linux-kernel - Re: Feature request: exec self for NOMMU.

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Date:	Tue, 26 Dec 2006 22:08:36 -0800
From:	Vadim Lobanov <vlobanov@...akeasy.net>
To:	Rob Landley <rob@...dley.net>
Cc:	ray-gmail@...rabbit.org, linux-kernel@...r.kernel.org,
	David McCullough <david_mccullough@...securecomputing.com>
Subject: Re: Feature request: exec self for NOMMU.

On Wed, 2006-12-27 at 00:51 -0500, Rob Landley wrote:
> On Wednesday 27 December 2006 12:13 am, Ray Lee wrote:
> > How about openning an fd to yourself at the beginning of execution, then
> > calling fexecve later?
> 
> I haven't got a man page for fexecve.  Does libc have it?

It's implemented inside glibc, and uses /proc to execve() the file that
the fd points to. Here's the code from
sysdeps/unix/sysv/linux/fexecve.c:

fexecve (fd, argv, envp)
     int fd;
     char *const argv[];
     char *const envp[];
{
  ...
  /* We use the /proc filesystem to get the information.  If it is not
     mounted we fail.  */
  char buf[sizeof "/proc/self/fd/" + sizeof (int) * 3];
  __snprintf (buf, sizeof (buf), "/proc/self/fd/%d", fd);

  /* We do not need the return value.  */
  __execve (buf, argv, envp);
  ...
}


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