[mono] Fix LoadAssemblyRaw to not pin or copy (#43830)

* [mono] Fix LoadAssemblyRaw to not pin or copy

Copying of the assembly and symbols happens later, in `mono_alc_load_raw_bytes`, and the pinning is no longer necessary so long as we have the handle.

* Handle null symbol store

src/mono/mono/metadata/appdomain.c

@@ -2789,33 +2789,20 @@ ves_icall_System_AppDomain_LoadAssemblyRaw (MonoAppDomainHandle ad,
 {
 	MonoAssembly *ass;
 	MonoReflectionAssemblyHandle refass = MONO_HANDLE_CAST (MonoReflectionAssembly, NULL_HANDLE);
-	MonoDomain *domain = MONO_HANDLE_GETVAL(ad, data);
-	guint32 raw_assembly_len = mono_array_handle_length (raw_assembly);
-
-	/* Copy the data ourselves to unpin the raw assembly byte array as soon as possible */
-	guint8 *assembly_data = (guint8*) g_try_malloc (raw_assembly_len);
-	if (!assembly_data) {
-		mono_error_set_out_of_memory (error, "Could not allocate %ud bytes to copy raw assembly data", raw_assembly_len);
-		return refass;
-	}
-	MonoGCHandle gchandle;
-	mono_byte *raw_data = (mono_byte*) MONO_ARRAY_HANDLE_PIN (raw_assembly, gchar, 0, &gchandle);
-	memcpy (assembly_data, raw_data, raw_assembly_len);
-	mono_gchandle_free_internal (gchandle); /* unpin */
-	MONO_HANDLE_ASSIGN (raw_assembly, NULL_HANDLE); /* don't reference the data anymore */
-
+	MonoDomain *domain = MONO_HANDLE_GETVAL (ad, data);
 	MonoAssemblyLoadContext *alc = mono_domain_default_alc (domain);
 
-	mono_byte *raw_symbol_data = NULL;
-	guint32 symbol_len = 0;
-	MonoGCHandle symbol_gchandle = 0;
+	guint8 *raw_assembly_ptr = (guint8 *)mono_array_handle_addr (raw_assembly, sizeof (guint8), 0);
+	guint32 raw_assembly_len = mono_array_handle_length (raw_assembly);
+
+	guint8 *raw_symbols_ptr = NULL;
+	guint32 raw_symbols_len = 0;
 	if (!MONO_HANDLE_IS_NULL (raw_symbol_store)) {
-		symbol_len = mono_array_handle_length (raw_symbol_store);
-		raw_symbol_data = (mono_byte*) MONO_ARRAY_HANDLE_PIN (raw_symbol_store, mono_byte, 0, &symbol_gchandle);
+		raw_symbols_ptr = (guint8 *)mono_array_handle_addr (raw_symbol_store, sizeof (guint8), 0);
+		raw_symbols_len = mono_array_handle_length (raw_symbol_store);
 	}
 
-	ass = mono_alc_load_raw_bytes (alc, assembly_data, raw_assembly_len, raw_symbol_data, symbol_len, refonly, error);
-	mono_gchandle_free_internal (symbol_gchandle);
+	ass = mono_alc_load_raw_bytes (alc, raw_assembly_ptr, raw_assembly_len, raw_symbols_ptr, raw_symbols_len, refonly, error);
 	goto_if_nok (error, leave);
 
 	refass = mono_assembly_get_object_handle (domain, ass, error);

src/mono/mono/metadata/handle.c

@@ -414,13 +414,19 @@ mono_gchandle_get_target_handle (MonoGCHandle gchandle)
 	return MONO_HANDLE_NEW (MonoObject, mono_gchandle_get_target_internal (gchandle));
 }
 
+gpointer
+mono_array_handle_addr (MonoArrayHandle handle, int size, uintptr_t index)
+{
+	MonoArray *raw = MONO_HANDLE_RAW (handle);
+	return mono_array_addr_with_size_internal (raw, size, index);
+}
+
 gpointer
 mono_array_handle_pin_with_size (MonoArrayHandle handle, int size, uintptr_t idx, MonoGCHandle *gchandle)
 {
 	g_assert (gchandle != NULL);
 	*gchandle = mono_gchandle_from_handle (MONO_HANDLE_CAST(MonoObject,handle), TRUE);
-	MonoArray *raw = MONO_HANDLE_RAW (handle);
-	return mono_array_addr_with_size_internal (raw, size, idx);
+	return mono_array_handle_addr (handle, size, idx);
 }
 
 gunichar2*

src/mono/mono/metadata/handle.h

@@ -651,6 +651,10 @@ mono_array_handle_memcpy_refs (MonoArrayHandle dest, uintptr_t dest_idx, MonoArr
 gpointer
 mono_array_handle_pin_with_size (MonoArrayHandle handle, int size, uintptr_t index, MonoGCHandle *gchandle);
 
+// Returns a pointer to the element with the given index, but does not pin
+gpointer
+mono_array_handle_addr (MonoArrayHandle handle, int size, uintptr_t index);
+
 #define MONO_ARRAY_HANDLE_PIN(handle,type,index,gchandle_out) ((type*)mono_array_handle_pin_with_size (MONO_HANDLE_CAST(MonoArray,(handle)), sizeof (type), (index), (gchandle_out)))
 
 void