Re: [PATCH 3/6] linux-user: Adjust brk for load_bias [regression]

[Ilya Leoshkevich <iii@linux.ibm.com>]

On Tue, 2024-11-26 at 16:11 +0900, Dominique MARTINET wrote:
> This commit is fairly old, but this appears to cause a segfault for
> older versions of ldconfig:
> ```
> $ docker run --rm --platform linux/arm64/v8 -ti
> docker.io/debian:bullseye-slim ldconfig
> qemu: uncaught target signal 11 (Segmentation fault) - core dumped
> Segmentation fault (core dumped)
> ```
> 
> The segfault happens inside ldconfig code (code_gen_buffer in qemu's
> backtrace), so I'm not sure how to debug that further, but it doesn't
> reproduce in bookworm's ldconfig so that is something that was
> "fixed"
> in glibc at some point.
> 
> If someone needs to run older debian releases with a newer qemu that
> might be a problem in the future?
> 
> [we might need to run old containers once every few years to rebuild
> old
> projects in a similar environment they were built on, so would
> eventually need to work around this problem somehow]
> 
> 
> The failure can be reproduced just running `qemu-aarch64
> ./path/to/ldconfig` on an extracted container so it was easy to
> bisect
> and I've got down to this commit; hence replying here directly with
> involved people.
> ------
> commit aec338d63bc28f1f13d5e64c561d7f1dd0e4b07e
> Author: Richard Henderson <richard.henderson@linaro.org>
> Date:   Wed Aug 16 10:32:18 2023 -0700
> 
>     linux-user: Adjust brk for load_bias
>     
>     PIE executables are usually linked at offset 0 and are
>     relocated somewhere during load.  The hiaddr needs to
>     be adjusted to keep the brk next to the executable.
>     
>     Cc: qemu-stable@nongnu.org
>     Fixes: 1f356e8c013 ("linux-user: Adjust initial brk when
> interpreter is close to executable")
>     Tested-by: Helge Deller <deller@gmx.de>
>     Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
>     Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>     Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ------
> 
> I've done my share of debugging linux-user last week[1] so I'll leave
> this
> as is for now, I've downgraded to (a non-static-pie build of) 7.1 for
> our build machine and am not in immediate trouble.
> [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1053101
> 
> If this doesn't get much interest I might try to pick at it further
> in
> a couple of weeks, assuming it's something we can/want to fix on qemu
> side.
> 
> Thanks,

Hi,

I think this is
https://gitlab.com/qemu-project/qemu/-/issues/1913

Best regards,
Ilya