commit 300c68da11fda3669d7b80b68dcd67b0b2082cbc
author Kevin Peng <kevin.peng@arm.com> Thu Aug 12 17:40:17 2021 +0800
committer Kevin Peng <kevin.peng@arm.com> Mon Sep 13 11:23:32 2021 +0800
tree a3e0cc35b8e7966b94631028d50f91c8c2f6a49e
parent e863e5ce570c9a76f633a765b22f1d608e24e75a

SPM: Use Main Stack for initialization

On reset, the Main Stack is used by default.
TF-M changes the stack to Processor Stack.

This patch remove the change to PSP in startup.s and:
- Rename the ARM_LIB_STACK to ER_INITIAL_PSP
- Rename the ARM_LIB_STACK_MSP to ARM_LIB_STACK
The renaming is to align the __main function of ARMClang where the
ARM_LIB_STACK is set to the current SP (MSP)

For Library Mode, the stacks are set to back to use PSP before entering
c code to avoid massive corresponding changes.

For FF-M implementations, this patch also:
- Seal the Main Stack before entering c code
- Manually free the Main Stack usage after initialization as the init
  function does not return

Change-Id: Ie1b6f2fca1f774c4812a89fa45bb039b16fe5af0
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
Co-authored-by: Summer Qin <summer.qin@arm.com>

secure_fw/spm/cmsis_psa/main.c

diff --git a/secure_fw/spm/cmsis_psa/main.c b/secure_fw/spm/cmsis_psa/main.c
index 7d34578..30cae8b 100644
--- a/secure_fw/spm/cmsis_psa/main.c
+++ b/secure_fw/spm/cmsis_psa/main.c
@@ -31,7 +31,7 @@
 #error Invalid TFM_LVL value. Only TFM_LVL 1, 2 and 3 are supported in IPC model!
 #endif
 
-REGION_DECLARE(Image$$, ARM_LIB_STACK_MSP,  $$ZI$$Base);
+REGION_DECLARE(Image$$, ARM_LIB_STACK, $$ZI$$Base);
 
 static fih_int tfm_core_init(void)
 {
@@ -123,13 +123,24 @@
     FIH_RET(fih_int_encode(TFM_SUCCESS));
 }
 
+__attribute__((naked))
 int main(void)
 {
+    __ASM volatile(
+        "ldr    r0, =0xFEF5EDA5     \n" /* Seal Main Stack before using */
+        "ldr    r1, =0xFEF5EDA5     \n"
+        "push   {r0, r1}            \n"
+        "bl     c_main              \n"
+    );
+}
+
+int c_main(void)
+{
     fih_int fih_rc = FIH_FAILURE;
 
     /* set Main Stack Pointer limit */
-    tfm_arch_init_secure_msp((uint32_t)&REGION_NAME(Image$$, ARM_LIB_STACK_MSP,
-                                               $$ZI$$Base));
+    tfm_arch_set_msplim((uint32_t)&REGION_NAME(Image$$, ARM_LIB_STACK,
+                                                                   $$ZI$$Base));
 
     fih_delay_init();
 
@@ -152,4 +163,6 @@
 
     /* Move to handler mode for further SPM initialization. */
     tfm_core_handler_mode();
+
+    return 0;
 }