On Fri, Oct 22, 2021 at 4:33 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > On Thu, Oct 21, 2021 at 04:42:12PM -0700, Alexei Starovoitov wrote: > > > Ahh. Right. It's potentially a different offset for every prog. > > Let's put it into struct jit_context then. > > Something like this... Yep. Looks nice and clean to me. > - poke->tailcall_bypass = image + (addr - poke_off - X86_PATCH_SIZE); > + poke->tailcall_bypass = ip + (prog - start); > poke->adj_off = X86_TAIL_CALL_OFFSET; > - poke->tailcall_target = image + (addr - X86_PATCH_SIZE); > + poke->tailcall_target = ip + ctx->tail_call_direct_label - X86_PATCH_SIZE; This part looks correct too, but this is Daniel's magic. He'll probably take a look next week when he comes back from PTO. I don't recall which test exercises this tailcall poking logic. It's only used with dynamic updates to prog_array. insmod test_bpf.ko and test_verifier won't go down this path.
