3.13.11.3 -stable review patch. If anyone has any objections, please let me
know.
------------------
From: Vineet Gupta <vineet.gup...@synopsys.com>
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 <vgu...@synopsys.com>
Cc: Anton Kolesov <anton.kole...@synopsys.com>
Cc: Francois Bedard <francois.bed...@synopsys.com>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Kamal Mostafa <ka...@canonical.com>
---
arch/arc/kernel/entry.S | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index 47d09d0..6e8f83a 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -614,11 +614,13 @@ 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]
--
1.9.1
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