diff options
| author | Vineet Gupta <Vineet.Gupta1@synopsys.com> | 2014-04-30 15:26:45 +0530 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-05-13 13:59:46 +0200 |
| commit | 149849f8b5e2b6f3424dde4ad95c521954bafeb9 (patch) | |
| tree | f146beafe1e1cdc94808e03f486600aa879cca69 | |
| parent | ec2d1018b19afeedaba7e0aff6ccd0f0c73c00e4 (diff) | |
ARC: !PREEMPT: Ensure Return to kernel mode is IRQ safe
commit 8aa9e85adac609588eeec356e5a85059b3b819ba upstream.
There was a very small race window where resume to kernel mode from a
Exception Path (or pure kernel mode which is true for most of ARC
exceptions anyways), was not disabling interrupts in restore_regs,
clobbering the exception regs
Anton found the culprit call flow (after many sleepless nights)
| 1. we got a Trap from user land
| 2. started to service it.
| 3. While doing some stuff on user-land memory (I think it is padzero()),
| we got a DataTlbMiss
| 4. On return from it we are taking "resume_kernel_mode" path
| 5. NEED_RESHED is not set, so we go to "return from exception" path in
| restore regs.
| 6. there seems to be IRQ happening
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Anton Kolesov <Anton.Kolesov@synopsys.com>
Cc: Francois Bedard <Francois.Bedard@synopsys.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/arc/kernel/entry.S | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S index 57f38333834..6f3cd0fb4b5 100644 --- a/arch/arc/kernel/entry.S +++ b/arch/arc/kernel/entry.S @@ -651,11 +651,13 @@ resume_user_mode_begin: resume_kernel_mode: -#ifdef CONFIG_PREEMPT - - ; This is a must for preempt_schedule_irq() + ; Disable Interrupts from this point on + ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq() + ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe IRQ_DISABLE r9 +#ifdef CONFIG_PREEMPT + ; Can't preempt if preemption disabled GET_CURR_THR_INFO_FROM_SP r10 ld r8, [r10, THREAD_INFO_PREEMPT_COUNT] |