tracing: Add 'enable_event' and 'disable_event' event trigger commands

Add 'enable_event' and 'disable_event' event_command commands.

enable_event and disable_event event triggers are added by the user
via these commands in a similar way and using practically the same
syntax as the analagous 'enable_event' and 'disable_event' ftrace
function commands, but instead of writing to the set_ftrace_filter
file, the enable_event and disable_event triggers are written to the
per-event 'trigger' files:

    echo 'enable_event:system:event' > .../othersys/otherevent/trigger
    echo 'disable_event:system:event' > .../othersys/otherevent/trigger

The above commands will enable or disable the 'system:event' trace
events whenever the othersys:otherevent events are hit.

This also adds a 'count' version that limits the number of times the
command will be invoked:

    echo 'enable_event:system:event:N' > .../othersys/otherevent/trigger
    echo 'disable_event:system:event:N' > .../othersys/otherevent/trigger

Where N is the number of times the command will be invoked.

The above commands will will enable or disable the 'system:event'
trace events whenever the othersys:otherevent events are hit, but only
N times.

This also makes the find_event_file() helper function extern, since
it's useful to use from other places, such as the event triggers code,
so make it accessible.

Link: http://lkml.kernel.org/r/f825f3048c3f6b026ee37ae5825f9fc373451828.1382622043.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 364 insertions, 1 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 50723e5e2b3c..ccbd8104cf99 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1028,6 +1028,10 @@ extern void trace_event_enable_cmd_record(bool enable);
 extern int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr);
 extern int event_trace_del_tracer(struct trace_array *tr);
 
+extern struct ftrace_event_file *find_event_file(struct trace_array *tr,
+                                                 const char *system,
+                                                 const char *event);
+
 static inline void *event_file_data(struct file *filp)
 {
         return ACCESS_ONCE(file_inode(filp)->i_private);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 442775c9dbf3..9a974bd843d4 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1868,7 +1868,7 @@ struct event_probe_data {
         bool                            enable;
 };
 
-static struct ftrace_event_file *
+struct ftrace_event_file *
 find_event_file(struct trace_array *tr, const char *system,  const char *event)
 {
         struct ftrace_event_file *file;
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index a3bd1da90c56..45e48b109d51 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -864,6 +864,364 @@ static __init void unregister_trigger_traceon_traceoff_cmds(void)
         unregister_event_command(&trigger_traceoff_cmd);
 }
 
+/* Avoid typos */
+#define ENABLE_EVENT_STR        "enable_event"
+#define DISABLE_EVENT_STR       "disable_event"
+
+struct enable_trigger_data {
+        struct ftrace_event_file        *file;
+        bool                            enable;
+};
+
+static void
+event_enable_trigger(struct event_trigger_data *data)
+{
+        struct enable_trigger_data *enable_data = data->private_data;
+
+        if (enable_data->enable)
+                clear_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &enable_data->file->flags);
+        else
+                set_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &enable_data->file->flags);
+}
+
+static void
+event_enable_count_trigger(struct event_trigger_data *data)
+{
+        struct enable_trigger_data *enable_data = data->private_data;
+
+        if (!data->count)
+                return;
+
+        /* Skip if the event is in a state we want to switch to */
+        if (enable_data->enable == !(enable_data->file->flags & FTRACE_EVENT_FL_SOFT_DISABLED))
+                return;
+
+        if (data->count != -1)
+                (data->count)--;
+
+        event_enable_trigger(data);
+}
+
+static int
+event_enable_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
+                           struct event_trigger_data *data)
+{
+        struct enable_trigger_data *enable_data = data->private_data;
+
+        seq_printf(m, "%s:%s:%s",
+                   enable_data->enable ? ENABLE_EVENT_STR : DISABLE_EVENT_STR,
+                   enable_data->file->event_call->class->system,
+                   enable_data->file->event_call->name);
+
+        if (data->count == -1)
+                seq_puts(m, ":unlimited");
+        else
+                seq_printf(m, ":count=%ld", data->count);
+
+        if (data->filter_str)
+                seq_printf(m, " if %s\n", data->filter_str);
+        else
+                seq_puts(m, "\n");
+
+        return 0;
+}
+
+static void
+event_enable_trigger_free(struct event_trigger_ops *ops,
+                          struct event_trigger_data *data)
+{
+        struct enable_trigger_data *enable_data = data->private_data;
+
+        if (WARN_ON_ONCE(data->ref <= 0))
+                return;
+
+        data->ref--;
+        if (!data->ref) {
+                /* Remove the SOFT_MODE flag */
+                trace_event_enable_disable(enable_data->file, 0, 1);
+                module_put(enable_data->file->event_call->mod);
+                trigger_data_free(data);
+                kfree(enable_data);
+        }
+}
+
+static struct event_trigger_ops event_enable_trigger_ops = {
+        .func                   = event_enable_trigger,
+        .print                  = event_enable_trigger_print,
+        .init                   = event_trigger_init,
+        .free                   = event_enable_trigger_free,
+};
+
+static struct event_trigger_ops event_enable_count_trigger_ops = {
+        .func                   = event_enable_count_trigger,
+        .print                  = event_enable_trigger_print,
+        .init                   = event_trigger_init,
+        .free                   = event_enable_trigger_free,
+};
+
+static struct event_trigger_ops event_disable_trigger_ops = {
+        .func                   = event_enable_trigger,
+        .print                  = event_enable_trigger_print,
+        .init                   = event_trigger_init,
+        .free                   = event_enable_trigger_free,
+};
+
+static struct event_trigger_ops event_disable_count_trigger_ops = {
+        .func                   = event_enable_count_trigger,
+        .print                  = event_enable_trigger_print,
+        .init                   = event_trigger_init,
+        .free                   = event_enable_trigger_free,
+};
+
+static int
+event_enable_trigger_func(struct event_command *cmd_ops,
+                          struct ftrace_event_file *file,
+                          char *glob, char *cmd, char *param)
+{
+        struct ftrace_event_file *event_enable_file;
+        struct enable_trigger_data *enable_data;
+        struct event_trigger_data *trigger_data;
+        struct event_trigger_ops *trigger_ops;
+        struct trace_array *tr = file->tr;
+        const char *system;
+        const char *event;
+        char *trigger;
+        char *number;
+        bool enable;
+        int ret;
+
+        if (!param)
+                return -EINVAL;
+
+        /* separate the trigger from the filter (s:e:n [if filter]) */
+        trigger = strsep(&param, " \t");
+        if (!trigger)
+                return -EINVAL;
+
+        system = strsep(&trigger, ":");
+        if (!trigger)
+                return -EINVAL;
+
+        event = strsep(&trigger, ":");
+
+        ret = -EINVAL;
+        event_enable_file = find_event_file(tr, system, event);
+        if (!event_enable_file)
+                goto out;
+
+        enable = strcmp(cmd, ENABLE_EVENT_STR) == 0;
+
+        trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);
+
+        ret = -ENOMEM;
+        trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
+        if (!trigger_data)
+                goto out;
+
+        enable_data = kzalloc(sizeof(*enable_data), GFP_KERNEL);
+        if (!enable_data) {
+                kfree(trigger_data);
+                goto out;
+        }
+
+        trigger_data->count = -1;
+        trigger_data->ops = trigger_ops;
+        trigger_data->cmd_ops = cmd_ops;
+        INIT_LIST_HEAD(&trigger_data->list);
+        RCU_INIT_POINTER(trigger_data->filter, NULL);
+
+        enable_data->enable = enable;
+        enable_data->file = event_enable_file;
+        trigger_data->private_data = enable_data;
+
+        if (glob[0] == '!') {
+                cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
+                kfree(trigger_data);
+                kfree(enable_data);
+                ret = 0;
+                goto out;
+        }
+
+        if (trigger) {
+                number = strsep(&trigger, ":");
+
+                ret = -EINVAL;
+                if (!strlen(number))
+                        goto out_free;
+
+                /*
+                 * We use the callback data field (which is a pointer)
+                 * as our counter.
+                 */
+                ret = kstrtoul(number, 0, &trigger_data->count);
+                if (ret)
+                        goto out_free;
+        }
+
+        if (!param) /* if param is non-empty, it's supposed to be a filter */
+                goto out_reg;
+
+        if (!cmd_ops->set_filter)
+                goto out_reg;
+
+        ret = cmd_ops->set_filter(param, trigger_data, file);
+        if (ret < 0)
+                goto out_free;
+
+ out_reg:
+        /* Don't let event modules unload while probe registered */
+        ret = try_module_get(event_enable_file->event_call->mod);
+        if (!ret) {
+                ret = -EBUSY;
+                goto out_free;
+        }
+
+        ret = trace_event_enable_disable(event_enable_file, 1, 1);
+        if (ret < 0)
+                goto out_put;
+        ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
+        /*
+         * The above returns on success the # of functions enabled,
+         * but if it didn't find any functions it returns zero.
+         * Consider no functions a failure too.
+         */
+        if (!ret) {
+                ret = -ENOENT;
+                goto out_disable;
+        } else if (ret < 0)
+                goto out_disable;
+        /* Just return zero, not the number of enabled functions */
+        ret = 0;
+ out:
+        return ret;
+
+ out_disable:
+        trace_event_enable_disable(event_enable_file, 0, 1);
+ out_put:
+        module_put(event_enable_file->event_call->mod);
+ out_free:
+        kfree(trigger_data);
+        kfree(enable_data);
+        goto out;
+}
+
+static int event_enable_register_trigger(char *glob,
+                                         struct event_trigger_ops *ops,
+                                         struct event_trigger_data *data,
+                                         struct ftrace_event_file *file)
+{
+        struct enable_trigger_data *enable_data = data->private_data;
+        struct enable_trigger_data *test_enable_data;
+        struct event_trigger_data *test;
+        int ret = 0;
+
+        list_for_each_entry_rcu(test, &file->triggers, list) {
+                test_enable_data = test->private_data;
+                if (test_enable_data &&
+                    (test_enable_data->file == enable_data->file)) {
+                        ret = -EEXIST;
+                        goto out;
+                }
+        }
+
+        if (data->ops->init) {
+                ret = data->ops->init(data->ops, data);
+                if (ret < 0)
+                        goto out;
+        }
+
+        list_add_rcu(&data->list, &file->triggers);
+        ret++;
+
+        if (trace_event_trigger_enable_disable(file, 1) < 0) {
+                list_del_rcu(&data->list);
+                ret--;
+        }
+out:
+        return ret;
+}
+
+static void event_enable_unregister_trigger(char *glob,
+                                            struct event_trigger_ops *ops,
+                                            struct event_trigger_data *test,
+                                            struct ftrace_event_file *file)
+{
+        struct enable_trigger_data *test_enable_data = test->private_data;
+        struct enable_trigger_data *enable_data;
+        struct event_trigger_data *data;
+        bool unregistered = false;
+
+        list_for_each_entry_rcu(data, &file->triggers, list) {
+                enable_data = data->private_data;
+                if (enable_data &&
+                    (enable_data->file == test_enable_data->file)) {
+                        unregistered = true;
+                        list_del_rcu(&data->list);
+                        trace_event_trigger_enable_disable(file, 0);
+                        break;
+                }
+        }
+
+        if (unregistered && data->ops->free)
+                data->ops->free(data->ops, data);
+}
+
+static struct event_trigger_ops *
+event_enable_get_trigger_ops(char *cmd, char *param)
+{
+        struct event_trigger_ops *ops;
+        bool enable;
+
+        enable = strcmp(cmd, ENABLE_EVENT_STR) == 0;
+
+        if (enable)
+                ops = param ? &event_enable_count_trigger_ops :
+                        &event_enable_trigger_ops;
+        else
+                ops = param ? &event_disable_count_trigger_ops :
+                        &event_disable_trigger_ops;
+
+        return ops;
+}
+
+static struct event_command trigger_enable_cmd = {
+        .name                   = ENABLE_EVENT_STR,
+        .trigger_type           = ETT_EVENT_ENABLE,
+        .func                   = event_enable_trigger_func,
+        .reg                    = event_enable_register_trigger,
+        .unreg                  = event_enable_unregister_trigger,
+        .get_trigger_ops        = event_enable_get_trigger_ops,
+};
+
+static struct event_command trigger_disable_cmd = {
+        .name                   = DISABLE_EVENT_STR,
+        .trigger_type           = ETT_EVENT_ENABLE,
+        .func                   = event_enable_trigger_func,
+        .reg                    = event_enable_register_trigger,
+        .unreg                  = event_enable_unregister_trigger,
+        .get_trigger_ops        = event_enable_get_trigger_ops,
+};
+
+static __init void unregister_trigger_enable_disable_cmds(void)
+{
+        unregister_event_command(&trigger_enable_cmd);
+        unregister_event_command(&trigger_disable_cmd);
+}
+
+static __init int register_trigger_enable_disable_cmds(void)
+{
+        int ret;
+
+        ret = register_event_command(&trigger_enable_cmd);
+        if (WARN_ON(ret < 0))
+                return ret;
+        ret = register_event_command(&trigger_disable_cmd);
+        if (WARN_ON(ret < 0))
+                unregister_trigger_enable_disable_cmds();
+
+        return ret;
+}
+
 static __init int register_trigger_traceon_traceoff_cmds(void)
 {
         int ret;
@@ -883,6 +1241,7 @@ __init int register_trigger_cmds(void)
         register_trigger_traceon_traceoff_cmds();
         register_trigger_snapshot_cmd();
         register_trigger_stacktrace_cmd();
+        register_trigger_enable_disable_cmds();
 
         return 0;
 }