diff --git a/libretro-common/include/memmap.h b/libretro-common/include/memmap.h
index 2dea42bb66..ac0f7bedd4 100644
--- a/libretro-common/include/memmap.h
+++ b/libretro-common/include/memmap.h
@@ -34,23 +34,10 @@
 #include <sys/mman.h>
 #endif
 
-#if !defined(HAVE_MMAN)
-#define PROT_EXEC       0x04
-#define MAP_FAILED      0
-#define PROT_READ       0
-#define PROT_WRITE      0
-#define MAP_PRIVATE     0
-#define MAP_ANONYMOUS   0
-#endif
-
-#ifndef MAP_ANONYMOUS
-#define MAP_ANONYMOUS MAP_ANON
-#endif
-
 #if !defined(HAVE_MMAN) || defined(_WIN32)
-void* mmap(void *desired_addr, size_t len, int mmap_prot, int mmap_flags, int fildes, size_t off);
+void* mmap(void *addr, size_t len, int mmap_prot, int mmap_flags, int fildes, size_t off);
 
-void munmap(void *base_addr, size_t len);
+int munmap(void *addr, size_t len);
 
 int mprotect(void *addr, size_t len, int prot);
 #endif
diff --git a/libretro-common/memmap/memmap.c b/libretro-common/memmap/memmap.c
index 74ee917e20..cf8a631fb7 100644
--- a/libretro-common/memmap/memmap.c
+++ b/libretro-common/memmap/memmap.c
@@ -23,109 +23,72 @@
 #include <stdint.h>
 #include <memmap.h>
 
+#ifndef PROT_READ
+#define PROT_READ     0x1  /* Page can be read */
+#endif
+
+#ifndef PROT_WRITE
+#define PROT_WRITE    0x2  /* Page can be written. */
+#endif
+
+#ifndef PROT_EXEC
+#define PROT_EXEC     0x4  /* Page can be executed. */
+#endif
+
+#ifndef PROT_NONE
+#define PROT_NONE     0x0  /* Page can not be accessed. */
+#endif
+
 #ifdef _WIN32
-#define MAP_SHARED    0x01
-
-#ifndef MAP_PRIVATE
-#define MAP_PRIVATE   0x02
-#endif
-
-#ifndef MAP_ANONYMOUS
-#define MAP_ANONYMOUS 0x20
-#endif
-
-#define MAP_ANON      MAP_ANONYMOUS
-#define MAP_FAILED    ((void *) -1)
-#define PROT_READ     0x1
-#define PROT_WRITE    0x2
-
-/* This flag is only available in WinXP+ */
-#ifdef FILE_MAP_EXECUTE
-#ifndef PROT_EXEC
-#define PROT_EXEC     0x4
-#endif
-#else
-#ifndef PROT_EXEC
-#define PROT_EXEC     0x0
-#endif
-
-#define FILE_MAP_EXECUTE 0
-#endif
-
-#ifdef __USE_FILE_OFFSET64
-# define DWORD_HI(x) (x >> 32)
-# define DWORD_LO(x) ((x) & 0xffffffff)
-#else
-# define DWORD_HI(x) (0)
-# define DWORD_LO(x) (x)
-#endif
-
 void* mmap(void *addr, size_t len, int prot, int flags, int fildes, size_t offset)
 {
-	uint32_t flProtect, dwDesiredAccess;
-	off_t end;
-	HANDLE mmap_fd, h;
-	void *ret;
+   void     *map = (void*)NULL;
+   HANDLE handle = INVALID_HANDLE_VALUE;
 
-	if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC))
-		return MAP_FAILED;
-
-	if (fd == -1)
+   switch (prot)
    {
-		if (!(flags & MAP_ANON) || offset)
-			return MAP_FAILED;
-	}
-   else if (flags & MAP_ANON)
-		return MAP_FAILED;
-
-	if (prot & PROT_WRITE)
-   {
-      flProtect = PAGE_READWRITE;
-      if (prot & PROT_EXEC)
-         flProtect = PAGE_EXECUTE_READWRITE;
+      case PROT_READ:
+      default:
+         {
+            handle = CreateFileMapping((HANDLE) _get_osfhandle(fildes), 0, PAGE_READONLY, 0,
+                  len, 0);
+            if (!handle)
+               break;
+            map = (void*)MapViewOfFile(handle, FILE_MAP_READ, 0, 0, len);
+            CloseHandle(handle);
+            break;
+         }
+      case PROT_WRITE:
+         {
+            handle = CreateFileMapping((HANDLE) _get_osfhandle(fildes),0,PAGE_READWRITE,0,
+                  len, 0);
+            if (!handle)
+               break;
+            map = (void*)MapViewOfFile(handle, FILE_MAP_WRITE, 0, 0, len);
+            CloseHandle(handle);
+            break;
+         }
+      case PROT_READWRITE:
+         {
+            handle = CreateFileMapping((HANDLE) _get_osfhandle(fildes),0,PAGE_READWRITE,0,
+                  len, 0);
+            if (!handle)
+               break;
+            map = (void*)MapViewOfFile(handle, FILE_MAP_ALL_ACCESS, 0, 0, len);
+            CloseHandle(handle);
+            break;
+         }
    }
-   else if (prot & PROT_EXEC)
-   {
-      flProtect = PAGE_EXECUTE;
-		if (prot & PROT_READ)
-			flProtect = PAGE_EXECUTE_READ;
-	}
-   else
-		flProtect = PAGE_READONLY;
-
-	end = length + offset;
-
-	if (fd == -1)
-		mmap_fd = INVALID_HANDLE_VALUE;
-	else
-		mmap_fd = (HANDLE)_get_osfhandle(fd);
-
-	h = CreateFileMapping(mmap_fd, NULL, flProtect, DWORD_HI(end), DWORD_LO(end), NULL);
-	if (h == NULL)
-		return MAP_FAILED;
-
-   dwDesiredAccess = FILE_MAP_READ;
-	if (prot & PROT_WRITE)
-		dwDesiredAccess = FILE_MAP_WRITE;
-	if (prot & PROT_EXEC)
-		dwDesiredAccess |= FILE_MAP_EXECUTE;
-	if (flags & MAP_PRIVATE)
-		dwDesiredAccess |= FILE_MAP_COPY;
-	ret = MapViewOfFile(h, dwDesiredAccess, DWORD_HI(offset), DWORD_LO(offset), length);
-
-	if (ret == NULL)
-   {
-		CloseHandle(h);
-		ret = MAP_FAILED;
-	}
-
-	return ret;
+   if (map == (void*)NULL)
+      return((void*)MAP_FAILED);
+   return((void*) ((int8_t*)map + offset));
 }
 
-void munmap(void *addr, size_t length)
+int munmap(void *addr, size_t length)
 {
-	UnmapViewOfFile(addr);
-	/* ruh-ro, we leaked handle from CreateFileMapping() ... */
+   if (!UnmapViewOfFile(addr))
+      return -1;
+   return 0;
 }
 
 int mprotect(void *addr, size_t len, int prot)
@@ -144,9 +107,10 @@ void* mmap(void *addr, size_t len, int prot, int flags, int fildes, size_t offse
    return malloc(len);
 }
 
-void munmap(void *addr, size_t len)
+int munmap(void *addr, size_t len)
 {
    free(addr);
+   return 0;
 }
 
 int mprotect(void *addr, size_t len, int prot)