From patchwork Tue Jan 16 19:53:41 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Vladislav Valtchev (VMware)" X-Patchwork-Id: 10758489 Return-Path: linux-trace-devel-owner@vger.kernel.org Received: from mail-wr0-f196.google.com ([209.85.128.196]:46007 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751280AbeAPTyv (ORCPT ); Tue, 16 Jan 2018 14:54:51 -0500 From: "Vladislav Valtchev (VMware)" To: rostedt@goodmis.org Cc: linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, y.karadz@gmail.com, "Vladislav Valtchev (VMware)" Subject: [PATCH v4 1/3] trace-cmd: Make read_proc() to return int status via OUT arg Date: Tue, 16 Jan 2018 21:53:41 +0200 Message-Id: <20180116195343.12800-2-vladislav.valtchev@gmail.com> In-Reply-To: <20180116195343.12800-1-vladislav.valtchev@gmail.com> References: <20180116195343.12800-1-vladislav.valtchev@gmail.com> Sender: linux-trace-devel-owner@vger.kernel.org List-ID: Content-Length: 3714 This patch changes both the implementation and the interface of read_proc() in trace-stack.c. First, it makes the function to read a string from the proc file and then parse it as an integer using strtol(). Then, it makes the function to return the integer read from the proc file using the int *status OUT parameter, in order to make possible its return value to be used by the caller to check if the operation succeeded. This new implementation relaxes the external contraints the function relies on, making it possible to be used by trace stat. The point is that 'stat' should not fail in case there is something wrong with the stack tracer. Only the call to die() in case the file is empty has been left in this patch: it will be removed as well in a separate commit. Signed-off-by: Vladislav Valtchev (VMware) --- trace-stack.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 57 insertions(+), 15 deletions(-) diff --git a/trace-stack.c b/trace-stack.c index aa79ae3..fada62d 100644 --- a/trace-stack.c +++ b/trace-stack.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include #include @@ -49,37 +50,74 @@ static void test_available(void) die("stack tracer not configured on running kernel"); } -static char read_proc(void) +/* + * Returns: + * -1 - Something went wrong + * 0 - File does not exist (stack tracer not enabled) + * 1 - Success + */ +static int read_proc(int *status) { - char buf[1]; + struct stat stat_buf; + char buf[64]; + long num; int fd; int n; + if (stat(PROC_FILE, &stat_buf) < 0) { + /* stack tracer not configured on running kernel */ + *status = 0; /* not configured means disabled */ + return 0; + } + fd = open(PROC_FILE, O_RDONLY); + if (fd < 0) - die("reading %s", PROC_FILE); - n = read(fd, buf, 1); + return -1; + + n = read(fd, buf, sizeof(buf)); close(fd); - if (n != 1) + + if (n <= 0) die("error reading %s", PROC_FILE); - return buf[0]; + if (n >= sizeof(buf)) + return -1; + + buf[n] = 0; + errno = 0; + num = strtol(buf, NULL, 10); + + /* Check for various possible errors */ + if (num > INT_MAX || num < INT_MIN || (!num && errno)) + return -1; + + *status = num; + return 1; /* full success */ } -static void start_stop_trace(char val) +/* NOTE: this implementation only accepts new_status in the range [0..9]. */ +static void change_stack_tracer_status(unsigned new_status) { char buf[1]; + int status; int fd; int n; - buf[0] = read_proc(); - if (buf[0] == val) + if (new_status > 9) { + warning("invalid status %d\n", new_status); return; + } + + if (read_proc(&status) > 0 && status == new_status) + return; /* nothing to do */ fd = open(PROC_FILE, O_WRONLY); if (fd < 0) die("writing %s", PROC_FILE); - buf[0] = val; + + buf[0] = new_status + '0'; + n = write(fd, buf, 1); if (n < 0) die("writing into %s", PROC_FILE); @@ -88,12 +126,12 @@ static void start_stop_trace(char val) static void start_trace(void) { - start_stop_trace('1'); + change_stack_tracer_status(1); } static void stop_trace(void) { - start_stop_trace('0'); + change_stack_tracer_status(0); } static void reset_trace(void) @@ -118,13 +156,17 @@ static void reset_trace(void) static void read_trace(void) { - FILE *fp; - char *path; char *buf = NULL; + int status; + char *path; + FILE *fp; size_t n; int r; - if (read_proc() == '1') + if (read_proc(&status) <= 0) + die("Invalid stack tracer state"); + + if (status > 0) printf("(stack tracer running)\n"); else printf("(stack tracer not running)\n"); From patchwork Tue Jan 16 19:53:42 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Vladislav Valtchev (VMware)" X-Patchwork-Id: 10758485 Return-Path: linux-trace-devel-owner@vger.kernel.org Received: from mail-wr0-f196.google.com ([209.85.128.196]:36904 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751628AbeAPTyw (ORCPT ); Tue, 16 Jan 2018 14:54:52 -0500 From: "Vladislav Valtchev (VMware)" To: rostedt@goodmis.org Cc: linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, y.karadz@gmail.com, "Vladislav Valtchev (VMware)" Subject: [PATCH v4 2/3] trace-cmd: Remove the die() call from read_proc() Date: Tue, 16 Jan 2018 21:53:42 +0200 Message-Id: <20180116195343.12800-3-vladislav.valtchev@gmail.com> In-Reply-To: <20180116195343.12800-1-vladislav.valtchev@gmail.com> References: <20180116195343.12800-1-vladislav.valtchev@gmail.com> Sender: linux-trace-devel-owner@vger.kernel.org List-ID: Content-Length: 1245 As trace-stack.c's read_proc() function is going to be used by trace-cmd stat, we don't want it to make the program die in case something went wrong. Therefore, this simple patch makes read_proc() to just return -1 in case the proc file was empty or read() failed with an error, instead of using die(). Signed-off-by: Vladislav Valtchev (VMware) --- trace-stack.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/trace-stack.c b/trace-stack.c index fada62d..3e1e41b 100644 --- a/trace-stack.c +++ b/trace-stack.c @@ -79,7 +79,7 @@ static int read_proc(int *status) close(fd); if (n <= 0) - die("error reading %s", PROC_FILE); + return -1; if (n >= sizeof(buf)) return -1; @@ -101,6 +101,7 @@ static void change_stack_tracer_status(unsigned new_status) { char buf[1]; int status; + int ret; int fd; int n; @@ -109,7 +110,11 @@ static void change_stack_tracer_status(unsigned new_status) return; } - if (read_proc(&status) > 0 && status == new_status) + ret = read_proc(&status); + if (ret < 0) + die("error reading %s", PROC_FILE); + + if (ret > 0 && status == new_status) return; /* nothing to do */ fd = open(PROC_FILE, O_WRONLY); From patchwork Tue Jan 16 19:53:43 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Vladislav Valtchev (VMware)" X-Patchwork-Id: 10758487 Return-Path: linux-trace-devel-owner@vger.kernel.org Received: from mail-wr0-f196.google.com ([209.85.128.196]:41944 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750941AbeAPTyx (ORCPT ); Tue, 16 Jan 2018 14:54:53 -0500 From: "Vladislav Valtchev (VMware)" To: rostedt@goodmis.org Cc: linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, y.karadz@gmail.com, "Vladislav Valtchev (VMware)" Subject: [PATCH v4 3/3] trace-cmd: Making stat to report when the stack tracer is ON Date: Tue, 16 Jan 2018 21:53:43 +0200 Message-Id: <20180116195343.12800-4-vladislav.valtchev@gmail.com> In-Reply-To: <20180116195343.12800-1-vladislav.valtchev@gmail.com> References: <20180116195343.12800-1-vladislav.valtchev@gmail.com> Sender: linux-trace-devel-owner@vger.kernel.org List-ID: Content-Length: 1896 trace-cmd stat is a handy way for users to see what tracing is currently going on, but currently it does not say anything about the stack tracing. This patch makes the command to show a message when the stack tracer is ON. Signed-off-by: Vladislav Valtchev (VMware) --- trace-cmd.h | 2 ++ trace-stack.c | 6 ++++++ trace-stat.c | 8 ++++++++ 3 files changed, 16 insertions(+) diff --git a/trace-cmd.h b/trace-cmd.h index 6fd34d7..9704b2e 100644 --- a/trace-cmd.h +++ b/trace-cmd.h @@ -358,6 +358,8 @@ void tracecmd_free_hooks(struct hook_list *hooks); /* --- Hack! --- */ int tracecmd_blk_hack(struct tracecmd_input *handle); +/* --- Stack tracer functions --- */ +int tracecmd_stack_tracer_status(int *status); /* --- Debugging --- */ struct kbuffer *tracecmd_record_kbuf(struct tracecmd_input *handle, diff --git a/trace-stack.c b/trace-stack.c index 3e1e41b..65a74ad 100644 --- a/trace-stack.c +++ b/trace-stack.c @@ -96,6 +96,12 @@ static int read_proc(int *status) return 1; /* full success */ } +/* Public wrapper of read_proc() */ +int tracecmd_stack_tracer_status(int *status) +{ + return read_proc(status); +} + /* NOTE: this implementation only accepts new_status in the range [0..9]. */ static void change_stack_tracer_status(unsigned new_status) { diff --git a/trace-stat.c b/trace-stat.c index fd16354..23d7dd4 100644 --- a/trace-stat.c +++ b/trace-stat.c @@ -893,6 +893,7 @@ void trace_stat (int argc, char **argv) { struct buffer_instance *instance = &top_instance; int topt = 0; + int status; int c; for (;;) { @@ -928,5 +929,12 @@ void trace_stat (int argc, char **argv) stat_instance(instance); } + if (tracecmd_stack_tracer_status(&status) >= 0) { + if (status > 0) + printf("Stack tracing is enabled\n\n"); + } else { + printf("Error reading stack tracer status\n\n"); + } + exit(0); }