dom/base/nsJSUtils.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=2 sw=2 et tw=78: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /**
   8  * This is not a generated file. It contains common utility functions
   9  * invoked from the JavaScript code generated from IDL interfaces.
  10  * The goal of the utility functions is to cut down on the size of
  11  * the generated code itself.
  12  */
  13
  14 #include "nsJSUtils.h"
  15 #include "jsapi.h"
  16 #include "js/OldDebugAPI.h"
  17 #include "jsfriendapi.h"
  18 #include "nsIScriptContext.h"
  19 #include "nsIScriptGlobalObject.h"
  20 #include "nsIXPConnect.h"
  21 #include "nsCOMPtr.h"
  22 #include "nsIScriptSecurityManager.h"
  23 #include "nsPIDOMWindow.h"
  24 #include "GeckoProfiler.h"
  25 #include "nsDOMJSUtils.h" // for GetScriptContextFromJSContext
  26 #include "nsJSPrincipals.h"
  27 #include "xpcpublic.h"
  28 #include "nsContentUtils.h"
  29 #include "nsGlobalWindow.h"
  30
  31 bool
  32 nsJSUtils::GetCallingLocation(JSContext* aContext, const char* *aFilename,
  33                               uint32_t* aLineno)
  34 {
  35   JS::AutoFilename filename;
  36   unsigned lineno = 0;
  37
  38   if (!JS::DescribeScriptedCaller(aContext, &filename, &lineno)) {
  39     return false;
  40   }
  41
  42   *aFilename = filename.get();
  43   *aLineno = lineno;
  44
  45   return true;
  46 }
  47
  48 nsIScriptGlobalObject *
  49 nsJSUtils::GetStaticScriptGlobal(JSObject* aObj)
  50 {
  51   if (!aObj)
  52     return nullptr;
  53   return xpc::WindowGlobalOrNull(aObj);
  54 }
  55
  56 nsIScriptContext *
  57 nsJSUtils::GetStaticScriptContext(JSObject* aObj)
  58 {
  59   nsIScriptGlobalObject *nativeGlobal = GetStaticScriptGlobal(aObj);
  60   if (!nativeGlobal)
  61     return nullptr;
  62
  63   return nativeGlobal->GetScriptContext();
  64 }
  65
  66 uint64_t
  67 nsJSUtils::GetCurrentlyRunningCodeInnerWindowID(JSContext *aContext)
  68 {
  69   if (!aContext)
  70     return 0;
  71
  72   uint64_t innerWindowID = 0;
  73
  74   JSObject *jsGlobal = JS::CurrentGlobalOrNull(aContext);
  75   if (jsGlobal) {
  76     nsIScriptGlobalObject *scriptGlobal = GetStaticScriptGlobal(jsGlobal);
  77     if (scriptGlobal) {
  78       nsCOMPtr<nsPIDOMWindow> win = do_QueryInterface(scriptGlobal);
  79       if (win)
  80         innerWindowID = win->WindowID();
  81     }
  82   }
  83
  84   return innerWindowID;
  85 }
  86
  87 void
  88 nsJSUtils::ReportPendingException(JSContext *aContext)
  89 {
  90   if (JS_IsExceptionPending(aContext)) {
  91     bool saved = JS_SaveFrameChain(aContext);
  92     {
  93       // JS_SaveFrameChain set the compartment of aContext to null, so we need
  94       // to enter a compartment.  The question is, which one? We don't want to
  95       // enter the original compartment of aContext (or the compartment of the
  96       // current exception on aContext, for that matter) because when we
  97       // JS_ReportPendingException the JS engine can try to duck-type the
  98       // exception and produce a JSErrorReport.  It will then pass that
  99       // JSErrorReport to the error reporter on aContext, which might expose
 100       // information from it to script via onerror handlers.  So it's very
 101       // important that the duck typing happen in the same compartment as the
 102       // onerror handler.  In practice, that's the compartment of the window (or
 103       // otherwise default global) of aContext, so use that here.
 104       nsIScriptContext* scx = GetScriptContextFromJSContext(aContext);
 105       JS::Rooted<JSObject*> scope(aContext);
 106       scope = scx ? scx->GetWindowProxy() : nullptr;
 107       if (!scope) {
 108         // The SafeJSContext has no default object associated with it.
 109         MOZ_ASSERT(NS_IsMainThread());
 110         MOZ_ASSERT(aContext == nsContentUtils::GetSafeJSContext());
 111         scope = xpc::UnprivilegedJunkScope(); // Usage approved by bholley
 112       }
 113       JSAutoCompartment ac(aContext, scope);
 114       JS_ReportPendingException(aContext);
 115     }
 116     if (saved) {
 117       JS_RestoreFrameChain(aContext);
 118     }
 119   }
 120 }
 121
 122 nsresult
 123 nsJSUtils::CompileFunction(JSContext* aCx,
 124                            JS::Handle<JSObject*> aTarget,
 125                            JS::CompileOptions& aOptions,
 126                            const nsACString& aName,
 127                            uint32_t aArgCount,
 128                            const char** aArgArray,
 129                            const nsAString& aBody,
 130                            JSObject** aFunctionObject)
 131 {
 132   MOZ_ASSERT(js::GetEnterCompartmentDepth(aCx) > 0);
 133   MOZ_ASSERT_IF(aTarget, js::IsObjectInContextCompartment(aTarget, aCx));
 134   MOZ_ASSERT_IF(aOptions.versionSet, aOptions.version != JSVERSION_UNKNOWN);
 135   mozilla::DebugOnly<nsIScriptContext*> ctx = GetScriptContextFromJSContext(aCx);
 136   MOZ_ASSERT_IF(ctx, ctx->IsContextInitialized());
 137
 138   // Do the junk Gecko is supposed to do before calling into JSAPI.
 139   if (aTarget) {
 140     JS::ExposeObjectToActiveJS(aTarget);
 141   }
 142
 143   // Compile.
 144   JS::Rooted<JSFunction*> fun(aCx);
 145   if (!JS::CompileFunction(aCx, aTarget, aOptions,
 146                            PromiseFlatCString(aName).get(),
 147                            aArgCount, aArgArray,
 148                            PromiseFlatString(aBody).get(),
 149                            aBody.Length(), &fun))
 150   {
 151     ReportPendingException(aCx);
 152     return NS_ERROR_FAILURE;
 153   }
 154
 155   *aFunctionObject = JS_GetFunctionObject(fun);
 156   return NS_OK;
 157 }
 158
 159 nsresult
 160 nsJSUtils::EvaluateString(JSContext* aCx,
 161                           const nsAString& aScript,
 162                           JS::Handle<JSObject*> aScopeObject,
 163                           JS::CompileOptions& aCompileOptions,
 164                           const EvaluateOptions& aEvaluateOptions,
 165                           JS::MutableHandle<JS::Value> aRetValue,
 166                           void **aOffThreadToken)
 167 {
 168   const nsPromiseFlatString& flatScript = PromiseFlatString(aScript);
 169   JS::SourceBufferHolder srcBuf(flatScript.get(), aScript.Length(),
 170                                 JS::SourceBufferHolder::NoOwnership);
 171   return EvaluateString(aCx, srcBuf, aScopeObject, aCompileOptions,
 172                         aEvaluateOptions, aRetValue, aOffThreadToken);
 173 }
 174
 175 nsresult
 176 nsJSUtils::EvaluateString(JSContext* aCx,
 177                           JS::SourceBufferHolder& aSrcBuf,
 178                           JS::Handle<JSObject*> aScopeObject,
 179                           JS::CompileOptions& aCompileOptions,
 180                           const EvaluateOptions& aEvaluateOptions,
 181                           JS::MutableHandle<JS::Value> aRetValue,
 182                           void **aOffThreadToken)
 183 {
 184   PROFILER_LABEL("nsJSUtils", "EvaluateString",
 185     js::ProfileEntry::Category::JS);
 186
 187   MOZ_ASSERT_IF(aCompileOptions.versionSet,
 188                 aCompileOptions.version != JSVERSION_UNKNOWN);
 189   MOZ_ASSERT_IF(aEvaluateOptions.coerceToString, aEvaluateOptions.needResult);
 190   MOZ_ASSERT_IF(!aEvaluateOptions.reportUncaught, aEvaluateOptions.needResult);
 191   MOZ_ASSERT(aCx == nsContentUtils::GetCurrentJSContext());
 192   MOZ_ASSERT(aSrcBuf.get());
 193
 194   // Unfortunately, the JS engine actually compiles scripts with a return value
 195   // in a different, less efficient way.  Furthermore, it can't JIT them in many
 196   // cases.  So we need to be explicitly told whether the caller cares about the
 197   // return value.  Callers can do this by calling the other overload of
 198   // EvaluateString() which calls this function with aEvaluateOptions.needResult
 199   // set to false.
 200   aRetValue.setUndefined();
 201
 202   JS::ExposeObjectToActiveJS(aScopeObject);
 203   nsAutoMicroTask mt;
 204   nsresult rv = NS_OK;
 205
 206   bool ok = false;
 207   nsIScriptSecurityManager* ssm = nsContentUtils::GetSecurityManager();
 208   NS_ENSURE_TRUE(ssm->ScriptAllowed(js::GetGlobalForObjectCrossCompartment(aScopeObject)), NS_OK);
 209
 210   mozilla::Maybe<AutoDontReportUncaught> dontReport;
 211   if (!aEvaluateOptions.reportUncaught) {
 212     // We need to prevent AutoLastFrameCheck from reporting and clearing
 213     // any pending exceptions.
 214     dontReport.emplace(aCx);
 215   }
 216
 217   // Scope the JSAutoCompartment so that we can later wrap the return value
 218   // into the caller's cx.
 219   {
 220     JSAutoCompartment ac(aCx, aScopeObject);
 221
 222     JS::Rooted<JSObject*> rootedScope(aCx, aScopeObject);
 223     if (aOffThreadToken) {
 224       JS::Rooted<JSScript*>
 225         script(aCx, JS::FinishOffThreadScript(aCx, JS_GetRuntime(aCx), *aOffThreadToken));
 226       *aOffThreadToken = nullptr; // Mark the token as having been finished.
 227       if (script) {
 228         if (aEvaluateOptions.needResult) {
 229           ok = JS_ExecuteScript(aCx, rootedScope, script, aRetValue);
 230         } else {
 231           ok = JS_ExecuteScript(aCx, rootedScope, script);
 232         }
 233       } else {
 234         ok = false;
 235       }
 236     } else {
 237       if (aEvaluateOptions.needResult) {
 238         ok = JS::Evaluate(aCx, rootedScope, aCompileOptions,
 239                           aSrcBuf, aRetValue);
 240       } else {
 241         ok = JS::Evaluate(aCx, rootedScope, aCompileOptions,
 242                           aSrcBuf);
 243       }
 244     }
 245
 246     if (ok && aEvaluateOptions.coerceToString && !aRetValue.isUndefined()) {
 247       JS::Rooted<JS::Value> value(aCx, aRetValue);
 248       JSString* str = JS::ToString(aCx, value);
 249       ok = !!str;
 250       aRetValue.set(ok ? JS::StringValue(str) : JS::UndefinedValue());
 251     }
 252   }
 253
 254   if (!ok) {
 255     if (aEvaluateOptions.reportUncaught) {
 256       ReportPendingException(aCx);
 257       if (aEvaluateOptions.needResult) {
 258         aRetValue.setUndefined();
 259       }
 260     } else {
 261       rv = JS_IsExceptionPending(aCx) ? NS_ERROR_FAILURE
 262                                       : NS_ERROR_OUT_OF_MEMORY;
 263       JS::Rooted<JS::Value> exn(aCx);
 264       JS_GetPendingException(aCx, &exn);
 265       if (aEvaluateOptions.needResult) {
 266         aRetValue.set(exn);
 267       }
 268       JS_ClearPendingException(aCx);
 269     }
 270   }
 271
 272   // Wrap the return value into whatever compartment aCx was in.
 273   if (aEvaluateOptions.needResult) {
 274     JS::Rooted<JS::Value> v(aCx, aRetValue);
 275     if (!JS_WrapValue(aCx, &v)) {
 276       return NS_ERROR_OUT_OF_MEMORY;
 277     }
 278     aRetValue.set(v);
 279   }
 280   return rv;
 281 }
 282
 283 nsresult
 284 nsJSUtils::EvaluateString(JSContext* aCx,
 285                           const nsAString& aScript,
 286                           JS::Handle<JSObject*> aScopeObject,
 287                           JS::CompileOptions& aCompileOptions,
 288                           void **aOffThreadToken)
 289 {
 290   EvaluateOptions options;
 291   options.setNeedResult(false);
 292   JS::RootedValue unused(aCx);
 293   return EvaluateString(aCx, aScript, aScopeObject, aCompileOptions,
 294                         options, &unused, aOffThreadToken);
 295 }
 296
 297 nsresult
 298 nsJSUtils::EvaluateString(JSContext* aCx,
 299                           JS::SourceBufferHolder& aSrcBuf,
 300                           JS::Handle<JSObject*> aScopeObject,
 301                           JS::CompileOptions& aCompileOptions,
 302                           void **aOffThreadToken)
 303 {
 304   EvaluateOptions options;
 305   options.setNeedResult(false);
 306   JS::RootedValue unused(aCx);
 307   return EvaluateString(aCx, aSrcBuf, aScopeObject, aCompileOptions,
 308                         options, &unused, aOffThreadToken);
 309 }
 310
 311 //
 312 // nsDOMJSUtils.h
 313 //
 314
 315 JSObject* GetDefaultScopeFromJSContext(JSContext *cx)
 316 {
 317   // DOM JSContexts don't store their default compartment object on
 318   // the cx, so in those cases we need to fetch it via the scx
 319   // instead.
 320   nsIScriptContext *scx = GetScriptContextFromJSContext(cx);
 321   return  scx ? scx->GetWindowProxy() : nullptr;
 322 }