tracing: Add :mod: command to enabled module events

Add a :mod: command to enable only events from a given module from the
set_events file.

  echo '*:mod:<module>' > set_events

Or

  echo ':mod:<module>' > set_events

Will enable all events for that module. Specific events can also be
enabled via:

  echo '<event>:mod:<module>' > set_events

Or

  echo '<system>:<event>:mod:<module>' > set_events

Or

  echo '*:<event>:mod:<module>' > set_events

The ":mod:" keyword is consistent with the function tracing filter to
enable functions from a given module.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/20250116143533.214496360@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst
index 759907c20e7591ce3f03ac191cbc14a29b242f8a..3db57516eb861d41975145aeee4e329bfe84d483 100644 (file)
--- a/Documentation/trace/events.rst
+++ b/Documentation/trace/events.rst
@@ -55,6 +55,28 @@ command::
 
        # echo 'irq:*' > /sys/kernel/tracing/set_event
 
+The set_event file may also be used to enable events associated to only
+a specific module::
+
+       # echo ':mod:<module>' > /sys/kernel/tracing/set_event
+
+Will enable all events in the module ``<module>``.
+
+The text before ``:mod:`` will be parsed to specify specific events that the
+module creates::
+
+       # echo '<match>:mod:<module>' > /sys/kernel/tracing/set_event
+
+The above will enable any system or event that ``<match>`` matches. If
+``<match>`` is ``"*"`` then it will match all events.
+
+To enable only a specific event within a system::
+
+       # echo '<system>:<event>:mod:<module>' > /sys/kernel/tracing/set_event
+
+If ``<event>`` is ``"*"`` then it will match all events within the system
+for a given module.
+
 2.2 Via the 'enable' toggle
 ---------------------------
 

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5aeb898054e7a32feac19e116f406483addcf02b..cb85ee4a88076b34d91fe2952990af1cc86d37c1 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5514,6 +5514,8 @@ static const char readme_msg[] =
        "\t    efield: For event probes ('e' types), the field is on of the fields\n"
        "\t            of the <attached-group>/<attached-event>.\n"
 #endif
+       "  set_event\t\t- Enables events by name written into it\n"
+       "\t\t\t  Can enable module events via: :mod:<module>\n"
        "  events/\t\t- Directory containing all trace event subsystems:\n"
        "      enable\t\t- Write 0/1 to enable/disable tracing of all events\n"
        "  events/<system>/\t- Directory containing all trace events for <system>:\n"

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 2b9222e7bd5a53e7bbab680f56e740cc359bef4d..5c7d0e07618d76ead8b3c5e0504bbd30a8fb12e2 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1153,17 +1153,36 @@ static void remove_event_file_dir(struct trace_event_file *file)
  */
 static int
 __ftrace_set_clr_event_nolock(struct trace_array *tr, const char *match,
-                             const char *sub, const char *event, int set)
+                             const char *sub, const char *event, int set,
+                             const char *mod)
 {
        struct trace_event_file *file;
        struct trace_event_call *call;
+       char *module __free(kfree) = NULL;
        const char *name;
        int ret = -EINVAL;
        int eret = 0;
 
+       if (mod) {
+               char *p;
+
+               module = kstrdup(mod, GFP_KERNEL);
+               if (!module)
+                       return -ENOMEM;
+
+               /* Replace all '-' with '_' as that's what modules do */
+               for (p = strchr(module, '-'); p; p = strchr(p + 1, '-'))
+                       *p = '_';
+       }
+
        list_for_each_entry(file, &tr->events, list) {
 
                call = file->event_call;
+
+               /* If a module is specified, skip events that are not that module */
+               if (module && (!call->module || strcmp(module_name(call->module), module)))
+                       continue;
+
                name = trace_event_name(call);
 
                if (!name || !call->class || !call->class->reg)
@@ -1200,12 +1219,13 @@ __ftrace_set_clr_event_nolock(struct trace_array *tr, const char *match,
 }
 
 static int __ftrace_set_clr_event(struct trace_array *tr, const char *match,
-                                 const char *sub, const char *event, int set)
+                                 const char *sub, const char *event, int set,
+                                 const char *mod)
 {
        int ret;
 
        mutex_lock(&event_mutex);
-       ret = __ftrace_set_clr_event_nolock(tr, match, sub, event, set);
+       ret = __ftrace_set_clr_event_nolock(tr, match, sub, event, set, mod);
        mutex_unlock(&event_mutex);
 
        return ret;
@@ -1213,11 +1233,20 @@ static int __ftrace_set_clr_event(struct trace_array *tr, const char *match,
 
 int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set)
 {
-       char *event = NULL, *sub = NULL, *match;
+       char *event = NULL, *sub = NULL, *match, *mod;
        int ret;
 
        if (!tr)
                return -ENOENT;
+
+       /* Modules events can be appened with :mod:<module> */
+       mod = strstr(buf, ":mod:");
+       if (mod) {
+               *mod = '\0';
+               /* move to the module name */
+               mod += 5;
+       }
+
        /*
         * The buf format can be <subsystem>:<event-name>
         *  *:<event-name> means any event by that name.
@@ -1240,9 +1269,13 @@ int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set)
                        sub = NULL;
                if (!strlen(event) || strcmp(event, "*") == 0)
                        event = NULL;
+       } else if (mod) {
+               /* Allow wildcard for no length or star */
+               if (!strlen(match) || strcmp(match, "*") == 0)
+                       match = NULL;
        }
 
-       ret = __ftrace_set_clr_event(tr, match, sub, event, set);
+       ret = __ftrace_set_clr_event(tr, match, sub, event, set, mod);
 
        /* Put back the colon to allow this to be called again */
        if (buf)
@@ -1270,7 +1303,7 @@ int trace_set_clr_event(const char *system, const char *event, int set)
        if (!tr)
                return -ENODEV;
 
-       return __ftrace_set_clr_event(tr, NULL, system, event, set);
+       return __ftrace_set_clr_event(tr, NULL, system, event, set, NULL);
 }
 EXPORT_SYMBOL_GPL(trace_set_clr_event);
 
@@ -1296,7 +1329,7 @@ int trace_array_set_clr_event(struct trace_array *tr, const char *system,
                return -ENOENT;
 
        set = (enable == true) ? 1 : 0;
-       return __ftrace_set_clr_event(tr, NULL, system, event, set);
+       return __ftrace_set_clr_event(tr, NULL, system, event, set, NULL);
 }
 EXPORT_SYMBOL_GPL(trace_array_set_clr_event);
 
@@ -1646,7 +1679,7 @@ system_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
        if (system)
                name = system->name;
 
-       ret = __ftrace_set_clr_event(dir->tr, NULL, name, NULL, val);
+       ret = __ftrace_set_clr_event(dir->tr, NULL, name, NULL, val, NULL);
        if (ret)
                goto out;
 
@@ -4094,7 +4127,7 @@ int event_trace_del_tracer(struct trace_array *tr)
        __ftrace_clear_event_pids(tr, TRACE_PIDS | TRACE_NO_PIDS);
 
        /* Disable any running events */
-       __ftrace_set_clr_event_nolock(tr, NULL, NULL, NULL, 0);
+       __ftrace_set_clr_event_nolock(tr, NULL, NULL, NULL, 0, NULL);
 
        /* Make sure no more events are being executed */
        tracepoint_synchronize_unregister();
@@ -4378,7 +4411,7 @@ static __init void event_trace_self_tests(void)
 
                pr_info("Testing event system %s: ", system->name);
 
-               ret = __ftrace_set_clr_event(tr, NULL, system->name, NULL, 1);
+               ret = __ftrace_set_clr_event(tr, NULL, system->name, NULL, 1, NULL);
                if (WARN_ON_ONCE(ret)) {
                        pr_warn("error enabling system %s\n",
                                system->name);
@@ -4387,7 +4420,7 @@ static __init void event_trace_self_tests(void)
 
                event_test_stuff();
 
-               ret = __ftrace_set_clr_event(tr, NULL, system->name, NULL, 0);
+               ret = __ftrace_set_clr_event(tr, NULL, system->name, NULL, 0, NULL);
                if (WARN_ON_ONCE(ret)) {
                        pr_warn("error disabling system %s\n",
                                system->name);
@@ -4402,7 +4435,7 @@ static __init void event_trace_self_tests(void)
        pr_info("Running tests on all trace events:\n");
        pr_info("Testing all events: ");
 
-       ret = __ftrace_set_clr_event(tr, NULL, NULL, NULL, 1);
+       ret = __ftrace_set_clr_event(tr, NULL, NULL, NULL, 1, NULL);
        if (WARN_ON_ONCE(ret)) {
                pr_warn("error enabling all events\n");
                return;
@@ -4411,7 +4444,7 @@ static __init void event_trace_self_tests(void)
        event_test_stuff();
 
        /* reset sysname */
-       ret = __ftrace_set_clr_event(tr, NULL, NULL, NULL, 0);
+       ret = __ftrace_set_clr_event(tr, NULL, NULL, NULL, 0, NULL);
        if (WARN_ON_ONCE(ret)) {
                pr_warn("error disabling all events\n");
                return;