ftrace: Add support to resolve module symbols in ftrace_lookup_symbols

Currently ftrace_lookup_symbols iterates only over core symbols,
adding module_kallsyms_on_each_symbol call to check on modules
symbols as well.

Also removing 'args.found == args.cnt' condition, because it's
already checked in kallsyms_callback function.

Also removing 'err < 0' check, because both *kallsyms_on_each_symbol
functions do not return error.

Reported-by: Martynas Pumputis <[email protected]>
Acked-by: Song Liu <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

kernel/trace/ftrace.c

@@ -8267,6 +8267,10 @@ struct kallsyms_data {
 	size_t found;
 };
 
+/* This function gets called for all kernel and module symbols
+ * and returns 1 in case we resolved all the requested symbols,
+ * 0 otherwise.
+ */
 static int kallsyms_callback(void *data, const char *name,
 			     struct module *mod, unsigned long addr)
 {
@@ -8309,17 +8313,19 @@ static int kallsyms_callback(void *data, const char *name,
 int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs)
 {
 	struct kallsyms_data args;
-	int err;
+	int found_all;
 
 	memset(addrs, 0, sizeof(*addrs) * cnt);
 	args.addrs = addrs;
 	args.syms = sorted_syms;
 	args.cnt = cnt;
 	args.found = 0;
-	err = kallsyms_on_each_symbol(kallsyms_callback, &args);
-	if (err < 0)
-		return err;
-	return args.found == args.cnt ? 0 : -ESRCH;
+
+	found_all = kallsyms_on_each_symbol(kallsyms_callback, &args);
+	if (found_all)
+		return 0;
+	found_all = module_kallsyms_on_each_symbol(kallsyms_callback, &args);
+	return found_all ? 0 : -ESRCH;
 }
 
 #ifdef CONFIG_SYSCTL