Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 766 insertions, 0 deletions

diff --git a/js/src/vm/Stack.cpp b/js/src/vm/Stack.cpp
new file mode 100644
index 0000000000..574d8a9379
--- /dev/null
+++ b/js/src/vm/Stack.cpp
@@ -0,0 +1,766 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "vm/Stack-inl.h"
+
+#include "mozilla/Maybe.h"  // mozilla::Maybe
+
+#include <algorithm>  // std::max
+#include <iterator>   // std::size
+#include <stddef.h>   // size_t
+#include <stdint.h>   // uint8_t, uint32_t
+
+#include "gc/Tracer.h"  // js::TraceRoot
+#include "jit/JitcodeMap.h"
+#include "jit/JitRuntime.h"
+#include "js/friend/ErrorMessages.h"  // JSMSG_*
+#include "js/Value.h"                 // JS::Value
+#include "vm/FrameIter.h"             // js::FrameIter
+#include "vm/JSContext.h"
+#include "wasm/WasmProcess.h"
+
+#include "jit/JSJitFrameIter-inl.h"
+#include "vm/Probes-inl.h"
+
+using namespace js;
+
+using mozilla::Maybe;
+
+using JS::Value;
+
+/*****************************************************************************/
+
+void InterpreterFrame::initExecuteFrame(JSContext* cx, HandleScript script,
+                                        AbstractFramePtr evalInFramePrev,
+                                        HandleObject envChain) {
+  flags_ = 0;
+  script_ = script;
+
+  envChain_ = envChain.get();
+  prev_ = nullptr;
+  prevpc_ = nullptr;
+  prevsp_ = nullptr;
+
+  evalInFramePrev_ = evalInFramePrev;
+  MOZ_ASSERT_IF(evalInFramePrev, isDebuggerEvalFrame());
+
+  if (script->isDebuggee()) {
+    setIsDebuggee();
+  }
+
+#ifdef DEBUG
+  Debug_SetValueRangeToCrashOnTouch(&rval_, 1);
+#endif
+}
+
+ArrayObject* InterpreterFrame::createRestParameter(JSContext* cx) {
+  MOZ_ASSERT(script()->hasRest());
+  unsigned nformal = callee().nargs() - 1, nactual = numActualArgs();
+  unsigned nrest = (nactual > nformal) ? nactual - nformal : 0;
+  Value* restvp = argv() + nformal;
+  return NewDenseCopiedArray(cx, nrest, restvp);
+}
+
+static inline void AssertScopeMatchesEnvironment(Scope* scope,
+                                                 JSObject* originalEnv) {
+#ifdef DEBUG
+  JSObject* env = originalEnv;
+  for (ScopeIter si(scope); si; si++) {
+    if (si.kind() == ScopeKind::NonSyntactic) {
+      while (env->is<WithEnvironmentObject>() ||
+             env->is<NonSyntacticVariablesObject>() ||
+             (env->is<LexicalEnvironmentObject>() &&
+              !env->as<LexicalEnvironmentObject>().isSyntactic())) {
+        MOZ_ASSERT(!IsSyntacticEnvironment(env));
+        env = &env->as<EnvironmentObject>().enclosingEnvironment();
+      }
+    } else if (si.hasSyntacticEnvironment()) {
+      switch (si.kind()) {
+        case ScopeKind::Function:
+          MOZ_ASSERT(env->as<CallObject>()
+                         .callee()
+                         .maybeCanonicalFunction()
+                         ->nonLazyScript() ==
+                     si.scope()->as<FunctionScope>().script());
+          env = &env->as<CallObject>().enclosingEnvironment();
+          break;
+
+        case ScopeKind::FunctionBodyVar:
+          MOZ_ASSERT(&env->as<VarEnvironmentObject>().scope() == si.scope());
+          env = &env->as<VarEnvironmentObject>().enclosingEnvironment();
+          break;
+
+        case ScopeKind::Lexical:
+        case ScopeKind::SimpleCatch:
+        case ScopeKind::Catch:
+        case ScopeKind::NamedLambda:
+        case ScopeKind::StrictNamedLambda:
+        case ScopeKind::FunctionLexical:
+        case ScopeKind::ClassBody:
+          MOZ_ASSERT(&env->as<ScopedLexicalEnvironmentObject>().scope() ==
+                     si.scope());
+          env =
+              &env->as<ScopedLexicalEnvironmentObject>().enclosingEnvironment();
+          break;
+
+        case ScopeKind::With:
+          MOZ_ASSERT(&env->as<WithEnvironmentObject>().scope() == si.scope());
+          env = &env->as<WithEnvironmentObject>().enclosingEnvironment();
+          break;
+
+        case ScopeKind::Eval:
+        case ScopeKind::StrictEval:
+          env = &env->as<VarEnvironmentObject>().enclosingEnvironment();
+          break;
+
+        case ScopeKind::Global:
+          env =
+              &env->as<GlobalLexicalEnvironmentObject>().enclosingEnvironment();
+          MOZ_ASSERT(env->is<GlobalObject>());
+          break;
+
+        case ScopeKind::NonSyntactic:
+          MOZ_CRASH("NonSyntactic should not have a syntactic environment");
+          break;
+
+        case ScopeKind::Module:
+          MOZ_ASSERT(&env->as<ModuleEnvironmentObject>().module() ==
+                     si.scope()->as<ModuleScope>().module());
+          env = &env->as<ModuleEnvironmentObject>().enclosingEnvironment();
+          break;
+
+        case ScopeKind::WasmInstance:
+          env =
+              &env->as<WasmInstanceEnvironmentObject>().enclosingEnvironment();
+          break;
+
+        case ScopeKind::WasmFunction:
+          env = &env->as<WasmFunctionCallObject>().enclosingEnvironment();
+          break;
+      }
+    }
+  }
+
+  // In the case of a non-syntactic env chain, the immediate parent of the
+  // outermost non-syntactic env may be the global lexical env, or, if
+  // called from Debugger, a DebugEnvironmentProxy.
+  //
+  // In the case of a syntactic env chain, the outermost env is always a
+  // GlobalObject.
+  MOZ_ASSERT(env->is<GlobalObject>() || IsGlobalLexicalEnvironment(env) ||
+             env->is<DebugEnvironmentProxy>());
+#endif
+}
+
+static inline void AssertScopeMatchesEnvironment(InterpreterFrame* fp,
+                                                 jsbytecode* pc) {
+#ifdef DEBUG
+  // If we OOMed before fully initializing the environment chain, the scope
+  // and environment will definitely mismatch.
+  if (fp->script()->initialEnvironmentShape() && fp->hasInitialEnvironment()) {
+    AssertScopeMatchesEnvironment(fp->script()->innermostScope(pc),
+                                  fp->environmentChain());
+  }
+#endif
+}
+
+bool InterpreterFrame::initFunctionEnvironmentObjects(JSContext* cx) {
+  return js::InitFunctionEnvironmentObjects(cx, this);
+}
+
+bool InterpreterFrame::prologue(JSContext* cx) {
+  RootedScript script(cx, this->script());
+
+  MOZ_ASSERT(cx->interpreterRegs().pc == script->code());
+  MOZ_ASSERT(cx->realm() == script->realm());
+
+  if (!isFunctionFrame()) {
+    return probes::EnterScript(cx, script, nullptr, this);
+  }
+
+  // At this point, we've yet to push any environments. Check that they
+  // match the enclosing scope.
+  AssertScopeMatchesEnvironment(script->enclosingScope(), environmentChain());
+
+  if (callee().needsFunctionEnvironmentObjects() &&
+      !initFunctionEnvironmentObjects(cx)) {
+    return false;
+  }
+
+  MOZ_ASSERT_IF(isConstructing(),
+                thisArgument().isObject() ||
+                    thisArgument().isMagic(JS_UNINITIALIZED_LEXICAL));
+
+  return probes::EnterScript(cx, script, script->function(), this);
+}
+
+void InterpreterFrame::epilogue(JSContext* cx, jsbytecode* pc) {
+  RootedScript script(cx, this->script());
+  MOZ_ASSERT(cx->realm() == script->realm());
+  probes::ExitScript(cx, script, script->function(),
+                     hasPushedGeckoProfilerFrame());
+
+  // Check that the scope matches the environment at the point of leaving
+  // the frame.
+  AssertScopeMatchesEnvironment(this, pc);
+
+  EnvironmentIter ei(cx, this, pc);
+  UnwindAllEnvironmentsInFrame(cx, ei);
+
+  if (isFunctionFrame()) {
+    if (!callee().isGenerator() && !callee().isAsync() && isConstructing() &&
+        thisArgument().isObject() && returnValue().isPrimitive()) {
+      setReturnValue(thisArgument());
+    }
+
+    return;
+  }
+
+  MOZ_ASSERT(isEvalFrame() || isGlobalFrame() || isModuleFrame());
+}
+
+bool InterpreterFrame::checkReturn(JSContext* cx, HandleValue thisv,
+                                   MutableHandleValue result) {
+  MOZ_ASSERT(script()->isDerivedClassConstructor());
+  MOZ_ASSERT(isFunctionFrame());
+  MOZ_ASSERT(callee().isClassConstructor());
+
+  HandleValue retVal = returnValue();
+  if (retVal.isObject()) {
+    result.set(retVal);
+    return true;
+  }
+
+  if (!retVal.isUndefined()) {
+    ReportValueError(cx, JSMSG_BAD_DERIVED_RETURN, JSDVG_IGNORE_STACK, retVal,
+                     nullptr);
+    return false;
+  }
+
+  if (thisv.isMagic(JS_UNINITIALIZED_LEXICAL)) {
+    return ThrowUninitializedThis(cx);
+  }
+
+  result.set(thisv);
+  return true;
+}
+
+bool InterpreterFrame::pushVarEnvironment(JSContext* cx, Handle<Scope*> scope) {
+  return js::PushVarEnvironmentObject(cx, scope, this);
+}
+
+bool InterpreterFrame::pushLexicalEnvironment(JSContext* cx,
+                                              Handle<LexicalScope*> scope) {
+  BlockLexicalEnvironmentObject* env =
+      BlockLexicalEnvironmentObject::createForFrame(cx, scope, this);
+  if (!env) {
+    return false;
+  }
+
+  pushOnEnvironmentChain(*env);
+  return true;
+}
+
+bool InterpreterFrame::freshenLexicalEnvironment(JSContext* cx) {
+  Rooted<BlockLexicalEnvironmentObject*> env(
+      cx, &envChain_->as<BlockLexicalEnvironmentObject>());
+  BlockLexicalEnvironmentObject* fresh =
+      BlockLexicalEnvironmentObject::clone(cx, env);
+  if (!fresh) {
+    return false;
+  }
+
+  replaceInnermostEnvironment(*fresh);
+  return true;
+}
+
+bool InterpreterFrame::recreateLexicalEnvironment(JSContext* cx) {
+  Rooted<BlockLexicalEnvironmentObject*> env(
+      cx, &envChain_->as<BlockLexicalEnvironmentObject>());
+  BlockLexicalEnvironmentObject* fresh =
+      BlockLexicalEnvironmentObject::recreate(cx, env);
+  if (!fresh) {
+    return false;
+  }
+
+  replaceInnermostEnvironment(*fresh);
+  return true;
+}
+
+bool InterpreterFrame::pushClassBodyEnvironment(JSContext* cx,
+                                                Handle<ClassBodyScope*> scope) {
+  ClassBodyLexicalEnvironmentObject* env =
+      ClassBodyLexicalEnvironmentObject::createForFrame(cx, scope, this);
+  if (!env) {
+    return false;
+  }
+
+  pushOnEnvironmentChain(*env);
+  return true;
+}
+
+void InterpreterFrame::trace(JSTracer* trc, Value* sp, jsbytecode* pc) {
+  TraceRoot(trc, &envChain_, "env chain");
+  TraceRoot(trc, &script_, "script");
+
+  if (flags_ & HAS_ARGS_OBJ) {
+    TraceRoot(trc, &argsObj_, "arguments");
+  }
+
+  if (hasReturnValue()) {
+    TraceRoot(trc, &rval_, "rval");
+  }
+
+  MOZ_ASSERT(sp >= slots());
+
+  if (hasArgs()) {
+    // Trace the callee and |this|. When we're doing a moving GC, we
+    // need to fix up the callee pointer before we use it below, under
+    // numFormalArgs() and script().
+    TraceRootRange(trc, 2, argv_ - 2, "fp callee and this");
+
+    // Trace arguments.
+    unsigned argc = std::max(numActualArgs(), numFormalArgs());
+    TraceRootRange(trc, argc + isConstructing(), argv_, "fp argv");
+  }
+
+  JSScript* script = this->script();
+  size_t nfixed = script->nfixed();
+  size_t nlivefixed = script->calculateLiveFixed(pc);
+
+  if (nfixed == nlivefixed) {
+    // All locals are live.
+    traceValues(trc, 0, sp - slots());
+  } else {
+    // Trace operand stack.
+    traceValues(trc, nfixed, sp - slots());
+
+    // Clear dead block-scoped locals.
+    while (nfixed > nlivefixed) {
+      unaliasedLocal(--nfixed).setUndefined();
+    }
+
+    // Trace live locals.
+    traceValues(trc, 0, nlivefixed);
+  }
+
+  if (auto* debugEnvs = script->realm()->debugEnvs()) {
+    debugEnvs->traceLiveFrame(trc, this);
+  }
+}
+
+void InterpreterFrame::traceValues(JSTracer* trc, unsigned start,
+                                   unsigned end) {
+  if (start < end) {
+    TraceRootRange(trc, end - start, slots() + start, "vm_stack");
+  }
+}
+
+static void TraceInterpreterActivation(JSTracer* trc,
+                                       InterpreterActivation* act) {
+  for (InterpreterFrameIterator frames(act); !frames.done(); ++frames) {
+    InterpreterFrame* fp = frames.frame();
+    fp->trace(trc, frames.sp(), frames.pc());
+  }
+}
+
+void js::TraceInterpreterActivations(JSContext* cx, JSTracer* trc) {
+  for (ActivationIterator iter(cx); !iter.done(); ++iter) {
+    Activation* act = iter.activation();
+    if (act->isInterpreter()) {
+      TraceInterpreterActivation(trc, act->asInterpreter());
+    }
+  }
+}
+
+/*****************************************************************************/
+
+// Unlike the other methods of this class, this method is defined here so that
+// we don't have to #include jsautooplen.h in vm/Stack.h.
+void InterpreterRegs::setToEndOfScript() { sp = fp()->base(); }
+
+/*****************************************************************************/
+
+InterpreterFrame* InterpreterStack::pushInvokeFrame(
+    JSContext* cx, const CallArgs& args, MaybeConstruct constructing) {
+  LifoAlloc::Mark mark = allocator_.mark();
+
+  RootedFunction fun(cx, &args.callee().as<JSFunction>());
+  RootedScript script(cx, fun->nonLazyScript());
+
+  Value* argv;
+  InterpreterFrame* fp = getCallFrame(cx, args, script, constructing, &argv);
+  if (!fp) {
+    return nullptr;
+  }
+
+  fp->mark_ = mark;
+  fp->initCallFrame(nullptr, nullptr, nullptr, *fun, script, argv,
+                    args.length(), constructing);
+  return fp;
+}
+
+InterpreterFrame* InterpreterStack::pushExecuteFrame(
+    JSContext* cx, HandleScript script, HandleObject envChain,
+    AbstractFramePtr evalInFrame) {
+  LifoAlloc::Mark mark = allocator_.mark();
+
+  unsigned nvars = script->nslots();
+  uint8_t* buffer =
+      allocateFrame(cx, sizeof(InterpreterFrame) + nvars * sizeof(Value));
+  if (!buffer) {
+    return nullptr;
+  }
+
+  InterpreterFrame* fp = reinterpret_cast<InterpreterFrame*>(buffer);
+  fp->mark_ = mark;
+  fp->initExecuteFrame(cx, script, evalInFrame, envChain);
+  fp->initLocals();
+
+  return fp;
+}
+
+/*****************************************************************************/
+
+InterpreterFrameIterator& InterpreterFrameIterator::operator++() {
+  MOZ_ASSERT(!done());
+  if (fp_ != activation_->entryFrame_) {
+    pc_ = fp_->prevpc();
+    sp_ = fp_->prevsp();
+    fp_ = fp_->prev();
+  } else {
+    pc_ = nullptr;
+    sp_ = nullptr;
+    fp_ = nullptr;
+  }
+  return *this;
+}
+
+JS::ProfilingFrameIterator::ProfilingFrameIterator(
+    JSContext* cx, const RegisterState& state,
+    const Maybe<uint64_t>& samplePositionInProfilerBuffer)
+    : cx_(cx),
+      samplePositionInProfilerBuffer_(samplePositionInProfilerBuffer),
+      activation_(nullptr) {
+  if (!cx->runtime()->geckoProfiler().enabled()) {
+    MOZ_CRASH(
+        "ProfilingFrameIterator called when geckoProfiler not enabled for "
+        "runtime.");
+  }
+
+  if (!cx->profilingActivation()) {
+    return;
+  }
+
+  // If profiler sampling is not enabled, skip.
+  if (!cx->isProfilerSamplingEnabled()) {
+    return;
+  }
+
+  activation_ = cx->profilingActivation();
+
+  MOZ_ASSERT(activation_->isProfiling());
+
+  static_assert(sizeof(wasm::ProfilingFrameIterator) <= StorageSpace &&
+                    sizeof(jit::JSJitProfilingFrameIterator) <= StorageSpace,
+                "ProfilingFrameIterator::storage_ is too small");
+  static_assert(alignof(void*) >= alignof(wasm::ProfilingFrameIterator) &&
+                    alignof(void*) >= alignof(jit::JSJitProfilingFrameIterator),
+                "ProfilingFrameIterator::storage_ is too weakly aligned");
+
+  iteratorConstruct(state);
+  settle();
+}
+
+JS::ProfilingFrameIterator::~ProfilingFrameIterator() {
+  if (!done()) {
+    MOZ_ASSERT(activation_->isProfiling());
+    iteratorDestroy();
+  }
+}
+
+void JS::ProfilingFrameIterator::operator++() {
+  MOZ_ASSERT(!done());
+  MOZ_ASSERT(activation_->isJit());
+  if (isWasm()) {
+    ++wasmIter();
+  } else {
+    ++jsJitIter();
+  }
+  settle();
+}
+
+void JS::ProfilingFrameIterator::settleFrames() {
+  // Handle transition frames (see comment in JitFrameIter::operator++).
+  if (isJSJit() && !jsJitIter().done() &&
+      jsJitIter().frameType() == jit::FrameType::WasmToJSJit) {
+    wasm::Frame* fp = (wasm::Frame*)jsJitIter().fp();
+    iteratorDestroy();
+    new (storage()) wasm::ProfilingFrameIterator(fp);
+    kind_ = Kind::Wasm;
+    MOZ_ASSERT(!wasmIter().done());
+    maybeSetEndStackAddress(wasmIter().endStackAddress());
+    return;
+  }
+
+  if (isWasm() && wasmIter().done() && wasmIter().unwoundJitCallerFP()) {
+    uint8_t* fp = wasmIter().unwoundJitCallerFP();
+    iteratorDestroy();
+    // Using this ctor will skip the first jit->wasm frame, which is
+    // needed because the profiling iterator doesn't know how to unwind
+    // when the callee has no script.
+    new (storage())
+        jit::JSJitProfilingFrameIterator((jit::CommonFrameLayout*)fp);
+    kind_ = Kind::JSJit;
+    MOZ_ASSERT(!jsJitIter().done());
+    maybeSetEndStackAddress(jsJitIter().endStackAddress());
+    return;
+  }
+}
+
+void JS::ProfilingFrameIterator::settle() {
+  settleFrames();
+  while (iteratorDone()) {
+    iteratorDestroy();
+    activation_ = activation_->prevProfiling();
+    endStackAddress_ = nullptr;
+    if (!activation_) {
+      return;
+    }
+    iteratorConstruct();
+    settleFrames();
+  }
+}
+
+void JS::ProfilingFrameIterator::iteratorConstruct(const RegisterState& state) {
+  MOZ_ASSERT(!done());
+  MOZ_ASSERT(activation_->isJit());
+
+  jit::JitActivation* activation = activation_->asJit();
+
+  // We want to know if we should start with a wasm profiling frame iterator
+  // or not. To determine this, there are three possibilities:
+  // - we've exited to C++ from wasm, in which case the activation
+  //   exitFP low bit is tagged and we can test hasWasmExitFP().
+  // - we're in wasm code, so we can do a lookup on PC.
+  // - in all the other cases, we're not in wasm or we haven't exited from
+  //   wasm.
+  if (activation->hasWasmExitFP() || wasm::InCompiledCode(state.pc)) {
+    new (storage()) wasm::ProfilingFrameIterator(*activation, state);
+    kind_ = Kind::Wasm;
+    maybeSetEndStackAddress(wasmIter().endStackAddress());
+    return;
+  }
+
+  new (storage()) jit::JSJitProfilingFrameIterator(cx_, state.pc, state.sp);
+  kind_ = Kind::JSJit;
+  maybeSetEndStackAddress(jsJitIter().endStackAddress());
+}
+
+void JS::ProfilingFrameIterator::iteratorConstruct() {
+  MOZ_ASSERT(!done());
+  MOZ_ASSERT(activation_->isJit());
+
+  jit::JitActivation* activation = activation_->asJit();
+
+  // The same reasoning as in the above iteratorConstruct variant applies
+  // here, except that it's even simpler: since this activation is higher up
+  // on the stack, it can only have exited to C++, through wasm or ion.
+  if (activation->hasWasmExitFP()) {
+    new (storage()) wasm::ProfilingFrameIterator(*activation);
+    kind_ = Kind::Wasm;
+    maybeSetEndStackAddress(wasmIter().endStackAddress());
+    return;
+  }
+
+  auto* fp = (jit::ExitFrameLayout*)activation->jsExitFP();
+  new (storage()) jit::JSJitProfilingFrameIterator(fp);
+  kind_ = Kind::JSJit;
+  maybeSetEndStackAddress(jsJitIter().endStackAddress());
+}
+
+void JS::ProfilingFrameIterator::iteratorDestroy() {
+  MOZ_ASSERT(!done());
+  MOZ_ASSERT(activation_->isJit());
+
+  if (isWasm()) {
+    wasmIter().~ProfilingFrameIterator();
+    return;
+  }
+
+  jsJitIter().~JSJitProfilingFrameIterator();
+}
+
+bool JS::ProfilingFrameIterator::iteratorDone() {
+  MOZ_ASSERT(!done());
+  MOZ_ASSERT(activation_->isJit());
+
+  if (isWasm()) {
+    return wasmIter().done();
+  }
+
+  return jsJitIter().done();
+}
+
+void* JS::ProfilingFrameIterator::stackAddress() const {
+  MOZ_ASSERT(!done());
+  MOZ_ASSERT(activation_->isJit());
+
+  if (isWasm()) {
+    return wasmIter().stackAddress();
+  }
+
+  return jsJitIter().stackAddress();
+}
+
+Maybe<JS::ProfilingFrameIterator::Frame>
+JS::ProfilingFrameIterator::getPhysicalFrameAndEntry(
+    const jit::JitcodeGlobalEntry** entry) const {
+  *entry = nullptr;
+
+  void* stackAddr = stackAddress();
+
+  MOZ_DIAGNOSTIC_ASSERT(endStackAddress_);
+  MOZ_DIAGNOSTIC_ASSERT(stackAddr >= endStackAddress_);
+
+  if (isWasm()) {
+    Frame frame;
+    frame.kind = Frame_Wasm;
+    frame.stackAddress = stackAddr;
+    frame.returnAddress_ = nullptr;
+    frame.activation = activation_;
+    frame.label = nullptr;
+    frame.endStackAddress = endStackAddress_;
+    frame.interpreterScript = nullptr;
+    // TODO: get the realm ID of wasm frames. Bug 1596235.
+    frame.realmID = 0;
+    return mozilla::Some(frame);
+  }
+
+  MOZ_ASSERT(isJSJit());
+
+  // Look up an entry for the return address.
+  void* returnAddr = jsJitIter().resumePCinCurrentFrame();
+  jit::JitcodeGlobalTable* table =
+      cx_->runtime()->jitRuntime()->getJitcodeGlobalTable();
+
+  // NB:
+  // The following lookups should be infallible, but the ad-hoc stackwalking
+  // code rots easily and corner cases where frames can't be looked up
+  // occur too often (e.g. once every day).
+  //
+  // The calls to `lookup*` below have been changed from infallible ones to
+  // fallible ones.  The proper solution to this problem is to fix all
+  // the jitcode to use frame-pointers and reliably walk the stack with those.
+  if (samplePositionInProfilerBuffer_) {
+    *entry = table->lookupForSampler(returnAddr, cx_->runtime(),
+                                     *samplePositionInProfilerBuffer_);
+  } else {
+    *entry = table->lookup(returnAddr);
+  }
+
+  // Failed to look up a jitcode entry for the given address, ignore.
+  if (!*entry) {
+    return mozilla::Nothing();
+  }
+
+  // Dummy frames produce no stack frames.
+  if ((*entry)->isDummy()) {
+    return mozilla::Nothing();
+  }
+
+  Frame frame;
+  if ((*entry)->isBaselineInterpreter()) {
+    frame.kind = Frame_BaselineInterpreter;
+  } else if ((*entry)->isBaseline()) {
+    frame.kind = Frame_Baseline;
+  } else {
+    MOZ_ASSERT((*entry)->isIon() || (*entry)->isIonIC());
+    frame.kind = Frame_Ion;
+  }
+  frame.stackAddress = stackAddr;
+  if ((*entry)->isBaselineInterpreter()) {
+    frame.label = jsJitIter().baselineInterpreterLabel();
+    jsJitIter().baselineInterpreterScriptPC(
+        &frame.interpreterScript, &frame.interpreterPC_, &frame.realmID);
+    MOZ_ASSERT(frame.interpreterScript);
+    MOZ_ASSERT(frame.interpreterPC_);
+  } else {
+    frame.interpreterScript = nullptr;
+    frame.returnAddress_ = returnAddr;
+    frame.label = nullptr;
+    frame.realmID = 0;
+  }
+  frame.activation = activation_;
+  frame.endStackAddress = endStackAddress_;
+  return mozilla::Some(frame);
+}
+
+uint32_t JS::ProfilingFrameIterator::extractStack(Frame* frames,
+                                                  uint32_t offset,
+                                                  uint32_t end) const {
+  if (offset >= end) {
+    return 0;
+  }
+
+  const jit::JitcodeGlobalEntry* entry;
+  Maybe<Frame> physicalFrame = getPhysicalFrameAndEntry(&entry);
+
+  // Dummy frames produce no stack frames.
+  if (physicalFrame.isNothing()) {
+    return 0;
+  }
+
+  if (isWasm()) {
+    frames[offset] = physicalFrame.value();
+    frames[offset].label = wasmIter().label();
+    return 1;
+  }
+
+  if (physicalFrame->kind == Frame_BaselineInterpreter) {
+    frames[offset] = physicalFrame.value();
+    return 1;
+  }
+
+  // Extract the stack for the entry.  Assume maximum inlining depth is <64
+  const char* labels[64];
+  uint32_t depth = entry->callStackAtAddr(cx_->runtime(),
+                                          jsJitIter().resumePCinCurrentFrame(),
+                                          labels, std::size(labels));
+  MOZ_ASSERT(depth < std::size(labels));
+  for (uint32_t i = 0; i < depth; i++) {
+    if (offset + i >= end) {
+      return i;
+    }
+    frames[offset + i] = physicalFrame.value();
+    frames[offset + i].label = labels[i];
+  }
+
+  return depth;
+}
+
+Maybe<JS::ProfilingFrameIterator::Frame>
+JS::ProfilingFrameIterator::getPhysicalFrameWithoutLabel() const {
+  const jit::JitcodeGlobalEntry* unused;
+  return getPhysicalFrameAndEntry(&unused);
+}
+
+bool JS::ProfilingFrameIterator::isWasm() const {
+  MOZ_ASSERT(!done());
+  return kind_ == Kind::Wasm;
+}
+
+bool JS::ProfilingFrameIterator::isJSJit() const {
+  return kind_ == Kind::JSJit;
+}
+
+mozilla::Maybe<JS::ProfilingFrameIterator::RegisterState>
+JS::ProfilingFrameIterator::getCppEntryRegisters() const {
+  if (!isJSJit()) {
+    return mozilla::Nothing{};
+  }
+  return jit::JitRuntime::getCppEntryRegisters(jsJitIter().framePtr());
+}