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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@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Dieter Ries <mail@dieterries.net>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100315170054.31593.3153.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Masami Hiramatsu 2010-03-15 13:00:54 -04:00 committed by Ingo Molnar
parent 8ea7f54410
commit 5cc718b9da
2 changed files with 4 additions and 15 deletions
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10
Documentation/kprobes.txt
View File

@ -165,8 +165,8 @@ the user entry_handler invocation is also skipped.
1.4 How Does Jump Optimization Work? 1.4 How Does Jump Optimization Work?
If you configured your kernel with CONFIG_OPTPROBES=y (currently If your kernel is built with CONFIG_OPTPROBES=y (currently this flag
this option is supported on x86/x86-64, non-preemptive kernel) and is automatically set 'y' on x86/x86-64, non-preemptive kernel) and
the "debug.kprobes_optimization" kernel parameter is set to 1 (see the "debug.kprobes_optimization" kernel parameter is set to 1 (see
sysctl(8)), Kprobes tries to reduce probe-hit overhead by using a jump sysctl(8)), Kprobes tries to reduce probe-hit overhead by using a jump
instruction instead of a breakpoint instruction at each probepoint. 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: using one of the following techniques:
- Specify an empty function for the kprobe's post_handler or break_handler. - Specify an empty function for the kprobe's post_handler or break_handler.
or or
- Config CONFIG_OPTPROBES=n.
or
- Execute 'sysctl -w debug.kprobes_optimization=n' - Execute 'sysctl -w debug.kprobes_optimization=n'
2. Architectures Supported 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 so you can use "objdump -d -l vmlinux" to see the source-to-object
code mapping. 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 4. API Reference
The Kprobes API includes a "register" function and an "unregister" The Kprobes API includes a "register" function and an "unregister"

9
arch/Kconfig
View File

@ -42,15 +42,10 @@ config KPROBES
If in doubt, say "N". If in doubt, say "N".
config OPTPROBES config OPTPROBES
bool "Kprobes jump optimization support (EXPERIMENTAL)" def_bool y
default y depends on KPROBES && HAVE_OPTPROBES
depends on KPROBES
depends on !PREEMPT depends on !PREEMPT
depends on HAVE_OPTPROBES
select KALLSYMS_ALL select KALLSYMS_ALL
help
This option will allow kprobes to optimize breakpoint to
a jump for reducing its overhead.
config HAVE_EFFICIENT_UNALIGNED_ACCESS config HAVE_EFFICIENT_UNALIGNED_ACCESS
bool bool