On Tue, May 12, 2026 at 12:38:34PM -0700, Andrii Nakryiko wrote: > On Tue, May 12, 2026 at 12:27 PM Alexei Starovoitov > <[email protected]> wrote: > > > > On Tue, May 12, 2026 at 10:07 AM Jiri Olsa <[email protected]> wrote: > > > > > > + /* > > > + * We have nop10 (with first byte overwritten to int3), > > > + * change it to: > > > + * lea 0x80(%rsp), %rsp > > > + * call tramp > > > + * > > > + * The first lea instruction skips the stack redzone so the call > > > + * instruction can safely push return address on stack. > > > + */ > > > > typo: lea -128(%rsp), %rsp
ugh, thanks > > > > you can also do: > > > > add $-128, %rsp + call tramp = 4 + 5 = 9 bytes instead of 10. > > When I asked AI about this it explained that add instruction modifies > flags, so it's not a good fit here. lea doesn't touch flags. > > > > > Initially I didn't like this approach, since we just introduced > > usdt nop5 and now need to recompile everything again, > > but looking at the fix it's definitely simpler than alternatives > > and doesn't have annoying limitations. > > > yeah, limitations are annoying, especially with those global "DO NOT > OPTIMIZE" flags... Jiri, let's polish your version and land it? ok, will send it out jirka
