Merge branch 'perf'

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.

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

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"

  $retval	: Fetch return value.(*)

  +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**)

  NAME=FETCHARG : Set NAME as the argument name of FETCHARG.

  FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types

		  (u8/u16/u32/u64/s8/s16/s32/s64) are supported.

  (*) only for return probe.

  (**) this is useful for fetching a field of data structures.

M:	Ingo Molnar <mingo@elte.hu>

M:	Arnaldo Carvalho de Melo <acme@redhat.com>

S:	Supported

F:	kernel/perf_event.c

F:	kernel/perf_event*.c

F:	include/linux/perf_event.h

F:	arch/*/kernel/perf_event.c

F:	arch/*/kernel/*/perf_event.c

F:	arch/*/kernel/*/*/perf_event.c

F:	arch/*/kernel/perf_event*.c

F:	arch/*/kernel/*/perf_event*.c

F:	arch/*/kernel/*/*/perf_event*.c

F:	arch/*/include/asm/perf_event.h

F:	arch/*/lib/perf_event.c

F:	arch/*/lib/perf_event*.c

F:	arch/*/kernel/perf_callchain.c

F:	tools/perf/

	  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

	select HAVE_ARCH_KMEMCHECK

	select HAVE_USER_RETURN_NOTIFIER

config INSTRUCTION_DECODER

	def_bool (KPROBES || PERF_EVENTS)

config OUTPUT_FORMAT

	string

	default "elf32-i386" if X86_32