[rtems commit] i386: Fix possible race condition on first context restore
Sebastian Huber
sebh at rtems.org
Wed Jul 29 09:39:13 UTC 2020
Module: rtems
Branch: master
Commit: 21c7e3a41f1590b18c2c3f883e2b63e36cc409aa
Changeset: http://git.rtems.org/rtems/commit/?id=21c7e3a41f1590b18c2c3f883e2b63e36cc409aa
Author: Jan Sommer <jan.sommer at dlr.de>
Date: Wed Jul 22 14:41:51 2020 +0200
i386: Fix possible race condition on first context restore
Make sure that the esp is restored before the eflags register.
When the init task is initially restored, system interrupts are activated when the
eflags register is loaded.
If the esp register still points to an address in the interrupt stack
area (from early system initlization) the ISR might overwrite its own
stack.
Closes #4031
---
cpukit/score/cpu/i386/cpu_asm.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/cpukit/score/cpu/i386/cpu_asm.S b/cpukit/score/cpu/i386/cpu_asm.S
index 6031f69..2336095 100644
--- a/cpukit/score/cpu/i386/cpu_asm.S
+++ b/cpukit/score/cpu/i386/cpu_asm.S
@@ -83,9 +83,9 @@ SYM (_CPU_Context_switch):
.L_restore:
movl I386_CONTEXT_CONTROL_ISR_DISPATCH_DISABLE(eax),ecx
movl ecx,PER_CPU_ISR_DISPATCH_DISABLE(edx)
+ movl REG_ESP(eax),esp /* restore stack pointer */
pushl REG_EFLAGS(eax) /* push eflags */
popf /* restore eflags */
- movl REG_ESP(eax),esp /* restore stack pointer */
movl REG_EBP(eax),ebp /* restore base pointer */
movl REG_EBX(eax),ebx /* restore ebx */
movl REG_ESI(eax),esi /* restore source register */
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