[PATCH -tip 3/4] ftrace/x86-64: Allow to change RIP in handlers

Masami Hiramatsu
2012-09-05T14:32:45Z

From: Steven Rostedt <rostedt@goodmis.org>

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

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---

arch/x86/kernel/entry_64.S | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index ed767b7..e9cc2b3 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