linux-kernel - Re: [PATCH] ftrace: powerpc: remove startup functions from tracing

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Date:	Fri, 17 Oct 2008 11:50:46 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Josh Boyer <jwboyer@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, David Miller <davem@...emloft.net>,
	linuxppc-dev@...abs.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] ftrace: powerpc: remove startup functions from tracing

On Thu, 2008-10-16 at 20:48 -0400, Steven Rostedt wrote:
> 
> The early init code in PowerPC is not mapped to their final locations
> and all jumps and memory references must be done with relative jumps
> and accesses.
> 
> The lib files in the powerpc directory are called in early boot, and
> since mcount will perform direct access to memory, the lib files need
> not be traced.

This is annoying though, because that means things like memcpy,
copy_to_from_user etc... can't be traced. On the other hand a lot
of that is asm and already doesn't call mcount.

Cheers,
Ben.


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