[3.8.y.z extended stable] Patch "ftrace/x86: skip over the breakpoint for ftrace caller" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ftrace/x86: skip over the breakpoint for ftrace caller

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.14.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 94516323d45f77d4bc859ccc84a642c6a546ad5c Mon Sep 17 00:00:00 2001
From: Kevin Hao <haokexin at gmail.com>
Date: Wed, 23 Oct 2013 20:58:16 +0800
Subject: ftrace/x86: skip over the breakpoint for ftrace caller

commit ab4ead02ec235d706d0611d8741964628291237e upstream.

In commit 8a4d0a687a59 "ftrace: Use breakpoint method to update ftrace
caller", we choose to use breakpoint method to update the ftrace
caller. But we also need to skip over the breakpoint in function
ftrace_int3_handler() for them. Otherwise weird things would happen.

Signed-off-by: Kevin Hao <haokexin at gmail.com>
Signed-off-by: Steven Rostedt <rostedt at goodmis.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/x86/kernel/ftrace.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 1d41402..8d5d9e5 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -248,6 +248,15 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	return ret;
 }

+static int is_ftrace_caller(unsigned long ip)
+{
+	if (ip == (unsigned long)(&ftrace_call) ||
+		ip == (unsigned long)(&ftrace_regs_call))
+		return 1;
+
+	return 0;
+}
+
 /*
  * A breakpoint was added to the code address we are about to
  * modify, and this is the handle that will just skip over it.
@@ -257,10 +266,13 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
  */
 int ftrace_int3_handler(struct pt_regs *regs)
 {
+	unsigned long ip;
+
 	if (WARN_ON_ONCE(!regs))
 		return 0;

-	if (!ftrace_location(regs->ip - 1))
+	ip = regs->ip - 1;
+	if (!ftrace_location(ip) && !is_ftrace_caller(ip))
 		return 0;

 	regs->ip += MCOUNT_INSN_SIZE - 1;
--
1.8.3.2