Re: [Qemu-devel] [PATCH] Python-lang gdb script to extract x86_64 guest vmcore from qemu coredump

[Stefan Hajnoczi]

On Thu, Sep 12, 2013 at 9:46 PM, Laszlo Ersek <address@hidden> wrote:
> When qemu dies unexpectedly, for example in response to an explicit
> abort() call, or (more importantly) when an external signal is delivered
> to it that results in a coredump, sometimes it is useful to extract the
> guest vmcore from the qemu process' memory image. The guest vmcore might
> help understand an emulation problem in qemu, or help debug the guest.
>
> This script reimplements (and cuts many features of) the
> qmp_dump_guest_memory() command in gdb/Python,
>
>   https://sourceware.org/gdb/current/onlinedocs/gdb/Python-API.html
>
> working off the saved memory image of the qemu process. The docstring in
> the patch (serving as gdb help text) describes the limitations relative to
> the QMP command.
>
> Dependencies of qmp_dump_guest_memory() have been reimplemented as needed.
> I sought to follow the general structure, sticking to original function
> names where possible. However, keeping it simple prevailed in some places.
>
> The patch has been tested with a 4 VCPU, 768 MB, RHEL-6.4
> (2.6.32-358.el6.x86_64) guest:

I tried this out with qemu-kvm-1.1.2 and it worked after a few minor
tweaks due to memory data structure changes.  I did hit a problem with
crash since the vmlinux was 32-bit and the guest dump was 64-bit.  But
from what I can tell dump-guest-memory works as advertised.

Reviewed-by: Stefan Hajnoczi <address@hidden>