From: Steven Rostedt <rostedt@goodmis.org>
Date: Wed, 5 Sep 2012 14:31:18 +0000 (+0900)
Subject: ftrace/x86-64: Allow to change RIP in handlers
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=47d5a5f88b9d25d6464c9b60c28f391e84e3ed65;p=openwrt%2Fstaging%2Fblogic.git

ftrace/x86-64: Allow to change RIP in handlers

Allow ftrace handlers to change RIP register (regs->ip)
in handlers. This will allow handlers to call another
function instead of original function.

Link: http://lkml.kernel.org/r/20120905143118.10329.5078.stgit@localhost.localdomain

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index ed767b747fe5..e9cc2b32bdf4 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -165,6 +165,10 @@ GLOBAL(ftrace_regs_call)
 	movq EFLAGS(%rsp), %rax
 	movq %rax, SS(%rsp)
 
+	/* Handlers can change the RIP */
+	movq RIP(%rsp), %rax
+	movq %rax, SS+8(%rsp)
+
 	/* restore the rest of pt_regs */
 	movq R15(%rsp), %r15
 	movq R14(%rsp), %r14