1 files changed, 61 insertions, 0 deletions

diff --git a/libc-bottom-half/mman/mman.c b/libc-bottom-half/mman/mman.c
index 87f08ba..32bce04 100644
--- a/libc-bottom-half/mman/mman.c
+++ b/libc-bottom-half/mman/mman.c
@@ -21,6 +21,7 @@ struct map {
     int flags;
     off_t offset;
     size_t length;
+    int fd;
 };
 
 void *mmap(void *addr, size_t length, int prot, int flags,
@@ -90,6 +91,17 @@ void *mmap(void *addr, size_t length, int prot, int flags,
     // or with zeros.
     addr = map + 1;
     if ((flags & MAP_ANON) == 0) {
+        int new_fd = dup(fd);
+
+        if (new_fd < 0) {
+            errno = EINVAL;
+            free(map);
+
+            return NULL;
+        }
+
+        map->fd = new_fd;
+
         char *body = (char *)addr;
         while (length > 0) {
             const ssize_t nread = pread(fd, body, length, offset);
@@ -105,6 +117,7 @@ void *mmap(void *addr, size_t length, int prot, int flags,
             body += (size_t)nread;
         }
     } else {
+        map->fd = -1;
         memset(addr, 0, length);
     }
 
@@ -123,6 +136,54 @@ int munmap(void *addr, size_t length) {
     // Release the memory.
     free(map);
 
+    // Write the data back to the backing file and close
+    // the file handle
+    if (map->fd > 0) {
+        if ((map->prot & PROT_WRITE) != 0) {
+            msync(addr, length, MS_SYNC);
+        }
+
+        close(map->fd);
+    }
+
     // Success!
     return 0;
 }
+
+int msync (void *addr, size_t length, int flags) {
+    struct map *map = (struct map *)addr - 1;
+    size_t map_flags = map->flags;
+    off_t map_offset = map->offset;
+    size_t map_length = map->length;
+    int fd = map->fd;
+
+    if (length > map_length) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    if ((map->prot & PROT_WRITE) != 0) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    if ((map_flags & MAP_ANON) == 0) {
+        char *body = (char *)addr;
+
+        while (length > 0) {
+            const ssize_t nwrite = pwrite(fd, body, length, map_offset);
+
+            if (nwrite > 0) {
+                length -= (size_t)nwrite;
+                map_offset += (size_t)nwrite;
+                body += (size_t)nwrite;
+            } else if (errno == EINTR) {
+                continue;
+            } else {
+                return -1;
+            }
+        }
+    }
+
+    return 0;
+}