linux-kernel - Re: [PATCH] arm: choose debug/uncompress.h include when uncompress debug is disabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130717151148.GM24642@n2100.arm.linux.org.uk>
Date:	Wed, 17 Jul 2013 16:11:48 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	Julien Grall <julien.grall@...aro.org>,
	Ian Campbell <Ian.Campbell@...rix.com>, patches@...aro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>
Subject: Re: [PATCH] arm: choose debug/uncompress.h include when uncompress
	debug is disabled

On Wed, Jul 17, 2013 at 02:25:38PM +0100, Stefano Stabellini wrote:
> On Mon, 15 Jul 2013, Julien Grall wrote:
> > Even if uncompress debug is disabled, some board will continue to print
> > information during uncompress step.
> 
> Are you talking about DEBUG_UNCOMPRESS?
> Should I read the sentence as "even if DEBUG_UNCOMPRESS is not selected,
> some board will continue to print information during the uncompress step"?
> 
> Isn't this a bug in the platform specific code that should be fixed anyway?

Hang on, let's be clear what's going on here.

1. The normal output from the decompressor is *not* debugging.  By that
   I mean the "Uncompressing kernel... done" message.  That is part of
   user output.

2. In non-multiplatform environments, the decompressor will normally use
   the putc/flush functions found in arch/arm/mach-*/include/mach/uncompress.h
   to implement its output, irrespective of the DEBUG_UNCOMPRESS setting.
   (An interesting point is that DEBUG_UNCOMPRESS really should depend on
   MULTIPLATFORM so that this point is explicit - the option requires
   MULTIPLATFORM to be set.)

3. DEBUG_UNCOMPRESS allows the functions which we've implemented for LL
   debug to be re-used for decompressor output.

4. When DEBUG_UNCOMPRESS is not set in a multiplatform kernel, the
   decompressors putc() and flush() functions are stubbed out.

So, it's quite right that you get output from the decompressor even when
DEBUG_UNCOMPRESS is not set.  There's no problem with that.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/