Re: [PULL 5/5] linux-user: Fix qemu-arm to run static armhf binaries

[Michael Tokarev]

19.07.2023 18:52, Helge Deller wrote:
> qemu-user crashes immediately when running static binaries on the armhf
> architecture. The problem is the memory layout where the executable is
> loaded before the interpreter library, in which case the reserved brk
> region clashes with the interpreter code and is released before qemu
> tries to start the program.
>
> At load time qemu calculates a brk value for interpreter and executable
> each.  The fix is to choose the higher one of both.
>
> Signed-off-by: Helge Deller <deller@gmx.de>
> Cc: Andreas Schwab <schwab@suse.de>
> Cc: qemu-stable@nongnu.org
> Reported-by:  Venkata.Pyla@toshiba-tsip.com
> Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1040981
> ---
>   linux-user/elfload.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index a26200d9f3..94951630b1 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -3615,6 +3615,13 @@ int load_elf_binary(struct linux_binprm *bprm, struct 
> image_info *info)
>
>       if (elf_interpreter) {
>           load_elf_interp(elf_interpreter, &interp_info, bprm->buf);
> +        /*
> +         * adjust brk address if the interpreter was loaded above the main
> +         * executable, e.g. happens with static binaries on armhf
> +         */
> +        if (interp_info.brk > info->brk) {
> +            info->brk = interp_info.brk;
> +        }

So, this is kinda amusing.
This broke arm64, ppc64el and s390x:

arm64$ ./qemu-aarch64 /bin/sh -c '/bin/ls -dCFl *[t]* >/dev/null'
qemu: uncaught target signal 11 (Segmentation fault) - core dumped
Segmentation fault

(it was just a quick test from debian qemu-user package).

Reverting this patch makes it work again..

*Sigh*.

(This is currently broken in debian unstable too, - this is how I
noticed the breakage).

Thanks,

/mjt