linux-kernel - Re: [PATCH] make execve(NULL) re-execute current binary

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Message-ID: <1158166a0906300510w5b03adb9k7368a049a2bec263@mail.gmail.com>
Date:	Tue, 30 Jun 2009 14:10:15 +0200
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Frysinger <vapier@...too.org>
Subject: Re: [PATCH] make execve(NULL) re-execute current binary

On Tue, Jun 30, 2009 at 12:27 AM, Alan Cox<alan@...rguk.ukuu.org.uk> wrote:
> On Tue, 30 Jun 2009 00:03:39 +0200
> Denys Vlasenko <vda.linux@...glemail.com> wrote:
>
>> Hi Al, Andrew, folks,
>>
>> This is a version 2 of re-execution patch.
>>
>> I replaced hardcoded "/proc/self/exe" with execve(NULL)
>
> So you add hacks to sys_execve, which means hacks on every system that
> doesn't need it

Yes.

> and also undefined behaviour if you use the feature when
> it isn't present.

The behavior of execve(NULL) is not undefined. It returns EFAULT.
The idea was that application will do:

/* Try traditional way */
execv("/proc/self/exe", argv);

/* Try Linux specific extension (only new kernels have it) */
execv(NULL, argv);

/* Give up */
printf("Can't re-exec myself\n");
exit(1);

which is safe on older kernels as well.

> Please implement sys_reexec() as was suggested before.

Ok.

--
vda
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