[d8] enable os.system only when requested

os.system uses fork(), which is not supported by ASAN/LSAN. Some fuzz tests
consist of js code that randomly picks properties and functions and calls them.
Sometimes, this combination means ASAN will report false positives.

Bug: chromium:740361
Change-Id: Id8d517263251a1fe88abadd33b0225c664b00498
Reviewed-on: https://chromium-review.googlesource.com/580313Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46876}

src/d8-posix.cc

@@ -749,9 +749,11 @@ void Shell::UnsetEnvironment(const v8::FunctionCallbackInfo<v8::Value>& args) {
 
 
 void Shell::AddOSMethods(Isolate* isolate, Local<ObjectTemplate> os_templ) {
-  os_templ->Set(String::NewFromUtf8(isolate, "system", NewStringType::kNormal)
-                    .ToLocalChecked(),
-                FunctionTemplate::New(isolate, System));
+  if (options.enable_os_system) {
+    os_templ->Set(String::NewFromUtf8(isolate, "system", NewStringType::kNormal)
+                      .ToLocalChecked(),
+                  FunctionTemplate::New(isolate, System));
+  }
   os_templ->Set(String::NewFromUtf8(isolate, "chdir", NewStringType::kNormal)
                     .ToLocalChecked(),
                 FunctionTemplate::New(isolate, ChangeDirectory));

src/d8.cc

-// Copyright 2012 the V8 project authors. All rights reserved.
+/// Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -2717,6 +2717,9 @@ bool Shell::SetOptions(int argc, char* argv[]) {
     } else if (strcmp(argv[i], "--disable-in-process-stack-traces") == 0) {
       options.disable_in_process_stack_traces = true;
       argv[i] = NULL;
+    } else if (strcmp(argv[i], "--enable-os-system") == 0) {
+      options.enable_os_system = true;
+      argv[i] = NULL;
     }
   }
 

src/d8.h

@@ -337,6 +337,7 @@ class ShellOptions {
   const char* trace_config;
   const char* lcov_file;
   bool disable_in_process_stack_traces;
+  bool enable_os_system = false;
 };
 
 class Shell : public i::AllStatic {

tools/linux-tick-processor

@@ -33,7 +33,8 @@ if [ ! -x "$d8_exec" ]; then
 fi
 
 # nm spits out 'no symbols found' messages to stderr.
-cat $log_file | $d8_exec $tools_path/splaytree.js $tools_path/codemap.js \
+cat $log_file | $d8_exec --enable-os-system \
+  $tools_path/splaytree.js $tools_path/codemap.js \
   $tools_path/csvparser.js $tools_path/consarray.js \
   $tools_path/profile.js $tools_path/profile_view.js \
   $tools_path/logreader.js $tools_path/tickprocessor.js \