1 files changed, 37 insertions, 0 deletions

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 8f58ee1e8858..424751cdf31f 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -154,9 +154,12 @@ fail:
 }
 
 static struct trace_probe_log trace_probe_log;
+extern struct mutex dyn_event_ops_mutex;
 
 void trace_probe_log_init(const char *subsystem, int argc, const char **argv)
 {
+	lockdep_assert_held(&dyn_event_ops_mutex);
+
 	trace_probe_log.subsystem = subsystem;
 	trace_probe_log.argc = argc;
 	trace_probe_log.argv = argv;
@@ -165,11 +168,15 @@ void trace_probe_log_init(const char *subsystem, int argc, const char **argv)
 
 void trace_probe_log_clear(void)
 {
+	lockdep_assert_held(&dyn_event_ops_mutex);
+
 	memset(&trace_probe_log, 0, sizeof(trace_probe_log));
 }
 
 void trace_probe_log_set_index(int index)
 {
+	lockdep_assert_held(&dyn_event_ops_mutex);
+
 	trace_probe_log.index = index;
 }
 
@@ -178,6 +185,8 @@ void __trace_probe_log_err(int offset, int err_type)
 	char *command, *p;
 	int i, len = 0, pos = 0;
 
+	lockdep_assert_held(&dyn_event_ops_mutex);
+
 	if (!trace_probe_log.argv)
 		return;
 
@@ -770,6 +779,10 @@ static int check_prepare_btf_string_fetch(char *typename,
 
 #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
 
+/*
+ * Add the entry code to store the 'argnum'th parameter and return the offset
+ * in the entry data buffer where the data will be stored.
+ */
 static int __store_entry_arg(struct trace_probe *tp, int argnum)
 {
 	struct probe_entry_arg *earg = tp->entry_arg;
@@ -793,6 +806,20 @@ static int __store_entry_arg(struct trace_probe *tp, int argnum)
 		tp->entry_arg = earg;
 	}
 
+	/*
+	 * The entry code array is repeating the pair of
+	 * [FETCH_OP_ARG(argnum)][FETCH_OP_ST_EDATA(offset of entry data buffer)]
+	 * and the rest of entries are filled with [FETCH_OP_END].
+	 *
+	 * To reduce the redundant function parameter fetching, we scan the entry
+	 * code array to find the FETCH_OP_ARG which already fetches the 'argnum'
+	 * parameter. If it doesn't match, update 'offset' to find the last
+	 * offset.
+	 * If we find the FETCH_OP_END without matching FETCH_OP_ARG entry, we
+	 * will save the entry with FETCH_OP_ARG and FETCH_OP_ST_EDATA, and
+	 * return data offset so that caller can find the data offset in the entry
+	 * data buffer.
+	 */
 	offset = 0;
 	for (i = 0; i < earg->size - 1; i++) {
 		switch (earg->code[i].op) {
@@ -826,6 +853,16 @@ int traceprobe_get_entry_data_size(struct trace_probe *tp)
 	if (!earg)
 		return 0;
 
+	/*
+	 * earg->code[] array has an operation sequence which is run in
+	 * the entry handler.
+	 * The sequence stopped by FETCH_OP_END and each data stored in
+	 * the entry data buffer by FETCH_OP_ST_EDATA. The FETCH_OP_ST_EDATA
+	 * stores the data at the data buffer + its offset, and all data are
+	 * "unsigned long" size. The offset must be increased when a data is
+	 * stored. Thus we need to find the last FETCH_OP_ST_EDATA in the
+	 * code array.
+	 */
 	for (i = 0; i < earg->size; i++) {
 		switch (earg->code[i].op) {
 		case FETCH_OP_END: