[PATCH v2 03/29] modpost: add read_text_file() and get_line() helpers

[Masahiro Yamada]

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@xxxxxxxxxx>
---

Changes in v2:
  - Iterate in while () {} in case read() returns shorter read bytes

 scripts/mod/modpost.c | 46 +++++++++++++++++++++++++++++++++++++++++++
 scripts/mod/modpost.h |  2 ++
 2 files changed, 48 insertions(+)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index af098d7efc22..139b811dc183 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -112,6 +112,52 @@ 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)
+		return NULL;
+
+	if (fstat(fd, &st) < 0)
+		return NULL;
+
+	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) {
+			free(buf);
+			buf = NULL;
+			goto close;
+		}
+
+		nbytes -= bytes_read;
+	}
+	buf[st.st_size] = '\0';
+close:
+	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;
 
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index bbaf5cc37bfb..dfadaa0c01ec 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -190,6 +190,8 @@ void add_moddevtable(struct buffer *buf, struct module *mod);
 void get_src_version(const char *modname, char sum[], unsigned sumlen);
 
 /* from modpost.c */
+char *read_text_file(const char *filename);
+char *get_line(char **stringp);
 void *grab_file(const char *filename, unsigned long *size);
 char* get_next_line(unsigned long *pos, void *file, unsigned long size);
 void release_file(void *file, unsigned long size);
-- 
2.25.1