On 11 November 2018 at 00:20, Peter Zijlstra <pet...@infradead.org> wrote: > On Fri, Nov 09, 2018 at 02:50:27PM +0100, Ard Biesheuvel wrote: >> On 9 November 2018 at 08:28, Ingo Molnar <mi...@kernel.org> wrote: >> >> - I'm not sure about the objtool approach. Objtool is (currently) >> >> x86-64 only, which means we have to use the "unoptimized" version >> >> everywhere else. I may experiment with a GCC plugin instead. >> > >> > I'd prefer the objtool approach. It's a pretty reliable first-principles >> > approach while GCC plugin would have to be replicated for Clang and any >> > other compilers, etc. >> > >> >> I implemented the GCC plugin approach here for arm64 > > I'm confused; I though we only needed objtool for variable instruction > length architectures, because we can't reliably decode our instruction > stream. Otherwise we can fairly trivially use the DWARF relocation data, > no?
How would that work? We could build vmlinux with --emit-relocs, filter out the static jump/call relocations and resolve the symbol names to filter the ones associated with calls to trampolines. But then, we have to build the static_call_sites section and reinject it back into the image in some way, which is essentially objtool, no?
