diff options
| -rw-r--r-- | samples/Kconfig | 7 | ||||
| -rw-r--r-- | samples/Makefile | 2 | ||||
| -rw-r--r-- | samples/trace_events/Makefile | 8 | ||||
| -rw-r--r-- | samples/trace_events/trace-events-sample.c | 56 | ||||
| -rw-r--r-- | samples/trace_events/trace-events-sample.h | 124 |
5 files changed, 196 insertions, 1 deletions
diff --git a/samples/Kconfig b/samples/Kconfig index 4b02f5a..93f41c0 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -19,6 +19,13 @@ config SAMPLE_TRACEPOINTS help This build tracepoints example modules. +config SAMPLE_TRACE_EVENTS + tristate "Build trace_events examples" + depends on EVENT_TRACING + default m + help + This build trace event example modules. + config SAMPLE_KOBJECT tristate "Build kobject examples" help diff --git a/samples/Makefile b/samples/Makefile index 10eaca8..13e4b47 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -1,3 +1,3 @@ # Makefile for Linux samples code -obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/ tracepoints/ +obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/ tracepoints/ trace_events/ diff --git a/samples/trace_events/Makefile b/samples/trace_events/Makefile new file mode 100644 index 0000000..06c6dea --- /dev/null +++ b/samples/trace_events/Makefile @@ -0,0 +1,8 @@ +# builds the trace events example kernel modules; +# then to use one (as root): insmod <module_name.ko> + +PWD := $(shell pwd) + +CFLAGS_trace-events-sample.o := -I$(PWD)/samples/trace_events/ + +obj-$(CONFIG_SAMPLE_TRACE_EVENTS) += trace-events-sample.o diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c new file mode 100644 index 0000000..f33b3ba --- /dev/null +++ b/samples/trace_events/trace-events-sample.c @@ -0,0 +1,56 @@ +#include <linux/module.h> +#include <linux/kthread.h> + +/* + * Any file that uses trace points, must include the header. + * But only one file, must include the header by defining + * CREATE_TRACE_POINTS first. This will make the C code that + * creates the handles for the trace points. + */ +#define CREATE_TRACE_POINTS +#include "trace-events-sample.h" + + +static void simple_thread_func(int cnt) +{ + set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(HZ); + trace_foo_bar("hello", cnt); + + if (!(cnt % 10)) + /* It is really important that I say "hi!" */ + printk(KERN_EMERG "hi!\n"); +} + +static int simple_thread(void *arg) +{ + int cnt = 0; + + while (!kthread_should_stop()) + simple_thread_func(cnt++); + + return 0; +} + +static struct task_struct *simple_tsk; + +static int __init trace_event_init(void) +{ + simple_tsk = kthread_run(simple_thread, NULL, "event-sample"); + if (IS_ERR(simple_tsk)) + return -1; + + return 0; +} + +static void __exit trace_event_exit(void) +{ + kthread_stop(simple_tsk); +} + +module_init(trace_event_init); +module_exit(trace_event_exit); + +MODULE_AUTHOR("Steven Rostedt"); +MODULE_DESCRIPTION("trace-events-sample"); +MODULE_LICENSE("GPL"); diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h new file mode 100644 index 0000000..eab4644 --- /dev/null +++ b/samples/trace_events/trace-events-sample.h @@ -0,0 +1,124 @@ +/* + * Notice that this file is not protected like a normal header. + * We also must allow for rereading of this file. The + * + * || defined(TRACE_HEADER_MULTI_READ) + * + * serves this purpose. + */ +#if !defined(_TRACE_EVENT_SAMPLE_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_EVENT_SAMPLE_H + +/* + * All trace headers should include tracepoint.h, until we finally + * make it into a standard header. + */ +#include <linux/tracepoint.h> + +/* + * If TRACE_SYSTEM is defined, that will be the directory created + * in the ftrace directory under /debugfs/tracing/events/<system> + * + * The define_trace.h belowe will also look for a file name of + * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here. + * + * If you want a different system than file name, you can override + * the header name by defining TRACE_INCLUDE_FILE + * + * If this file was called, goofy.h, then we would define: + * + * #define TRACE_INCLUDE_FILE goofy + * + */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM trace-events-sample + +/* + * The TRACE_EVENT macro is broken up into 5 parts. + * + * name: name of the trace point. This is also how to enable the tracepoint. + * A function called trace_foo_bar() will be created. + * + * proto: the prototype of the function trace_foo_bar() + * Here it is trace_foo_bar(char *foo, int bar). + * + * args: must match the arguments in the prototype. + * Here it is simply "foo, bar". + * + * struct: This defines the way the data will be stored in the ring buffer. + * There are currently two types of elements. __field and __array. + * a __field is broken up into (type, name). Where type can be any + * type but an array. + * For an array. there are three fields. (type, name, size). The + * type of elements in the array, the name of the field and the size + * of the array. + * + * __array( char, foo, 10) is the same as saying char foo[10]. + * + * fast_assign: This is a C like function that is used to store the items + * into the ring buffer. + * + * printk: This is a way to print out the data in pretty print. This is + * useful if the system crashes and you are logging via a serial line, + * the data can be printed to the console using this "printk" method. + * + * Note, that for both the assign and the printk, __entry is the handler + * to the data structure in the ring buffer, and is defined by the + * TP_STRUCT__entry. + */ +TRACE_EVENT(foo_bar, + + TP_PROTO(char *foo, int bar), + + TP_ARGS(foo, bar), + + TP_STRUCT__entry( + __array( char, foo, 10 ) + __field( int, bar ) + ), + + TP_fast_assign( + strncpy(__entry->foo, foo, 10); + __entry->bar = bar; + ), + + TP_printk("foo %s %d", __entry->foo, __entry->bar) +); +#endif + +/***** NOTICE! The #if protection ends here. *****/ + + +/* + * There are several ways I could have done this. If I left out the + * TRACE_INCLUDE_PATH, then it would default to the kernel source + * include/trace/events directory. + * + * I could specify a path from the define_trace.h file back to this + * file. + * + * #define TRACE_INCLUDE_PATH ../../samples/trace_events + * + * But I chose to simply make it use the current directory and then in + * the Makefile I added: + * + * CFLAGS_trace-events-sample.o := -I$(PWD)/samples/trace_events/ + * + * This will make sure the current path is part of the include + * structure for our file so that we can find it. + * + * I could have made only the top level directory the include: + * + * CFLAGS_trace-events-sample.o := -I$(PWD) + * + * And then let the path to this directory be the TRACE_INCLUDE_PATH: + * + * #define TRACE_INCLUDE_PATH samples/trace_events + * + * But then if something defines "samples" or "trace_events" then we + * could risk that being converted too, and give us an unexpected + * result. + */ +#undef TRACE_INCLUDE_PATH +#define TRACE_INCLUDE_PATH . +#include <trace/define_trace.h> |
