----- Original Message -----
> Hi All,
>
> I try to use `bt -a' for arm64 platform, then Segmentation fault
> happened. My crash is built from source code hosted on github. And my
> kernel version is 4.4.35.
I note your reference to github, but what version of crash are you using?
The only thing that comes to mind is this fix that went into crash-7.1.8:
- Fix for the ARM64 "bt" command in Linux 4.10 and later kernels that
are configured with CONFIG_THREAD_INFO_IN_TASK. Without the patch,
the "bt" command will fail for active tasks in dumpfiles that were
generated by the kdump facility.
(takahiro.akashi@xxxxxxxxxx)
But since you are using kernel version 4.4.35, that is presumably not
the problem.
> I tried to use gdb to examine this problem, Some information is shown
> as below:
>
> (gdb) bt
> #0 arm64_is_kernel_exception_frame (bt=bt@entry=0x7ffeba6577e0,
> stkptr=stkptr@entry=18446743803091823872) at arm64.c:1504
> #1 0x00000000004fbda8 in arm64_back_trace_cmd (bt=0x7ffeba6577e0) at arm64.c:2259
> #2 0x00000000004d415c in back_trace (bt=bt@entry=0x7ffeba6577e0) at kernel.c:3063
> #3 0x00000000004dee87 in cmd_bt () at kernel.c:2701
> [...]
> (gdb) p/x stkptr
> $14 = 0xffffffc0fded2d00
> (gdb) p/x bt->stackbase
> $15 = 0xffffff8008dcc000
>
> As it is, (stkptr - bt->stackbase) is too large. It lead
> bt->stackbuf[(ulong)(STACK_OFFSET_TYPE(stkptr))] index out of bounds.
> This stack belongs to swapper/0. I'm not sure whether it is a BUG.
> Could anyone give me some advise to solve this problem? Thank you!
The closest sample arm64 kernel I have available is 4.5-based, and looking
at the kernel virtual address space, both the stkptr and stackbase values
above are out of range, so I'm not sure what's going on:
crash> mach
MACHINE TYPE: aarch64
MEMORY SIZE: 16 GB
CPUS: 1
HZ: 1000
PAGE SIZE: 65536
KERNEL VIRTUAL BASE: ffff800000000000
KERNEL VMALLOC BASE: ffff000000000000
KERNEL MODULES BASE: ffff7ffffc000000
KERNEL VMEMMAP BASE: ffff7fbfe0000000
KERNEL STACK SIZE: 16384
IRQ STACK SIZE: 16384
IRQ STACKS:
CPU 0: ffff8003ffe30020
CPU 1: ffff8003ffe60020
CPU 2: ffff8003ffe90020
CPU 3: ffff8003ffec0020
CPU 4: ffff8003ffef0020
CPU 5: ffff8003fff20020
CPU 6: ffff8003fff50020
CPU 7: ffff8003fff80020
crash>
Dave
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