modpost: use read_text_file() and get_line() for reading text files

grab_file() mmaps a file, but it is not so efficient here because
get_next_line() copies every line to the temporary buffer anyway.

read_text_file() and get_line() are simpler. get_line() exploits the
library function strchr().

Going forward, the missing *.symvers or *.cmd is a fatal error.
This should not happen because scripts/Makefile.modpost guards the
-i option files with $(wildcard $(input-symdump)).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 0a84490..4fdf992 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2481,15 +2481,16 @@ static void write_if_changed(struct buffer *b, const char *fname)
  **/
 static void read_dump(const char *fname)
 {
-	unsigned long size, pos = 0;
-	void *file = grab_file(fname, &size);
-	char *line;
+	char *buf, *pos, *line;
 
-	if (!file)
+	buf = read_text_file(fname);
+	if (!buf)
 		/* No symbol versions, silently ignore */
 		return;
 
-	while ((line = get_next_line(&pos, file, size))) {
+	pos = buf;
+
+	while ((line = get_line(&pos))) {
 		char *symname, *namespace, *modname, *d, *export;
 		unsigned int crc;
 		struct module *mod;
@@ -2524,10 +2525,10 @@ static void read_dump(const char *fname)
 		sym_set_crc(symname, crc);
 		sym_update_namespace(symname, namespace);
 	}
-	release_file(file, size);
+	free(buf);
 	return;
 fail:
-	release_file(file, size);
+	free(buf);
 	fatal("parse error in symbol dump file\n");
 }