Re: [Crash-utility] [BUG?] failed to execute bt -a for arm64
On Mon, Apr 17, 2017 at 09:05:12AM -0400, Dave Anderson wrote:
----- 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(a)linaro.org)
But since you are using kernel version 4.4.35, that is presumably not
the problem.
Thank you for rapid response.
I'm using the most current code, which already contains this patch.
Its version is 7.1.8++.
> 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>
I'm afraid I don't get you. Did you mean you cannot reproduce this
phenomenon? Because the index is (stkptr - bt->stackbase). I think it
should be OK if they are in the same range(both larger than
PAGE_OFFSET of both smaller than PAGE_OFFSET). For my further inspect,
Only bt 0 will crash. bt other thread is OK. I guess maybe swapper
also should use stack address beyond PAGE_OFFSET (for my board, it's
0xffffffc000000000).
Dave
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