[PATCH v1 1/1] i386: Fix possible race condition on first context restore

[Jan Sommer]

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 #4030
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 6031f6914e..23360959f5 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 */
-- 
2.17.1