On Wed, Jul 10, 2024 at 9:24 AM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > > On Wed, Jul 10, 2024 at 08:11:57AM -0700, Andrii Nakryiko wrote: > > On Wed, Jul 10, 2024 at 4:39 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > On Tue, Jul 09, 2024 at 10:50:00AM -0700, Andrii Nakryiko wrote: > > > > You can see it replaced the first byte, the following 3 bytes are > > > > remnants of endb64 (gdb says it's a nop? :)), and then we proceeded, > > > > you can see I stepped through a few more instructions. > > > > > > > > Works by accident? > > > > > > Yeah, we don't actually have Userspace IBT enabled yet, even on hardware > > > that supports it. > > > > OK, I don't know what the implications are, but it's a good accident :) > > > > Anyways, what should I do for v4? Drop is_endbr6() check or keep it? > > Given the current behavior of uprobe overwriting ENDBR64 with INT3, the > is_endbr6() check still makes sense, otherwise is_uprobe_at_func_entry() > would never return true on OSes which have the ENDBR64 compiled in. > > However, once userspace IBT actually gets enabled, uprobe should skip > the ENDBR64 and patch the subsequent instruction. Then the is_endbr6() > check would no longer be needed. > Ok, I'll keep it then, thanks. > -- > Josh
