+ arm ML and maintainers On Wed, Sep 4, 2024 at 6:02 PM Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > > Hey, > > I just recently realized that we are still missing multi-kprobe > support for ARM64, which depends on CONFIG_FPROBE. And CONFIG_FPROBE > seems to require CONFIG_HAVE_RETHOOK, which, it turns out, is not > implemented for ARM64. > > It took me a while to realize what's going on, as I roughly remembered > (and confirmed through lore search) that Masami's original rethook > patches had arm64-specific bits. Long story short: > > 0f8f8030038a Revert "arm64: rethook: Add arm64 rethook implementation" > 83acdce68949 arm64: rethook: Add arm64 rethook implementation > > The patch was landed and then reverted. I found some discussion online > and it seems like the plan was to land arch-specific bits shortly > after bpf-next PR. > > But it seems like that never happened. Why? > > I see s390x, RISC-V, loongarch (I'm not even mentioning x86-64) all > have CONFIG_HAVE_RETHOOK, even powerpc is getting one (see [0]), it > seems. How come ARM64 is the one left out? > > Can anyone please provide some context? And if that's just an > oversight, can we prioritize landing this for ARM64 ASAP? > > [0] https://lore.kernel.org/bpf/20240830113131.7597-1-adubey@xxxxxxxxxxxxx/ > Masami, Steven, Does Linus have to be in CC to get any reply here? Come on, it's been almost a full week. Maybe ARM64 folks have some context?... And hopefully desire to see this through so that ARM64 doesn't stick out as a lesser-supported platform as far as tracing goes compared to loongarch, s390x, and powerpc (which just landed rethook support, see [2]). Note that there was already an implementation (see [1]), but for some reason it never made it. [1] https://lore.kernel.org/bpf/164338038439.2429999.17564843625400931820.stgit@devnote2/ [2] https://lore.kernel.org/bpf/172562357215.467568.2172858907419105155.b4-ty@xxxxxxxxxxxxxx/ > > -- Andrii
