From patchwork Thu Apr 15 12:13:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yordan Karadzhov X-Patchwork-Id: 12205297 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0BDF2C433B4 for ; Thu, 15 Apr 2021 12:13:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE202613B6 for ; Thu, 15 Apr 2021 12:13:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232770AbhDOMNt (ORCPT ); Thu, 15 Apr 2021 08:13:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232767AbhDOMNt (ORCPT ); Thu, 15 Apr 2021 08:13:49 -0400 Received: from mail-ej1-x62e.google.com (mail-ej1-x62e.google.com [IPv6:2a00:1450:4864:20::62e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8450C061756 for ; Thu, 15 Apr 2021 05:13:24 -0700 (PDT) Received: by mail-ej1-x62e.google.com with SMTP id w3so36552824ejc.4 for ; Thu, 15 Apr 2021 05:13:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Ir2uoBhaBlCM9nU/EcKA4NdYTmn8iA9rSHmkquNWHJk=; b=p0/u8FEOlUOgrGpWUINq8kXPKba51kprMW6OkzJXgL2ppOyFQBkGrF+i4ZbID8g36L zGy+2pAhDt0Pu5yZ6rFZUv3YyFkCqUgE2A+K85dRXkHiyRQ3ux/AoQOXRM4TohtHl4Ev /O3CN6jx5gIj9mtiK1guS07+zc6nhdwCkJRmbvOEsG7/mSTeIv8GP/FybZaA8yq48oyM z07odcdH0b9Djfv8c2dkA3iMHOFaflnrNW+DWysqwUCz0toumH5ZcMya+h9dvBoD+Rnw njeoU/vEI2/nnysaOOMVKqYRpNCETg/2tQz1BvnGiagVe/0jCoFLS1dbPVf+Tr+XyP9t oRgA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Ir2uoBhaBlCM9nU/EcKA4NdYTmn8iA9rSHmkquNWHJk=; b=bOEYc/5BR/gpp2jgYFwrvFT6Dz9TW/gWzJ3peoi/aoDCMag2JjZaKfJMjYC6ifH6Kn WpM8x9bIkt4ken+L2kgIKTFhkOVheH/YMNiTH92QCEOYSAESdzHb7Hzrs0eYenX20BVq xEzfaJHzfQB4nDkA9leUkG0Yxzlzquxudiasj/3QCXjcV4EjCy0vl0jc2rXgsdyexu4z JBT8SpDico4RFM0dySVFGIfrRYNiyVQzEEvk4ZddoDXQeVewQFZNuKD5ePNfeOUdaBz6 uJ7wPWzzkHHqQ1FBRL/94NyWrq5MafcOUzTQXfWvcTOWCnG75YGLHIKGRrWwuyBUcHfB Eh9Q== X-Gm-Message-State: AOAM533I0JSd2nVpfHYJdAW0SGKjl51L//WRxWD0hAN8YWWrO4cKqxVR 7d0mlSivoKbUGuncND44eD0= X-Google-Smtp-Source: ABdhPJxic/diuunNSNyKyU4QcYLY/LYHU3swalOoYPUbO6C8k9NccMJksIysMvuIrbVNIZmP8u6OGw== X-Received: by 2002:a17:906:e949:: with SMTP id jw9mr3197290ejb.433.1618488803551; Thu, 15 Apr 2021 05:13:23 -0700 (PDT) Received: from localhost.localdomain ([84.40.93.55]) by smtp.gmail.com with ESMTPSA id o20sm2364863eds.65.2021.04.15.05.13.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Apr 2021 05:13:23 -0700 (PDT) From: "Yordan Karadzhov (VMware)" To: rostedt@goodmis.org Cc: tz.stoyanov@gmail.com, linux-trace-devel@vger.kernel.org, "Yordan Karadzhov (VMware)" Subject: [PATCH 1/3] libtracefs: Add more methods for writing to files Date: Thu, 15 Apr 2021 15:13:09 +0300 Message-Id: <20210415121311.59787-2-y.karadz@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210415121311.59787-1-y.karadz@gmail.com> References: <20210415121311.59787-1-y.karadz@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org For the moment the library provides only one method for writing to tracefs files, that is: int tracefs_instance_file_write() This method first truncates the size of the file to 0 (clearing it), then writes new content to this file. Essentially this method overwrites (clear + write). In this patch we add two additional methids: int tracefs_instance_file_append() which writes without clearing and int tracefs_instance_file_clear() which clears without writing anything. Those two new APIs have various use-cases. For example one can use the two methods when adding/clearing kprobes. Signed-off-by: Yordan Karadzhov (VMware) --- include/tracefs.h | 4 +++ src/tracefs-instance.c | 74 +++++++++++++++++++++++++++++++++--------- 2 files changed, 63 insertions(+), 15 deletions(-) diff --git a/include/tracefs.h b/include/tracefs.h index 55ee867..551c37c 100644 --- a/include/tracefs.h +++ b/include/tracefs.h @@ -33,6 +33,10 @@ tracefs_instance_get_file(struct tracefs_instance *instance, const char *file); char *tracefs_instance_get_dir(struct tracefs_instance *instance); int tracefs_instance_file_write(struct tracefs_instance *instance, const char *file, const char *str); +int tracefs_instance_file_append(struct tracefs_instance *instance, + const char *file, const char *str); +int tracefs_instance_file_clear(struct tracefs_instance *instance, + const char *file); char *tracefs_instance_file_read(struct tracefs_instance *instance, const char *file, int *psize); int tracefs_instance_file_read_number(struct tracefs_instance *instance, diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c index b8ce36f..2aeb529 100644 --- a/src/tracefs-instance.c +++ b/src/tracefs-instance.c @@ -337,21 +337,41 @@ const char *tracefs_instance_get_trace_dir(struct tracefs_instance *instance) return NULL; } -static int write_file(const char *file, const char *str) +static int write_file(const char *file, const char *str, int flags) { - int ret; + int ret = 0; int fd; - fd = open(file, O_WRONLY | O_TRUNC); + fd = open(file, flags); if (fd < 0) { tracefs_warning("Failed to open '%s'", file); return -1; } - ret = write(fd, str, strlen(str)); + + if (str) + ret = write(fd, str, strlen(str)); + close(fd); return ret; } +static int instance_file_write(struct tracefs_instance *instance, + const char *file, const char *str, int flags) +{ + struct stat st; + char *path; + int ret; + + path = tracefs_instance_get_file(instance, file); + if (!path) + return -1; + ret = stat(path, &st); + if (ret == 0) + ret = write_file(path, str, flags); + tracefs_put_tracing_file(path); + + return ret; +} /** * tracefs_instance_file_write - Write in trace file of specific instance. @@ -364,19 +384,43 @@ static int write_file(const char *file, const char *str) int tracefs_instance_file_write(struct tracefs_instance *instance, const char *file, const char *str) { - struct stat st; - char *path; - int ret; + return instance_file_write(instance, file, str, O_WRONLY | O_TRUNC); +} - path = tracefs_instance_get_file(instance, file); - if (!path) - return -1; - ret = stat(path, &st); - if (ret == 0) - ret = write_file(path, str); - tracefs_put_tracing_file(path); +/** + * tracefs_instance_file_append - Append to a trace file of specific instance. + * @instance: ftrace instance, can be NULL for the top instance. + * @file: name of the file. + * @str: nul terminated string, that will be appended to the file. + * + * Returns the number of appended bytes, or -1 in case of an error. + */ +int tracefs_instance_file_append(struct tracefs_instance *instance, + const char *file, const char *str) +{ + return instance_file_write(instance, file, str, O_WRONLY); +} - return ret; +/** + * tracefs_instance_file_clear - Clear a trace file of specific instance. + * Note, it only opens with O_TRUNC and closes the file. If the file has + * content that does not get cleared in this way, this will not have any + * effect. For example, set_ftrace_filter can have probes that are not + * cleared by O_TRUNC: + * + * echo "schedule:stacktrace" > set_ftrace_filter + * + * This function will not clear the above "set_ftrace_filter" after that + * command. + * @instance: ftrace instance, can be NULL for the top instance. + * @file: name of the file to clear. + * + * Returns 0 on success, or -1 in case of an error. + */ +int tracefs_instance_file_clear(struct tracefs_instance *instance, + const char *file) +{ + return instance_file_write(instance, file, NULL, O_WRONLY | O_TRUNC); } /** From patchwork Thu Apr 15 12:13:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yordan Karadzhov X-Patchwork-Id: 12205299 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNWANTED_LANGUAGE_BODY, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6EE28C43460 for ; Thu, 15 Apr 2021 12:13:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 36F346137D for ; Thu, 15 Apr 2021 12:13:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232768AbhDOMNt (ORCPT ); Thu, 15 Apr 2021 08:13:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232642AbhDOMNs (ORCPT ); Thu, 15 Apr 2021 08:13:48 -0400 Received: from mail-ej1-x632.google.com (mail-ej1-x632.google.com [IPv6:2a00:1450:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A4A4FC06175F for ; Thu, 15 Apr 2021 05:13:25 -0700 (PDT) Received: by mail-ej1-x632.google.com with SMTP id v6so35227678ejo.6 for ; Thu, 15 Apr 2021 05:13:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=qBbh6sDrJSeW7ta6BZDPWAj+z1sWBTzbJs5rZJ8nB8o=; b=kd9EDVp8ugZJ6oyIXfnexpih4KXpt2XWSl8fqpdJvWTetNscXjBiDVLy3zUNL9RSPa 3ybo2e/cTVFjzaCbHn/cuYr2hazmjCWTLNn+0qVz0Jb8qt22kVnTJHttLhkWP1TeGKGW kYgpS2Z49EiK+2ycxa0pcs6/QfBFe8FQ8NHjQenIZQfYWoneek61h8vswamAmKr4DyLp V4JyRaBr1Ze9dRy4JSz+NM5bfuPVKqc6DXkCB9w9iti+qP6VeRZInFX5/+sme6FnMxCf 8Y7mhVmsBEwMZ87tDO5ltHGhe5w3Ha4UCK0Tfmj7SVP27G00T32ETPFPQr1SHqAA53mp ZjqQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=qBbh6sDrJSeW7ta6BZDPWAj+z1sWBTzbJs5rZJ8nB8o=; b=mApNnoZLowP4QifZwnz07I3WtNk/VT0+2AQP6IOMYV7Tj9MpSsRzsNm78aPVkO67Wi MLYwwcCOnhVV1FXXVh3YEqcNrySYuCCbSlmo7Gla4cnXQu791h7bssuX+3Y4VbC2DhqH Hym/vfyIuTm1NfmsnxbHY6LD1AH0VvxuUN1RR2ItCQk+FGgj97gXiDxvo1YLddL9uxFB L6TaB+7uAfImD863PDnLhb5sB4LbDsCFg4Gah4i96eX+5CPDpdILe09nUHFmsezw7tKH wzbYh8DUxqbtb/twPyfWlwerGUqmBQFhs0AooBg5Ch/SEA0EVNq0LB5faIV/X2R57Pim FGAw== X-Gm-Message-State: AOAM533Yxf1vOZ+Dha5r5EnQL6fzCGndg2YwOpHqmIi4BdspzKsfzKQo vcas+TSZdZDaQ7VA3m/e6ss6xpRSUos= X-Google-Smtp-Source: ABdhPJyY0jiah5bY+fe/XNOS08HIp/CdlJNbOC8h0eHTUGvWjf1USSEHzTtWSvrekaErr5k+Gg1Zzg== X-Received: by 2002:a17:906:804b:: with SMTP id x11mr3199479ejw.388.1618488804441; Thu, 15 Apr 2021 05:13:24 -0700 (PDT) Received: from localhost.localdomain ([84.40.93.55]) by smtp.gmail.com with ESMTPSA id o20sm2364863eds.65.2021.04.15.05.13.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Apr 2021 05:13:24 -0700 (PDT) From: "Yordan Karadzhov (VMware)" To: rostedt@goodmis.org Cc: tz.stoyanov@gmail.com, linux-trace-devel@vger.kernel.org, "Yordan Karadzhov (VMware)" Subject: [PATCH 2/3] libtracefs: Add tests for the new methods for writing Date: Thu, 15 Apr 2021 15:13:10 +0300 Message-Id: <20210415121311.59787-3-y.karadz@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210415121311.59787-1-y.karadz@gmail.com> References: <20210415121311.59787-1-y.karadz@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org We add testing for "int tracefs_instance_file_append()" and "int tracefs_instance_file_clear()". The test case performs registration and deregistration of kprobes. Signed-off-by: Yordan Karadzhov (VMware) --- utest/tracefs-utest.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/utest/tracefs-utest.c b/utest/tracefs-utest.c index d675c16..edb3a3d 100644 --- a/utest/tracefs-utest.c +++ b/utest/tracefs-utest.c @@ -28,6 +28,11 @@ #define TRACE_ON "tracing_on" #define TRACE_CLOCK "trace_clock" +#define KPROB_EVTS "kprobe_events" +#define KPROBE_1 "p:mkdir do_mkdirat path=+u0($arg2):ustring" +#define KPROBE_1_RM "-:mkdir" +#define KPROBE_2 "p:open do_sys_openat2 file=+u0($arg2):ustring flags=+0($arg3):x64" + static struct tracefs_instance *test_instance; static struct tep_handle *test_tep; struct test_sample { @@ -375,6 +380,7 @@ static void test_instance_file(void) char *inst_file; char *inst_dir; struct stat st; + char *kprobes; char *fname; char *file1; char *file2; @@ -443,6 +449,32 @@ static void test_instance_file(void) free(file1); free(file2); + ret = tracefs_instance_file_write(NULL, KPROB_EVTS, KPROBE_1); + CU_TEST(ret == strlen(KPROBE_1)); + kprobes = tracefs_instance_file_read(NULL, KPROB_EVTS, &size); + CU_TEST(kprobes != NULL); + CU_TEST(strstr(kprobes, KPROBE_1 + 2) != NULL); + free(kprobes); + + ret = tracefs_instance_file_append(NULL, KPROB_EVTS, KPROBE_2); + CU_TEST(ret == strlen(KPROBE_2)); + kprobes = tracefs_instance_file_read(NULL, KPROB_EVTS, &size); + CU_TEST(kprobes != NULL); + CU_TEST(strstr(kprobes, KPROBE_2 + 2) != NULL); + free(kprobes); + + ret = tracefs_instance_file_append(NULL, KPROB_EVTS, KPROBE_1_RM); + CU_TEST(ret == strlen(KPROBE_1_RM)); + kprobes = tracefs_instance_file_read(NULL, KPROB_EVTS, &size); + CU_TEST(kprobes != NULL); + CU_TEST(strstr(kprobes, KPROBE_1 + 2) == NULL); + free(kprobes); + + ret = tracefs_instance_file_clear(NULL, KPROB_EVTS); + CU_TEST(ret == 0); + kprobes = tracefs_instance_file_read(NULL, KPROB_EVTS, &size); + CU_TEST(kprobes == NULL); + tracefs_put_tracing_file(inst_file); free(fname); From patchwork Thu Apr 15 12:13:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yordan Karadzhov X-Patchwork-Id: 12205301 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-20.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9B13C43461 for ; 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Thu, 15 Apr 2021 05:13:25 -0700 (PDT) Received: from localhost.localdomain ([84.40.93.55]) by smtp.gmail.com with ESMTPSA id o20sm2364863eds.65.2021.04.15.05.13.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Apr 2021 05:13:24 -0700 (PDT) From: "Yordan Karadzhov (VMware)" To: rostedt@goodmis.org Cc: tz.stoyanov@gmail.com, linux-trace-devel@vger.kernel.org, "Yordan Karadzhov (VMware)" Subject: [PATCH 3/3] libtracefs: Document the new methods for writing to file. Date: Thu, 15 Apr 2021 15:13:11 +0300 Message-Id: <20210415121311.59787-4-y.karadz@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210415121311.59787-1-y.karadz@gmail.com> References: <20210415121311.59787-1-y.karadz@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Documentation for "int tracefs_instance_file_append()" and "int tracefs_instance_file_clear()" is being added. The file "Documentation/libtracefs-instances-files.txt" gets split, because when adding two more APIs we exceed the limit of APIs per file. Signed-off-by: Yordan Karadzhov (VMware) --- .../libtracefs-instances-file-manip.txt | 199 ++++++++++++++++++ Documentation/libtracefs-instances-files.txt | 35 +-- 2 files changed, 201 insertions(+), 33 deletions(-) create mode 100644 Documentation/libtracefs-instances-file-manip.txt diff --git a/Documentation/libtracefs-instances-file-manip.txt b/Documentation/libtracefs-instances-file-manip.txt new file mode 100644 index 0000000..942e7ad --- /dev/null +++ b/Documentation/libtracefs-instances-file-manip.txt @@ -0,0 +1,199 @@ +libtracefs(3) +============= + +NAME +---- + +tracefs_instance_file_open, +tracefs_instance_file_write, tracefs_instance_file_append, tracefs_instance_file_clear, +tracefs_instance_file_read, tracefs_instance_file_read_number - Work with files in tracing instances. + +SYNOPSIS +-------- +[verse] +-- +*#include * + +int *tracefs_instance_file_open*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, int _mode_); +int *tracefs_instance_file_write*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, const char pass:[*]_str_); +int *tracefs_instance_file_append*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, const char pass:[*]_str_); +int *tracefs_instance_file_clear*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_); +char pass:[*]*tracefs_instance_file_read*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, int pass:[*]_psize_); +int *tracefs_instance_file_read_number*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, long long int pass:[*]_res_); + +-- + +DESCRIPTION +----------- +This set of APIs can be used to work with trace files in all trace instances. +Each of these APIs take an _instance_ argument, that can be NULL to act +on the top level instance. Otherwise, it acts on an instance created with +*tracefs_insance_create*(3) + +The _tracefs_instance_file_open()_ function opens trace _file_ from given _instance_ and returns +a file descriptor to it. The file access _mode_ can be specified, see *open*(3) for more details. +If -1 is passed as _mode_, default O_RDWR is used. + +The _tracefs_instance_file_write()_ function writes a string _str_ in a _file_ from +the given _instance_, without the terminating NULL character. When opening the file, this function +tries to truncates the size of the file to zero, which clears all previously existing settings. + +The _tracefs_instance_file_append()_ function writes a string _str_ in a _file_ from +the given _instance_, without the terminating NULL character. This function is similar to +_tracefs_instance_file_write()_, but the existing content of the is not cleared. Thus the +new settings are appended to the existing ones (if any). + +The _tracefs_instance_file_clear()_ function tries to truncates the size of the file to zero, +which clears all previously existing settings. If the file has content that does not get +cleared in this way, this will not have any effect. + +The _tracefs_instance_file_read()_ function reads the content of a _file_ from +the given _instance_. + +The _tracefs_instance_file_read_number()_ function reads the content of a _file_ from +the given _instance_ and converts it to a long long integer, which is stored in _res_. + +RETURN VALUE +------------ +The _tracefs_instance_file_open()_ function returns a file descriptor to the opened file. It must be +closed with *close*(3). In case of an error, -1 is returned. + +The _tracefs_instance_file_write()_ function returns the number of written bytes, +or -1 in case of an error. + +The _tracefs_instance_file_append()_ function returns the number of written bytes, +or -1 in case of an error. + +The _tracefs_instance_file_clear()_ function returns 0 on success, or -1 in case of an error. + +The _tracefs_instance_file_read()_ function returns a pointer to a NULL terminated +string, read from the file, or NULL in case of an error. The returned string must +be freed with free(). + +The _tracefs_instance_file_read_number()_ function returns 0 if a valid integer is read from +the file and stored in _res_ or -1 in case of an error. + +EXAMPLE +------- +[source,c] +-- +#include + +struct tracefs_instance *inst = tracefs_instance_create("foo"); + if (!inst) { + /* Error creating a new trace instance */ + ... + } + + if (tracefs_file_exists(inst,"trace_clock")) { + /* The instance foo supports trace clock */ + char *path, *clock; + int size; + + path = = tracefs_instance_get_file(inst, "trace_clock") + if (!path) { + /* Error getting the path to trace_clock file in instance foo */ + ... + } + ... + tracefs_put_tracing_file(path); + + clock = tracefs_instance_file_read(inst, "trace_clock", &size); + if (!clock) { + /* Failed to read trace_clock file in instance foo */ + ... + } + ... + free(clock); + + if (tracefs_instance_file_write(inst, "trace_clock", "global") != strlen("global")) { + /* Failed to set gloabl trace clock in instance foo */ + ... + } + } else { + /* The instance foo does not support trace clock */ + } + + if (tracefs_dir_exists(inst,"options")) { + /* The instance foo supports trace options */ + char *path = tracefs_instance_get_file(inst, "options"); + if (!path) { + /* Error getting the path to options directory in instance foo */ + ... + } + + tracefs_put_tracing_file(path); + } else { + /* The instance foo does not support trace options */ + } + + ... + + if (tracefs_instance_is_new(inst)) + tracefs_instance_destroy(inst); + else + tracefs_instance_free(inst); + ... + + long long int res; + if (tracefs_instance_file_read_number(NULL, "tracing_on", &res) == 0) { + if (res == 0) { + /* tracing is disabled in the top instance */ + } else if (res == 1) { + /* tracing is enabled in the top instance */ + } else { + /* Unknown tracing state of the top instance */ + } + } else { + /* Failed to read integer from tracing_on file */ + } + + ... + + int fd; + fd = tracefs_instance_file_open(NULL, "tracing_on", O_WRONLY); + if (fd >= 0) { + /* Got file descriptor to the tracing_on file from the top instance for writing */ + ... + close(fd); + } +-- +FILES +----- +[verse] +-- +*tracefs.h* + Header file to include in order to have access to the library APIs. +*-ltracefs* + Linker switch to add when building a program that uses the library. +-- + +SEE ALSO +-------- +_libtracefs(3)_, +_libtraceevent(3)_, +_trace-cmd(1)_ + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* +*Tzvetomir Stoyanov* +-- +REPORTING BUGS +-------------- +Report bugs to + +LICENSE +------- +libtracefs is Free Software licensed under the GNU LGPL 2.1 + +RESOURCES +--------- +https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/ + +COPYING +------- +Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under +the terms of the GNU Public License (GPL). diff --git a/Documentation/libtracefs-instances-files.txt b/Documentation/libtracefs-instances-files.txt index 124ef52..4ac87d1 100644 --- a/Documentation/libtracefs-instances-files.txt +++ b/Documentation/libtracefs-instances-files.txt @@ -3,9 +3,8 @@ libtracefs(3) NAME ---- -tracefs_file_exists, tracefs_dir_exists, tracefs_instance_get_file, -tracefs_instance_get_dir, tracefs_instance_file_open, tracefs_instance_file_write, -tracefs_instance_file_read, tracefs_instance_file_read_number - Work with files in tracing instances. +tracefs_file_exists, tracefs_dir_exists, +tracefs_instance_get_file, tracefs_instance_get_dir - Work with files directories in tracing instances. SYNOPSIS -------- @@ -17,10 +16,6 @@ bool *tracefs_file_exists*(struct tracefs_instance pass:[*]_instance_, char pass bool *tracefs_dir_exists*(struct tracefs_instance pass:[*]_instance_, char pass:[*]_name_); char pass:[*]*tracefs_instance_get_file*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_); char pass:[*]*tracefs_instance_get_dir*(struct tracefs_instance pass:[*]_instance_); -int *tracefs_instance_file_open*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, int _mode_); -int *tracefs_instance_file_write*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, const char pass:[*]_str_); -char pass:[*]*tracefs_instance_file_read*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, int pass:[*]_psize_); -int *tracefs_instance_file_read_number*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_file_, long long int pass:[*]_res_); -- @@ -43,19 +38,6 @@ The _tracefs_instance_get_dir()_ function returns the full path of the director with given _name_ in _instance_. Note, it does not check if the directory exists in the instance. -The _tracefs_instance_file_open()_ function opens trace _file_ from given _instance_ and returns -a file descriptor to it. The file access _mode_ can be specified, see *open*(3) for more details. -If -1 is passed as _mode_, default O_RDWR is used. - -The _tracefs_instance_file_write()_ function writes a string _str_ in a _file_ from -the given _instance_, without the terminating NULL character. - -The _tracefs_instance_file_read()_ function reads the content of a _file_ from -the given _instance_. - -The _tracefs_instance_file_read_number()_ function reads the content of a _file_ from -the given _instance_ and converts it to a long long integer, which is stored in _res_. - RETURN VALUE ------------ The _tracefs_file_exists()_ and _tracefs_dir_exists()_ functions return true if the @@ -65,19 +47,6 @@ The _tracefs_instance_get_file()_ and _tracefs_instance_get_dir()_ functions ret a string or NULL in case of an error. The returned string must be freed with _tracefs_put_tracing_file()_. -The _tracefs_instance_file_open()_ function returns a file descriptor to the opened file. It must be -closed with *close*(3). In case of an error, -1 is returned. - -The _tracefs_instance_file_write()_ function returns the number of written bytes, -or -1 in case of an error. - -The _tracefs_instance_file_read()_ function returns a pointer to a NULL terminated -string, read from the file, or NULL in case of an error. The returned string must -be freed with free(). - -The _tracefs_instance_file_read_number()_ function returns 0 if a valid integer is read from -the file and stored in _res_ or -1 in case of an error. - EXAMPLE ------- [source,c]