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

[Dominique MARTINET]

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,
-- 
Dominique