From mboxrd@z Thu Jan  1 00:00:00 1970
From: Roland McGrath <roland@redhat.com>
Subject: Re: [Patch 3/3] elf: use a macro instead of a raw number
Date: Thu,  2 Jul 2009 02:55:54 -0700 (PDT)
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Cc: linux-kernel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
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To: Amerigo Wang <amwang@redhat.com>
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> But in the kernel code, pr_fname is copied from ->comm, they should
> be equal, shouldn't they?

The point is that we are not at liberty to change the size of pr_fname.
Its size and layout are known to userland and thus set in stone.  To
have a larger size, we would have to invent a new NT_* type code with a
new layout that would also be known to userland.  It's not worth the
bother.  

Nowadays a debugger can see AT_EXECFN in auxv (NT_AUXV in core files,
/proc/pid/auxv live), and look at that address in the user memory (core
file or process).  That's clobberable on the user-mode stack, but it can
be of unbounded size.


Thanks,
Roland