From: Steven Rostedt <srostedt@redhat.com>
Date: Tue, 16 Aug 2011 13:57:10 +0000 (-0400)
Subject: ftrace/x86: Have arch x86_64 use breakpoints instead of stop machine
X-Git-Tag: v3.5-rc1~141^2~37^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=08d636b6d4fb80647fe8869ea1cd97b2c26a4751;p=pandora-kernel.git

ftrace/x86: Have arch x86_64 use breakpoints instead of stop machine

This method changes x86 to add a breakpoint to the mcount locations
instead of calling stop machine.

Now that iret can be handled by NMIs, we perform the following to
update code:

1) Add a breakpoint to all locations that will be modified

2) Sync all cores

3) Update all locations to be either a nop or call (except breakpoint
   op)

4) Sync all cores

5) Remove the breakpoint with the new code.

6) Sync all cores

[
  Added updates that Masami suggested:
   Use unlikely(modifying_ftrace_code) in int3 trap to keep kprobes efficient.
   Don't use NOTIFY_* in ftrace handler in int3 as it is not a notifier.
]

Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

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