Messages in this thread | | | Date | Mon, 15 Aug 2022 17:02:03 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC] ftrace: Add support to keep some functions out of ftrace |
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On Mon, Aug 15, 2022 at 07:45:16AM -0700, Alexei Starovoitov wrote: > On Mon, Aug 15, 2022 at 7:33 AM Peter Zijlstra <peterz@infradead.org> wrote:
> > It is in full control of the 'call __fentry__'. Absolute full NAK on you > > trying to make it otherwise. > > Don't mix 'call fentry' generated by the compiler with nop5 inserted > by macroses or JITs.
Looking at:
https://lore.kernel.org/all/20191211123017.13212-3-bjorn.topel@gmail.com/
this seems to want to prod at the __fentry__ sites.
> > > Soon we will have nop5 in the middle of the function. > > > ftrace must not touch it. > > > > How are you generating that NOP and what for? > > We're generating nop5-s in JITed code to further > attach to.
Ftrace doesn't know about those; so how can it break that?
Likewise it doesn't know about the static_branch/static_call NOPs and nothing is broken.
Ftrace only knows about the __fentry__ sites, and it *does* own them. Are you saying ftrace is writing to a code location not a __fentry__ site?
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