linux-kernel - [tip:perf/core] kprobes: Hide CONFIG_OPTPROBES and set if arch supports optimized kprobes

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Message-ID: <tip-5cc718b9dad682329a60e73547c6e708faa5bbe4@git.kernel.org>
Date:	Tue, 16 Mar 2010 14:47:53 GMT
From:	tip-bot for Masami Hiramatsu <mhiramat@...hat.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	acme@...hat.com, mingo@...hat.com, a.p.zijlstra@...llo.nl,
	mail@...terries.net, efault@....de, fweisbec@...il.com,
	dle-develop@...ts.sourceforge.net, hirofumi@...l.parknet.co.jp,
	tglx@...utronix.de, mhiramat@...hat.com,
	systemtap@...rces.redhat.com, hpa@...or.com, paulus@...ba.org,
	linux-kernel@...r.kernel.org, ananth@...ibm.com, mingo@...e.hu
Subject: [tip:perf/core] kprobes: Hide CONFIG_OPTPROBES and set if arch supports optimized kprobes

Commit-ID:  5cc718b9dad682329a60e73547c6e708faa5bbe4
Gitweb:     http://git.kernel.org/tip/5cc718b9dad682329a60e73547c6e708faa5bbe4
Author:     Masami Hiramatsu <mhiramat@...hat.com>
AuthorDate: Mon, 15 Mar 2010 13:00:54 -0400
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 16 Mar 2010 11:07:23 +0100

kprobes: Hide CONFIG_OPTPROBES and set if arch supports optimized kprobes

Hide CONFIG_OPTPROBES and set if the arch supports optimized
kprobes (IOW, HAVE_OPTPROBES=y), since this option doesn't
change the major behavior of kprobes, and workarounds for minor
changes are documented.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: systemtap <systemtap@...rces.redhat.com>
Cc: DLE <dle-develop@...ts.sourceforge.net>
Cc: Dieter Ries <mail@...terries.net>
Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Mike Galbraith <efault@....de>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
LKML-Reference: <20100315170054.31593.3153.stgit@...alhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 Documentation/kprobes.txt |   10 ++--------
 arch/Kconfig              |    9 ++-------
 2 files changed, 4 insertions(+), 15 deletions(-)

diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
index 2f9115c..61c291c 100644
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -165,8 +165,8 @@ the user entry_handler invocation is also skipped.
 
 1.4 How Does Jump Optimization Work?
 
-If you configured your kernel with CONFIG_OPTPROBES=y (currently
-this option is supported on x86/x86-64, non-preemptive kernel) and
+If your kernel is built with CONFIG_OPTPROBES=y (currently this flag
+is automatically set 'y' on x86/x86-64, non-preemptive kernel) and
 the "debug.kprobes_optimization" kernel parameter is set to 1 (see
 sysctl(8)), Kprobes tries to reduce probe-hit overhead by using a jump
 instruction instead of a breakpoint instruction at each probepoint.
@@ -271,8 +271,6 @@ tweak the kernel's execution path, you need to suppress optimization,
 using one of the following techniques:
 - Specify an empty function for the kprobe's post_handler or break_handler.
  or
-- Config CONFIG_OPTPROBES=n.
- or
 - Execute 'sysctl -w debug.kprobes_optimization=n'
 
 2. Architectures Supported
@@ -307,10 +305,6 @@ it useful to "Compile the kernel with debug info" (CONFIG_DEBUG_INFO),
 so you can use "objdump -d -l vmlinux" to see the source-to-object
 code mapping.
 
-If you want to reduce probing overhead, set "Kprobes jump optimization
-support" (CONFIG_OPTPROBES) to "y". You can find this option under the
-"Kprobes" line.
-
 4. API Reference
 
 The Kprobes API includes a "register" function and an "unregister"
diff --git a/arch/Kconfig b/arch/Kconfig
index e5eb133..f06010f 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -42,15 +42,10 @@ config KPROBES
 	  If in doubt, say "N".
 
 config OPTPROBES
-	bool "Kprobes jump optimization support (EXPERIMENTAL)"
-	default y
-	depends on KPROBES
+	def_bool y
+	depends on KPROBES && HAVE_OPTPROBES
 	depends on !PREEMPT
-	depends on HAVE_OPTPROBES
 	select KALLSYMS_ALL
-	help
-	  This option will allow kprobes to optimize breakpoint to
-	  a jump for reducing its overhead.
 
 config HAVE_EFFICIENT_UNALIGNED_ACCESS
 	bool
--
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