tracing/events: add support for modules to TRACE_EVENT

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>

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 1781085..75f3ac0 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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);