Messages in this thread | | | Date | Tue, 07 Aug 2012 13:23:54 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [RFC PATCH 0/4] ftrace: Add use of -mfentry for x86_64 |
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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 <hpa@linux.intel.com>
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
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