* H. Peter Anvin <h...@zytor.com> wrote:
> On 08/07/2012 12:38 PM, Steven Rostedt wrote:
> >
> >This is an RFC patch set that makes gcc use the -mfentry option with
> >-pg. This will set the ftrace 'hook' to the beginning of the function
> >and also remove the requirement that -pg enables frame pointers.
> >
> >This has a couple of benefits (and probably more).
> >
> >1) removal of the frame pointer requirement makes for smaller and faster
> >code.
> >
> >2) Having the function trace hook at the beginning of the function instead
> > of after the frame is set up, gives the function tracing callbacks access
> > to the parameters. This means that kprobes can take advantage of this.
> > When a kprobe is set on top of a ftrace hook (nop), it will automatically
> > use the function tracing callback. This makes it into an 'optimized' probe
> > as there's no need to hit a breakpoint and trigger the probe that way.
> > The function tracing code can do the work for it. Note, optimized probes
> > are only allowed with !PREEMPT, but a ftrace optimize probe is allowed
> > in any context (another benefit).
> >
> >This only implements fentry for x86_64.
> >
>
> Acked-by: H. Peter Anvin <h...@linux.intel.com>
Acked-by: Ingo Molnar <mi...@kernel.org>
Nice feature!
Thanks,
Ingo
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