[Crash-utility] [PATCH] x86_64: do not process zero size exception stack
There is an issue with newer Linux kernel (found on 5.9.y)
where 'bt 0' fails with:
crash> bt 0
PID: 0 TASK: ffffffff95414900 CPU: 0 COMMAND: "swapper/0"
bt: invalid size request: 0 type: "stack contents"
bt: read of stack at fffffe0000012000 failed
The reason is: readmem fails to read content of exception
stack [4]. As you can see it has correct base: fffffe0000012000,
but zero size, See reduced output of 'help -m':
stkinfo: isize: 16384
esize[7]: 4096,4096,4096,4096,0,0,0
NMI_stack_index: 1
exception_stacks:
[0]: DOUBLEFAULT
[1]: NMI
[2]: DEBUG
[3]: MCE
[4]: (unknown)
[5]: (unknown)
[6]: (unknown)
ebase[cpus][7]:
[0]: fffffe0000009000 fffffe000000b000 fffffe000000d000 fffffe000000f000
fffffe0000012000 0000000000000000 0000000000000000
there are only 4 exception stacks for x86. So I'm not sure what
5th ebase ([4]) is, but its size is zero, (guard page?)
So, solution I use here is to ignore exception stack if its size
is zero.
Signed-off-by: Alexey Makhalov <amakhalov(a)vmware.com>
---
x86_64.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/x86_64.c b/x86_64.c
index fc05e8a..a8c9b2e 100644
--- a/x86_64.c
+++ b/x86_64.c
@@ -5090,7 +5090,7 @@ skip_stage:
ms->stkinfo.esize[estack];
console("x86_64_get_dumpfile_stack_frame: searching %s estack at %lx\n",
ms->stkinfo.exception_stacks[estack], bt->stackbase);
- if (!(bt->stackbase))
+ if (!(bt->stackbase) || !(ms->stkinfo.esize[estack]))
goto skip_stage;
bt->stackbuf = ms->irqstack;
alter_stackbuf(bt);
--
2.11.0