modpost: add read_text_file() and get_line() helpers

modpost uses grab_file() to open a file, but it is not suitable for
a text file because the mmap'ed file is not terminated by null byte.
Actually, I see some issues for the use of grab_file().

The new helper, read_text_file() loads the whole file content into a
malloc'ed buffer, and appends a null byte. Then, get_line() reads
each line.

To handle text files, I intend to replace as follows:

  grab_file()    -> read_text_file()
  get_new_line() -> get_line()

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

1 files changed, 49 insertions, 0 deletions

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index a5da633af700..0a844902998e 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -112,6 +112,55 @@ void *do_nofail(void *ptr, const char *expr)
 	return ptr;
 }
 
+char *read_text_file(const char *filename)
+{
+	struct stat st;
+	size_t nbytes;
+	int fd;
+	char *buf;
+
+	fd = open(filename, O_RDONLY);
+	if (fd < 0) {
+		perror(filename);
+		exit(1);
+	}
+
+	if (fstat(fd, &st) < 0) {
+		perror(filename);
+		exit(1);
+	}
+
+	buf = NOFAIL(malloc(st.st_size + 1));
+
+	nbytes = st.st_size;
+
+	while (nbytes) {
+		ssize_t bytes_read;
+
+		bytes_read = read(fd, buf, nbytes);
+		if (bytes_read < 0) {
+			perror(filename);
+			exit(1);
+		}
+
+		nbytes -= bytes_read;
+	}
+	buf[st.st_size] = '\0';
+
+	close(fd);
+
+	return buf;
+}
+
+char *get_line(char **stringp)
+{
+	/* do not return the unwanted extra line at EOF */
+	if (*stringp && **stringp == '\0')
+		return NULL;
+
+	return strsep(stringp, "\n");
+}
+
 /* A list of all modules we processed */
 static struct module *modules;