Messages in this thread Patch in this message | | | Subject | [patch 3/3] Trace samples | From | "David J. Wilder" <> | Date | Mon, 12 Nov 2007 17:02:22 -0800 |
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Trace example - Adds the trace example to samples/
Signed-off-by: David Wilder <dwilder@us.ibm.com> --- samples/Kconfig | 6 + samples/Makefile | 1 + samples/trace/Makefile | 4 + samples/trace/fork_trace.c | 132 ++++++++++++++++++++++++++ samples/trace/sem_watch.c | 224 ++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 367 insertions(+), 0 deletions(-)
diff --git a/samples/Kconfig b/samples/Kconfig index 57bb223..fa3c453 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -13,4 +13,10 @@ config SAMPLE_MARKERS help This build markers example modules. +config SAMPLE_TRACE + tristate "Build trace example -- loadable modules only" + depends on TRACE && KPROBES && m + help + This builds a trace example module. + endif # SAMPLES diff --git a/samples/Makefile b/samples/Makefile index 5a4f0b6..8f6d05b 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -1,3 +1,4 @@ # Makefile for Linux samples code obj-$(CONFIG_SAMPLES) += markers/ +obj-$(CONFIG_SAMPLES) += trace/ diff --git a/samples/trace/Makefile b/samples/trace/Makefile new file mode 100644 index 0000000..0168641 --- /dev/null +++ b/samples/trace/Makefile @@ -0,0 +1,4 @@ +# builds the trace example kernel modules; +# then to use (as root): insmod <fork_trace.ko> or <sem_watch.ko> + +obj-$(CONFIG_SAMPLE_TRACE) := fork_trace.o sem_watch.o diff --git a/samples/trace/fork_trace.c b/samples/trace/fork_trace.c new file mode 100644 index 0000000..71c04c7 --- /dev/null +++ b/samples/trace/fork_trace.c @@ -0,0 +1,132 @@ +/* + * An example of using trace in a kprobes module + * + * Copyright (C) 2007 IBM Inc. + * + * David Wilder <dwilder@us.ibm.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + * + * ------- + * This module creates a trace channel and places a kprobe + * on the function do_fork(). The value of current->pid is written to + * the trace channel each time the kprobe is hit.. + * + * How to run the example: + * $ mount -t debugfs /debug + * $ insmod fork_trace.ko + * + * To view the data produced by the module: + * $ cat /debug/trace_example/do_fork/trace0 + * + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/kprobes.h> +#include <linux/trace.h> + +#define USE_GLOBAL_BUFFERS 1 +#define USE_FLIGHT 1 + +#define PROBE_POINT "do_fork" + +static struct kprobe kp; +static struct trace_info *kprobes_trace; + +#ifdef USE_GLOBAL_BUFFERS +static DEFINE_SPINLOCK(trace_lock); +#endif + +/* + * Send formatted trace data to trace channel. + * @note Preemption must be disabled to use this. + */ +static void trace_printf(struct trace_info *trace, const char *format, ...) +{ + va_list ap, aq; + char *record; + unsigned long flags; + int len; + + if (!trace) + return; + +#ifdef USE_GLOBAL_BUFFERS + spin_lock_irqsave(&trace_lock, flags); +#endif + if (trace_running(trace)) { + va_start(ap, format); + va_copy(aq, ap); + len = vsnprintf(NULL, 0, format, aq); + va_end(aq); + record = relay_reserve(trace->rchan, ++len); + if (record) + vsnprintf(record, len, format, ap); + va_end(ap); + } +#ifdef USE_GLOBAL_BUFFERS + spin_unlock_irqrestore(&trace_lock, flags); +#endif +} + +static int handler_pre(struct kprobe *p, struct pt_regs *regs) +{ + rcu_read_lock(); + trace_printf(kprobes_trace, "%d\n", current->pid); + rcu_read_unlock(); + return 0; +} + +int init_module(void) +{ + int ret; + u32 flags = 0; + +#ifdef USE_GLOBAL_BUFFERS + flags |= TRACE_GLOBAL_CHANNEL; +#endif + +#ifdef USE_FLIGHT + flags |= TRACE_FLIGHT_CHANNEL; +#endif + + /* setup the trace */ + kprobes_trace = trace_setup("trace_example", PROBE_POINT, + 1024, 8, flags); + if (IS_ERR(kprobes_trace)) + return PTR_ERR(kprobes_trace); + + trace_start(kprobes_trace); + + /* setup the kprobe */ + kp.pre_handler = handler_pre; + kp.post_handler = NULL; + kp.fault_handler = NULL; + kp.symbol_name = PROBE_POINT; + ret = register_kprobe(&kp); + if (ret) { + printk(KERN_ERR "fork_trace: register_kprobe failed\n"); + return ret; + } + return 0; +} + +void cleanup_module(void) +{ + unregister_kprobe(&kp); + trace_stop(kprobes_trace); + trace_cleanup(kprobes_trace); +} +MODULE_LICENSE("GPL"); diff --git a/samples/trace/sem_watch.c b/samples/trace/sem_watch.c new file mode 100644 index 0000000..279aeb9 --- /dev/null +++ b/samples/trace/sem_watch.c @@ -0,0 +1,224 @@ +/* + * An example of using trace with marker probes + * + * Copyright (C) 2007 IBM Inc. + * + * David Wilder <dwilder@us.ibm.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + * + * ------- + * This example show how trace may be used to collect marker probe data. + * For this example to work a series of markers must be placed in + * lib/semaphore-sleepers.c. The markers record the execution of semaphore + * primitives. An example patch that places these markers can be + * found in the lkml archive. The data generated by this code can be used + * to analyze semaphore contention. + * + * How to run the example: + * $ mount -t debugfs /debug + * $ modprobe sem_watch + * + * To start the recording of trace data: + * echo start > /debug/trace_example/sem_watch/state + * + * Generate a test load and stop the trace: + * echo stop > /debug/trace_example/sem_watch/state + * + * Collect the data from the per-cpu trace buffers, sorting chronologically: + * sort --field-separator=: --key=2.1 /debug/trace_example/sem_watch/trace* + * + * Verify that no data was lost by examining the dropped file: + * cat /debug/trace_example/sem_watch/dropped + * + * To collect a larger amount of data the trace buffers can be read + * continuously using something like: + * + * echo start > /debug/trace_example/sem_watch/state + * while [ 1 ] ; do + * sort --field-separator=: --key=2.1 <.....>/trace* + * done + * echo stop > /debug/trace_example/sem_watch/state + * + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/ktime.h> +#include <linux/marker.h> +#include <linux/trace.h> + +#define modname "sem_watch" + +void probe_sem_generic(const struct marker *, void *, const char *, ...); + +static struct trace_info *sem_trace; + +struct probe_data { + const char *name; + const char *format; + marker_probe_func *probe_func; +}; + +/* marker probes array */ +static struct probe_data probes[] = +{ + { .name = "sem_up", + .format = "%p", + .probe_func = probe_sem_generic }, + + { .name = "sem_down", + .format = "%p", + .probe_func = probe_sem_generic }, + + { .name = "sem_down_sched", + .format = "%p", + .probe_func = probe_sem_generic }, + + { .name = "sem_down_resume", + .format = "%p", + .probe_func = probe_sem_generic }, + + { .name = "sem_down_intr", + .format = "%p", + .probe_func = probe_sem_generic }, + + { .name = "sem_down_intr_sched", + .format = "%p", + .probe_func = probe_sem_generic }, + + { .name = "sem_down_intr_fail", + .format = "%p", + .probe_func = probe_sem_generic }, + + { .name = "sem_down_intr_resume", + .format = "%p", + .probe_func = probe_sem_generic } +}; + +#define NPROBES ARRAY_SIZE(probes) + +inline s64 get_time(void) +{ + struct timespec ts; + ktime_get_real_ts(&ts); + return (s64) ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec; +} + +/** + * This probe function is called each time one of the semaphore markers is + * hit. Using the trace channel, we log a time stamp, the semaphore primitive + * (the probe name), address of the semaphore, pid and command name. + * For simplicity of the example, all log data is converter to ASCII. + * Logging binary data would be much more efficient, but requires a + * corresponding user program to interpret the data. + */ +void probe_sem_generic(const struct marker *mdata, void *private, + const char *format, ...) +{ + int len; + va_list ap; + char *record; + void *semaddr; + s64 tstamp; + struct probe_data *pd = (struct probe_data *) mdata->private; + + if (!sem_trace) + return; + + if (!trace_running(sem_trace)) + return; + + va_start(ap, format); + semaddr = va_arg(ap, void *); + va_end(ap); + + tstamp = get_time(); + + /** + * Log format :time-stamp:probe-name:semaddr:pid:command-name + */ + len = snprintf(NULL, 0, ":%lld:%s:%p:%d:%s\n", + tstamp, pd->name, semaddr, current->pid, current->comm); + + record = relay_reserve(sem_trace->rchan, ++len); + if (record) + snprintf(record, len, ":%lld:%s:%p:%d:%s\n", + tstamp, pd->name, semaddr, current->pid, current->comm); +} + +static void clean_up(void) +{ + int i; + + /* Deregister marker probes */ + for (i = 0; i < NPROBES; i++) + marker_probe_unregister(probes[i].name); + + synchronize_sched(); /* Wait for probes to finish */ + + /* Shut down the trace */ + trace_stop(sem_trace); + trace_cleanup(sem_trace); +} + +/** + * Initialize module + */ +static int __init sem_watch_init(void) +{ + int i, result; + + /* Setup the trace using per-cpu buffering */ + sem_trace = trace_setup("trace_example", modname, 2048, 8, 0); + if (IS_ERR(sem_trace)) + return PTR_ERR(sem_trace); + + + /* Register and arm marker probes */ + for (i = 0; i < NPROBES; i++) { + result = marker_probe_register(probes[i].name, probes[i].format, + probes[i].probe_func, &probes[i]); + if (result) { + printk(KERN_INFO "Unable to register probe %s\n", + probes[i].name); + break; + } + + result = marker_arm(probes[i].name); + if (result) { + printk(KERN_INFO "Unable to arm probe %s\n", + probes[i].name); + break; + } + } + + if (result) + clean_up(); + + return result; +} + +/** + * Exit module + */ +static void __exit sem_watch_exit(void) +{ + clean_up(); +} + +module_init(sem_watch_init); +module_exit(sem_watch_exit); + +MODULE_LICENSE("GPL");
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