Commit a7e30b8d authored by Philippe Rétornaz's avatar Philippe Rétornaz Committed by Haavard Skinnemoen

[AVR32] Fix random segfault with preemption

As explained on:
http://www.avrfreaks.net/index.php?nameÿphpBB2&fileÿewtopic&tS307
If the current process is preempted before it can copy RAR_SUP and
RSR_SUP both register are lost and the process will segfault as soon
as it return from the syscall since the return adress will be
corrupted.

This patch disable IRQ as soon as we enter the syscall path and
reenable them when the copy is done.

In the interrupt handlers, check if we are interrupting the srrf
instruction, if so disable interrupts and return. The interrupt
handler will be re-called immediatly when the interrupts are
reenabled.

After some stressing workload:
 - find / > /dev/null in loop
 - top (in ssh)
 - ping -f avr32

The segfaults are not seen anymore.
Signed-off-by: default avatarPhilippe Rétornaz <philippe.retornaz@epfl.ch>
Signed-off-by: default avatarHaavard Skinnemoen <hskinnemoen@atmel.com>
parent bb7aa6d4
......@@ -159,11 +159,18 @@ handle_vmalloc_miss:
.section .scall.text,"ax",@progbits
system_call:
#ifdef CONFIG_PREEMPT
mask_interrupts
#endif
pushm r12 /* r12_orig */
stmts --sp, r0-lr
zero_fp
mfsr r0, SYSREG_RAR_SUP
mfsr r1, SYSREG_RSR_SUP
#ifdef CONFIG_PREEMPT
unmask_interrupts
#endif
zero_fp
stm --sp, r0-r1
/* check for syscall tracing */
......@@ -638,6 +645,13 @@ irq_level\level:
stmts --sp,r0-lr
mfsr r8, rar_int\level
mfsr r9, rsr_int\level
#ifdef CONFIG_PREEMPT
sub r11, pc, (. - system_call)
cp.w r11, r8
breq 4f
#endif
pushm r8-r9
mov r11, sp
......@@ -668,6 +682,16 @@ irq_level\level:
sub sp, -4 /* ignore r12_orig */
rete
#ifdef CONFIG_PREEMPT
4: mask_interrupts
mfsr r8, rsr_int\level
sbr r8, 16
mtsr rsr_int\level, r8
ldmts sp++, r0-lr
sub sp, -4 /* ignore r12_orig */
rete
#endif
2: get_thread_info r0
ld.w r1, r0[TI_flags]
bld r1, TIF_CPU_GOING_TO_SLEEP
......
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