tracing/probes: Move event parameter fetching code to common parser

Move trace event parameter fetching code to common parser in
trace_probe.c. This simplifies eprobe's trace-event variable fetching
code by introducing a parse context data structure.

Link: https://lore.kernel.org/all/168507472950.913472.2812253181558471278.stgit@mhiramat.roam.corp.google.com/Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

kernel/trace/trace_eprobe.c

@@ -227,37 +227,6 @@ static struct trace_eprobe *alloc_event_probe(const char *group,
 	return ERR_PTR(ret);
 }
 
-static int trace_eprobe_tp_arg_update(struct trace_eprobe *ep, int i)
-{
-	struct probe_arg *parg = &ep->tp.args[i];
-	struct ftrace_event_field *field;
-	struct list_head *head;
-	int ret = -ENOENT;
-
-	head = trace_get_fields(ep->event);
-	list_for_each_entry(field, head, link) {
-		if (!strcmp(parg->code->data, field->name)) {
-			kfree(parg->code->data);
-			parg->code->data = field;
-			return 0;
-		}
-	}
-
-	/*
-	 * Argument not found on event. But allow for comm and COMM
-	 * to be used to get the current->comm.
-	 */
-	if (strcmp(parg->code->data, "COMM") == 0 ||
-	    strcmp(parg->code->data, "comm") == 0) {
-		parg->code->op = FETCH_OP_COMM;
-		ret = 0;
-	}
-
-	kfree(parg->code->data);
-	parg->code->data = NULL;
-	return ret;
-}
-
 static int eprobe_event_define_fields(struct trace_event_call *event_call)
 {
 	struct eprobe_trace_entry_head field;
@@ -817,19 +786,16 @@ find_and_get_event(const char *system, const char *event_name)
 
 static int trace_eprobe_tp_update_arg(struct trace_eprobe *ep, const char *argv[], int i)
 {
-	unsigned int flags = TPARG_FL_KERNEL | TPARG_FL_TEVENT;
+	struct traceprobe_parse_context ctx = {
+		.event = ep->event,
+		.flags = TPARG_FL_KERNEL | TPARG_FL_TEVENT,
+	};
 	int ret;
 
-	ret = traceprobe_parse_probe_arg(&ep->tp, i, argv[i], flags);
+	ret = traceprobe_parse_probe_arg(&ep->tp, i, argv[i], &ctx);
 	if (ret)
 		return ret;
 
-	if (ep->tp.args[i].code->op == FETCH_OP_TP_ARG) {
-		ret = trace_eprobe_tp_arg_update(ep, i);
-		if (ret)
-			trace_probe_log_err(0, BAD_ATTACH_ARG);
-	}
-
 	/* Handle symbols "@" */
 	if (!ret)
 		ret = traceprobe_update_arg(&ep->tp.args[i]);

kernel/trace/trace_fprobe.c

@@ -1047,8 +1047,10 @@ static int __trace_fprobe_create(int argc, const char *argv[])
 
 	/* parse arguments */
 	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
+		struct traceprobe_parse_context ctx = { .flags = flags };
+
 		trace_probe_log_set_index(i + 2);
-		ret = traceprobe_parse_probe_arg(&tf->tp, i, argv[i], flags);
+		ret = traceprobe_parse_probe_arg(&tf->tp, i, argv[i], &ctx);
 		if (ret)
 			goto error;	/* This can be -ENOMEM */
 	}

kernel/trace/trace_kprobe.c

@@ -867,8 +867,10 @@ static int __trace_kprobe_create(int argc, const char *argv[])
 
 	/* parse arguments */
 	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
+		struct traceprobe_parse_context ctx = { .flags = flags };
+
 		trace_probe_log_set_index(i + 2);
-		ret = traceprobe_parse_probe_arg(&tk->tp, i, argv[i], flags);
+		ret = traceprobe_parse_probe_arg(&tk->tp, i, argv[i], &ctx);
 		if (ret)
 			goto error;	/* This can be -ENOMEM */
 	}

kernel/trace/trace_probe.h

@@ -378,8 +378,15 @@ static inline bool tparg_is_function_entry(unsigned int flags)
 	return (flags & TPARG_FL_LOC_MASK) == (TPARG_FL_KERNEL | TPARG_FL_FENTRY);
 }
 
+struct traceprobe_parse_context {
+	struct trace_event_call *event;
+	unsigned int flags;
+	int offset;
+};
+
 extern int traceprobe_parse_probe_arg(struct trace_probe *tp, int i,
-				const char *argv, unsigned int flags);
+				      const char *argv,
+				      struct traceprobe_parse_context *ctx);
 
 extern int traceprobe_update_arg(struct probe_arg *arg);
 extern void traceprobe_free_probe_arg(struct probe_arg *arg);

kernel/trace/trace_uprobe.c

@@ -686,10 +686,12 @@ static int __trace_uprobe_create(int argc, const char **argv)
 
 	/* parse arguments */
 	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
+		struct traceprobe_parse_context ctx = {
+			.flags = (is_return ? TPARG_FL_RETURN : 0) | TPARG_FL_USER,
+		};
+
 		trace_probe_log_set_index(i + 2);
-		ret = traceprobe_parse_probe_arg(&tu->tp, i, argv[i],
-					(is_return ? TPARG_FL_RETURN : 0) |
-					TPARG_FL_USER);
+		ret = traceprobe_parse_probe_arg(&tu->tp, i, argv[i], &ctx);
 		if (ret)
 			goto error;
 	}