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

[Masami Hiramatsu]

From: Steven Rostedt <rostedt@xxxxxxxxxxx>

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@xxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
---

 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

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