On Fri, Sep 19, 2025 at 07:56:20PM -0700, Alexei Starovoitov wrote: > On Fri, Sep 19, 2025 at 12:19 AM Feng Yang <[email protected]> wrote: > > > > When I use bpf_program__attach_kprobe_multi_opts to hook a BPF program that > > contains the bpf_get_stackid function on the arm64 architecture, > > I find that the stack trace cannot be obtained. The trace->nr in > > __bpf_get_stackid is 0, and the function returns -EFAULT. > > > > For example: > > diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi.c > > b/tools/testing/selftests/bpf/progs/kprobe_multi.c > > index 9e1ca8e34913..844fa88cdc4c 100644 > > --- a/tools/testing/selftests/bpf/progs/kprobe_multi.c > > +++ b/tools/testing/selftests/bpf/progs/kprobe_multi.c > > @@ -36,6 +36,15 @@ __u64 kretprobe_test6_result = 0; > > __u64 kretprobe_test7_result = 0; > > __u64 kretprobe_test8_result = 0; > > > > +typedef __u64 stack_trace_t[2]; > > + > > +struct { > > + __uint(type, BPF_MAP_TYPE_STACK_TRACE); > > + __uint(max_entries, 1024); > > + __type(key, __u32); > > + __type(value, stack_trace_t); > > +} stacks SEC(".maps"); > > + > > static void kprobe_multi_check(void *ctx, bool is_return) > > { > > if (bpf_get_current_pid_tgid() >> 32 != pid) > > @@ -100,7 +109,9 @@ int test_kretprobe(struct pt_regs *ctx) > > SEC("kprobe.multi") > > int test_kprobe_manual(struct pt_regs *ctx) > > { > > + int id = bpf_get_stackid(ctx, &stacks, 0); > > ftrace_partial_regs() supposed to work on x86 and arm64, > but since multi-kprobe is the only user... > I suspect the arm64 implementation wasn't really tested. > Or maybe there is some other issue. > > Masami, Jiri, > thoughts?
hi, I did quick test for kprobe multi and I can reproduce the issue on arm64 with ci: https://github.com/kernel-patches/bpf/pull/9809 but can't really tell what's missing on arm side.. cc-ing Will thanks, jirka
