From mboxrd@z Thu Jan 1 00:00:00 1970 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 933E2DDBE for ; Mon, 3 Jul 2023 13:00:00 +0000 (UTC) Received: from mail-ed1-x52e.google.com (mail-ed1-x52e.google.com [IPv6:2a00:1450:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0144DD for ; Mon, 3 Jul 2023 05:59:58 -0700 (PDT) Received: by mail-ed1-x52e.google.com with SMTP id 4fb4d7f45d1cf-51de841a727so4495168a12.3 for ; Mon, 03 Jul 2023 05:59:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1688389197; x=1690981197; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=5cZnewjmf7DrJMc5X556bVwXHRxytKI1jw53LG2FMW8=; b=Nx080V3m4hq+yTaxZ/ERiRZsDTDQqX8UkibK72STYxhuJWLJRHYxIhNs7erKYtVxPz /ME2j0x4CzvMUSaA+3fosciuSdEKd/D7c1WNH8YnLMpmaqIwBzcp9v4Bm5yyGtbjS8QY La7JIlMd7A6Z+e6mYecdJogTfRQJu8cZ7L/SHjQr8rCERy/8AaloCDG8fxAu/CgDYYuN gB+bHYX2UAtGA02HeE+kwjjmcT5U4eCR8HJx4Ya2Z4KNnfAEWm4b035gzX5FPsd4kPVS DP93QQDqXVMHXR5XBHkwmj6bdm+OhY0D8fsHdX5+VCHLjJWFfFrb/hfM1n/sHnI5EJHe C79A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688389197; x=1690981197; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=5cZnewjmf7DrJMc5X556bVwXHRxytKI1jw53LG2FMW8=; b=URiYSBS7X8hk6kvjovAJYeR/UqfprUy3G2BTF8XYSGr83VxmhlQuLd7TXbRHAqUnJf K7Qm8O3OY28YBsJDL15Gab0TWH0HZj9/RO5KdwpNygvoZe3bk2GVzPYfkn5hoDg6bCBp sswBUw+EyXMm/hI9/aywB0JsggEC9/Ii6jl4k9Oe1oosLaQruZ7ow6vCDUkkmv9AoIMh iat5m9hCKNI6SHuu2/o01yFUtoFuQHjhBNVF8wpSACW5ZCLg2GdKKDoj4gJ4gwsP1NQc 0Vp3n8822ogt3QJlEDziVZj5Gh87p03yoa8+hOEamdV8V0DT+CFFdLCJEDqkqhrH/H1H RqyA== X-Gm-Message-State: ABy/qLaPuYBLCE1mLv81WS09RQD3cKm+2ry3tjMTdtlBUc3UnwfV12Sn zDvBlUCGJmLxy3dT5Ygv+AE= X-Google-Smtp-Source: APBJJlFG13wRltK0968hUgiYZuZ5bp5BnY0D3osSKcz0xQiXH4+WVZGTRdza2J7Xw/DS5MeUuhtOhg== X-Received: by 2002:a05:6402:328:b0:51d:b0f1:bed0 with SMTP id q8-20020a056402032800b0051db0f1bed0mr7291651edw.35.1688389196902; Mon, 03 Jul 2023 05:59:56 -0700 (PDT) Received: from krava ([193.46.31.82]) by smtp.gmail.com with ESMTPSA id d17-20020a056402001100b0051a53d7b160sm10417659edu.80.2023.07.03.05.59.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Jul 2023 05:59:56 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Mon, 3 Jul 2023 14:59:52 +0200 To: Jackie Liu Cc: olsajiri@gmail.com, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, bpf@vger.kernel.org, liuyun01@kylinos.cn, lkp@intel.com Subject: Re: [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms Message-ID: References: <20230703013618.1959621-1-liu.yun@linux.dev> Precedence: bulk X-Mailing-List: bpf@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: <20230703013618.1959621-1-liu.yun@linux.dev> X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Mon, Jul 03, 2023 at 09:36:17AM +0800, Jackie Liu wrote: > 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 > --- > v2->v3: fix 'fscanf' may overflow > > tools/lib/bpf/libbpf.c | 122 ++++++++++++++++++++++++++++++++++++----- > 1 file changed, 109 insertions(+), 13 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 214f828ece6b..232268215bb7 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) > { > @@ -10539,23 +10545,113 @@ 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 qsort_compare_function(const void *a, const void *b) > { > - struct kprobe_multi_resolve *res = ctx; > - int err; > + return strcmp(*(const char **)a, *(const char **)b); > +} > > - if (!glob_match(sym_name, res->pattern)) > - return 0; > +static int bsearch_compare_function(const void *a, const void *b) > +{ > + return strcmp((const char *)a, *(const char **)b); > +} > > - err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long), > - res->cnt + 1); > - if (err) > +static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res) > +{ > + char sym_name[500]; > + const char *available_functions_file = tracefs_available_filter_functions(); > + FILE *f; > + int err = 0, ret, i; > + struct function_info { > + const char **syms; > + size_t cap; > + size_t cnt; > + } infos = {}; do you need to define new struct for this? there's just on infos variable of that, you could use just: 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; > + } > > - res->addrs[res->cnt++] = (unsigned long) sym_addr; > - return 0; > + 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 **)&infos.syms, &infos.cap, > + sizeof(void *), infos.cnt + 1); > + if (err) > + goto cleanup; > + > + name = strdup(sym_name); > + if (!name) { > + err = -errno; > + goto cleanup; > + } > + > + infos.syms[infos.cnt++] = name; > + } > + fclose(f); should you check if you found anything (infos.cnt != 0) and return early if there's nothing found > + > + /* sort available functions */ > + qsort(infos.syms, infos.cnt, sizeof(void *), qsort_compare_function); > + > + f = fopen("/proc/kallsyms", "r"); why not use libbpf_kallsyms_parse for kallsyms parsing? the call below would be in its callback > + if (!f) { > + err = -errno; > + pr_warn("failed to open /proc/kallsyms\n"); > + goto free_infos; > + } > + > + while (true) { > + unsigned long long sym_addr; > + > + ret = fscanf(f, "%llx %*c %499s%*[^\n]\n", &sym_addr, sym_name); > + if (ret == EOF && feof(f)) > + break; > + > + if (ret != 2) { > + pr_warn("failed to read kallsyms entry: %d\n", ret); > + err = -EINVAL; > + break; > + } > + > + if (!glob_match(sym_name, res->pattern)) > + continue; hm, we don't need to call glob_match again, we just want to check if the kallsyms symbol is in infos.syms > + > + if (!bsearch(&sym_name, infos.syms, infos.cnt, sizeof(void *), > + bsearch_compare_function)) > + continue; > + > + err = libbpf_ensure_mem((void **)&res->addrs, &res->cap, > + sizeof(unsigned long), res->cnt + 1); > + if (err) > + break; > + > + res->addrs[res->cnt++] = (unsigned long) sym_addr; > + } res->cnt is check outside for 0, so we should be find here jirka > + > +cleanup: > + fclose(f); > +free_infos: > + for (i = 0; i < infos.cnt; i++) > + free((char *)infos.syms[i]); > + free(infos.syms); > + > + return err; > } > > struct bpf_link * > @@ -10594,7 +10690,7 @@ 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) { > -- > 2.25.1 >