Re: [PATCH] Simplify /proc/<pid|self>/exe symlink code

[Al Viro <viro@ftp.linux.org.uk>]

On Thu, Jul 12, 2007 at 07:00:12PM -0700, Matt Helsley wrote:
> This patch avoids holding the mmap semaphore while walking VMAs in response to
> programs which read or follow the /proc/<pid|self>/exe symlink. This also allows
> us to merge mmu and nommu proc_exe_link() functions. The costs are holding the
> task lock, a separate reference to the executable file stored in the task
> struct, and increased code in fork, exec, and exit paths.

I don't think it's a food idea.  Consider a program that deliberately
creates an executable anon memory, copies the binary there, jumps there
and unmaps the original.   In the current tree you'll get nothing
pinning the binary; with your patch it will remained busy.

It's not a common situation, of course, but there are legitimate uses
for such technics...
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