To audit active event triggers, userspace currently must traverse the events/ directory and read each individual trigger file. This is cumbersome for system-wide auditing or debugging.
Introduce "show_event_triggers" at the trace root directory. This file displays all events that currently have one or more triggers applied, alongside the trigger configuration, in a consolidated system:event [tab] trigger format. The implementation leverages the existing trace_event_file iterators and uses the trigger's own print() operation to ensure output consistency with the per-event trigger files. Signed-off-by: Aaron Tomlin <[email protected]> --- Documentation/trace/ftrace.rst | 8 +++++ kernel/trace/trace_events.c | 64 ++++++++++++++++++++++++++++++++++ 2 files changed, 72 insertions(+) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 4ce01e726b09..b9efb148a5c2 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -692,6 +692,14 @@ of ftrace. Here is a list of some of the key files: See events.rst for more information. + show_event_triggers: + + A list of events that have triggers. This shows the + system/event pair along with the trigger that is attached to + the event. + + See events.rst for more information. + available_events: A list of events that can be enabled in tracing. diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 5ede4214c4df..e2a67561253d 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -1687,6 +1687,38 @@ static int t_show_filters(struct seq_file *m, void *v) return 0; } +/** + * t_show_triggers - seq_file callback to display active event triggers + * @m: The seq_file interface for formatted output + * @v: The current trace_event_file being iterated + * + * Iterates through the trigger list of the current event file and prints + * each active trigger's configuration using its associated print + * operation. + */ +static int t_show_triggers(struct seq_file *m, void *v) +{ + struct trace_event_file *file = v; + struct trace_event_call *call = file->event_call; + struct event_trigger_data *data; + + /* + * The event_mutex is held by t_start(), protecting the + * file->triggers list traversal. + */ + if (list_empty(&file->triggers)) + return 0; + + list_for_each_entry_rcu(data, &file->triggers, list) { + seq_printf(m, "%s:%s\t", call->class->system, + trace_event_name(call)); + + data->cmd_ops->print(m, data); + } + + return 0; +} + #ifdef CONFIG_MODULES static int s_show(struct seq_file *m, void *v) { @@ -2515,6 +2547,7 @@ ftrace_event_npid_write(struct file *filp, const char __user *ubuf, static int ftrace_event_avail_open(struct inode *inode, struct file *file); static int ftrace_event_set_open(struct inode *inode, struct file *file); static int ftrace_event_show_filters_open(struct inode *inode, struct file *file); +static int ftrace_event_show_triggers_open(struct inode *inode, struct file *file); static int ftrace_event_set_pid_open(struct inode *inode, struct file *file); static int ftrace_event_set_npid_open(struct inode *inode, struct file *file); static int ftrace_event_release(struct inode *inode, struct file *file); @@ -2540,6 +2573,13 @@ static const struct seq_operations show_show_event_filters_seq_ops = { .stop = t_stop, }; +static const struct seq_operations show_show_event_triggers_seq_ops = { + .start = t_start, + .next = t_next, + .show = t_show_triggers, + .stop = t_stop, +}; + static const struct seq_operations show_set_pid_seq_ops = { .start = p_start, .next = p_next, @@ -2576,6 +2616,13 @@ static const struct file_operations ftrace_show_event_filters_fops = { .release = seq_release, }; +static const struct file_operations ftrace_show_event_triggers_fops = { + .open = ftrace_event_show_triggers_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, +}; + static const struct file_operations ftrace_set_event_pid_fops = { .open = ftrace_event_set_pid_open, .read = seq_read, @@ -2734,6 +2781,20 @@ ftrace_event_show_filters_open(struct inode *inode, struct file *file) return ftrace_event_open(inode, file, &show_show_event_filters_seq_ops); } +/** + * ftrace_event_show_triggers_open - open interface for show_event_triggers + * @inode: The inode of the file + * @file: The file being opened + * + * Connects the show_event_triggers file to the sequence operations + * required to iterate over and display active event triggers. + */ +static int +ftrace_event_show_triggers_open(struct inode *inode, struct file *file) +{ + return ftrace_event_open(inode, file, &show_show_event_triggers_seq_ops); +} + static int ftrace_event_set_pid_open(struct inode *inode, struct file *file) { @@ -4457,6 +4518,9 @@ create_event_toplevel_files(struct dentry *parent, struct trace_array *tr) trace_create_file("show_event_filters", TRACE_MODE_READ, parent, tr, &ftrace_show_event_filters_fops); + trace_create_file("show_event_triggers", TRACE_MODE_READ, parent, tr, + &ftrace_show_event_triggers_fops); + nr_entries = ARRAY_SIZE(events_entries); e_events = eventfs_create_events_dir("events", parent, events_entries, -- 2.51.0
