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>

6 files changed, 28 insertions, 12 deletions

diff --git a/archival/rpm.c b/archival/rpm.c
index 68afba914..a4d850b46 100644
--- a/archival/rpm.c
+++ b/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);
 
diff --git a/include/libbb.h b/include/libbb.h
index 8f1ee7eec..a74b3119f 100644
--- a/include/libbb.h
+++ b/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)?
diff --git a/libbb/copyfd.c b/libbb/copyfd.c
index d41fd10f0..7f9d92ea9 100644
--- a/libbb/copyfd.c
+++ b/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:
diff --git a/libbb/xfuncs_printf.c b/libbb/xfuncs_printf.c
index fcc798662..db40e996b 100644
--- a/libbb/xfuncs_printf.c
+++ b/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)
diff --git a/modutils/modutils.c b/modutils/modutils.c
index 6f7cd9721..f7ad5e805 100644
--- a/modutils/modutils.c
+++ b/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)) {
diff --git a/util-linux/uevent.c b/util-linux/uevent.c
index 045b35432..015f1ee78 100644
--- a/util-linux/uevent.c
+++ b/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);