js/src/builtin/Eval.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   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 #include "builtin/Eval.h"
   8
   9 #include "mozilla/HashFunctions.h"
  10 #include "mozilla/Range.h"
  11
  12 #include "frontend/BytecodeCompiler.h"  // frontend::CompileEvalScript
  13 #include "gc/HashUtil.h"
  14 #include "js/CompilationAndEvaluation.h"
  15 #include "js/friend/ErrorMessages.h"   // js::GetErrorMessage, JSMSG_*
  16 #include "js/friend/JSMEnvironment.h"  // JS::NewJSMEnvironment, JS::ExecuteInJSMEnvironment, JS::GetJSMEnvironmentOfScriptedCaller, JS::IsJSMEnvironment
  17 #include "js/friend/WindowProxy.h"     // js::IsWindowProxy
  18 #include "js/SourceText.h"
  19 #include "js/StableStringChars.h"
  20 #include "vm/EnvironmentObject.h"
  21 #include "vm/FrameIter.h"
  22 #include "vm/GlobalObject.h"
  23 #include "vm/Interpreter.h"
  24 #include "vm/JSContext.h"
  25 #include "vm/JSONParser.h"
  26
  27 #include "gc/Marking-inl.h"
  28 #include "vm/EnvironmentObject-inl.h"
  29 #include "vm/JSContext-inl.h"
  30 #include "vm/Stack-inl.h"
  31
  32 using namespace js;
  33
  34 using mozilla::AddToHash;
  35 using mozilla::HashString;
  36 using mozilla::RangedPtr;
  37
  38 using JS::AutoCheckCannotGC;
  39 using JS::AutoStableStringChars;
  40 using JS::CompileOptions;
  41 using JS::SourceOwnership;
  42 using JS::SourceText;
  43
  44 // We should be able to assert this for *any* fp->environmentChain().
  45 static void AssertInnerizedEnvironmentChain(JSContext* cx, JSObject& env) {
  46 #ifdef DEBUG
  47   RootedObject obj(cx);
  48   for (obj = &env; obj; obj = obj->enclosingEnvironment()) {
  49     MOZ_ASSERT(!IsWindowProxy(obj));
  50   }
  51 #endif
  52 }
  53
  54 static bool IsEvalCacheCandidate(JSScript* script) {
  55   if (!script->isDirectEvalInFunction()) {
  56     return false;
  57   }
  58
  59   // Make sure there are no inner objects (which may be used directly by script
  60   // and clobbered) or inner functions (which may have wrong scope).
  61   for (JS::GCCellPtr gcThing : script->gcthings()) {
  62     if (gcThing.is<JSObject>()) {
  63       return false;
  64     }
  65   }
  66
  67   return true;
  68 }
  69
  70 /* static */
  71 HashNumber EvalCacheHashPolicy::hash(const EvalCacheLookup& l) {
  72   HashNumber hash = HashStringChars(l.str);
  73   return AddToHash(hash, l.callerScript.get(), l.pc);
  74 }
  75
  76 /* static */
  77 bool EvalCacheHashPolicy::match(const EvalCacheEntry& cacheEntry,
  78                                 const EvalCacheLookup& l) {
  79   MOZ_ASSERT(IsEvalCacheCandidate(cacheEntry.script));
  80
  81   return EqualStrings(cacheEntry.str, l.str) &&
  82          cacheEntry.callerScript == l.callerScript && cacheEntry.pc == l.pc;
  83 }
  84
  85 // Add the script to the eval cache when EvalKernel is finished
  86 class EvalScriptGuard {
  87   JSContext* cx_;
  88   Rooted<JSScript*> script_;
  89
  90   /* These fields are only valid if lookup_.str is non-nullptr. */
  91   EvalCacheLookup lookup_;
  92   mozilla::Maybe<DependentAddPtr<EvalCache>> p_;
  93
  94   Rooted<JSLinearString*> lookupStr_;
  95
  96  public:
  97   explicit EvalScriptGuard(JSContext* cx)
  98       : cx_(cx), script_(cx), lookup_(cx), lookupStr_(cx) {}
  99
 100   ~EvalScriptGuard() {
 101     if (script_ && !cx_->isExceptionPending()) {
 102       script_->cacheForEval();
 103       EvalCacheEntry cacheEntry = {lookupStr_, script_, lookup_.callerScript,
 104                                    lookup_.pc};
 105       lookup_.str = lookupStr_;
 106       if (lookup_.str && IsEvalCacheCandidate(script_)) {
 107         // Ignore failure to add cache entry.
 108         if (!p_->add(cx_, cx_->caches().evalCache, lookup_, cacheEntry)) {
 109           cx_->recoverFromOutOfMemory();
 110         }
 111       }
 112     }
 113   }
 114
 115   void lookupInEvalCache(JSLinearString* str, JSScript* callerScript,
 116                          jsbytecode* pc) {
 117     lookupStr_ = str;
 118     lookup_.str = str;
 119     lookup_.callerScript = callerScript;
 120     lookup_.pc = pc;
 121     p_.emplace(cx_, cx_->caches().evalCache, lookup_);
 122     if (*p_) {
 123       script_ = (*p_)->script;
 124       p_->remove(cx_, cx_->caches().evalCache, lookup_);
 125     }
 126   }
 127
 128   void setNewScript(JSScript* script) {
 129     // JSScript::fullyInitFromStencil has already called js_CallNewScriptHook.
 130     MOZ_ASSERT(!script_ && script);
 131     script_ = script;
 132   }
 133
 134   bool foundScript() { return !!script_; }
 135
 136   HandleScript script() {
 137     MOZ_ASSERT(script_);
 138     return script_;
 139   }
 140 };
 141
 142 enum class EvalJSONResult { Failure, Success, NotJSON };
 143
 144 template <typename CharT>
 145 static bool EvalStringMightBeJSON(const mozilla::Range<const CharT> chars) {
 146   // If the eval string starts with '(' or '[' and ends with ')' or ']', it
 147   // may be JSON.  Try the JSON parser first because it's much faster.  If
 148   // the eval string isn't JSON, JSON parsing will probably fail quickly, so
 149   // little time will be lost.
 150   size_t length = chars.length();
 151   if (length < 2) {
 152     return false;
 153   }
 154
 155   // It used to be that strings in JavaScript forbid U+2028 LINE SEPARATOR
 156   // and U+2029 PARAGRAPH SEPARATOR, so something like
 157   //
 158   //   eval("['" + "\u2028" + "']");
 159   //
 160   // i.e. an array containing a string with a line separator in it, *would*
 161   // be JSON but *would not* be valid JavaScript.  Handing such a string to
 162   // the JSON parser would then fail to recognize a syntax error.  As of
 163   // <https://tc39.github.io/proposal-json-superset/> JavaScript strings may
 164   // contain these two code points, so it's safe to JSON-parse eval strings
 165   // that contain them.
 166
 167   CharT first = chars[0], last = chars[length - 1];
 168   return (first == '[' && last == ']') || (first == '(' && last == ')');
 169 }
 170
 171 template <typename CharT>
 172 static EvalJSONResult ParseEvalStringAsJSON(
 173     JSContext* cx, const mozilla::Range<const CharT> chars,
 174     MutableHandleValue rval) {
 175   size_t len = chars.length();
 176   MOZ_ASSERT((chars[0] == '(' && chars[len - 1] == ')') ||
 177              (chars[0] == '[' && chars[len - 1] == ']'));
 178
 179   auto jsonChars = (chars[0] == '[') ? chars
 180                                      : mozilla::Range<const CharT>(
 181                                            chars.begin().get() + 1U, len - 2);
 182
 183   Rooted<JSONParser<CharT>> parser(
 184       cx, cx, jsonChars, JSONParser<CharT>::ParseType::AttemptForEval);
 185   if (!parser.parse(rval)) {
 186     return EvalJSONResult::Failure;
 187   }
 188
 189   return rval.isUndefined() ? EvalJSONResult::NotJSON : EvalJSONResult::Success;
 190 }
 191
 192 static EvalJSONResult TryEvalJSON(JSContext* cx, JSLinearString* str,
 193                                   MutableHandleValue rval) {
 194   if (str->hasLatin1Chars()) {
 195     AutoCheckCannotGC nogc;
 196     if (!EvalStringMightBeJSON(str->latin1Range(nogc))) {
 197       return EvalJSONResult::NotJSON;
 198     }
 199   } else {
 200     AutoCheckCannotGC nogc;
 201     if (!EvalStringMightBeJSON(str->twoByteRange(nogc))) {
 202       return EvalJSONResult::NotJSON;
 203     }
 204   }
 205
 206   AutoStableStringChars linearChars(cx);
 207   if (!linearChars.init(cx, str)) {
 208     return EvalJSONResult::Failure;
 209   }
 210
 211   return linearChars.isLatin1()
 212              ? ParseEvalStringAsJSON(cx, linearChars.latin1Range(), rval)
 213              : ParseEvalStringAsJSON(cx, linearChars.twoByteRange(), rval);
 214 }
 215
 216 enum EvalType { DIRECT_EVAL, INDIRECT_EVAL };
 217
 218 // 18.2.1.1 PerformEval
 219 //
 220 // Common code implementing direct and indirect eval.
 221 //
 222 // Evaluate v, if it is a string, in the context of the given calling
 223 // frame, with the provided scope chain, with the semantics of either a direct
 224 // or indirect eval (see ES5 10.4.2).  If this is an indirect eval, env
 225 // must be the global lexical environment.
 226 //
 227 // On success, store the completion value in call.rval and return true.
 228 static bool EvalKernel(JSContext* cx, HandleValue v, EvalType evalType,
 229                        AbstractFramePtr caller, HandleObject env,
 230                        jsbytecode* pc, MutableHandleValue vp) {
 231   MOZ_ASSERT((evalType == INDIRECT_EVAL) == !caller);
 232   MOZ_ASSERT((evalType == INDIRECT_EVAL) == !pc);
 233   MOZ_ASSERT_IF(evalType == INDIRECT_EVAL, IsGlobalLexicalEnvironment(env));
 234   AssertInnerizedEnvironmentChain(cx, *env);
 235
 236   // Step 2.
 237   if (!v.isString()) {
 238     vp.set(v);
 239     return true;
 240   }
 241
 242   // Steps 3-4.
 243   RootedString str(cx, v.toString());
 244   if (!cx->isRuntimeCodeGenEnabled(JS::RuntimeCode::JS, str)) {
 245     JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
 246                               JSMSG_CSP_BLOCKED_EVAL);
 247     return false;
 248   }
 249
 250   // Step 5 ff.
 251
 252   // Per ES5, indirect eval runs in the global scope. (eval is specified this
 253   // way so that the compiler can make assumptions about what bindings may or
 254   // may not exist in the current frame if it doesn't see 'eval'.)
 255   MOZ_ASSERT_IF(
 256       evalType != DIRECT_EVAL,
 257       cx->global() == &env->as<GlobalLexicalEnvironmentObject>().global());
 258
 259   Rooted<JSLinearString*> linearStr(cx, str->ensureLinear(cx));
 260   if (!linearStr) {
 261     return false;
 262   }
 263
 264   RootedScript callerScript(cx, caller ? caller.script() : nullptr);
 265   EvalJSONResult ejr = TryEvalJSON(cx, linearStr, vp);
 266   if (ejr != EvalJSONResult::NotJSON) {
 267     return ejr == EvalJSONResult::Success;
 268   }
 269
 270   EvalScriptGuard esg(cx);
 271
 272   if (evalType == DIRECT_EVAL && caller.isFunctionFrame()) {
 273     esg.lookupInEvalCache(linearStr, callerScript, pc);
 274   }
 275
 276   if (!esg.foundScript()) {
 277     RootedScript maybeScript(cx);
 278     uint32_t lineno;
 279     const char* filename;
 280     bool mutedErrors;
 281     uint32_t pcOffset;
 282     if (evalType == DIRECT_EVAL) {
 283       DescribeScriptedCallerForDirectEval(cx, callerScript, pc, &filename,
 284                                           &lineno, &pcOffset, &mutedErrors);
 285       maybeScript = callerScript;
 286     } else {
 287       DescribeScriptedCallerForCompilation(cx, &maybeScript, &filename, &lineno,
 288                                            &pcOffset, &mutedErrors);
 289     }
 290
 291     const char* introducerFilename = filename;
 292     if (maybeScript && maybeScript->scriptSource()->introducerFilename()) {
 293       introducerFilename = maybeScript->scriptSource()->introducerFilename();
 294     }
 295
 296     Rooted<Scope*> enclosing(cx);
 297     if (evalType == DIRECT_EVAL) {
 298       enclosing = callerScript->innermostScope(pc);
 299     } else {
 300       enclosing = &cx->global()->emptyGlobalScope();
 301     }
 302
 303     CompileOptions options(cx);
 304     options.setIsRunOnce(true)
 305         .setNoScriptRval(false)
 306         .setMutedErrors(mutedErrors)
 307         .setDeferDebugMetadata();
 308
 309     RootedScript introScript(cx);
 310
 311     if (evalType == DIRECT_EVAL && IsStrictEvalPC(pc)) {
 312       options.setForceStrictMode();
 313     }
 314
 315     if (introducerFilename) {
 316       options.setFileAndLine(filename, 1);
 317       options.setIntroductionInfo(introducerFilename, "eval", lineno, pcOffset);
 318       introScript = maybeScript;
 319     } else {
 320       options.setFileAndLine("eval", 1);
 321       options.setIntroductionType("eval");
 322     }
 323     options.setNonSyntacticScope(
 324         enclosing->hasOnChain(ScopeKind::NonSyntactic));
 325
 326     AutoStableStringChars linearChars(cx);
 327     if (!linearChars.initTwoByte(cx, linearStr)) {
 328       return false;
 329     }
 330
 331     SourceText<char16_t> srcBuf;
 332     if (!srcBuf.initMaybeBorrowed(cx, linearChars)) {
 333       return false;
 334     }
 335
 336     RootedScript script(
 337         cx, frontend::CompileEvalScript(cx, options, srcBuf, enclosing, env));
 338     if (!script) {
 339       return false;
 340     }
 341
 342     RootedValue undefValue(cx);
 343     JS::InstantiateOptions instantiateOptions(options);
 344     if (!JS::UpdateDebugMetadata(cx, script, instantiateOptions, undefValue,
 345                                  nullptr, introScript, maybeScript)) {
 346       return false;
 347     }
 348
 349     esg.setNewScript(script);
 350   }
 351
 352   return ExecuteKernel(cx, esg.script(), env, NullFramePtr() /* evalInFrame */,
 353                        vp);
 354 }
 355
 356 bool js::IndirectEval(JSContext* cx, unsigned argc, Value* vp) {
 357   CallArgs args = CallArgsFromVp(argc, vp);
 358
 359   RootedObject globalLexical(cx, &cx->global()->lexicalEnvironment());
 360
 361   // Note we'll just pass |undefined| here, then return it directly (or throw
 362   // if runtime codegen is disabled), if no argument is provided.
 363   return EvalKernel(cx, args.get(0), INDIRECT_EVAL, NullFramePtr(),
 364                     globalLexical, nullptr, args.rval());
 365 }
 366
 367 bool js::DirectEval(JSContext* cx, HandleValue v, MutableHandleValue vp) {
 368   // Direct eval can assume it was called from an interpreted or baseline frame.
 369   ScriptFrameIter iter(cx);
 370   AbstractFramePtr caller = iter.abstractFramePtr();
 371
 372   MOZ_ASSERT(JSOp(*iter.pc()) == JSOp::Eval ||
 373              JSOp(*iter.pc()) == JSOp::StrictEval ||
 374              JSOp(*iter.pc()) == JSOp::SpreadEval ||
 375              JSOp(*iter.pc()) == JSOp::StrictSpreadEval);
 376   MOZ_ASSERT(caller.realm() == caller.script()->realm());
 377
 378   RootedObject envChain(cx, caller.environmentChain());
 379   return EvalKernel(cx, v, DIRECT_EVAL, caller, envChain, iter.pc(), vp);
 380 }
 381
 382 bool js::IsAnyBuiltinEval(JSFunction* fun) {
 383   return fun->maybeNative() == IndirectEval;
 384 }
 385
 386 static bool ExecuteInExtensibleLexicalEnvironment(
 387     JSContext* cx, HandleScript scriptArg,
 388     Handle<ExtensibleLexicalEnvironmentObject*> env) {
 389   CHECK_THREAD(cx);
 390   cx->check(env);
 391   cx->check(scriptArg);
 392   MOZ_RELEASE_ASSERT(scriptArg->hasNonSyntacticScope());
 393
 394   RootedValue rval(cx);
 395   return ExecuteKernel(cx, scriptArg, env, NullFramePtr() /* evalInFrame */,
 396                        &rval);
 397 }
 398
 399 JS_PUBLIC_API bool js::ExecuteInFrameScriptEnvironment(
 400     JSContext* cx, HandleObject objArg, HandleScript scriptArg,
 401     MutableHandleObject envArg) {
 402   RootedObject varEnv(cx, NonSyntacticVariablesObject::create(cx));
 403   if (!varEnv) {
 404     return false;
 405   }
 406
 407   RootedObjectVector envChain(cx);
 408   if (!envChain.append(objArg)) {
 409     return false;
 410   }
 411
 412   RootedObject env(cx);
 413   if (!js::CreateObjectsForEnvironmentChain(cx, envChain, varEnv, &env)) {
 414     return false;
 415   }
 416
 417   // Create lexical environment with |this| == objArg, which should be a Gecko
 418   // MessageManager.
 419   // NOTE: This is required behavior for Gecko FrameScriptLoader, where some
 420   // callers try to bind methods from the message manager in their scope chain
 421   // to |this|, and will fail if it is not bound to a message manager.
 422   ObjectRealm& realm = ObjectRealm::get(varEnv);
 423   Rooted<NonSyntacticLexicalEnvironmentObject*> lexicalEnv(
 424       cx,
 425       realm.getOrCreateNonSyntacticLexicalEnvironment(cx, env, varEnv, objArg));
 426   if (!lexicalEnv) {
 427     return false;
 428   }
 429
 430   if (!ExecuteInExtensibleLexicalEnvironment(cx, scriptArg, lexicalEnv)) {
 431     return false;
 432   }
 433
 434   envArg.set(lexicalEnv);
 435   return true;
 436 }
 437
 438 JS_PUBLIC_API JSObject* JS::NewJSMEnvironment(JSContext* cx) {
 439   RootedObject varEnv(cx, NonSyntacticVariablesObject::create(cx));
 440   if (!varEnv) {
 441     return nullptr;
 442   }
 443
 444   // Force the NonSyntacticLexicalEnvironmentObject to be created.
 445   ObjectRealm& realm = ObjectRealm::get(varEnv);
 446   MOZ_ASSERT(!realm.getNonSyntacticLexicalEnvironment(varEnv));
 447   if (!realm.getOrCreateNonSyntacticLexicalEnvironment(cx, varEnv)) {
 448     return nullptr;
 449   }
 450
 451   return varEnv;
 452 }
 453
 454 JS_PUBLIC_API bool JS::ExecuteInJSMEnvironment(JSContext* cx,
 455                                                HandleScript scriptArg,
 456                                                HandleObject varEnv) {
 457   RootedObjectVector emptyChain(cx);
 458   return ExecuteInJSMEnvironment(cx, scriptArg, varEnv, emptyChain);
 459 }
 460
 461 JS_PUBLIC_API bool JS::ExecuteInJSMEnvironment(JSContext* cx,
 462                                                HandleScript scriptArg,
 463                                                HandleObject varEnv,
 464                                                HandleObjectVector targetObj) {
 465   cx->check(varEnv);
 466   MOZ_ASSERT(
 467       ObjectRealm::get(varEnv).getNonSyntacticLexicalEnvironment(varEnv));
 468   MOZ_DIAGNOSTIC_ASSERT(scriptArg->noScriptRval());
 469
 470   Rooted<ExtensibleLexicalEnvironmentObject*> env(
 471       cx, ExtensibleLexicalEnvironmentObject::forVarEnvironment(varEnv));
 472
 473   // If the Gecko subscript loader specifies target objects, we need to add
 474   // them to the environment. These are added after the NSVO environment.
 475   if (!targetObj.empty()) {
 476     // The environment chain will be as follows:
 477     //      GlobalObject / BackstagePass
 478     //      GlobalLexicalEnvironmentObject[this=global]
 479     //      NonSyntacticVariablesObject (the JSMEnvironment)
 480     //      NonSyntacticLexicalEnvironmentObject[this=nsvo]
 481     //      WithEnvironmentObject[target=targetObj]
 482     //      NonSyntacticLexicalEnvironmentObject[this=targetObj] (*)
 483     //
 484     //  (*) This environment intercepts JSOp::GlobalThis.
 485
 486     // Wrap the target objects in WithEnvironments.
 487     RootedObject envChain(cx);
 488     if (!js::CreateObjectsForEnvironmentChain(cx, targetObj, env, &envChain)) {
 489       return false;
 490     }
 491
 492     // See CreateNonSyntacticEnvironmentChain
 493     if (!JSObject::setQualifiedVarObj(cx, envChain)) {
 494       return false;
 495     }
 496
 497     // Create an extensible lexical environment for the target object.
 498     env = ObjectRealm::get(envChain).getOrCreateNonSyntacticLexicalEnvironment(
 499         cx, envChain);
 500     if (!env) {
 501       return false;
 502     }
 503   }
 504
 505   return ExecuteInExtensibleLexicalEnvironment(cx, scriptArg, env);
 506 }
 507
 508 JS_PUBLIC_API JSObject* JS::GetJSMEnvironmentOfScriptedCaller(JSContext* cx) {
 509   FrameIter iter(cx);
 510   if (iter.done()) {
 511     return nullptr;
 512   }
 513
 514   // WASM frames don't always provide their environment, but we also shouldn't
 515   // expect to see any calling into here.
 516   MOZ_RELEASE_ASSERT(!iter.isWasm());
 517
 518   RootedObject env(cx, iter.environmentChain(cx));
 519   while (env && !env->is<NonSyntacticVariablesObject>()) {
 520     env = env->enclosingEnvironment();
 521   }
 522
 523   return env;
 524 }
 525
 526 JS_PUBLIC_API bool JS::IsJSMEnvironment(JSObject* obj) {
 527   // NOTE: This also returns true if the NonSyntacticVariablesObject was
 528   // created for reasons other than the JSM loader.
 529   return obj->is<NonSyntacticVariablesObject>();
 530 }
 531
 532 #ifdef JSGC_HASH_TABLE_CHECKS
 533 void RuntimeCaches::checkEvalCacheAfterMinorGC() {
 534   JSContext* cx = TlsContext.get();
 535   for (auto r = evalCache.all(); !r.empty(); r.popFront()) {
 536     const EvalCacheEntry& entry = r.front();
 537     CheckGCThingAfterMovingGC(entry.str);
 538     EvalCacheLookup lookup(cx);
 539     lookup.str = entry.str;
 540     lookup.callerScript = entry.callerScript;
 541     lookup.pc = entry.pc;
 542     auto ptr = evalCache.lookup(lookup);
 543     MOZ_RELEASE_ASSERT(ptr.found() && &*ptr == &r.front());
 544   }
 545 }
 546 #endif