From patchwork Wed Jul 5 09:12:08 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jackie Liu X-Patchwork-Id: 13301857 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 B7D1D46B6 for ; Wed, 5 Jul 2023 09:12:24 +0000 (UTC) Received: from out-23.mta0.migadu.com (out-23.mta0.migadu.com [IPv6:2001:41d0:1004:224b::17]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0D85A170E for ; Wed, 5 Jul 2023 02:12:21 -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=1688548340; 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=Ufq9RzXxwvkSuKi7zraiaJAvAmobsbgeIKzzPJTEdv0=; b=BUN4cM0bSwBl2vTdrdXclQ1PZe92RbbElbuINvIZXFI2MC4/EoqBjkX7CePy48YF4Efzq7 Jp2GeSVgguAS8uq6Sk7QrgwGO/5pR5WeKZv5AQC3FOW59SgoFiwXeJFPEhmvcSZvEuLHma 7Ug5a3gpcsq22m23mJMGf9bjPkoFfO8= 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, daniel@iogearbox.net Subject: [PATCH v7 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms Date: Wed, 5 Jul 2023 17:12:08 +0800 Message-Id: <20230705091209.3803873-1-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 --- v6->v7: fix leak "FILE *f" v5->v6: fix crash by not init "const char *syms" v4->v5: simplified code tools/lib/bpf/libbpf.c | 107 +++++++++++++++++++++++++++++++++++++---- 1 file changed, 97 insertions(+), 10 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 214f828ece6b..af7e224ba4ca 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 +10576,79 @@ 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 = NULL; + 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; + } + /* not found entry, return direct */ + if (!cnt) { + fclose(f); + 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); + + fclose(f); + return err; +} + struct bpf_link * bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, const char *pattern, @@ -10594,13 +10685,9 @@ 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; }