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Douglas Raillardd7c21b72017-06-28 15:23:03 +01001ARM Trusted Firmware Design
2===========================
3
4
5.. section-numbering::
6 :suffix: .
7
8.. contents::
9
10The ARM Trusted Firmware implements a subset of the Trusted Board Boot
Douglas Raillard30d7b362017-06-28 16:14:55 +010011Requirements (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
16The ARM Trusted Firmware also implements the Power State Coordination Interface
Douglas Raillard30d7b362017-06-28 16:14:55 +010017PDD [2]_ as a runtime service. PSCI is the interface from normal world software
Douglas Raillardd7c21b72017-06-28 15:23:03 +010018to firmware implementing power management use-cases (for example, secondary CPU
19boot, hotplug and idle). Normal world software can access ARM Trusted Firmware
20runtime services via the ARM SMC (Secure Monitor Call) instruction. The SMC
Douglas Raillard30d7b362017-06-28 16:14:55 +010021instruction must be used as mandated by the SMC Calling Convention [3]_.
Douglas Raillardd7c21b72017-06-28 15:23:03 +010022
23The ARM Trusted Firmware implements a framework for configuring and managing
24interrupts generated in either security state. The details of the interrupt
25management framework and its design can be found in ARM Trusted Firmware
Douglas Raillard30d7b362017-06-28 16:14:55 +010026Interrupt Management Design guide [4]_.
Douglas Raillardd7c21b72017-06-28 15:23:03 +010027
Antonio Nino Diazb5d68092017-05-23 11:49:22 +010028The ARM Trusted Firmware also implements a library for setting up and managing
29the translation tables. The details of this library can be found in
30`Xlat_tables design`_.
31
Douglas Raillardd7c21b72017-06-28 15:23:03 +010032The ARM Trusted Firmware can be built to support either AArch64 or AArch32
33execution state.
34
35Cold boot
36---------
37
38The cold boot path starts when the platform is physically turned on. If
39``COLD_BOOT_SINGLE_CPU=0``, one of the CPUs released from reset is chosen as the
40primary CPU, and the remaining CPUs are considered secondary CPUs. The primary
41CPU is chosen through platform-specific means. The cold boot path is mainly
42executed by the primary CPU, other than essential CPU initialization executed by
43all CPUs. The secondary CPUs are kept in a safe platform-specific state until
44the primary CPU has performed enough initialization to boot them.
45
46Refer to the `Reset Design`_ for more information on the effect of the
47``COLD_BOOT_SINGLE_CPU`` platform build option.
48
49The cold boot path in this implementation of the ARM Trusted Firmware,
50depends on the execution state.
51For AArch64, it is divided into five steps (in order of execution):
52
53- Boot Loader stage 1 (BL1) *AP Trusted ROM*
54- Boot Loader stage 2 (BL2) *Trusted Boot Firmware*
55- Boot Loader stage 3-1 (BL31) *EL3 Runtime Software*
56- Boot Loader stage 3-2 (BL32) *Secure-EL1 Payload* (optional)
57- Boot Loader stage 3-3 (BL33) *Non-trusted Firmware*
58
59For AArch32, it is divided into four steps (in order of execution):
60
61- Boot Loader stage 1 (BL1) *AP Trusted ROM*
62- Boot Loader stage 2 (BL2) *Trusted Boot Firmware*
63- Boot Loader stage 3-2 (BL32) *EL3 Runtime Software*
64- Boot Loader stage 3-3 (BL33) *Non-trusted Firmware*
65
66ARM development platforms (Fixed Virtual Platforms (FVPs) and Juno) implement a
67combination of the following types of memory regions. Each bootloader stage uses
68one or more of these memory regions.
69
70- Regions accessible from both non-secure and secure states. For example,
71 non-trusted SRAM, ROM and DRAM.
72- Regions accessible from only the secure state. For example, trusted SRAM and
73 ROM. The FVPs also implement the trusted DRAM which is statically
74 configured. Additionally, the Base FVPs and Juno development platform
75 configure the TrustZone Controller (TZC) to create a region in the DRAM
76 which is accessible only from the secure state.
77
78The sections below provide the following details:
79
80- initialization and execution of the first three stages during cold boot
81- specification of the EL3 Runtime Software (BL31 for AArch64 and BL32 for
82 AArch32) entrypoint requirements for use by alternative Trusted Boot
83 Firmware in place of the provided BL1 and BL2
84
85BL1
86~~~
87
88This stage begins execution from the platform's reset vector at EL3. The reset
89address is platform dependent but it is usually located in a Trusted ROM area.
90The BL1 data section is copied to trusted SRAM at runtime.
91
92On the ARM development platforms, BL1 code starts execution from the reset
93vector defined by the constant ``BL1_RO_BASE``. The BL1 data section is copied
94to the top of trusted SRAM as defined by the constant ``BL1_RW_BASE``.
95
96The functionality implemented by this stage is as follows.
97
98Determination of boot path
99^^^^^^^^^^^^^^^^^^^^^^^^^^
100
101Whenever a CPU is released from reset, BL1 needs to distinguish between a warm
102boot and a cold boot. This is done using platform-specific mechanisms (see the
103``plat_get_my_entrypoint()`` function in the `Porting Guide`_). In the case of a
104warm boot, a CPU is expected to continue execution from a separate
105entrypoint. In the case of a cold boot, the secondary CPUs are placed in a safe
106platform-specific state (see the ``plat_secondary_cold_boot_setup()`` function in
107the `Porting Guide`_) while the primary CPU executes the remaining cold boot path
108as described in the following sections.
109
110This step only applies when ``PROGRAMMABLE_RESET_ADDRESS=0``. Refer to the
111`Reset Design`_ for more information on the effect of the
112``PROGRAMMABLE_RESET_ADDRESS`` platform build option.
113
114Architectural initialization
115^^^^^^^^^^^^^^^^^^^^^^^^^^^^
116
117BL1 performs minimal architectural initialization as follows.
118
119- Exception vectors
120
121 BL1 sets up simple exception vectors for both synchronous and asynchronous
122 exceptions. The default behavior upon receiving an exception is to populate
123 a status code in the general purpose register ``X0/R0`` and call the
124 ``plat_report_exception()`` function (see the `Porting Guide`_). The status
125 code is one of:
126
127 For AArch64:
128
129 ::
130
131 0x0 : Synchronous exception from Current EL with SP_EL0
132 0x1 : IRQ exception from Current EL with SP_EL0
133 0x2 : FIQ exception from Current EL with SP_EL0
134 0x3 : System Error exception from Current EL with SP_EL0
135 0x4 : Synchronous exception from Current EL with SP_ELx
136 0x5 : IRQ exception from Current EL with SP_ELx
137 0x6 : FIQ exception from Current EL with SP_ELx
138 0x7 : System Error exception from Current EL with SP_ELx
139 0x8 : Synchronous exception from Lower EL using aarch64
140 0x9 : IRQ exception from Lower EL using aarch64
141 0xa : FIQ exception from Lower EL using aarch64
142 0xb : System Error exception from Lower EL using aarch64
143 0xc : Synchronous exception from Lower EL using aarch32
144 0xd : IRQ exception from Lower EL using aarch32
145 0xe : FIQ exception from Lower EL using aarch32
146 0xf : System Error exception from Lower EL using aarch32
147
148 For AArch32:
149
150 ::
151
152 0x10 : User mode
153 0x11 : FIQ mode
154 0x12 : IRQ mode
155 0x13 : SVC mode
156 0x16 : Monitor mode
157 0x17 : Abort mode
158 0x1a : Hypervisor mode
159 0x1b : Undefined mode
160 0x1f : System mode
161
162 The ``plat_report_exception()`` implementation on the ARM FVP port programs
163 the Versatile Express System LED register in the following format to
164 indicate the occurence of an unexpected exception:
165
166 ::
167
168 SYS_LED[0] - Security state (Secure=0/Non-Secure=1)
169 SYS_LED[2:1] - Exception Level (EL3=0x3, EL2=0x2, EL1=0x1, EL0=0x0)
170 For AArch32 it is always 0x0
171 SYS_LED[7:3] - Exception Class (Sync/Async & origin). This is the value
172 of the status code
173
174 A write to the LED register reflects in the System LEDs (S6LED0..7) in the
175 CLCD window of the FVP.
176
177 BL1 does not expect to receive any exceptions other than the SMC exception.
178 For the latter, BL1 installs a simple stub. The stub expects to receive a
179 limited set of SMC types (determined by their function IDs in the general
180 purpose register ``X0/R0``):
181
182 - ``BL1_SMC_RUN_IMAGE``: This SMC is raised by BL2 to make BL1 pass control
183 to EL3 Runtime Software.
184 - All SMCs listed in section "BL1 SMC Interface" in the `Firmware Update`_
185 Design Guide are supported for AArch64 only. These SMCs are currently
186 not supported when BL1 is built for AArch32.
187
188 Any other SMC leads to an assertion failure.
189
190- CPU initialization
191
192 BL1 calls the ``reset_handler()`` function which in turn calls the CPU
193 specific reset handler function (see the section: "CPU specific operations
194 framework").
195
196- Control register setup (for AArch64)
197
198 - ``SCTLR_EL3``. Instruction cache is enabled by setting the ``SCTLR_EL3.I``
199 bit. Alignment and stack alignment checking is enabled by setting the
200 ``SCTLR_EL3.A`` and ``SCTLR_EL3.SA`` bits. Exception endianness is set to
201 little-endian by clearing the ``SCTLR_EL3.EE`` bit.
202
203 - ``SCR_EL3``. The register width of the next lower exception level is set
204 to AArch64 by setting the ``SCR.RW`` bit. The ``SCR.EA`` bit is set to trap
205 both External Aborts and SError Interrupts in EL3. The ``SCR.SIF`` bit is
206 also set to disable instruction fetches from Non-secure memory when in
207 secure state.
208
209 - ``CPTR_EL3``. Accesses to the ``CPACR_EL1`` register from EL1 or EL2, or the
210 ``CPTR_EL2`` register from EL2 are configured to not trap to EL3 by
211 clearing the ``CPTR_EL3.TCPAC`` bit. Access to the trace functionality is
212 configured not to trap to EL3 by clearing the ``CPTR_EL3.TTA`` bit.
213 Instructions that access the registers associated with Floating Point
214 and Advanced SIMD execution are configured to not trap to EL3 by
215 clearing the ``CPTR_EL3.TFP`` bit.
216
217 - ``DAIF``. The SError interrupt is enabled by clearing the SError interrupt
218 mask bit.
219
220 - ``MDCR_EL3``. The trap controls, ``MDCR_EL3.TDOSA``, ``MDCR_EL3.TDA`` and
221 ``MDCR_EL3.TPM``, are set so that accesses to the registers they control
222 do not trap to EL3. AArch64 Secure self-hosted debug is disabled by
223 setting the ``MDCR_EL3.SDD`` bit. Also ``MDCR_EL3.SPD32`` is set to
224 disable AArch32 Secure self-hosted privileged debug from S-EL1.
225
226- Control register setup (for AArch32)
227
228 - ``SCTLR``. Instruction cache is enabled by setting the ``SCTLR.I`` bit.
229 Alignment checking is enabled by setting the ``SCTLR.A`` bit.
230 Exception endianness is set to little-endian by clearing the
231 ``SCTLR.EE`` bit.
232
233 - ``SCR``. The ``SCR.SIF`` bit is set to disable instruction fetches from
234 Non-secure memory when in secure state.
235
236 - ``CPACR``. Allow execution of Advanced SIMD instructions at PL0 and PL1,
237 by clearing the ``CPACR.ASEDIS`` bit. Access to the trace functionality
238 is configured not to trap to undefined mode by clearing the
239 ``CPACR.TRCDIS`` bit.
240
241 - ``NSACR``. Enable non-secure access to Advanced SIMD functionality and
242 system register access to implemented trace registers.
243
244 - ``FPEXC``. Enable access to the Advanced SIMD and floating-point
245 functionality from all Exception levels.
246
247 - ``CPSR.A``. The Asynchronous data abort interrupt is enabled by clearing
248 the Asynchronous data abort interrupt mask bit.
249
250 - ``SDCR``. The ``SDCR.SPD`` field is set to disable AArch32 Secure
251 self-hosted privileged debug.
252
253Platform initialization
254^^^^^^^^^^^^^^^^^^^^^^^
255
256On ARM platforms, BL1 performs the following platform initializations:
257
258- Enable the Trusted Watchdog.
259- Initialize the console.
260- Configure the Interconnect to enable hardware coherency.
261- Enable the MMU and map the memory it needs to access.
262- Configure any required platform storage to load the next bootloader image
263 (BL2).
264
265Firmware Update detection and execution
266^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
267
268After performing platform setup, BL1 common code calls
269``bl1_plat_get_next_image_id()`` to determine if `Firmware Update`_ is required or
270to proceed with the normal boot process. If the platform code returns
271``BL2_IMAGE_ID`` then the normal boot sequence is executed as described in the
272next section, else BL1 assumes that `Firmware Update`_ is required and execution
273passes to the first image in the `Firmware Update`_ process. In either case, BL1
274retrieves a descriptor of the next image by calling ``bl1_plat_get_image_desc()``.
275The image descriptor contains an ``entry_point_info_t`` structure, which BL1
276uses to initialize the execution state of the next image.
277
278BL2 image load and execution
279^^^^^^^^^^^^^^^^^^^^^^^^^^^^
280
281In the normal boot flow, BL1 execution continues as follows:
282
283#. BL1 prints the following string from the primary CPU to indicate successful
284 execution of the BL1 stage:
285
286 ::
287
288 "Booting Trusted Firmware"
289
290#. BL1 determines the amount of free trusted SRAM memory available by
291 calculating the extent of its own data section, which also resides in
292 trusted SRAM. BL1 loads a BL2 raw binary image from platform storage, at a
293 platform-specific base address. If the BL2 image file is not present or if
294 there is not enough free trusted SRAM the following error message is
295 printed:
296
297 ::
298
299 "Failed to load BL2 firmware."
300
301 BL1 calculates the amount of Trusted SRAM that can be used by the BL2
302 image. The exact load location of the image is provided as a base address
303 in the platform header. Further description of the memory layout can be
304 found later in this document.
305
306#. BL1 passes control to the BL2 image at Secure EL1 (for AArch64) or at
307 Secure SVC mode (for AArch32), starting from its load address.
308
309#. BL1 also passes information about the amount of trusted SRAM used and
310 available for use. This information is populated at a platform-specific
311 memory address.
312
313BL2
314~~~
315
316BL1 loads and passes control to BL2 at Secure-EL1 (for AArch64) or at Secure
317SVC mode (for AArch32) . BL2 is linked against and loaded at a platform-specific
318base address (more information can be found later in this document).
319The functionality implemented by BL2 is as follows.
320
321Architectural initialization
322^^^^^^^^^^^^^^^^^^^^^^^^^^^^
323
324For AArch64, BL2 performs the minimal architectural initialization required
325for subsequent stages of the ARM Trusted Firmware and normal world software.
326EL1 and EL0 are given access to Floating Point and Advanced SIMD registers
327by clearing the ``CPACR.FPEN`` bits.
328
329For AArch32, the minimal architectural initialization required for subsequent
330stages of the ARM Trusted Firmware and normal world software is taken care of
331in BL1 as both BL1 and BL2 execute at PL1.
332
333Platform initialization
334^^^^^^^^^^^^^^^^^^^^^^^
335
336On ARM platforms, BL2 performs the following platform initializations:
337
338- Initialize the console.
339- Configure any required platform storage to allow loading further bootloader
340 images.
341- Enable the MMU and map the memory it needs to access.
342- Perform platform security setup to allow access to controlled components.
343- Reserve some memory for passing information to the next bootloader image
344 EL3 Runtime Software and populate it.
345- Define the extents of memory available for loading each subsequent
346 bootloader image.
347
348Image loading in BL2
349^^^^^^^^^^^^^^^^^^^^
350
351Image loading scheme in BL2 depends on ``LOAD_IMAGE_V2`` build option. If the
352flag is disabled, the BLxx images are loaded, by calling the respective
353load\_blxx() function from BL2 generic code. If the flag is enabled, the BL2
354generic code loads the images based on the list of loadable images provided
355by the platform. BL2 passes the list of executable images provided by the
356platform to the next handover BL image. By default, this flag is disabled for
357AArch64 and the AArch32 build is supported only if this flag is enabled.
358
359SCP\_BL2 (System Control Processor Firmware) image load
360^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
361
362Some systems have a separate System Control Processor (SCP) for power, clock,
363reset and system control. BL2 loads the optional SCP\_BL2 image from platform
364storage into a platform-specific region of secure memory. The subsequent
365handling of SCP\_BL2 is platform specific. For example, on the Juno ARM
366development platform port the image is transferred into SCP's internal memory
367using the Boot Over MHU (BOM) protocol after being loaded in the trusted SRAM
368memory. The SCP executes SCP\_BL2 and signals to the Application Processor (AP)
369for BL2 execution to continue.
370
371EL3 Runtime Software image load
372^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
373
374BL2 loads the EL3 Runtime Software image from platform storage into a platform-
375specific address in trusted SRAM. If there is not enough memory to load the
376image or image is missing it leads to an assertion failure. If ``LOAD_IMAGE_V2``
377is disabled and if image loads successfully, BL2 updates the amount of trusted
378SRAM used and available for use by EL3 Runtime Software. This information is
379populated at a platform-specific memory address.
380
381AArch64 BL32 (Secure-EL1 Payload) image load
382^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
383
384BL2 loads the optional BL32 image from platform storage into a platform-
385specific region of secure memory. The image executes in the secure world. BL2
386relies on BL31 to pass control to the BL32 image, if present. Hence, BL2
387populates a platform-specific area of memory with the entrypoint/load-address
388of the BL32 image. The value of the Saved Processor Status Register (``SPSR``)
389for entry into BL32 is not determined by BL2, it is initialized by the
390Secure-EL1 Payload Dispatcher (see later) within BL31, which is responsible for
391managing interaction with BL32. This information is passed to BL31.
392
393BL33 (Non-trusted Firmware) image load
394^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
395
396BL2 loads the BL33 image (e.g. UEFI or other test or boot software) from
397platform storage into non-secure memory as defined by the platform.
398
399BL2 relies on EL3 Runtime Software to pass control to BL33 once secure state
400initialization is complete. Hence, BL2 populates a platform-specific area of
401memory with the entrypoint and Saved Program Status Register (``SPSR``) of the
402normal world software image. The entrypoint is the load address of the BL33
403image. The ``SPSR`` is determined as specified in Section 5.13 of the
404`PSCI PDD`_. This information is passed to the EL3 Runtime Software.
405
406AArch64 BL31 (EL3 Runtime Software) execution
407^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
408
409BL2 execution continues as follows:
410
411#. BL2 passes control back to BL1 by raising an SMC, providing BL1 with the
412 BL31 entrypoint. The exception is handled by the SMC exception handler
413 installed by BL1.
414
415#. BL1 turns off the MMU and flushes the caches. It clears the
416 ``SCTLR_EL3.M/I/C`` bits, flushes the data cache to the point of coherency
417 and invalidates the TLBs.
418
419#. BL1 passes control to BL31 at the specified entrypoint at EL3.
420
421AArch64 BL31
422~~~~~~~~~~~~
423
424The image for this stage is loaded by BL2 and BL1 passes control to BL31 at
425EL3. BL31 executes solely in trusted SRAM. BL31 is linked against and
426loaded at a platform-specific base address (more information can be found later
427in this document). The functionality implemented by BL31 is as follows.
428
429Architectural initialization
430^^^^^^^^^^^^^^^^^^^^^^^^^^^^
431
432Currently, BL31 performs a similar architectural initialization to BL1 as
433far as system register settings are concerned. Since BL1 code resides in ROM,
434architectural initialization in BL31 allows override of any previous
435initialization done by BL1.
436
437BL31 initializes the per-CPU data framework, which provides a cache of
438frequently accessed per-CPU data optimised for fast, concurrent manipulation
439on different CPUs. This buffer includes pointers to per-CPU contexts, crash
440buffer, CPU reset and power down operations, PSCI data, platform data and so on.
441
442It then replaces the exception vectors populated by BL1 with its own. BL31
443exception vectors implement more elaborate support for handling SMCs since this
444is the only mechanism to access the runtime services implemented by BL31 (PSCI
445for example). BL31 checks each SMC for validity as specified by the
446`SMC calling convention PDD`_ before passing control to the required SMC
447handler routine.
448
449BL31 programs the ``CNTFRQ_EL0`` register with the clock frequency of the system
450counter, which is provided by the platform.
451
452Platform initialization
453^^^^^^^^^^^^^^^^^^^^^^^
454
455BL31 performs detailed platform initialization, which enables normal world
456software to function correctly.
457
458On ARM platforms, this consists of the following:
459
460- Initialize the console.
461- Configure the Interconnect to enable hardware coherency.
462- Enable the MMU and map the memory it needs to access.
463- Initialize the generic interrupt controller.
464- Initialize the power controller device.
465- Detect the system topology.
466
467Runtime services initialization
468^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
469
470BL31 is responsible for initializing the runtime services. One of them is PSCI.
471
472As part of the PSCI initializations, BL31 detects the system topology. It also
473initializes the data structures that implement the state machine used to track
474the state of power domain nodes. The state can be one of ``OFF``, ``RUN`` or
475``RETENTION``. All secondary CPUs are initially in the ``OFF`` state. The cluster
476that the primary CPU belongs to is ``ON``; any other cluster is ``OFF``. It also
477initializes the locks that protect them. BL31 accesses the state of a CPU or
478cluster immediately after reset and before the data cache is enabled in the
479warm boot path. It is not currently possible to use 'exclusive' based spinlocks,
480therefore BL31 uses locks based on Lamport's Bakery algorithm instead.
481
482The runtime service framework and its initialization is described in more
483detail in the "EL3 runtime services framework" section below.
484
485Details about the status of the PSCI implementation are provided in the
486"Power State Coordination Interface" section below.
487
488AArch64 BL32 (Secure-EL1 Payload) image initialization
489^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
490
491If a BL32 image is present then there must be a matching Secure-EL1 Payload
492Dispatcher (SPD) service (see later for details). During initialization
493that service must register a function to carry out initialization of BL32
494once the runtime services are fully initialized. BL31 invokes such a
495registered function to initialize BL32 before running BL33. This initialization
496is not necessary for AArch32 SPs.
497
498Details on BL32 initialization and the SPD's role are described in the
499"Secure-EL1 Payloads and Dispatchers" section below.
500
501BL33 (Non-trusted Firmware) execution
502^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
503
504EL3 Runtime Software initializes the EL2 or EL1 processor context for normal-
505world cold boot, ensuring that no secure state information finds its way into
506the non-secure execution state. EL3 Runtime Software uses the entrypoint
507information provided by BL2 to jump to the Non-trusted firmware image (BL33)
508at the highest available Exception Level (EL2 if available, otherwise EL1).
509
510Using alternative Trusted Boot Firmware in place of BL1 & BL2 (AArch64 only)
511~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
512
513Some platforms have existing implementations of Trusted Boot Firmware that
514would like to use ARM Trusted Firmware BL31 for the EL3 Runtime Software. To
515enable this firmware architecture it is important to provide a fully documented
516and stable interface between the Trusted Boot Firmware and BL31.
517
518Future changes to the BL31 interface will be done in a backwards compatible
519way, and this enables these firmware components to be independently enhanced/
520updated to develop and exploit new functionality.
521
522Required CPU state when calling ``bl31_entrypoint()`` during cold boot
523^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
524
525This function must only be called by the primary CPU.
526
527On entry to this function the calling primary CPU must be executing in AArch64
528EL3, little-endian data access, and all interrupt sources masked:
529
530::
531
532 PSTATE.EL = 3
533 PSTATE.RW = 1
534 PSTATE.DAIF = 0xf
535 SCTLR_EL3.EE = 0
536
537X0 and X1 can be used to pass information from the Trusted Boot Firmware to the
538platform code in BL31:
539
540::
541
542 X0 : Reserved for common Trusted Firmware information
543 X1 : Platform specific information
544
545BL31 zero-init sections (e.g. ``.bss``) should not contain valid data on entry,
546these will be zero filled prior to invoking platform setup code.
547
548Use of the X0 and X1 parameters
549'''''''''''''''''''''''''''''''
550
551The parameters are platform specific and passed from ``bl31_entrypoint()`` to
552``bl31_early_platform_setup()``. The value of these parameters is never directly
553used by the common BL31 code.
554
555The convention is that ``X0`` conveys information regarding the BL31, BL32 and
556BL33 images from the Trusted Boot firmware and ``X1`` can be used for other
557platform specific purpose. This convention allows platforms which use ARM
558Trusted Firmware's BL1 and BL2 images to transfer additional platform specific
559information from Secure Boot without conflicting with future evolution of the
560Trusted Firmware using ``X0`` to pass a ``bl31_params`` structure.
561
562BL31 common and SPD initialization code depends on image and entrypoint
563information about BL33 and BL32, which is provided via BL31 platform APIs.
564This information is required until the start of execution of BL33. This
565information can be provided in a platform defined manner, e.g. compiled into
566the platform code in BL31, or provided in a platform defined memory location
567by the Trusted Boot firmware, or passed from the Trusted Boot Firmware via the
568Cold boot Initialization parameters. This data may need to be cleaned out of
569the CPU caches if it is provided by an earlier boot stage and then accessed by
570BL31 platform code before the caches are enabled.
571
572ARM Trusted Firmware's BL2 implementation passes a ``bl31_params`` structure in
573``X0`` and the ARM development platforms interpret this in the BL31 platform
574code.
575
576MMU, Data caches & Coherency
577''''''''''''''''''''''''''''
578
579BL31 does not depend on the enabled state of the MMU, data caches or
580interconnect coherency on entry to ``bl31_entrypoint()``. If these are disabled
581on entry, these should be enabled during ``bl31_plat_arch_setup()``.
582
583Data structures used in the BL31 cold boot interface
584''''''''''''''''''''''''''''''''''''''''''''''''''''
585
586These structures are designed to support compatibility and independent
587evolution of the structures and the firmware images. For example, a version of
588BL31 that can interpret the BL3x image information from different versions of
589BL2, a platform that uses an extended entry\_point\_info structure to convey
590additional register information to BL31, or a ELF image loader that can convey
591more details about the firmware images.
592
593To support these scenarios the structures are versioned and sized, which enables
594BL31 to detect which information is present and respond appropriately. The
595``param_header`` is defined to capture this information:
596
597.. code:: c
598
599 typedef struct param_header {
600 uint8_t type; /* type of the structure */
601 uint8_t version; /* version of this structure */
602 uint16_t size; /* size of this structure in bytes */
603 uint32_t attr; /* attributes: unused bits SBZ */
604 } param_header_t;
605
606The structures using this format are ``entry_point_info``, ``image_info`` and
607``bl31_params``. The code that allocates and populates these structures must set
608the header fields appropriately, and the ``SET_PARAM_HEAD()`` a macro is defined
609to simplify this action.
610
611Required CPU state for BL31 Warm boot initialization
612^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
613
614When requesting a CPU power-on, or suspending a running CPU, ARM Trusted
615Firmware provides the platform power management code with a Warm boot
616initialization entry-point, to be invoked by the CPU immediately after the
617reset handler. On entry to the Warm boot initialization function the calling
618CPU must be in AArch64 EL3, little-endian data access and all interrupt sources
619masked:
620
621::
622
623 PSTATE.EL = 3
624 PSTATE.RW = 1
625 PSTATE.DAIF = 0xf
626 SCTLR_EL3.EE = 0
627
628The PSCI implementation will initialize the processor state and ensure that the
629platform power management code is then invoked as required to initialize all
630necessary system, cluster and CPU resources.
631
632AArch32 EL3 Runtime Software entrypoint interface
633~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
634
635To enable this firmware architecture it is important to provide a fully
636documented and stable interface between the Trusted Boot Firmware and the
637AArch32 EL3 Runtime Software.
638
639Future changes to the entrypoint interface will be done in a backwards
640compatible way, and this enables these firmware components to be independently
641enhanced/updated to develop and exploit new functionality.
642
643Required CPU state when entering during cold boot
644^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
645
646This function must only be called by the primary CPU.
647
648On entry to this function the calling primary CPU must be executing in AArch32
649EL3, little-endian data access, and all interrupt sources masked:
650
651::
652
653 PSTATE.AIF = 0x7
654 SCTLR.EE = 0
655
656R0 and R1 are used to pass information from the Trusted Boot Firmware to the
657platform code in AArch32 EL3 Runtime Software:
658
659::
660
661 R0 : Reserved for common Trusted Firmware information
662 R1 : Platform specific information
663
664Use of the R0 and R1 parameters
665'''''''''''''''''''''''''''''''
666
667The parameters are platform specific and the convention is that ``R0`` conveys
668information regarding the BL3x images from the Trusted Boot firmware and ``R1``
669can be used for other platform specific purpose. This convention allows
670platforms which use ARM Trusted Firmware's BL1 and BL2 images to transfer
671additional platform specific information from Secure Boot without conflicting
672with future evolution of the Trusted Firmware using ``R0`` to pass a ``bl_params``
673structure.
674
675The AArch32 EL3 Runtime Software is responsible for entry into BL33. This
676information can be obtained in a platform defined manner, e.g. compiled into
677the AArch32 EL3 Runtime Software, or provided in a platform defined memory
678location by the Trusted Boot firmware, or passed from the Trusted Boot Firmware
679via the Cold boot Initialization parameters. This data may need to be cleaned
680out of the CPU caches if it is provided by an earlier boot stage and then
681accessed by AArch32 EL3 Runtime Software before the caches are enabled.
682
683When using AArch32 EL3 Runtime Software, the ARM development platforms pass a
684``bl_params`` structure in ``R0`` from BL2 to be interpreted by AArch32 EL3 Runtime
685Software platform code.
686
687MMU, Data caches & Coherency
688''''''''''''''''''''''''''''
689
690AArch32 EL3 Runtime Software must not depend on the enabled state of the MMU,
691data caches or interconnect coherency in its entrypoint. They must be explicitly
692enabled if required.
693
694Data structures used in cold boot interface
695'''''''''''''''''''''''''''''''''''''''''''
696
697The AArch32 EL3 Runtime Software cold boot interface uses ``bl_params`` instead
698of ``bl31_params``. The ``bl_params`` structure is based on the convention
699described in AArch64 BL31 cold boot interface section.
700
701Required CPU state for warm boot initialization
702^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
703
704When requesting a CPU power-on, or suspending a running CPU, AArch32 EL3
705Runtime Software must ensure execution of a warm boot initialization entrypoint.
706If ARM Trusted Firmware BL1 is used and the PROGRAMMABLE\_RESET\_ADDRESS build
707flag is false, then AArch32 EL3 Runtime Software must ensure that BL1 branches
708to the warm boot entrypoint by arranging for the BL1 platform function,
709plat\_get\_my\_entrypoint(), to return a non-zero value.
710
711In this case, the warm boot entrypoint must be in AArch32 EL3, little-endian
712data access and all interrupt sources masked:
713
714::
715
716 PSTATE.AIF = 0x7
717 SCTLR.EE = 0
718
719The warm boot entrypoint may be implemented by using the ARM Trusted Firmware
720``psci_warmboot_entrypoint()`` function. In that case, the platform must fulfil
721the pre-requisites mentioned in the `PSCI Library integration guide`_.
722
723EL3 runtime services framework
724------------------------------
725
726Software executing in the non-secure state and in the secure state at exception
727levels lower than EL3 will request runtime services using the Secure Monitor
728Call (SMC) instruction. These requests will follow the convention described in
729the SMC Calling Convention PDD (`SMCCC`_). The `SMCCC`_ assigns function
730identifiers to each SMC request and describes how arguments are passed and
731returned.
732
733The EL3 runtime services framework enables the development of services by
734different providers that can be easily integrated into final product firmware.
735The following sections describe the framework which facilitates the
736registration, initialization and use of runtime services in EL3 Runtime
737Software (BL31).
738
739The design of the runtime services depends heavily on the concepts and
740definitions described in the `SMCCC`_, in particular SMC Function IDs, Owning
741Entity Numbers (OEN), Fast and Yielding calls, and the SMC32 and SMC64 calling
742conventions. Please refer to that document for more detailed explanation of
743these terms.
744
745The following runtime services are expected to be implemented first. They have
746not all been instantiated in the current implementation.
747
748#. Standard service calls
749
750 This service is for management of the entire system. The Power State
751 Coordination Interface (`PSCI`_) is the first set of standard service calls
752 defined by ARM (see PSCI section later).
753
754#. Secure-EL1 Payload Dispatcher service
755
756 If a system runs a Trusted OS or other Secure-EL1 Payload (SP) then
757 it also requires a *Secure Monitor* at EL3 to switch the EL1 processor
758 context between the normal world (EL1/EL2) and trusted world (Secure-EL1).
759 The Secure Monitor will make these world switches in response to SMCs. The
760 `SMCCC`_ provides for such SMCs with the Trusted OS Call and Trusted
761 Application Call OEN ranges.
762
763 The interface between the EL3 Runtime Software and the Secure-EL1 Payload is
764 not defined by the `SMCCC`_ or any other standard. As a result, each
765 Secure-EL1 Payload requires a specific Secure Monitor that runs as a runtime
766 service - within ARM Trusted Firmware this service is referred to as the
767 Secure-EL1 Payload Dispatcher (SPD).
768
769 ARM Trusted Firmware provides a Test Secure-EL1 Payload (TSP) and its
770 associated Dispatcher (TSPD). Details of SPD design and TSP/TSPD operation
771 are described in the "Secure-EL1 Payloads and Dispatchers" section below.
772
773#. CPU implementation service
774
775 This service will provide an interface to CPU implementation specific
776 services for a given platform e.g. access to processor errata workarounds.
777 This service is currently unimplemented.
778
779Additional services for ARM Architecture, SiP and OEM calls can be implemented.
780Each implemented service handles a range of SMC function identifiers as
781described in the `SMCCC`_.
782
783Registration
784~~~~~~~~~~~~
785
786A runtime service is registered using the ``DECLARE_RT_SVC()`` macro, specifying
787the name of the service, the range of OENs covered, the type of service and
788initialization and call handler functions. This macro instantiates a ``const struct rt_svc_desc`` for the service with these details (see ``runtime_svc.h``).
789This structure is allocated in a special ELF section ``rt_svc_descs``, enabling
790the framework to find all service descriptors included into BL31.
791
792The specific service for a SMC Function is selected based on the OEN and call
793type of the Function ID, and the framework uses that information in the service
794descriptor to identify the handler for the SMC Call.
795
796The service descriptors do not include information to identify the precise set
797of SMC function identifiers supported by this service implementation, the
798security state from which such calls are valid nor the capability to support
79964-bit and/or 32-bit callers (using SMC32 or SMC64). Responding appropriately
800to these aspects of a SMC call is the responsibility of the service
801implementation, the framework is focused on integration of services from
802different providers and minimizing the time taken by the framework before the
803service handler is invoked.
804
805Details of the parameters, requirements and behavior of the initialization and
806call handling functions are provided in the following sections.
807
808Initialization
809~~~~~~~~~~~~~~
810
811``runtime_svc_init()`` in ``runtime_svc.c`` initializes the runtime services
812framework running on the primary CPU during cold boot as part of the BL31
813initialization. This happens prior to initializing a Trusted OS and running
814Normal world boot firmware that might in turn use these services.
815Initialization involves validating each of the declared runtime service
816descriptors, calling the service initialization function and populating the
817index used for runtime lookup of the service.
818
819The BL31 linker script collects all of the declared service descriptors into a
820single array and defines symbols that allow the framework to locate and traverse
821the array, and determine its size.
822
823The framework does basic validation of each descriptor to halt firmware
824initialization if service declaration errors are detected. The framework does
825not check descriptors for the following error conditions, and may behave in an
826unpredictable manner under such scenarios:
827
828#. Overlapping OEN ranges
829#. Multiple descriptors for the same range of OENs and ``call_type``
830#. Incorrect range of owning entity numbers for a given ``call_type``
831
832Once validated, the service ``init()`` callback is invoked. This function carries
833out any essential EL3 initialization before servicing requests. The ``init()``
834function is only invoked on the primary CPU during cold boot. If the service
835uses per-CPU data this must either be initialized for all CPUs during this call,
836or be done lazily when a CPU first issues an SMC call to that service. If
837``init()`` returns anything other than ``0``, this is treated as an initialization
838error and the service is ignored: this does not cause the firmware to halt.
839
840The OEN and call type fields present in the SMC Function ID cover a total of
841128 distinct services, but in practice a single descriptor can cover a range of
842OENs, e.g. SMCs to call a Trusted OS function. To optimize the lookup of a
843service handler, the framework uses an array of 128 indices that map every
844distinct OEN/call-type combination either to one of the declared services or to
845indicate the service is not handled. This ``rt_svc_descs_indices[]`` array is
846populated for all of the OENs covered by a service after the service ``init()``
847function has reported success. So a service that fails to initialize will never
848have it's ``handle()`` function invoked.
849
850The following figure shows how the ``rt_svc_descs_indices[]`` index maps the SMC
851Function ID call type and OEN onto a specific service handler in the
852``rt_svc_descs[]`` array.
853
854|Image 1|
855
856Handling an SMC
857~~~~~~~~~~~~~~~
858
859When the EL3 runtime services framework receives a Secure Monitor Call, the SMC
860Function ID is passed in W0 from the lower exception level (as per the
861`SMCCC`_). If the calling register width is AArch32, it is invalid to invoke an
862SMC Function which indicates the SMC64 calling convention: such calls are
863ignored and return the Unknown SMC Function Identifier result code ``0xFFFFFFFF``
864in R0/X0.
865
866Bit[31] (fast/yielding call) and bits[29:24] (owning entity number) of the SMC
867Function ID are combined to index into the ``rt_svc_descs_indices[]`` array. The
868resulting value might indicate a service that has no handler, in this case the
869framework will also report an Unknown SMC Function ID. Otherwise, the value is
870used as a further index into the ``rt_svc_descs[]`` array to locate the required
871service and handler.
872
873The service's ``handle()`` callback is provided with five of the SMC parameters
874directly, the others are saved into memory for retrieval (if needed) by the
875handler. The handler is also provided with an opaque ``handle`` for use with the
876supporting library for parameter retrieval, setting return values and context
877manipulation; and with ``flags`` indicating the security state of the caller. The
878framework finally sets up the execution stack for the handler, and invokes the
879services ``handle()`` function.
880
881On return from the handler the result registers are populated in X0-X3 before
882restoring the stack and CPU state and returning from the original SMC.
883
884Power State Coordination Interface
885----------------------------------
886
887TODO: Provide design walkthrough of PSCI implementation.
888
889The PSCI v1.0 specification categorizes APIs as optional and mandatory. All the
890mandatory APIs in PSCI v1.0 and all the APIs in PSCI v0.2 draft specification
891`Power State Coordination Interface PDD`_ are implemented. The table lists
892the PSCI v1.0 APIs and their support in generic code.
893
894An API implementation might have a dependency on platform code e.g. CPU\_SUSPEND
895requires the platform to export a part of the implementation. Hence the level
896of support of the mandatory APIs depends upon the support exported by the
897platform port as well. The Juno and FVP (all variants) platforms export all the
898required support.
899
900+-----------------------------+-------------+-------------------------------+
901| PSCI v1.0 API | Supported | Comments |
902+=============================+=============+===============================+
903| ``PSCI_VERSION`` | Yes | The version returned is 1.0 |
904+-----------------------------+-------------+-------------------------------+
905| ``CPU_SUSPEND`` | Yes\* | |
906+-----------------------------+-------------+-------------------------------+
907| ``CPU_OFF`` | Yes\* | |
908+-----------------------------+-------------+-------------------------------+
909| ``CPU_ON`` | Yes\* | |
910+-----------------------------+-------------+-------------------------------+
911| ``AFFINITY_INFO`` | Yes | |
912+-----------------------------+-------------+-------------------------------+
913| ``MIGRATE`` | Yes\*\* | |
914+-----------------------------+-------------+-------------------------------+
915| ``MIGRATE_INFO_TYPE`` | Yes\*\* | |
916+-----------------------------+-------------+-------------------------------+
917| ``MIGRATE_INFO_CPU`` | Yes\*\* | |
918+-----------------------------+-------------+-------------------------------+
919| ``SYSTEM_OFF`` | Yes\* | |
920+-----------------------------+-------------+-------------------------------+
921| ``SYSTEM_RESET`` | Yes\* | |
922+-----------------------------+-------------+-------------------------------+
923| ``PSCI_FEATURES`` | Yes | |
924+-----------------------------+-------------+-------------------------------+
925| ``CPU_FREEZE`` | No | |
926+-----------------------------+-------------+-------------------------------+
927| ``CPU_DEFAULT_SUSPEND`` | No | |
928+-----------------------------+-------------+-------------------------------+
929| ``NODE_HW_STATE`` | Yes\* | |
930+-----------------------------+-------------+-------------------------------+
931| ``SYSTEM_SUSPEND`` | Yes\* | |
932+-----------------------------+-------------+-------------------------------+
933| ``PSCI_SET_SUSPEND_MODE`` | No | |
934+-----------------------------+-------------+-------------------------------+
935| ``PSCI_STAT_RESIDENCY`` | Yes\* | |
936+-----------------------------+-------------+-------------------------------+
937| ``PSCI_STAT_COUNT`` | Yes\* | |
938+-----------------------------+-------------+-------------------------------+
939
940\*Note : These PSCI APIs require platform power management hooks to be
941registered with the generic PSCI code to be supported.
942
943\*\*Note : These PSCI APIs require appropriate Secure Payload Dispatcher
944hooks to be registered with the generic PSCI code to be supported.
945
946The PSCI implementation in ARM Trusted Firmware is a library which can be
947integrated with AArch64 or AArch32 EL3 Runtime Software for ARMv8-A systems.
948A guide to integrating PSCI library with AArch32 EL3 Runtime Software
949can be found `here`_.
950
951Secure-EL1 Payloads and Dispatchers
952-----------------------------------
953
954On a production system that includes a Trusted OS running in Secure-EL1/EL0,
955the Trusted OS is coupled with a companion runtime service in the BL31
956firmware. This service is responsible for the initialisation of the Trusted
957OS and all communications with it. The Trusted OS is the BL32 stage of the
958boot flow in ARM Trusted Firmware. The firmware will attempt to locate, load
959and execute a BL32 image.
960
961ARM Trusted Firmware uses a more general term for the BL32 software that runs
962at Secure-EL1 - the *Secure-EL1 Payload* - as it is not always a Trusted OS.
963
964The ARM Trusted Firmware provides a Test Secure-EL1 Payload (TSP) and a Test
965Secure-EL1 Payload Dispatcher (TSPD) service as an example of how a Trusted OS
966is supported on a production system using the Runtime Services Framework. On
967such a system, the Test BL32 image and service are replaced by the Trusted OS
968and its dispatcher service. The ARM Trusted Firmware build system expects that
969the dispatcher will define the build flag ``NEED_BL32`` to enable it to include
970the BL32 in the build either as a binary or to compile from source depending
971on whether the ``BL32`` build option is specified or not.
972
973The TSP runs in Secure-EL1. It is designed to demonstrate synchronous
974communication with the normal-world software running in EL1/EL2. Communication
975is initiated by the normal-world software
976
977- either directly through a Fast SMC (as defined in the `SMCCC`_)
978
979- or indirectly through a `PSCI`_ SMC. The `PSCI`_ implementation in turn
980 informs the TSPD about the requested power management operation. This allows
981 the TSP to prepare for or respond to the power state change
982
983The TSPD service is responsible for.
984
985- Initializing the TSP
986
987- Routing requests and responses between the secure and the non-secure
988 states during the two types of communications just described
989
990Initializing a BL32 Image
991~~~~~~~~~~~~~~~~~~~~~~~~~
992
993The Secure-EL1 Payload Dispatcher (SPD) service is responsible for initializing
994the BL32 image. It needs access to the information passed by BL2 to BL31 to do
995so. This is provided by:
996
997.. code:: c
998
999 entry_point_info_t *bl31_plat_get_next_image_ep_info(uint32_t);
1000
1001which returns a reference to the ``entry_point_info`` structure corresponding to
1002the image which will be run in the specified security state. The SPD uses this
1003API to get entry point information for the SECURE image, BL32.
1004
1005In the absence of a BL32 image, BL31 passes control to the normal world
1006bootloader image (BL33). When the BL32 image is present, it is typical
1007that the SPD wants control to be passed to BL32 first and then later to BL33.
1008
1009To do this the SPD has to register a BL32 initialization function during
1010initialization of the SPD service. The BL32 initialization function has this
1011prototype:
1012
1013.. code:: c
1014
1015 int32_t init(void);
1016
1017and is registered using the ``bl31_register_bl32_init()`` function.
1018
1019Trusted Firmware supports two approaches for the SPD to pass control to BL32
1020before returning through EL3 and running the non-trusted firmware (BL33):
1021
1022#. In the BL32 setup function, use ``bl31_set_next_image_type()`` to
1023 request that the exit from ``bl31_main()`` is to the BL32 entrypoint in
1024 Secure-EL1. BL31 will exit to BL32 using the asynchronous method by
1025 calling ``bl31_prepare_next_image_entry()`` and ``el3_exit()``.
1026
1027 When the BL32 has completed initialization at Secure-EL1, it returns to
1028 BL31 by issuing an SMC, using a Function ID allocated to the SPD. On
1029 receipt of this SMC, the SPD service handler should switch the CPU context
1030 from trusted to normal world and use the ``bl31_set_next_image_type()`` and
1031 ``bl31_prepare_next_image_entry()`` functions to set up the initial return to
1032 the normal world firmware BL33. On return from the handler the framework
1033 will exit to EL2 and run BL33.
1034
1035#. The BL32 setup function registers an initialization function using
1036 ``bl31_register_bl32_init()`` which provides a SPD-defined mechanism to
1037 invoke a 'world-switch synchronous call' to Secure-EL1 to run the BL32
1038 entrypoint.
1039 NOTE: The Test SPD service included with the Trusted Firmware provides one
1040 implementation of such a mechanism.
1041
1042 On completion BL32 returns control to BL31 via a SMC, and on receipt the
1043 SPD service handler invokes the synchronous call return mechanism to return
1044 to the BL32 initialization function. On return from this function,
1045 ``bl31_main()`` will set up the return to the normal world firmware BL33 and
1046 continue the boot process in the normal world.
1047
Jeenu Viswambharanb60420a2017-08-24 15:43:44 +01001048Crash Reporting in BL31
1049-----------------------
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001050
1051BL31 implements a scheme for reporting the processor state when an unhandled
1052exception is encountered. The reporting mechanism attempts to preserve all the
1053register contents and report it via a dedicated UART (PL011 console). BL31
1054reports the general purpose, EL3, Secure EL1 and some EL2 state registers.
1055
1056A dedicated per-CPU crash stack is maintained by BL31 and this is retrieved via
1057the per-CPU pointer cache. The implementation attempts to minimise the memory
1058required for this feature. The file ``crash_reporting.S`` contains the
1059implementation for crash reporting.
1060
1061The sample crash output is shown below.
1062
1063::
1064
1065 x0 :0x000000004F00007C
1066 x1 :0x0000000007FFFFFF
1067 x2 :0x0000000004014D50
1068 x3 :0x0000000000000000
1069 x4 :0x0000000088007998
1070 x5 :0x00000000001343AC
1071 x6 :0x0000000000000016
1072 x7 :0x00000000000B8A38
1073 x8 :0x00000000001343AC
1074 x9 :0x00000000000101A8
1075 x10 :0x0000000000000002
1076 x11 :0x000000000000011C
1077 x12 :0x00000000FEFDC644
1078 x13 :0x00000000FED93FFC
1079 x14 :0x0000000000247950
1080 x15 :0x00000000000007A2
1081 x16 :0x00000000000007A4
1082 x17 :0x0000000000247950
1083 x18 :0x0000000000000000
1084 x19 :0x00000000FFFFFFFF
1085 x20 :0x0000000004014D50
1086 x21 :0x000000000400A38C
1087 x22 :0x0000000000247950
1088 x23 :0x0000000000000010
1089 x24 :0x0000000000000024
1090 x25 :0x00000000FEFDC868
1091 x26 :0x00000000FEFDC86A
1092 x27 :0x00000000019EDEDC
1093 x28 :0x000000000A7CFDAA
1094 x29 :0x0000000004010780
1095 x30 :0x000000000400F004
1096 scr_el3 :0x0000000000000D3D
1097 sctlr_el3 :0x0000000000C8181F
1098 cptr_el3 :0x0000000000000000
1099 tcr_el3 :0x0000000080803520
1100 daif :0x00000000000003C0
1101 mair_el3 :0x00000000000004FF
1102 spsr_el3 :0x00000000800003CC
1103 elr_el3 :0x000000000400C0CC
1104 ttbr0_el3 :0x00000000040172A0
1105 esr_el3 :0x0000000096000210
1106 sp_el3 :0x0000000004014D50
1107 far_el3 :0x000000004F00007C
1108 spsr_el1 :0x0000000000000000
1109 elr_el1 :0x0000000000000000
1110 spsr_abt :0x0000000000000000
1111 spsr_und :0x0000000000000000
1112 spsr_irq :0x0000000000000000
1113 spsr_fiq :0x0000000000000000
1114 sctlr_el1 :0x0000000030C81807
1115 actlr_el1 :0x0000000000000000
1116 cpacr_el1 :0x0000000000300000
1117 csselr_el1 :0x0000000000000002
1118 sp_el1 :0x0000000004028800
1119 esr_el1 :0x0000000000000000
1120 ttbr0_el1 :0x000000000402C200
1121 ttbr1_el1 :0x0000000000000000
1122 mair_el1 :0x00000000000004FF
1123 amair_el1 :0x0000000000000000
1124 tcr_el1 :0x0000000000003520
1125 tpidr_el1 :0x0000000000000000
1126 tpidr_el0 :0x0000000000000000
1127 tpidrro_el0 :0x0000000000000000
1128 dacr32_el2 :0x0000000000000000
1129 ifsr32_el2 :0x0000000000000000
1130 par_el1 :0x0000000000000000
1131 far_el1 :0x0000000000000000
1132 afsr0_el1 :0x0000000000000000
1133 afsr1_el1 :0x0000000000000000
1134 contextidr_el1 :0x0000000000000000
1135 vbar_el1 :0x0000000004027000
1136 cntp_ctl_el0 :0x0000000000000000
1137 cntp_cval_el0 :0x0000000000000000
1138 cntv_ctl_el0 :0x0000000000000000
1139 cntv_cval_el0 :0x0000000000000000
1140 cntkctl_el1 :0x0000000000000000
1141 fpexc32_el2 :0x0000000004000700
1142 sp_el0 :0x0000000004010780
1143
1144Guidelines for Reset Handlers
1145-----------------------------
1146
1147Trusted Firmware implements a framework that allows CPU and platform ports to
1148perform actions very early after a CPU is released from reset in both the cold
1149and warm boot paths. This is done by calling the ``reset_handler()`` function in
1150both the BL1 and BL31 images. It in turn calls the platform and CPU specific
1151reset handling functions.
1152
1153Details for implementing a CPU specific reset handler can be found in
1154Section 8. Details for implementing a platform specific reset handler can be
1155found in the `Porting Guide`_ (see the ``plat_reset_handler()`` function).
1156
1157When adding functionality to a reset handler, keep in mind that if a different
1158reset handling behavior is required between the first and the subsequent
1159invocations of the reset handling code, this should be detected at runtime.
1160In other words, the reset handler should be able to detect whether an action has
1161already been performed and act as appropriate. Possible courses of actions are,
1162e.g. skip the action the second time, or undo/redo it.
1163
1164CPU specific operations framework
1165---------------------------------
1166
1167Certain aspects of the ARMv8 architecture are implementation defined,
1168that is, certain behaviours are not architecturally defined, but must be defined
1169and documented by individual processor implementations. The ARM Trusted
1170Firmware implements a framework which categorises the common implementation
1171defined behaviours and allows a processor to export its implementation of that
1172behaviour. The categories are:
1173
1174#. Processor specific reset sequence.
1175
1176#. Processor specific power down sequences.
1177
1178#. Processor specific register dumping as a part of crash reporting.
1179
1180#. Errata status reporting.
1181
1182Each of the above categories fulfils a different requirement.
1183
1184#. allows any processor specific initialization before the caches and MMU
1185 are turned on, like implementation of errata workarounds, entry into
1186 the intra-cluster coherency domain etc.
1187
1188#. allows each processor to implement the power down sequence mandated in
1189 its Technical Reference Manual (TRM).
1190
1191#. allows a processor to provide additional information to the developer
1192 in the event of a crash, for example Cortex-A53 has registers which
1193 can expose the data cache contents.
1194
1195#. allows a processor to define a function that inspects and reports the status
1196 of all errata workarounds on that processor.
1197
1198Please note that only 2. is mandated by the TRM.
1199
1200The CPU specific operations framework scales to accommodate a large number of
1201different CPUs during power down and reset handling. The platform can specify
1202any CPU optimization it wants to enable for each CPU. It can also specify
1203the CPU errata workarounds to be applied for each CPU type during reset
1204handling by defining CPU errata compile time macros. Details on these macros
1205can be found in the `cpu-specific-build-macros.rst`_ file.
1206
1207The CPU specific operations framework depends on the ``cpu_ops`` structure which
1208needs to be exported for each type of CPU in the platform. It is defined in
1209``include/lib/cpus/aarch64/cpu_macros.S`` and has the following fields : ``midr``,
1210``reset_func()``, ``cpu_pwr_down_ops`` (array of power down functions) and
1211``cpu_reg_dump()``.
1212
1213The CPU specific files in ``lib/cpus`` export a ``cpu_ops`` data structure with
1214suitable handlers for that CPU. For example, ``lib/cpus/aarch64/cortex_a53.S``
1215exports the ``cpu_ops`` for Cortex-A53 CPU. According to the platform
1216configuration, these CPU specific files must be included in the build by
1217the platform makefile. The generic CPU specific operations framework code exists
1218in ``lib/cpus/aarch64/cpu_helpers.S``.
1219
1220CPU specific Reset Handling
1221~~~~~~~~~~~~~~~~~~~~~~~~~~~
1222
1223After a reset, the state of the CPU when it calls generic reset handler is:
1224MMU turned off, both instruction and data caches turned off and not part
1225of any coherency domain.
1226
1227The BL entrypoint code first invokes the ``plat_reset_handler()`` to allow
1228the platform to perform any system initialization required and any system
1229errata workarounds that needs to be applied. The ``get_cpu_ops_ptr()`` reads
1230the current CPU midr, finds the matching ``cpu_ops`` entry in the ``cpu_ops``
1231array and returns it. Note that only the part number and implementer fields
1232in midr are used to find the matching ``cpu_ops`` entry. The ``reset_func()`` in
1233the returned ``cpu_ops`` is then invoked which executes the required reset
1234handling for that CPU and also any errata workarounds enabled by the platform.
1235This function must preserve the values of general purpose registers x20 to x29.
1236
1237Refer to Section "Guidelines for Reset Handlers" for general guidelines
1238regarding placement of code in a reset handler.
1239
1240CPU specific power down sequence
1241~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1242
1243During the BL31 initialization sequence, the pointer to the matching ``cpu_ops``
1244entry is stored in per-CPU data by ``init_cpu_ops()`` so that it can be quickly
1245retrieved during power down sequences.
1246
1247Various CPU drivers register handlers to perform power down at certain power
1248levels for that specific CPU. The PSCI service, upon receiving a power down
1249request, determines the highest power level at which to execute power down
1250sequence for a particular CPU. It uses the ``prepare_cpu_pwr_dwn()`` function to
1251pick the right power down handler for the requested level. The function
1252retrieves ``cpu_ops`` pointer member of per-CPU data, and from that, further
1253retrieves ``cpu_pwr_down_ops`` array, and indexes into the required level. If the
1254requested power level is higher than what a CPU driver supports, the handler
1255registered for highest level is invoked.
1256
1257At runtime the platform hooks for power down are invoked by the PSCI service to
1258perform platform specific operations during a power down sequence, for example
1259turning off CCI coherency during a cluster power down.
1260
1261CPU specific register reporting during crash
1262~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1263
1264If the crash reporting is enabled in BL31, when a crash occurs, the crash
1265reporting framework calls ``do_cpu_reg_dump`` which retrieves the matching
1266``cpu_ops`` using ``get_cpu_ops_ptr()`` function. The ``cpu_reg_dump()`` in
1267``cpu_ops`` is invoked, which then returns the CPU specific register values to
1268be reported and a pointer to the ASCII list of register names in a format
1269expected by the crash reporting framework.
1270
1271CPU errata status reporting
1272~~~~~~~~~~~~~~~~~~~~~~~~~~~
1273
1274Errata workarounds for CPUs supported in ARM Trusted Firmware are applied during
1275both cold and warm boots, shortly after reset. Individual Errata workarounds are
1276enabled as build options. Some errata workarounds have potential run-time
1277implications; therefore some are enabled by default, others not. Platform ports
1278shall override build options to enable or disable errata as appropriate. The CPU
1279drivers take care of applying errata workarounds that are enabled and applicable
1280to a given CPU. Refer to the section titled *CPU Errata Workarounds* in `CPUBM`_
1281for more information.
1282
1283Functions in CPU drivers that apply errata workaround must follow the
1284conventions listed below.
1285
1286The errata workaround must be authored as two separate functions:
1287
1288- One that checks for errata. This function must determine whether that errata
1289 applies to the current CPU. Typically this involves matching the current
1290 CPUs revision and variant against a value that's known to be affected by the
1291 errata. If the function determines that the errata applies to this CPU, it
1292 must return ``ERRATA_APPLIES``; otherwise, it must return
1293 ``ERRATA_NOT_APPLIES``. The utility functions ``cpu_get_rev_var`` and
1294 ``cpu_rev_var_ls`` functions may come in handy for this purpose.
1295
1296For an errata identified as ``E``, the check function must be named
1297``check_errata_E``.
1298
1299This function will be invoked at different times, both from assembly and from
1300C run time. Therefore it must follow AAPCS, and must not use stack.
1301
1302- Another one that applies the errata workaround. This function would call the
1303 check function described above, and applies errata workaround if required.
1304
1305CPU drivers that apply errata workaround can optionally implement an assembly
1306function that report the status of errata workarounds pertaining to that CPU.
1307For a driver that registers the CPU, for example, ``cpux`` via. ``declare_cpu_ops``
1308macro, the errata reporting function, if it exists, must be named
1309``cpux_errata_report``. This function will always be called with MMU enabled; it
1310must follow AAPCS and may use stack.
1311
1312In a debug build of ARM Trusted Firmware, on a CPU that comes out of reset, both
1313BL1 and the run time firmware (BL31 in AArch64, and BL32 in AArch32) will invoke
1314errata status reporting function, if one exists, for that type of CPU.
1315
1316To report the status of each errata workaround, the function shall use the
1317assembler macro ``report_errata``, passing it:
1318
1319- The build option that enables the errata;
1320
1321- The name of the CPU: this must be the same identifier that CPU driver
1322 registered itself with, using ``declare_cpu_ops``;
1323
1324- And the errata identifier: the identifier must match what's used in the
1325 errata's check function described above.
1326
1327The errata status reporting function will be called once per CPU type/errata
1328combination during the software's active life time.
1329
1330It's expected that whenever an errata workaround is submitted to ARM Trusted
1331Firmware, the errata reporting function is appropriately extended to report its
1332status as well.
1333
1334Reporting the status of errata workaround is for informational purpose only; it
1335has no functional significance.
1336
1337Memory layout of BL images
1338--------------------------
1339
1340Each bootloader image can be divided in 2 parts:
1341
1342- the static contents of the image. These are data actually stored in the
1343 binary on the disk. In the ELF terminology, they are called ``PROGBITS``
1344 sections;
1345
1346- the run-time contents of the image. These are data that don't occupy any
1347 space in the binary on the disk. The ELF binary just contains some
1348 metadata indicating where these data will be stored at run-time and the
1349 corresponding sections need to be allocated and initialized at run-time.
1350 In the ELF terminology, they are called ``NOBITS`` sections.
1351
1352All PROGBITS sections are grouped together at the beginning of the image,
1353followed by all NOBITS sections. This is true for all Trusted Firmware images
1354and it is governed by the linker scripts. This ensures that the raw binary
1355images are as small as possible. If a NOBITS section was inserted in between
1356PROGBITS sections then the resulting binary file would contain zero bytes in
1357place of this NOBITS section, making the image unnecessarily bigger. Smaller
1358images allow faster loading from the FIP to the main memory.
1359
1360Linker scripts and symbols
1361~~~~~~~~~~~~~~~~~~~~~~~~~~
1362
1363Each bootloader stage image layout is described by its own linker script. The
1364linker scripts export some symbols into the program symbol table. Their values
1365correspond to particular addresses. The trusted firmware code can refer to these
1366symbols to figure out the image memory layout.
1367
1368Linker symbols follow the following naming convention in the trusted firmware.
1369
1370- ``__<SECTION>_START__``
1371
1372 Start address of a given section named ``<SECTION>``.
1373
1374- ``__<SECTION>_END__``
1375
1376 End address of a given section named ``<SECTION>``. If there is an alignment
1377 constraint on the section's end address then ``__<SECTION>_END__`` corresponds
1378 to the end address of the section's actual contents, rounded up to the right
1379 boundary. Refer to the value of ``__<SECTION>_UNALIGNED_END__`` to know the
1380 actual end address of the section's contents.
1381
1382- ``__<SECTION>_UNALIGNED_END__``
1383
1384 End address of a given section named ``<SECTION>`` without any padding or
1385 rounding up due to some alignment constraint.
1386
1387- ``__<SECTION>_SIZE__``
1388
1389 Size (in bytes) of a given section named ``<SECTION>``. If there is an
1390 alignment constraint on the section's end address then ``__<SECTION>_SIZE__``
1391 corresponds to the size of the section's actual contents, rounded up to the
1392 right boundary. In other words, ``__<SECTION>_SIZE__ = __<SECTION>_END__ - _<SECTION>_START__``. Refer to the value of ``__<SECTION>_UNALIGNED_SIZE__``
1393 to know the actual size of the section's contents.
1394
1395- ``__<SECTION>_UNALIGNED_SIZE__``
1396
1397 Size (in bytes) of a given section named ``<SECTION>`` without any padding or
1398 rounding up due to some alignment constraint. In other words,
1399 ``__<SECTION>_UNALIGNED_SIZE__ = __<SECTION>_UNALIGNED_END__ - __<SECTION>_START__``.
1400
1401Some of the linker symbols are mandatory as the trusted firmware code relies on
1402them to be defined. They are listed in the following subsections. Some of them
1403must be provided for each bootloader stage and some are specific to a given
1404bootloader stage.
1405
1406The linker scripts define some extra, optional symbols. They are not actually
1407used by any code but they help in understanding the bootloader images' memory
1408layout as they are easy to spot in the link map files.
1409
1410Common linker symbols
1411^^^^^^^^^^^^^^^^^^^^^
1412
1413All BL images share the following requirements:
1414
1415- The BSS section must be zero-initialised before executing any C code.
1416- The coherent memory section (if enabled) must be zero-initialised as well.
1417- The MMU setup code needs to know the extents of the coherent and read-only
1418 memory regions to set the right memory attributes. When
1419 ``SEPARATE_CODE_AND_RODATA=1``, it needs to know more specifically how the
1420 read-only memory region is divided between code and data.
1421
1422The following linker symbols are defined for this purpose:
1423
1424- ``__BSS_START__``
1425- ``__BSS_SIZE__``
1426- ``__COHERENT_RAM_START__`` Must be aligned on a page-size boundary.
1427- ``__COHERENT_RAM_END__`` Must be aligned on a page-size boundary.
1428- ``__COHERENT_RAM_UNALIGNED_SIZE__``
1429- ``__RO_START__``
1430- ``__RO_END__``
1431- ``__TEXT_START__``
1432- ``__TEXT_END__``
1433- ``__RODATA_START__``
1434- ``__RODATA_END__``
1435
1436BL1's linker symbols
1437^^^^^^^^^^^^^^^^^^^^
1438
1439BL1 being the ROM image, it has additional requirements. BL1 resides in ROM and
1440it is entirely executed in place but it needs some read-write memory for its
1441mutable data. Its ``.data`` section (i.e. its allocated read-write data) must be
1442relocated from ROM to RAM before executing any C code.
1443
1444The following additional linker symbols are defined for BL1:
1445
1446- ``__BL1_ROM_END__`` End address of BL1's ROM contents, covering its code
1447 and ``.data`` section in ROM.
1448- ``__DATA_ROM_START__`` Start address of the ``.data`` section in ROM. Must be
1449 aligned on a 16-byte boundary.
1450- ``__DATA_RAM_START__`` Address in RAM where the ``.data`` section should be
1451 copied over. Must be aligned on a 16-byte boundary.
1452- ``__DATA_SIZE__`` Size of the ``.data`` section (in ROM or RAM).
1453- ``__BL1_RAM_START__`` Start address of BL1 read-write data.
1454- ``__BL1_RAM_END__`` End address of BL1 read-write data.
1455
1456How to choose the right base addresses for each bootloader stage image
1457~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1458
1459There is currently no support for dynamic image loading in the Trusted Firmware.
1460This means that all bootloader images need to be linked against their ultimate
1461runtime locations and the base addresses of each image must be chosen carefully
1462such that images don't overlap each other in an undesired way. As the code
1463grows, the base addresses might need adjustments to cope with the new memory
1464layout.
1465
1466The memory layout is completely specific to the platform and so there is no
1467general recipe for choosing the right base addresses for each bootloader image.
1468However, there are tools to aid in understanding the memory layout. These are
1469the link map files: ``build/<platform>/<build-type>/bl<x>/bl<x>.map``, with ``<x>``
1470being the stage bootloader. They provide a detailed view of the memory usage of
1471each image. Among other useful information, they provide the end address of
1472each image.
1473
1474- ``bl1.map`` link map file provides ``__BL1_RAM_END__`` address.
1475- ``bl2.map`` link map file provides ``__BL2_END__`` address.
1476- ``bl31.map`` link map file provides ``__BL31_END__`` address.
1477- ``bl32.map`` link map file provides ``__BL32_END__`` address.
1478
1479For each bootloader image, the platform code must provide its start address
1480as well as a limit address that it must not overstep. The latter is used in the
1481linker scripts to check that the image doesn't grow past that address. If that
1482happens, the linker will issue a message similar to the following:
1483
1484::
1485
1486 aarch64-none-elf-ld: BLx has exceeded its limit.
1487
1488Additionally, if the platform memory layout implies some image overlaying like
1489on FVP, BL31 and TSP need to know the limit address that their PROGBITS
1490sections must not overstep. The platform code must provide those.
1491
1492When LOAD\_IMAGE\_V2 is disabled, Trusted Firmware provides a mechanism to
1493verify at boot time that the memory to load a new image is free to prevent
1494overwriting a previously loaded image. For this mechanism to work, the platform
1495must specify the memory available in the system as regions, where each region
1496consists of base address, total size and the free area within it (as defined
1497in the ``meminfo_t`` structure). Trusted Firmware retrieves these memory regions
1498by calling the corresponding platform API:
1499
1500- ``meminfo_t *bl1_plat_sec_mem_layout(void)``
1501- ``meminfo_t *bl2_plat_sec_mem_layout(void)``
1502- ``void bl2_plat_get_scp_bl2_meminfo(meminfo_t *scp_bl2_meminfo)``
1503- ``void bl2_plat_get_bl32_meminfo(meminfo_t *bl32_meminfo)``
1504- ``void bl2_plat_get_bl33_meminfo(meminfo_t *bl33_meminfo)``
1505
1506For example, in the case of BL1 loading BL2, ``bl1_plat_sec_mem_layout()`` will
1507return the region defined by the platform where BL1 intends to load BL2. The
1508``load_image()`` function will check that the memory where BL2 will be loaded is
1509within the specified region and marked as free.
1510
1511The actual number of regions and their base addresses and sizes is platform
1512specific. The platform may return the same region or define a different one for
1513each API. However, the overlap verification mechanism applies only to a single
1514region. Hence, it is the platform responsibility to guarantee that different
1515regions do not overlap, or that if they do, the overlapping images are not
1516accessed at the same time. This could be used, for example, to load temporary
1517images (e.g. certificates) or firmware images prior to being transfered to its
1518corresponding processor (e.g. the SCP BL2 image).
1519
1520To reduce fragmentation and simplify the tracking of free memory, all the free
1521memory within a region is always located in one single buffer defined by its
1522base address and size. Trusted Firmware implements a top/bottom load approach:
1523after a new image is loaded, it checks how much memory remains free above and
1524below the image. The smallest area is marked as unavailable, while the larger
1525area becomes the new free memory buffer. Platforms should take this behaviour
1526into account when defining the base address for each of the images. For example,
1527if an image is loaded near the middle of the region, small changes in image size
1528could cause a flip between a top load and a bottom load, which may result in an
1529unexpected memory layout.
1530
1531The following diagram is an example of an image loaded in the bottom part of
1532the memory region. The region is initially free (nothing has been loaded yet):
1533
1534::
1535
1536 Memory region
1537 +----------+
1538 | |
1539 | | <<<<<<<<<<<<< Free
1540 | |
1541 |----------| +------------+
1542 | image | <<<<<<<<<<<<< | image |
1543 |----------| +------------+
1544 | xxxxxxxx | <<<<<<<<<<<<< Marked as unavailable
1545 +----------+
1546
1547And the following diagram is an example of an image loaded in the top part:
1548
1549::
1550
1551 Memory region
1552 +----------+
1553 | xxxxxxxx | <<<<<<<<<<<<< Marked as unavailable
1554 |----------| +------------+
1555 | image | <<<<<<<<<<<<< | image |
1556 |----------| +------------+
1557 | |
1558 | | <<<<<<<<<<<<< Free
1559 | |
1560 +----------+
1561
1562When LOAD\_IMAGE\_V2 is enabled, Trusted Firmware does not provide any mechanism
1563to verify at boot time that the memory to load a new image is free to prevent
1564overwriting a previously loaded image. The platform must specify the memory
1565available in the system for all the relevant BL images to be loaded.
1566
1567For example, in the case of BL1 loading BL2, ``bl1_plat_sec_mem_layout()`` will
1568return the region defined by the platform where BL1 intends to load BL2. The
1569``load_image()`` function performs bounds check for the image size based on the
1570base and maximum image size provided by the platforms. Platforms must take
1571this behaviour into account when defining the base/size for each of the images.
1572
1573Memory layout on ARM development platforms
1574^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1575
1576The following list describes the memory layout on the ARM development platforms:
1577
1578- A 4KB page of shared memory is used for communication between Trusted
1579 Firmware and the platform's power controller. This is located at the base of
1580 Trusted SRAM. The amount of Trusted SRAM available to load the bootloader
1581 images is reduced by the size of the shared memory.
1582
1583 The shared memory is used to store the CPUs' entrypoint mailbox. On Juno,
1584 this is also used for the MHU payload when passing messages to and from the
1585 SCP.
1586
1587- On FVP, BL1 is originally sitting in the Trusted ROM at address ``0x0``. On
1588 Juno, BL1 resides in flash memory at address ``0x0BEC0000``. BL1 read-write
1589 data are relocated to the top of Trusted SRAM at runtime.
1590
1591- EL3 Runtime Software, BL31 for AArch64 and BL32 for AArch32 (e.g. SP\_MIN),
1592 is loaded at the top of the Trusted SRAM, such that its NOBITS sections will
1593 overwrite BL1 R/W data. This implies that BL1 global variables remain valid
1594 only until execution reaches the EL3 Runtime Software entry point during a
1595 cold boot.
1596
1597- BL2 is loaded below EL3 Runtime Software.
1598
1599- On Juno, SCP\_BL2 is loaded temporarily into the EL3 Runtime Software memory
1600 region and transfered to the SCP before being overwritten by EL3 Runtime
1601 Software.
1602
1603- BL32 (for AArch64) can be loaded in one of the following locations:
1604
1605 - Trusted SRAM
1606 - Trusted DRAM (FVP only)
1607 - Secure region of DRAM (top 16MB of DRAM configured by the TrustZone
1608 controller)
1609
1610 When BL32 (for AArch64) is loaded into Trusted SRAM, its NOBITS sections
1611 are allowed to overlay BL2. This memory layout is designed to give the
1612 BL32 image as much memory as possible when it is loaded into Trusted SRAM.
1613
1614When LOAD\_IMAGE\_V2 is disabled the memory regions for the overlap detection
1615mechanism at boot time are defined as follows (shown per API):
1616
1617- ``meminfo_t *bl1_plat_sec_mem_layout(void)``
1618
1619 This region corresponds to the whole Trusted SRAM except for the shared
1620 memory at the base. This region is initially free. At boot time, BL1 will
1621 mark the BL1(rw) section within this region as occupied. The BL1(rw) section
1622 is placed at the top of Trusted SRAM.
1623
1624- ``meminfo_t *bl2_plat_sec_mem_layout(void)``
1625
1626 This region corresponds to the whole Trusted SRAM as defined by
1627 ``bl1_plat_sec_mem_layout()``, but with the BL1(rw) section marked as
1628 occupied. This memory region is used to check that BL2 and BL31 do not
1629 overlap with each other. BL2\_BASE and BL1\_RW\_BASE are carefully chosen so
1630 that the memory for BL31 is top loaded above BL2.
1631
1632- ``void bl2_plat_get_scp_bl2_meminfo(meminfo_t *scp_bl2_meminfo)``
1633
1634 This region is an exact copy of the region defined by
1635 ``bl2_plat_sec_mem_layout()``. Being a disconnected copy means that all the
1636 changes made to this region by the Trusted Firmware will not be propagated.
1637 This approach is valid because the SCP BL2 image is loaded temporarily
1638 while it is being transferred to the SCP, so this memory is reused
1639 afterwards.
1640
1641- ``void bl2_plat_get_bl32_meminfo(meminfo_t *bl32_meminfo)``
1642
1643 This region depends on the location of the BL32 image. Currently, ARM
1644 platforms support three different locations (detailed below): Trusted SRAM,
1645 Trusted DRAM and the TZC-Secured DRAM.
1646
1647- ``void bl2_plat_get_bl33_meminfo(meminfo_t *bl33_meminfo)``
1648
1649 This region corresponds to the Non-Secure DDR-DRAM, excluding the
1650 TZC-Secured area.
1651
1652The location of the BL32 image will result in different memory maps. This is
1653illustrated for both FVP and Juno in the following diagrams, using the TSP as
1654an example.
1655
1656Note: Loading the BL32 image in TZC secured DRAM doesn't change the memory
1657layout of the other images in Trusted SRAM.
1658
1659**FVP with TSP in Trusted SRAM (default option):**
1660(These diagrams only cover the AArch64 case)
1661
1662::
1663
1664 Trusted SRAM
1665 0x04040000 +----------+ loaded by BL2 ------------------
1666 | BL1 (rw) | <<<<<<<<<<<<< | BL31 NOBITS |
1667 |----------| <<<<<<<<<<<<< |----------------|
1668 | | <<<<<<<<<<<<< | BL31 PROGBITS |
1669 |----------| ------------------
1670 | BL2 | <<<<<<<<<<<<< | BL32 NOBITS |
1671 |----------| <<<<<<<<<<<<< |----------------|
1672 | | <<<<<<<<<<<<< | BL32 PROGBITS |
1673 0x04001000 +----------+ ------------------
1674 | Shared |
1675 0x04000000 +----------+
1676
1677 Trusted ROM
1678 0x04000000 +----------+
1679 | BL1 (ro) |
1680 0x00000000 +----------+
1681
1682**FVP with TSP in Trusted DRAM:**
1683
1684::
1685
1686 Trusted DRAM
1687 0x08000000 +----------+
1688 | BL32 |
1689 0x06000000 +----------+
1690
1691 Trusted SRAM
1692 0x04040000 +----------+ loaded by BL2 ------------------
1693 | BL1 (rw) | <<<<<<<<<<<<< | BL31 NOBITS |
1694 |----------| <<<<<<<<<<<<< |----------------|
1695 | | <<<<<<<<<<<<< | BL31 PROGBITS |
1696 |----------| ------------------
1697 | BL2 |
1698 |----------|
1699 | |
1700 0x04001000 +----------+
1701 | Shared |
1702 0x04000000 +----------+
1703
1704 Trusted ROM
1705 0x04000000 +----------+
1706 | BL1 (ro) |
1707 0x00000000 +----------+
1708
1709**FVP with TSP in TZC-Secured DRAM:**
1710
1711::
1712
1713 DRAM
1714 0xffffffff +----------+
1715 | BL32 | (secure)
1716 0xff000000 +----------+
1717 | |
1718 : : (non-secure)
1719 | |
1720 0x80000000 +----------+
1721
1722 Trusted SRAM
1723 0x04040000 +----------+ loaded by BL2 ------------------
1724 | BL1 (rw) | <<<<<<<<<<<<< | BL31 NOBITS |
1725 |----------| <<<<<<<<<<<<< |----------------|
1726 | | <<<<<<<<<<<<< | BL31 PROGBITS |
1727 |----------| ------------------
1728 | BL2 |
1729 |----------|
1730 | |
1731 0x04001000 +----------+
1732 | Shared |
1733 0x04000000 +----------+
1734
1735 Trusted ROM
1736 0x04000000 +----------+
1737 | BL1 (ro) |
1738 0x00000000 +----------+
1739
1740**Juno with BL32 in Trusted SRAM (default option):**
1741
1742::
1743
1744 Flash0
1745 0x0C000000 +----------+
1746 : :
1747 0x0BED0000 |----------|
1748 | BL1 (ro) |
1749 0x0BEC0000 |----------|
1750 : :
1751 0x08000000 +----------+ BL31 is loaded
1752 after SCP_BL2 has
1753 Trusted SRAM been sent to SCP
1754 0x04040000 +----------+ loaded by BL2 ------------------
1755 | BL1 (rw) | <<<<<<<<<<<<< | BL31 NOBITS |
1756 |----------| <<<<<<<<<<<<< |----------------|
1757 | SCP_BL2 | <<<<<<<<<<<<< | BL31 PROGBITS |
1758 |----------| ------------------
1759 | BL2 | <<<<<<<<<<<<< | BL32 NOBITS |
1760 |----------| <<<<<<<<<<<<< |----------------|
1761 | | <<<<<<<<<<<<< | BL32 PROGBITS |
1762 0x04001000 +----------+ ------------------
1763 | MHU |
1764 0x04000000 +----------+
1765
1766**Juno with BL32 in TZC-secured DRAM:**
1767
1768::
1769
1770 DRAM
1771 0xFFE00000 +----------+
1772 | BL32 | (secure)
1773 0xFF000000 |----------|
1774 | |
1775 : : (non-secure)
1776 | |
1777 0x80000000 +----------+
1778
1779 Flash0
1780 0x0C000000 +----------+
1781 : :
1782 0x0BED0000 |----------|
1783 | BL1 (ro) |
1784 0x0BEC0000 |----------|
1785 : :
1786 0x08000000 +----------+ BL31 is loaded
1787 after SCP_BL2 has
1788 Trusted SRAM been sent to SCP
1789 0x04040000 +----------+ loaded by BL2 ------------------
1790 | BL1 (rw) | <<<<<<<<<<<<< | BL31 NOBITS |
1791 |----------| <<<<<<<<<<<<< |----------------|
1792 | SCP_BL2 | <<<<<<<<<<<<< | BL31 PROGBITS |
1793 |----------| ------------------
1794 | BL2 |
1795 |----------|
1796 | |
1797 0x04001000 +----------+
1798 | MHU |
1799 0x04000000 +----------+
1800
1801Firmware Image Package (FIP)
1802----------------------------
1803
1804Using a Firmware Image Package (FIP) allows for packing bootloader images (and
1805potentially other payloads) into a single archive that can be loaded by the ARM
1806Trusted Firmware from non-volatile platform storage. A driver to load images
1807from a FIP has been added to the storage layer and allows a package to be read
1808from supported platform storage. A tool to create Firmware Image Packages is
1809also provided and described below.
1810
1811Firmware Image Package layout
1812~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1813
1814The FIP layout consists of a table of contents (ToC) followed by payload data.
1815The ToC itself has a header followed by one or more table entries. The ToC is
1816terminated by an end marker entry. All ToC entries describe some payload data
1817that has been appended to the end of the binary package. With the information
1818provided in the ToC entry the corresponding payload data can be retrieved.
1819
1820::
1821
1822 ------------------
1823 | ToC Header |
1824 |----------------|
1825 | ToC Entry 0 |
1826 |----------------|
1827 | ToC Entry 1 |
1828 |----------------|
1829 | ToC End Marker |
1830 |----------------|
1831 | |
1832 | Data 0 |
1833 | |
1834 |----------------|
1835 | |
1836 | Data 1 |
1837 | |
1838 ------------------
1839
1840The ToC header and entry formats are described in the header file
1841``include/tools_share/firmware_image_package.h``. This file is used by both the
1842tool and the ARM Trusted firmware.
1843
1844The ToC header has the following fields:
1845
1846::
1847
1848 `name`: The name of the ToC. This is currently used to validate the header.
1849 `serial_number`: A non-zero number provided by the creation tool
1850 `flags`: Flags associated with this data.
1851 Bits 0-31: Reserved
1852 Bits 32-47: Platform defined
1853 Bits 48-63: Reserved
1854
1855A ToC entry has the following fields:
1856
1857::
1858
1859 `uuid`: All files are referred to by a pre-defined Universally Unique
1860 IDentifier [UUID] . The UUIDs are defined in
1861 `include/tools_share/firmware_image_package.h`. The platform translates
1862 the requested image name into the corresponding UUID when accessing the
1863 package.
1864 `offset_address`: The offset address at which the corresponding payload data
1865 can be found. The offset is calculated from the ToC base address.
1866 `size`: The size of the corresponding payload data in bytes.
Etienne Carriere7421bf12017-08-23 15:43:33 +02001867 `flags`: Flags associated with this entry. None are yet defined.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01001868
1869Firmware Image Package creation tool
1870~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1871
1872The FIP creation tool can be used to pack specified images into a binary package
1873that can be loaded by the ARM Trusted Firmware from platform storage. The tool
1874currently only supports packing bootloader images. Additional image definitions
1875can be added to the tool as required.
1876
1877The tool can be found in ``tools/fiptool``.
1878
1879Loading from a Firmware Image Package (FIP)
1880~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1881
1882The Firmware Image Package (FIP) driver can load images from a binary package on
1883non-volatile platform storage. For the ARM development platforms, this is
1884currently NOR FLASH.
1885
1886Bootloader images are loaded according to the platform policy as specified by
1887the function ``plat_get_image_source()``. For the ARM development platforms, this
1888means the platform will attempt to load images from a Firmware Image Package
1889located at the start of NOR FLASH0.
1890
1891The ARM development platforms' policy is to only allow loading of a known set of
1892images. The platform policy can be modified to allow additional images.
1893
1894Use of coherent memory in Trusted Firmware
1895------------------------------------------
1896
1897There might be loss of coherency when physical memory with mismatched
1898shareability, cacheability and memory attributes is accessed by multiple CPUs
1899(refer to section B2.9 of `ARM ARM`_ for more details). This possibility occurs
1900in Trusted Firmware during power up/down sequences when coherency, MMU and
1901caches are turned on/off incrementally.
1902
1903Trusted Firmware defines coherent memory as a region of memory with Device
1904nGnRE attributes in the translation tables. The translation granule size in
1905Trusted Firmware is 4KB. This is the smallest possible size of the coherent
1906memory region.
1907
1908By default, all data structures which are susceptible to accesses with
1909mismatched attributes from various CPUs are allocated in a coherent memory
1910region (refer to section 2.1 of `Porting Guide`_). The coherent memory region
1911accesses are Outer Shareable, non-cacheable and they can be accessed
1912with the Device nGnRE attributes when the MMU is turned on. Hence, at the
1913expense of at least an extra page of memory, Trusted Firmware is able to work
1914around coherency issues due to mismatched memory attributes.
1915
1916The alternative to the above approach is to allocate the susceptible data
1917structures in Normal WriteBack WriteAllocate Inner shareable memory. This
1918approach requires the data structures to be designed so that it is possible to
1919work around the issue of mismatched memory attributes by performing software
1920cache maintenance on them.
1921
1922Disabling the use of coherent memory in Trusted Firmware
1923~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1924
1925It might be desirable to avoid the cost of allocating coherent memory on
1926platforms which are memory constrained. Trusted Firmware enables inclusion of
1927coherent memory in firmware images through the build flag ``USE_COHERENT_MEM``.
1928This flag is enabled by default. It can be disabled to choose the second
1929approach described above.
1930
1931The below sections analyze the data structures allocated in the coherent memory
1932region and the changes required to allocate them in normal memory.
1933
1934Coherent memory usage in PSCI implementation
1935~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1936
1937The ``psci_non_cpu_pd_nodes`` data structure stores the platform's power domain
1938tree information for state management of power domains. By default, this data
1939structure is allocated in the coherent memory region in the Trusted Firmware
1940because it can be accessed by multple CPUs, either with caches enabled or
1941disabled.
1942
1943.. code:: c
1944
1945 typedef struct non_cpu_pwr_domain_node {
1946 /*
1947 * Index of the first CPU power domain node level 0 which has this node
1948 * as its parent.
1949 */
1950 unsigned int cpu_start_idx;
1951
1952 /*
1953 * Number of CPU power domains which are siblings of the domain indexed
1954 * by 'cpu_start_idx' i.e. all the domains in the range 'cpu_start_idx
1955 * -> cpu_start_idx + ncpus' have this node as their parent.
1956 */
1957 unsigned int ncpus;
1958
1959 /*
1960 * Index of the parent power domain node.
1961 * TODO: Figure out whether to whether using pointer is more efficient.
1962 */
1963 unsigned int parent_node;
1964
1965 plat_local_state_t local_state;
1966
1967 unsigned char level;
1968
1969 /* For indexing the psci_lock array*/
1970 unsigned char lock_index;
1971 } non_cpu_pd_node_t;
1972
1973In order to move this data structure to normal memory, the use of each of its
1974fields must be analyzed. Fields like ``cpu_start_idx``, ``ncpus``, ``parent_node``
1975``level`` and ``lock_index`` are only written once during cold boot. Hence removing
1976them from coherent memory involves only doing a clean and invalidate of the
1977cache lines after these fields are written.
1978
1979The field ``local_state`` can be concurrently accessed by multiple CPUs in
1980different cache states. A Lamport's Bakery lock ``psci_locks`` is used to ensure
1981mutual exlusion to this field and a clean and invalidate is needed after it
1982is written.
1983
1984Bakery lock data
1985~~~~~~~~~~~~~~~~
1986
1987The bakery lock data structure ``bakery_lock_t`` is allocated in coherent memory
1988and is accessed by multiple CPUs with mismatched attributes. ``bakery_lock_t`` is
1989defined as follows:
1990
1991.. code:: c
1992
1993 typedef struct bakery_lock {
1994 /*
1995 * The lock_data is a bit-field of 2 members:
1996 * Bit[0] : choosing. This field is set when the CPU is
1997 * choosing its bakery number.
1998 * Bits[1 - 15] : number. This is the bakery number allocated.
1999 */
2000 volatile uint16_t lock_data[BAKERY_LOCK_MAX_CPUS];
2001 } bakery_lock_t;
2002
2003It is a characteristic of Lamport's Bakery algorithm that the volatile per-CPU
2004fields can be read by all CPUs but only written to by the owning CPU.
2005
2006Depending upon the data cache line size, the per-CPU fields of the
2007``bakery_lock_t`` structure for multiple CPUs may exist on a single cache line.
2008These per-CPU fields can be read and written during lock contention by multiple
2009CPUs with mismatched memory attributes. Since these fields are a part of the
2010lock implementation, they do not have access to any other locking primitive to
2011safeguard against the resulting coherency issues. As a result, simple software
2012cache maintenance is not enough to allocate them in coherent memory. Consider
2013the following example.
2014
2015CPU0 updates its per-CPU field with data cache enabled. This write updates a
2016local cache line which contains a copy of the fields for other CPUs as well. Now
2017CPU1 updates its per-CPU field of the ``bakery_lock_t`` structure with data cache
2018disabled. CPU1 then issues a DCIVAC operation to invalidate any stale copies of
2019its field in any other cache line in the system. This operation will invalidate
2020the update made by CPU0 as well.
2021
2022To use bakery locks when ``USE_COHERENT_MEM`` is disabled, the lock data structure
2023has been redesigned. The changes utilise the characteristic of Lamport's Bakery
2024algorithm mentioned earlier. The bakery\_lock structure only allocates the memory
2025for a single CPU. The macro ``DEFINE_BAKERY_LOCK`` allocates all the bakery locks
2026needed for a CPU into a section ``bakery_lock``. The linker allocates the memory
2027for other cores by using the total size allocated for the bakery\_lock section
2028and multiplying it with (PLATFORM\_CORE\_COUNT - 1). This enables software to
2029perform software cache maintenance on the lock data structure without running
2030into coherency issues associated with mismatched attributes.
2031
2032The bakery lock data structure ``bakery_info_t`` is defined for use when
2033``USE_COHERENT_MEM`` is disabled as follows:
2034
2035.. code:: c
2036
2037 typedef struct bakery_info {
2038 /*
2039 * The lock_data is a bit-field of 2 members:
2040 * Bit[0] : choosing. This field is set when the CPU is
2041 * choosing its bakery number.
2042 * Bits[1 - 15] : number. This is the bakery number allocated.
2043 */
2044 volatile uint16_t lock_data;
2045 } bakery_info_t;
2046
2047The ``bakery_info_t`` represents a single per-CPU field of one lock and
2048the combination of corresponding ``bakery_info_t`` structures for all CPUs in the
2049system represents the complete bakery lock. The view in memory for a system
2050with n bakery locks are:
2051
2052::
2053
2054 bakery_lock section start
2055 |----------------|
2056 | `bakery_info_t`| <-- Lock_0 per-CPU field
2057 | Lock_0 | for CPU0
2058 |----------------|
2059 | `bakery_info_t`| <-- Lock_1 per-CPU field
2060 | Lock_1 | for CPU0
2061 |----------------|
2062 | .... |
2063 |----------------|
2064 | `bakery_info_t`| <-- Lock_N per-CPU field
2065 | Lock_N | for CPU0
2066 ------------------
2067 | XXXXX |
2068 | Padding to |
2069 | next Cache WB | <--- Calculate PERCPU_BAKERY_LOCK_SIZE, allocate
2070 | Granule | continuous memory for remaining CPUs.
2071 ------------------
2072 | `bakery_info_t`| <-- Lock_0 per-CPU field
2073 | Lock_0 | for CPU1
2074 |----------------|
2075 | `bakery_info_t`| <-- Lock_1 per-CPU field
2076 | Lock_1 | for CPU1
2077 |----------------|
2078 | .... |
2079 |----------------|
2080 | `bakery_info_t`| <-- Lock_N per-CPU field
2081 | Lock_N | for CPU1
2082 ------------------
2083 | XXXXX |
2084 | Padding to |
2085 | next Cache WB |
2086 | Granule |
2087 ------------------
2088
2089Consider a system of 2 CPUs with 'N' bakery locks as shown above. For an
2090operation on Lock\_N, the corresponding ``bakery_info_t`` in both CPU0 and CPU1
2091``bakery_lock`` section need to be fetched and appropriate cache operations need
2092to be performed for each access.
2093
2094On ARM Platforms, bakery locks are used in psci (``psci_locks``) and power controller
2095driver (``arm_lock``).
2096
2097Non Functional Impact of removing coherent memory
2098~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2099
2100Removal of the coherent memory region leads to the additional software overhead
2101of performing cache maintenance for the affected data structures. However, since
2102the memory where the data structures are allocated is cacheable, the overhead is
2103mostly mitigated by an increase in performance.
2104
2105There is however a performance impact for bakery locks, due to:
2106
2107- Additional cache maintenance operations, and
2108- Multiple cache line reads for each lock operation, since the bakery locks
2109 for each CPU are distributed across different cache lines.
2110
2111The implementation has been optimized to minimize this additional overhead.
2112Measurements indicate that when bakery locks are allocated in Normal memory, the
2113minimum latency of acquiring a lock is on an average 3-4 micro seconds whereas
2114in Device memory the same is 2 micro seconds. The measurements were done on the
2115Juno ARM development platform.
2116
2117As mentioned earlier, almost a page of memory can be saved by disabling
2118``USE_COHERENT_MEM``. Each platform needs to consider these trade-offs to decide
2119whether coherent memory should be used. If a platform disables
2120``USE_COHERENT_MEM`` and needs to use bakery locks in the porting layer, it can
2121optionally define macro ``PLAT_PERCPU_BAKERY_LOCK_SIZE`` (see the
2122`Porting Guide`_). Refer to the reference platform code for examples.
2123
2124Isolating code and read-only data on separate memory pages
2125----------------------------------------------------------
2126
2127In the ARMv8 VMSA, translation table entries include fields that define the
2128properties of the target memory region, such as its access permissions. The
2129smallest unit of memory that can be addressed by a translation table entry is
2130a memory page. Therefore, if software needs to set different permissions on two
2131memory regions then it needs to map them using different memory pages.
2132
2133The default memory layout for each BL image is as follows:
2134
2135::
2136
2137 | ... |
2138 +-------------------+
2139 | Read-write data |
2140 +-------------------+ Page boundary
2141 | <Padding> |
2142 +-------------------+
2143 | Exception vectors |
2144 +-------------------+ 2 KB boundary
2145 | <Padding> |
2146 +-------------------+
2147 | Read-only data |
2148 +-------------------+
2149 | Code |
2150 +-------------------+ BLx_BASE
2151
2152Note: The 2KB alignment for the exception vectors is an architectural
2153requirement.
2154
2155The read-write data start on a new memory page so that they can be mapped with
2156read-write permissions, whereas the code and read-only data below are configured
2157as read-only.
2158
2159However, the read-only data are not aligned on a page boundary. They are
2160contiguous to the code. Therefore, the end of the code section and the beginning
2161of the read-only data one might share a memory page. This forces both to be
2162mapped with the same memory attributes. As the code needs to be executable, this
2163means that the read-only data stored on the same memory page as the code are
2164executable as well. This could potentially be exploited as part of a security
2165attack.
2166
2167TF provides the build flag ``SEPARATE_CODE_AND_RODATA`` to isolate the code and
2168read-only data on separate memory pages. This in turn allows independent control
2169of the access permissions for the code and read-only data. In this case,
2170platform code gets a finer-grained view of the image layout and can
2171appropriately map the code region as executable and the read-only data as
2172execute-never.
2173
2174This has an impact on memory footprint, as padding bytes need to be introduced
2175between the code and read-only data to ensure the segragation of the two. To
2176limit the memory cost, this flag also changes the memory layout such that the
2177code and exception vectors are now contiguous, like so:
2178
2179::
2180
2181 | ... |
2182 +-------------------+
2183 | Read-write data |
2184 +-------------------+ Page boundary
2185 | <Padding> |
2186 +-------------------+
2187 | Read-only data |
2188 +-------------------+ Page boundary
2189 | <Padding> |
2190 +-------------------+
2191 | Exception vectors |
2192 +-------------------+ 2 KB boundary
2193 | <Padding> |
2194 +-------------------+
2195 | Code |
2196 +-------------------+ BLx_BASE
2197
2198With this more condensed memory layout, the separation of read-only data will
2199add zero or one page to the memory footprint of each BL image. Each platform
2200should consider the trade-off between memory footprint and security.
2201
2202This build flag is disabled by default, minimising memory footprint. On ARM
2203platforms, it is enabled.
2204
2205Performance Measurement Framework
2206---------------------------------
2207
2208The Performance Measurement Framework (PMF) facilitates collection of
2209timestamps by registered services and provides interfaces to retrieve
2210them from within the ARM Trusted Firmware. A platform can choose to
2211expose appropriate SMCs to retrieve these collected timestamps.
2212
2213By default, the global physical counter is used for the timestamp
2214value and is read via ``CNTPCT_EL0``. The framework allows to retrieve
2215timestamps captured by other CPUs.
2216
2217Timestamp identifier format
2218~~~~~~~~~~~~~~~~~~~~~~~~~~~
2219
2220A PMF timestamp is uniquely identified across the system via the
2221timestamp ID or ``tid``. The ``tid`` is composed as follows:
2222
2223::
2224
2225 Bits 0-7: The local timestamp identifier.
2226 Bits 8-9: Reserved.
2227 Bits 10-15: The service identifier.
2228 Bits 16-31: Reserved.
2229
2230#. The service identifier. Each PMF service is identified by a
2231 service name and a service identifier. Both the service name and
2232 identifier are unique within the system as a whole.
2233
2234#. The local timestamp identifier. This identifier is unique within a given
2235 service.
2236
2237Registering a PMF service
2238~~~~~~~~~~~~~~~~~~~~~~~~~
2239
2240To register a PMF service, the ``PMF_REGISTER_SERVICE()`` macro from ``pmf.h``
2241is used. The arguments required are the service name, the service ID,
2242the total number of local timestamps to be captured and a set of flags.
2243
2244The ``flags`` field can be specified as a bitwise-OR of the following values:
2245
2246::
2247
2248 PMF_STORE_ENABLE: The timestamp is stored in memory for later retrieval.
2249 PMF_DUMP_ENABLE: The timestamp is dumped on the serial console.
2250
2251The ``PMF_REGISTER_SERVICE()`` reserves memory to store captured
2252timestamps in a PMF specific linker section at build time.
2253Additionally, it defines necessary functions to capture and
2254retrieve a particular timestamp for the given service at runtime.
2255
2256The macro ``PMF_REGISTER_SERVICE()`` only enables capturing PMF
2257timestamps from within ARM Trusted Firmware. In order to retrieve
2258timestamps from outside of ARM Trusted Firmware, the
2259``PMF_REGISTER_SERVICE_SMC()`` macro must be used instead. This macro
2260accepts the same set of arguments as the ``PMF_REGISTER_SERVICE()``
2261macro but additionally supports retrieving timestamps using SMCs.
2262
2263Capturing a timestamp
2264~~~~~~~~~~~~~~~~~~~~~
2265
2266PMF timestamps are stored in a per-service timestamp region. On a
2267system with multiple CPUs, each timestamp is captured and stored
2268in a per-CPU cache line aligned memory region.
2269
2270Having registered the service, the ``PMF_CAPTURE_TIMESTAMP()`` macro can be
2271used to capture a timestamp at the location where it is used. The macro
2272takes the service name, a local timestamp identifier and a flag as arguments.
2273
2274The ``flags`` field argument can be zero, or ``PMF_CACHE_MAINT`` which
2275instructs PMF to do cache maintenance following the capture. Cache
2276maintenance is required if any of the service's timestamps are captured
2277with data cache disabled.
2278
2279To capture a timestamp in assembly code, the caller should use
2280``pmf_calc_timestamp_addr`` macro (defined in ``pmf_asm_macros.S``) to
2281calculate the address of where the timestamp would be stored. The
2282caller should then read ``CNTPCT_EL0`` register to obtain the timestamp
2283and store it at the determined address for later retrieval.
2284
2285Retrieving a timestamp
2286~~~~~~~~~~~~~~~~~~~~~~
2287
2288From within ARM Trusted Firmware, timestamps for individual CPUs can
2289be retrieved using either ``PMF_GET_TIMESTAMP_BY_MPIDR()`` or
2290``PMF_GET_TIMESTAMP_BY_INDEX()`` macros. These macros accept the CPU's MPIDR
2291value, or its ordinal position, respectively.
2292
2293From outside ARM Trusted Firmware, timestamps for individual CPUs can be
2294retrieved by calling into ``pmf_smc_handler()``.
2295
2296.. code:: c
2297
2298 Interface : pmf_smc_handler()
2299 Argument : unsigned int smc_fid, u_register_t x1,
2300 u_register_t x2, u_register_t x3,
2301 u_register_t x4, void *cookie,
2302 void *handle, u_register_t flags
2303 Return : uintptr_t
2304
2305 smc_fid: Holds the SMC identifier which is either `PMF_SMC_GET_TIMESTAMP_32`
2306 when the caller of the SMC is running in AArch32 mode
2307 or `PMF_SMC_GET_TIMESTAMP_64` when the caller is running in AArch64 mode.
2308 x1: Timestamp identifier.
2309 x2: The `mpidr` of the CPU for which the timestamp has to be retrieved.
2310 This can be the `mpidr` of a different core to the one initiating
2311 the SMC. In that case, service specific cache maintenance may be
2312 required to ensure the updated copy of the timestamp is returned.
2313 x3: A flags value that is either 0 or `PMF_CACHE_MAINT`. If
2314 `PMF_CACHE_MAINT` is passed, then the PMF code will perform a
2315 cache invalidate before reading the timestamp. This ensures
2316 an updated copy is returned.
2317
2318The remaining arguments, ``x4``, ``cookie``, ``handle`` and ``flags`` are unused
2319in this implementation.
2320
2321PMF code structure
2322~~~~~~~~~~~~~~~~~~
2323
2324#. ``pmf_main.c`` consists of core functions that implement service registration,
2325 initialization, storing, dumping and retrieving timestamps.
2326
2327#. ``pmf_smc.c`` contains the SMC handling for registered PMF services.
2328
2329#. ``pmf.h`` contains the public interface to Performance Measurement Framework.
2330
2331#. ``pmf_asm_macros.S`` consists of macros to facilitate capturing timestamps in
2332 assembly code.
2333
2334#. ``pmf_helpers.h`` is an internal header used by ``pmf.h``.
2335
Jeenu Viswambharanb60420a2017-08-24 15:43:44 +01002336ARMv8 Architecture Extensions
2337-----------------------------
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002338
2339ARM Trusted Firmware makes use of ARMv8 Architecture Extensions where
2340applicable. This section lists the usage of Architecture Extensions, and build
2341flags controlling them.
2342
2343In general, and unless individually mentioned, the build options
2344``ARM_ARCH_MAJOR`` and ``ARM_ARCH_MINOR`` selects the Architecture Extension to
2345target when building ARM Trusted Firmware. Subsequent ARM Architecture
2346Extensions are backward compatible with previous versions.
2347
2348The build system only requires that ``ARM_ARCH_MAJOR`` and ``ARM_ARCH_MINOR`` have a
2349valid numeric value. These build options only control whether or not
2350Architecture Extension-specific code is included in the build. Otherwise, ARM
2351Trusted Firmware targets the base ARMv8.0 architecture; i.e. as if
2352``ARM_ARCH_MAJOR`` == 8 and ``ARM_ARCH_MINOR`` == 0, which are also their respective
2353default values.
2354
2355See also the *Summary of build options* in `User Guide`_.
2356
2357For details on the Architecture Extension and available features, please refer
2358to the respective Architecture Extension Supplement.
2359
2360ARMv8.1
2361~~~~~~~
2362
2363This Architecture Extension is targeted when ``ARM_ARCH_MAJOR`` >= 8, or when
2364``ARM_ARCH_MAJOR`` == 8 and ``ARM_ARCH_MINOR`` >= 1.
2365
2366- The Compare and Swap instruction is used to implement spinlocks. Otherwise,
2367 the load-/store-exclusive instruction pair is used.
2368
2369Code Structure
2370--------------
2371
2372Trusted Firmware code is logically divided between the three boot loader
2373stages mentioned in the previous sections. The code is also divided into the
2374following categories (present as directories in the source code):
2375
2376- **Platform specific.** Choice of architecture specific code depends upon
2377 the platform.
2378- **Common code.** This is platform and architecture agnostic code.
2379- **Library code.** This code comprises of functionality commonly used by all
2380 other code. The PSCI implementation and other EL3 runtime frameworks reside
2381 as Library components.
2382- **Stage specific.** Code specific to a boot stage.
2383- **Drivers.**
2384- **Services.** EL3 runtime services (eg: SPD). Specific SPD services
2385 reside in the ``services/spd`` directory (e.g. ``services/spd/tspd``).
2386
2387Each boot loader stage uses code from one or more of the above mentioned
2388categories. Based upon the above, the code layout looks like this:
2389
2390::
2391
2392 Directory Used by BL1? Used by BL2? Used by BL31?
2393 bl1 Yes No No
2394 bl2 No Yes No
2395 bl31 No No Yes
2396 plat Yes Yes Yes
2397 drivers Yes No Yes
2398 common Yes Yes Yes
2399 lib Yes Yes Yes
2400 services No No Yes
2401
2402The build system provides a non configurable build option IMAGE\_BLx for each
2403boot loader stage (where x = BL stage). e.g. for BL1 , IMAGE\_BL1 will be
2404defined by the build system. This enables the Trusted Firmware to compile
2405certain code only for specific boot loader stages
2406
2407All assembler files have the ``.S`` extension. The linker source files for each
2408boot stage have the extension ``.ld.S``. These are processed by GCC to create the
2409linker scripts which have the extension ``.ld``.
2410
2411FDTs provide a description of the hardware platform and are used by the Linux
2412kernel at boot time. These can be found in the ``fdts`` directory.
2413
2414References
2415----------
2416
Douglas Raillard30d7b362017-06-28 16:14:55 +01002417.. [#] Trusted Board Boot Requirements CLIENT PDD (ARM DEN 0006B-5). Available
2418 under NDA through your ARM account representative.
2419.. [#] `Power State Coordination Interface PDD`_
2420.. [#] `SMC Calling Convention PDD`_
2421.. [#] `ARM Trusted Firmware Interrupt Management Design guide`_.
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002422
2423--------------
2424
Antonio Nino Diazb5d68092017-05-23 11:49:22 +01002425*Copyright (c) 2013-2017, ARM Limited and Contributors. All rights reserved.*
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002426
2427.. _Reset Design: ./reset-design.rst
2428.. _Porting Guide: ./porting-guide.rst
2429.. _Firmware Update: ./firmware-update.rst
2430.. _PSCI PDD: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf
2431.. _SMC calling convention PDD: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
2432.. _PSCI Library integration guide: ./psci-lib-integration-guide.rst
2433.. _SMCCC: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
2434.. _PSCI: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf
2435.. _Power State Coordination Interface PDD: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf
2436.. _here: ./psci-lib-integration-guide.rst
2437.. _cpu-specific-build-macros.rst: ./cpu-specific-build-macros.rst
2438.. _CPUBM: ./cpu-specific-build-macros.rst
2439.. _ARM ARM: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0487a.e/index.html
2440.. _User Guide: ./user-guide.rst
2441.. _SMC Calling Convention PDD: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
2442.. _ARM Trusted Firmware Interrupt Management Design guide: ./interrupt-framework-design.rst
Antonio Nino Diazb5d68092017-05-23 11:49:22 +01002443.. _Xlat_tables design: xlat-tables-lib-v2-design.rst
Douglas Raillardd7c21b72017-06-28 15:23:03 +01002444
2445.. |Image 1| image:: diagrams/rt-svc-descs-layout.png?raw=true