sync after unmap and add prot check

2 files changed, 19 insertions, 0 deletions

diff --git a/README.md b/README.md
index 6b1817d..2ede515 100644
--- a/README.md
+++ b/README.md
@@ -21,6 +21,9 @@ additional extensions:
 - pipe and event support (`pipe`, `event` )
 - DNS resolution support (`resolve` )
 
+# NOTES
+- Memory mapping is currently not compatible with threads
+
 # WASI(X) Extensions Spec
 
 [WASIX](https://wasix.org) is maintained by wasix.org [here](https://github.com/wasix-org/wasix-witx)
diff --git a/libc-bottom-half/mman/mman.c b/libc-bottom-half/mman/mman.c
index 511b379..e4ae27d 100644
--- a/libc-bottom-half/mman/mman.c
+++ b/libc-bottom-half/mman/mman.c
@@ -117,6 +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);
     }
 
@@ -135,6 +136,16 @@ 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 != -1) {
+        if ((map->prot & PROT_WRITE) != 0) {
+            msync(addr, length, MS_SYNC);
+        }
+
+        close(map->fd);
+    }
+
     // Success!
     return 0;
 }
@@ -151,6 +162,11 @@ int msync (void *addr, size_t length, int flags) {
         return -1;
     }
 
+    if ((map->prot & PROT_WRITE) != 0) {
+        errno = EINVAL;
+        return -1;
+    }
+
     if ((map_flags & MAP_ANON) == 0) {
         char *body = (char *)addr;