Commit 67e9a9ee authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google)
Browse files

tracing/fprobe: Support raw tracepoint events on modules 

Support raw tracepoint event on module by fprobe events.
Since it only uses for_each_kernel_tracepoint() to find a tracepoint,
the tracepoints on modules are not handled. Thus if user specified a
tracepoint on a module, it shows an error.
This adds new for_each_module_tracepoint() API to tracepoint subsystem,
and uses it to find tracepoints on modules.

Link: https://lore.kernel.org/all/172397779651.286558.15903703620679186867.stgit@devnote2/



Reported-by: default avatardon <zds100@gmail.com>
Closes: https://lore.kernel.org/all/20240530215718.aeec973a1d0bf058d39cb1e3@kernel.org/


Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
parent d4df54f3

kernel/trace/trace_fprobe.c

+38 −8
Original line number Diff line number Diff line
@@ -385,6 +385,7 @@ static struct trace_fprobe *alloc_trace_fprobe(const char *group, 
					       const char *event,

					       const char *symbol,

					       struct tracepoint *tpoint,

					       struct module *mod,

					       int maxactive,

					       int nargs, bool is_return)

{
@@ -405,6 +406,7 @@ static struct trace_fprobe *alloc_trace_fprobe(const char *group, 
		tf->fp.entry_handler = fentry_dispatcher;



	tf->tpoint = tpoint;

	tf->mod = mod;

	tf->fp.nr_maxactive = maxactive;



	ret = trace_probe_init(&tf->tp, event, group, false, nargs);
@@ -895,8 +897,23 @@ static struct notifier_block tracepoint_module_nb = { 
struct __find_tracepoint_cb_data {

	const char *tp_name;

	struct tracepoint *tpoint;

	struct module *mod;

};



static void __find_tracepoint_module_cb(struct tracepoint *tp, struct module *mod, void *priv)

{

	struct __find_tracepoint_cb_data *data = priv;



	if (!data->tpoint && !strcmp(data->tp_name, tp->name)) {

		data->tpoint = tp;

		data->mod = mod;

		if (!try_module_get(data->mod)) {

			data->tpoint = NULL;

			data->mod = NULL;

		}

	}

}



static void __find_tracepoint_cb(struct tracepoint *tp, void *priv)

{

	struct __find_tracepoint_cb_data *data = priv;
@@ -905,14 +922,28 @@ static void __find_tracepoint_cb(struct tracepoint *tp, void *priv) 
		data->tpoint = tp;

}



static struct tracepoint *find_tracepoint(const char *tp_name)

/*

 * Find a tracepoint from kernel and module. If the tracepoint is in a module,

 * this increments the module refcount to prevent unloading until the

 * trace_fprobe is registered to the list. After registering the trace_fprobe

 * on the trace_fprobe list, the module refcount is decremented because

 * tracepoint_probe_module_cb will handle it.

 */

static struct tracepoint *find_tracepoint(const char *tp_name,

					  struct module **tp_mod)

{

	struct __find_tracepoint_cb_data data = {

		.tp_name = tp_name,

		.mod = NULL,

	};



	for_each_kernel_tracepoint(__find_tracepoint_cb, &data);



	if (!data.tpoint && IS_ENABLED(CONFIG_MODULES)) {

		for_each_module_tracepoint(__find_tracepoint_module_cb, &data);

		*tp_mod = data.mod;

	}



	return data.tpoint;

}
@@ -996,6 +1027,7 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
	char abuf[MAX_BTF_ARGS_LEN];

	char *dbuf = NULL;

	bool is_tracepoint = false;

	struct module *tp_mod = NULL;

	struct tracepoint *tpoint = NULL;

	struct traceprobe_parse_context ctx = {

		.flags = TPARG_FL_KERNEL | TPARG_FL_FPROBE,
@@ -1080,7 +1112,7 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 


	if (is_tracepoint) {

		ctx.flags |= TPARG_FL_TPOINT;

		tpoint = find_tracepoint(symbol);

		tpoint = find_tracepoint(symbol, &tp_mod);

		if (!tpoint) {

			trace_probe_log_set_index(1);

			trace_probe_log_err(0, NO_TRACEPOINT);
@@ -1110,8 +1142,8 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
		goto out;



	/* setup a probe */

	tf = alloc_trace_fprobe(group, event, symbol, tpoint, maxactive,

				argc, is_return);

	tf = alloc_trace_fprobe(group, event, symbol, tpoint, tp_mod,

				maxactive, argc, is_return);

	if (IS_ERR(tf)) {

		ret = PTR_ERR(tf);

		/* This must return -ENOMEM, else there is a bug */
@@ -1119,10 +1151,6 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
		goto out;	/* We know tf is not allocated */

	}



	if (is_tracepoint)

		tf->mod = __module_text_address(

				(unsigned long)tf->tpoint->probestub);



	/* parse arguments */

	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {

		trace_probe_log_set_index(i + 2);
@@ -1155,6 +1183,8 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
	}



out:

	if (tp_mod)

		module_put(tp_mod);

	traceprobe_finish_parse(&ctx);

	trace_probe_log_clear();

	kfree(new_argv);