linux-kernel - Re: [PATCH v7 4/7] arm64: Add ftrace support

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Message-ID: <20140416134506.GD1001@arm.com>
Date:	Wed, 16 Apr 2014 14:45:06 +0100
From:	Will Deacon <will.deacon@....com>
To:	AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:	"rostedt@...dmis.org" <rostedt@...dmis.org>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"tim.bird@...ymobile.com" <tim.bird@...ymobile.com>,
	"gkulkarni@...iumnetworks.com" <gkulkarni@...iumnetworks.com>,
	"dsaxena@...aro.org" <dsaxena@...aro.org>,
	"arndb@...db.de" <arndb@...db.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 4/7] arm64: Add ftrace support

On Sat, Mar 15, 2014 at 05:45:50AM +0000, AKASHI Takahiro wrote:
> This patch implements arm64 specific part to support function tracers,
> such as function (CONFIG_FUNCTION_TRACER), function_graph
> (CONFIG_FUNCTION_GRAPH_TRACER) and function profiler
> (CONFIG_FUNCTION_PROFILER).
> 
> With 'function' tracer, all the functions in the kernel are traced with
> timestamps in ${sysfs}/tracing/trace. If function_graph tracer is
> specified, call graph is generated.
> 
> The kernel must be compiled with -pg option so that _mcount() is inserted
> at the beginning of functions. This function is called on every function's
> entry as long as tracing is enabled.
> In addition, function_graph tracer also needs to be able to probe function's
> exit. ftrace_graph_caller() & return_to_handler do this by faking link
> register's value to intercept function's return path.
> 
> More details on architecture specific requirements are described in
> Documentation/trace/ftrace-design.txt.
> 
> Reviewed-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>

I'm still slightly suspicious about the alignment of your ASCII art, but:

  Acked-by: Will Deacon <will.deacon@....com>

Will
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