linux-kernel - [PATCH -tip 1/3] kprobes: Hide CONFIG_OPTPROBES and set if arch support optimized kprobes

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Date:	Fri, 12 Mar 2010 18:22:09 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>
Cc:	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Dieter Ries <mail@...terries.net>, Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>
Subject: [PATCH -tip 1/3] kprobes: Hide CONFIG_OPTPROBES and set if arch
	support optimized kprobes

Hide CONFIG_OPTPROBES and set if arch support optimized kprobes, since
this option doesn't change the behavior of kprobes, but just reduces
the overhead.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Dieter Ries <mail@...terries.net>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
---

 Documentation/kprobes.txt |   10 ++--------
 arch/Kconfig              |    6 ++----
 2 files changed, 4 insertions(+), 12 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..12f9dcc 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -42,11 +42,9 @@ 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


-- 
Masami Hiramatsu
e-mail: mhiramat@...hat.com
--
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