linux-kernel - Re: [PATCH 0/2] wait/ptrace: always assume _

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Message-ID: <20151025154256.GA2043@redhat.com>
Date:	Sun, 25 Oct 2015 16:42:56 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Pedro Alves <palves@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Jan Kratochvil <jan.kratochvil@...hat.com>,
	Julien Tinnes <jln@...gle.com>,
	Kees Cook <keescook@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
	Robert Swiecki <swiecki@...gle.com>,
	Roland McGrath <roland@...k.frob.com>,
	syzkaller@...glegroups.com, linux-kernel@...r.kernel.org,
	"gdb@...rceware.org" <gdb@...rceware.org>
Subject: Re: [PATCH 0/2] wait/ptrace: always assume __WALL if the child is
	traced

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.

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