HACK: Use sbrk instead of mmap to allocate wasm pages, to skip memset…

…. Disable vfree.

src/mono/mono/utils/mono-mmap-wasm.c

@@ -90,6 +90,8 @@ mono_setmmapjit (int flag)
 	/* Ignored on HOST_WASM */
 }
 
+void *sbrk (intptr_t increment);
+
 static void*
 valloc_impl (void *addr, size_t size, int flags, MonoMemAccountType type)
 {
@@ -104,14 +106,8 @@ valloc_impl (void *addr, size_t size, int flags, MonoMemAccountType type)
 		/* emscripten throws an exception on 0 length */
 		return NULL;
 
-	mflags |= MAP_ANONYMOUS;
-	mflags |= MAP_PRIVATE;
-
-	BEGIN_CRITICAL_SECTION;
-	ptr = mmap (addr, size, prot, mflags, -1, 0);
-	END_CRITICAL_SECTION;
-
-	if (ptr == MAP_FAILED)
+	ptr = sbrk (size);
+	if (ptr == 0)
 		return NULL;
 
 	mono_account_mem (type, (ssize_t)size);
@@ -167,26 +163,7 @@ mono_valloc_aligned (size_t size, size_t alignment, int flags, MonoMemAccountTyp
 int
 mono_vfree (void *addr, size_t length, MonoMemAccountType type)
 {
-	VallocInfo *info = (VallocInfo*)(valloc_hash ? g_hash_table_lookup (valloc_hash, addr) : NULL);
-
-	if (info) {
-		/*
-		 * We are passed the aligned address in the middle of the mapping allocated by
-		 * mono_valloc_align (), free the original mapping.
-		 */
-		BEGIN_CRITICAL_SECTION;
-		munmap (info->addr, info->size);
-		END_CRITICAL_SECTION;
-		g_free (info);
-		g_hash_table_remove (valloc_hash, addr);
-	} else {
-		BEGIN_CRITICAL_SECTION;
-		munmap (addr, length);
-		END_CRITICAL_SECTION;
-	}
-
-	mono_account_mem (type, -(ssize_t)length);
-
+	g_warning ("mono_vfree not implemented on webassembly; silently failing to free\n");
 	return 0;
 }