On Tue, Jan 14, 2025 at 03:17:23PM +0100, Peter Zijlstra wrote: > On Tue, Jan 14, 2025 at 03:02:37PM +0100, Jiri Olsa wrote: > > hi, > > while checking on similar code for uprobes I was wondering if we > > can merge first 2 steps of instruction update in text_poke_bp_batch > > function. > > > > Basically the first step now would be to write int3 byte together > > with the rest of the bytes of the new instruction instead of doing > > that separately. And the second step would be to overwrite int3 > > byte with first byte of the new instruction. > > > > Would that work or do I miss some x86 detail that could lead to crash? > > I *think* it will work on most modern systems, but I'm very sure I don't > have all the details. > > IIRC this is the magic recipe blessed by both Intel and AMD, and > if we're going to be changing this I would want both vendors to sign off > on that. ok > > > I tried to hack it together in attached patch and it speeds up a bit > > text_poke_bp_batch as shown below. > > Why do we care about performance here? just a benefit of doing that change.. but mainly I was just curious on why those first steps are separated thanks, jirka
