SPM: Introduce Secure Partition Manager
A Secure Partition is a software execution environment instantiated in
S-EL0 that can be used to implement simple management and security
services. Since S-EL0 is an unprivileged exception level, a Secure
Partition relies on privileged firmware e.g. ARM Trusted Firmware to be
granted access to system and processor resources. Essentially, it is a
software sandbox that runs under the control of privileged software in
the Secure World and accesses the following system resources:
- Memory and device regions in the system address map.
- PE system registers.
- A range of asynchronous exceptions e.g. interrupts.
- A range of synchronous exceptions e.g. SMC function identifiers.
A Secure Partition enables privileged firmware to implement only the
absolutely essential secure services in EL3 and instantiate the rest in
a partition. Since the partition executes in S-EL0, its implementation
cannot be overly complex.
The component in ARM Trusted Firmware responsible for managing a Secure
Partition is called the Secure Partition Manager (SPM). The SPM is
responsible for the following:
- Validating and allocating resources requested by a Secure Partition.
- Implementing a well defined interface that is used for initialising a
Secure Partition.
- Implementing a well defined interface that is used by the normal world
and other secure services for accessing the services exported by a
Secure Partition.
- Implementing a well defined interface that is used by a Secure
Partition to fulfil service requests.
- Instantiating the software execution environment required by a Secure
Partition to fulfil a service request.
Change-Id: I6f7862d6bba8732db5b73f54e789d717a35e802f
Co-authored-by: Douglas Raillard <douglas.raillard@arm.com>
Co-authored-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Co-authored-by: Achin Gupta <achin.gupta@arm.com>
Co-authored-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/services/std_svc/spm/aarch64/spm_helpers.S b/services/std_svc/spm/aarch64/spm_helpers.S
new file mode 100644
index 0000000..aa35811
--- /dev/null
+++ b/services/std_svc/spm/aarch64/spm_helpers.S
@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <asm_macros.S>
+#include "../spm_private.h"
+
+ .global spm_secure_partition_enter
+ .global spm_secure_partition_exit
+
+ /* ---------------------------------------------------------------------
+ * This function is called with SP_EL0 as stack. Here we stash our EL3
+ * callee-saved registers on to the stack as a part of saving the C
+ * runtime and enter the secure payload.
+ * 'x0' contains a pointer to the memory where the address of the C
+ * runtime context is to be saved.
+ * ---------------------------------------------------------------------
+ */
+func spm_secure_partition_enter
+ /* Make space for the registers that we're going to save */
+ mov x3, sp
+ str x3, [x0, #0]
+ sub sp, sp, #SP_C_RT_CTX_SIZE
+
+ /* Save callee-saved registers on to the stack */
+ stp x19, x20, [sp, #SP_C_RT_CTX_X19]
+ stp x21, x22, [sp, #SP_C_RT_CTX_X21]
+ stp x23, x24, [sp, #SP_C_RT_CTX_X23]
+ stp x25, x26, [sp, #SP_C_RT_CTX_X25]
+ stp x27, x28, [sp, #SP_C_RT_CTX_X27]
+ stp x29, x30, [sp, #SP_C_RT_CTX_X29]
+
+ /* ---------------------------------------------------------------------
+ * Everything is setup now. el3_exit() will use the secure context to
+ * restore to the general purpose and EL3 system registers to ERET
+ * into the secure payload.
+ * ---------------------------------------------------------------------
+ */
+ b el3_exit
+endfunc spm_secure_partition_enter
+
+ /* ---------------------------------------------------------------------
+ * This function is called with 'x0' pointing to a C runtime context
+ * saved in spm_secure_partition_enter().
+ * It restores the saved registers and jumps to that runtime with 'x0'
+ * as the new SP register. This destroys the C runtime context that had
+ * been built on the stack below the saved context by the caller. Later
+ * the second parameter 'x1' is passed as a return value to the caller.
+ * ---------------------------------------------------------------------
+ */
+func spm_secure_partition_exit
+ /* Restore the previous stack */
+ mov sp, x0
+
+ /* Restore callee-saved registers on to the stack */
+ ldp x19, x20, [x0, #(SP_C_RT_CTX_X19 - SP_C_RT_CTX_SIZE)]
+ ldp x21, x22, [x0, #(SP_C_RT_CTX_X21 - SP_C_RT_CTX_SIZE)]
+ ldp x23, x24, [x0, #(SP_C_RT_CTX_X23 - SP_C_RT_CTX_SIZE)]
+ ldp x25, x26, [x0, #(SP_C_RT_CTX_X25 - SP_C_RT_CTX_SIZE)]
+ ldp x27, x28, [x0, #(SP_C_RT_CTX_X27 - SP_C_RT_CTX_SIZE)]
+ ldp x29, x30, [x0, #(SP_C_RT_CTX_X29 - SP_C_RT_CTX_SIZE)]
+
+ /* ---------------------------------------------------------------------
+ * This should take us back to the instruction after the call to the
+ * last spm_secure_partition_enter().* Place the second parameter to x0
+ * so that the caller will see it as a return value from the original
+ * entry call.
+ * ---------------------------------------------------------------------
+ */
+ mov x0, x1
+ ret
+endfunc spm_secure_partition_exit