On Fri, Jan 26, 2024 at 5:24 AM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> On Thu, 2024-01-25 at 12:55 -0800, Andrii Nakryiko wrote:
> [...]
>
> > @@ -6379,11 +6388,21 @@ static bool need_func_arg_type_fixup(const struct btf *btf, const struct bpf_pro
> > /* special cases */
> > switch (prog->type) {
> > case BPF_PROG_TYPE_KPROBE:
> > - case BPF_PROG_TYPE_PERF_EVENT:
> > /* `struct pt_regs *` is expected, but we need to fix up */
> > if (btf_is_struct(t) && strcmp(tname, "pt_regs") == 0)
> > return true;
> > break;
>
> Sorry, this was probably discussed, but I got lost a bit.
> Kernel side does not change pt_regs for BPF_PROG_TYPE_KPROBE
> (in ./kernel/bpf/btf.c:btf_validate_prog_ctx_type)
> but here we do, why do it differently?
>
Hm... We do the same. After this patch w end up with this logic on
libbpf side (which matches kernel-side one, I believe):
for KPROBE => allow pt_regs (unconditionally)
for PERF_EVENT => allow user_regs_struct|user_pt_regs|pt_regs,
depending on bpf_user_pt_regs_t definition on host platform
That should match what the kernel is doing.
> [...]
