On Fri, Apr 14, 2023 at 10:53:03AM +0100, Mark Rutland wrote: > > Currently proposed topics follow. The list is open though and more will > > be added during the regular Call for Topics. > > > > - klp-convert (as means to fix CET IBT limitations) and its > > upstreamability > > - shadow variables, global state transition > > - kselftests and the future direction of development > > - arm64 live patching > > 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). klp-convert is still considered experimental. FYI here's a pull request which adds arm64 support to kpatch-build: https://github.com/dynup/kpatch/pull/1302 > 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... If objtool is going to be doing control-flow anyway then it could just validate DWARF/SFrame. Then everybody's happy? > * 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. Can you elaborate? Why can't noinstr inline noinstr? (that's a mouthful) Is it because of potential cloning caused by IPA optimizations? > 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. Not to mention how objtool will react to compiled rust code (has it already been tried?) -- Josh
