Landing: Write protect executable pages in the VM.

runtime/vm/object_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
@@ skipping 2446 matching lines @@
       static_cast<int32_t>(entry_point), 0, 0, 0, 0));
 #else
   typedef intptr_t (*IncrementCode)();
   retval = reinterpret_cast<IncrementCode>(entry_point)();
 #endif
   EXPECT_EQ(2, retval);
   EXPECT_EQ(instructions.raw(), Instructions::FromEntryPoint(entry_point));
 }
 
 
+// Test for immutability of generated instructions. The test crashes with a
+// segmentation fault when writing into it.
+TEST_CASE(CodeImmutability) {
+  extern void GenerateIncrement(Assembler* assembler);
+  Assembler _assembler_;
+  GenerateIncrement(&_assembler_);
+  Code& code = Code::Handle(Code::FinalizeCode(
+      *CreateFunction("Test_Code"), &_assembler_));
+  Instructions& instructions = Instructions::Handle(code.instructions());
+  uword entry_point = instructions.EntryPoint();
+  // Try writing into the generated code, expected to crash.
+  *(reinterpret_cast<char*>(entry_point) + 1) = 1;
+  intptr_t retval = 0;
+#if defined(USING_SIMULATOR)
+  retval = bit_copy<intptr_t, int64_t>(Simulator::Current()->Call(
+      static_cast<int32_t>(entry_point), 0, 0, 0, 0));
+#else
+  typedef intptr_t (*IncrementCode)();
+  retval = reinterpret_cast<IncrementCode>(entry_point)();
+#endif
+  EXPECT_EQ(3, retval);
+  EXPECT_EQ(instructions.raw(), Instructions::FromEntryPoint(entry_point));
+}
+
+
 // Test for Embedded String object in the instructions.
 TEST_CASE(EmbedStringInCode) {
   extern void GenerateEmbedStringInCode(Assembler* assembler, const char* str);
   const char* kHello = "Hello World!";
   word expected_length = static_cast<word>(strlen(kHello));
   Assembler _assembler_;
   GenerateEmbedStringInCode(&_assembler_, kHello);
   Code& code = Code::Handle(Code::FinalizeCode(
       *CreateFunction("Test_EmbedStringInCode"), &_assembler_));
   Instructions& instructions = Instructions::Handle(code.instructions());
@@ skipping 1505 matching lines @@
   // Simple map.
   //
   // TODO(turnidge): Consider showing something like: {1: 2, 2: 'otter'}
   result = Dart_GetField(lib, NewString("simple_map"));
   EXPECT_VALID(result);
   obj ^= Api::UnwrapHandle(result);
   EXPECT_STREQ("Instance of '_LinkedHashMap'", obj.ToUserCString());
 }
 
 }  // namespace dart