libbb: create and use mmap() helpers

function                                             old     new   delta
mmap_anon                                              -      22     +22
mmap_read                                              -      21     +21
xmmap_anon                                             -      16     +16
rpm_gettags                                          465     447     -18
bb_full_fd_action                                    498     480     -18
uevent_main                                          337     310     -27
------------------------------------------------------------------------------
(add/remove: 3/0 grow/shrink: 0/3 up/down: 59/-63)             Total: -4 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

archival/rpm.c

@@ -145,7 +145,7 @@ static int rpm_gettags(const char *filename)
 	/* remember size for munmap */
 	G.mapsize = storepos;
 	/* some NOMMU systems prefer MAP_PRIVATE over MAP_SHARED */
-	G.map = mmap(0, storepos, PROT_READ, MAP_PRIVATE, fd, 0);
+	G.map = mmap_read(fd, storepos);
 	if (G.map == MAP_FAILED)
 		bb_perror_msg_and_die("mmap '%s'", filename);
 

include/libbb.h

@@ -387,6 +387,9 @@ void* xrealloc_vector_helper(void *vector, unsigned sizeof_and_shift, int idx) F
 char *xstrdup(const char *s) FAST_FUNC RETURNS_MALLOC;
 char *xstrndup(const char *s, int n) FAST_FUNC RETURNS_MALLOC;
 void *xmemdup(const void *s, int n) FAST_FUNC RETURNS_MALLOC;
+void *mmap_read(int fd, size_t size) FAST_FUNC;
+void *mmap_anon(size_t size) FAST_FUNC;
+void *xmmap_anon(size_t size) FAST_FUNC;
 
 
 //TODO: supply a pointer to char[11] buffer (avoid statics)?

libbb/copyfd.c

@@ -75,10 +75,7 @@ static off_t bb_full_fd_action(int src_fd, int dst_fd, off_t size)
 				goto use_small_buf;
 			/* We want page-aligned buffer, just in case kernel is clever
 			 * and can do page-aligned io more efficiently */
-			buffer = mmap(NULL, CONFIG_FEATURE_COPYBUF_KB * 1024,
-					PROT_READ | PROT_WRITE,
-					MAP_PRIVATE | MAP_ANON,
-					/* ignored: */ -1, 0);
+			buffer = mmap_anon(CONFIG_FEATURE_COPYBUF_KB * 1024);
 			buffer_size = CONFIG_FEATURE_COPYBUF_KB * 1024;
 			if (buffer == MAP_FAILED) {
  use_small_buf:

libbb/xfuncs_printf.c

@@ -111,6 +111,27 @@ void* FAST_FUNC xmemdup(const void *s, int n)
 	return memcpy(xmalloc(n), s, n);
 }
 
+void* FAST_FUNC mmap_read(int fd, size_t size)
+{
+	return mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+}
+
+void* FAST_FUNC mmap_anon(size_t size)
+{
+	return mmap(NULL, size,
+			PROT_READ | PROT_WRITE,
+			MAP_PRIVATE | MAP_ANONYMOUS,
+			/* ignored: */ -1, 0);
+}
+
+void* FAST_FUNC xmmap_anon(size_t size)
+{
+	void *p = mmap_anon(size);
+	if (p == MAP_FAILED)
+		bb_die_memory_exhausted();
+	return p;
+}
+
 // Die if we can't open a file and return a FILE* to it.
 // Notice we haven't got xfread(), This is for use with fscanf() and friends.
 FILE* FAST_FUNC xfopen(const char *path, const char *mode)

modutils/modutils.c

@@ -169,7 +169,7 @@ void* FAST_FUNC try_to_mmap_module(const char *filename, size_t *image_size_p)
 	/* st.st_size is off_t, we can't just pass it to mmap */
 	if (st.st_size <= *image_size_p) {
 		size_t image_size = st.st_size;
-		image = mmap(NULL, image_size, PROT_READ, MAP_PRIVATE, fd, 0);
+		image = mmap_read(fd, image_size);
 		if (image == MAP_FAILED) {
 			image = NULL;
 		} else if (*(uint32_t*)image != SWAP_BE32(0x7f454C46)) {

util-linux/uevent.c

@@ -74,12 +74,7 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
 		// for a new uevent notification to come in.
 		// We use a fresh mmap so that buffer is not allocated
 		// until kernel actually starts filling it.
-		netbuf = mmap(NULL, USER_RCVBUF,
-					PROT_READ | PROT_WRITE,
-					MAP_PRIVATE | MAP_ANON,
-					/* ignored: */ -1, 0);
-		if (netbuf == MAP_FAILED)
-			bb_simple_perror_msg_and_die("mmap");
+		netbuf = xmmap_anon(USER_RCVBUF);
 
 		// Here we block, possibly for a very long time
 		len = safe_read(fd, netbuf, USER_RCVBUF - 1);