linux-kernel - Re: [PATCH] ftrace: handle weak symbol functions

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Message-ID: <20080820145105.GB829@elte.hu>
Date:	Wed, 20 Aug 2008 16:51:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] ftrace: handle weak symbol functions


* Steven Rostedt <rostedt@...dmis.org> wrote:

> During tests and checks, I've discovered that there were failures to 
> convert mcount callers into nops. Looking deeper into these failures, 
> code that was attempted to be changed was not an mcount caller. The 
> current code only updates if the code being changed is what it 
> expects, but I still investigate any time there is a failure.
> 
> What was happening is that a weak symbol was being used as a reference 
> for other mcount callers. That weak symbol was also referenced 
> elsewhere so the offsets were using the strong symbol and not the 
> function symbol that it was referenced from.
> 
> This patch changes the setting up of the mcount_loc section to search 
> for a global function that is not weak. It will pick a local over a 
> weak but if only a weak is found in a section, a warning is printed 
> and the mcount location is not recorded (just to be safe).
> 
> Signed-off-by: Steven Rostedt <srostedt@...hat.com>

applied to tip/tracing/ftrace, thanks Steve!

	Ingo
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