linux-kernel - Re: [PATCH] get_random_long() and AT

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Message-ID: <20070625070938.GN7012@devserv.devel.redhat.com>
Date:	Mon, 25 Jun 2007 03:09:38 -0400
From:	Jakub Jelinek <jakub@...hat.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Matt Mackall <mpm@...enic.com>,
	Alexander Gabert <pappy@...too.org>,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	libc-alpha@...rceware.org, hardened@...too.org
Subject: Re: [PATCH] get_random_long() and AT_ENTROPY for auxv, kernel 2.6.21.5

On Sun, Jun 24, 2007 at 09:43:03PM -0700, Arjan van de Ven wrote:
> > - something to do with aux vector headers
> 
> the primary goal is to pass a random value to userspace at process
> start; this to save glibc from having to open /dev/urandom on ever
> program start (which it does now for all apps compiled with
> -fstack-protector, which in various distros is "everything").

There are 2 ways to compile -fstack-protector supporting glibc actually,
only one opens /dev/urandom on every program initialization, the other
computes the stack guard from some bits of the stack address (so indirectly
depends on get_random_int() in stack randomization).
Nevertheless, having one random long (32-bit for 32-bit arches, 64-bit
otherwise) in aux vector would be useful.

	Jakub
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