> > I'm happy to talk about the kernel-side of arm64 live patching; it'd be good to > > get in contact with anyone looking at the arm64 userspace side (e.g. > > klp-convert). > > > > I have some topics which overlap between live-patching and general toolchain > > bits and pieces, and I'm not sure if they'd be best suited here or in a > > toolchain track, e.g. > > > > * How to avoid/minimize the need to reverse-engineer control flow for things > > like ORC generation. > > > > On the arm64 side we're pretty averse to doing this to generate metadata for > > unwinding (and we might not need to), but there are things objtool does today > > that requires awareness of control-flow (e.g. forward-edge checks for noinstr > > safety). > > > > Hopefully without a flamewar about DWARF... > > > > * Better compiler support for noinstr and similar properties. > > > > For example, noinstr functions are currently all noinline, and we can't > > inline a noinstr function into a noinstr function, leading to a painful mix > > of noinstr and __always_inline. Having a mechanism to allow noinstr code to > > be inlined into other noinstr code would be nice. > > > > Likewise, whether we could somehow get compile-time warnings about unintended > > calls from instrumentable code from noinstr code. > > > > * How is this going to work with rust? > > > > It's not clear to me whether/how things like ftrace, RELIABLE_STACKTRACE, and > > live-patching are going to work with rust. We probably need to start looking > > soon. > > > > I've Cc'd Nick, Jose, and Miguel, in case they have thoughts. > > We have indeed submitted a proposal for a Toolchains MC for Plumbers. Great. > I think the two first topics mentioned above (CFG in ELF and handling of > noinstr functions) would definitely fit well in the Toolchains MC. Yes. > As for Rust... we have the Rust GCC support and that would fit in the MC > as well. We can surely invite some of the hackers working in the > front-end. But maybe it would be better to have that discussion in a > Rust MC, if there is gonna be one (Miguel?). I would definitely welcome a session which Mark proposed. Be it at Live Patching MC or Rust MC. I know next to nothing about how Rust is wired into the kernel and what impact it might have on us. The sooner we understand possible issues, the better. > For starters, I would make sure that the involved MCs (Live Patching, > Toolchains, and an eventual Rust MC) do not overlap in the schedule. > Then we could have these discussions in either microconferences. Agreed. Miroslav
