On April 14, 2023 4:04:36 PM GMT-03:00, Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx> wrote: >On Fri, Apr 14, 2023 at 7:12 PM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: >> >> Not to mention how objtool will react to compiled rust code (has it >> already been tried?) > >Rust uses LLVM, so it should be generally fine -- at least some of the >checks appear to work. For instance, I can trigger: > > RUSTC L rust/kernel.o > rust/kernel.o: warning: objtool: .text+0x0: unreachable instruction > > RUSTC [M] samples/rust/rust_minimal.o > samples/rust/rust_minimal.o: warning: objtool: >_R..._6kernel6Module4init+0x172: unreachable instruction > >via a random instruction in the middle of nowhere in the former (with >`global_asm!`) and a jumped-over instruction in the latter (with >`asm!`). > >Moreover, we were already getting warnings when rethunk / x86 IBT is >enabled (since we got `objtool` called for `vmlinux.o`), e.g. > > vmlinux.o: warning: objtool: .rodata+0x18c58: data relocation to >!ENDBR: _R...IsWhitespaceEEB4_+0x0 > > vmlinux.o: warning: objtool: _R...into_foreign+0x5: 'naked' return >found in RETHUNK build > >I can send the patch to run it for all Rust object files via >`$(cmd_objtool)`, unless you think it is a bad idea. > >Having said that, tooling may indeed have issues, e.g. Arnaldo (Cc'd) >is improving `pahole` to avoid assumptions around struct layout like >field reordering (which Rust does by default). That part should be dealt with the recently released pahole 1.25: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=c4eb1897d1f3841d291ee39dc969c4212750cf2c https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=1231b6b9b4d88e0084bef4254eb1a05eb9935c99 But there are more issues, I'll resume work on Rust soon, after a detour on Go, and I think the changes made for Go make the DWARF loading more robust and may even have helped with Rust already: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?h=next&id=31bc0d7410572f6e03e3ed9da7c8c6f0d8df23c8 - Arnaldo > >Cheers, >Miguel
