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Date: Mon, 2 Feb 2009 08:59:14 +0100
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Subject: Re: [Qemu-devel] [6485] linux-user: identify running binary in
	/proc/self/exe
From: Laurent Desnogues <laurent.desnogues@gmail.com>
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To: qemu-devel@nongnu.org

On Fri, Jan 30, 2009 at 9:09 PM, Aurelien Jarno <aurelien@aurel32.net> wrote:
> Revision: 6485
>          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6485
> Author:   aurel32
> Date:     2009-01-30 20:09:01 +0000 (Fri, 30 Jan 2009)
>
> Log Message:
> -----------
> linux-user: identify running binary in /proc/self/exe
>
> Some applications like to test /proc/self/exe to find
> out who they are. Fake the result of readlink() for
> them. Use realpath() to return full path to binary
> (which the links /proc/self/exe are)
>
> Signed-off-by: Riku Voipio <riku.voipio@iki.fi>
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
>
> Modified Paths:
> --------------
>    trunk/linux-user/main.c
>    trunk/linux-user/qemu.h
>    trunk/linux-user/syscall.c
>
[...]
> Modified: trunk/linux-user/syscall.c
> ===================================================================
> --- trunk/linux-user/syscall.c  2009-01-30 19:59:17 UTC (rev 6484)
> +++ trunk/linux-user/syscall.c  2009-01-30 20:09:01 UTC (rev 6485)
> @@ -4410,13 +4410,22 @@
>  #endif
>     case TARGET_NR_readlink:
>         {
> -            void *p2;
> +            void *p2, *temp;
>             p = lock_user_string(arg1);
>             p2 = lock_user(VERIFY_WRITE, arg2, arg3, 0);
>             if (!p || !p2)
>                 ret = -TARGET_EFAULT;
> -            else
> -                ret = get_errno(readlink(path(p), p2, arg3));
> +            else {
> +                if (strncmp((const char *)p, "/proc/self/exe", 14) == 0) {
> +                    char real[PATH_MAX];
> +                    temp = realpath(exec_path,real);
> +                    ret = (temp==NULL) ? get_errno(-1) : strlen(real) ;
> +                    snprintf((char *)p2, arg3, "%s", real);
> +                    }
> +                else
> +                    ret = get_errno(readlink(path(p), p2, arg3));
> +                break;

Do we really want to skip unlock_user?

> +            }
>             unlock_user(p2, arg2, ret);
>             unlock_user(p, arg1, 0);
>         }


Laurent