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cpu/cortexm_common: fix r12 clobber in pendsv for Cortex-M0

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This commit is contained in:
Koen Zandberg 2020-12-15 13:16:02 +01:00
parent 4661948bd1
commit 8f1a42cbbf
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GPG Key ID: 0895A893E6D2985B
1 changed files with 10 additions and 10 deletions
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20
cpu/cortexm_common/thread_arch.c
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@ -372,31 +372,30 @@ void __attribute__((naked)) __attribute__((used)) isr_pendsv(void) {
__asm__ volatile (
/* PendSV handler entry point */
/* save context by pushing unsaved registers to the stack */
/* {r0-r3,r12,LR,PC,xPSR,s0-s15,FPSCR} are saved automatically on exception entry */
/* {r0-r3,r12,LR,PC,PSR} are saved automatically on exception entry */
".thumb_func \n"
".syntax unified \n"
/* skip context saving if sched_active_thread == NULL */
"ldr r1, =sched_active_thread \n" /* r1 = &sched_active_thread */
"ldr r1, [r1] \n"
"mov r12, r1 \n" /* r12 = sched_active_thread */
"push {lr} \n" /* push exception return code */
"push {r4,lr} \n" /* push r4 and exception return code */
"ldr r4, [r1] \n" /* r4 = sched_active_thread */
"cpsid i \n" /* Disable IRQs during sched_run */
"bl sched_run \n" /* perform scheduling */
"cpsie i \n" /* Re-enable interrupts */
/* Cortex-M0, Cortex-M0+ and Cortex-M23 */
"cmp r0, r12 \n" /* if r0 == previous_thread: */
"cmp r0, r4 \n" /* if r0 == previous_thread: */
"bne cont_schedule \n" /* jump over pop if r0 != 0 */
"pop {pc} \n" /* Pop exception return to PC */
"pop {r4,pc} \n" /* Pop exception return to PC */
"cont_schedule: \n" /* Otherwise continue the ctx switch */
"pop {r2} \n" /* Pop LR from the exception stack */
"pop {r1,r2} \n" /* Pop LR from the exception stack */
/* r1 contains r4 from the thread */
"mov lr, r2 \n" /* Store LR in lr */
"mov r1,r12 \n" /* r1 = sched_active_thread */
"cmp r1, #0 \n" /* Test if r1 == NULL */
"cmp r4, #0 \n" /* Test if sched_active_thread == NULL */
"mov r12, sp \n" /* remember the exception SP in r12 */
"beq restore_context \n" /* goto restore_context if r1 == NULL */
@ -406,7 +405,8 @@ void __attribute__((naked)) __attribute__((used)) isr_pendsv(void) {
/* Calculate the expected stack offset beforehand so that we don't have to
* store the old SP from here on, saves a register we don't have */
"subs r0, #36 \n" /* Move saved SP with 9 words */
"str r0, [r1] \n" /* And store */
"str r0, [r4] \n" /* And store */
"mov r4, r1 \n" /* restore r4 content */
/* we can not push high registers directly, so we move R11-R8 into
* R4-R0, as these are already saved */