linux-kernel - [RFC PATCH -tip 11/16] tracing/docs: add explanation about disassembler interface

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Message-ID: <20120401160411.4502.77554.stgit@shimauta>
Date:	Mon, 02 Apr 2012 01:04:11 +0900
From:	Masami Hiramatsu <masami.hiramatsu@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Huang Ying <ying.huang@...el.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [RFC PATCH -tip 11/16] tracing/docs: add explanation about
 disassembler interface

Add an entry for explaining x86 disassembler interface
to kprobetrace.txt, because that is very useful for
someone who wants to put a probe on somewhere without
using perf-probe.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu@...il.com>
---
 Documentation/trace/kprobetrace.txt |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index d0d0bb9..1dc7b44 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -92,6 +92,20 @@ Event Profiling
 the third is the number of probe miss-hits.
 
 
+Function disassembling
+----------------------
+ To find a probe target, you have two options.
+1) Use perf-probe in perftools. This allows you to find a probe target
+ by using source-code level information.
+2) Use a kernel function disassembling interface on debugfs.
+The first one is easy to use, very helpful for noraml user, but also
+requires kernel debuginfo package (or built binary with CONFIG_DEBUGINFO).
+The second one is easy to use, but requires a knowladge of assembly
+language (and also, this is currently available on x86 with
+CONFIG_X86_DISASSEMBLER=y and CONFIG_DEBUG_X86_DISASSEMBLY=y).
+The debugfs interface is /sys/kernel/debug/x86/disassembly. At first,
+you should write a function name to the file, and then, read it.
+
 Usage examples
 --------------
 To add a probe as a new event, write a new definition to kprobe_events

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