Fix initialization of large-sized NSData (#85)

src/chomper/os/ios/hooks.py

@@ -528,3 +528,26 @@ def hook_sec_item_copy_matching(uc, address, size, user_data):
         emu.write_u64(a2, result)
 
     return 0
+
+
+@register_hook("_mach_vm_allocate")
+def hook_mach_vm_allocate(uc, address, size, user_data):
+    emu = user_data["emu"]
+
+    addr = emu.get_arg(1)
+    size = emu.get_arg(2)
+
+    mem = emu.memory_manager.alloc(size)
+    emu.write_pointer(addr, mem)
+
+    return 0
+
+
+@register_hook("_mach_vm_deallocate")
+def hook_mach_vm_deallocate(uc, address, size, user_data):
+    emu = user_data["emu"]
+
+    mem = emu.get_arg(1)
+    emu.memory_manager.free(mem)
+
+    return 0

tests/test_objc.py

@@ -37,6 +37,19 @@ def test_ns_data(emu_ios, objc):
         assert data
 
 
+def test_ns_data_with_large_size(emu_ios, objc):
+    """When the size of `NSData` exceeds 64k, `vm_allocate` will be called."""
+    with objc.autorelease_pool():
+        data_bytes = bytes(1024 * 64)
+
+        buffer = emu_ios.create_buffer(len(data_bytes))
+        emu_ios.write_bytes(buffer, data_bytes)
+
+        data = objc.msg_send("NSData", "dataWithBytes:length:", buffer, len(data_bytes))
+
+        assert data
+
+
 def test_ns_url(emu_ios, objc):
     with objc.autorelease_pool():
         string = objc.msg_send(