[wasi] Work arounbd WASI's mmap implementation not returning aligned …

…memory. (#91761)

Some code in sgen like sgen_los_free_object () expects the return address to be aligned.

Hopefully fixes #88501 and others.

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

@@ -90,8 +90,8 @@ mono_setmmapjit (int flag)
 	/* Ignored on HOST_WASM */
 }
 
-void*
-mono_valloc (void *addr, size_t size, int flags, MonoMemAccountType type)
+static void*
+valloc_impl (void *addr, size_t size, int flags, MonoMemAccountType type)
 {
 	void *ptr;
 	int mflags = 0;
@@ -119,6 +119,19 @@ mono_valloc (void *addr, size_t size, int flags, MonoMemAccountType type)
 	return ptr;
 }
 
+void*
+mono_valloc (void *addr, size_t size, int flags, MonoMemAccountType type)
+{
+#if HOST_WASI
+	// WASI implements mmap using malloc, so the returned address is not page aligned
+	// and our code depends on it
+	g_assert (!addr);
+	return mono_valloc_aligned (size, mono_pagesize (), flags, type);
+#else
+	return valloc_impl (addr, size, flags, type);
+#endif
+}
+
 static GHashTable *valloc_hash;
 
 typedef struct {
@@ -130,7 +143,7 @@ void*
 mono_valloc_aligned (size_t size, size_t alignment, int flags, MonoMemAccountType type)
 {
 	/* Allocate twice the memory to be able to put the block on an aligned address */
-	char *mem = (char *) mono_valloc (NULL, size + alignment, flags, type);
+	char *mem = (char *) valloc_impl (NULL, size + alignment, flags, type);
 	char *aligned;
 
 	if (!mem)