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@xxxxxxxxxxxxx> 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@xxxxxxxxx/ 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?
