diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 2c1968061b4bc4cbabba1db3a3a8ef78247faae3..faa5bf4a5a3a7eca57e18658913c88373ef945ec 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -86,8 +86,12 @@
 # define F_LINUX_SPECIFIC_BASE	1024
 #endif
 
+/*
+ * strtoul: Go from a string to a value, i.e. for msr: MSR_FS_BASE to 0xc0000100
+ */
 struct syscall_arg_fmt {
 	size_t	   (*scnprintf)(char *bf, size_t size, struct syscall_arg *arg);
+	bool	   (*strtoul)(char *bf, size_t size, struct syscall_arg *arg, u64 *val);
 	unsigned long (*mask_val)(struct syscall_arg *arg, unsigned long val);
 	void	   *parm;
 	const char *name;
@@ -1543,8 +1547,10 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field
                } else {
 			struct syscall_arg_fmt *fmt = syscall_arg_fmt__find_by_name(field->name);
 
-			if (fmt)
+			if (fmt) {
 				arg->scnprintf = fmt->scnprintf;
+				arg->strtoul   = fmt->strtoul;
+			}
 		}
 	}