From patchwork Wed Jul 5 03:29:07 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jackie Liu X-Patchwork-Id: 13301626 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5C22AA3D for ; Wed, 5 Jul 2023 03:29:24 +0000 (UTC) Received: from out-4.mta1.migadu.com (out-4.mta1.migadu.com [95.215.58.4]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0BEAC10D5 for ; Tue, 4 Jul 2023 20:29:20 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1688527757; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=XbzVyXf8fgu/ccXkS56oriFPHxIUJg3jUWsomKaoolM=; b=EBIMYz64U0x8h7fGMyAiAHQsRWp5qT6qSp5ANRWh+nJHNg7zgBVOUsS1y5lVtaao/jIG6i NQuSSqIK7VxPn9yUUdU4WtjISDZ5G65BzZDTQnnHdQdQZ7+AqXzfYC/h6V6o70rnI+1ioa g1T71ZFdmifQDiduaVYBEPvTJtJ/Lrg= From: Jackie Liu To: olsajiri@gmail.com, andrii@kernel.org Cc: martin.lau@linux.dev, song@kernel.org, yhs@fb.com, bpf@vger.kernel.org, liuyun01@kylinos.cn Subject: [PATCH v5 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms Date: Wed, 5 Jul 2023 11:29:07 +0800 Message-Id: <20230705032908.3778010-1-liu.yun@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net From: Jackie Liu When using regular expression matching with "kprobe multi", it scans all the functions under "/proc/kallsyms" that can be matched. However, not all of them can be traced by kprobe.multi. If any one of the functions fails to be traced, it will result in the failure of all functions. The best approach is to filter out the functions that cannot be traced to ensure proper tracking of the functions. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202307030355.TdXOHklM-lkp@intel.com/ Suggested-by: Jiri Olsa Suggested-by: Andrii Nakryiko Signed-off-by: Jackie Liu --- v4->v5: simplified code tools/lib/bpf/libbpf.c | 106 +++++++++++++++++++++++++++++++++++++---- 1 file changed, 96 insertions(+), 10 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 214f828ece6b..327b4a9e9f0d 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -10224,6 +10224,12 @@ static const char *tracefs_uprobe_events(void) return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events"; } +static const char *tracefs_available_filter_functions(void) +{ + return use_debugfs() ? DEBUGFS"/available_filter_functions" : + TRACEFS"/available_filter_functions"; +} + static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, const char *kfunc_name, size_t offset) { @@ -10539,14 +10545,26 @@ struct kprobe_multi_resolve { size_t cnt; }; -static int -resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type, - const char *sym_name, void *ctx) +static int avail_compare_function(const void *a, const void *b) +{ + return strcmp(*(const char **)a, *(const char **)b); +} + +struct avail_kallsyms_data { + const char **syms; + size_t cnt; + struct kprobe_multi_resolve *res; +}; + +static int avail_kallsyms_cb(unsigned long long sym_addr, char sym_type, + const char *sym_name, void *ctx) { - struct kprobe_multi_resolve *res = ctx; + struct avail_kallsyms_data *data = ctx; + struct kprobe_multi_resolve *res = data->res; int err; - if (!glob_match(sym_name, res->pattern)) + if (!bsearch(&sym_name, data->syms, data->cnt, sizeof(void *), + avail_compare_function)) return 0; err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long), @@ -10558,6 +10576,78 @@ resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type, return 0; } +static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res) +{ + struct avail_kallsyms_data data; + char sym_name[500]; + const char *available_functions_file = tracefs_available_filter_functions(); + FILE *f; + int err = 0, ret, i; + const char **syms; + size_t cap = 0, cnt = 0; + + f = fopen(available_functions_file, "r"); + if (!f) { + err = -errno; + pr_warn("failed to open %s\n", available_functions_file); + return err; + } + + while (true) { + char *name; + + ret = fscanf(f, "%499s%*[^\n]\n", sym_name); + if (ret == EOF && feof(f)) + break; + + if (ret != 1) { + pr_warn("failed to read available function file entry: %d\n", + ret); + err = -EINVAL; + goto cleanup; + } + + if (!glob_match(sym_name, res->pattern)) + continue; + + err = libbpf_ensure_mem((void **)&syms, &cap, sizeof(void *), + cnt + 1); + if (err) + goto cleanup; + + name = strdup(sym_name); + if (!name) { + err = -errno; + goto cleanup; + } + + syms[cnt++] = name; + } + fclose(f); + + /* not found entry, return direct */ + if (!cnt) + return -ENOENT; + + /* sort available functions */ + qsort(syms, cnt, sizeof(void *), avail_compare_function); + + data.syms = syms; + data.res = res; + data.cnt = cnt; + libbpf_kallsyms_parse(avail_kallsyms_cb, &data); + + if (!res->cnt) + err = -ENOENT; + +cleanup: + for (i = 0; i < cnt; i++) + free((char *)syms[i]); + free(syms); + + return err; +} + struct bpf_link * bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, const char *pattern, @@ -10594,13 +10684,9 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, return libbpf_err_ptr(-EINVAL); if (pattern) { - err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res); + err = libbpf_available_kallsyms_parse(&res); if (err) goto error; - if (!res.cnt) { - err = -ENOENT; - goto error; - } addrs = res.addrs; cnt = res.cnt; }