On 10/8/26 00:20, [email protected] wrote: >> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c >> index a805a5b73303f..80928401830c7 100644 >> --- a/kernel/trace/bpf_trace.c >> +++ b/kernel/trace/bpf_trace.c >> @@ -3759,26 +3759,46 @@ static int >> bpf_tracing_multi_link_fill_link_info(const struct bpf_link *link, >> } >> >> #ifdef CONFIG_PROC_FS >> +static const char *bpf_prog_func_name(struct bpf_prog *prog, u32 btf_id) >> +{ >> + const struct btf *btf = prog->aux->btf; >> + const struct btf_type *t; >> + >> + t = btf_type_by_id(btf, btf_id); >> + if (!t || !btf_type_is_func(t)) >> + return ""; >> + >> + return btf_name_by_offset(btf, t->name_off); >> +} >> + >> static void bpf_tracing_multi_show_fdinfo(const struct bpf_link *link, >> struct seq_file *seq) >> { >> struct bpf_tracing_multi_link *tr_link = >> container_of(link, struct bpf_tracing_multi_link, link); >> bool has_cookies = !!tr_link->cookies; >> + bool has_progs = !!tr_link->progs; >> >> seq_printf(seq, "attach_type:\t%u\n", tr_link->link.attach_type); >> seq_printf(seq, "cnt:\t%u\n", tr_link->nodes_cnt); >> >> - seq_printf(seq, "%s\t %s\t %s\t %s\n", "obj-id", "btf-id", "cookie", >> "func"); >> + seq_printf(seq, "%s\t %s\t %s\t %s\n", has_progs ? "prog-id" : >> "obj-id", "btf-id", "cookie", >> + "func"); >> for (int i = 0; i < tr_link->nodes_cnt; i++) { >> struct bpf_tracing_multi_node *mnode = &tr_link->nodes[i]; >> + u64 cookie = has_cookies ? tr_link->cookies[i] : 0; >> u32 btf_id, obj_id; >> >> bpf_trampoline_unpack_key(mnode->trampoline->key, &obj_id, >> &btf_id); >> + btf_id = has_progs ? (u32) mnode->trampoline->key : btf_id; > ^^^^ > > This isn't a bug, but since bpf_trampoline_unpack_key() only masks off > bit 31, which is never set for prog targets, does this re-assignment > change anything, or could the unpacked value be used directly? > > bpf_trampoline_unpack_key() already sets btf_id = key & 0x7FFFFFFF, and > bit 31 is only set by the !tgt_prog branch of bpf_trampoline_compute_key() > (the kernel-BTF case). > > In the has_progs case the key was built as: > > ((u64)tgt_prog->aux->id << 32) | ids[i] > > and ids[i] must be a valid BTF type id (<= BTF_MAX_TYPE, 0xfffff) or > bpf_check_attach_target() would have rejected the attach, so (u32)key > and the unpacked btf_id are always equal here. >
Good catch. Will drop this line. >> + if (has_progs) >> + seq_printf(seq, "%u\t %u\t %llu\t %s\n", >> + obj_id, btf_id, cookie, >> + bpf_prog_func_name(tr_link->progs[i], >> btf_id)); >> + else >> + seq_printf(seq, "%u\t %u\t %llu\t %pS\n", >> + obj_id, btf_id, cookie, >> + (void *) mnode->trampoline->ip); >> >> cond_resched(); >> } > > The commit message shows the sample fdinfo output but doesn't say much > about the implementation or why this change is needed. In particular: > >> Show the target bpf prog info in the fdinfo. >> >> $ cat /proc/self/fdinfo/13 >> pos: 0 >> flags: 02000000 >> mnt_id: 18 >> ino: 1045 >> link_type: tracing_multi >> link_id: 9 >> prog_tag: 9a7f9e3ab6f138ab >> prog_id: 25 >> attach_type: 61 >> cnt: 2 >> prog-id btf-id cookie func >> 21 4 16706819 target_1 >> 22 5 16706819 target_2 > > This isn't a bug, but could the changelog say why the trampoline ip is > not usable as the func column for prog targets (tr->ip is 0 for JIT'd > prog addresses), rather than mostly showing the resulting output? It > also doesn't mention that the first column header changes from "obj-id" > to "prog-id" for prog-target links. > Hmm, will describe the change in the commit msg. Thanks, Leon > > --- > AI reviewed your patch. Please fix the bug or email reply why it's not a bug. > See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md > > CI run summary: https://github.com/kernel-patches/bpf/actions/runs/31320427087
