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Date: Sun, 25 Oct 2015 14:46:00 -0000
From: Oleg Nesterov <oleg@redhat.com>
To: Pedro Alves <palves@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,        Dmitry Vyukov <dvyukov@google.com>,        Alexander Potapenko <glider@google.com>,        Denys Vlasenko <dvlasenk@redhat.com>,        Eric Dumazet <edumazet@google.com>,        Jan Kratochvil <jan.kratochvil@redhat.com>,        Julien Tinnes <jln@google.com>, Kees Cook <keescook@google.com>,        Kostya Serebryany <kcc@google.com>,        Linus Torvalds <torvalds@linux-foundation.org>,        "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,        Robert Swiecki <swiecki@google.com>,        Roland McGrath <roland@hack.frob.com>, syzkaller@googlegroups.com,        linux-kernel@vger.kernel.org,        "gdb@sourceware.org" <gdb@sourceware.org>
Subject: Re: [PATCH 0/2] wait/ptrace: always assume __WALL if the child is	traced
Message-ID: <20151025154256.GA2043@redhat.com>
References: <20151020171740.GA29290@redhat.com> <5628F569.4070602@redhat.com>
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On 10/22, Pedro Alves wrote:
>
> In any case, to make sure existing gdb binaries would still work
> with your kernel change, I ran GDB's testsuite with this:
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> diff --git a/gdb/nat/linux-waitpid.c b/gdb/nat/linux-waitpid.c
> index cbcdd95..864ba2e 100644
> --- a/gdb/nat/linux-waitpid.c
> +++ b/gdb/nat/linux-waitpid.c
> @@ -149,3 +149,17 @@ my_waitpid (int pid, int *status, int flags)
>    errno = out_errno;
>    return ret;
>  }
> +
> +#include <dlfcn.h>
> +
> +pid_t
> +waitpid (pid_t pid, int *status, int options)
> +{
> +  static pid_t (*waitpid2) (pid_t pid, int *status, int options) = NULL;
> +
> +  if (waitpid2 == NULL)
> +    waitpid2 = dlsym (RTLD_NEXT, "waitpid");
> +
> +  options |= __WALL;
> +  return waitpid2 (pid, status, options);
> +}
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thanks a lot Pedro!

So gdb should be fine, strace too. Perhaps we should change the kernel
this way and forget about /sbin/init fixes.

Oleg.