[PATCH 3.12 077/116] ftrace/x86: skip over the breakpoint for ftrace caller

[Greg Kroah-Hartman]

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kevin Hao <haokexin@xxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/kernel/ftrace.c |   14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -248,6 +248,15 @@ int ftrace_update_ftrace_func(ftrace_fun
 	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_fun
  */
 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;


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