kprobes: Introduce kprobes jump optimization

Introduce kprobes jump optimization arch-independent parts.
Kprobes uses breakpoint instruction for interrupting execution
flow, on some architectures, it can be replaced by a jump
instruction and interruption emulation code. This gains kprobs'
performance drastically.

To enable this feature, set CONFIG_OPTPROBES=y (default y if the
arch supports OPTPROBE).

Changes in v9:
 - Fix a bug to optimize probe when enabling.
 - Check nearby probes can be optimize/unoptimize when disarming/arming
   kprobes, instead of registering/unregistering. This will help
   kprobe-tracer because most of probes on it are usually disabled.

Changes in v6:
 - Cleanup coding style for readability.
 - Add comments around get/put_online_cpus().

Changes in v5:
 - Use get_online_cpus()/put_online_cpus() for avoiding text_mutex
   deadlock.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Anders Kaseorg <andersk@ksplice.com>
Cc: Tim Abbott <tabbott@ksplice.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
LKML-Reference: <20100225133407.6725.81992.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 9d055b4f0585..e0ad3caf16d9 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -57,6 +57,17 @@ config KPROBES
           for kernel debugging, non-intrusive instrumentation and testing.
           If in doubt, say "N".
 
+config OPTPROBES
+        bool "Kprobes jump optimization support (EXPERIMENTAL)"
+        default y
+        depends on KPROBES
+        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
         help
@@ -99,6 +110,8 @@ config HAVE_KPROBES
 config HAVE_KRETPROBES
         bool
 
+config HAVE_OPTPROBES
+        bool
 #
 # An arch should select this if it provides all these things:
 #