linux-kernel - Re: [uml-devel] [PATCH 2/6] UML: Don't valgrind userspace

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Date:	Fri, 5 Sep 2008 12:37:18 -0400
From:	Jeff Dike <jdike@...toit.com>
To:	Steve VanDeBogart <vandebo-lkml@...dBox.Net>
Cc:	linux-kernel@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net, jiayingz@...gle.com,
	dkegel@...gle.com
Subject: Re: [uml-devel] [PATCH 2/6] UML: Don't valgrind userspace

On Fri, Aug 29, 2008 at 04:15:24PM -0700, Steve VanDeBogart wrote:
> Add a flag to tell Valgrind to run the forked child natively.  Necessary
> because Valgrind makes additional system calls to instrumented processes,
> which confuse UML.

> +#ifdef UML_CONFIG_VALGRIND_SUPPORT
> +		flags |= VALGRIND_CLONE_LETGO;
> +#endif
> +	}

I keep forgetting that I have a really bad feeling about this:

+#define VALGRIND_CLONE_LETGO   0x80000000      /* do not track fork like childr
en*/

This is effectively appropriating part of the kernel's ABI for
valgrind's use.  Not to mention that that bit is already taken:

#define CLONE_IO		0x80000000	/* Clone io context */

Could you do this with an annotation that says "let the next clone run
untraced"?

				Jeff

-- 
Work email - jdike at linux dot intel dot com
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