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    Subject[tip:perf/core] ftrace/x86-64: Allow to change RIP in handlers
    Commit-ID:  47d5a5f88b9d25d6464c9b60c28f391e84e3ed65
    Gitweb: http://git.kernel.org/tip/47d5a5f88b9d25d6464c9b60c28f391e84e3ed65
    Author: Steven Rostedt <rostedt@goodmis.org>
    AuthorDate: Wed, 5 Sep 2012 23:31:18 +0900
    Committer: Steven Rostedt <rostedt@goodmis.org>
    CommitDate: Thu, 13 Sep 2012 22:52:10 -0400

    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>
    ---
    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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