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Subject[PATCH 8/8] tracing/events: add support for modules to TRACE_EVENT
From: Steven Rostedt <srostedt@redhat.com>

Impact: allow modules to add TRACE_EVENTS on load

This patch adds the final hooks to allow modules to use the TRACE_EVENT
macro. A notifier and a data structure are used to link the TRACE_EVENTs
defined in the module to connect them with the ftrace event tracing system.

It also adds the necessary automated clean ups to the trace events when a
module is removed.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
include/linux/ftrace_event.h | 3 +
include/linux/module.h | 4 +
include/linux/trace_seq.h | 2 +
include/trace/ftrace.h | 1 +
kernel/module.c | 7 ++
kernel/trace/trace_events.c | 128 +++++++++++++++++++++++++++++++-----------
6 files changed, 113 insertions(+), 32 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 1781085..75f3ac0 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -7,6 +7,7 @@

struct trace_array;
struct tracer;
+struct dentry;

/*
* The trace entry - the most basic unit of tracing. This is what
@@ -87,6 +88,7 @@ struct ftrace_event_call {
char *name;
char *system;
struct dentry *dir;
+ struct trace_event *event;
int enabled;
int (*regfunc)(void);
void (*unregfunc)(void);
@@ -97,6 +99,7 @@ struct ftrace_event_call {
struct list_head fields;
int n_preds;
struct filter_pred **preds;
+ void *mod;

#ifdef CONFIG_EVENT_PROFILE
atomic_t profile_count;
diff --git a/include/linux/module.h b/include/linux/module.h
index 627ac08..6155fa4 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -337,6 +337,10 @@ struct module
const char **trace_bprintk_fmt_start;
unsigned int num_trace_bprintk_fmt;
#endif
+#ifdef CONFIG_EVENT_TRACING
+ struct ftrace_event_call *trace_events;
+ unsigned int num_trace_events;
+#endif

#ifdef CONFIG_MODULE_UNLOAD
/* What modules depend on me? */
diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 28051da..15ca2c7 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -1,6 +1,8 @@
#ifndef _LINUX_TRACE_SEQ_H
#define _LINUX_TRACE_SEQ_H

+#include <linux/fs.h>
+
/*
* Trace sequences are used to allow a function to call several other functions
* to create a string of data to use (up to a max of PAGE_SIZE.
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 955b967..60c5323 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -477,6 +477,7 @@ __attribute__((__aligned__(4))) \
__attribute__((section("_ftrace_events"))) event_##call = { \
.name = #call, \
.system = __stringify(TRACE_SYSTEM), \
+ .event = &ftrace_event_type_##call, \
.raw_init = ftrace_raw_init_event_##call, \
.regfunc = ftrace_raw_reg_event_##call, \
.unregfunc = ftrace_raw_unreg_event_##call, \
diff --git a/kernel/module.c b/kernel/module.c
index e797812..a039470 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -18,6 +18,7 @@
*/
#include <linux/module.h>
#include <linux/moduleloader.h>
+#include <linux/ftrace_event.h>
#include <linux/init.h>
#include <linux/kallsyms.h>
#include <linux/fs.h>
@@ -2172,6 +2173,12 @@ static noinline struct module *load_module(void __user *umod,
sizeof(*mod->tracepoints),
&mod->num_tracepoints);
#endif
+#ifdef CONFIG_EVENT_TRACING
+ mod->trace_events = section_objs(hdr, sechdrs, secstrings,
+ "_ftrace_events",
+ sizeof(*mod->trace_events),
+ &mod->num_trace_events);
+#endif

#ifdef CONFIG_MODVERSIONS
if ((mod->num_syms && !mod->crcs)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 8b9e621..a4b1777 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -713,7 +713,13 @@ event_subsystem_dir(const char *name, struct dentry *d_events)
return d_events;
}

- system->name = name;
+ system->name = kstrdup(name, GFP_KERNEL);
+ if (!system->name) {
+ debugfs_remove(system->entry);
+ kfree(system);
+ return d_events;
+ }
+
list_add(&system->list, &event_subsystems);

system->preds = NULL;
@@ -738,7 +744,7 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
* If the trace point header did not define TRACE_SYSTEM
* then the system would be called "TRACE_SYSTEM".
*/
- if (strcmp(call->system, "TRACE_SYSTEM") != 0)
+ if (strcmp(call->system, TRACE_SYSTEM) != 0)
d_events = event_subsystem_dir(call->system, d_events);

if (call->raw_init) {
@@ -757,21 +763,13 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
return -1;
}

- if (call->regfunc) {
- entry = debugfs_create_file("enable", 0644, call->dir, call,
- &ftrace_enable_fops);
- if (!entry)
- pr_warning("Could not create debugfs "
- "'%s/enable' entry\n", call->name);
- }
+ if (call->regfunc)
+ entry = trace_create_file("enable", 0644, call->dir, call,
+ &ftrace_enable_fops);

- if (call->id) {
- entry = debugfs_create_file("id", 0444, call->dir, call,
- &ftrace_event_id_fops);
- if (!entry)
- pr_warning("Could not create debugfs '%s/id' entry\n",
- call->name);
- }
+ if (call->id)
+ entry = trace_create_file("id", 0444, call->dir, call,
+ &ftrace_event_id_fops);

if (call->define_fields) {
ret = call->define_fields();
@@ -780,40 +778,102 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
" events/%s\n", call->name);
return ret;
}
- entry = debugfs_create_file("filter", 0644, call->dir, call,
- &ftrace_event_filter_fops);
- if (!entry)
- pr_warning("Could not create debugfs "
- "'%s/filter' entry\n", call->name);
+ entry = trace_create_file("filter", 0644, call->dir, call,
+ &ftrace_event_filter_fops);
}

/* A trace may not want to export its format */
if (!call->show_format)
return 0;

- entry = debugfs_create_file("format", 0444, call->dir, call,
- &ftrace_event_format_fops);
- if (!entry)
- pr_warning("Could not create debugfs "
- "'%s/format' entry\n", call->name);
+ entry = trace_create_file("format", 0444, call->dir, call,
+ &ftrace_event_format_fops);
+
+ return 0;
+}
+
+#define for_each_event(event, start, end) \
+ for (event = start; \
+ (unsigned long)event < (unsigned long)end; \
+ event++)
+
+static void trace_module_add_events(struct module *mod)
+{
+ struct ftrace_event_call *call, *start, *end;
+ struct dentry *d_events;
+
+ start = mod->trace_events;
+ end = mod->trace_events + mod->num_trace_events;
+
+ if (start == end)
+ return;
+
+ d_events = event_trace_events_dir();
+ if (!d_events)
+ return;
+
+ for_each_event(call, start, end) {
+ /* The linker may leave blanks */
+ if (!call->name)
+ continue;
+ call->mod = mod;
+ list_add(&call->list, &ftrace_events);
+ event_create_dir(call, d_events);
+ }
+}
+
+static void trace_module_remove_events(struct module *mod)
+{
+ struct ftrace_event_call *call, *p;
+
+ list_for_each_entry_safe(call, p, &ftrace_events, list) {
+ if (call->mod == mod) {
+ if (call->enabled) {
+ call->enabled = 0;
+ call->unregfunc();
+ }
+ if (call->event)
+ unregister_ftrace_event(call->event);
+ debugfs_remove_recursive(call->dir);
+ list_del(&call->list);
+ }
+ }
+}
+
+int trace_module_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ struct module *mod = data;
+
+ mutex_lock(&event_mutex);
+ switch (val) {
+ case MODULE_STATE_COMING:
+ trace_module_add_events(mod);
+ break;
+ case MODULE_STATE_GOING:
+ trace_module_remove_events(mod);
+ break;
+ }
+ mutex_unlock(&event_mutex);

return 0;
}

+struct notifier_block trace_module_nb = {
+ .notifier_call = trace_module_notify,
+ .priority = 0,
+};
+
extern struct ftrace_event_call __start_ftrace_events[];
extern struct ftrace_event_call __stop_ftrace_events[];

-#define for_each_event(event) \
- for (event = __start_ftrace_events; \
- (unsigned long)event < (unsigned long)__stop_ftrace_events; \
- event++)
-
static __init int event_trace_init(void)
{
struct ftrace_event_call *call;
struct dentry *d_tracer;
struct dentry *entry;
struct dentry *d_events;
+ int ret;

d_tracer = tracing_init_dentry();
if (!d_tracer)
@@ -837,7 +897,7 @@ static __init int event_trace_init(void)
if (!d_events)
return 0;

- for_each_event(call) {
+ for_each_event(call, __start_ftrace_events, __stop_ftrace_events) {
/* The linker may leave blanks */
if (!call->name)
continue;
@@ -845,6 +905,10 @@ static __init int event_trace_init(void)
event_create_dir(call, d_events);
}

+ ret = register_module_notifier(&trace_module_nb);
+ if (!ret)
+ pr_warning("Failed to register trace events module notifier\n");
+
return 0;
}
fs_initcall(event_trace_init);
--
1.6.2.1
--


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