On Sat, Feb 20, 2021 at 01:39:20AM +0100, Borislav Petkov wrote: > On Fri, Feb 19, 2021 at 11:01:58PM +0100, Peter Zijlstra wrote: > > We could, but it so happens Joerg is also wanting negative features. > > Juergen.
Argh! I should stick to jgross. Sorry. > > So I was thikning that perhaps we can convince Boris they're not > > really all that aweful after all :-) > > Well, I'm not crazy about this, TBH - I totally agree with Josh: > > "with objtool generating code, it's going to be a maze to figure out > where the generated code is coming from" > > and without a real good reason to do this, what's the point? I know, > because we can. :-) Well: - straight line execution is always better than a round-trip to somewhere else, no matter how trivial. - supposely EIBRS (yeah, I know, there's a paper out there) should result in no longer using retpolines. - I really, as in _REALLY_ don't want to do a CET enabled retpoline - IOW, retpolines should be on their way out (knock on wood) - doing this was fun :-) - this stuff was mostly trivial make work stuff I could do with a head full of snot and a headache. - if we had negative alternatives objtool doesn't need to actually rewrite code in this case. It could simply emit alternative entries and call it a day. - objtool already rewrites code - I have more cases for objtool to rewrite code (I'll see if I can rebase and post that this weekend -- no promises). - also https://lkml.kernel.org/r/20200625200235.gq4...@hirez.programming.kicks-ass.net
