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/sumversion.c b/scripts/mod/sumversion.c
index 9f77c9d..d587f40 100644
--- a/scripts/mod/sumversion.c
+++ b/scripts/mod/sumversion.c
@@ -303,9 +303,8 @@ static int is_static_library(const char *objfile)
  * to figure out source files. */
 static int parse_source_files(const char *objfile, struct md4_ctx *md)
 {
-	char *cmd, *file, *line, *dir;
+	char *cmd, *file, *line, *dir, *pos;
 	const char *base;
-	unsigned long flen, pos = 0;
 	int dirlen, ret = 0, check_files = 0;
 
 	cmd = NOFAIL(malloc(strlen(objfile) + sizeof("..cmd")));
@@ -323,14 +322,12 @@ static int parse_source_files(const char *objfile, struct md4_ctx *md)
 	strncpy(dir, objfile, dirlen);
 	dir[dirlen] = '\0';
 
-	file = grab_file(cmd, &flen);
-	if (!file) {
-		warn("could not find %s for %s\n", cmd, objfile);
-		goto out;
-	}
+	file = read_text_file(cmd);
+
+	pos = file;
 
 	/* Sum all files in the same dir or subdirs. */
-	while ((line = get_next_line(&pos, file, flen)) != NULL) {
+	while ((line = get_line(&pos))) {
 		char* p = line;
 
 		if (strncmp(line, "source_", sizeof("source_")-1) == 0) {
@@ -381,8 +378,7 @@ static int parse_source_files(const char *objfile, struct md4_ctx *md)
 	/* Everyone parsed OK */
 	ret = 1;
 out_file:
-	release_file(file, flen);
-out:
+	free(file);
 	free(dir);
 	free(cmd);
 	return ret;