From patchwork Wed Jun 23 12:05:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yordan Karadzhov X-Patchwork-Id: 12339741 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,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 79E92C4743C for ; Wed, 23 Jun 2021 12:05:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5AC516044F for ; Wed, 23 Jun 2021 12:05:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230130AbhFWMH4 (ORCPT ); Wed, 23 Jun 2021 08:07:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230019AbhFWMH4 (ORCPT ); Wed, 23 Jun 2021 08:07:56 -0400 Received: from mail-wm1-x333.google.com (mail-wm1-x333.google.com [IPv6:2a00:1450:4864:20::333]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53DBDC061574 for ; Wed, 23 Jun 2021 05:05:38 -0700 (PDT) Received: by mail-wm1-x333.google.com with SMTP id a5-20020a7bc1c50000b02901e3bbe0939bso1205659wmj.0 for ; Wed, 23 Jun 2021 05:05:38 -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:mime-version :content-transfer-encoding; bh=i2Meg6CX3aHC6i/LD4BJfxvungrOu3d87p8M2PfVM9g=; b=UORUrM1pehE6djIJ7uik5TDGotZ1+noo8kxTgabI9K/IFiehjHQWHat0uamEZl7knu xb0MwYzLe2vFcvonyPqmd1sBO2n1372EgZ7v3J8m2zCxKS9T9reHVKGln4NVvHxPVQqu 0bC2dWZyzb62Iiud0JlQKC/qBGJXo6fBfirFSpRulxZymoUa0SsxZM7P8OiKGjn8AaP8 TbEzoKQ3Be9gGKmCIRrYQmeQtyya29AjBTBKOGZRnW7VmKznuIV51XCjiPK74Gc+EzI1 kLcWnTjij4NGofpB9VWG3pn3A7sBjEB8tzMavqE/YcLC7nj09aE7F5me4LujaaX4002p YlQw== 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:mime-version :content-transfer-encoding; bh=i2Meg6CX3aHC6i/LD4BJfxvungrOu3d87p8M2PfVM9g=; b=Y8EfNK66rWQaIB8ZZlJ41xy9ynDAaV5ODBWc2xTxUn9z11HbzM5Yz37Cz9S9CW63Qq frdHfsFn2b8cwQdQxqV8bTOmVzObHvyok3IsUg5fCqnC5+Ud7AS+y4xmXySA6kt0Rr3m jMhPoCLqq3b3OxssFfOz8C8N1l48qleQpflmI+MOHKI+mS3FrD7ajsmqZqxDjZzaE2XA nGSBRML5MSQq50YxYtyRJPvj/23OyzN93UZG9yKaeNJ+ZK0z8JJtAxabCTvZPKFihY30 ZhIpTNnM3YiOuhz3EByUibLA8qC5h1BTnEaACvpoEcLxBwaBz6o3q4BDj5gV7C8VJY15 j8FQ== X-Gm-Message-State: AOAM533kmfuw3fZZa8iIJyXL2PR19RhmQMqMaCUfnQZ5ZTGxyABOC0pA ohfZP4zOvH1tee7+O6JtlWaPJSfRA+w= X-Google-Smtp-Source: ABdhPJyLyeW78LagsERGCQ6UJPM9+yTEvcMiHAxORDiHEpULh0w722qBOdjcpZnrsciPoJwSpFj82g== X-Received: by 2002:a1c:7903:: with SMTP id l3mr10069481wme.128.1624449936660; Wed, 23 Jun 2021 05:05:36 -0700 (PDT) Received: from crow.eng.vmware.com ([146.247.46.133]) by smtp.gmail.com with ESMTPSA id n13sm5584627wms.37.2021.06.23.05.05.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Jun 2021 05:05:36 -0700 (PDT) From: "Yordan Karadzhov (VMware)" To: linux-trace-devel@vger.kernel.org Cc: "Yordan Karadzhov (VMware)" Subject: [PATCH v2] libtracefs: Add APIs for data streaming Date: Wed, 23 Jun 2021 15:05:26 +0300 Message-Id: <20210623120526.36623-1-y.karadz@gmail.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org The new APIs can be used to dump the content of "trace_pipe" into a file or directly to "stdout". The "splice" system call is used to moves the data without copying. The new functionality is essentially identical to what 'trace-cmd show -p' does. Signed-off-by: Yordan Karadzhov (VMware) --- Changes in v2: - The setting of the signal disposition is removed from the library and is now responsibility of the caller. This in fact gives more options for the user. - The example provided in the documentation is updated accordingly. Documentation/libtracefs-stream.txt | 106 ++++++++++++++++++++++++++++ include/tracefs-local.h | 1 + include/tracefs.h | 5 ++ src/tracefs-tools.c | 98 +++++++++++++++++++++++++ 4 files changed, 210 insertions(+) create mode 100644 Documentation/libtracefs-stream.txt diff --git a/Documentation/libtracefs-stream.txt b/Documentation/libtracefs-stream.txt new file mode 100644 index 0000000..24c2e47 --- /dev/null +++ b/Documentation/libtracefs-stream.txt @@ -0,0 +1,106 @@ +libtracefs(3) +============= + +NAME +---- +tracefs_trace_pipe_stream, tracefs_trace_pipe_print - +redirect the stream of trace data to an output or stdout. + +SYNOPSIS +-------- +[verse] +-- +*#include * + +int tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, int flags); +int tracefs_trace_pipe_print(struct tracefs_instance *instance); + +-- + +DESCRIPTION +----------- +If NULL is passed as _instance_, the top trace instance is used. +The user can interrupt the streaming of the data by pressing Ctrl-c. + +The _tracefs_trace_pipe_stream()_ function redirects the stream of trace data to an output +file. The "splice" system call is used to moves the data without copying between kernel +address space and user address space. The _fd_ is the file descriptor of the output file +and _flags_ is a bit mask of flags to be passed to the "splice" system call. + +The _tracefs_trace_pipe_print()_ function is similar to _tracefs_trace_pipe_stream()_, but +the stream of trace data is redirected to stdout. + + +RETURN VALUE +------------ +The _tracefs_trace_pipe_stream()_, and _tracefs_trace_pipe_print()_ functions return 0 if the operation is +successful, or -1 in case of an error. + +EXAMPLE +------- +[source,c] +-- +#include +#include + +#include + +void stop(int sig) +{ + tracefs_trace_pipe_stop(NULL); +} + +int main() +{ + mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH; + const char *filename = "trace.txt"; + int fd = creat(filename, mode); + int ret; + + signal(SIGINT, stop); + ret = tracefs_trace_pipe_stream(fd, NULL, 0); + close(fd); + + return ret; +} +-- +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)_, +Documentation/trace/ftrace.rst from the Linux kernel tree + +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) 2021 VMware, Inc. Free use of this software is granted under +the terms of the GNU Public License (GPL). diff --git a/include/tracefs-local.h b/include/tracefs-local.h index 9e3aa18..833f136 100644 --- a/include/tracefs-local.h +++ b/include/tracefs-local.h @@ -30,6 +30,7 @@ struct tracefs_instance { int ftrace_notrace_fd; int ftrace_marker_fd; int ftrace_marker_raw_fd; + int pipe_keep_going; }; extern pthread_mutex_t toplevel_lock; diff --git a/include/tracefs.h b/include/tracefs.h index e29b550..3c6741b 100644 --- a/include/tracefs.h +++ b/include/tracefs.h @@ -184,4 +184,9 @@ int tracefs_function_notrace(struct tracefs_instance *instance, const char *filt /* Control library logs */ void tracefs_set_loglevel(enum tep_loglevel level); +int tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, int flags); +int tracefs_trace_pipe_print(struct tracefs_instance *instance); +void tracefs_trace_pipe_stop(struct tracefs_instance *instance); + + #endif /* _TRACE_FS_H */ diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c index 0cbb56d..0c0c44f 100644 --- a/src/tracefs-tools.c +++ b/src/tracefs-tools.c @@ -912,3 +912,101 @@ int tracefs_function_notrace(struct tracefs_instance *instance, const char *filt tracefs_put_tracing_file(filter_path); return ret; } + +static int top_pipe_keep_going; + +/** + * tracefs_trace_pipe_stream - redirect the stream of trace data to an output + * file. The "splice" system call is used to moves the data without copying + * between kernel address space and user address space. The user can interrupt + * the streaming of the data by pressing Ctrl-c. + * @fd: The file descriptor of the output file. + * @instance: ftrace instance, can be NULL for top tracing instance. + * @flags: flags to be passed to the "splice" system call. + * + * Returns -1 in case of an error or 0 otherwise. + */ +int tracefs_trace_pipe_stream(int fd, struct tracefs_instance *instance, + int flags) +{ + int *keep_going = instance ? &instance->pipe_keep_going : + &top_pipe_keep_going; + const char *file = "trace_pipe"; + int brass[2], in_fd, ret = -1; + off_t data_size; + + in_fd = tracefs_instance_file_open(instance, file, O_RDONLY); + if (in_fd < 0) { + tracefs_warning("Failed to open 'trace_pipe'."); + return ret; + } + + if(pipe(brass) < 0) { + tracefs_warning("Failed to open pipe."); + goto close_file; + } + + data_size = fcntl(brass[0], F_GETPIPE_SZ); + if (data_size <= 0) { + tracefs_warning("Failed to open pipe (size=0)."); + goto close_all; + } + + *keep_going = true; + while (*keep_going) { + ret = splice(in_fd, NULL, + brass[1], NULL, + data_size, flags); + if (ret < 0) + break; + + ret = splice(brass[0], NULL, + fd, NULL, + data_size, flags); + if (ret < 0) + break; + } + + /* + * Do not return error in the case when the "splice" system call + * was interrupted by the user (pressing Ctrl-c). + */ + if (!keep_going) + ret = 0; + + close_all: + close(brass[0]); + close(brass[1]); + close_file: + close(in_fd); + + return ret; +} + +/** + * tracefs_trace_pipe_print - redirect the stream of trace data to "stdout". + * The "splice" system call is used to moves the data without copying + * between kernel address space and user address space. + * @instance: ftrace instance, can be NULL for top tracing instance. + * + * Returns -1 in case of an error or 0 otherwise. + */ + +int tracefs_trace_pipe_print(struct tracefs_instance *instance) +{ + return tracefs_trace_pipe_stream(STDOUT_FILENO, + instance, + SPLICE_F_MORE | SPLICE_F_MOVE); +} + +/** + * tracefs_trace_pipe_stop - stop the streaming of trace data. + * @instance: ftrace instance, can be NULL for top tracing instance. + */ +void tracefs_trace_pipe_stop(struct tracefs_instance *instance) +{ + if (instance) + instance->pipe_keep_going = false; + else + top_pipe_keep_going = false; +}