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?
