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imx233: fix IRQ handler w.r.t unwinder

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The IRQ handler saves registers on the IRQ stack, saves the old PC to imx233
HW_DIGCTL_SCRATCH0 register and switcht to SVC for the actual handling. The
old code had a problem in that if the unwinder is called during the IRQ (for
example by the watchdog), then __get_sp() will use SPSR_svc to discover the
previous mode, switch to it and recover SP. But SPSR_svc is invalid, it should
be SPSR_irq but we switch from IRQ to SVC mode. The new code copies SPSR_irq
to SPSR_svc in IRQ to fix this problem. It also saves/restore SCRATCH0 in
case I one day renable nested interrupts or use SCRATCH0 for other purposes.
I also changed the old watchdog code to call UIE directly instead of trying
to make the code crash with a SWI.

Change-Id: Id87462d410764b019bd2aa9adc71cb917ade32e3
This commit is contained in:
Amaury Pouly 2016-09-21 00:09:23 +01:00
parent 7e0820fe21
commit a523c3fcfe
2 changed files with 18 additions and 10 deletions
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17
firmware/target/arm/imx233/icoll-imx233.c
View file

@ -205,13 +205,17 @@ void irq_handler(void)
{
/* save stuff */
asm volatile(
/* This part is in IRQ mode (with IRQ stack) */
"sub lr, lr, #4 \n" /* Create return address */
"stmfd sp!, { r0-r5, r12, lr } \n" /* Save what gets clobbered */
"ldr r1, =0x8001c290 \n" /* Save pointer to instruction */
"str lr, [r1] \n" /* in HW_DIGCTL_SCRATCH0 */
"mrs lr, spsr \n" /* Save SPSR_irq */
"stmfd sp!, { r1, lr } \n" /* Push it on the stack */
"ldr r1, =0x8001c290 \n" /* Save HW_DIGCTL_SCRATCH0 */
"ldr r0, [r1] \n" /* and store instruction pointer */
"str lr, [r1] \n" /* in it (for debug) */
"mrs r2, spsr \n" /* Save SPSR_irq */
"stmfd sp!, { r0, r2 } \n" /* Push it on the stack */
"msr cpsr_c, #0x93 \n" /* Switch to SVC mode, IRQ disabled */
/* This part is in SVC mode (with SVC stack) */
"msr spsr_cxsf, r2 \n" /* Copy SPSR_irq to SPSR_svc (for __get_sp) */
"mov r4, lr \n" /* Save lr_SVC */
"and r5, sp, #4 \n" /* Align SVC stack */
"sub sp, sp, r5 \n" /* on 8-byte boundary */
@ -219,7 +223,10 @@ void irq_handler(void)
"add sp, sp, r5 \n" /* Undo alignement */
"mov lr, r4 \n" /* Restore lr_SVC */
"msr cpsr_c, #0x92 \n" /* Mask IRQ, return to IRQ mode */
"ldmfd sp!, { r1, lr } \n" /* Reload saved value */
/* This part is in IRQ mode (with IRQ stack) */
"ldmfd sp!, { r0, lr } \n" /* Reload saved value */
"ldr r1, =0x8001c290 \n" /* Restore HW_DIGCTL_SCRATCH0 */
"str r0, [r1] \n" /* using saved value */
"msr spsr_cxsf, lr \n" /* Restore SPSR_irq */
"ldmfd sp!, { r0-r5, r12, pc }^ \n" /* Restore regs, and RFE */);
}

11
firmware/target/arm/imx233/system-imx233.c
View file

@ -52,15 +52,16 @@
#define WATCHDOG_HW_DELAY (10 * HZ)
#define WATCHDOG_SW_DELAY (5 * HZ)
void UIE(unsigned int pc, unsigned int num);
static void woof_woof(void)
{
/* stop hadrware watchdog, we catched the error */
/* stop hardware watchdog, we catched the error */
imx233_rtc_enable_watchdog(false);
/* recover current PC and trigger abort, so in the hope to get a useful
* backtrace */
uint32_t pc = HW_DIGCTL_SCRATCH0;
/* write a "SWI #0xdead" instruction at the faulty instruction so that it
* will trigger a proper backtrace */
*(uint32_t *)pc = 0xef00dead;
commit_discard_idcache();
UIE(pc, 4);
}
static void good_dog(void)