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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3680dafbf4bsm8185224f8f.73.2024.07.16.00.27.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jul 2024 00:27:07 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 16 Jul 2024 09:27:05 +0200 To: Hou Tao Cc: bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, Arnaldo Carvalho de Melo , Alexei Starovoitov , Yonghong Song , Krister Johansen , houtao1@huawei.com Subject: Re: [PATCH bpf-next] perf/bpf: Use prog to emit ksymbol event for main program Message-ID: References: <20240714065533.1112616-1-houtao@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240714065533.1112616-1-houtao@huaweicloud.com> On Sun, Jul 14, 2024 at 02:55:33PM +0800, Hou Tao wrote: > From: Hou Tao > > Since commit 0108a4e9f358 ("bpf: ensure main program has an extable"), > prog->aux->func[0]->kallsyms is left as uninitialized. For bpf program > with subprogs, the symbol for the main program is missed just as shown > in the output of perf script below: > > ffffffff81284b69 qp_trie_lookup_elem+0xb9 ([kernel.kallsyms]) > ffffffffc0011125 bpf_prog_a4a0eb0651e6af8b_lookup_qp_trie+0x5d (bpf...) > ffffffff8127bc2b bpf_for_each_array_elem+0x7b ([kernel.kallsyms]) > ffffffffc00110a1 +0x25 () > ffffffff8121a89a trace_call_bpf+0xca ([kernel.kallsyms]) > > Fix it by always using prog instead prog->aux->func[0] to emit ksymbol > event for the main program. After the fix, the output of perf script > will be correct: > > ffffffff81284b96 qp_trie_lookup_elem+0xe6 ([kernel.kallsyms]) > ffffffffc001382d bpf_prog_a4a0eb0651e6af8b_lookup_qp_trie+0x5d (bpf...) > ffffffff8127bc2b bpf_for_each_array_elem+0x7b ([kernel.kallsyms]) > ffffffffc0013779 bpf_prog_245c55ab25cfcf40_qp_trie_lookup+0x25 (bpf...) > ffffffff8121a89a trace_call_bpf+0xca ([kernel.kallsyms]) > > Fixes: 0108a4e9f358 ("bpf: ensure main program has an extable") > Signed-off-by: Hou Tao > --- > Hi, > > ksymbol for bpf program had been broken twice, and I think it is better > to add a bpf selftest for it, but I'm not so familiar with the > perf_event_open(), for now I just post the fix patch and will post the > selftest later. good idea, lgtm Reviewed-by: Jiri Olsa jirka > > kernel/events/core.c | 28 +++++++++++++--------------- > 1 file changed, 13 insertions(+), 15 deletions(-) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index f0128c5ff278..e1b7d9e61fa0 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -9289,21 +9289,19 @@ static void perf_event_bpf_emit_ksymbols(struct bpf_prog *prog, > bool unregister = type == PERF_BPF_EVENT_PROG_UNLOAD; > int i; > > - if (prog->aux->func_cnt == 0) { > - perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, > - (u64)(unsigned long)prog->bpf_func, > - prog->jited_len, unregister, > - prog->aux->ksym.name); > - } else { > - for (i = 0; i < prog->aux->func_cnt; i++) { > - struct bpf_prog *subprog = prog->aux->func[i]; > - > - perf_event_ksymbol( > - PERF_RECORD_KSYMBOL_TYPE_BPF, > - (u64)(unsigned long)subprog->bpf_func, > - subprog->jited_len, unregister, > - subprog->aux->ksym.name); > - } > + perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, > + (u64)(unsigned long)prog->bpf_func, > + prog->jited_len, unregister, > + prog->aux->ksym.name); > + > + for (i = 1; i < prog->aux->func_cnt; i++) { > + struct bpf_prog *subprog = prog->aux->func[i]; > + > + perf_event_ksymbol( > + PERF_RECORD_KSYMBOL_TYPE_BPF, > + (u64)(unsigned long)subprog->bpf_func, > + subprog->jited_len, unregister, > + subprog->aux->ksym.name); > } > } > > -- > 2.29.2 >