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ArmPlatformPkg/Sec: Fix transition to Trusted Monitor World with ARMGCC

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The enter_monitor_world() function was trashing r0/r1/r2 registers and then
was returning back to 'C'. The compiler might have used these registers in the C code.
These new design prevents register corruptions.



git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13060 6f19259b-4bc3-4df7-8a09-765794883524
This commit is contained in:
oliviermartin
2012-02-28 17:28:44 +00:00
parent 8cc852f791
commit a853088911
4 changed files with 98 additions and 54 deletions
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24
ArmPlatformPkg/Sec/Helper.asm
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@@ -18,20 +18,26 @@
AREA Helper, CODE, READONLY
// arg0: Secure Monitor mode stack
// r0: Monitor World EntryPoint
// r1: MpId
// r2: Secure Monitor mode stack
enter_monitor_mode
mov r2, lr // Save current lr
mrs r1, cpsr // Save current mode (SVC) in r1
bic r3, r1, #0x1f // Clear all mode bits
mrs r4, cpsr // Save current mode (SVC) in r1
bic r3, r4, #0x1f // Clear all mode bits
orr r3, r3, #0x16 // Set bits for Monitor mode
msr cpsr_cxsf, r3 // We are now in Monitor Mode
mov sp, r0 // Use the passed sp
mov lr, r2 // Use the same lr as before
cmp r2, #0 // If a Secure Monitor stack base has been passed, used it
movne sp, r2 // Use the passed sp
mov lr, r0 // Use the pass entrypoint as lr
msr spsr_cxsf, r1 // Use saved mode for the MOVS jump to the kernel
bx lr
msr spsr_cxsf, r4 // Use saved mode for the MOVS jump to the kernel
mov r4, r0 // Swap EntryPoint and MpId registers
mov r0, r1
bx r4
// We cannot use the instruction 'movs pc, lr' because the caller can be written either in ARM or Thumb2 assembler.
// When we will jump into this function, we will set the CPSR flag to ARM assembler. By copying directly 'lr' into