1 files changed, 352 insertions, 0 deletions
diff --git a/js/src/jit/Bailouts.cpp b/js/src/jit/Bailouts.cpp
new file mode 100644
index 0000000000..3730d8997a
--- /dev/null
+++ b/js/src/jit/Bailouts.cpp
@@ -0,0 +1,352 @@
+/* -*- 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 "jit/Bailouts.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/ScopeExit.h"
+
+#include "gc/GC.h"
+#include "jit/Assembler.h"  // jit::FramePointer
+#include "jit/BaselineJIT.h"
+#include "jit/JitFrames.h"
+#include "jit/JitRuntime.h"
+#include "jit/JitSpewer.h"
+#include "jit/JSJitFrameIter.h"
+#include "jit/SafepointIndex.h"
+#include "jit/ScriptFromCalleeToken.h"
+#include "vm/Interpreter.h"
+#include "vm/JSContext.h"
+#include "vm/Stack.h"
+
+#include "vm/JSScript-inl.h"
+#include "vm/Probes-inl.h"
+#include "vm/Stack-inl.h"
+
+using namespace js;
+using namespace js::jit;
+
+using mozilla::IsInRange;
+
+#if defined(_WIN32)
+#  pragma pack(push, 1)
+#endif
+class js::jit::BailoutStack {
+  RegisterDump::FPUArray fpregs_;
+  RegisterDump::GPRArray regs_;
+  uintptr_t frameSize_;
+  uintptr_t snapshotOffset_;
+
+ public:
+  MachineState machineState() {
+    return MachineState::FromBailout(regs_, fpregs_);
+  }
+  uint32_t snapshotOffset() const { return snapshotOffset_; }
+  uint32_t frameSize() const { return frameSize_; }
+  uint8_t* parentStackPointer() {
+    return (uint8_t*)this + sizeof(BailoutStack);
+  }
+};
+#if defined(_WIN32)
+#  pragma pack(pop)
+#endif
+
+// Make sure the compiler doesn't add extra padding on 32-bit platforms.
+static_assert((sizeof(BailoutStack) % 8) == 0,
+              "BailoutStack should be 8-byte aligned.");
+
+BailoutFrameInfo::BailoutFrameInfo(const JitActivationIterator& activations,
+                                   BailoutStack* bailout)
+    : machine_(bailout->machineState()), activation_(nullptr) {
+  uint8_t* sp = bailout->parentStackPointer();
+  framePointer_ = sp + bailout->frameSize();
+  MOZ_RELEASE_ASSERT(uintptr_t(framePointer_) == machine_.read(FramePointer));
+
+  JSScript* script =
+      ScriptFromCalleeToken(((JitFrameLayout*)framePointer_)->calleeToken());
+  topIonScript_ = script->ionScript();
+
+  attachOnJitActivation(activations);
+  snapshotOffset_ = bailout->snapshotOffset();
+}
+
+BailoutFrameInfo::BailoutFrameInfo(const JitActivationIterator& activations,
+                                   InvalidationBailoutStack* bailout)
+    : machine_(bailout->machine()), activation_(nullptr) {
+  framePointer_ = (uint8_t*)bailout->fp();
+  MOZ_RELEASE_ASSERT(uintptr_t(framePointer_) == machine_.read(FramePointer));
+
+  topIonScript_ = bailout->ionScript();
+  attachOnJitActivation(activations);
+
+  uint8_t* returnAddressToFp_ = bailout->osiPointReturnAddress();
+  const OsiIndex* osiIndex = topIonScript_->getOsiIndex(returnAddressToFp_);
+  snapshotOffset_ = osiIndex->snapshotOffset();
+}
+
+BailoutFrameInfo::BailoutFrameInfo(const JitActivationIterator& activations,
+                                   const JSJitFrameIter& frame)
+    : machine_(frame.machineState()) {
+  framePointer_ = (uint8_t*)frame.fp();
+  topIonScript_ = frame.ionScript();
+  attachOnJitActivation(activations);
+
+  const OsiIndex* osiIndex = frame.osiIndex();
+  snapshotOffset_ = osiIndex->snapshotOffset();
+}
+
+// This address is a magic number made to cause crashes while indicating that we
+// are making an attempt to mark the stack during a bailout.
+static constexpr uint32_t FAKE_EXITFP_FOR_BAILOUT_ADDR = 0xba2;
+static uint8_t* const FAKE_EXITFP_FOR_BAILOUT =
+    reinterpret_cast<uint8_t*>(FAKE_EXITFP_FOR_BAILOUT_ADDR);
+
+static_assert(!(FAKE_EXITFP_FOR_BAILOUT_ADDR & wasm::ExitFPTag),
+              "FAKE_EXITFP_FOR_BAILOUT could be mistaken as a low-bit tagged "
+              "wasm exit fp");
+
+bool jit::Bailout(BailoutStack* sp, BaselineBailoutInfo** bailoutInfo) {
+  JSContext* cx = TlsContext.get();
+  MOZ_ASSERT(bailoutInfo);
+
+  // We don't have an exit frame.
+  MOZ_ASSERT(IsInRange(FAKE_EXITFP_FOR_BAILOUT, 0, 0x1000) &&
+                 IsInRange(FAKE_EXITFP_FOR_BAILOUT + sizeof(CommonFrameLayout),
+                           0, 0x1000),
+             "Fake exitfp pointer should be within the first page.");
+
+#ifdef DEBUG
+  // Reset the counter when we bailed after MDebugEnterGCUnsafeRegion, but
+  // before the matching MDebugLeaveGCUnsafeRegion.
+  //
+  // NOTE: EnterJit ensures the counter is zero when we enter JIT code.
+  cx->resetInUnsafeRegion();
+#endif
+
+  cx->activation()->asJit()->setJSExitFP(FAKE_EXITFP_FOR_BAILOUT);
+
+  JitActivationIterator jitActivations(cx);
+  BailoutFrameInfo bailoutData(jitActivations, sp);
+  JSJitFrameIter frame(jitActivations->asJit());
+  MOZ_ASSERT(!frame.ionScript()->invalidated());
+  JitFrameLayout* currentFramePtr = frame.jsFrame();
+
+  JitSpew(JitSpew_IonBailouts, "Took bailout! Snapshot offset: %u",
+          frame.snapshotOffset());
+
+  MOZ_ASSERT(IsBaselineJitEnabled(cx));
+
+  *bailoutInfo = nullptr;
+  bool success =
+      BailoutIonToBaseline(cx, bailoutData.activation(), frame, bailoutInfo,
+                           /*exceptionInfo=*/nullptr, BailoutReason::Normal);
+  MOZ_ASSERT_IF(success, *bailoutInfo != nullptr);
+
+  if (!success) {
+    MOZ_ASSERT(cx->isExceptionPending());
+    JSScript* script = frame.script();
+    probes::ExitScript(cx, script, script->function(),
+                       /* popProfilerFrame = */ false);
+  }
+
+  // This condition was wrong when we entered this bailout function, but it
+  // might be true now. A GC might have reclaimed all the Jit code and
+  // invalidated all frames which are currently on the stack. As we are
+  // already in a bailout, we could not switch to an invalidation
+  // bailout. When the code of an IonScript which is on the stack is
+  // invalidated (see InvalidateActivation), we remove references to it and
+  // increment the reference counter for each activation that appear on the
+  // stack. As the bailed frame is one of them, we have to decrement it now.
+  if (frame.ionScript()->invalidated()) {
+    frame.ionScript()->decrementInvalidationCount(cx->gcContext());
+  }
+
+  // NB: Commentary on how |lastProfilingFrame| is set from bailouts.
+  //
+  // Once we return to jitcode, any following frames might get clobbered,
+  // but the current frame will not (as it will be clobbered "in-place"
+  // with a baseline frame that will share the same frame prefix).
+  // However, there may be multiple baseline frames unpacked from this
+  // single Ion frame, which means we will need to once again reset
+  // |lastProfilingFrame| to point to the correct unpacked last frame
+  // in |FinishBailoutToBaseline|.
+  //
+  // In the case of error, the jitcode will jump immediately to an
+  // exception handler, which will unwind the frames and properly set
+  // the |lastProfilingFrame| to point to the frame being resumed into
+  // (see |AutoResetLastProfilerFrameOnReturnFromException|).
+  //
+  // In both cases, we want to temporarily set the |lastProfilingFrame|
+  // to the current frame being bailed out, and then fix it up later.
+  if (cx->runtime()->jitRuntime()->isProfilerInstrumentationEnabled(
+          cx->runtime())) {
+    cx->jitActivation->setLastProfilingFrame(currentFramePtr);
+  }
+
+  return success;
+}
+
+bool jit::InvalidationBailout(InvalidationBailoutStack* sp,
+                              BaselineBailoutInfo** bailoutInfo) {
+  sp->checkInvariants();
+
+  JSContext* cx = TlsContext.get();
+
+#ifdef DEBUG
+  // Reset the counter when we bailed after MDebugEnterGCUnsafeRegion, but
+  // before the matching MDebugLeaveGCUnsafeRegion.
+  //
+  // NOTE: EnterJit ensures the counter is zero when we enter JIT code.
+  cx->resetInUnsafeRegion();
+#endif
+
+  // We don't have an exit frame.
+  cx->activation()->asJit()->setJSExitFP(FAKE_EXITFP_FOR_BAILOUT);
+
+  JitActivationIterator jitActivations(cx);
+  BailoutFrameInfo bailoutData(jitActivations, sp);
+  JSJitFrameIter frame(jitActivations->asJit());
+  JitFrameLayout* currentFramePtr = frame.jsFrame();
+
+  JitSpew(JitSpew_IonBailouts, "Took invalidation bailout! Snapshot offset: %u",
+          frame.snapshotOffset());
+
+  MOZ_ASSERT(IsBaselineJitEnabled(cx));
+
+  *bailoutInfo = nullptr;
+  bool success = BailoutIonToBaseline(cx, bailoutData.activation(), frame,
+                                      bailoutInfo, /*exceptionInfo=*/nullptr,
+                                      BailoutReason::Invalidate);
+  MOZ_ASSERT_IF(success, *bailoutInfo != nullptr);
+
+  if (!success) {
+    MOZ_ASSERT(cx->isExceptionPending());
+
+    // If the bailout failed, then bailout trampoline will pop the
+    // current frame and jump straight to exception handling code when
+    // this function returns.  Any Gecko Profiler entry pushed for this
+    // frame will be silently forgotten.
+    //
+    // We call ExitScript here to ensure that if the ionScript had Gecko
+    // Profiler instrumentation, then the entry for it is popped.
+    //
+    // However, if the bailout was during argument check, then a
+    // pseudostack frame would not have been pushed in the first
+    // place, so don't pop anything in that case.
+    JSScript* script = frame.script();
+    probes::ExitScript(cx, script, script->function(),
+                       /* popProfilerFrame = */ false);
+
+#ifdef JS_JITSPEW
+    JitFrameLayout* layout = frame.jsFrame();
+    JitSpew(JitSpew_IonInvalidate, "Bailout failed (Fatal Error)");
+    JitSpew(JitSpew_IonInvalidate, "   calleeToken %p",
+            (void*)layout->calleeToken());
+    JitSpew(JitSpew_IonInvalidate, "   callerFramePtr %p",
+            layout->callerFramePtr());
+    JitSpew(JitSpew_IonInvalidate, "   ra %p", (void*)layout->returnAddress());
+#endif
+  }
+
+  frame.ionScript()->decrementInvalidationCount(cx->gcContext());
+
+  // Make the frame being bailed out the top profiled frame.
+  if (cx->runtime()->jitRuntime()->isProfilerInstrumentationEnabled(
+          cx->runtime())) {
+    cx->jitActivation->setLastProfilingFrame(currentFramePtr);
+  }
+
+  return success;
+}
+
+bool jit::ExceptionHandlerBailout(JSContext* cx,
+                                  const InlineFrameIterator& frame,
+                                  ResumeFromException* rfe,
+                                  const ExceptionBailoutInfo& excInfo) {
+  // If we are resuming in a finally block, the exception has already
+  // been captured.
+  // We can also be propagating debug mode exceptions without there being an
+  // actual exception pending. For instance, when we return false from an
+  // operation callback like a timeout handler.
+  MOZ_ASSERT_IF(
+      !cx->isExceptionPending(),
+      excInfo.isFinally() || excInfo.propagatingIonExceptionForDebugMode());
+
+  JS::AutoSaveExceptionState savedExc(cx);
+
+  JitActivation* act = cx->activation()->asJit();
+  uint8_t* prevExitFP = act->jsExitFP();
+  auto restoreExitFP =
+      mozilla::MakeScopeExit([&]() { act->setJSExitFP(prevExitFP); });
+  act->setJSExitFP(FAKE_EXITFP_FOR_BAILOUT);
+
+  gc::AutoSuppressGC suppress(cx);
+
+  JitActivationIterator jitActivations(cx);
+  BailoutFrameInfo bailoutData(jitActivations, frame.frame());
+  JSJitFrameIter frameView(jitActivations->asJit());
+  JitFrameLayout* currentFramePtr = frameView.jsFrame();
+
+  BaselineBailoutInfo* bailoutInfo = nullptr;
+  bool success = BailoutIonToBaseline(cx, bailoutData.activation(), frameView,
+                                      &bailoutInfo, &excInfo,
+                                      BailoutReason::ExceptionHandler);
+  if (success) {
+    MOZ_ASSERT(bailoutInfo);
+
+    // Overwrite the kind so HandleException after the bailout returns
+    // false, jumping directly to the exception tail.
+    if (excInfo.propagatingIonExceptionForDebugMode()) {
+      bailoutInfo->bailoutKind =
+          mozilla::Some(BailoutKind::IonExceptionDebugMode);
+    } else if (excInfo.isFinally()) {
+      bailoutInfo->bailoutKind = mozilla::Some(BailoutKind::Finally);
+    }
+
+    rfe->kind = ExceptionResumeKind::Bailout;
+    rfe->stackPointer = bailoutInfo->incomingStack;
+    rfe->bailoutInfo = bailoutInfo;
+  } else {
+    // Drop the exception that triggered the bailout and instead propagate the
+    // failure caused by processing the bailout (eg. OOM).
+    savedExc.drop();
+    MOZ_ASSERT(!bailoutInfo);
+    MOZ_ASSERT(cx->isExceptionPending());
+  }
+
+  // Make the frame being bailed out the top profiled frame.
+  if (cx->runtime()->jitRuntime()->isProfilerInstrumentationEnabled(
+          cx->runtime())) {
+    cx->jitActivation->setLastProfilingFrame(currentFramePtr);
+  }
+
+  return success;
+}
+
+// Initialize the NamedLambdaObject and CallObject of the current frame if
+// needed.
+bool jit::EnsureHasEnvironmentObjects(JSContext* cx, AbstractFramePtr fp) {
+  // Ion does not compile eval scripts.
+  MOZ_ASSERT(!fp.isEvalFrame());
+
+  if (fp.isFunctionFrame() && !fp.hasInitialEnvironment() &&
+      fp.callee()->needsFunctionEnvironmentObjects()) {
+    if (!fp.initFunctionEnvironmentObjects(cx)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void BailoutFrameInfo::attachOnJitActivation(
+    const JitActivationIterator& jitActivations) {
+  MOZ_ASSERT(jitActivations->asJit()->jsExitFP() == FAKE_EXITFP_FOR_BAILOUT);
+  activation_ = jitActivations->asJit();
+  activation_->setBailoutData(this);
+}
+
+BailoutFrameInfo::~BailoutFrameInfo() { activation_->cleanBailoutData(); }