Re: [Crash-utility] EXT: Re: EXT: Re: crash start in CentOS 8
Hello Kazu,
On Mon, Jun 15, 2020 at 8:38 PM HAGIO KAZUHITO(萩尾 一仁)
<k-hagio-ab(a)nec.com> wrote:
-----Original Message-----
> > [root@lxkmg-pag-ale test64]# /usr/bin/crash -d 15
> > System.map-4.18.0-147.el8.x86_64 vmlinux.debuginfo vmcore
...
> > <read_diskdump: addr: ffffffff82131200 paddr: 37b31200 cnt: 8>
> > read_diskdump: PAGE_EXCLUDED: paddr/pfn: 37b31200/37b31
> > crash: page excluded: kernel virtual address: ffffffff82131200 type:
"page_offset_base"
> > [root@lxkmg-pag-ale test64]#
>
> Hmmm, I think you should find better results with:
>
> $ crash vmlinux vmcore (On the machine used for post-processing)
>
> and
>
> $ crash vmlinux /proc/kcore (On the original crashing system)
>
> I think if that helps you reach the crash > prompt, we have a potential issue
which needs to be looked-at.
> Can you please try to run the same and let me know the outcome?
>
> Thanks,
> Bhupesh
>
>
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>
> Hello,
>
> Running the above mentioned command on the server used to post process the crash
shows a message indicating
> a mismatch between the vmcore and kernel.debug binary.
>
> I will now first try to clarify this and come back later on if the issue is still
there.
>
> Thanks for helping.
> Best regards,
> Patrick Agrain
>
Just FYI, with respect to the System.map file, the following Dave's post
would be helpful:
https://www.redhat.com/archives/crash-utility/2018-June/msg00002.html
If you have the vmlinux corresponding to a running kernel, you don't need
the System.map file.
Indeed, I remember discussing this with Dave A. some months back.
Infact with newer KASLR enabled kernels it makes little sense to use
System.map file as it contains the non-relocated symbol values that
were compiled into the vmlinux file - that's why I suggested just to
use to the vmlinux and vmcore file as an arguments while invoking the
crash tool to Patrick.
However, going back to the discussion I had with Dave A., I think the
main point of confusion was the 'crash_whitepaper' which is still
located at [1], and which provides the following example to invoke the
crash utility with the System.map file, vmlinux and vmcore
combination:
Examples when running on a dumpfile:
$ crash /boot/System.map vmlinux.dbg vmcore
I think while this was ok for older kernels which did not support
KASLR, for newer kernels this needs an update.
I am trying to see if I can modify the 'crash_whitepaper' and push the
same to github, so that users are not confused with the System.map
option.
What's your views on the same? Please let me know.
[1]. https://crash-utility.github.io/crash_whitepaper.html
Thanks,
Bhupesh