linux-kernel - Re: [PATCH 1/2] vsprintf: introduce %pT format specifier

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Message-ID: <20110323131213.GA25467@elte.hu>
Date:	Wed, 23 Mar 2011 14:12:13 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 1/2] vsprintf: introduce %pT format specifier


* Namhyung Kim <namhyung@...il.com> wrote:

> The %pT format specifier is for stack backtrace. Its handler
> sprint_trace() does symbol lookup using (address-1) to ensure
> the address will not point outside of the function.
> 
> If there is a tail-call to the function marked "noreturn",
> gcc optimized out the code after the call then causes saved
> return address points outside of the function (i.e. the start
> of the next function), so pollutes call trace somewhat.
> This patch will fix it.
> 
> Signed-off-by: Namhyung Kim <namhyung@...il.com>
> Cc: linux-arch@...r.kernel.org
> ---
>  include/linux/kallsyms.h |    7 +++++++
>  kernel/kallsyms.c        |   40 ++++++++++++++++++++++++++++++++++++++++
>  lib/vsprintf.c           |    7 ++++++-
>  3 files changed, 53 insertions(+), 1 deletions(-)

Looks useful. Please include before/after stack dump examples in the changelog, 
to show the difference.

Thanks,

	Ingo
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