diff options
| author | Jose Abreu <Jose.Abreu@synopsys.com> | 2017-09-01 19:00:23 +0300 |
|---|---|---|
| committer | Vineet Gupta <vgupta@synopsys.com> | 2017-09-01 21:29:05 +0300 |
| commit | 1ee55a8f7f6b7ca4c0c59e0b4b4e3584a085c2d3 (patch) | |
| tree | b04b36aa2678527e951a7e3d7262926149ac2228 /arch/arc/kernel/entry.S | |
| parent | aa7e3a5e8b63628c7fc131effc163ade08ced41b (diff) | |
| download | linux-1ee55a8f7f6b7ca4c0c59e0b4b4e3584a085c2d3.tar.xz | |
ARC: Re-enable MMU upon Machine Check exception
I recently came upon a scenario where I would get a double fault
machine check exception tiriggered by a kernel module.
However the ensuing crash stacktrace (ksym lookup) was not working
correctly.
Turns out that machine check auto-disables MMU while modules are allocated
in kernel vaddr spapce.
This patch re-enables the MMU before start printing the stacktrace
making stacktracing of modules work upon a fatal exception.
Cc: stable@kernel.org
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Reviewed-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
[vgupta: moved code into low level handler to avoid in 2 places]
Diffstat (limited to 'arch/arc/kernel/entry.S')
| -rw-r--r-- | arch/arc/kernel/entry.S | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S index 1eea99beecc3..85d9ea4a0acc 100644 --- a/arch/arc/kernel/entry.S +++ b/arch/arc/kernel/entry.S @@ -92,6 +92,12 @@ ENTRY(EV_MachineCheck) lr r0, [efa] mov r1, sp + ; hardware auto-disables MMU, re-enable it to allow kernel vaddr + ; access for say stack unwinding of modules for crash dumps + lr r3, [ARC_REG_PID] + or r3, r3, MMU_ENABLE + sr r3, [ARC_REG_PID] + lsr r3, r2, 8 bmsk r3, r3, 7 brne r3, ECR_C_MCHK_DUP_TLB, 1f |