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From: Valdis.Kletnieks@vt.edu
To: kernel-hardening@lists.openwall.com
Cc: Emese Revfy <re.emese@gmail.com>,
	Matt Davis <mattdavis9@gmail.com>,
	pageexec@freemail.hu, spender@grsecurity.net, mmarek@suse.com,
	keescook@chromium.org, linux-kernel@vger.kernel.org,
	yamada.masahiro@socionext.com, linux-kbuild@vger.kernel.org,
	minipli@ld-linux.so, linux@armlinux.org.uk,
	catalin.marinas@arm.com, linux@rasmusvillemoes.dk,
	david.brown@linaro.org, benh@kernel.crashing.org,
	tglx@linutronix.de, akpm@linux-foundation.org,
	jlayton@poochiereds.net, arnd@arndb.de
Subject: Re: [kernel-hardening] Re: [PATCH v1 0/2] Introduce the initify gcc plugin
Date: Tue, 28 Jun 2016 18:07:01 -0400	[thread overview]
Message-ID: <47053.1467151621@turing-police.cc.vt.edu> (raw)
In-Reply-To: <1467150555.24287.77.camel@perches.com>

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On Tue, 28 Jun 2016 14:49:15 -0700, Joe Perches said:

> Another potentially useful plugin, especially for embedded systems,
> would be to compress any string literal marked with
>
> 	 __attribute__((format(printf, string-index,)))
>
> and decompress the compressed format on the stack in lib/vsprintf.c
> vsnprintf just before use.

Are there enough such strings in the kernel to make it worth the effort?
I'm assuming that the string literals in printk("some string here") are
automatically so marked?

Is there a minimum length under which the compression overhead actually
makes it larger?  For instance, "a" can't be compressed, because you need
to indicate there's 1 "a" and 1 \0, while "aaaaaa" can, because you can
express it as '6*"a" 1 \0 in only 4 bytes not 7.  But exactly where the
cutoff is, I have no idea (and is probably *very* text-dependent, as
"aaaaaa" and "abcdef" will compress differently....)


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  reply	other threads:[~2016-06-28 22:09 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-28 11:34 [PATCH v1 0/2] Introduce the initify gcc plugin Emese Revfy
2016-06-28 11:34 ` [kernel-hardening] " Emese Revfy
2016-06-28 11:35 ` [PATCH v1 1/2] Add " Emese Revfy
2016-06-28 11:35   ` [kernel-hardening] " Emese Revfy
2016-06-28 21:05   ` Rasmus Villemoes
2016-06-28 21:05     ` [kernel-hardening] " Rasmus Villemoes
2016-06-29 14:50     ` Kees Cook
2016-06-29 14:50       ` [kernel-hardening] " Kees Cook
2016-06-29 14:50       ` Kees Cook
2016-06-29 19:03     ` Emese Revfy
2016-06-29 19:03       ` [kernel-hardening] " Emese Revfy
2016-06-28 11:36 ` [PATCH v1 2/2] Mark functions with the __nocapture attribute Emese Revfy
2016-06-28 11:36   ` [kernel-hardening] " Emese Revfy
2016-06-28 16:43   ` Joe Perches
2016-06-28 16:43     ` [kernel-hardening] " Joe Perches
2016-06-28 20:40     ` Emese Revfy
2016-06-28 20:40       ` [kernel-hardening] " Emese Revfy
2016-06-28 21:00       ` Joe Perches
2016-06-28 21:00         ` [kernel-hardening] " Joe Perches
2016-06-29 18:42         ` Emese Revfy
2016-06-29 18:42           ` [kernel-hardening] " Emese Revfy
2016-06-30  0:12           ` Joe Perches
2016-06-30  0:12             ` [kernel-hardening] " Joe Perches
2016-07-01 14:03             ` Emese Revfy
2016-07-01 14:03               ` [kernel-hardening] " Emese Revfy
2016-06-28 20:50   ` Rasmus Villemoes
2016-06-28 20:50     ` [kernel-hardening] " Rasmus Villemoes
2016-06-28 21:38     ` PaX Team
2016-06-28 21:38       ` [kernel-hardening] " PaX Team
2016-06-28 22:41       ` Rasmus Villemoes
2016-06-28 22:41         ` [kernel-hardening] " Rasmus Villemoes
2016-06-29 18:39     ` Emese Revfy
2016-06-29 18:39       ` [kernel-hardening] " Emese Revfy
2016-06-28 11:42 ` [PATCH v1 0/2] Introduce the initify gcc plugin Emese Revfy
2016-06-28 11:42   ` [kernel-hardening] " Emese Revfy
2016-06-28 12:57 ` [kernel-hardening] " Mark Rutland
2016-06-28 16:14   ` Emese Revfy
2016-06-28 20:46     ` Kees Cook
2016-06-28 20:46       ` Kees Cook
2016-06-29  8:21       ` Mark Rutland
2016-06-29  8:21         ` Mark Rutland
2016-06-29 17:52         ` Mark Rutland
2016-06-29 17:52           ` Mark Rutland
2016-06-29 18:28           ` Emese Revfy
2016-06-29 18:28             ` Emese Revfy
2016-06-28 16:35 ` Joe Perches
2016-06-28 16:35   ` [kernel-hardening] " Joe Perches
2016-06-28 18:48   ` Joe Perches
2016-06-28 18:48     ` [kernel-hardening] " Joe Perches
2016-06-28 19:02     ` Rasmus Villemoes
2016-06-28 19:02       ` [kernel-hardening] " Rasmus Villemoes
2016-06-28 20:29       ` Emese Revfy
2016-06-28 20:29         ` [kernel-hardening] " Emese Revfy
2016-06-28 17:00 ` Mathias Krause
2016-06-28 17:00   ` [kernel-hardening] " Mathias Krause
2016-06-28 20:29   ` Emese Revfy
2016-06-28 20:29     ` [kernel-hardening] " Emese Revfy
2016-06-28 21:49 ` Joe Perches
2016-06-28 21:49   ` [kernel-hardening] " Joe Perches
2016-06-28 22:07   ` Valdis.Kletnieks [this message]
2016-06-28 23:54     ` Joe Perches

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