Landing: Write protect executable pages in the VM.

runtime/vm/code_generator.cc

 // Copyright (c) 2013, 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/code_generator.h"
 
 #include "vm/assembler.h"
 #include "vm/ast.h"
 #include "vm/bigint_operations.h"
 #include "vm/code_patcher.h"
@@ skipping 648 matching lines @@
         Error::Handle(Compiler::CompileFunction(target_function));
     if (!error.IsNull()) {
       Exceptions::PropagateError(error);
     }
   }
   const Code& target_code = Code::Handle(target_function.CurrentCode());
   // Before patching verify that we are not repeatedly patching to the same
   // target.
   ASSERT(target_code.EntryPoint() !=
          CodePatcher::GetStaticCallTargetAt(caller_frame->pc(), caller_code));
-  CodePatcher::PatchStaticCallAt(caller_frame->pc(), caller_code,
-                                 target_code.EntryPoint());
-  caller_code.SetStaticCallTargetCodeAt(caller_frame->pc(), target_code);
+  const Instructions& instrs =
+      Instructions::Handle(caller_code.instructions());
+  {
+    WritableInstructionsScope writable(instrs.EntryPoint(), instrs.size());
+    CodePatcher::PatchStaticCallAt(caller_frame->pc(), caller_code,
+                                   target_code.EntryPoint());
+    caller_code.SetStaticCallTargetCodeAt(caller_frame->pc(), target_code);
+  }
   if (FLAG_trace_patching) {
     OS::PrintErr("PatchStaticCall: patching from %#" Px " to '%s' %#" Px "\n",
         caller_frame->pc(),
         target_function.ToFullyQualifiedCString(),
         target_code.EntryPoint());
   }
   arguments.SetReturn(target_code);
 }
 
 
@@ skipping 674 matching lines @@
     const Error& error =
         Error::Handle(Compiler::CompileFunction(target_function));
     if (!error.IsNull()) {
       Exceptions::PropagateError(error);
     }
   }
   ASSERT(target_function.HasCode());
   ASSERT(target_function.raw() == target_code.function());
 
   const Code& current_target_code = Code::Handle(target_function.CurrentCode());
-  CodePatcher::PatchStaticCallAt(frame->pc(), caller_code,
-                                 current_target_code.EntryPoint());
-  caller_code.SetStaticCallTargetCodeAt(frame->pc(), current_target_code);
+  const Instructions& instrs = Instructions::Handle(caller_code.instructions());
+  {
+    WritableInstructionsScope writable(instrs.EntryPoint(), instrs.size());
+    CodePatcher::PatchStaticCallAt(frame->pc(), caller_code,
+                                   current_target_code.EntryPoint());
+    caller_code.SetStaticCallTargetCodeAt(frame->pc(), current_target_code);
+  }
   if (FLAG_trace_patching) {
     OS::PrintErr("FixCallersTarget: patching from %#" Px " to '%s' %#" Px "\n",
         frame->pc(),
         target_function.ToFullyQualifiedCString(),
         current_target_code.EntryPoint());
   }
   arguments.SetReturn(current_target_code);
 }
 
 
@@ skipping 19 matching lines @@
   const Code& unoptimized_code = Code::Handle(function.unoptimized_code());
   ASSERT(!unoptimized_code.IsNull());
   // The switch to unoptimized code may have already occurred.
   if (function.HasOptimizedCode()) {
     function.SwitchToUnoptimizedCode();
   }
   // Patch call site (lazy deoptimization is quite rare, patching it twice
   // is not a performance issue).
   uword lazy_deopt_jump = optimized_code.GetLazyDeoptPc();
   ASSERT(lazy_deopt_jump != 0);
-  CodePatcher::InsertCallAt(pc, lazy_deopt_jump);
+  const Instructions& instrs =
+      Instructions::Handle(optimized_code.instructions());
+  {
+    WritableInstructionsScope writable(instrs.EntryPoint(), instrs.size());
+    CodePatcher::InsertCallAt(pc, lazy_deopt_jump);
+  }
   if (FLAG_trace_patching) {
     const String& name = String::Handle(function.name());
     OS::PrintErr("InsertCallAt: %" Px " to %" Px " for %s\n", pc,
                  lazy_deopt_jump, name.ToCString());
   }
   // Mark code as dead (do not GC its embedded objects).
   optimized_code.set_is_alive(false);
 }
 
 
@@ skipping 180 matching lines @@
 // of the given value.
 //   Arg0: Field object;
 //   Arg1: Value that is being stored.
 DEFINE_RUNTIME_ENTRY(UpdateFieldCid, 2) {
   const Field& field = Field::CheckedHandle(arguments.ArgAt(0));
   const Object& value = Object::Handle(arguments.ArgAt(1));
   field.UpdateGuardedCidAndLength(value);
 }
 
 }  // namespace dart