From patchwork Thu Aug 12 15:50:28 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 12433839 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 E9B27C4320A for ; Thu, 12 Aug 2021 15:50:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB38460FBF for ; Thu, 12 Aug 2021 15:50:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238265AbhHLPu5 (ORCPT ); Thu, 12 Aug 2021 11:50:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:47000 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237013AbhHLPu4 (ORCPT ); Thu, 12 Aug 2021 11:50:56 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 652B860E93; Thu, 12 Aug 2021 15:50:31 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94.2) (envelope-from ) id 1mECyU-003ths-8r; Thu, 12 Aug 2021 11:50:30 -0400 From: Steven Rostedt To: linux-trace-devel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Tom Zanussi , Daniel Bristot de Oliveira , Masami Hiramatsu , "Steven Rostedt (VMware)" Subject: [PATCH v2 1/2] libtracefs: Add random number to keep synthetic variables unique Date: Thu, 12 Aug 2021 11:50:28 -0400 Message-Id: <20210812155029.929048-2-rostedt@goodmis.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210812155029.929048-1-rostedt@goodmis.org> References: <20210812155029.929048-1-rostedt@goodmis.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org From: "Steven Rostedt (VMware)" The 'hist' triggers expect that all variables are unique. If two synthetic events are created, it is possible that they will use the same variable names, and this can break the logic for synthetic events. Add a random number to the argument names that will help prevent that from happening. There's no guarantee that there wont be collisions, but the chances of that happening is 1 in 32768. If this is a problem, we could possibly look for variables that are already in use. Link: https://lore.kernel.org/linux-trace-devel/20210812005546.910833-2-rostedt@goodmis.org/ Signed-off-by: Steven Rostedt (VMware) --- src/tracefs-hist.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/src/tracefs-hist.c b/src/tracefs-hist.c index 7f9cf3820611..9de70579a871 100644 --- a/src/tracefs-hist.c +++ b/src/tracefs-hist.c @@ -13,6 +13,8 @@ #include #include #include +#include +#include #include "tracefs.h" #include "tracefs-local.h" @@ -558,6 +560,7 @@ struct tracefs_synth { unsigned int end_parens; unsigned int end_state; int *start_type; + char arg_name[16]; int arg_cnt; }; @@ -951,13 +954,31 @@ int tracefs_synth_add_match_field(struct tracefs_synth *synth, return -1; } +static unsigned int make_rand(void) +{ + struct timeval tv; + unsigned long seed; + + gettimeofday(&tv, NULL); + seed = (tv.tv_sec + tv.tv_usec) + gettid(); + + /* taken from the rand(3) man page */ + seed = seed * 1103515245 + 12345; + return((unsigned)(seed/65536) % 32768); +} + static char *new_arg(struct tracefs_synth *synth) { int cnt = synth->arg_cnt + 1; char *arg; int ret; - ret = asprintf(&arg, "__arg__%d", cnt); + /* Create a unique argument name */ + if (!synth->arg_name[0]) { + /* make_rand() returns at most 32768 (total 13 bytes in use) */ + sprintf(synth->arg_name, "__arg_%u_", make_rand()); + } + ret = asprintf(&arg, "%s%d", synth->arg_name, cnt); if (ret < 0) return NULL;