I checked with Will about it and learnt that ARM64 does support patching certain instructions (e.g. branch, brk, nops) using aarch64_insn_patch_text_nosync, it's used in ftrace: https://elixir.bootlin.com/linux/latest/source/arch/arm64/kernel/ftrace.c#L24 But one has to tolerate that not all CPUs will execute these instructions until a context synchronization happens due to an exception or an ISB instruction. But I think we can start with the same thing that FTrace does? - KP On Wed, Feb 24, 2021 at 10:01 PM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote: > > On 2/24/21 8:54 PM, Luigi Rizzo wrote: > > I prepared a BPF version of kstats[1] > > https://github.com/luigirizzo/lr-cstats > > that uses fentry/fexit hooks to monitor the execution time > > of a kernel function. > > > > I hoped to have it working on ARM64 too, but it looks like > > arch_prepare_bpf_trampoline() only exists for x86. > > > > Is there any outstanding patch for this function on ARM64, > > or any similar function I could look at to implement it myself ? > > Not that I'm currently aware of, arm64 support would definitely be great > to have. From x86 side, the underlying arch dependency was basically on > text_poke_bp() to patch instructions on a live kernel. Haven't checked > recently whether an equivalent exists on arm64 yet, but perhaps Will > might know. > > > [1] kstats is an in-kernel also in the above repo and previously > > discussed at https://lwn.net/Articles/813303/ >
