diff options
| author | Nicholas Piggin | 2017-07-29 22:50:27 +1000 |
|---|---|---|
| committer | Michael Ellerman | 2017-07-31 20:22:37 +1000 |
| commit | cc491f1d3583146eaee635c86b9c9227fa835c6c (patch) | |
| tree | 5b2d43d7d4bf922f96f9eb5dd7485131360c4231 | |
| parent | bb272221e9db79f13d454e1f3fb6b05013be985e (diff) | |
powerpc/64s: Fix stack setup in watchdog soft_nmi_common()
The watchdog soft-NMI exception stack setup loads a stack pointer
twice, which is an obvious error. It ends up using the system reset
interrupt (true-NMI) stack, which is also a bug because the watchdog
could be preempted by a system reset interrupt that overwrites the
NMI stack.
Change the soft-NMI to use the "emergency stack". The current kernel
stack is not used, because of the longer-term goal to prevent
asynchronous stack access using soft-disable.
Fixes: 2104180a5369 ("powerpc/64s: implement arch-specific hardlockup watchdog")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
| -rw-r--r-- | arch/powerpc/kernel/exceptions-64s.S | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 9029afd1fa2a..f14f3c04ec7e 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -1325,10 +1325,18 @@ EXC_VIRT_NONE(0x5800, 0x100) std r10,PACA_EXGEN+EX_R13(r13); \ EXCEPTION_PROLOG_PSERIES_1(soft_nmi_common, _H) +/* + * Branch to soft_nmi_interrupt using the emergency stack. The emergency + * stack is one that is usable by maskable interrupts so long as MSR_EE + * remains off. It is used for recovery when something has corrupted the + * normal kernel stack, for example. The "soft NMI" must not use the process + * stack because we want irq disabled sections to avoid touching the stack + * at all (other than PMU interrupts), so use the emergency stack for this, + * and run it entirely with interrupts hard disabled. + */ EXC_COMMON_BEGIN(soft_nmi_common) mr r10,r1 ld r1,PACAEMERGSP(r13) - ld r1,PACA_NMI_EMERG_SP(r13) subi r1,r1,INT_FRAME_SIZE EXCEPTION_COMMON_NORET_STACK(PACA_EXGEN, 0x900, system_reset, soft_nmi_interrupt, |