From cd5cfb4c2dbbf5615c78d1e439f0cbfb08437b43 Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@tuebingen.mpg.de>
Date: Sun, 15 Feb 2015 16:42:05 +0100
Subject: [PATCH] Simplify and rename mmap_full_file().

There is only one caller which maps the file privately into read-only
memory. Moreover, this caller does not care about the file descriptor
from which the mapping was created.

This commit removes the argument from mmap_full_file() which control
the type of the map and the result pointer for the file descriptor,
thereby simplifying the function slightly. Rename it to mmap_file_ro()
to indicate that read-only private mappings are implied.
---
 fd.c   | 32 +++++++++-----------------------
 fd.h   |  3 +--
 user.c |  2 +-
 3 files changed, 11 insertions(+), 26 deletions(-)

diff --git a/fd.c b/fd.c
index 7984356..9fe8867 100644
--- a/fd.c
+++ b/fd.c
@@ -199,36 +199,25 @@ int adu_fchdir(int fd)
 }
 
 /**
- * Open a file and map it into memory.
+ * Open a file read-only and map it into memory.
  *
  * \param path Name of the regular file to map.
- * \param open_mode Either \p O_RDONLY or \p O_RDWR.
  * \param map On success, the mapping is returned here.
- * \param size size of the mapping.
- * \param fd_ptr The file descriptor of the mapping.
+ * \param size Result parameter: size of the mapping in bytes.
  *
- * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
- * open call is closed after mmap().  Otherwise the file is kept open and the
- * file descriptor is returned in \a fd_ptr.
+ * The file will be mapped privately with memory protection PROT_READ. The file
+ * descriptor resulting from the underlying open call is closed after mmap().
  *
  * \return Standard.
  *
  * \sa mmap(2).
  */
-int mmap_full_file(const char *path, int open_mode, void **map,
-		size_t *size, int *fd_ptr)
+int mmap_file_ro(const char *path, void **map, size_t *size)
 {
-	int fd, ret, mmap_prot, mmap_flags;
+	int fd, ret;
 	struct stat file_status;
 
-	if (open_mode == O_RDONLY) {
-		mmap_prot = PROT_READ;
-		mmap_flags = MAP_PRIVATE;
-	} else {
-		mmap_prot = PROT_READ | PROT_WRITE;
-		mmap_flags = MAP_SHARED;
-	}
-	ret = __open(path, open_mode, 0);
+	ret = __open(path, O_RDONLY, 0);
 	if (ret < 0)
 		return ret;
 	fd = ret;
@@ -241,7 +230,7 @@ int mmap_full_file(const char *path, int open_mode, void **map,
 	DEBUG_LOG("%s: size %zu\n", path, *size);
 	if (!*size)
 		goto out;
-	*map = mmap(NULL, *size, mmap_prot, mmap_flags, fd, 0);
+	*map = mmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (*map == MAP_FAILED) {
 		*map = NULL;
 		ret = -E_MMAP;
@@ -249,10 +238,7 @@ int mmap_full_file(const char *path, int open_mode, void **map,
 	}
 	ret = 1;
 out:
-	if (ret < 0 || !fd_ptr)
-		close(fd);
-	else
-		*fd_ptr = fd;
+	close(fd);
 	return ret;
 }
 
diff --git a/fd.h b/fd.h
index 1089932..a3d1d9d 100644
--- a/fd.h
+++ b/fd.h
@@ -8,8 +8,7 @@
 
 int adu_opendir(const char *dirname, DIR **dir, int *cwd);
 int adu_fchdir(int fd);
-int mmap_full_file(const char *filename, int open_mode, void **map,
-	size_t *size, int *fd_ptr);
+int mmap_file_ro(const char *filename, void **map, size_t *size);
 int adu_munmap(void *start, size_t length);
 int adu_write_file(const char *filename, const void *buf, size_t size);
 int mkpath(const char *p, mode_t mode);
diff --git a/user.c b/user.c
index a1513a4..ed16463 100644
--- a/user.c
+++ b/user.c
@@ -511,7 +511,7 @@ int read_uid_file(void)
 	size_t size;
 	uint32_t n;
 	char *filename = get_uid_list_name(), *map;
-	int ret = mmap_full_file(filename, O_RDONLY, (void **)&map, &size, NULL);
+	int ret = mmap_file_ro(filename, (void **)&map, &size);
 	unsigned bits;
 
 	if (ret < 0) {
-- 
2.39.5