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    Subject[PATCH -tip 1/3] kprobes: Hide CONFIG_OPTPROBES and set if arch support optimized kprobes
    Date
    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@redhat.com>
    Cc: Dieter Ries <mail@dieterries.net>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Ananth N Mavinakayanahalli <ananth@in.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@redhat.com


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