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Subject[PATCH 1/4][RFC] tracing: add event trace infrastructure
From: Steven Rostedt <srostedt@redhat.com>

This patch creates the event tracing infrastructure of ftrace.
It will create the files:

/debug/tracing/available_events
/debug/tracing/set_event

The available_events will list the trace points that have been
registered with the event tracer.

set_events will allow the user to enable or disable an event hook.

example:

# echo sched_wakeup > /debug/tracing/set_event
Will enable the sched_wakeup event (if it is registered).

# echo "!sched_wakeup" >> /debug/tracing/set_event

Will disable the sched_wakeup event (and only that event).

# echo > /debug/tracing/set_event
Will disable all events (notice the '>')

# cat /debug/tracing/available_events > /debug/tracing/set_event
Will enable all registered event hooks.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
include/asm-generic/vmlinux.lds.h | 11 ++-
kernel/trace/Kconfig | 9 ++
kernel/trace/Makefile | 1 +
kernel/trace/trace_events.c | 280 +++++++++++++++++++++++++++++++++++++
kernel/trace/trace_events.h | 49 +++++++
5 files changed, 349 insertions(+), 1 deletions(-)
create mode 100644 kernel/trace/trace_events.c
create mode 100644 kernel/trace/trace_events.h
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 5406e70..9d97491 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -61,6 +61,14 @@
#define BRANCH_PROFILE()
#endif

+#ifdef CONFIG_EVENT_TRACER
+#define FTRACE_EVENTS() VMLINUX_SYMBOL(__start_ftrace_events) = .; \
+ *(_ftrace_events) \
+ VMLINUX_SYMBOL(__stop_ftrace_events) = .;
+#else
+#define FTRACE_EVENTS()
+#endif
+
/* .data section */
#define DATA_DATA \
*(.data) \
@@ -81,7 +89,8 @@
*(__tracepoints) \
VMLINUX_SYMBOL(__stop___tracepoints) = .; \
LIKELY_PROFILE() \
- BRANCH_PROFILE()
+ BRANCH_PROFILE() \
+ FTRACE_EVENTS()

#define RO_DATA(align) \
. = ALIGN((align)); \
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 9e4f17c..02bc5d6 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -159,6 +159,15 @@ config CONTEXT_SWITCH_TRACER
This tracer gets called from the context switch and records
all switching of tasks.

+config EVENT_TRACER
+ bool "Trace various events in the kernel"
+ depends on DEBUG_KERNEL
+ select TRACING
+ help
+ This tracer hooks to various trace points in the kernel
+ allowing the user to pick and choose which trace point they
+ want to trace.
+
config BOOT_TRACER
bool "Trace boot initcalls"
depends on DEBUG_KERNEL
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 627090b..c736356 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -38,5 +38,6 @@ obj-$(CONFIG_POWER_TRACER) += trace_power.o
obj-$(CONFIG_KMEMTRACE) += kmemtrace.o
obj-$(CONFIG_WORKQUEUE_TRACER) += trace_workqueue.o
obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
+obj-$(CONFIG_EVENT_TRACER) += trace_events.o

libftrace-y := ftrace.o
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
new file mode 100644
index 0000000..05bc80e
--- /dev/null
+++ b/kernel/trace/trace_events.c
@@ -0,0 +1,280 @@
+/*
+ * event tracer
+ *
+ * Copyright (C) 2008 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
+ *
+ */
+
+#include <linux/debugfs.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/ctype.h>
+
+#include "trace_events.h"
+
+void event_trace_printk(unsigned long ip, const char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ tracing_record_cmdline(current);
+ trace_vprintk(ip, task_curr_ret_stack(current), fmt, ap);
+ va_end(ap);
+}
+
+static void ftrace_clear_events(void)
+{
+ struct ftrace_event_call *call = (void *)__start_ftrace_events;
+
+
+ while ((unsigned long)call < (unsigned long)__stop_ftrace_events) {
+
+ if (call->enabled) {
+ call->enabled = 0;
+ call->unregfunc();
+ }
+ call++;
+ }
+}
+
+static int ftrace_set_clr_event(char *buf, int set)
+{
+ struct ftrace_event_call *call = (void *)__start_ftrace_events;
+
+
+ while ((unsigned long)call < (unsigned long)__stop_ftrace_events) {
+
+ if (strcmp(buf, call->name) != 0) {
+ call++;
+ continue;
+ }
+
+ if (set) {
+ /* Already set? */
+ if (call->enabled)
+ return 0;
+ call->enabled = 1;
+ call->regfunc();
+ } else {
+ /* Already cleared? */
+ if (!call->enabled)
+ return 0;
+ call->enabled = 0;
+ call->unregfunc();
+ }
+ return 0;
+ }
+ return -EINVAL;
+}
+
+/* 128 should be much more than enough */
+#define EVENT_BUF_SIZE 127
+
+static ssize_t
+ftrace_event_write(struct file *file, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ size_t read = 0;
+ int i, set = 1;
+ ssize_t ret;
+ char *buf;
+ char ch;
+
+ if (!cnt || cnt < 0)
+ return 0;
+
+ ret = get_user(ch, ubuf++);
+ if (ret)
+ return ret;
+ read++;
+ cnt--;
+
+ /* skip white space */
+ while (cnt && isspace(ch)) {
+ ret = get_user(ch, ubuf++);
+ if (ret)
+ return ret;
+ read++;
+ cnt--;
+ }
+
+ /* Only white space found? */
+ if (isspace(ch)) {
+ file->f_pos += read;
+ ret = read;
+ return ret;
+ }
+
+ buf = kmalloc(EVENT_BUF_SIZE+1, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ if (cnt > EVENT_BUF_SIZE)
+ cnt = EVENT_BUF_SIZE;
+
+ i = 0;
+ while (cnt && !isspace(ch)) {
+ if (!i && ch == '!')
+ set = 0;
+ else
+ buf[i++] = ch;
+
+ ret = get_user(ch, ubuf++);
+ if (ret)
+ goto out_free;
+ read++;
+ cnt--;
+ }
+ buf[i] = 0;
+
+ file->f_pos += read;
+
+ ret = ftrace_set_clr_event(buf, set);
+ if (ret)
+ goto out_free;
+
+ ret = read;
+
+ out_free:
+ kfree(buf);
+
+ return ret;
+}
+
+static void *
+t_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ struct ftrace_event_call *call = m->private;
+ struct ftrace_event_call *next = call;
+
+ (*pos)++;
+
+ if ((unsigned long)call >= (unsigned long)__stop_ftrace_events)
+ return NULL;
+
+ m->private = ++next;
+
+ return call;
+}
+
+static void *t_start(struct seq_file *m, loff_t *pos)
+{
+ return t_next(m, NULL, pos);
+}
+
+static void *
+s_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ struct ftrace_event_call *call = m->private;
+ struct ftrace_event_call *next;
+
+ (*pos)++;
+
+ retry:
+ if ((unsigned long)call >= (unsigned long)__stop_ftrace_events)
+ return NULL;
+
+ if (!call->enabled) {
+ call++;
+ goto retry;
+ }
+
+ next = call;
+ m->private = ++next;
+
+ return call;
+}
+
+static void *s_start(struct seq_file *m, loff_t *pos)
+{
+ return s_next(m, NULL, pos);
+}
+
+static int t_show(struct seq_file *m, void *v)
+{
+ struct ftrace_event_call *call = v;
+
+ seq_printf(m, "%s\n", call->name);
+
+ return 0;
+}
+
+static void t_stop(struct seq_file *m, void *p)
+{
+}
+
+static int
+ftrace_event_seq_open(struct inode *inode, struct file *file)
+{
+ int ret;
+ const struct seq_operations *seq_ops;
+
+ if ((file->f_mode & FMODE_WRITE) &&
+ !(file->f_flags & O_APPEND))
+ ftrace_clear_events();
+
+ seq_ops = inode->i_private;
+ ret = seq_open(file, seq_ops);
+ if (!ret) {
+ struct seq_file *m = file->private_data;
+
+ m->private = __start_ftrace_events;
+ }
+ return ret;
+}
+
+static const struct seq_operations show_event_seq_ops = {
+ .start = t_start,
+ .next = t_next,
+ .show = t_show,
+ .stop = t_stop,
+};
+
+static const struct seq_operations show_set_event_seq_ops = {
+ .start = s_start,
+ .next = s_next,
+ .show = t_show,
+ .stop = t_stop,
+};
+
+static const struct file_operations ftrace_avail_fops = {
+ .open = ftrace_event_seq_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static const struct file_operations ftrace_set_event_fops = {
+ .open = ftrace_event_seq_open,
+ .read = seq_read,
+ .write = ftrace_event_write,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static __init int event_trace_init(void)
+{
+ struct dentry *d_tracer;
+ struct dentry *entry;
+
+ d_tracer = tracing_init_dentry();
+ if (!d_tracer)
+ return 0;
+
+ entry = debugfs_create_file("available_events", 0444, d_tracer,
+ (void *)&show_event_seq_ops,
+ &ftrace_avail_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs "
+ "'available_events' entry\n");
+
+ entry = debugfs_create_file("set_event", 0644, d_tracer,
+ (void *)&show_set_event_seq_ops,
+ &ftrace_set_event_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs "
+ "'set_event' entry\n");
+
+ return 0;
+}
+fs_initcall(event_trace_init);
diff --git a/kernel/trace/trace_events.h b/kernel/trace/trace_events.h
new file mode 100644
index 0000000..aa82057
--- /dev/null
+++ b/kernel/trace/trace_events.h
@@ -0,0 +1,49 @@
+#ifndef _LINUX_KERNEL_TRACE_EVENTS_H
+#define _LINUX_KERNEL_TRACE_EVENTS_H
+
+#include <linux/ftrace.h>
+#include "trace.h"
+
+struct ftrace_event_call {
+ char *name;
+ int enabled;
+ int (*regfunc)(void);
+ void (*unregfunc)(void);
+};
+
+
+#undef DECLARE_TRACE_FMT
+#define DECLARE_TRACE_FMT(call, proto, args, fmt, fmt_args) \
+static void ftrace_event_##call(proto) \
+{ \
+ event_trace_printk(_RET_IP_, "(%s) " fmt "\n", #call, fmt_args); \
+} \
+ \
+static int ftrace_reg_event_##call(void) \
+{ \
+ int ret; \
+ \
+ ret = register_trace_##call(ftrace_event_##call); \
+ if (!ret) \
+ pr_info("event trace: Could not activate trace point " \
+ "probe to " #call); \
+ return ret; \
+} \
+ \
+static void ftrace_unreg_event_##call(void) \
+{ \
+ unregister_trace_##call(ftrace_event_##call); \
+} \
+ \
+static struct ftrace_event_call __used \
+__attribute__((section("_ftrace_events"))) event_##call = { \
+ .name = #call, \
+ .regfunc = ftrace_reg_event_##call, \
+ .unregfunc = ftrace_unreg_event_##call, \
+}
+
+void event_trace_printk(unsigned long ip, const char *fmt, ...);
+extern unsigned long __start_ftrace_events[];
+extern unsigned long __stop_ftrace_events[];
+
+#endif /* _LINUX_KERNEL_TRACE_EVENTS_H */
--
1.5.6.5
--


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