tracing: Add 'traceon' and 'traceoff' event trigger commands

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

    echo 'traceon' > .../tracing/events/somesys/someevent/trigger
    echo 'traceoff' > .../tracing/events/somesys/someevent/trigger

The above command will turn tracing on or off whenever someevent is
hit.

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

    echo 'traceon:N' > .../tracing/events/somesys/someevent/trigger
    echo 'traceoff:N' > .../tracing/events/somesys/someevent/trigger

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

The above commands will will turn tracing on or off whenever someevent
is hit, but only N times.

Some common register/unregister_trigger() implementations of the
event_command reg()/unreg() callbacks are also provided, which add and
remove trigger instances to the per-event list of triggers, and
arm/disarm them as appropriate.  event_trigger_callback() is a
general-purpose event_command func() implementation that orchestrates
command parsing and registration for most normal commands.

Most event commands will use these, but some will override and
possibly reuse them.

The event_trigger_init(), event_trigger_free(), and
event_trigger_print() functions are meant to be common implementations
of the event_trigger_ops init(), free(), and print() ops,
respectively.

Most trigger_ops implementations will use these, but some will
override and possibly reuse them.

Link: http://lkml.kernel.org/r/00a52816703b98d2072947478dd6e2d70cde5197.1382622043.git.tom.zanussi@linux.intel.com

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

1 files changed, 446 insertions, 0 deletions

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 60a6a6d66dc0..4ea72ee169a7 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -28,6 +28,13 @@
 static LIST_HEAD(trigger_commands);
 static DEFINE_MUTEX(trigger_cmd_mutex);
 
+static void
+trigger_data_free(struct event_trigger_data *data)
+{
+        synchronize_sched(); /* make sure current triggers exit before free */
+        kfree(data);
+}
+
 /**
  * event_triggers_call - Call triggers associated with a trace event
  * @file: The ftrace_event_file associated with the event
@@ -224,6 +231,129 @@ const struct file_operations event_trigger_fops = {
         .release = event_trigger_release,
 };
 
+/*
+ * Currently we only register event commands from __init, so mark this
+ * __init too.
+ */
+static __init int register_event_command(struct event_command *cmd)
+{
+        struct event_command *p;
+        int ret = 0;
+
+        mutex_lock(&trigger_cmd_mutex);
+        list_for_each_entry(p, &trigger_commands, list) {
+                if (strcmp(cmd->name, p->name) == 0) {
+                        ret = -EBUSY;
+                        goto out_unlock;
+                }
+        }
+        list_add(&cmd->list, &trigger_commands);
+ out_unlock:
+        mutex_unlock(&trigger_cmd_mutex);
+
+        return ret;
+}
+
+/*
+ * Currently we only unregister event commands from __init, so mark
+ * this __init too.
+ */
+static __init int unregister_event_command(struct event_command *cmd)
+{
+        struct event_command *p, *n;
+        int ret = -ENODEV;
+
+        mutex_lock(&trigger_cmd_mutex);
+        list_for_each_entry_safe(p, n, &trigger_commands, list) {
+                if (strcmp(cmd->name, p->name) == 0) {
+                        ret = 0;
+                        list_del_init(&p->list);
+                        goto out_unlock;
+                }
+        }
+ out_unlock:
+        mutex_unlock(&trigger_cmd_mutex);
+
+        return ret;
+}
+
+/**
+ * event_trigger_print - Generic event_trigger_ops @print implementation
+ * @name: The name of the event trigger
+ * @m: The seq_file being printed to
+ * @data: Trigger-specific data
+ * @filter_str: filter_str to print, if present
+ *
+ * Common implementation for event triggers to print themselves.
+ *
+ * Usually wrapped by a function that simply sets the @name of the
+ * trigger command and then invokes this.
+ *
+ * Return: 0 on success, errno otherwise
+ */
+static int
+event_trigger_print(const char *name, struct seq_file *m,
+                    void *data, char *filter_str)
+{
+        long count = (long)data;
+
+        seq_printf(m, "%s", name);
+
+        if (count == -1)
+                seq_puts(m, ":unlimited");
+        else
+                seq_printf(m, ":count=%ld", count);
+
+        if (filter_str)
+                seq_printf(m, " if %s\n", filter_str);
+        else
+                seq_puts(m, "\n");
+
+        return 0;
+}
+
+/**
+ * event_trigger_init - Generic event_trigger_ops @init implementation
+ * @ops: The trigger ops associated with the trigger
+ * @data: Trigger-specific data
+ *
+ * Common implementation of event trigger initialization.
+ *
+ * Usually used directly as the @init method in event trigger
+ * implementations.
+ *
+ * Return: 0 on success, errno otherwise
+ */
+static int
+event_trigger_init(struct event_trigger_ops *ops,
+                   struct event_trigger_data *data)
+{
+        data->ref++;
+        return 0;
+}
+
+/**
+ * event_trigger_free - Generic event_trigger_ops @free implementation
+ * @ops: The trigger ops associated with the trigger
+ * @data: Trigger-specific data
+ *
+ * Common implementation of event trigger de-initialization.
+ *
+ * Usually used directly as the @free method in event trigger
+ * implementations.
+ */
+static void
+event_trigger_free(struct event_trigger_ops *ops,
+                   struct event_trigger_data *data)
+{
+        if (WARN_ON_ONCE(data->ref <= 0))
+                return;
+
+        data->ref--;
+        if (!data->ref)
+                trigger_data_free(data);
+}
+
 static int trace_event_trigger_enable_disable(struct ftrace_event_file *file,
                                               int trigger_enable)
 {
@@ -272,7 +402,323 @@ clear_event_triggers(struct trace_array *tr)
         }
 }
 
+/**
+ * register_trigger - Generic event_command @reg implementation
+ * @glob: The raw string used to register the trigger
+ * @ops: The trigger ops associated with the trigger
+ * @data: Trigger-specific data to associate with the trigger
+ * @file: The ftrace_event_file associated with the event
+ *
+ * Common implementation for event trigger registration.
+ *
+ * Usually used directly as the @reg method in event command
+ * implementations.
+ *
+ * Return: 0 on success, errno otherwise
+ */
+static int register_trigger(char *glob, struct event_trigger_ops *ops,
+                            struct event_trigger_data *data,
+                            struct ftrace_event_file *file)
+{
+        struct event_trigger_data *test;
+        int ret = 0;
+
+        list_for_each_entry_rcu(test, &file->triggers, list) {
+                if (test->cmd_ops->trigger_type == data->cmd_ops->trigger_type) {
+                        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;
+}
+
+/**
+ * unregister_trigger - Generic event_command @unreg implementation
+ * @glob: The raw string used to register the trigger
+ * @ops: The trigger ops associated with the trigger
+ * @test: Trigger-specific data used to find the trigger to remove
+ * @file: The ftrace_event_file associated with the event
+ *
+ * Common implementation for event trigger unregistration.
+ *
+ * Usually used directly as the @unreg method in event command
+ * implementations.
+ */
+static void unregister_trigger(char *glob, struct event_trigger_ops *ops,
+                               struct event_trigger_data *test,
+                               struct ftrace_event_file *file)
+{
+        struct event_trigger_data *data;
+        bool unregistered = false;
+
+        list_for_each_entry_rcu(data, &file->triggers, list) {
+                if (data->cmd_ops->trigger_type == test->cmd_ops->trigger_type) {
+                        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);
+}
+
+/**
+ * event_trigger_callback - Generic event_command @func implementation
+ * @cmd_ops: The command ops, used for trigger registration
+ * @file: The ftrace_event_file associated with the event
+ * @glob: The raw string used to register the trigger
+ * @cmd: The cmd portion of the string used to register the trigger
+ * @param: The params portion of the string used to register the trigger
+ *
+ * Common implementation for event command parsing and trigger
+ * instantiation.
+ *
+ * Usually used directly as the @func method in event command
+ * implementations.
+ *
+ * Return: 0 on success, errno otherwise
+ */
+static int
+event_trigger_callback(struct event_command *cmd_ops,
+                       struct ftrace_event_file *file,
+                       char *glob, char *cmd, char *param)
+{
+        struct event_trigger_data *trigger_data;
+        struct event_trigger_ops *trigger_ops;
+        char *trigger = NULL;
+        char *number;
+        int ret;
+
+        /* separate the trigger from the filter (t:n [if filter]) */
+        if (param && isdigit(param[0]))
+                trigger = strsep(&param, " \t");
+
+        trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);
+
+        ret = -ENOMEM;
+        trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
+        if (!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);
+
+        if (glob[0] == '!') {
+                cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
+                kfree(trigger_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:
+        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_free;
+        } else if (ret < 0)
+                goto out_free;
+        ret = 0;
+ out:
+        return ret;
+
+ out_free:
+        kfree(trigger_data);
+        goto out;
+}
+
+static void
+traceon_trigger(struct event_trigger_data *data)
+{
+        if (tracing_is_on())
+                return;
+
+        tracing_on();
+}
+
+static void
+traceon_count_trigger(struct event_trigger_data *data)
+{
+        if (!data->count)
+                return;
+
+        if (data->count != -1)
+                (data->count)--;
+
+        traceon_trigger(data);
+}
+
+static void
+traceoff_trigger(struct event_trigger_data *data)
+{
+        if (!tracing_is_on())
+                return;
+
+        tracing_off();
+}
+
+static void
+traceoff_count_trigger(struct event_trigger_data *data)
+{
+        if (!data->count)
+                return;
+
+        if (data->count != -1)
+                (data->count)--;
+
+        traceoff_trigger(data);
+}
+
+static int
+traceon_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
+                      struct event_trigger_data *data)
+{
+        return event_trigger_print("traceon", m, (void *)data->count,
+                                   data->filter_str);
+}
+
+static int
+traceoff_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
+                       struct event_trigger_data *data)
+{
+        return event_trigger_print("traceoff", m, (void *)data->count,
+                                   data->filter_str);
+}
+
+static struct event_trigger_ops traceon_trigger_ops = {
+        .func                   = traceon_trigger,
+        .print                  = traceon_trigger_print,
+        .init                   = event_trigger_init,
+        .free                   = event_trigger_free,
+};
+
+static struct event_trigger_ops traceon_count_trigger_ops = {
+        .func                   = traceon_count_trigger,
+        .print                  = traceon_trigger_print,
+        .init                   = event_trigger_init,
+        .free                   = event_trigger_free,
+};
+
+static struct event_trigger_ops traceoff_trigger_ops = {
+        .func                   = traceoff_trigger,
+        .print                  = traceoff_trigger_print,
+        .init                   = event_trigger_init,
+        .free                   = event_trigger_free,
+};
+
+static struct event_trigger_ops traceoff_count_trigger_ops = {
+        .func                   = traceoff_count_trigger,
+        .print                  = traceoff_trigger_print,
+        .init                   = event_trigger_init,
+        .free                   = event_trigger_free,
+};
+
+static struct event_trigger_ops *
+onoff_get_trigger_ops(char *cmd, char *param)
+{
+        struct event_trigger_ops *ops;
+
+        /* we register both traceon and traceoff to this callback */
+        if (strcmp(cmd, "traceon") == 0)
+                ops = param ? &traceon_count_trigger_ops :
+                        &traceon_trigger_ops;
+        else
+                ops = param ? &traceoff_count_trigger_ops :
+                        &traceoff_trigger_ops;
+
+        return ops;
+}
+
+static struct event_command trigger_traceon_cmd = {
+        .name                   = "traceon",
+        .trigger_type           = ETT_TRACE_ONOFF,
+        .func                   = event_trigger_callback,
+        .reg                    = register_trigger,
+        .unreg                  = unregister_trigger,
+        .get_trigger_ops        = onoff_get_trigger_ops,
+};
+
+static struct event_command trigger_traceoff_cmd = {
+        .name                   = "traceoff",
+        .trigger_type           = ETT_TRACE_ONOFF,
+        .func                   = event_trigger_callback,
+        .reg                    = register_trigger,
+        .unreg                  = unregister_trigger,
+        .get_trigger_ops        = onoff_get_trigger_ops,
+};
+
+static __init void unregister_trigger_traceon_traceoff_cmds(void)
+{
+        unregister_event_command(&trigger_traceon_cmd);
+        unregister_event_command(&trigger_traceoff_cmd);
+}
+
+static __init int register_trigger_traceon_traceoff_cmds(void)
+{
+        int ret;
+
+        ret = register_event_command(&trigger_traceon_cmd);
+        if (WARN_ON(ret < 0))
+                return ret;
+        ret = register_event_command(&trigger_traceoff_cmd);
+        if (WARN_ON(ret < 0))
+                unregister_trigger_traceon_traceoff_cmds();
+
+        return ret;
+}
+
 __init int register_trigger_cmds(void)
 {
+        register_trigger_traceon_traceoff_cmds();
+
         return 0;
 }