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Dan Handley610e7e12018-03-01 18:44:00 +00001Trusted Firmware-A design
2=========================
Douglas Raillardd7c21b72017-06-28 15:23:03 +01003
4
5.. section-numbering::
6 :suffix: .
7
8.. contents::
9
Dan Handley610e7e12018-03-01 18:44:00 +000010Trusted Firmware-A (TF-A) implements a subset of the Trusted Board Boot
11Requirements (TBBR) Platform Design Document (PDD) [1]_ for Arm reference
Douglas Raillardd7c21b72017-06-28 15:23:03 +010012platforms. The TBB sequence starts when the platform is powered on and runs up
13to the stage where it hands-off control to firmware running in the normal
14world in DRAM. This is the cold boot path.
15
Dan Handley610e7e12018-03-01 18:44:00 +000016TF-A also implements the Power State Coordination Interface PDD [2]_ as a
17runtime service. PSCI is the interface from normal world software to firmware
18implementing power management use-cases (for example, secondary CPU boot,
19hotplug and idle). Normal world software can access TF-A runtime services via
20the Arm SMC (Secure Monitor Call) instruction. The SMC instruction must be
21used as mandated by the SMC Calling Convention [3]_.
Douglas Raillardd7c21b72017-06-28 15:23:03 +010022
Dan Handley610e7e12018-03-01 18:44:00 +000023TF-A implements a framework for configuring and managing interrupts generated
24in either security state. The details of the interrupt management framework
25and its design can be found in TF-A Interrupt Management Design guide [4]_.
Douglas Raillardd7c21b72017-06-28 15:23:03 +010026
Dan Handley610e7e12018-03-01 18:44:00 +000027TF-A also implements a library for setting up and managing the translation
28tables. The details of this library can be found in `Xlat_tables design`_.
Antonio Nino Diazb5d68092017-05-23 11:49:22 +010029
Dan Handley610e7e12018-03-01 18:44:00 +000030TF-A can be built to support either AArch64 or AArch32 execution state.
Douglas Raillardd7c21b72017-06-28 15:23:03 +010031
32Cold boot
33---------
34
35The cold boot path starts when the platform is physically turned on. If
36``COLD_BOOT_SINGLE_CPU=0``, one of the CPUs released from reset is chosen as the
37primary CPU, and the remaining CPUs are considered secondary CPUs. The primary
38CPU is chosen through platform-specific means. The cold boot path is mainly
39executed by the primary CPU, other than essential CPU initialization executed by
40all CPUs. The secondary CPUs are kept in a safe platform-specific state until
41the primary CPU has performed enough initialization to boot them.
42
43Refer to the `Reset Design`_ for more information on the effect of the
44``COLD_BOOT_SINGLE_CPU`` platform build option.
45
Dan Handley610e7e12018-03-01 18:44:00 +000046The cold boot path in this implementation of TF-A depends on the execution
47state. For AArch64, it is divided into five steps (in order of execution):
Douglas Raillardd7c21b72017-06-28 15:23:03 +010048
49- Boot Loader stage 1 (BL1) *AP Trusted ROM*
50- Boot Loader stage 2 (BL2) *Trusted Boot Firmware*
51- Boot Loader stage 3-1 (BL31) *EL3 Runtime Software*
52- Boot Loader stage 3-2 (BL32) *Secure-EL1 Payload* (optional)
53- Boot Loader stage 3-3 (BL33) *Non-trusted Firmware*
54
55For AArch32, it is divided into four steps (in order of execution):
56
57- Boot Loader stage 1 (BL1) *AP Trusted ROM*
58- Boot Loader stage 2 (BL2) *Trusted Boot Firmware*
59- Boot Loader stage 3-2 (BL32) *EL3 Runtime Software*
60- Boot Loader stage 3-3 (BL33) *Non-trusted Firmware*
61
Dan Handley610e7e12018-03-01 18:44:00 +000062Arm development platforms (Fixed Virtual Platforms (FVPs) and Juno) implement a
Douglas Raillardd7c21b72017-06-28 15:23:03 +010063combination of the following types of memory regions. Each bootloader stage uses
64one or more of these memory regions.
65
66- Regions accessible from both non-secure and secure states. For example,
67 non-trusted SRAM, ROM and DRAM.
68- Regions accessible from only the secure state. For example, trusted SRAM and
69 ROM. The FVPs also implement the trusted DRAM which is statically
70 configured. Additionally, the Base FVPs and Juno development platform
71 configure the TrustZone Controller (TZC) to create a region in the DRAM
72 which is accessible only from the secure state.
73
74The sections below provide the following details:
75
Soby Mathewb1bf0442018-02-16 14:52:52 +000076- dynamic configuration of Boot Loader stages
Douglas Raillardd7c21b72017-06-28 15:23:03 +010077- initialization and execution of the first three stages during cold boot
78- specification of the EL3 Runtime Software (BL31 for AArch64 and BL32 for
79 AArch32) entrypoint requirements for use by alternative Trusted Boot
80 Firmware in place of the provided BL1 and BL2
81
Soby Mathewb1bf0442018-02-16 14:52:52 +000082Dynamic Configuration during cold boot
83~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
84
85Each of the Boot Loader stages may be dynamically configured if required by the
86platform. The Boot Loader stage may optionally specify a firmware
87configuration file and/or hardware configuration file as listed below:
88
89- HW_CONFIG - The hardware configuration file. Can be shared by all Boot Loader
90 stages and also by the Normal World Rich OS.
91- TB_FW_CONFIG - Trusted Boot Firmware configuration file. Shared between BL1
92 and BL2.
93- SOC_FW_CONFIG - SoC Firmware configuration file. Used by BL31.
94- TOS_FW_CONFIG - Trusted OS Firmware configuration file. Used by Trusted OS
95 (BL32).
96- NT_FW_CONFIG - Non Trusted Firmware configuration file. Used by Non-trusted
97 firmware (BL33).
98
99The Arm development platforms use the Flattened Device Tree format for the
100dynamic configuration files.
101
102Each Boot Loader stage can pass up to 4 arguments via registers to the next
103stage. BL2 passes the list of the next images to execute to the *EL3 Runtime
104Software* (BL31 for AArch64 and BL32 for AArch32) via `arg0`. All the other
105arguments are platform defined. The Arm development platforms use the following
106convention:
107
108- BL1 passes the address of a meminfo_t structure to BL2 via ``arg1``. This
109 structure contains the memory layout available to BL2.
110- When dynamic configuration files are present, the firmware configuration for
111 the next Boot Loader stage is populated in the first available argument and
112 the generic hardware configuration is passed the next available argument.
113 For example,
114
115 - If TB_FW_CONFIG is loaded by BL1, then its address is passed in ``arg0``
116 to BL2.
117 - If HW_CONFIG is loaded by BL1, then its address is passed in ``arg2`` to
118 BL2. Note, ``arg1`` is already used for meminfo_t.
119 - If SOC_FW_CONFIG is loaded by BL2, then its address is passed in ``arg1``
120 to BL31. Note, ``arg0`` is used to pass the list of executable images.
121 - Similarly, if HW_CONFIG is loaded by BL1 or BL2, then its address is
122 passed in ``arg2`` to BL31.
123 - For other BL3x images, if the firmware configuration file is loaded by
124 BL2, then its address is passed in ``arg0`` and if HW_CONFIG is loaded
125 then its address is passed in ``arg1``.
126
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100127BL1
128~~~
129
130This stage begins execution from the platform's reset vector at EL3. The reset
131address is platform dependent but it is usually located in a Trusted ROM area.
132The BL1 data section is copied to trusted SRAM at runtime.
133
Dan Handley610e7e12018-03-01 18:44:00 +0000134On the Arm development platforms, BL1 code starts execution from the reset
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100135vector defined by the constant ``BL1_RO_BASE``. The BL1 data section is copied
136to the top of trusted SRAM as defined by the constant ``BL1_RW_BASE``.
137
138The functionality implemented by this stage is as follows.
139
140Determination of boot path
141^^^^^^^^^^^^^^^^^^^^^^^^^^
142
143Whenever a CPU is released from reset, BL1 needs to distinguish between a warm
144boot and a cold boot. This is done using platform-specific mechanisms (see the
145``plat_get_my_entrypoint()`` function in the `Porting Guide`_). In the case of a
146warm boot, a CPU is expected to continue execution from a separate
147entrypoint. In the case of a cold boot, the secondary CPUs are placed in a safe
148platform-specific state (see the ``plat_secondary_cold_boot_setup()`` function in
149the `Porting Guide`_) while the primary CPU executes the remaining cold boot path
150as described in the following sections.
151
152This step only applies when ``PROGRAMMABLE_RESET_ADDRESS=0``. Refer to the
153`Reset Design`_ for more information on the effect of the
154``PROGRAMMABLE_RESET_ADDRESS`` platform build option.
155
156Architectural initialization
157^^^^^^^^^^^^^^^^^^^^^^^^^^^^
158
159BL1 performs minimal architectural initialization as follows.
160
161- Exception vectors
162
163 BL1 sets up simple exception vectors for both synchronous and asynchronous
164 exceptions. The default behavior upon receiving an exception is to populate
165 a status code in the general purpose register ``X0/R0`` and call the
166 ``plat_report_exception()`` function (see the `Porting Guide`_). The status
167 code is one of:
168
169 For AArch64:
170
171 ::
172
173 0x0 : Synchronous exception from Current EL with SP_EL0
174 0x1 : IRQ exception from Current EL with SP_EL0
175 0x2 : FIQ exception from Current EL with SP_EL0
176 0x3 : System Error exception from Current EL with SP_EL0
177 0x4 : Synchronous exception from Current EL with SP_ELx
178 0x5 : IRQ exception from Current EL with SP_ELx
179 0x6 : FIQ exception from Current EL with SP_ELx
180 0x7 : System Error exception from Current EL with SP_ELx
181 0x8 : Synchronous exception from Lower EL using aarch64
182 0x9 : IRQ exception from Lower EL using aarch64
183 0xa : FIQ exception from Lower EL using aarch64
184 0xb : System Error exception from Lower EL using aarch64
185 0xc : Synchronous exception from Lower EL using aarch32
186 0xd : IRQ exception from Lower EL using aarch32
187 0xe : FIQ exception from Lower EL using aarch32
188 0xf : System Error exception from Lower EL using aarch32
189
190 For AArch32:
191
192 ::
193
194 0x10 : User mode
195 0x11 : FIQ mode
196 0x12 : IRQ mode
197 0x13 : SVC mode
198 0x16 : Monitor mode
199 0x17 : Abort mode
200 0x1a : Hypervisor mode
201 0x1b : Undefined mode
202 0x1f : System mode
203
Dan Handley610e7e12018-03-01 18:44:00 +0000204 The ``plat_report_exception()`` implementation on the Arm FVP port programs
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100205 the Versatile Express System LED register in the following format to
Paul Beesley1fbc97b2019-01-11 18:26:51 +0000206 indicate the occurrence of an unexpected exception:
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100207
208 ::
209
210 SYS_LED[0] - Security state (Secure=0/Non-Secure=1)
211 SYS_LED[2:1] - Exception Level (EL3=0x3, EL2=0x2, EL1=0x1, EL0=0x0)
212 For AArch32 it is always 0x0
213 SYS_LED[7:3] - Exception Class (Sync/Async & origin). This is the value
214 of the status code
215
216 A write to the LED register reflects in the System LEDs (S6LED0..7) in the
217 CLCD window of the FVP.
218
219 BL1 does not expect to receive any exceptions other than the SMC exception.
220 For the latter, BL1 installs a simple stub. The stub expects to receive a
221 limited set of SMC types (determined by their function IDs in the general
222 purpose register ``X0/R0``):
223
224 - ``BL1_SMC_RUN_IMAGE``: This SMC is raised by BL2 to make BL1 pass control
225 to EL3 Runtime Software.
226 - All SMCs listed in section "BL1 SMC Interface" in the `Firmware Update`_
227 Design Guide are supported for AArch64 only. These SMCs are currently
228 not supported when BL1 is built for AArch32.
229
230 Any other SMC leads to an assertion failure.
231
232- CPU initialization
233
234 BL1 calls the ``reset_handler()`` function which in turn calls the CPU
235 specific reset handler function (see the section: "CPU specific operations
236 framework").
237
238- Control register setup (for AArch64)
239
240 - ``SCTLR_EL3``. Instruction cache is enabled by setting the ``SCTLR_EL3.I``
241 bit. Alignment and stack alignment checking is enabled by setting the
242 ``SCTLR_EL3.A`` and ``SCTLR_EL3.SA`` bits. Exception endianness is set to
243 little-endian by clearing the ``SCTLR_EL3.EE`` bit.
244
245 - ``SCR_EL3``. The register width of the next lower exception level is set
246 to AArch64 by setting the ``SCR.RW`` bit. The ``SCR.EA`` bit is set to trap
247 both External Aborts and SError Interrupts in EL3. The ``SCR.SIF`` bit is
248 also set to disable instruction fetches from Non-secure memory when in
249 secure state.
250
251 - ``CPTR_EL3``. Accesses to the ``CPACR_EL1`` register from EL1 or EL2, or the
252 ``CPTR_EL2`` register from EL2 are configured to not trap to EL3 by
253 clearing the ``CPTR_EL3.TCPAC`` bit. Access to the trace functionality is
254 configured not to trap to EL3 by clearing the ``CPTR_EL3.TTA`` bit.
255 Instructions that access the registers associated with Floating Point
256 and Advanced SIMD execution are configured to not trap to EL3 by
257 clearing the ``CPTR_EL3.TFP`` bit.
258
259 - ``DAIF``. The SError interrupt is enabled by clearing the SError interrupt
260 mask bit.
261
262 - ``MDCR_EL3``. The trap controls, ``MDCR_EL3.TDOSA``, ``MDCR_EL3.TDA`` and
263 ``MDCR_EL3.TPM``, are set so that accesses to the registers they control
264 do not trap to EL3. AArch64 Secure self-hosted debug is disabled by
265 setting the ``MDCR_EL3.SDD`` bit. Also ``MDCR_EL3.SPD32`` is set to
266 disable AArch32 Secure self-hosted privileged debug from S-EL1.
267
268- Control register setup (for AArch32)
269
270 - ``SCTLR``. Instruction cache is enabled by setting the ``SCTLR.I`` bit.
271 Alignment checking is enabled by setting the ``SCTLR.A`` bit.
272 Exception endianness is set to little-endian by clearing the
273 ``SCTLR.EE`` bit.
274
275 - ``SCR``. The ``SCR.SIF`` bit is set to disable instruction fetches from
276 Non-secure memory when in secure state.
277
278 - ``CPACR``. Allow execution of Advanced SIMD instructions at PL0 and PL1,
279 by clearing the ``CPACR.ASEDIS`` bit. Access to the trace functionality
280 is configured not to trap to undefined mode by clearing the
281 ``CPACR.TRCDIS`` bit.
282
283 - ``NSACR``. Enable non-secure access to Advanced SIMD functionality and
284 system register access to implemented trace registers.
285
286 - ``FPEXC``. Enable access to the Advanced SIMD and floating-point
287 functionality from all Exception levels.
288
289 - ``CPSR.A``. The Asynchronous data abort interrupt is enabled by clearing
290 the Asynchronous data abort interrupt mask bit.
291
292 - ``SDCR``. The ``SDCR.SPD`` field is set to disable AArch32 Secure
293 self-hosted privileged debug.
294
295Platform initialization
296^^^^^^^^^^^^^^^^^^^^^^^
297
Dan Handley610e7e12018-03-01 18:44:00 +0000298On Arm platforms, BL1 performs the following platform initializations:
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100299
300- Enable the Trusted Watchdog.
301- Initialize the console.
302- Configure the Interconnect to enable hardware coherency.
303- Enable the MMU and map the memory it needs to access.
304- Configure any required platform storage to load the next bootloader image
305 (BL2).
Soby Mathewb1bf0442018-02-16 14:52:52 +0000306- If the BL1 dynamic configuration file, ``TB_FW_CONFIG``, is available, then
307 load it to the platform defined address and make it available to BL2 via
308 ``arg0``.
Soby Mathewd969a7e2018-06-11 16:40:36 +0100309- Configure the system timer and program the `CNTFRQ_EL0` for use by NS-BL1U
310 and NS-BL2U firmware update images.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100311
312Firmware Update detection and execution
313^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
314
315After performing platform setup, BL1 common code calls
316``bl1_plat_get_next_image_id()`` to determine if `Firmware Update`_ is required or
317to proceed with the normal boot process. If the platform code returns
318``BL2_IMAGE_ID`` then the normal boot sequence is executed as described in the
319next section, else BL1 assumes that `Firmware Update`_ is required and execution
320passes to the first image in the `Firmware Update`_ process. In either case, BL1
321retrieves a descriptor of the next image by calling ``bl1_plat_get_image_desc()``.
322The image descriptor contains an ``entry_point_info_t`` structure, which BL1
323uses to initialize the execution state of the next image.
324
325BL2 image load and execution
326^^^^^^^^^^^^^^^^^^^^^^^^^^^^
327
328In the normal boot flow, BL1 execution continues as follows:
329
330#. BL1 prints the following string from the primary CPU to indicate successful
331 execution of the BL1 stage:
332
333 ::
334
335 "Booting Trusted Firmware"
336
Soby Mathewb1bf0442018-02-16 14:52:52 +0000337#. BL1 loads a BL2 raw binary image from platform storage, at a
338 platform-specific base address. Prior to the load, BL1 invokes
339 ``bl1_plat_handle_pre_image_load()`` which allows the platform to update or
340 use the image information. If the BL2 image file is not present or if
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100341 there is not enough free trusted SRAM the following error message is
342 printed:
343
344 ::
345
346 "Failed to load BL2 firmware."
347
Soby Mathewb1bf0442018-02-16 14:52:52 +0000348#. BL1 invokes ``bl1_plat_handle_post_image_load()`` which again is intended
349 for platforms to take further action after image load. This function must
350 populate the necessary arguments for BL2, which may also include the memory
351 layout. Further description of the memory layout can be found later
352 in this document.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100353
354#. BL1 passes control to the BL2 image at Secure EL1 (for AArch64) or at
355 Secure SVC mode (for AArch32), starting from its load address.
356
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100357BL2
358~~~
359
360BL1 loads and passes control to BL2 at Secure-EL1 (for AArch64) or at Secure
361SVC mode (for AArch32) . BL2 is linked against and loaded at a platform-specific
362base address (more information can be found later in this document).
363The functionality implemented by BL2 is as follows.
364
365Architectural initialization
366^^^^^^^^^^^^^^^^^^^^^^^^^^^^
367
368For AArch64, BL2 performs the minimal architectural initialization required
Dan Handley610e7e12018-03-01 18:44:00 +0000369for subsequent stages of TF-A and normal world software. EL1 and EL0 are given
370access to Floating Point and Advanced SIMD registers by clearing the
371``CPACR.FPEN`` bits.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100372
373For AArch32, the minimal architectural initialization required for subsequent
Dan Handley610e7e12018-03-01 18:44:00 +0000374stages of TF-A and normal world software is taken care of in BL1 as both BL1
375and BL2 execute at PL1.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100376
377Platform initialization
378^^^^^^^^^^^^^^^^^^^^^^^
379
Dan Handley610e7e12018-03-01 18:44:00 +0000380On Arm platforms, BL2 performs the following platform initializations:
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100381
382- Initialize the console.
383- Configure any required platform storage to allow loading further bootloader
384 images.
385- Enable the MMU and map the memory it needs to access.
386- Perform platform security setup to allow access to controlled components.
387- Reserve some memory for passing information to the next bootloader image
388 EL3 Runtime Software and populate it.
389- Define the extents of memory available for loading each subsequent
390 bootloader image.
Soby Mathewb1bf0442018-02-16 14:52:52 +0000391- If BL1 has passed TB_FW_CONFIG dynamic configuration file in ``arg0``,
392 then parse it.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100393
394Image loading in BL2
395^^^^^^^^^^^^^^^^^^^^
396
Roberto Vargas025946a2018-09-24 17:20:48 +0100397BL2 generic code loads the images based on the list of loadable images
398provided by the platform. BL2 passes the list of executable images
399provided by the platform to the next handover BL image.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100400
Soby Mathewb1bf0442018-02-16 14:52:52 +0000401The list of loadable images provided by the platform may also contain
402dynamic configuration files. The files are loaded and can be parsed as
403needed in the ``bl2_plat_handle_post_image_load()`` function. These
404configuration files can be passed to next Boot Loader stages as arguments
405by updating the corresponding entrypoint information in this function.
406
Sandrine Bailleux15530dd2019-02-08 15:26:36 +0100407SCP_BL2 (System Control Processor Firmware) image load
408^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100409
410Some systems have a separate System Control Processor (SCP) for power, clock,
Sandrine Bailleux15530dd2019-02-08 15:26:36 +0100411reset and system control. BL2 loads the optional SCP_BL2 image from platform
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100412storage into a platform-specific region of secure memory. The subsequent
Sandrine Bailleux15530dd2019-02-08 15:26:36 +0100413handling of SCP_BL2 is platform specific. For example, on the Juno Arm
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100414development platform port the image is transferred into SCP's internal memory
415using the Boot Over MHU (BOM) protocol after being loaded in the trusted SRAM
Sandrine Bailleux15530dd2019-02-08 15:26:36 +0100416memory. The SCP executes SCP_BL2 and signals to the Application Processor (AP)
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100417for BL2 execution to continue.
418
419EL3 Runtime Software image load
420^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
421
422BL2 loads the EL3 Runtime Software image from platform storage into a platform-
423specific address in trusted SRAM. If there is not enough memory to load the
Roberto Vargas025946a2018-09-24 17:20:48 +0100424image or image is missing it leads to an assertion failure.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100425
426AArch64 BL32 (Secure-EL1 Payload) image load
427^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
428
429BL2 loads the optional BL32 image from platform storage into a platform-
430specific region of secure memory. The image executes in the secure world. BL2
431relies on BL31 to pass control to the BL32 image, if present. Hence, BL2
432populates a platform-specific area of memory with the entrypoint/load-address
433of the BL32 image. The value of the Saved Processor Status Register (``SPSR``)
434for entry into BL32 is not determined by BL2, it is initialized by the
435Secure-EL1 Payload Dispatcher (see later) within BL31, which is responsible for
436managing interaction with BL32. This information is passed to BL31.
437
438BL33 (Non-trusted Firmware) image load
439^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
440
441BL2 loads the BL33 image (e.g. UEFI or other test or boot software) from
442platform storage into non-secure memory as defined by the platform.
443
444BL2 relies on EL3 Runtime Software to pass control to BL33 once secure state
445initialization is complete. Hence, BL2 populates a platform-specific area of
446memory with the entrypoint and Saved Program Status Register (``SPSR``) of the
447normal world software image. The entrypoint is the load address of the BL33
448image. The ``SPSR`` is determined as specified in Section 5.13 of the
449`PSCI PDD`_. This information is passed to the EL3 Runtime Software.
450
451AArch64 BL31 (EL3 Runtime Software) execution
452^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
453
454BL2 execution continues as follows:
455
456#. BL2 passes control back to BL1 by raising an SMC, providing BL1 with the
457 BL31 entrypoint. The exception is handled by the SMC exception handler
458 installed by BL1.
459
460#. BL1 turns off the MMU and flushes the caches. It clears the
461 ``SCTLR_EL3.M/I/C`` bits, flushes the data cache to the point of coherency
462 and invalidates the TLBs.
463
464#. BL1 passes control to BL31 at the specified entrypoint at EL3.
465
Roberto Vargasb1584272017-11-20 13:36:10 +0000466Running BL2 at EL3 execution level
467~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
468
Dan Handley610e7e12018-03-01 18:44:00 +0000469Some platforms have a non-TF-A Boot ROM that expects the next boot stage
470to execute at EL3. On these platforms, TF-A BL1 is a waste of memory
471as its only purpose is to ensure TF-A BL2 is entered at S-EL1. To avoid
Roberto Vargasb1584272017-11-20 13:36:10 +0000472this waste, a special mode enables BL2 to execute at EL3, which allows
Dan Handley610e7e12018-03-01 18:44:00 +0000473a non-TF-A Boot ROM to load and jump directly to BL2. This mode is selected
Roberto Vargasb1584272017-11-20 13:36:10 +0000474when the build flag BL2_AT_EL3 is enabled. The main differences in this
475mode are:
476
477#. BL2 includes the reset code and the mailbox mechanism to differentiate
478 cold boot and warm boot. It runs at EL3 doing the arch
479 initialization required for EL3.
480
481#. BL2 does not receive the meminfo information from BL1 anymore. This
482 information can be passed by the Boot ROM or be internal to the
483 BL2 image.
484
485#. Since BL2 executes at EL3, BL2 jumps directly to the next image,
486 instead of invoking the RUN_IMAGE SMC call.
487
488
489We assume 3 different types of BootROM support on the platform:
490
491#. The Boot ROM always jumps to the same address, for both cold
492 and warm boot. In this case, we will need to keep a resident part
493 of BL2 whose memory cannot be reclaimed by any other image. The
494 linker script defines the symbols __TEXT_RESIDENT_START__ and
495 __TEXT_RESIDENT_END__ that allows the platform to configure
496 correctly the memory map.
497#. The platform has some mechanism to indicate the jump address to the
498 Boot ROM. Platform code can then program the jump address with
499 psci_warmboot_entrypoint during cold boot.
500#. The platform has some mechanism to program the reset address using
501 the PROGRAMMABLE_RESET_ADDRESS feature. Platform code can then
502 program the reset address with psci_warmboot_entrypoint during
503 cold boot, bypassing the boot ROM for warm boot.
504
505In the last 2 cases, no part of BL2 needs to remain resident at
506runtime. In the first 2 cases, we expect the Boot ROM to be able to
507differentiate between warm and cold boot, to avoid loading BL2 again
508during warm boot.
509
510This functionality can be tested with FVP loading the image directly
511in memory and changing the address where the system jumps at reset.
512For example:
513
Dimitris Papastamos25836492018-06-11 11:07:58 +0100514 -C cluster0.cpu0.RVBAR=0x4022000
515 --data cluster0.cpu0=bl2.bin@0x4022000
Roberto Vargasb1584272017-11-20 13:36:10 +0000516
517With this configuration, FVP is like a platform of the first case,
518where the Boot ROM jumps always to the same address. For simplification,
519BL32 is loaded in DRAM in this case, to avoid other images reclaiming
520BL2 memory.
521
522
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100523AArch64 BL31
524~~~~~~~~~~~~
525
526The image for this stage is loaded by BL2 and BL1 passes control to BL31 at
527EL3. BL31 executes solely in trusted SRAM. BL31 is linked against and
528loaded at a platform-specific base address (more information can be found later
529in this document). The functionality implemented by BL31 is as follows.
530
531Architectural initialization
532^^^^^^^^^^^^^^^^^^^^^^^^^^^^
533
534Currently, BL31 performs a similar architectural initialization to BL1 as
535far as system register settings are concerned. Since BL1 code resides in ROM,
536architectural initialization in BL31 allows override of any previous
537initialization done by BL1.
538
539BL31 initializes the per-CPU data framework, which provides a cache of
540frequently accessed per-CPU data optimised for fast, concurrent manipulation
541on different CPUs. This buffer includes pointers to per-CPU contexts, crash
542buffer, CPU reset and power down operations, PSCI data, platform data and so on.
543
544It then replaces the exception vectors populated by BL1 with its own. BL31
545exception vectors implement more elaborate support for handling SMCs since this
546is the only mechanism to access the runtime services implemented by BL31 (PSCI
547for example). BL31 checks each SMC for validity as specified by the
548`SMC calling convention PDD`_ before passing control to the required SMC
549handler routine.
550
551BL31 programs the ``CNTFRQ_EL0`` register with the clock frequency of the system
552counter, which is provided by the platform.
553
554Platform initialization
555^^^^^^^^^^^^^^^^^^^^^^^
556
557BL31 performs detailed platform initialization, which enables normal world
558software to function correctly.
559
Dan Handley610e7e12018-03-01 18:44:00 +0000560On Arm platforms, this consists of the following:
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100561
562- Initialize the console.
563- Configure the Interconnect to enable hardware coherency.
564- Enable the MMU and map the memory it needs to access.
565- Initialize the generic interrupt controller.
566- Initialize the power controller device.
567- Detect the system topology.
568
569Runtime services initialization
570^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
571
572BL31 is responsible for initializing the runtime services. One of them is PSCI.
573
574As part of the PSCI initializations, BL31 detects the system topology. It also
575initializes the data structures that implement the state machine used to track
576the state of power domain nodes. The state can be one of ``OFF``, ``RUN`` or
577``RETENTION``. All secondary CPUs are initially in the ``OFF`` state. The cluster
578that the primary CPU belongs to is ``ON``; any other cluster is ``OFF``. It also
579initializes the locks that protect them. BL31 accesses the state of a CPU or
580cluster immediately after reset and before the data cache is enabled in the
581warm boot path. It is not currently possible to use 'exclusive' based spinlocks,
582therefore BL31 uses locks based on Lamport's Bakery algorithm instead.
583
584The runtime service framework and its initialization is described in more
585detail in the "EL3 runtime services framework" section below.
586
587Details about the status of the PSCI implementation are provided in the
588"Power State Coordination Interface" section below.
589
590AArch64 BL32 (Secure-EL1 Payload) image initialization
591^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
592
593If a BL32 image is present then there must be a matching Secure-EL1 Payload
594Dispatcher (SPD) service (see later for details). During initialization
595that service must register a function to carry out initialization of BL32
596once the runtime services are fully initialized. BL31 invokes such a
597registered function to initialize BL32 before running BL33. This initialization
598is not necessary for AArch32 SPs.
599
600Details on BL32 initialization and the SPD's role are described in the
601"Secure-EL1 Payloads and Dispatchers" section below.
602
603BL33 (Non-trusted Firmware) execution
604^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
605
606EL3 Runtime Software initializes the EL2 or EL1 processor context for normal-
607world cold boot, ensuring that no secure state information finds its way into
608the non-secure execution state. EL3 Runtime Software uses the entrypoint
609information provided by BL2 to jump to the Non-trusted firmware image (BL33)
610at the highest available Exception Level (EL2 if available, otherwise EL1).
611
612Using alternative Trusted Boot Firmware in place of BL1 & BL2 (AArch64 only)
613~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
614
615Some platforms have existing implementations of Trusted Boot Firmware that
Dan Handley610e7e12018-03-01 18:44:00 +0000616would like to use TF-A BL31 for the EL3 Runtime Software. To enable this
617firmware architecture it is important to provide a fully documented and stable
618interface between the Trusted Boot Firmware and BL31.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100619
620Future changes to the BL31 interface will be done in a backwards compatible
621way, and this enables these firmware components to be independently enhanced/
622updated to develop and exploit new functionality.
623
624Required CPU state when calling ``bl31_entrypoint()`` during cold boot
625^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
626
627This function must only be called by the primary CPU.
628
629On entry to this function the calling primary CPU must be executing in AArch64
630EL3, little-endian data access, and all interrupt sources masked:
631
632::
633
634 PSTATE.EL = 3
635 PSTATE.RW = 1
636 PSTATE.DAIF = 0xf
637 SCTLR_EL3.EE = 0
638
639X0 and X1 can be used to pass information from the Trusted Boot Firmware to the
640platform code in BL31:
641
642::
643
Dan Handley610e7e12018-03-01 18:44:00 +0000644 X0 : Reserved for common TF-A information
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100645 X1 : Platform specific information
646
647BL31 zero-init sections (e.g. ``.bss``) should not contain valid data on entry,
648these will be zero filled prior to invoking platform setup code.
649
650Use of the X0 and X1 parameters
651'''''''''''''''''''''''''''''''
652
653The parameters are platform specific and passed from ``bl31_entrypoint()`` to
654``bl31_early_platform_setup()``. The value of these parameters is never directly
655used by the common BL31 code.
656
657The convention is that ``X0`` conveys information regarding the BL31, BL32 and
658BL33 images from the Trusted Boot firmware and ``X1`` can be used for other
Dan Handley610e7e12018-03-01 18:44:00 +0000659platform specific purpose. This convention allows platforms which use TF-A's
660BL1 and BL2 images to transfer additional platform specific information from
661Secure Boot without conflicting with future evolution of TF-A using ``X0`` to
662pass a ``bl31_params`` structure.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100663
664BL31 common and SPD initialization code depends on image and entrypoint
665information about BL33 and BL32, which is provided via BL31 platform APIs.
666This information is required until the start of execution of BL33. This
667information can be provided in a platform defined manner, e.g. compiled into
668the platform code in BL31, or provided in a platform defined memory location
669by the Trusted Boot firmware, or passed from the Trusted Boot Firmware via the
670Cold boot Initialization parameters. This data may need to be cleaned out of
671the CPU caches if it is provided by an earlier boot stage and then accessed by
672BL31 platform code before the caches are enabled.
673
Dan Handley610e7e12018-03-01 18:44:00 +0000674TF-A's BL2 implementation passes a ``bl31_params`` structure in
675``X0`` and the Arm development platforms interpret this in the BL31 platform
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100676code.
677
678MMU, Data caches & Coherency
679''''''''''''''''''''''''''''
680
681BL31 does not depend on the enabled state of the MMU, data caches or
682interconnect coherency on entry to ``bl31_entrypoint()``. If these are disabled
683on entry, these should be enabled during ``bl31_plat_arch_setup()``.
684
685Data structures used in the BL31 cold boot interface
686''''''''''''''''''''''''''''''''''''''''''''''''''''
687
688These structures are designed to support compatibility and independent
689evolution of the structures and the firmware images. For example, a version of
690BL31 that can interpret the BL3x image information from different versions of
Sandrine Bailleux15530dd2019-02-08 15:26:36 +0100691BL2, a platform that uses an extended entry_point_info structure to convey
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100692additional register information to BL31, or a ELF image loader that can convey
693more details about the firmware images.
694
695To support these scenarios the structures are versioned and sized, which enables
696BL31 to detect which information is present and respond appropriately. The
697``param_header`` is defined to capture this information:
698
699.. code:: c
700
701 typedef struct param_header {
702 uint8_t type; /* type of the structure */
703 uint8_t version; /* version of this structure */
704 uint16_t size; /* size of this structure in bytes */
705 uint32_t attr; /* attributes: unused bits SBZ */
706 } param_header_t;
707
708The structures using this format are ``entry_point_info``, ``image_info`` and
709``bl31_params``. The code that allocates and populates these structures must set
710the header fields appropriately, and the ``SET_PARAM_HEAD()`` a macro is defined
711to simplify this action.
712
713Required CPU state for BL31 Warm boot initialization
714^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
715
Dan Handley610e7e12018-03-01 18:44:00 +0000716When requesting a CPU power-on, or suspending a running CPU, TF-A provides
717the platform power management code with a Warm boot initialization
718entry-point, to be invoked by the CPU immediately after the reset handler.
719On entry to the Warm boot initialization function the calling CPU must be in
720AArch64 EL3, little-endian data access and all interrupt sources masked:
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100721
722::
723
724 PSTATE.EL = 3
725 PSTATE.RW = 1
726 PSTATE.DAIF = 0xf
727 SCTLR_EL3.EE = 0
728
729The PSCI implementation will initialize the processor state and ensure that the
730platform power management code is then invoked as required to initialize all
731necessary system, cluster and CPU resources.
732
733AArch32 EL3 Runtime Software entrypoint interface
734~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
735
736To enable this firmware architecture it is important to provide a fully
737documented and stable interface between the Trusted Boot Firmware and the
738AArch32 EL3 Runtime Software.
739
740Future changes to the entrypoint interface will be done in a backwards
741compatible way, and this enables these firmware components to be independently
742enhanced/updated to develop and exploit new functionality.
743
744Required CPU state when entering during cold boot
745^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
746
747This function must only be called by the primary CPU.
748
749On entry to this function the calling primary CPU must be executing in AArch32
750EL3, little-endian data access, and all interrupt sources masked:
751
752::
753
754 PSTATE.AIF = 0x7
755 SCTLR.EE = 0
756
757R0 and R1 are used to pass information from the Trusted Boot Firmware to the
758platform code in AArch32 EL3 Runtime Software:
759
760::
761
Dan Handley610e7e12018-03-01 18:44:00 +0000762 R0 : Reserved for common TF-A information
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100763 R1 : Platform specific information
764
765Use of the R0 and R1 parameters
766'''''''''''''''''''''''''''''''
767
768The parameters are platform specific and the convention is that ``R0`` conveys
769information regarding the BL3x images from the Trusted Boot firmware and ``R1``
770can be used for other platform specific purpose. This convention allows
Dan Handley610e7e12018-03-01 18:44:00 +0000771platforms which use TF-A's BL1 and BL2 images to transfer additional platform
772specific information from Secure Boot without conflicting with future
773evolution of TF-A using ``R0`` to pass a ``bl_params`` structure.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100774
775The AArch32 EL3 Runtime Software is responsible for entry into BL33. This
776information can be obtained in a platform defined manner, e.g. compiled into
777the AArch32 EL3 Runtime Software, or provided in a platform defined memory
778location by the Trusted Boot firmware, or passed from the Trusted Boot Firmware
779via the Cold boot Initialization parameters. This data may need to be cleaned
780out of the CPU caches if it is provided by an earlier boot stage and then
781accessed by AArch32 EL3 Runtime Software before the caches are enabled.
782
Dan Handley610e7e12018-03-01 18:44:00 +0000783When using AArch32 EL3 Runtime Software, the Arm development platforms pass a
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100784``bl_params`` structure in ``R0`` from BL2 to be interpreted by AArch32 EL3 Runtime
785Software platform code.
786
787MMU, Data caches & Coherency
788''''''''''''''''''''''''''''
789
790AArch32 EL3 Runtime Software must not depend on the enabled state of the MMU,
791data caches or interconnect coherency in its entrypoint. They must be explicitly
792enabled if required.
793
794Data structures used in cold boot interface
795'''''''''''''''''''''''''''''''''''''''''''
796
797The AArch32 EL3 Runtime Software cold boot interface uses ``bl_params`` instead
798of ``bl31_params``. The ``bl_params`` structure is based on the convention
799described in AArch64 BL31 cold boot interface section.
800
801Required CPU state for warm boot initialization
802^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
803
804When requesting a CPU power-on, or suspending a running CPU, AArch32 EL3
805Runtime Software must ensure execution of a warm boot initialization entrypoint.
Sandrine Bailleux15530dd2019-02-08 15:26:36 +0100806If TF-A BL1 is used and the PROGRAMMABLE_RESET_ADDRESS build flag is false,
Dan Handley610e7e12018-03-01 18:44:00 +0000807then AArch32 EL3 Runtime Software must ensure that BL1 branches to the warm
808boot entrypoint by arranging for the BL1 platform function,
Sandrine Bailleux15530dd2019-02-08 15:26:36 +0100809plat_get_my_entrypoint(), to return a non-zero value.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100810
811In this case, the warm boot entrypoint must be in AArch32 EL3, little-endian
812data access and all interrupt sources masked:
813
814::
815
816 PSTATE.AIF = 0x7
817 SCTLR.EE = 0
818
Dan Handley610e7e12018-03-01 18:44:00 +0000819The warm boot entrypoint may be implemented by using TF-A
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100820``psci_warmboot_entrypoint()`` function. In that case, the platform must fulfil
821the pre-requisites mentioned in the `PSCI Library integration guide`_.
822
823EL3 runtime services framework
824------------------------------
825
826Software executing in the non-secure state and in the secure state at exception
827levels lower than EL3 will request runtime services using the Secure Monitor
828Call (SMC) instruction. These requests will follow the convention described in
829the SMC Calling Convention PDD (`SMCCC`_). The `SMCCC`_ assigns function
830identifiers to each SMC request and describes how arguments are passed and
831returned.
832
833The EL3 runtime services framework enables the development of services by
834different providers that can be easily integrated into final product firmware.
835The following sections describe the framework which facilitates the
836registration, initialization and use of runtime services in EL3 Runtime
837Software (BL31).
838
839The design of the runtime services depends heavily on the concepts and
840definitions described in the `SMCCC`_, in particular SMC Function IDs, Owning
841Entity Numbers (OEN), Fast and Yielding calls, and the SMC32 and SMC64 calling
842conventions. Please refer to that document for more detailed explanation of
843these terms.
844
845The following runtime services are expected to be implemented first. They have
846not all been instantiated in the current implementation.
847
848#. Standard service calls
849
850 This service is for management of the entire system. The Power State
851 Coordination Interface (`PSCI`_) is the first set of standard service calls
Dan Handley610e7e12018-03-01 18:44:00 +0000852 defined by Arm (see PSCI section later).
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100853
854#. Secure-EL1 Payload Dispatcher service
855
856 If a system runs a Trusted OS or other Secure-EL1 Payload (SP) then
857 it also requires a *Secure Monitor* at EL3 to switch the EL1 processor
858 context between the normal world (EL1/EL2) and trusted world (Secure-EL1).
859 The Secure Monitor will make these world switches in response to SMCs. The
860 `SMCCC`_ provides for such SMCs with the Trusted OS Call and Trusted
861 Application Call OEN ranges.
862
863 The interface between the EL3 Runtime Software and the Secure-EL1 Payload is
864 not defined by the `SMCCC`_ or any other standard. As a result, each
865 Secure-EL1 Payload requires a specific Secure Monitor that runs as a runtime
Dan Handley610e7e12018-03-01 18:44:00 +0000866 service - within TF-A this service is referred to as the Secure-EL1 Payload
867 Dispatcher (SPD).
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100868
Dan Handley610e7e12018-03-01 18:44:00 +0000869 TF-A provides a Test Secure-EL1 Payload (TSP) and its associated Dispatcher
870 (TSPD). Details of SPD design and TSP/TSPD operation are described in the
871 "Secure-EL1 Payloads and Dispatchers" section below.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100872
873#. CPU implementation service
874
875 This service will provide an interface to CPU implementation specific
876 services for a given platform e.g. access to processor errata workarounds.
877 This service is currently unimplemented.
878
Dan Handley610e7e12018-03-01 18:44:00 +0000879Additional services for Arm Architecture, SiP and OEM calls can be implemented.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100880Each implemented service handles a range of SMC function identifiers as
881described in the `SMCCC`_.
882
883Registration
884~~~~~~~~~~~~
885
886A runtime service is registered using the ``DECLARE_RT_SVC()`` macro, specifying
887the name of the service, the range of OENs covered, the type of service and
888initialization and call handler functions. This macro instantiates a ``const struct rt_svc_desc`` for the service with these details (see ``runtime_svc.h``).
889This structure is allocated in a special ELF section ``rt_svc_descs``, enabling
890the framework to find all service descriptors included into BL31.
891
892The specific service for a SMC Function is selected based on the OEN and call
893type of the Function ID, and the framework uses that information in the service
894descriptor to identify the handler for the SMC Call.
895
896The service descriptors do not include information to identify the precise set
897of SMC function identifiers supported by this service implementation, the
898security state from which such calls are valid nor the capability to support
89964-bit and/or 32-bit callers (using SMC32 or SMC64). Responding appropriately
900to these aspects of a SMC call is the responsibility of the service
901implementation, the framework is focused on integration of services from
902different providers and minimizing the time taken by the framework before the
903service handler is invoked.
904
905Details of the parameters, requirements and behavior of the initialization and
906call handling functions are provided in the following sections.
907
908Initialization
909~~~~~~~~~~~~~~
910
911``runtime_svc_init()`` in ``runtime_svc.c`` initializes the runtime services
912framework running on the primary CPU during cold boot as part of the BL31
913initialization. This happens prior to initializing a Trusted OS and running
914Normal world boot firmware that might in turn use these services.
915Initialization involves validating each of the declared runtime service
916descriptors, calling the service initialization function and populating the
917index used for runtime lookup of the service.
918
919The BL31 linker script collects all of the declared service descriptors into a
920single array and defines symbols that allow the framework to locate and traverse
921the array, and determine its size.
922
923The framework does basic validation of each descriptor to halt firmware
924initialization if service declaration errors are detected. The framework does
925not check descriptors for the following error conditions, and may behave in an
926unpredictable manner under such scenarios:
927
928#. Overlapping OEN ranges
929#. Multiple descriptors for the same range of OENs and ``call_type``
930#. Incorrect range of owning entity numbers for a given ``call_type``
931
932Once validated, the service ``init()`` callback is invoked. This function carries
933out any essential EL3 initialization before servicing requests. The ``init()``
934function is only invoked on the primary CPU during cold boot. If the service
935uses per-CPU data this must either be initialized for all CPUs during this call,
936or be done lazily when a CPU first issues an SMC call to that service. If
937``init()`` returns anything other than ``0``, this is treated as an initialization
938error and the service is ignored: this does not cause the firmware to halt.
939
940The OEN and call type fields present in the SMC Function ID cover a total of
941128 distinct services, but in practice a single descriptor can cover a range of
942OENs, e.g. SMCs to call a Trusted OS function. To optimize the lookup of a
943service handler, the framework uses an array of 128 indices that map every
944distinct OEN/call-type combination either to one of the declared services or to
945indicate the service is not handled. This ``rt_svc_descs_indices[]`` array is
946populated for all of the OENs covered by a service after the service ``init()``
947function has reported success. So a service that fails to initialize will never
948have it's ``handle()`` function invoked.
949
950The following figure shows how the ``rt_svc_descs_indices[]`` index maps the SMC
951Function ID call type and OEN onto a specific service handler in the
952``rt_svc_descs[]`` array.
953
954|Image 1|
955
956Handling an SMC
957~~~~~~~~~~~~~~~
958
959When the EL3 runtime services framework receives a Secure Monitor Call, the SMC
960Function ID is passed in W0 from the lower exception level (as per the
961`SMCCC`_). If the calling register width is AArch32, it is invalid to invoke an
962SMC Function which indicates the SMC64 calling convention: such calls are
963ignored and return the Unknown SMC Function Identifier result code ``0xFFFFFFFF``
964in R0/X0.
965
966Bit[31] (fast/yielding call) and bits[29:24] (owning entity number) of the SMC
967Function ID are combined to index into the ``rt_svc_descs_indices[]`` array. The
968resulting value might indicate a service that has no handler, in this case the
969framework will also report an Unknown SMC Function ID. Otherwise, the value is
970used as a further index into the ``rt_svc_descs[]`` array to locate the required
971service and handler.
972
973The service's ``handle()`` callback is provided with five of the SMC parameters
974directly, the others are saved into memory for retrieval (if needed) by the
975handler. The handler is also provided with an opaque ``handle`` for use with the
976supporting library for parameter retrieval, setting return values and context
977manipulation; and with ``flags`` indicating the security state of the caller. The
978framework finally sets up the execution stack for the handler, and invokes the
979services ``handle()`` function.
980
981On return from the handler the result registers are populated in X0-X3 before
982restoring the stack and CPU state and returning from the original SMC.
983
Jeenu Viswambharancbb40d52017-10-18 14:30:53 +0100984Exception Handling Framework
985----------------------------
986
987Please refer to the `Exception Handling Framework`_ document.
988
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100989Power State Coordination Interface
990----------------------------------
991
992TODO: Provide design walkthrough of PSCI implementation.
993
Roberto Vargasd963e3e2017-09-12 10:28:35 +0100994The PSCI v1.1 specification categorizes APIs as optional and mandatory. All the
995mandatory APIs in PSCI v1.1, PSCI v1.0 and in PSCI v0.2 draft specification
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100996`Power State Coordination Interface PDD`_ are implemented. The table lists
Roberto Vargasd963e3e2017-09-12 10:28:35 +0100997the PSCI v1.1 APIs and their support in generic code.
Douglas Raillardd7c21b72017-06-28 15:23:03 +0100998
Sandrine Bailleux15530dd2019-02-08 15:26:36 +0100999An API implementation might have a dependency on platform code e.g. CPU_SUSPEND
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001000requires the platform to export a part of the implementation. Hence the level
1001of support of the mandatory APIs depends upon the support exported by the
1002platform port as well. The Juno and FVP (all variants) platforms export all the
1003required support.
1004
1005+-----------------------------+-------------+-------------------------------+
Roberto Vargasd963e3e2017-09-12 10:28:35 +01001006| PSCI v1.1 API | Supported | Comments |
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001007+=============================+=============+===============================+
Roberto Vargasd963e3e2017-09-12 10:28:35 +01001008| ``PSCI_VERSION`` | Yes | The version returned is 1.1 |
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001009+-----------------------------+-------------+-------------------------------+
1010| ``CPU_SUSPEND`` | Yes\* | |
1011+-----------------------------+-------------+-------------------------------+
1012| ``CPU_OFF`` | Yes\* | |
1013+-----------------------------+-------------+-------------------------------+
1014| ``CPU_ON`` | Yes\* | |
1015+-----------------------------+-------------+-------------------------------+
1016| ``AFFINITY_INFO`` | Yes | |
1017+-----------------------------+-------------+-------------------------------+
1018| ``MIGRATE`` | Yes\*\* | |
1019+-----------------------------+-------------+-------------------------------+
1020| ``MIGRATE_INFO_TYPE`` | Yes\*\* | |
1021+-----------------------------+-------------+-------------------------------+
1022| ``MIGRATE_INFO_CPU`` | Yes\*\* | |
1023+-----------------------------+-------------+-------------------------------+
1024| ``SYSTEM_OFF`` | Yes\* | |
1025+-----------------------------+-------------+-------------------------------+
1026| ``SYSTEM_RESET`` | Yes\* | |
1027+-----------------------------+-------------+-------------------------------+
1028| ``PSCI_FEATURES`` | Yes | |
1029+-----------------------------+-------------+-------------------------------+
1030| ``CPU_FREEZE`` | No | |
1031+-----------------------------+-------------+-------------------------------+
1032| ``CPU_DEFAULT_SUSPEND`` | No | |
1033+-----------------------------+-------------+-------------------------------+
1034| ``NODE_HW_STATE`` | Yes\* | |
1035+-----------------------------+-------------+-------------------------------+
1036| ``SYSTEM_SUSPEND`` | Yes\* | |
1037+-----------------------------+-------------+-------------------------------+
1038| ``PSCI_SET_SUSPEND_MODE`` | No | |
1039+-----------------------------+-------------+-------------------------------+
1040| ``PSCI_STAT_RESIDENCY`` | Yes\* | |
1041+-----------------------------+-------------+-------------------------------+
1042| ``PSCI_STAT_COUNT`` | Yes\* | |
1043+-----------------------------+-------------+-------------------------------+
Roberto Vargasd963e3e2017-09-12 10:28:35 +01001044| ``SYSTEM_RESET2`` | Yes\* | |
1045+-----------------------------+-------------+-------------------------------+
1046| ``MEM_PROTECT`` | Yes\* | |
1047+-----------------------------+-------------+-------------------------------+
1048| ``MEM_PROTECT_CHECK_RANGE`` | Yes\* | |
1049+-----------------------------+-------------+-------------------------------+
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001050
1051\*Note : These PSCI APIs require platform power management hooks to be
1052registered with the generic PSCI code to be supported.
1053
1054\*\*Note : These PSCI APIs require appropriate Secure Payload Dispatcher
1055hooks to be registered with the generic PSCI code to be supported.
1056
Dan Handley610e7e12018-03-01 18:44:00 +00001057The PSCI implementation in TF-A is a library which can be integrated with
1058AArch64 or AArch32 EL3 Runtime Software for Armv8-A systems. A guide to
1059integrating PSCI library with AArch32 EL3 Runtime Software can be found
1060`here`_.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001061
1062Secure-EL1 Payloads and Dispatchers
1063-----------------------------------
1064
1065On a production system that includes a Trusted OS running in Secure-EL1/EL0,
1066the Trusted OS is coupled with a companion runtime service in the BL31
1067firmware. This service is responsible for the initialisation of the Trusted
1068OS and all communications with it. The Trusted OS is the BL32 stage of the
Dan Handley610e7e12018-03-01 18:44:00 +00001069boot flow in TF-A. The firmware will attempt to locate, load and execute a
1070BL32 image.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001071
Dan Handley610e7e12018-03-01 18:44:00 +00001072TF-A uses a more general term for the BL32 software that runs at Secure-EL1 -
1073the *Secure-EL1 Payload* - as it is not always a Trusted OS.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001074
Dan Handley610e7e12018-03-01 18:44:00 +00001075TF-A provides a Test Secure-EL1 Payload (TSP) and a Test Secure-EL1 Payload
1076Dispatcher (TSPD) service as an example of how a Trusted OS is supported on a
1077production system using the Runtime Services Framework. On such a system, the
1078Test BL32 image and service are replaced by the Trusted OS and its dispatcher
1079service. The TF-A build system expects that the dispatcher will define the
1080build flag ``NEED_BL32`` to enable it to include the BL32 in the build either
1081as a binary or to compile from source depending on whether the ``BL32`` build
1082option is specified or not.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001083
1084The TSP runs in Secure-EL1. It is designed to demonstrate synchronous
1085communication with the normal-world software running in EL1/EL2. Communication
1086is initiated by the normal-world software
1087
1088- either directly through a Fast SMC (as defined in the `SMCCC`_)
1089
1090- or indirectly through a `PSCI`_ SMC. The `PSCI`_ implementation in turn
1091 informs the TSPD about the requested power management operation. This allows
1092 the TSP to prepare for or respond to the power state change
1093
1094The TSPD service is responsible for.
1095
1096- Initializing the TSP
1097
1098- Routing requests and responses between the secure and the non-secure
1099 states during the two types of communications just described
1100
1101Initializing a BL32 Image
1102~~~~~~~~~~~~~~~~~~~~~~~~~
1103
1104The Secure-EL1 Payload Dispatcher (SPD) service is responsible for initializing
1105the BL32 image. It needs access to the information passed by BL2 to BL31 to do
1106so. This is provided by:
1107
1108.. code:: c
1109
1110 entry_point_info_t *bl31_plat_get_next_image_ep_info(uint32_t);
1111
1112which returns a reference to the ``entry_point_info`` structure corresponding to
1113the image which will be run in the specified security state. The SPD uses this
1114API to get entry point information for the SECURE image, BL32.
1115
1116In the absence of a BL32 image, BL31 passes control to the normal world
1117bootloader image (BL33). When the BL32 image is present, it is typical
1118that the SPD wants control to be passed to BL32 first and then later to BL33.
1119
1120To do this the SPD has to register a BL32 initialization function during
1121initialization of the SPD service. The BL32 initialization function has this
1122prototype:
1123
1124.. code:: c
1125
1126 int32_t init(void);
1127
1128and is registered using the ``bl31_register_bl32_init()`` function.
1129
Dan Handley610e7e12018-03-01 18:44:00 +00001130TF-A supports two approaches for the SPD to pass control to BL32 before
1131returning through EL3 and running the non-trusted firmware (BL33):
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001132
1133#. In the BL32 setup function, use ``bl31_set_next_image_type()`` to
1134 request that the exit from ``bl31_main()`` is to the BL32 entrypoint in
1135 Secure-EL1. BL31 will exit to BL32 using the asynchronous method by
1136 calling ``bl31_prepare_next_image_entry()`` and ``el3_exit()``.
1137
1138 When the BL32 has completed initialization at Secure-EL1, it returns to
1139 BL31 by issuing an SMC, using a Function ID allocated to the SPD. On
1140 receipt of this SMC, the SPD service handler should switch the CPU context
1141 from trusted to normal world and use the ``bl31_set_next_image_type()`` and
1142 ``bl31_prepare_next_image_entry()`` functions to set up the initial return to
1143 the normal world firmware BL33. On return from the handler the framework
1144 will exit to EL2 and run BL33.
1145
1146#. The BL32 setup function registers an initialization function using
1147 ``bl31_register_bl32_init()`` which provides a SPD-defined mechanism to
1148 invoke a 'world-switch synchronous call' to Secure-EL1 to run the BL32
1149 entrypoint.
Dan Handley610e7e12018-03-01 18:44:00 +00001150 NOTE: The Test SPD service included with TF-A provides one implementation
1151 of such a mechanism.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001152
1153 On completion BL32 returns control to BL31 via a SMC, and on receipt the
1154 SPD service handler invokes the synchronous call return mechanism to return
1155 to the BL32 initialization function. On return from this function,
1156 ``bl31_main()`` will set up the return to the normal world firmware BL33 and
1157 continue the boot process in the normal world.
1158
Jeenu Viswambharanb60420a2017-08-24 15:43:44 +01001159Crash Reporting in BL31
1160-----------------------
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001161
1162BL31 implements a scheme for reporting the processor state when an unhandled
1163exception is encountered. The reporting mechanism attempts to preserve all the
1164register contents and report it via a dedicated UART (PL011 console). BL31
1165reports the general purpose, EL3, Secure EL1 and some EL2 state registers.
1166
1167A dedicated per-CPU crash stack is maintained by BL31 and this is retrieved via
1168the per-CPU pointer cache. The implementation attempts to minimise the memory
1169required for this feature. The file ``crash_reporting.S`` contains the
1170implementation for crash reporting.
1171
1172The sample crash output is shown below.
1173
1174::
1175
1176 x0 :0x000000004F00007C
1177 x1 :0x0000000007FFFFFF
1178 x2 :0x0000000004014D50
1179 x3 :0x0000000000000000
1180 x4 :0x0000000088007998
1181 x5 :0x00000000001343AC
1182 x6 :0x0000000000000016
1183 x7 :0x00000000000B8A38
1184 x8 :0x00000000001343AC
1185 x9 :0x00000000000101A8
1186 x10 :0x0000000000000002
1187 x11 :0x000000000000011C
1188 x12 :0x00000000FEFDC644
1189 x13 :0x00000000FED93FFC
1190 x14 :0x0000000000247950
1191 x15 :0x00000000000007A2
1192 x16 :0x00000000000007A4
1193 x17 :0x0000000000247950
1194 x18 :0x0000000000000000
1195 x19 :0x00000000FFFFFFFF
1196 x20 :0x0000000004014D50
1197 x21 :0x000000000400A38C
1198 x22 :0x0000000000247950
1199 x23 :0x0000000000000010
1200 x24 :0x0000000000000024
1201 x25 :0x00000000FEFDC868
1202 x26 :0x00000000FEFDC86A
1203 x27 :0x00000000019EDEDC
1204 x28 :0x000000000A7CFDAA
1205 x29 :0x0000000004010780
1206 x30 :0x000000000400F004
1207 scr_el3 :0x0000000000000D3D
1208 sctlr_el3 :0x0000000000C8181F
1209 cptr_el3 :0x0000000000000000
1210 tcr_el3 :0x0000000080803520
1211 daif :0x00000000000003C0
1212 mair_el3 :0x00000000000004FF
1213 spsr_el3 :0x00000000800003CC
1214 elr_el3 :0x000000000400C0CC
1215 ttbr0_el3 :0x00000000040172A0
1216 esr_el3 :0x0000000096000210
1217 sp_el3 :0x0000000004014D50
1218 far_el3 :0x000000004F00007C
1219 spsr_el1 :0x0000000000000000
1220 elr_el1 :0x0000000000000000
1221 spsr_abt :0x0000000000000000
1222 spsr_und :0x0000000000000000
1223 spsr_irq :0x0000000000000000
1224 spsr_fiq :0x0000000000000000
1225 sctlr_el1 :0x0000000030C81807
1226 actlr_el1 :0x0000000000000000
1227 cpacr_el1 :0x0000000000300000
1228 csselr_el1 :0x0000000000000002
1229 sp_el1 :0x0000000004028800
1230 esr_el1 :0x0000000000000000
1231 ttbr0_el1 :0x000000000402C200
1232 ttbr1_el1 :0x0000000000000000
1233 mair_el1 :0x00000000000004FF
1234 amair_el1 :0x0000000000000000
1235 tcr_el1 :0x0000000000003520
1236 tpidr_el1 :0x0000000000000000
1237 tpidr_el0 :0x0000000000000000
1238 tpidrro_el0 :0x0000000000000000
1239 dacr32_el2 :0x0000000000000000
1240 ifsr32_el2 :0x0000000000000000
1241 par_el1 :0x0000000000000000
1242 far_el1 :0x0000000000000000
1243 afsr0_el1 :0x0000000000000000
1244 afsr1_el1 :0x0000000000000000
1245 contextidr_el1 :0x0000000000000000
1246 vbar_el1 :0x0000000004027000
1247 cntp_ctl_el0 :0x0000000000000000
1248 cntp_cval_el0 :0x0000000000000000
1249 cntv_ctl_el0 :0x0000000000000000
1250 cntv_cval_el0 :0x0000000000000000
1251 cntkctl_el1 :0x0000000000000000
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001252 sp_el0 :0x0000000004010780
1253
1254Guidelines for Reset Handlers
1255-----------------------------
1256
Dan Handley610e7e12018-03-01 18:44:00 +00001257TF-A implements a framework that allows CPU and platform ports to perform
1258actions very early after a CPU is released from reset in both the cold and warm
1259boot paths. This is done by calling the ``reset_handler()`` function in both
1260the BL1 and BL31 images. It in turn calls the platform and CPU specific reset
1261handling functions.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001262
1263Details for implementing a CPU specific reset handler can be found in
1264Section 8. Details for implementing a platform specific reset handler can be
1265found in the `Porting Guide`_ (see the ``plat_reset_handler()`` function).
1266
1267When adding functionality to a reset handler, keep in mind that if a different
1268reset handling behavior is required between the first and the subsequent
1269invocations of the reset handling code, this should be detected at runtime.
1270In other words, the reset handler should be able to detect whether an action has
1271already been performed and act as appropriate. Possible courses of actions are,
1272e.g. skip the action the second time, or undo/redo it.
1273
Jeenu Viswambharanaeb267c2017-09-22 08:32:09 +01001274Configuring secure interrupts
1275-----------------------------
1276
1277The GIC driver is responsible for performing initial configuration of secure
1278interrupts on the platform. To this end, the platform is expected to provide the
1279GIC driver (either GICv2 or GICv3, as selected by the platform) with the
1280interrupt configuration during the driver initialisation.
1281
Antonio Nino Diaz29b9f5b2018-09-24 17:23:24 +01001282Secure interrupt configuration are specified in an array of secure interrupt
1283properties. In this scheme, in both GICv2 and GICv3 driver data structures, the
1284``interrupt_props`` member points to an array of interrupt properties. Each
Antonio Nino Diaz56b68ad2019-02-28 13:35:21 +00001285element of the array specifies the interrupt number and its attributes
1286(priority, group, configuration). Each element of the array shall be populated
1287by the macro ``INTR_PROP_DESC()``. The macro takes the following arguments:
Jeenu Viswambharanaeb267c2017-09-22 08:32:09 +01001288
Antonio Nino Diaz29b9f5b2018-09-24 17:23:24 +01001289- 10-bit interrupt number,
Jeenu Viswambharanaeb267c2017-09-22 08:32:09 +01001290
Antonio Nino Diaz29b9f5b2018-09-24 17:23:24 +01001291- 8-bit interrupt priority,
Jeenu Viswambharanaeb267c2017-09-22 08:32:09 +01001292
Antonio Nino Diaz29b9f5b2018-09-24 17:23:24 +01001293- Interrupt type (one of ``INTR_TYPE_EL3``, ``INTR_TYPE_S_EL1``,
1294 ``INTR_TYPE_NS``),
Jeenu Viswambharanaeb267c2017-09-22 08:32:09 +01001295
Antonio Nino Diaz29b9f5b2018-09-24 17:23:24 +01001296- Interrupt configuration (either ``GIC_INTR_CFG_LEVEL`` or
1297 ``GIC_INTR_CFG_EDGE``).
Jeenu Viswambharanaeb267c2017-09-22 08:32:09 +01001298
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001299CPU specific operations framework
1300---------------------------------
1301
Dan Handley610e7e12018-03-01 18:44:00 +00001302Certain aspects of the Armv8-A architecture are implementation defined,
1303that is, certain behaviours are not architecturally defined, but must be
1304defined and documented by individual processor implementations. TF-A
1305implements a framework which categorises the common implementation defined
1306behaviours and allows a processor to export its implementation of that
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001307behaviour. The categories are:
1308
1309#. Processor specific reset sequence.
1310
1311#. Processor specific power down sequences.
1312
1313#. Processor specific register dumping as a part of crash reporting.
1314
1315#. Errata status reporting.
1316
1317Each of the above categories fulfils a different requirement.
1318
1319#. allows any processor specific initialization before the caches and MMU
1320 are turned on, like implementation of errata workarounds, entry into
1321 the intra-cluster coherency domain etc.
1322
1323#. allows each processor to implement the power down sequence mandated in
1324 its Technical Reference Manual (TRM).
1325
1326#. allows a processor to provide additional information to the developer
1327 in the event of a crash, for example Cortex-A53 has registers which
1328 can expose the data cache contents.
1329
1330#. allows a processor to define a function that inspects and reports the status
1331 of all errata workarounds on that processor.
1332
1333Please note that only 2. is mandated by the TRM.
1334
1335The CPU specific operations framework scales to accommodate a large number of
1336different CPUs during power down and reset handling. The platform can specify
1337any CPU optimization it wants to enable for each CPU. It can also specify
1338the CPU errata workarounds to be applied for each CPU type during reset
1339handling by defining CPU errata compile time macros. Details on these macros
1340can be found in the `cpu-specific-build-macros.rst`_ file.
1341
1342The CPU specific operations framework depends on the ``cpu_ops`` structure which
1343needs to be exported for each type of CPU in the platform. It is defined in
1344``include/lib/cpus/aarch64/cpu_macros.S`` and has the following fields : ``midr``,
1345``reset_func()``, ``cpu_pwr_down_ops`` (array of power down functions) and
1346``cpu_reg_dump()``.
1347
1348The CPU specific files in ``lib/cpus`` export a ``cpu_ops`` data structure with
1349suitable handlers for that CPU. For example, ``lib/cpus/aarch64/cortex_a53.S``
1350exports the ``cpu_ops`` for Cortex-A53 CPU. According to the platform
1351configuration, these CPU specific files must be included in the build by
1352the platform makefile. The generic CPU specific operations framework code exists
1353in ``lib/cpus/aarch64/cpu_helpers.S``.
1354
1355CPU specific Reset Handling
1356~~~~~~~~~~~~~~~~~~~~~~~~~~~
1357
1358After a reset, the state of the CPU when it calls generic reset handler is:
1359MMU turned off, both instruction and data caches turned off and not part
1360of any coherency domain.
1361
1362The BL entrypoint code first invokes the ``plat_reset_handler()`` to allow
1363the platform to perform any system initialization required and any system
1364errata workarounds that needs to be applied. The ``get_cpu_ops_ptr()`` reads
1365the current CPU midr, finds the matching ``cpu_ops`` entry in the ``cpu_ops``
1366array and returns it. Note that only the part number and implementer fields
1367in midr are used to find the matching ``cpu_ops`` entry. The ``reset_func()`` in
1368the returned ``cpu_ops`` is then invoked which executes the required reset
1369handling for that CPU and also any errata workarounds enabled by the platform.
1370This function must preserve the values of general purpose registers x20 to x29.
1371
1372Refer to Section "Guidelines for Reset Handlers" for general guidelines
1373regarding placement of code in a reset handler.
1374
1375CPU specific power down sequence
1376~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1377
1378During the BL31 initialization sequence, the pointer to the matching ``cpu_ops``
1379entry is stored in per-CPU data by ``init_cpu_ops()`` so that it can be quickly
1380retrieved during power down sequences.
1381
1382Various CPU drivers register handlers to perform power down at certain power
1383levels for that specific CPU. The PSCI service, upon receiving a power down
1384request, determines the highest power level at which to execute power down
1385sequence for a particular CPU. It uses the ``prepare_cpu_pwr_dwn()`` function to
1386pick the right power down handler for the requested level. The function
1387retrieves ``cpu_ops`` pointer member of per-CPU data, and from that, further
1388retrieves ``cpu_pwr_down_ops`` array, and indexes into the required level. If the
1389requested power level is higher than what a CPU driver supports, the handler
1390registered for highest level is invoked.
1391
1392At runtime the platform hooks for power down are invoked by the PSCI service to
1393perform platform specific operations during a power down sequence, for example
1394turning off CCI coherency during a cluster power down.
1395
1396CPU specific register reporting during crash
1397~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1398
1399If the crash reporting is enabled in BL31, when a crash occurs, the crash
1400reporting framework calls ``do_cpu_reg_dump`` which retrieves the matching
1401``cpu_ops`` using ``get_cpu_ops_ptr()`` function. The ``cpu_reg_dump()`` in
1402``cpu_ops`` is invoked, which then returns the CPU specific register values to
1403be reported and a pointer to the ASCII list of register names in a format
1404expected by the crash reporting framework.
1405
1406CPU errata status reporting
1407~~~~~~~~~~~~~~~~~~~~~~~~~~~
1408
Dan Handley610e7e12018-03-01 18:44:00 +00001409Errata workarounds for CPUs supported in TF-A are applied during both cold and
1410warm boots, shortly after reset. Individual Errata workarounds are enabled as
1411build options. Some errata workarounds have potential run-time implications;
1412therefore some are enabled by default, others not. Platform ports shall
1413override build options to enable or disable errata as appropriate. The CPU
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001414drivers take care of applying errata workarounds that are enabled and applicable
1415to a given CPU. Refer to the section titled *CPU Errata Workarounds* in `CPUBM`_
1416for more information.
1417
1418Functions in CPU drivers that apply errata workaround must follow the
1419conventions listed below.
1420
1421The errata workaround must be authored as two separate functions:
1422
1423- One that checks for errata. This function must determine whether that errata
1424 applies to the current CPU. Typically this involves matching the current
1425 CPUs revision and variant against a value that's known to be affected by the
1426 errata. If the function determines that the errata applies to this CPU, it
1427 must return ``ERRATA_APPLIES``; otherwise, it must return
1428 ``ERRATA_NOT_APPLIES``. The utility functions ``cpu_get_rev_var`` and
1429 ``cpu_rev_var_ls`` functions may come in handy for this purpose.
1430
1431For an errata identified as ``E``, the check function must be named
1432``check_errata_E``.
1433
1434This function will be invoked at different times, both from assembly and from
1435C run time. Therefore it must follow AAPCS, and must not use stack.
1436
1437- Another one that applies the errata workaround. This function would call the
1438 check function described above, and applies errata workaround if required.
1439
1440CPU drivers that apply errata workaround can optionally implement an assembly
1441function that report the status of errata workarounds pertaining to that CPU.
Antonio Nino Diaz56b68ad2019-02-28 13:35:21 +00001442For a driver that registers the CPU, for example, ``cpux`` via ``declare_cpu_ops``
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001443macro, the errata reporting function, if it exists, must be named
1444``cpux_errata_report``. This function will always be called with MMU enabled; it
1445must follow AAPCS and may use stack.
1446
Dan Handley610e7e12018-03-01 18:44:00 +00001447In a debug build of TF-A, on a CPU that comes out of reset, both BL1 and the
1448runtime firmware (BL31 in AArch64, and BL32 in AArch32) will invoke errata
1449status reporting function, if one exists, for that type of CPU.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001450
1451To report the status of each errata workaround, the function shall use the
1452assembler macro ``report_errata``, passing it:
1453
1454- The build option that enables the errata;
1455
1456- The name of the CPU: this must be the same identifier that CPU driver
1457 registered itself with, using ``declare_cpu_ops``;
1458
1459- And the errata identifier: the identifier must match what's used in the
1460 errata's check function described above.
1461
1462The errata status reporting function will be called once per CPU type/errata
1463combination during the software's active life time.
1464
Dan Handley610e7e12018-03-01 18:44:00 +00001465It's expected that whenever an errata workaround is submitted to TF-A, the
1466errata reporting function is appropriately extended to report its status as
1467well.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001468
1469Reporting the status of errata workaround is for informational purpose only; it
1470has no functional significance.
1471
1472Memory layout of BL images
1473--------------------------
1474
1475Each bootloader image can be divided in 2 parts:
1476
1477- the static contents of the image. These are data actually stored in the
1478 binary on the disk. In the ELF terminology, they are called ``PROGBITS``
1479 sections;
1480
1481- the run-time contents of the image. These are data that don't occupy any
1482 space in the binary on the disk. The ELF binary just contains some
1483 metadata indicating where these data will be stored at run-time and the
1484 corresponding sections need to be allocated and initialized at run-time.
1485 In the ELF terminology, they are called ``NOBITS`` sections.
1486
1487All PROGBITS sections are grouped together at the beginning of the image,
Dan Handley610e7e12018-03-01 18:44:00 +00001488followed by all NOBITS sections. This is true for all TF-A images and it is
1489governed by the linker scripts. This ensures that the raw binary images are
1490as small as possible. If a NOBITS section was inserted in between PROGBITS
1491sections then the resulting binary file would contain zero bytes in place of
1492this NOBITS section, making the image unnecessarily bigger. Smaller images
1493allow faster loading from the FIP to the main memory.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001494
1495Linker scripts and symbols
1496~~~~~~~~~~~~~~~~~~~~~~~~~~
1497
1498Each bootloader stage image layout is described by its own linker script. The
1499linker scripts export some symbols into the program symbol table. Their values
Dan Handley610e7e12018-03-01 18:44:00 +00001500correspond to particular addresses. TF-A code can refer to these symbols to
1501figure out the image memory layout.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001502
Dan Handley610e7e12018-03-01 18:44:00 +00001503Linker symbols follow the following naming convention in TF-A.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001504
1505- ``__<SECTION>_START__``
1506
1507 Start address of a given section named ``<SECTION>``.
1508
1509- ``__<SECTION>_END__``
1510
1511 End address of a given section named ``<SECTION>``. If there is an alignment
1512 constraint on the section's end address then ``__<SECTION>_END__`` corresponds
1513 to the end address of the section's actual contents, rounded up to the right
1514 boundary. Refer to the value of ``__<SECTION>_UNALIGNED_END__`` to know the
1515 actual end address of the section's contents.
1516
1517- ``__<SECTION>_UNALIGNED_END__``
1518
1519 End address of a given section named ``<SECTION>`` without any padding or
1520 rounding up due to some alignment constraint.
1521
1522- ``__<SECTION>_SIZE__``
1523
1524 Size (in bytes) of a given section named ``<SECTION>``. If there is an
1525 alignment constraint on the section's end address then ``__<SECTION>_SIZE__``
1526 corresponds to the size of the section's actual contents, rounded up to the
1527 right boundary. In other words, ``__<SECTION>_SIZE__ = __<SECTION>_END__ - _<SECTION>_START__``. Refer to the value of ``__<SECTION>_UNALIGNED_SIZE__``
1528 to know the actual size of the section's contents.
1529
1530- ``__<SECTION>_UNALIGNED_SIZE__``
1531
1532 Size (in bytes) of a given section named ``<SECTION>`` without any padding or
1533 rounding up due to some alignment constraint. In other words,
1534 ``__<SECTION>_UNALIGNED_SIZE__ = __<SECTION>_UNALIGNED_END__ - __<SECTION>_START__``.
1535
Dan Handley610e7e12018-03-01 18:44:00 +00001536Some of the linker symbols are mandatory as TF-A code relies on them to be
1537defined. They are listed in the following subsections. Some of them must be
1538provided for each bootloader stage and some are specific to a given bootloader
1539stage.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001540
1541The linker scripts define some extra, optional symbols. They are not actually
1542used by any code but they help in understanding the bootloader images' memory
1543layout as they are easy to spot in the link map files.
1544
1545Common linker symbols
1546^^^^^^^^^^^^^^^^^^^^^
1547
1548All BL images share the following requirements:
1549
1550- The BSS section must be zero-initialised before executing any C code.
1551- The coherent memory section (if enabled) must be zero-initialised as well.
1552- The MMU setup code needs to know the extents of the coherent and read-only
1553 memory regions to set the right memory attributes. When
1554 ``SEPARATE_CODE_AND_RODATA=1``, it needs to know more specifically how the
1555 read-only memory region is divided between code and data.
1556
1557The following linker symbols are defined for this purpose:
1558
1559- ``__BSS_START__``
1560- ``__BSS_SIZE__``
1561- ``__COHERENT_RAM_START__`` Must be aligned on a page-size boundary.
1562- ``__COHERENT_RAM_END__`` Must be aligned on a page-size boundary.
1563- ``__COHERENT_RAM_UNALIGNED_SIZE__``
1564- ``__RO_START__``
1565- ``__RO_END__``
1566- ``__TEXT_START__``
1567- ``__TEXT_END__``
1568- ``__RODATA_START__``
1569- ``__RODATA_END__``
1570
1571BL1's linker symbols
1572^^^^^^^^^^^^^^^^^^^^
1573
1574BL1 being the ROM image, it has additional requirements. BL1 resides in ROM and
1575it is entirely executed in place but it needs some read-write memory for its
1576mutable data. Its ``.data`` section (i.e. its allocated read-write data) must be
1577relocated from ROM to RAM before executing any C code.
1578
1579The following additional linker symbols are defined for BL1:
1580
1581- ``__BL1_ROM_END__`` End address of BL1's ROM contents, covering its code
1582 and ``.data`` section in ROM.
1583- ``__DATA_ROM_START__`` Start address of the ``.data`` section in ROM. Must be
1584 aligned on a 16-byte boundary.
1585- ``__DATA_RAM_START__`` Address in RAM where the ``.data`` section should be
1586 copied over. Must be aligned on a 16-byte boundary.
1587- ``__DATA_SIZE__`` Size of the ``.data`` section (in ROM or RAM).
1588- ``__BL1_RAM_START__`` Start address of BL1 read-write data.
1589- ``__BL1_RAM_END__`` End address of BL1 read-write data.
1590
1591How to choose the right base addresses for each bootloader stage image
1592~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1593
Dan Handley610e7e12018-03-01 18:44:00 +00001594There is currently no support for dynamic image loading in TF-A. This means
1595that all bootloader images need to be linked against their ultimate runtime
1596locations and the base addresses of each image must be chosen carefully such
1597that images don't overlap each other in an undesired way. As the code grows,
1598the base addresses might need adjustments to cope with the new memory layout.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001599
1600The memory layout is completely specific to the platform and so there is no
1601general recipe for choosing the right base addresses for each bootloader image.
1602However, there are tools to aid in understanding the memory layout. These are
1603the link map files: ``build/<platform>/<build-type>/bl<x>/bl<x>.map``, with ``<x>``
1604being the stage bootloader. They provide a detailed view of the memory usage of
1605each image. Among other useful information, they provide the end address of
1606each image.
1607
1608- ``bl1.map`` link map file provides ``__BL1_RAM_END__`` address.
1609- ``bl2.map`` link map file provides ``__BL2_END__`` address.
1610- ``bl31.map`` link map file provides ``__BL31_END__`` address.
1611- ``bl32.map`` link map file provides ``__BL32_END__`` address.
1612
1613For each bootloader image, the platform code must provide its start address
1614as well as a limit address that it must not overstep. The latter is used in the
1615linker scripts to check that the image doesn't grow past that address. If that
1616happens, the linker will issue a message similar to the following:
1617
1618::
1619
1620 aarch64-none-elf-ld: BLx has exceeded its limit.
1621
1622Additionally, if the platform memory layout implies some image overlaying like
1623on FVP, BL31 and TSP need to know the limit address that their PROGBITS
1624sections must not overstep. The platform code must provide those.
1625
Soby Mathew97b1bff2018-09-27 16:46:41 +01001626TF-A does not provide any mechanism to verify at boot time that the memory
1627to load a new image is free to prevent overwriting a previously loaded image.
1628The platform must specify the memory available in the system for all the
1629relevant BL images to be loaded.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001630
1631For example, in the case of BL1 loading BL2, ``bl1_plat_sec_mem_layout()`` will
1632return the region defined by the platform where BL1 intends to load BL2. The
1633``load_image()`` function performs bounds check for the image size based on the
1634base and maximum image size provided by the platforms. Platforms must take
1635this behaviour into account when defining the base/size for each of the images.
1636
Dan Handley610e7e12018-03-01 18:44:00 +00001637Memory layout on Arm development platforms
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001638^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1639
Dan Handley610e7e12018-03-01 18:44:00 +00001640The following list describes the memory layout on the Arm development platforms:
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001641
1642- A 4KB page of shared memory is used for communication between Trusted
1643 Firmware and the platform's power controller. This is located at the base of
1644 Trusted SRAM. The amount of Trusted SRAM available to load the bootloader
1645 images is reduced by the size of the shared memory.
1646
1647 The shared memory is used to store the CPUs' entrypoint mailbox. On Juno,
1648 this is also used for the MHU payload when passing messages to and from the
1649 SCP.
1650
Soby Mathew492e2452018-06-06 16:03:10 +01001651- Another 4 KB page is reserved for passing memory layout between BL1 and BL2
1652 and also the dynamic firmware configurations.
1653
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001654- On FVP, BL1 is originally sitting in the Trusted ROM at address ``0x0``. On
1655 Juno, BL1 resides in flash memory at address ``0x0BEC0000``. BL1 read-write
1656 data are relocated to the top of Trusted SRAM at runtime.
1657
Soby Mathew492e2452018-06-06 16:03:10 +01001658- BL2 is loaded below BL1 RW
1659
Sandrine Bailleux15530dd2019-02-08 15:26:36 +01001660- EL3 Runtime Software, BL31 for AArch64 and BL32 for AArch32 (e.g. SP_MIN),
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001661 is loaded at the top of the Trusted SRAM, such that its NOBITS sections will
Soby Mathew492e2452018-06-06 16:03:10 +01001662 overwrite BL1 R/W data and BL2. This implies that BL1 global variables
1663 remain valid only until execution reaches the EL3 Runtime Software entry
1664 point during a cold boot.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001665
Sandrine Bailleux15530dd2019-02-08 15:26:36 +01001666- On Juno, SCP_BL2 is loaded temporarily into the EL3 Runtime Software memory
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001667 region and transfered to the SCP before being overwritten by EL3 Runtime
1668 Software.
1669
1670- BL32 (for AArch64) can be loaded in one of the following locations:
1671
1672 - Trusted SRAM
1673 - Trusted DRAM (FVP only)
1674 - Secure region of DRAM (top 16MB of DRAM configured by the TrustZone
1675 controller)
1676
Soby Mathew492e2452018-06-06 16:03:10 +01001677 When BL32 (for AArch64) is loaded into Trusted SRAM, it is loaded below
1678 BL31.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001679
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001680The location of the BL32 image will result in different memory maps. This is
1681illustrated for both FVP and Juno in the following diagrams, using the TSP as
1682an example.
1683
1684Note: Loading the BL32 image in TZC secured DRAM doesn't change the memory
1685layout of the other images in Trusted SRAM.
1686
Sathees Balya90950092018-11-15 14:22:30 +00001687CONFIG section in memory layouts shown below contains:
1688
1689::
1690
1691 +--------------------+
1692 |bl2_mem_params_descs|
1693 |--------------------|
1694 | fw_configs |
1695 +--------------------+
1696
1697``bl2_mem_params_descs`` contains parameters passed from BL2 to next the
1698BL image during boot.
1699
1700``fw_configs`` includes soc_fw_config, tos_fw_config and tb_fw_config.
1701
Soby Mathew492e2452018-06-06 16:03:10 +01001702**FVP with TSP in Trusted SRAM with firmware configs :**
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001703(These diagrams only cover the AArch64 case)
1704
1705::
1706
Soby Mathew492e2452018-06-06 16:03:10 +01001707 DRAM
1708 0xffffffff +----------+
1709 : :
1710 |----------|
1711 |HW_CONFIG |
1712 0x83000000 |----------| (non-secure)
1713 | |
1714 0x80000000 +----------+
1715
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001716 Trusted SRAM
Soby Mathew492e2452018-06-06 16:03:10 +01001717 0x04040000 +----------+ loaded by BL2 +----------------+
1718 | BL1 (rw) | <<<<<<<<<<<<< | |
1719 |----------| <<<<<<<<<<<<< | BL31 NOBITS |
1720 | BL2 | <<<<<<<<<<<<< | |
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001721 |----------| <<<<<<<<<<<<< |----------------|
1722 | | <<<<<<<<<<<<< | BL31 PROGBITS |
Soby Mathew492e2452018-06-06 16:03:10 +01001723 | | <<<<<<<<<<<<< |----------------|
1724 | | <<<<<<<<<<<<< | BL32 |
1725 0x04002000 +----------+ +----------------+
Sathees Balya90950092018-11-15 14:22:30 +00001726 | CONFIG |
Soby Mathew492e2452018-06-06 16:03:10 +01001727 0x04001000 +----------+
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001728 | Shared |
1729 0x04000000 +----------+
1730
1731 Trusted ROM
1732 0x04000000 +----------+
1733 | BL1 (ro) |
1734 0x00000000 +----------+
1735
Soby Mathew492e2452018-06-06 16:03:10 +01001736**FVP with TSP in Trusted DRAM with firmware configs (default option):**
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001737
1738::
1739
Soby Mathewb1bf0442018-02-16 14:52:52 +00001740 DRAM
1741 0xffffffff +--------------+
1742 : :
1743 |--------------|
1744 | HW_CONFIG |
1745 0x83000000 |--------------| (non-secure)
1746 | |
1747 0x80000000 +--------------+
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001748
Soby Mathewb1bf0442018-02-16 14:52:52 +00001749 Trusted DRAM
1750 0x08000000 +--------------+
1751 | BL32 |
1752 0x06000000 +--------------+
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001753
Soby Mathewb1bf0442018-02-16 14:52:52 +00001754 Trusted SRAM
Soby Mathew492e2452018-06-06 16:03:10 +01001755 0x04040000 +--------------+ loaded by BL2 +----------------+
1756 | BL1 (rw) | <<<<<<<<<<<<< | |
1757 |--------------| <<<<<<<<<<<<< | BL31 NOBITS |
1758 | BL2 | <<<<<<<<<<<<< | |
Soby Mathewb1bf0442018-02-16 14:52:52 +00001759 |--------------| <<<<<<<<<<<<< |----------------|
1760 | | <<<<<<<<<<<<< | BL31 PROGBITS |
Soby Mathew492e2452018-06-06 16:03:10 +01001761 | | +----------------+
1762 +--------------+
Sathees Balya90950092018-11-15 14:22:30 +00001763 | CONFIG |
Soby Mathewb1bf0442018-02-16 14:52:52 +00001764 0x04001000 +--------------+
1765 | Shared |
1766 0x04000000 +--------------+
1767
1768 Trusted ROM
1769 0x04000000 +--------------+
1770 | BL1 (ro) |
1771 0x00000000 +--------------+
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001772
Soby Mathew492e2452018-06-06 16:03:10 +01001773**FVP with TSP in TZC-Secured DRAM with firmware configs :**
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001774
1775::
1776
1777 DRAM
1778 0xffffffff +----------+
Soby Mathewb1bf0442018-02-16 14:52:52 +00001779 | BL32 | (secure)
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001780 0xff000000 +----------+
1781 | |
Soby Mathew492e2452018-06-06 16:03:10 +01001782 |----------|
1783 |HW_CONFIG |
1784 0x83000000 |----------| (non-secure)
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001785 | |
1786 0x80000000 +----------+
1787
1788 Trusted SRAM
Soby Mathew492e2452018-06-06 16:03:10 +01001789 0x04040000 +----------+ loaded by BL2 +----------------+
1790 | BL1 (rw) | <<<<<<<<<<<<< | |
1791 |----------| <<<<<<<<<<<<< | BL31 NOBITS |
1792 | BL2 | <<<<<<<<<<<<< | |
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001793 |----------| <<<<<<<<<<<<< |----------------|
1794 | | <<<<<<<<<<<<< | BL31 PROGBITS |
Soby Mathew492e2452018-06-06 16:03:10 +01001795 | | +----------------+
1796 0x04002000 +----------+
Sathees Balya90950092018-11-15 14:22:30 +00001797 | CONFIG |
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001798 0x04001000 +----------+
1799 | Shared |
1800 0x04000000 +----------+
1801
1802 Trusted ROM
1803 0x04000000 +----------+
1804 | BL1 (ro) |
1805 0x00000000 +----------+
1806
Soby Mathew492e2452018-06-06 16:03:10 +01001807**Juno with BL32 in Trusted SRAM :**
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001808
1809::
1810
1811 Flash0
1812 0x0C000000 +----------+
1813 : :
1814 0x0BED0000 |----------|
1815 | BL1 (ro) |
1816 0x0BEC0000 |----------|
1817 : :
1818 0x08000000 +----------+ BL31 is loaded
1819 after SCP_BL2 has
1820 Trusted SRAM been sent to SCP
Soby Mathew492e2452018-06-06 16:03:10 +01001821 0x04040000 +----------+ loaded by BL2 +----------------+
1822 | BL1 (rw) | <<<<<<<<<<<<< | |
1823 |----------| <<<<<<<<<<<<< | BL31 NOBITS |
1824 | BL2 | <<<<<<<<<<<<< | |
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001825 |----------| <<<<<<<<<<<<< |----------------|
1826 | SCP_BL2 | <<<<<<<<<<<<< | BL31 PROGBITS |
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001827 |----------| <<<<<<<<<<<<< |----------------|
Soby Mathew492e2452018-06-06 16:03:10 +01001828 | | <<<<<<<<<<<<< | BL32 |
1829 | | +----------------+
1830 | |
1831 0x04001000 +----------+
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001832 | MHU |
1833 0x04000000 +----------+
1834
Soby Mathew492e2452018-06-06 16:03:10 +01001835**Juno with BL32 in TZC-secured DRAM :**
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001836
1837::
1838
1839 DRAM
1840 0xFFE00000 +----------+
Soby Mathewb1bf0442018-02-16 14:52:52 +00001841 | BL32 | (secure)
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001842 0xFF000000 |----------|
1843 | |
1844 : : (non-secure)
1845 | |
1846 0x80000000 +----------+
1847
1848 Flash0
1849 0x0C000000 +----------+
1850 : :
1851 0x0BED0000 |----------|
1852 | BL1 (ro) |
1853 0x0BEC0000 |----------|
1854 : :
1855 0x08000000 +----------+ BL31 is loaded
1856 after SCP_BL2 has
1857 Trusted SRAM been sent to SCP
Soby Mathew492e2452018-06-06 16:03:10 +01001858 0x04040000 +----------+ loaded by BL2 +----------------+
1859 | BL1 (rw) | <<<<<<<<<<<<< | |
1860 |----------| <<<<<<<<<<<<< | BL31 NOBITS |
1861 | BL2 | <<<<<<<<<<<<< | |
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001862 |----------| <<<<<<<<<<<<< |----------------|
1863 | SCP_BL2 | <<<<<<<<<<<<< | BL31 PROGBITS |
Soby Mathew492e2452018-06-06 16:03:10 +01001864 |----------| +----------------+
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001865 0x04001000 +----------+
1866 | MHU |
1867 0x04000000 +----------+
1868
Sathees Balya17d8eed2019-01-30 15:56:44 +00001869Library at ROM
1870---------------
1871
1872Please refer to the `ROMLIB Design`_ document.
1873
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001874Firmware Image Package (FIP)
1875----------------------------
1876
1877Using a Firmware Image Package (FIP) allows for packing bootloader images (and
Dan Handley610e7e12018-03-01 18:44:00 +00001878potentially other payloads) into a single archive that can be loaded by TF-A
1879from non-volatile platform storage. A driver to load images from a FIP has
1880been added to the storage layer and allows a package to be read from supported
1881platform storage. A tool to create Firmware Image Packages is also provided
1882and described below.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001883
1884Firmware Image Package layout
1885~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1886
1887The FIP layout consists of a table of contents (ToC) followed by payload data.
1888The ToC itself has a header followed by one or more table entries. The ToC is
Jett Zhou75566102017-11-24 16:03:58 +08001889terminated by an end marker entry, and since the size of the ToC is 0 bytes,
1890the offset equals the total size of the FIP file. All ToC entries describe some
1891payload data that has been appended to the end of the binary package. With the
1892information provided in the ToC entry the corresponding payload data can be
1893retrieved.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001894
1895::
1896
1897 ------------------
1898 | ToC Header |
1899 |----------------|
1900 | ToC Entry 0 |
1901 |----------------|
1902 | ToC Entry 1 |
1903 |----------------|
1904 | ToC End Marker |
1905 |----------------|
1906 | |
1907 | Data 0 |
1908 | |
1909 |----------------|
1910 | |
1911 | Data 1 |
1912 | |
1913 ------------------
1914
1915The ToC header and entry formats are described in the header file
1916``include/tools_share/firmware_image_package.h``. This file is used by both the
Dan Handley610e7e12018-03-01 18:44:00 +00001917tool and TF-A.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001918
1919The ToC header has the following fields:
1920
1921::
1922
1923 `name`: The name of the ToC. This is currently used to validate the header.
1924 `serial_number`: A non-zero number provided by the creation tool
1925 `flags`: Flags associated with this data.
1926 Bits 0-31: Reserved
1927 Bits 32-47: Platform defined
1928 Bits 48-63: Reserved
1929
1930A ToC entry has the following fields:
1931
1932::
1933
1934 `uuid`: All files are referred to by a pre-defined Universally Unique
1935 IDentifier [UUID] . The UUIDs are defined in
1936 `include/tools_share/firmware_image_package.h`. The platform translates
1937 the requested image name into the corresponding UUID when accessing the
1938 package.
1939 `offset_address`: The offset address at which the corresponding payload data
1940 can be found. The offset is calculated from the ToC base address.
1941 `size`: The size of the corresponding payload data in bytes.
Etienne Carriere7421bf12017-08-23 15:43:33 +02001942 `flags`: Flags associated with this entry. None are yet defined.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001943
1944Firmware Image Package creation tool
1945~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1946
Dan Handley610e7e12018-03-01 18:44:00 +00001947The FIP creation tool can be used to pack specified images into a binary
1948package that can be loaded by TF-A from platform storage. The tool currently
1949only supports packing bootloader images. Additional image definitions can be
1950added to the tool as required.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001951
1952The tool can be found in ``tools/fiptool``.
1953
1954Loading from a Firmware Image Package (FIP)
1955~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1956
1957The Firmware Image Package (FIP) driver can load images from a binary package on
Dan Handley610e7e12018-03-01 18:44:00 +00001958non-volatile platform storage. For the Arm development platforms, this is
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001959currently NOR FLASH.
1960
1961Bootloader images are loaded according to the platform policy as specified by
Dan Handley610e7e12018-03-01 18:44:00 +00001962the function ``plat_get_image_source()``. For the Arm development platforms, this
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001963means the platform will attempt to load images from a Firmware Image Package
1964located at the start of NOR FLASH0.
1965
Dan Handley610e7e12018-03-01 18:44:00 +00001966The Arm development platforms' policy is to only allow loading of a known set of
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001967images. The platform policy can be modified to allow additional images.
1968
Dan Handley610e7e12018-03-01 18:44:00 +00001969Use of coherent memory in TF-A
1970------------------------------
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001971
1972There might be loss of coherency when physical memory with mismatched
1973shareability, cacheability and memory attributes is accessed by multiple CPUs
Dan Handley610e7e12018-03-01 18:44:00 +00001974(refer to section B2.9 of `Arm ARM`_ for more details). This possibility occurs
1975in TF-A during power up/down sequences when coherency, MMU and caches are
1976turned on/off incrementally.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001977
Dan Handley610e7e12018-03-01 18:44:00 +00001978TF-A defines coherent memory as a region of memory with Device nGnRE attributes
1979in the translation tables. The translation granule size in TF-A is 4KB. This
1980is the smallest possible size of the coherent memory region.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001981
1982By default, all data structures which are susceptible to accesses with
1983mismatched attributes from various CPUs are allocated in a coherent memory
1984region (refer to section 2.1 of `Porting Guide`_). The coherent memory region
1985accesses are Outer Shareable, non-cacheable and they can be accessed
1986with the Device nGnRE attributes when the MMU is turned on. Hence, at the
Dan Handley610e7e12018-03-01 18:44:00 +00001987expense of at least an extra page of memory, TF-A is able to work around
1988coherency issues due to mismatched memory attributes.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001989
1990The alternative to the above approach is to allocate the susceptible data
1991structures in Normal WriteBack WriteAllocate Inner shareable memory. This
1992approach requires the data structures to be designed so that it is possible to
1993work around the issue of mismatched memory attributes by performing software
1994cache maintenance on them.
1995
Dan Handley610e7e12018-03-01 18:44:00 +00001996Disabling the use of coherent memory in TF-A
1997~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001998
1999It might be desirable to avoid the cost of allocating coherent memory on
Dan Handley610e7e12018-03-01 18:44:00 +00002000platforms which are memory constrained. TF-A enables inclusion of coherent
2001memory in firmware images through the build flag ``USE_COHERENT_MEM``.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002002This flag is enabled by default. It can be disabled to choose the second
2003approach described above.
2004
2005The below sections analyze the data structures allocated in the coherent memory
2006region and the changes required to allocate them in normal memory.
2007
2008Coherent memory usage in PSCI implementation
2009~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2010
2011The ``psci_non_cpu_pd_nodes`` data structure stores the platform's power domain
2012tree information for state management of power domains. By default, this data
Dan Handley610e7e12018-03-01 18:44:00 +00002013structure is allocated in the coherent memory region in TF-A because it can be
Paul Beesley1fbc97b2019-01-11 18:26:51 +00002014accessed by multiple CPUs, either with caches enabled or disabled.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002015
2016.. code:: c
2017
2018 typedef struct non_cpu_pwr_domain_node {
2019 /*
2020 * Index of the first CPU power domain node level 0 which has this node
2021 * as its parent.
2022 */
2023 unsigned int cpu_start_idx;
2024
2025 /*
2026 * Number of CPU power domains which are siblings of the domain indexed
2027 * by 'cpu_start_idx' i.e. all the domains in the range 'cpu_start_idx
2028 * -> cpu_start_idx + ncpus' have this node as their parent.
2029 */
2030 unsigned int ncpus;
2031
2032 /*
2033 * Index of the parent power domain node.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002034 */
2035 unsigned int parent_node;
2036
2037 plat_local_state_t local_state;
2038
2039 unsigned char level;
2040
2041 /* For indexing the psci_lock array*/
2042 unsigned char lock_index;
2043 } non_cpu_pd_node_t;
2044
2045In order to move this data structure to normal memory, the use of each of its
2046fields must be analyzed. Fields like ``cpu_start_idx``, ``ncpus``, ``parent_node``
2047``level`` and ``lock_index`` are only written once during cold boot. Hence removing
2048them from coherent memory involves only doing a clean and invalidate of the
2049cache lines after these fields are written.
2050
2051The field ``local_state`` can be concurrently accessed by multiple CPUs in
2052different cache states. A Lamport's Bakery lock ``psci_locks`` is used to ensure
Paul Beesley1fbc97b2019-01-11 18:26:51 +00002053mutual exclusion to this field and a clean and invalidate is needed after it
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002054is written.
2055
2056Bakery lock data
2057~~~~~~~~~~~~~~~~
2058
2059The bakery lock data structure ``bakery_lock_t`` is allocated in coherent memory
2060and is accessed by multiple CPUs with mismatched attributes. ``bakery_lock_t`` is
2061defined as follows:
2062
2063.. code:: c
2064
2065 typedef struct bakery_lock {
2066 /*
2067 * The lock_data is a bit-field of 2 members:
2068 * Bit[0] : choosing. This field is set when the CPU is
2069 * choosing its bakery number.
2070 * Bits[1 - 15] : number. This is the bakery number allocated.
2071 */
2072 volatile uint16_t lock_data[BAKERY_LOCK_MAX_CPUS];
2073 } bakery_lock_t;
2074
2075It is a characteristic of Lamport's Bakery algorithm that the volatile per-CPU
2076fields can be read by all CPUs but only written to by the owning CPU.
2077
2078Depending upon the data cache line size, the per-CPU fields of the
2079``bakery_lock_t`` structure for multiple CPUs may exist on a single cache line.
2080These per-CPU fields can be read and written during lock contention by multiple
2081CPUs with mismatched memory attributes. Since these fields are a part of the
2082lock implementation, they do not have access to any other locking primitive to
2083safeguard against the resulting coherency issues. As a result, simple software
2084cache maintenance is not enough to allocate them in coherent memory. Consider
2085the following example.
2086
2087CPU0 updates its per-CPU field with data cache enabled. This write updates a
2088local cache line which contains a copy of the fields for other CPUs as well. Now
2089CPU1 updates its per-CPU field of the ``bakery_lock_t`` structure with data cache
2090disabled. CPU1 then issues a DCIVAC operation to invalidate any stale copies of
2091its field in any other cache line in the system. This operation will invalidate
2092the update made by CPU0 as well.
2093
2094To use bakery locks when ``USE_COHERENT_MEM`` is disabled, the lock data structure
2095has been redesigned. The changes utilise the characteristic of Lamport's Bakery
Sandrine Bailleux15530dd2019-02-08 15:26:36 +01002096algorithm mentioned earlier. The bakery_lock structure only allocates the memory
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002097for a single CPU. The macro ``DEFINE_BAKERY_LOCK`` allocates all the bakery locks
2098needed for a CPU into a section ``bakery_lock``. The linker allocates the memory
Sandrine Bailleux15530dd2019-02-08 15:26:36 +01002099for other cores by using the total size allocated for the bakery_lock section
2100and multiplying it with (PLATFORM_CORE_COUNT - 1). This enables software to
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002101perform software cache maintenance on the lock data structure without running
2102into coherency issues associated with mismatched attributes.
2103
2104The bakery lock data structure ``bakery_info_t`` is defined for use when
2105``USE_COHERENT_MEM`` is disabled as follows:
2106
2107.. code:: c
2108
2109 typedef struct bakery_info {
2110 /*
2111 * The lock_data is a bit-field of 2 members:
2112 * Bit[0] : choosing. This field is set when the CPU is
2113 * choosing its bakery number.
2114 * Bits[1 - 15] : number. This is the bakery number allocated.
2115 */
2116 volatile uint16_t lock_data;
2117 } bakery_info_t;
2118
2119The ``bakery_info_t`` represents a single per-CPU field of one lock and
2120the combination of corresponding ``bakery_info_t`` structures for all CPUs in the
2121system represents the complete bakery lock. The view in memory for a system
2122with n bakery locks are:
2123
2124::
2125
2126 bakery_lock section start
2127 |----------------|
2128 | `bakery_info_t`| <-- Lock_0 per-CPU field
2129 | Lock_0 | for CPU0
2130 |----------------|
2131 | `bakery_info_t`| <-- Lock_1 per-CPU field
2132 | Lock_1 | for CPU0
2133 |----------------|
2134 | .... |
2135 |----------------|
2136 | `bakery_info_t`| <-- Lock_N per-CPU field
2137 | Lock_N | for CPU0
2138 ------------------
2139 | XXXXX |
2140 | Padding to |
2141 | next Cache WB | <--- Calculate PERCPU_BAKERY_LOCK_SIZE, allocate
2142 | Granule | continuous memory for remaining CPUs.
2143 ------------------
2144 | `bakery_info_t`| <-- Lock_0 per-CPU field
2145 | Lock_0 | for CPU1
2146 |----------------|
2147 | `bakery_info_t`| <-- Lock_1 per-CPU field
2148 | Lock_1 | for CPU1
2149 |----------------|
2150 | .... |
2151 |----------------|
2152 | `bakery_info_t`| <-- Lock_N per-CPU field
2153 | Lock_N | for CPU1
2154 ------------------
2155 | XXXXX |
2156 | Padding to |
2157 | next Cache WB |
2158 | Granule |
2159 ------------------
2160
2161Consider a system of 2 CPUs with 'N' bakery locks as shown above. For an
Sandrine Bailleux15530dd2019-02-08 15:26:36 +01002162operation on Lock_N, the corresponding ``bakery_info_t`` in both CPU0 and CPU1
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002163``bakery_lock`` section need to be fetched and appropriate cache operations need
2164to be performed for each access.
2165
Dan Handley610e7e12018-03-01 18:44:00 +00002166On Arm Platforms, bakery locks are used in psci (``psci_locks``) and power controller
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002167driver (``arm_lock``).
2168
2169Non Functional Impact of removing coherent memory
2170~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2171
2172Removal of the coherent memory region leads to the additional software overhead
2173of performing cache maintenance for the affected data structures. However, since
2174the memory where the data structures are allocated is cacheable, the overhead is
2175mostly mitigated by an increase in performance.
2176
2177There is however a performance impact for bakery locks, due to:
2178
2179- Additional cache maintenance operations, and
2180- Multiple cache line reads for each lock operation, since the bakery locks
2181 for each CPU are distributed across different cache lines.
2182
2183The implementation has been optimized to minimize this additional overhead.
2184Measurements indicate that when bakery locks are allocated in Normal memory, the
2185minimum latency of acquiring a lock is on an average 3-4 micro seconds whereas
2186in Device memory the same is 2 micro seconds. The measurements were done on the
Dan Handley610e7e12018-03-01 18:44:00 +00002187Juno Arm development platform.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002188
2189As mentioned earlier, almost a page of memory can be saved by disabling
2190``USE_COHERENT_MEM``. Each platform needs to consider these trade-offs to decide
2191whether coherent memory should be used. If a platform disables
2192``USE_COHERENT_MEM`` and needs to use bakery locks in the porting layer, it can
2193optionally define macro ``PLAT_PERCPU_BAKERY_LOCK_SIZE`` (see the
2194`Porting Guide`_). Refer to the reference platform code for examples.
2195
2196Isolating code and read-only data on separate memory pages
2197----------------------------------------------------------
2198
Dan Handley610e7e12018-03-01 18:44:00 +00002199In the Armv8-A VMSA, translation table entries include fields that define the
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002200properties of the target memory region, such as its access permissions. The
2201smallest unit of memory that can be addressed by a translation table entry is
2202a memory page. Therefore, if software needs to set different permissions on two
2203memory regions then it needs to map them using different memory pages.
2204
2205The default memory layout for each BL image is as follows:
2206
2207::
2208
2209 | ... |
2210 +-------------------+
2211 | Read-write data |
2212 +-------------------+ Page boundary
2213 | <Padding> |
2214 +-------------------+
2215 | Exception vectors |
2216 +-------------------+ 2 KB boundary
2217 | <Padding> |
2218 +-------------------+
2219 | Read-only data |
2220 +-------------------+
2221 | Code |
2222 +-------------------+ BLx_BASE
2223
2224Note: The 2KB alignment for the exception vectors is an architectural
2225requirement.
2226
2227The read-write data start on a new memory page so that they can be mapped with
2228read-write permissions, whereas the code and read-only data below are configured
2229as read-only.
2230
2231However, the read-only data are not aligned on a page boundary. They are
2232contiguous to the code. Therefore, the end of the code section and the beginning
2233of the read-only data one might share a memory page. This forces both to be
2234mapped with the same memory attributes. As the code needs to be executable, this
2235means that the read-only data stored on the same memory page as the code are
2236executable as well. This could potentially be exploited as part of a security
2237attack.
2238
2239TF provides the build flag ``SEPARATE_CODE_AND_RODATA`` to isolate the code and
2240read-only data on separate memory pages. This in turn allows independent control
2241of the access permissions for the code and read-only data. In this case,
2242platform code gets a finer-grained view of the image layout and can
2243appropriately map the code region as executable and the read-only data as
2244execute-never.
2245
2246This has an impact on memory footprint, as padding bytes need to be introduced
Paul Beesley1fbc97b2019-01-11 18:26:51 +00002247between the code and read-only data to ensure the segregation of the two. To
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002248limit the memory cost, this flag also changes the memory layout such that the
2249code and exception vectors are now contiguous, like so:
2250
2251::
2252
2253 | ... |
2254 +-------------------+
2255 | Read-write data |
2256 +-------------------+ Page boundary
2257 | <Padding> |
2258 +-------------------+
2259 | Read-only data |
2260 +-------------------+ Page boundary
2261 | <Padding> |
2262 +-------------------+
2263 | Exception vectors |
2264 +-------------------+ 2 KB boundary
2265 | <Padding> |
2266 +-------------------+
2267 | Code |
2268 +-------------------+ BLx_BASE
2269
2270With this more condensed memory layout, the separation of read-only data will
2271add zero or one page to the memory footprint of each BL image. Each platform
2272should consider the trade-off between memory footprint and security.
2273
Dan Handley610e7e12018-03-01 18:44:00 +00002274This build flag is disabled by default, minimising memory footprint. On Arm
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002275platforms, it is enabled.
2276
Jeenu Viswambharane3f22002017-09-22 08:32:10 +01002277Publish and Subscribe Framework
2278-------------------------------
2279
2280The Publish and Subscribe Framework allows EL3 components to define and publish
2281events, to which other EL3 components can subscribe.
2282
2283The following macros are provided by the framework:
2284
2285- ``REGISTER_PUBSUB_EVENT(event)``: Defines an event, and takes one argument,
2286 the event name, which must be a valid C identifier. All calls to
2287 ``REGISTER_PUBSUB_EVENT`` macro must be placed in the file
2288 ``pubsub_events.h``.
2289
2290- ``PUBLISH_EVENT_ARG(event, arg)``: Publishes a defined event, by iterating
2291 subscribed handlers and calling them in turn. The handlers will be passed the
2292 parameter ``arg``. The expected use-case is to broadcast an event.
2293
2294- ``PUBLISH_EVENT(event)``: Like ``PUBLISH_EVENT_ARG``, except that the value
2295 ``NULL`` is passed to subscribed handlers.
2296
2297- ``SUBSCRIBE_TO_EVENT(event, handler)``: Registers the ``handler`` to
2298 subscribe to ``event``. The handler will be executed whenever the ``event``
2299 is published.
2300
2301- ``for_each_subscriber(event, subscriber)``: Iterates through all handlers
2302 subscribed for ``event``. ``subscriber`` must be a local variable of type
2303 ``pubsub_cb_t *``, and will point to each subscribed handler in turn during
2304 iteration. This macro can be used for those patterns that none of the
2305 ``PUBLISH_EVENT_*()`` macros cover.
2306
2307Publishing an event that wasn't defined using ``REGISTER_PUBSUB_EVENT`` will
2308result in build error. Subscribing to an undefined event however won't.
2309
2310Subscribed handlers must be of type ``pubsub_cb_t``, with following function
2311signature:
2312
2313::
2314
2315 typedef void* (*pubsub_cb_t)(const void *arg);
2316
2317There may be arbitrary number of handlers registered to the same event. The
2318order in which subscribed handlers are notified when that event is published is
2319not defined. Subscribed handlers may be executed in any order; handlers should
2320not assume any relative ordering amongst them.
2321
2322Publishing an event on a PE will result in subscribed handlers executing on that
2323PE only; it won't cause handlers to execute on a different PE.
2324
2325Note that publishing an event on a PE blocks until all the subscribed handlers
2326finish executing on the PE.
2327
Dan Handley610e7e12018-03-01 18:44:00 +00002328TF-A generic code publishes and subscribes to some events within. Platform
2329ports are discouraged from subscribing to them. These events may be withdrawn,
2330renamed, or have their semantics altered in the future. Platforms may however
2331register, publish, and subscribe to platform-specific events.
Dimitris Papastamosa7921b92017-10-13 15:27:58 +01002332
Jeenu Viswambharane3f22002017-09-22 08:32:10 +01002333Publish and Subscribe Example
2334~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2335
2336A publisher that wants to publish event ``foo`` would:
2337
2338- Define the event ``foo`` in the ``pubsub_events.h``.
2339
2340 ::
2341
2342 REGISTER_PUBSUB_EVENT(foo);
2343
2344- Depending on the nature of event, use one of ``PUBLISH_EVENT_*()`` macros to
2345 publish the event at the appropriate path and time of execution.
2346
2347A subscriber that wants to subscribe to event ``foo`` published above would
2348implement:
2349
Sandrine Bailleuxf5a91002019-02-08 10:50:28 +01002350.. code:: c
Jeenu Viswambharane3f22002017-09-22 08:32:10 +01002351
Sandrine Bailleuxf5a91002019-02-08 10:50:28 +01002352 void *foo_handler(const void *arg)
2353 {
2354 void *result;
Jeenu Viswambharane3f22002017-09-22 08:32:10 +01002355
Sandrine Bailleuxf5a91002019-02-08 10:50:28 +01002356 /* Do handling ... */
Jeenu Viswambharane3f22002017-09-22 08:32:10 +01002357
Sandrine Bailleuxf5a91002019-02-08 10:50:28 +01002358 return result;
2359 }
Jeenu Viswambharane3f22002017-09-22 08:32:10 +01002360
Sandrine Bailleuxf5a91002019-02-08 10:50:28 +01002361 SUBSCRIBE_TO_EVENT(foo, foo_handler);
Jeenu Viswambharane3f22002017-09-22 08:32:10 +01002362
Daniel Boulby468f0d72018-09-18 11:45:51 +01002363
2364Reclaiming the BL31 initialization code
2365~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2366
2367A significant amount of the code used for the initialization of BL31 is never
2368needed again after boot time. In order to reduce the runtime memory
2369footprint, the memory used for this code can be reclaimed after initialization
2370has finished and be used for runtime data.
2371
2372The build option ``RECLAIM_INIT_CODE`` can be set to mark this boot time code
2373with a ``.text.init.*`` attribute which can be filtered and placed suitably
Paul Beesley1fbc97b2019-01-11 18:26:51 +00002374within the BL image for later reclamation by the platform. The platform can
2375specify the filter and the memory region for this init section in BL31 via the
Daniel Boulby468f0d72018-09-18 11:45:51 +01002376plat.ld.S linker script. For example, on the FVP, this section is placed
2377overlapping the secondary CPU stacks so that after the cold boot is done, this
2378memory can be reclaimed for the stacks. The init memory section is initially
Paul Beesley1fbc97b2019-01-11 18:26:51 +00002379mapped with ``RO``, ``EXECUTE`` attributes. After BL31 initialization has
Daniel Boulby468f0d72018-09-18 11:45:51 +01002380completed, the FVP changes the attributes of this section to ``RW``,
2381``EXECUTE_NEVER`` allowing it to be used for runtime data. The memory attributes
2382are changed within the ``bl31_plat_runtime_setup`` platform hook. The init
2383section section can be reclaimed for any data which is accessed after cold
2384boot initialization and it is upto the platform to make the decision.
2385
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002386Performance Measurement Framework
2387---------------------------------
2388
2389The Performance Measurement Framework (PMF) facilitates collection of
Dan Handley610e7e12018-03-01 18:44:00 +00002390timestamps by registered services and provides interfaces to retrieve them
2391from within TF-A. A platform can choose to expose appropriate SMCs to
2392retrieve these collected timestamps.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002393
2394By default, the global physical counter is used for the timestamp
2395value and is read via ``CNTPCT_EL0``. The framework allows to retrieve
2396timestamps captured by other CPUs.
2397
2398Timestamp identifier format
2399~~~~~~~~~~~~~~~~~~~~~~~~~~~
2400
2401A PMF timestamp is uniquely identified across the system via the
2402timestamp ID or ``tid``. The ``tid`` is composed as follows:
2403
2404::
2405
2406 Bits 0-7: The local timestamp identifier.
2407 Bits 8-9: Reserved.
2408 Bits 10-15: The service identifier.
2409 Bits 16-31: Reserved.
2410
2411#. The service identifier. Each PMF service is identified by a
2412 service name and a service identifier. Both the service name and
2413 identifier are unique within the system as a whole.
2414
2415#. The local timestamp identifier. This identifier is unique within a given
2416 service.
2417
2418Registering a PMF service
2419~~~~~~~~~~~~~~~~~~~~~~~~~
2420
2421To register a PMF service, the ``PMF_REGISTER_SERVICE()`` macro from ``pmf.h``
2422is used. The arguments required are the service name, the service ID,
2423the total number of local timestamps to be captured and a set of flags.
2424
2425The ``flags`` field can be specified as a bitwise-OR of the following values:
2426
2427::
2428
2429 PMF_STORE_ENABLE: The timestamp is stored in memory for later retrieval.
2430 PMF_DUMP_ENABLE: The timestamp is dumped on the serial console.
2431
2432The ``PMF_REGISTER_SERVICE()`` reserves memory to store captured
2433timestamps in a PMF specific linker section at build time.
2434Additionally, it defines necessary functions to capture and
2435retrieve a particular timestamp for the given service at runtime.
2436
Dan Handley610e7e12018-03-01 18:44:00 +00002437The macro ``PMF_REGISTER_SERVICE()`` only enables capturing PMF timestamps
2438from within TF-A. In order to retrieve timestamps from outside of TF-A, the
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002439``PMF_REGISTER_SERVICE_SMC()`` macro must be used instead. This macro
2440accepts the same set of arguments as the ``PMF_REGISTER_SERVICE()``
2441macro but additionally supports retrieving timestamps using SMCs.
2442
2443Capturing a timestamp
2444~~~~~~~~~~~~~~~~~~~~~
2445
2446PMF timestamps are stored in a per-service timestamp region. On a
2447system with multiple CPUs, each timestamp is captured and stored
2448in a per-CPU cache line aligned memory region.
2449
2450Having registered the service, the ``PMF_CAPTURE_TIMESTAMP()`` macro can be
2451used to capture a timestamp at the location where it is used. The macro
2452takes the service name, a local timestamp identifier and a flag as arguments.
2453
2454The ``flags`` field argument can be zero, or ``PMF_CACHE_MAINT`` which
2455instructs PMF to do cache maintenance following the capture. Cache
2456maintenance is required if any of the service's timestamps are captured
2457with data cache disabled.
2458
2459To capture a timestamp in assembly code, the caller should use
2460``pmf_calc_timestamp_addr`` macro (defined in ``pmf_asm_macros.S``) to
2461calculate the address of where the timestamp would be stored. The
2462caller should then read ``CNTPCT_EL0`` register to obtain the timestamp
2463and store it at the determined address for later retrieval.
2464
2465Retrieving a timestamp
2466~~~~~~~~~~~~~~~~~~~~~~
2467
Dan Handley610e7e12018-03-01 18:44:00 +00002468From within TF-A, timestamps for individual CPUs can be retrieved using either
2469``PMF_GET_TIMESTAMP_BY_MPIDR()`` or ``PMF_GET_TIMESTAMP_BY_INDEX()`` macros.
2470These macros accept the CPU's MPIDR value, or its ordinal position
2471respectively.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002472
Dan Handley610e7e12018-03-01 18:44:00 +00002473From outside TF-A, timestamps for individual CPUs can be retrieved by calling
2474into ``pmf_smc_handler()``.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002475
2476.. code:: c
2477
2478 Interface : pmf_smc_handler()
2479 Argument : unsigned int smc_fid, u_register_t x1,
2480 u_register_t x2, u_register_t x3,
2481 u_register_t x4, void *cookie,
2482 void *handle, u_register_t flags
2483 Return : uintptr_t
2484
2485 smc_fid: Holds the SMC identifier which is either `PMF_SMC_GET_TIMESTAMP_32`
2486 when the caller of the SMC is running in AArch32 mode
2487 or `PMF_SMC_GET_TIMESTAMP_64` when the caller is running in AArch64 mode.
2488 x1: Timestamp identifier.
2489 x2: The `mpidr` of the CPU for which the timestamp has to be retrieved.
2490 This can be the `mpidr` of a different core to the one initiating
2491 the SMC. In that case, service specific cache maintenance may be
2492 required to ensure the updated copy of the timestamp is returned.
2493 x3: A flags value that is either 0 or `PMF_CACHE_MAINT`. If
2494 `PMF_CACHE_MAINT` is passed, then the PMF code will perform a
2495 cache invalidate before reading the timestamp. This ensures
2496 an updated copy is returned.
2497
2498The remaining arguments, ``x4``, ``cookie``, ``handle`` and ``flags`` are unused
2499in this implementation.
2500
2501PMF code structure
2502~~~~~~~~~~~~~~~~~~
2503
2504#. ``pmf_main.c`` consists of core functions that implement service registration,
2505 initialization, storing, dumping and retrieving timestamps.
2506
2507#. ``pmf_smc.c`` contains the SMC handling for registered PMF services.
2508
2509#. ``pmf.h`` contains the public interface to Performance Measurement Framework.
2510
2511#. ``pmf_asm_macros.S`` consists of macros to facilitate capturing timestamps in
2512 assembly code.
2513
2514#. ``pmf_helpers.h`` is an internal header used by ``pmf.h``.
2515
Dan Handley610e7e12018-03-01 18:44:00 +00002516Armv8-A Architecture Extensions
2517-------------------------------
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002518
Dan Handley610e7e12018-03-01 18:44:00 +00002519TF-A makes use of Armv8-A Architecture Extensions where applicable. This
2520section lists the usage of Architecture Extensions, and build flags
2521controlling them.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002522
2523In general, and unless individually mentioned, the build options
Alexei Fedorovb567e5d2019-03-11 16:51:47 +00002524``ARM_ARCH_MAJOR`` and ``ARM_ARCH_MINOR`` select the Architecture Extension to
Dan Handley610e7e12018-03-01 18:44:00 +00002525target when building TF-A. Subsequent Arm Architecture Extensions are backward
2526compatible with previous versions.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002527
2528The build system only requires that ``ARM_ARCH_MAJOR`` and ``ARM_ARCH_MINOR`` have a
2529valid numeric value. These build options only control whether or not
Dan Handley610e7e12018-03-01 18:44:00 +00002530Architecture Extension-specific code is included in the build. Otherwise, TF-A
2531targets the base Armv8.0-A architecture; i.e. as if ``ARM_ARCH_MAJOR`` == 8
2532and ``ARM_ARCH_MINOR`` == 0, which are also their respective default values.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002533
2534See also the *Summary of build options* in `User Guide`_.
2535
2536For details on the Architecture Extension and available features, please refer
2537to the respective Architecture Extension Supplement.
2538
Dan Handley610e7e12018-03-01 18:44:00 +00002539Armv8.1-A
2540~~~~~~~~~
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002541
2542This Architecture Extension is targeted when ``ARM_ARCH_MAJOR`` >= 8, or when
2543``ARM_ARCH_MAJOR`` == 8 and ``ARM_ARCH_MINOR`` >= 1.
2544
2545- The Compare and Swap instruction is used to implement spinlocks. Otherwise,
2546 the load-/store-exclusive instruction pair is used.
2547
Dan Handley610e7e12018-03-01 18:44:00 +00002548Armv8.2-A
2549~~~~~~~~~
Isla Mitchellc4a1a072017-08-07 11:20:13 +01002550
Antonio Nino Diaz633703a2019-02-19 13:14:06 +00002551- The presence of ARMv8.2-TTCNP is detected at runtime. When it is present, the
2552 Common not Private (TTBRn_ELx.CnP) bit is enabled to indicate that multiple
Sandrine Bailleuxfee6e262018-01-29 14:48:15 +01002553 Processing Elements in the same Inner Shareable domain use the same
2554 translation table entries for a given stage of translation for a particular
2555 translation regime.
Isla Mitchellc4a1a072017-08-07 11:20:13 +01002556
Jeenu Viswambharancbad6612018-08-15 14:29:29 +01002557Armv8.3-A
2558~~~~~~~~~
2559
Antonio Nino Diaz594811b2019-01-31 11:58:00 +00002560- Pointer authentication features of Armv8.3-A are unconditionally enabled in
2561 the Non-secure world so that lower ELs are allowed to use them without
2562 causing a trap to EL3.
2563
2564 In order to enable the Secure world to use it, ``CTX_INCLUDE_PAUTH_REGS``
2565 must be set to 1. This will add all pointer authentication system registers
2566 to the context that is saved when doing a world switch.
Jeenu Viswambharancbad6612018-08-15 14:29:29 +01002567
Alexei Fedorov2831d582019-03-13 11:05:07 +00002568 The TF-A itself has support for pointer authentication at runtime
Antonio Nino Diaz25cda672019-02-19 11:53:51 +00002569 that can be enabled by setting both options ``ENABLE_PAUTH`` and
2570 ``CTX_INCLUDE_PAUTH_REGS`` to 1. This enables pointer authentication in BL1,
2571 BL2, BL31, and the TSP if it is used.
2572
Alexei Fedorov2831d582019-03-13 11:05:07 +00002573 These options are experimental features.
2574
2575 Note that Pointer Authentication is enabled for Non-secure world irrespective
2576 of the value of these build flags if the CPU supports it.
2577
Alexei Fedorovb567e5d2019-03-11 16:51:47 +00002578 If ``ARM_ARCH_MAJOR == 8`` and ``ARM_ARCH_MINOR >= 3`` the code footprint of
2579 enabling PAuth is lower because the compiler will use the optimized
2580 PAuth instructions rather than the backwards-compatible ones.
2581
Dan Handley610e7e12018-03-01 18:44:00 +00002582Armv7-A
2583~~~~~~~
Etienne Carriere1374fcb2017-11-08 13:48:40 +01002584
2585This Architecture Extension is targeted when ``ARM_ARCH_MAJOR`` == 7.
2586
Dan Handley610e7e12018-03-01 18:44:00 +00002587There are several Armv7-A extensions available. Obviously the TrustZone
2588extension is mandatory to support the TF-A bootloader and runtime services.
Etienne Carriere1374fcb2017-11-08 13:48:40 +01002589
Dan Handley610e7e12018-03-01 18:44:00 +00002590Platform implementing an Armv7-A system can to define from its target
Etienne Carriere1374fcb2017-11-08 13:48:40 +01002591Cortex-A architecture through ``ARM_CORTEX_A<X> = yes`` in their
Paul Beesley1fbc97b2019-01-11 18:26:51 +00002592``platform.mk`` script. For example ``ARM_CORTEX_A15=yes`` for a
Etienne Carriere1374fcb2017-11-08 13:48:40 +01002593Cortex-A15 target.
2594
2595Platform can also set ``ARM_WITH_NEON=yes`` to enable neon support.
2596Note that using neon at runtime has constraints on non secure wolrd context.
Dan Handley610e7e12018-03-01 18:44:00 +00002597TF-A does not yet provide VFP context management.
Etienne Carriere1374fcb2017-11-08 13:48:40 +01002598
2599Directive ``ARM_CORTEX_A<x>`` and ``ARM_WITH_NEON`` are used to set
2600the toolchain target architecture directive.
2601
2602Platform may choose to not define straight the toolchain target architecture
2603directive by defining ``MARCH32_DIRECTIVE``.
2604I.e:
2605
2606::
2607
2608 MARCH32_DIRECTIVE := -mach=armv7-a
2609
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002610Code Structure
2611--------------
2612
Dan Handley610e7e12018-03-01 18:44:00 +00002613TF-A code is logically divided between the three boot loader stages mentioned
2614in the previous sections. The code is also divided into the following
2615categories (present as directories in the source code):
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002616
2617- **Platform specific.** Choice of architecture specific code depends upon
2618 the platform.
2619- **Common code.** This is platform and architecture agnostic code.
2620- **Library code.** This code comprises of functionality commonly used by all
2621 other code. The PSCI implementation and other EL3 runtime frameworks reside
2622 as Library components.
2623- **Stage specific.** Code specific to a boot stage.
2624- **Drivers.**
2625- **Services.** EL3 runtime services (eg: SPD). Specific SPD services
2626 reside in the ``services/spd`` directory (e.g. ``services/spd/tspd``).
2627
2628Each boot loader stage uses code from one or more of the above mentioned
2629categories. Based upon the above, the code layout looks like this:
2630
2631::
2632
2633 Directory Used by BL1? Used by BL2? Used by BL31?
2634 bl1 Yes No No
2635 bl2 No Yes No
2636 bl31 No No Yes
2637 plat Yes Yes Yes
2638 drivers Yes No Yes
2639 common Yes Yes Yes
2640 lib Yes Yes Yes
2641 services No No Yes
2642
Sandrine Bailleux15530dd2019-02-08 15:26:36 +01002643The build system provides a non configurable build option IMAGE_BLx for each
2644boot loader stage (where x = BL stage). e.g. for BL1 , IMAGE_BL1 will be
Dan Handley610e7e12018-03-01 18:44:00 +00002645defined by the build system. This enables TF-A to compile certain code only
2646for specific boot loader stages
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002647
2648All assembler files have the ``.S`` extension. The linker source files for each
2649boot stage have the extension ``.ld.S``. These are processed by GCC to create the
2650linker scripts which have the extension ``.ld``.
2651
2652FDTs provide a description of the hardware platform and are used by the Linux
2653kernel at boot time. These can be found in the ``fdts`` directory.
2654
2655References
2656----------
2657
Sandrine Bailleux30918422019-04-24 10:41:24 +02002658.. [#] `Trusted Board Boot Requirements CLIENT (TBBR-CLIENT) Armv8-A (ARM DEN0006D)`_
Douglas Raillard30d7b362017-06-28 16:14:55 +01002659.. [#] `Power State Coordination Interface PDD`_
2660.. [#] `SMC Calling Convention PDD`_
Dan Handley610e7e12018-03-01 18:44:00 +00002661.. [#] `TF-A Interrupt Management Design guide`_.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002662
2663--------------
2664
Antonio Nino Diaz633703a2019-02-19 13:14:06 +00002665*Copyright (c) 2013-2019, Arm Limited and Contributors. All rights reserved.*
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002666
2667.. _Reset Design: ./reset-design.rst
2668.. _Porting Guide: ./porting-guide.rst
2669.. _Firmware Update: ./firmware-update.rst
2670.. _PSCI PDD: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf
2671.. _SMC calling convention PDD: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
2672.. _PSCI Library integration guide: ./psci-lib-integration-guide.rst
2673.. _SMCCC: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
2674.. _PSCI: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf
2675.. _Power State Coordination Interface PDD: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf
2676.. _here: ./psci-lib-integration-guide.rst
2677.. _cpu-specific-build-macros.rst: ./cpu-specific-build-macros.rst
2678.. _CPUBM: ./cpu-specific-build-macros.rst
Dan Handley610e7e12018-03-01 18:44:00 +00002679.. _Arm ARM: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0487a.e/index.html
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002680.. _User Guide: ./user-guide.rst
2681.. _SMC Calling Convention PDD: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
Dan Handley610e7e12018-03-01 18:44:00 +00002682.. _TF-A Interrupt Management Design guide: ./interrupt-framework-design.rst
Antonio Nino Diazb5d68092017-05-23 11:49:22 +01002683.. _Xlat_tables design: xlat-tables-lib-v2-design.rst
Jeenu Viswambharancbb40d52017-10-18 14:30:53 +01002684.. _Exception Handling Framework: exception-handling.rst
Sathees Balya17d8eed2019-01-30 15:56:44 +00002685.. _ROMLIB Design: romlib-design.rst
Sandrine Bailleux30918422019-04-24 10:41:24 +02002686.. _Trusted Board Boot Requirements CLIENT (TBBR-CLIENT) Armv8-A (ARM DEN0006D): https://developer.arm.com/docs/den0006/latest/trusted-board-boot-requirements-client-tbbr-client-armv8-a
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002687
2688.. |Image 1| image:: diagrams/rt-svc-descs-layout.png?raw=true