tracing/probes: Add tracepoint support on fprobe_events

Allow fprobe_events to trace raw tracepoints so that user can trace
tracepoints which don't have traceevent wrappers. This new event is
always available if the fprobe_events is enabled (thus no kconfig),
because the fprobe_events depends on the trace-event and traceporint.

e.g.
 # echo 't sched_overutilized_tp' >> dynamic_events
 # echo 't 9p_client_req' >> dynamic_events
 # cat dynamic_events
t:tracepoints/sched_overutilized_tp sched_overutilized_tp
t:tracepoints/_9p_client_req 9p_client_req

The event name is based on the tracepoint name, but if it is started
with digit character, an underscore '_' will be added.

NOTE: to avoid further confusion, this renames TPARG_FL_TPOINT to
TPARG_FL_TEVENT because this flag is used for eprobe (trace-event probe).
And reuse TPARG_FL_TPOINT for this raw tracepoint probe.

Link: https://lore.kernel.org/all/168507471874.913472.17214624519622959593.stgit@mhiramat.roam.corp.google.com/

Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202305020453.afTJ3VVp-lkp@intel.com/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

1 files changed, 127 insertions, 7 deletions

diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 48dbbc72b7dd..aa71ccb4205c 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -9,6 +9,7 @@
 #include <linux/module.h>
 #include <linux/rculist.h>
 #include <linux/security.h>
+#include <linux/tracepoint.h>
 #include <linux/uaccess.h>
 
 #include "trace_dynevent.h"
@@ -17,6 +18,7 @@
 #include "trace_probe_tmpl.h"
 
 #define FPROBE_EVENT_SYSTEM "fprobes"
+#define TRACEPOINT_EVENT_SYSTEM "tracepoints"
 #define RETHOOK_MAXACTIVE_MAX 4096
 
 static int trace_fprobe_create(const char *raw_command);
@@ -41,6 +43,8 @@ struct trace_fprobe {
 	struct dyn_event	devent;
 	struct fprobe		fp;
 	const char		*symbol;
+	struct tracepoint	*tpoint;
+	struct module		*mod;
 	struct trace_probe	tp;
 };
 
@@ -68,6 +72,11 @@ static bool trace_fprobe_is_return(struct trace_fprobe *tf)
 	return tf->fp.exit_handler != NULL;
 }
 
+static bool trace_fprobe_is_tracepoint(struct trace_fprobe *tf)
+{
+	return tf->tpoint != NULL;
+}
+
 static const char *trace_fprobe_symbol(struct trace_fprobe *tf)
 {
 	return tf->symbol ? tf->symbol : "unknown";
@@ -668,6 +677,21 @@ static int __register_trace_fprobe(struct trace_fprobe *tf)
 	else
 		tf->fp.flags |= FPROBE_FL_DISABLED;
 
+	if (trace_fprobe_is_tracepoint(tf)) {
+		struct tracepoint *tpoint = tf->tpoint;
+		unsigned long ip = (unsigned long)tpoint->probestub;
+		/*
+		 * Here, we do 2 steps to enable fprobe on a tracepoint.
+		 * At first, put __probestub_##TP function on the tracepoint
+		 * and put a fprobe on the stub function.
+		 */
+		ret = tracepoint_probe_register_prio_may_exist(tpoint,
+					tpoint->probestub, NULL, 0);
+		if (ret < 0)
+			return ret;
+		return register_fprobe_ips(&tf->fp, &ip, 1);
+	}
+
 	/* TODO: handle filter, nofilter or symbol list */
 	return register_fprobe(&tf->fp, tf->symbol, NULL);
 }
@@ -678,6 +702,12 @@ static void __unregister_trace_fprobe(struct trace_fprobe *tf)
 	if (trace_fprobe_is_registered(tf)) {
 		unregister_fprobe(&tf->fp);
 		memset(&tf->fp, 0, sizeof(tf->fp));
+		if (trace_fprobe_is_tracepoint(tf)) {
+			tracepoint_probe_unregister(tf->tpoint,
+					tf->tpoint->probestub, NULL);
+			tf->tpoint = NULL;
+			tf->mod = NULL;
+		}
 	}
 }
 
@@ -741,7 +771,8 @@ static int append_trace_fprobe(struct trace_fprobe *tf, struct trace_fprobe *to)
 {
 	int ret;
 
-	if (trace_fprobe_is_return(tf) != trace_fprobe_is_return(to)) {
+	if (trace_fprobe_is_return(tf) != trace_fprobe_is_return(to) ||
+	    trace_fprobe_is_tracepoint(tf) != trace_fprobe_is_tracepoint(to)) {
 		trace_probe_log_set_index(0);
 		trace_probe_log_err(0, DIFF_PROBE_TYPE);
 		return -EEXIST;
@@ -811,6 +842,60 @@ end:
 	return ret;
 }
 
+#ifdef CONFIG_MODULES
+static int __tracepoint_probe_module_cb(struct notifier_block *self,
+					unsigned long val, void *data)
+{
+	struct tp_module *tp_mod = data;
+	struct trace_fprobe *tf;
+	struct dyn_event *pos;
+
+	if (val != MODULE_STATE_GOING)
+		return NOTIFY_DONE;
+
+	mutex_lock(&event_mutex);
+	for_each_trace_fprobe(tf, pos) {
+		if (tp_mod->mod == tf->mod) {
+			tracepoint_probe_unregister(tf->tpoint,
+					tf->tpoint->probestub, NULL);
+			tf->tpoint = NULL;
+			tf->mod = NULL;
+		}
+	}
+	mutex_unlock(&event_mutex);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block tracepoint_module_nb = {
+	.notifier_call = __tracepoint_probe_module_cb,
+};
+#endif /* CONFIG_MODULES */
+
+struct __find_tracepoint_cb_data {
+	const char *tp_name;
+	struct tracepoint *tpoint;
+};
+
+static void __find_tracepoint_cb(struct tracepoint *tp, void *priv)
+{
+	struct __find_tracepoint_cb_data *data = priv;
+
+	if (!data->tpoint && !strcmp(data->tp_name, tp->name))
+		data->tpoint = tp;
+}
+
+static struct tracepoint *find_tracepoint(const char *tp_name)
+{
+	struct __find_tracepoint_cb_data data = {
+		.tp_name = tp_name,
+	};
+
+	for_each_kernel_tracepoint(__find_tracepoint_cb, &data);
+
+	return data.tpoint;
+}
+
 static int __trace_fprobe_create(int argc, const char *argv[])
 {
 	/*
@@ -819,6 +904,8 @@ static int __trace_fprobe_create(int argc, const char *argv[])
 	 *      f[:[GRP/][EVENT]] [MOD:]KSYM [FETCHARGS]
 	 *  - Add fexit probe:
 	 *      f[N][:[GRP/][EVENT]] [MOD:]KSYM%return [FETCHARGS]
+	 *  - Add tracepoint probe:
+	 *      t[:[GRP/][EVENT]] TRACEPOINT [FETCHARGS]
 	 *
 	 * Fetch args:
 	 *  $retval	: fetch return value
@@ -844,10 +931,16 @@ static int __trace_fprobe_create(int argc, const char *argv[])
 	char buf[MAX_EVENT_NAME_LEN];
 	char gbuf[MAX_EVENT_NAME_LEN];
 	unsigned int flags = TPARG_FL_KERNEL | TPARG_FL_FPROBE;
+	bool is_tracepoint = false;
 
-	if (argv[0][0] != 'f' || argc < 2)
+	if ((argv[0][0] != 'f' && argv[0][0] != 't') || argc < 2)
 		return -ECANCELED;
 
+	if (argv[0][0] == 't') {
+		is_tracepoint = true;
+		group = TRACEPOINT_EVENT_SYSTEM;
+	}
+
 	trace_probe_log_init("trace_fprobe", argc, argv);
 
 	event = strchr(&argv[0][1], ':');
@@ -881,14 +974,14 @@ static int __trace_fprobe_create(int argc, const char *argv[])
 
 	trace_probe_log_set_index(1);
 
-	/* a symbol specified */
+	/* a symbol(or tracepoint) must be specified */
 	symbol = kstrdup(argv[1], GFP_KERNEL);
 	if (!symbol)
 		return -ENOMEM;
 
 	tmp = strchr(symbol, '%');
 	if (tmp) {
-		if (!strcmp(tmp, "%return")) {
+		if (!is_tracepoint && !strcmp(tmp, "%return")) {
 			*tmp = '\0';
 			is_return = true;
 		} else {
@@ -907,6 +1000,9 @@ static int __trace_fprobe_create(int argc, const char *argv[])
 	else
 		flags |= TPARG_FL_FENTRY;
 
+	if (is_tracepoint)
+		flags |= TPARG_FL_TPOINT;
+
 	trace_probe_log_set_index(0);
 	if (event) {
 		ret = traceprobe_parse_event_name(&event, &group, gbuf,
@@ -917,8 +1013,11 @@ static int __trace_fprobe_create(int argc, const char *argv[])
 
 	if (!event) {
 		/* Make a new event name */
-		snprintf(buf, MAX_EVENT_NAME_LEN, "%s__%s", symbol,
-			 is_return ? "exit" : "entry");
+		if (is_tracepoint)
+			strscpy(buf, symbol, MAX_EVENT_NAME_LEN);
+		else
+			snprintf(buf, MAX_EVENT_NAME_LEN, "%s__%s", symbol,
+				 is_return ? "exit" : "entry");
 		sanitize_event_name(buf);
 		event = buf;
 	}
@@ -932,6 +1031,18 @@ static int __trace_fprobe_create(int argc, const char *argv[])
 		WARN_ON_ONCE(ret != -ENOMEM);
 		goto out;	/* We know tf is not allocated */
 	}
+
+	if (is_tracepoint) {
+		tf->tpoint = find_tracepoint(tf->symbol);
+		if (!tf->tpoint) {
+			trace_probe_log_set_index(1);
+			trace_probe_log_err(0, NO_TRACEPOINT);
+			goto parse_error;
+		}
+		tf->mod = __module_text_address(
+				(unsigned long)tf->tpoint->probestub);
+	}
+
 	argc -= 2; argv += 2;
 
 	/* parse arguments */
@@ -991,7 +1102,10 @@ static int trace_fprobe_show(struct seq_file *m, struct dyn_event *ev)
 	struct trace_fprobe *tf = to_trace_fprobe(ev);
 	int i;
 
-	seq_putc(m, 'f');
+	if (trace_fprobe_is_tracepoint(tf))
+		seq_putc(m, 't');
+	else
+		seq_putc(m, 'f');
 	if (trace_fprobe_is_return(tf) && tf->fp.nr_maxactive)
 		seq_printf(m, "%d", tf->fp.nr_maxactive);
 	seq_printf(m, ":%s/%s", trace_probe_group_name(&tf->tp),
@@ -1048,6 +1162,12 @@ static __init int init_fprobe_trace_early(void)
 	if (ret)
 		return ret;
 
+#ifdef CONFIG_MODULES
+	ret = register_tracepoint_module_notifier(&tracepoint_module_nb);
+	if (ret)
+		return ret;
+#endif
+
 	return 0;
 }
 core_initcall(init_fprobe_trace_early);