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    SubjectRe: [PATCH -v4 4/9] tracing: add static function tracer support for MIPS
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    On Thu, 2009-10-22 at 17:55 -0400, Steven Rostedt wrote:
    > On Thu, 2009-10-22 at 14:29 -0700, Adam Nemet wrote:
    > > Steven Rostedt writes:
    > > > On Thu, 2009-10-22 at 13:30 -0700, Adam Nemet wrote:
    > > > > Also note that for functions invoked via tail call you won't get an exit
    > > > > event. E.g. if bar is tail-called from foo:
    > > > >
    > > > > foo entered
    > > > > bar entered
    > > > > foo/bar exited
    > > > >
    > > > > However, this is not MIPS-specific and you can always disable tail calls
    > > > > with -fno-optimize-sibling-calls.
    > > >
    > > > The question is, would bar have a _mcount call? So far, we have not had
    > > > any issues with this on either x86 nor PPC.
    > >
    > > Yes, bar will have an _mcount call. The difference is that bar will return to
    > > foo's caller directly rather than to foo first.
    >
    > I guess the best bet is to have CONFIG_FUNCTION_GRAPH enable
    > -fno-optimize-sibling-calls and be done with it.
    >

    Hello, This did for us:

    Makefile:

    ifdef CONFIG_FRAME_POINTER
    KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
    else
    KBUILD_CFLAGS += -fomit-frame-pointer
    endif

    So, the only thing we need to do is enabling CONFIG_FRAME_POINTER.
    Seems it was selected by FTRACE by default.

    Regards,
    Wu Zhangjin



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