Bug 1435360 - Baldr: remove wasm async interrupt support (r=jandem)

--HG--
extra : rebase_source : af951434c93e1c946cad43aaae023b491fb58ef1

js/src/jit/Ion.cpp

@@ -47,6 +47,7 @@
 #include "jit/ValueNumbering.h"
 #include "jit/WasmBCE.h"
 #include "js/Printf.h"
+#include "util/Windows.h"
 #include "vm/Debugger.h"
 #include "vm/HelperThreads.h"
 #include "vm/JSCompartment.h"
@@ -64,6 +65,10 @@
 #include "vm/JSScript-inl.h"
 #include "vm/Stack-inl.h"
 
+#if defined(ANDROID)
+# include <sys/system_properties.h>
+#endif
+
 using namespace js;
 using namespace js::jit;
 
@@ -392,7 +397,7 @@ JitZoneGroup::patchIonBackedges(JSContext* cx, BackedgeTarget target)
         MOZ_ASSERT(cx->runtime()->jitRuntime()->preventBackedgePatching());
         MOZ_ASSERT(CurrentThreadCanAccessRuntime(cx->runtime()));
     } else {
-        // We must be called from InterruptRunningJitCode, or a signal handler
+        // We must be called from jit::InterruptRunningCode, or a signal handler
         // triggered there. rt->handlingJitInterrupt() ensures we can't reenter
         // this code.
         MOZ_ASSERT(!cx->runtime()->jitRuntime()->preventBackedgePatching());
@@ -3352,3 +3357,169 @@ jit::JitSupportsAtomics()
 // If you change these, please also change the comment in TempAllocator.
 /* static */ const size_t TempAllocator::BallastSize            = 16 * 1024;
 /* static */ const size_t TempAllocator::PreferredLifoChunkSize = 32 * 1024;
+
+static void
+RedirectIonBackedgesToInterruptCheck(JSContext* cx)
+{
+    // Jitcode may only be modified on the runtime's active thread.
+    if (cx != cx->runtime()->activeContext())
+        return;
+
+    // The faulting thread is suspended so we can access cx fields that can
+    // normally only be accessed by the cx's active thread.
+    AutoNoteSingleThreadedRegion anstr;
+
+    Zone* zone = cx->zoneRaw();
+    if (zone && !zone->isAtomsZone()) {
+        jit::JitRuntime* jitRuntime = cx->runtime()->jitRuntime();
+        if (!jitRuntime)
+            return;
+
+        // If the backedge list is being mutated, the pc must be in C++ code and
+        // thus not in a JIT iloop. We assume that the interrupt flag will be
+        // checked at least once before entering JIT code (if not, no big deal;
+        // the browser will just request another interrupt in a second).
+        if (!jitRuntime->preventBackedgePatching()) {
+            jit::JitZoneGroup* jzg = zone->group()->jitZoneGroup;
+            jzg->patchIonBackedges(cx, jit::JitZoneGroup::BackedgeInterruptCheck);
+        }
+    }
+}
+
+#if !defined(XP_WIN)
+// For the interrupt signal, pick a signal number that:
+//  - is not otherwise used by mozilla or standard libraries
+//  - defaults to nostop and noprint on gdb/lldb so that noone is bothered
+// SIGVTALRM a relative of SIGALRM, so intended for user code, but, unlike
+// SIGALRM, not used anywhere else in Mozilla.
+static const int sJitAsyncInterruptSignal = SIGVTALRM;
+
+static void
+JitAsyncInterruptHandler(int signum, siginfo_t*, void*)
+{
+    MOZ_RELEASE_ASSERT(signum == sJitAsyncInterruptSignal);
+
+    JSContext* cx = TlsContext.get();
+    if (!cx)
+        return;
+
+#if defined(JS_SIMULATOR_ARM) || defined(JS_SIMULATOR_MIPS32) || defined(JS_SIMULATOR_MIPS64)
+    SimulatorProcess::ICacheCheckingDisableCount++;
+#endif
+
+    RedirectIonBackedgesToInterruptCheck(cx);
+
+#if defined(JS_SIMULATOR_ARM) || defined(JS_SIMULATOR_MIPS32) || defined(JS_SIMULATOR_MIPS64)
+    SimulatorProcess::cacheInvalidatedBySignalHandler_ = true;
+    SimulatorProcess::ICacheCheckingDisableCount--;
+#endif
+
+    cx->finishHandlingJitInterrupt();
+}
+#endif
+
+static bool sTriedInstallAsyncInterrupt = false;
+static bool sHaveAsyncInterrupt = false;
+
+void
+jit::EnsureAsyncInterrupt(JSContext* cx)
+{
+    // We assume that there are no races creating the first JSRuntime of the process.
+    if (sTriedInstallAsyncInterrupt)
+        return;
+    sTriedInstallAsyncInterrupt = true;
+
+#if defined(ANDROID) && !defined(__aarch64__)
+    // Before Android 4.4 (SDK version 19), there is a bug
+    //   https://android-review.googlesource.com/#/c/52333
+    // in Bionic's pthread_join which causes pthread_join to return early when
+    // pthread_kill is used (on any thread). Nobody expects the pthread_cond_wait
+    // EINTRquisition.
+    char version_string[PROP_VALUE_MAX];
+    mozilla::PodArrayZero(version_string);
+    if (__system_property_get("ro.build.version.sdk", version_string) > 0) {
+        if (atol(version_string) < 19)
+            return;
+    }
+#endif
+
+#if defined(XP_WIN)
+    // Windows uses SuspendThread to stop the active thread from another thread.
+#else
+    struct sigaction interruptHandler;
+    interruptHandler.sa_flags = SA_SIGINFO;
+    interruptHandler.sa_sigaction = &JitAsyncInterruptHandler;
+    sigemptyset(&interruptHandler.sa_mask);
+    struct sigaction prev;
+    if (sigaction(sJitAsyncInterruptSignal, &interruptHandler, &prev))
+        MOZ_CRASH("unable to install interrupt handler");
+
+    // There shouldn't be any other handlers installed for
+    // sJitAsyncInterruptSignal. If there are, we could always forward, but we
+    // need to understand what we're doing to avoid problematic interference.
+    if ((prev.sa_flags & SA_SIGINFO && prev.sa_sigaction) ||
+        (prev.sa_handler != SIG_DFL && prev.sa_handler != SIG_IGN))
+    {
+        MOZ_CRASH("contention for interrupt signal");
+    }
+#endif // defined(XP_WIN)
+
+    sHaveAsyncInterrupt = true;
+}
+
+bool
+jit::HaveAsyncInterrupt()
+{
+    MOZ_ASSERT(sTriedInstallAsyncInterrupt);
+    return sHaveAsyncInterrupt;
+}
+
+// JSRuntime::requestInterrupt sets interrupt_ (which is checked frequently by
+// C++ code at every Baseline JIT loop backedge) and jitStackLimit_ (which is
+// checked at every Baseline and Ion JIT function prologue). The remaining
+// sources of potential iloops (Ion loop backedges) are handled by this
+// function: Ion loop backedges are patched to instead point to a stub that
+// handles the interrupt;
+void
+jit::InterruptRunningCode(JSContext* cx)
+{
+    // If signal handlers weren't installed, then Ion emit normal interrupt
+    // checks and don't need asynchronous interruption.
+    MOZ_ASSERT(sTriedInstallAsyncInterrupt);
+    if (!sHaveAsyncInterrupt)
+        return;
+
+    // Do nothing if we're already handling an interrupt here, to avoid races
+    // below and in JitRuntime::patchIonBackedges.
+    if (!cx->startHandlingJitInterrupt())
+        return;
+
+    // If we are on context's thread, then we can patch Ion backedges without
+    // any special synchronization.
+    if (cx == TlsContext.get()) {
+        RedirectIonBackedgesToInterruptCheck(cx);
+        cx->finishHandlingJitInterrupt();
+        return;
+    }
+
+    // We are not on the runtime's active thread, so we need to halt the
+    // runtime's active thread first.
+#if defined(XP_WIN)
+    // On Windows, we can simply suspend the active thread. SuspendThread can
+    // sporadically fail if the thread is in the middle of a syscall. Rather
+    // than retrying in a loop, just wait for the next request for interrupt.
+    HANDLE thread = (HANDLE)cx->threadNative();
+    if (SuspendThread(thread) != (DWORD)-1) {
+        RedirectIonBackedgesToInterruptCheck(cx);
+        ResumeThread(thread);
+    }
+    cx->finishHandlingJitInterrupt();
+#else
+    // On Unix, we instead deliver an async signal to the active thread which
+    // halts the thread and callers our JitAsyncInterruptHandler (which has
+    // already been installed by EnsureSignalHandlersInstalled).
+    pthread_t thread = (pthread_t)cx->threadNative();
+    pthread_kill(thread, sJitAsyncInterruptSignal);
+#endif
+}
+

js/src/jit/JitCompartment.h

@@ -736,6 +736,20 @@ class MOZ_STACK_CLASS MaybeAutoWritableJitCode
     }
 };
 
+// Ensure the given JSRuntime is set up to use async interrupts. Failure to
+// enable signal handlers indicates some catastrophic failure and creation of
+// the runtime must fail.
+void
+EnsureAsyncInterrupt(JSContext* cx);
+
+// Return whether the async interrupt can be used to interrupt Ion code.
+bool
+HaveAsyncInterrupt();
+
+// Force any currently-executing JIT code to call HandleExecutionInterrupt.
+extern void
+InterruptRunningCode(JSContext* cx);
+
 } // namespace jit
 } // namespace js
 

js/src/jit/JitOptions.cpp

@@ -187,10 +187,6 @@ DefaultJitOptions::DefaultJitOptions()
     // pc-relative jump and call instructions.
     SET_DEFAULT(jumpThreshold, UINT32_MAX);
 
-    // Whether the (ARM) simulators should always interrupt before executing any
-    // instruction.
-    SET_DEFAULT(simulatorAlwaysInterrupt, false);
-
     // Branch pruning heuristic is based on a scoring system, which is look at
     // different metrics and provide a score. The score is computed as a
     // projection where each factor defines the weight of each metric. Then this

js/src/jit/JitOptions.h

@@ -76,7 +76,6 @@ struct DefaultJitOptions
     bool wasmFoldOffsets;
     bool wasmDelayTier2;
     bool ionInterruptWithoutSignals;
-    bool simulatorAlwaysInterrupt;
     uint32_t baselineWarmUpThreshold;
     uint32_t exceptionBailoutThreshold;
     uint32_t frequentBailoutThreshold;

js/src/jit/Lowering.cpp

@@ -15,7 +15,6 @@
 #include "jit/LIR.h"
 #include "jit/MIR.h"
 #include "jit/MIRGraph.h"
-#include "wasm/WasmSignalHandlers.h"
 
 #include "jit/shared/Lowering-shared-inl.h"
 #include "vm/BytecodeUtil-inl.h"
@@ -95,8 +94,8 @@ LIRGenerator::visitIsConstructing(MIsConstructing* ins)
 static void
 TryToUseImplicitInterruptCheck(MIRGraph& graph, MBasicBlock* backedge)
 {
-    // Implicit interrupt checks require wasm signal handlers to be installed.
-    if (!wasm::HaveSignalHandlers() || JitOptions.ionInterruptWithoutSignals)
+    // Implicit interrupt checks require JIT async interrupt support.
+    if (!jit::HaveAsyncInterrupt() || JitOptions.ionInterruptWithoutSignals)
         return;
 
     // To avoid triggering expensive interrupts (backedge patching) in

js/src/jit/arm/Simulator-arm.cpp

@@ -1160,7 +1160,6 @@ Simulator::Simulator(JSContext* cx)
     stackLimit_ = 0;
     pc_modified_ = false;
     icount_ = 0L;
-    wasm_interrupt_ = false;
     break_pc_ = nullptr;
     break_instr_ = 0;
     single_stepping_ = false;
@@ -1594,29 +1593,6 @@ Simulator::registerState()
     return state;
 }
 
-// The signal handler only redirects the PC to the interrupt stub when the PC is
-// in function code. However, this guard is racy for the ARM simulator since the
-// signal handler samples PC in the middle of simulating an instruction and thus
-// the current PC may have advanced once since the signal handler's guard. So we
-// re-check here.
-void
-Simulator::handleWasmInterrupt()
-{
-    if (!wasm::CodeExists)
-        return;
-
-    uint8_t* pc = (uint8_t*)get_pc();
-
-    const wasm::ModuleSegment* ms = nullptr;
-    if (!wasm::InInterruptibleCode(cx_, pc, &ms))
-        return;
-
-    if (!cx_->activation()->asJit()->startWasmInterrupt(registerState()))
-        return;
-
-    set_pc(int32_t(ms->interruptCode()));
-}
-
 static inline JitActivation*
 GetJitActivation(JSContext* cx)
 {
@@ -1659,9 +1635,7 @@ Simulator::handleWasmSegFault(int32_t addr, unsigned numBytes)
 
     const wasm::MemoryAccess* memoryAccess = instance->code().lookupMemoryAccess(pc);
     if (!memoryAccess) {
-        MOZ_ALWAYS_TRUE(act->asJit()->startWasmInterrupt(registerState()));
-        if (!instance->code().containsCodePC(pc))
-            MOZ_CRASH("Cannot map PC to trap handler");
+        act->asJit()->startWasmTrap(wasm::Trap::OutOfBounds, 0, registerState());
         set_pc(int32_t(moduleSegment->outOfBoundsCode()));
         return true;
     }
@@ -4925,19 +4899,6 @@ Simulator::disable_single_stepping()
     single_step_callback_arg_ = nullptr;
 }
 
-static void
-FakeInterruptHandler()
-{
-    JSContext* cx = TlsContext.get();
-    uint8_t* pc = cx->simulator()->get_pc_as<uint8_t*>();
-
-    const wasm::ModuleSegment* ms= nullptr;
-    if (!wasm::InInterruptibleCode(cx, pc, &ms))
-        return;
-
-    cx->simulator()->trigger_wasm_interrupt();
-}
-
 template<bool EnableStopSimAt>
 void
 Simulator::execute()
@@ -4957,16 +4918,9 @@ Simulator::execute()
         } else {
             if (single_stepping_)
                 single_step_callback_(single_step_callback_arg_, this, (void*)program_counter);
-            if (MOZ_UNLIKELY(JitOptions.simulatorAlwaysInterrupt))
-                FakeInterruptHandler();
             SimInstruction* instr = reinterpret_cast<SimInstruction*>(program_counter);
             instructionDecode(instr);
             icount_++;
-
-            if (MOZ_UNLIKELY(wasm_interrupt_)) {
-                handleWasmInterrupt();
-                wasm_interrupt_ = false;
-            }
         }
         program_counter = get_pc();
     }

js/src/jit/arm/Simulator-arm.h

@@ -197,13 +197,6 @@ class Simulator
     template <typename T>
     T get_pc_as() const { return reinterpret_cast<T>(get_pc()); }
 
-    void trigger_wasm_interrupt() {
-        // This can be called several times if a single interrupt isn't caught
-        // and handled by the simulator, but this is fine; once the current
-        // instruction is done executing, the interrupt will be handled anyhow.
-        wasm_interrupt_ = true;
-    }
-
     void enable_single_stepping(SingleStepCallback cb, void* arg);
     void disable_single_stepping();
 
@@ -293,7 +286,6 @@ class Simulator
     void printStopInfo(uint32_t code);
 
     // Handle a wasm interrupt triggered by an async signal handler.
-    void handleWasmInterrupt();
     JS::ProfilingFrameIterator::RegisterState registerState();
 
     // Handle any wasm faults, returning true if the fault was handled.
@@ -426,9 +418,6 @@ class Simulator
     bool pc_modified_;
     int64_t icount_;
 
-    // wasm async interrupt / fault support
-    bool wasm_interrupt_;
-
     // Debugger input.
     char* lastDebuggerInput_;
 

js/src/jit/arm64/vixl/MozSimulator-vixl.cpp

@@ -86,7 +86,6 @@ void Simulator::ResetState() {
   // Reset registers to 0.
   pc_ = nullptr;
   pc_modified_ = false;
-  wasm_interrupt_ = false;
   for (unsigned i = 0; i < kNumberOfRegisters; i++) {
     set_xreg(i, 0xbadbeef);
   }
@@ -195,15 +194,6 @@ void Simulator::ExecuteInstruction() {
   VIXL_ASSERT(IsWordAligned(pc_));
   decoder_->Decode(pc_);
   increment_pc();
-
-  if (MOZ_UNLIKELY(wasm_interrupt_)) {
-    handle_wasm_interrupt();
-    // Just calling set_pc turns the pc_modified_ flag on, which means it doesn't
-    // auto-step after executing the next instruction.  Force that to off so it
-    // will auto-step after executing the first instruction of the handler.
-    pc_modified_ = false;
-    wasm_interrupt_ = false;
-  }
 }
 
 
@@ -230,12 +220,6 @@ bool Simulator::overRecursedWithExtra(uint32_t extra) const {
 }
 
 
-void Simulator::trigger_wasm_interrupt() {
-  MOZ_ASSERT(!wasm_interrupt_);
-  wasm_interrupt_ = true;
-}
-
-
 static inline JitActivation*
 GetJitActivation(JSContext* cx)
 {
@@ -257,32 +241,6 @@ Simulator::registerState()
   return state;
 }
 
-// The signal handler only redirects the PC to the interrupt stub when the PC is
-// in function code. However, this guard is racy for the ARM simulator since the
-// signal handler samples PC in the middle of simulating an instruction and thus
-// the current PC may have advanced once since the signal handler's guard. So we
-// re-check here.
-void Simulator::handle_wasm_interrupt()
-{
-  if (!js::wasm::CodeExists)
-    return;
-
-  uint8_t* pc = (uint8_t*)get_pc();
-
-  const js::wasm::ModuleSegment* ms = nullptr;
-  if (!js::wasm::InInterruptibleCode(cx_, pc, &ms))
-      return;
-
-  JitActivation* act = GetJitActivation(cx_);
-  if (!act)
-      return;
-
-  if (!act->startWasmInterrupt(registerState()))
-      return;
-
-  set_pc((Instruction*)ms->interruptCode());
-}
-
 bool
 Simulator::handle_wasm_seg_fault(uintptr_t addr, unsigned numBytes)
 {
@@ -309,10 +267,7 @@ Simulator::handle_wasm_seg_fault(uintptr_t addr, unsigned numBytes)
 
     const js::wasm::MemoryAccess* memoryAccess = instance->code().lookupMemoryAccess(pc);
     if (!memoryAccess) {
-        if (!act->startWasmInterrupt(registerState()))
-	    MOZ_CRASH("Cannot start interrupt");
-        if (!instance->code().containsCodePC(pc))
-            MOZ_CRASH("Cannot map PC to trap handler");
+        act->startWasmTrap(js::wasm::Trap::OutOfBounds, 0, registerState());
         set_pc((Instruction*)moduleSegment->outOfBoundsCode());
         return true;
     }

js/src/jit/arm64/vixl/Simulator-vixl.h

@@ -746,8 +746,6 @@ class Simulator : public DecoderVisitor {
     pc_modified_ = true;
   }
 
-  void trigger_wasm_interrupt();
-  void handle_wasm_interrupt();
   bool handle_wasm_ill_fault();
   bool handle_wasm_seg_fault(uintptr_t addr, unsigned numBytes);
 
@@ -2583,7 +2581,6 @@ class Simulator : public DecoderVisitor {
   // automatically incremented.
   bool pc_modified_;
   const Instruction* pc_;
-  bool wasm_interrupt_;
 
   static const char* xreg_names[];
   static const char* wreg_names[];

js/src/jit/mips32/Simulator-mips32.cpp

@@ -1269,7 +1269,6 @@ Simulator::Simulator()
     pc_modified_ = false;
     icount_ = 0;
     break_count_ = 0;
-    wasm_interrupt_ = false;
     break_pc_ = nullptr;
     break_instr_ = 0;
 
@@ -1642,32 +1641,6 @@ Simulator::registerState()
     return state;
 }
 
-// The signal handler only redirects the PC to the interrupt stub when the PC is
-// in function code. However, this guard is racy for the simulator since the
-// signal handler samples PC in the middle of simulating an instruction and thus
-// the current PC may have advanced once since the signal handler's guard. So we
-// re-check here.
-void
-Simulator::handleWasmInterrupt()
-{
-    if (!wasm::CodeExists)
-        return;
-
-    void* pc = (void*)get_pc();
-    void* fp = (void*)getRegister(Register::fp);
-
-    JitActivation* activation = TlsContext.get()->activation()->asJit();
-    const wasm::CodeSegment* segment = wasm::LookupCodeSegment(pc);
-    if (!segment || !segment->isModule() || !segment->containsCodePC(pc))
-        return;
-
-    if (!activation->startWasmInterrupt(registerState()))
-         return;
-
-    set_pc(int32_t(segment->asModule()->interruptCode()));
-}
-
-
 // WebAssembly memories contain an extra region of guard pages (see
 // WasmArrayRawBuffer comment). The guard pages catch out-of-bounds accesses
 // using a signal handler that redirects PC to a stub that safely reports an
@@ -1706,9 +1679,7 @@ Simulator::handleWasmFault(int32_t addr, unsigned numBytes)
 
     const wasm::MemoryAccess* memoryAccess = instance->code().lookupMemoryAccess(pc);
     if (!memoryAccess) {
-        MOZ_ALWAYS_TRUE(act->startWasmInterrupt(registerState()));
-        if (!instance->code().containsCodePC(pc))
-            MOZ_CRASH("Cannot map PC to trap handler");
+        act->startWasmTrap(wasm::Trap::OutOfBounds, 0, registerState());
         set_pc(int32_t(moduleSegment->outOfBoundsCode()));
         return true;
     }
@@ -3673,19 +3644,6 @@ Simulator::branchDelayInstructionDecode(SimInstruction* instr)
     instructionDecode(instr);
 }
 
-static void
-FakeInterruptHandler()
-{
-    JSContext* cx = TlsContext.get();
-    uint8_t* pc = cx->simulator()->get_pc_as<uint8_t*>();
-
-    const wasm::ModuleSegment* ms = nullptr;
-    if (!wasm::InInterruptibleCode(cx, pc, &ms))
-        return;
-
-    cx->simulator()->trigger_wasm_interrupt();
-}
-
 template<bool enableStopSimAt>
 void
 Simulator::execute()
@@ -3699,16 +3657,9 @@ Simulator::execute()
             MipsDebugger dbg(this);
             dbg.debug();
         } else {
-            if (MOZ_UNLIKELY(JitOptions.simulatorAlwaysInterrupt))
-                FakeInterruptHandler();
             SimInstruction* instr = reinterpret_cast<SimInstruction*>(program_counter);
             instructionDecode(instr);
             icount_++;
-
-            if (MOZ_UNLIKELY(wasm_interrupt_)) {
-                handleWasmInterrupt();
-                wasm_interrupt_ = false;
-            }
         }
         program_counter = get_pc();
     }

js/src/jit/mips32/Simulator-mips32.h

@@ -202,13 +202,6 @@ class Simulator {
     template <typename T>
     T get_pc_as() const { return reinterpret_cast<T>(get_pc()); }
 
-    void trigger_wasm_interrupt() {
-        // This can be called several times if a single interrupt isn't caught
-        // and handled by the simulator, but this is fine; once the current
-        // instruction is done executing, the interrupt will be handled anyhow.
-        wasm_interrupt_ = true;
-    }
-
     // Accessor to the internal simulator stack area.
     uintptr_t stackLimit() const;
     bool overRecursed(uintptr_t newsp = 0) const;
@@ -304,8 +297,6 @@ class Simulator {
     void increaseStopCounter(uint32_t code);
     void printStopInfo(uint32_t code);
 
-    // Handle a wasm interrupt triggered by an async signal handler.
-    void handleWasmInterrupt();
     JS::ProfilingFrameIterator::RegisterState registerState();
 
     // Handle any wasm faults, returning true if the fault was handled.
@@ -365,9 +356,6 @@ class Simulator {
     int icount_;
     int break_count_;
 
-    // wasm async interrupt / fault support
-    bool wasm_interrupt_;
-
     // Debugger input.
     char* lastDebuggerInput_;
 

js/src/jit/mips64/Simulator-mips64.cpp

@@ -1278,7 +1278,6 @@ Simulator::Simulator()
     pc_modified_ = false;
     icount_ = 0;
     break_count_ = 0;
-    wasm_interrupt_ = false;
     break_pc_ = nullptr;
     break_instr_ = 0;
     single_stepping_ = false;
@@ -1645,35 +1644,6 @@ Simulator::registerState()
     return state;
 }
 
-// The signal handler only redirects the PC to the interrupt stub when the PC is
-// in function code. However, this guard is racy for the simulator since the
-// signal handler samples PC in the middle of simulating an instruction and thus
-// the current PC may have advanced once since the signal handler's guard. So we
-// re-check here.
-void
-Simulator::handleWasmInterrupt()
-{
-    if (!wasm::CodeExists)
-        return;
-
-    void* pc = (void*)get_pc();
-    void* fp = (void*)getRegister(Register::fp);
-
-    JitActivation* activation = TlsContext.get()->activation()->asJit();
-    const wasm::CodeSegment* segment = wasm::LookupCodeSegment(pc);
-    if (!segment || !segment->isModule() || !segment->containsCodePC(pc))
-        return;
-
-    // fp can be null during the prologue/epilogue of the entry function.
-    if (!fp)
-        return;
-
-    if (!activation->startWasmInterrupt(registerState()))
-         return;
-
-    set_pc(int64_t(segment->asModule()->interruptCode()));
-}
-
 // WebAssembly memories contain an extra region of guard pages (see
 // WasmArrayRawBuffer comment). The guard pages catch out-of-bounds accesses
 // using a signal handler that redirects PC to a stub that safely reports an
@@ -1712,9 +1682,7 @@ Simulator::handleWasmFault(uint64_t addr, unsigned numBytes)
 
     const wasm::MemoryAccess* memoryAccess = instance->code().lookupMemoryAccess(pc);
     if (!memoryAccess) {
-        MOZ_ALWAYS_TRUE(act->startWasmInterrupt(registerState()));
-        if (!instance->code().containsCodePC(pc))
-            MOZ_CRASH("Cannot map PC to trap handler");
+        act->startWasmTrap(wasm::Trap::OutOfBounds, 0, registerState());
         set_pc(int64_t(moduleSegment->outOfBoundsCode()));
         return true;
     }
@@ -4062,19 +4030,6 @@ Simulator::disable_single_stepping()
     single_step_callback_arg_ = nullptr;
 }
 
-static void
-FakeInterruptHandler()
-{
-    JSContext* cx = TlsContext.get();
-    uint8_t* pc = cx->simulator()->get_pc_as<uint8_t*>();
-
-    const wasm::ModuleSegment* ms = nullptr;
-    if (!wasm::InInterruptibleCode(cx, pc, &ms))
-        return;
-
-    cx->simulator()->trigger_wasm_interrupt();
-}
-
 template<bool enableStopSimAt>
 void
 Simulator::execute()
@@ -4093,16 +4048,9 @@ Simulator::execute()
         } else {
             if (single_stepping_)
                 single_step_callback_(single_step_callback_arg_, this, (void*)program_counter);
-            if (MOZ_UNLIKELY(JitOptions.simulatorAlwaysInterrupt))
-                FakeInterruptHandler();
             SimInstruction* instr = reinterpret_cast<SimInstruction *>(program_counter);
             instructionDecode(instr);
             icount_++;
-
-            if (MOZ_UNLIKELY(wasm_interrupt_)) {
-                handleWasmInterrupt();
-                wasm_interrupt_ = false;
-            }
         }
         program_counter = get_pc();
     }

js/src/jit/mips64/Simulator-mips64.h

@@ -206,13 +206,6 @@ class Simulator {
     template <typename T>
     T get_pc_as() const { return reinterpret_cast<T>(get_pc()); }
 
-    void trigger_wasm_interrupt() {
-        // This can be called several times if a single interrupt isn't caught
-        // and handled by the simulator, but this is fine; once the current
-        // instruction is done executing, the interrupt will be handled anyhow.
-        wasm_interrupt_ = true;
-    }
-
     void enable_single_stepping(SingleStepCallback cb, void* arg);
     void disable_single_stepping();
 
@@ -319,8 +312,6 @@ class Simulator {
     void increaseStopCounter(uint32_t code);
     void printStopInfo(uint32_t code);
 
-    // Handle a wasm interrupt triggered by an async signal handler.
-    void handleWasmInterrupt();
     JS::ProfilingFrameIterator::RegisterState registerState();
 
     // Handle any wasm faults, returning true if the fault was handled.
@@ -378,9 +369,6 @@ class Simulator {
     int64_t icount_;
     int64_t break_count_;
 
-    // wasm async interrupt support
-    bool wasm_interrupt_;
-
     // Debugger input.
     char* lastDebuggerInput_;
 

js/src/jsapi.cpp

@@ -7272,9 +7272,6 @@ JS_SetGlobalJitCompilerOption(JSContext* cx, JSJitCompilerOption opt, uint32_t v
         }
         jit::JitOptions.jumpThreshold = value;
         break;
-      case JSJITCOMPILER_SIMULATOR_ALWAYS_INTERRUPT:
-        jit::JitOptions.simulatorAlwaysInterrupt = !!value;
-        break;
       case JSJITCOMPILER_SPECTRE_INDEX_MASKING:
         jit::JitOptions.spectreIndexMasking = !!value;
         break;

js/src/vm/JSCompartment.cpp

@@ -183,7 +183,7 @@ JSRuntime::createJitRuntime(JSContext* cx)
     if (!jrt)
         return nullptr;
 
-    // Protect jitRuntime_ from being observed (by InterruptRunningJitCode)
+    // Protect jitRuntime_ from being observed (by jit::InterruptRunningCode)
     // while it is being initialized. Unfortunately, initialization depends on
     // jitRuntime_ being non-null, so we can't just wait to assign jitRuntime_.
     JitRuntime::AutoPreventBackedgePatching apbp(cx->runtime(), jrt);

js/src/vm/JSContext.cpp

@@ -52,7 +52,6 @@
 #include "vm/JSObject.h"
 #include "vm/JSScript.h"
 #include "vm/Shape.h"
-#include "wasm/WasmSignalHandlers.h"
 
 #include "vm/JSObject-inl.h"
 #include "vm/JSScript-inl.h"
@@ -102,7 +101,7 @@ JSContext::init(ContextKind kind)
 {
     // Skip most of the initialization if this thread will not be running JS.
     if (kind == ContextKind::Cooperative) {
-        // Get a platform-native handle for this thread, used by js::InterruptRunningJitCode.
+        // Get a platform-native handle for this thread, used by jit::InterruptRunningCode.
 #ifdef XP_WIN
         size_t openFlags = THREAD_GET_CONTEXT | THREAD_SET_CONTEXT | THREAD_SUSPEND_RESUME |
                            THREAD_QUERY_INFORMATION;
@@ -123,11 +122,12 @@ JSContext::init(ContextKind kind)
             return false;
 
 #ifdef JS_SIMULATOR
-        simulator_ = js::jit::Simulator::Create(this);
+        simulator_ = jit::Simulator::Create(this);
         if (!simulator_)
             return false;
 #endif
 
+        jit::EnsureAsyncInterrupt(this);
         if (!wasm::EnsureSignalHandlers(this))
             return false;
     }

js/src/vm/Runtime.cpp

@@ -44,7 +44,6 @@
 #include "vm/JSScript.h"
 #include "vm/TraceLogging.h"
 #include "vm/TraceLoggingGraph.h"
-#include "wasm/WasmSignalHandlers.h"
 
 #include "gc/GC-inl.h"
 #include "vm/JSContext-inl.h"
@@ -598,7 +597,7 @@ JSContext::requestInterrupt(InterruptMode mode)
         if (fx.isWaiting())
             fx.wake(FutexThread::WakeForJSInterrupt);
         fx.unlock();
-        InterruptRunningJitCode(this);
+        jit::InterruptRunningCode(this);
     }
 }
 

js/src/vm/Runtime.h

@@ -999,18 +999,9 @@ struct JSRuntime : public js::MallocProvider<JSRuntime>
   public:
     js::RuntimeCaches& caches() { return caches_.ref(); }
 
-    // When wasm traps or is interrupted, the signal handler records some data
-    // for unwinding purposes. Wasm code can't interrupt or trap reentrantly.
-    js::ActiveThreadData<
-        mozilla::MaybeOneOf<js::wasm::TrapData, js::wasm::InterruptData>
-    > wasmUnwindData;
-
-    js::wasm::TrapData& wasmTrapData() {
-        return wasmUnwindData.ref().ref<js::wasm::TrapData>();
-    }
-    js::wasm::InterruptData& wasmInterruptData() {
-        return wasmUnwindData.ref().ref<js::wasm::InterruptData>();
-    }
+    // When wasm traps, the signal handler records some data for unwinding
+    // purposes. Wasm code can't trap reentrantly.
+    js::ActiveThreadData<mozilla::Maybe<js::wasm::TrapData>> wasmTrapData;
 
   public:
 #if defined(NIGHTLY_BUILD)

js/src/vm/Stack.cpp

@@ -1574,7 +1574,7 @@ jit::JitActivation::~JitActivation()
     // JitActivations.
     MOZ_ASSERT(!bailoutData_);
 
-    MOZ_ASSERT(!isWasmInterrupted());
+    // Traps get handled immediately.
     MOZ_ASSERT(!isWasmTrapping());
 
     clearRematerializedFrames();
@@ -1742,86 +1742,6 @@ jit::JitActivation::traceIonRecovery(JSTracer* trc)
         it->trace(trc);
 }
 
-bool
-jit::JitActivation::startWasmInterrupt(const JS::ProfilingFrameIterator::RegisterState& state)
-{
-    // fp may be null when first entering wasm code from an interpreter entry
-    // stub.
-    if (!state.fp)
-        return false;
-
-    MOZ_ASSERT(state.pc);
-
-    // Execution can only be interrupted in function code. Afterwards, control
-    // flow does not reenter function code and thus there can be no
-    // interrupt-during-interrupt.
-
-    bool unwound;
-    wasm::UnwindState unwindState;
-    MOZ_ALWAYS_TRUE(wasm::StartUnwinding(state, &unwindState, &unwound));
-
-    void* pc = unwindState.pc;
-
-    if (unwound) {
-        // In the prologue/epilogue, FP might have been fixed up to the
-        // caller's FP, and the caller could be the jit entry. Ignore this
-        // interrupt, in this case, because FP points to a jit frame and not a
-        // wasm one.
-        if (!wasm::LookupCode(pc)->lookupFuncRange(pc))
-            return false;
-    }
-
-    cx_->runtime()->wasmUnwindData.ref().construct<wasm::InterruptData>(pc, state.pc);
-    setWasmExitFP(unwindState.fp);
-
-    MOZ_ASSERT(compartment() == unwindState.fp->tls->instance->compartment());
-    MOZ_ASSERT(isWasmInterrupted());
-    return true;
-}
-
-void
-jit::JitActivation::finishWasmInterrupt()
-{
-    MOZ_ASSERT(isWasmInterrupted());
-
-    cx_->runtime()->wasmUnwindData.ref().destroy();
-    packedExitFP_ = nullptr;
-}
-
-bool
-jit::JitActivation::isWasmInterrupted() const
-{
-    JSRuntime* rt = cx_->runtime();
-    if (!rt->wasmUnwindData.ref().constructed<wasm::InterruptData>())
-        return false;
-
-    Activation* act = cx_->activation();
-    while (act && !act->hasWasmExitFP())
-        act = act->prev();
-
-    if (act != this)
-        return false;
-
-    DebugOnly<const wasm::Frame*> fp = wasmExitFP();
-    DebugOnly<void*> unwindPC = rt->wasmInterruptData().unwindPC;
-    MOZ_ASSERT(fp->instance()->code().containsCodePC(unwindPC));
-    return true;
-}
-
-void*
-jit::JitActivation::wasmInterruptUnwindPC() const
-{
-    MOZ_ASSERT(isWasmInterrupted());
-    return cx_->runtime()->wasmInterruptData().unwindPC;
-}
-
-void*
-jit::JitActivation::wasmInterruptResumePC() const
-{
-    MOZ_ASSERT(isWasmInterrupted());
-    return cx_->runtime()->wasmInterruptData().resumePC;
-}
-
 void
 jit::JitActivation::startWasmTrap(wasm::Trap trap, uint32_t bytecodeOffset,
                                   const wasm::RegisterState& state)
@@ -1842,7 +1762,7 @@ jit::JitActivation::startWasmTrap(wasm::Trap trap, uint32_t bytecodeOffset,
     if (unwound)
         bytecodeOffset = code.lookupCallSite(pc)->lineOrBytecode();
 
-    cx_->runtime()->wasmUnwindData.ref().construct<wasm::TrapData>(pc, trap, bytecodeOffset);
+    cx_->runtime()->wasmTrapData.ref().emplace(pc, trap, bytecodeOffset);
     setWasmExitFP(fp);
 }
 
@@ -1851,7 +1771,7 @@ jit::JitActivation::finishWasmTrap()
 {
     MOZ_ASSERT(isWasmTrapping());
 
-    cx_->runtime()->wasmUnwindData.ref().destroy();
+    cx_->runtime()->wasmTrapData.ref().reset();
     packedExitFP_ = nullptr;
 }
 
@@ -1859,7 +1779,7 @@ bool
 jit::JitActivation::isWasmTrapping() const
 {
     JSRuntime* rt = cx_->runtime();
-    if (!rt->wasmUnwindData.ref().constructed<wasm::TrapData>())
+    if (!rt->wasmTrapData.ref())
         return false;
 
     Activation* act = cx_->activation();
@@ -1870,7 +1790,7 @@ jit::JitActivation::isWasmTrapping() const
         return false;
 
     DebugOnly<const wasm::Frame*> fp = wasmExitFP();
-    DebugOnly<void*> unwindPC = rt->wasmTrapData().pc;
+    DebugOnly<void*> unwindPC = rt->wasmTrapData->pc;
     MOZ_ASSERT(fp->instance()->code().containsCodePC(unwindPC));
     return true;
 }
@@ -1879,14 +1799,14 @@ void*
 jit::JitActivation::wasmTrapPC() const
 {
     MOZ_ASSERT(isWasmTrapping());
-    return cx_->runtime()->wasmTrapData().pc;
+    return cx_->runtime()->wasmTrapData->pc;
 }
 
 uint32_t
 jit::JitActivation::wasmTrapBytecodeOffset() const
 {
     MOZ_ASSERT(isWasmTrapping());
-    return cx_->runtime()->wasmTrapData().bytecodeOffset;
+    return cx_->runtime()->wasmTrapData->bytecodeOffset;
 }
 
 InterpreterFrameIterator&

js/src/vm/Stack.h

@@ -1805,17 +1805,6 @@ class JitActivation : public Activation
         return offsetof(JitActivation, encodedWasmExitReason_);
     }
 
-    // Interrupts are started from the interrupt signal handler (or the ARM
-    // simulator) and cleared by WasmHandleExecutionInterrupt or WasmHandleThrow
-    // when the interrupt is handled.
-
-    // Returns true iff we've entered interrupted state.
-    bool startWasmInterrupt(const wasm::RegisterState& state);
-    void finishWasmInterrupt();
-    bool isWasmInterrupted() const;
-    void* wasmInterruptUnwindPC() const;
-    void* wasmInterruptResumePC() const;
-
     void startWasmTrap(wasm::Trap trap, uint32_t bytecodeOffset, const wasm::RegisterState& state);
     void finishWasmTrap();
     bool isWasmTrapping() const;

js/src/wasm/WasmBaselineCompile.cpp

@@ -3606,8 +3606,7 @@ class BaseCompiler final : public BaseCompilerInterface
 
     void addInterruptCheck()
     {
-        // Always use signals for interrupts with Asm.JS/Wasm
-        MOZ_RELEASE_ASSERT(HaveSignalHandlers());
+        // TODO
     }
 
     void jumpTable(const LabelVector& labels, Label* theTable) {
@@ -9817,8 +9816,6 @@ BaseCompiler::init()
     if (!fr.setupLocals(locals_, sig().args(), debugEnabled_, &localInfo_))
         return false;
 
-    addInterruptCheck();
-
     return true;
 }
 

js/src/wasm/WasmBuiltins.cpp

@@ -69,28 +69,6 @@ CallingActivation()
     return act->asJit();
 }
 
-static void*
-WasmHandleExecutionInterrupt()
-{
-    JitActivation* activation = CallingActivation();
-    MOZ_ASSERT(activation->isWasmInterrupted());
-
-    if (!CheckForInterrupt(activation->cx())) {
-        // If CheckForInterrupt failed, it is time to interrupt execution.
-        // Returning nullptr to the caller will jump to the throw stub which
-        // will call HandleThrow. The JitActivation must stay in the
-        // interrupted state until then so that stack unwinding works in
-        // HandleThrow.
-        return nullptr;
-    }
-
-    // If CheckForInterrupt succeeded, then execution can proceed and the
-    // interrupt is over.
-    void* resumePC = activation->wasmInterruptResumePC();
-    activation->finishWasmInterrupt();
-    return resumePC;
-}
-
 static bool
 WasmHandleDebugTrap()
 {
@@ -219,7 +197,6 @@ wasm::HandleThrow(JSContext* cx, WasmFrameIter& iter)
         frame->leave(cx);
     }
 
-    MOZ_ASSERT(!cx->activation()->asJit()->isWasmInterrupted(), "unwinding clears the interrupt");
     MOZ_ASSERT(!cx->activation()->asJit()->isWasmTrapping(), "unwinding clears the trapping state");
 
     return iter.unwoundAddressOfReturnAddress();
@@ -287,7 +264,7 @@ WasmOldReportTrap(int32_t trapIndex)
 static void
 WasmReportTrap()
 {
-    Trap trap = TlsContext.get()->runtime()->wasmTrapData().trap;
+    Trap trap = TlsContext.get()->runtime()->wasmTrapData->trap;
     WasmOldReportTrap(int32_t(trap));
 }
 
@@ -511,9 +488,6 @@ void*
 wasm::AddressOf(SymbolicAddress imm, ABIFunctionType* abiType)
 {
     switch (imm) {
-      case SymbolicAddress::HandleExecutionInterrupt:
-        *abiType = Args_General0;
-        return FuncCast(WasmHandleExecutionInterrupt, *abiType);
       case SymbolicAddress::HandleDebugTrap:
         *abiType = Args_General0;
         return FuncCast(WasmHandleDebugTrap, *abiType);
@@ -692,7 +666,6 @@ wasm::NeedsBuiltinThunk(SymbolicAddress sym)
     // Some functions don't want to a thunk, because they already have one or
     // they don't have frame info.
     switch (sym) {
-      case SymbolicAddress::HandleExecutionInterrupt: // GenerateInterruptExit
       case SymbolicAddress::HandleDebugTrap:          // GenerateDebugTrapStub
       case SymbolicAddress::HandleThrow:              // GenerateThrowStub
       case SymbolicAddress::ReportTrap:               // GenerateTrapExit
@@ -874,8 +847,8 @@ PopulateTypedNatives(TypedNativeToFuncPtrMap* typedNatives)
 // things:
 //  - bridging the few differences between the internal wasm ABI and the external
 //    native ABI (viz. float returns on x86 and soft-fp ARM)
-//  - executing an exit prologue/epilogue which in turn allows any asynchronous
-//    interrupt to see the full stack up to the wasm operation that called out
+//  - executing an exit prologue/epilogue which in turn allows any profiling
+//    iterator to see the full stack up to the wasm operation that called out
 //
 // Thunks are created for two kinds of C++ callees, enumerated above:
 //  - SymbolicAddress: for statically compiled calls in the wasm module

js/src/wasm/WasmCode.cpp

@@ -335,7 +335,6 @@ ModuleSegment::initialize(Tier tier,
                           const CodeRangeVector& codeRanges)
 {
     MOZ_ASSERT(bytes_ == nullptr);
-    MOZ_ASSERT(linkData.interruptOffset);
     MOZ_ASSERT(linkData.outOfBoundsOffset);
     MOZ_ASSERT(linkData.unalignedAccessOffset);
     MOZ_ASSERT(linkData.trapOffset);
@@ -343,7 +342,6 @@ ModuleSegment::initialize(Tier tier,
     tier_ = tier;
     bytes_ = Move(codeBytes);
     length_ = codeLength;
-    interruptCode_ = bytes_.get() + linkData.interruptOffset;
     outOfBoundsCode_ = bytes_.get() + linkData.outOfBoundsOffset;
     unalignedAccessCode_ = bytes_.get() + linkData.unalignedAccessOffset;
     trapCode_ = bytes_.get() + linkData.trapOffset;

js/src/wasm/WasmCode.h

@@ -144,9 +144,8 @@ class ModuleSegment : public CodeSegment
 {
     Tier            tier_;
 
-    // These are pointers into code for stubs used for asynchronous
-    // signal-handler control-flow transfer.
-    uint8_t*        interruptCode_;
+    // These are pointers into code for stubs used for signal-handler
+    // control-flow transfer.
     uint8_t*        outOfBoundsCode_;
     uint8_t*        unalignedAccessCode_;
     uint8_t*        trapCode_;
@@ -173,7 +172,6 @@ class ModuleSegment : public CodeSegment
     ModuleSegment()
       : CodeSegment(),
         tier_(Tier(-1)),
-        interruptCode_(nullptr),
         outOfBoundsCode_(nullptr),
         unalignedAccessCode_(nullptr),
         trapCode_(nullptr)
@@ -195,7 +193,6 @@ class ModuleSegment : public CodeSegment
 
     Tier tier() const { return tier_; }
 
-    uint8_t* interruptCode() const { return interruptCode_; }
     uint8_t* outOfBoundsCode() const { return outOfBoundsCode_; }
     uint8_t* unalignedAccessCode() const { return unalignedAccessCode_; }
     uint8_t* trapCode() const { return trapCode_; }

js/src/wasm/WasmFrameIter.cpp

@@ -61,27 +61,6 @@ WasmFrameIter::WasmFrameIter(JitActivation* activation, wasm::Frame* fp)
         return;
     }
 
-    // When asynchronously interrupted, exitFP is set to the interrupted frame
-    // itself and so we do not want to skip it. Instead, we can recover the
-    // Code and CodeRange from the JitActivation, which are set when control
-    // flow was interrupted. There is no CallSite (b/c the interrupt was
-    // async), but this is fine because CallSite is only used for line number
-    // for which we can use the beginning of the function from the CodeRange
-    // instead.
-
-    if (activation->isWasmInterrupted()) {
-        code_ = &fp_->tls->instance->code();
-        MOZ_ASSERT(code_ == LookupCode(activation->wasmInterruptUnwindPC()));
-
-        codeRange_ = code_->lookupFuncRange(activation->wasmInterruptUnwindPC());
-        MOZ_ASSERT(codeRange_);
-
-        lineOrBytecode_ = codeRange_->funcLineOrBytecode();
-
-        MOZ_ASSERT(!done());
-        return;
-    }
-
     // Otherwise, execution exits wasm code via an exit stub which sets exitFP
     // to the exit stub's frame. Thus, in this case, we want to start iteration
     // at the caller of the exit frame, whose Code, CodeRange and CallSite are
@@ -111,14 +90,12 @@ WasmFrameIter::operator++()
     // popping each frame and, once onLeaveFrame is called for a given frame,
     // that frame must not be visible to subsequent stack iteration (or it
     // could be added as a "new" frame just as it becomes garbage).  When the
-    // frame is "interrupted", then exitFP is included in the callstack
-    // (otherwise, it is skipped, as explained above). So to unwind the
-    // innermost frame, we just clear the interrupt state.
+    // frame is trapping, then exitFP is included in the callstack (otherwise,
+    // it is skipped, as explained above). So to unwind the innermost frame, we
+    // just clear the trapping state.
 
     if (unwind_ == Unwind::True) {
-        if (activation_->isWasmInterrupted())
-            activation_->finishWasmInterrupt();
-        else if (activation_->isWasmTrapping())
+        if (activation_->isWasmTrapping())
             activation_->finishWasmTrap();
         activation_->setWasmExitFP(fp_);
     }
@@ -760,10 +737,8 @@ ProfilingFrameIterator::initFromExitFP(const Frame* fp)
     // This means that the innermost frame is skipped. This is fine because:
     //  - for import exit calls, the innermost frame is a thunk, so the first
     //    frame that shows up is the function calling the import;
-    //  - for Math and other builtin calls as well as interrupts, we note the
-    //    absence of an exit reason and inject a fake "builtin" frame; and
-    //  - for async interrupts, we just accept that we'll lose the innermost
-    //    frame.
+    //  - for Math and other builtin calls, we note the absence of an exit
+    //    reason and inject a fake "builtin" frame; and
     switch (codeRange_->kind()) {
       case CodeRange::InterpEntry:
         callerPC_ = nullptr;
@@ -791,7 +766,6 @@ ProfilingFrameIterator::initFromExitFP(const Frame* fp)
       case CodeRange::OutOfBoundsExit:
       case CodeRange::UnalignedExit:
       case CodeRange::Throw:
-      case CodeRange::Interrupt:
       case CodeRange::FarJumpIsland:
         MOZ_CRASH("Unexpected CodeRange kind");
     }
@@ -1012,11 +986,6 @@ js::wasm::StartUnwinding(const RegisterState& registers, UnwindState* unwindStat
         // the entire activation. To simplify testing, we simply pretend throw
         // stubs have already popped the entire stack.
         return false;
-      case CodeRange::Interrupt:
-        // When the PC is in the async interrupt stub, the fp may be garbage and
-        // so we cannot blindly unwind it. Since the percent of time spent in
-        // the interrupt stub is extremely small, just ignore the stack.
-        return false;
     }
 
     unwindState->code = code;
@@ -1142,7 +1111,6 @@ ProfilingFrameIterator::operator++()
         MOZ_CRASH("should have had null caller fp");
       case CodeRange::JitEntry:
         MOZ_CRASH("should have been guarded above");
-      case CodeRange::Interrupt:
       case CodeRange::Throw:
         MOZ_CRASH("code range doesn't have frame");
     }
@@ -1155,7 +1123,6 @@ ThunkedNativeToDescription(SymbolicAddress func)
 {
     MOZ_ASSERT(NeedsBuiltinThunk(func));
     switch (func) {
-      case SymbolicAddress::HandleExecutionInterrupt:
       case SymbolicAddress::HandleDebugTrap:
       case SymbolicAddress::HandleThrow:
       case SymbolicAddress::ReportTrap:
@@ -1311,8 +1278,7 @@ ProfilingFrameIterator::label() const
       case CodeRange::OutOfBoundsExit:   return "out-of-bounds stub (in wasm)";
       case CodeRange::UnalignedExit:     return "unaligned trap stub (in wasm)";
       case CodeRange::FarJumpIsland:     return "interstitial (in wasm)";
-      case CodeRange::Throw:             MOZ_FALLTHROUGH;
-      case CodeRange::Interrupt:         MOZ_CRASH("does not have a frame");
+      case CodeRange::Throw:             MOZ_CRASH("does not have a frame");
     }
 
     MOZ_CRASH("bad code range kind");

js/src/wasm/WasmFrameIter.h

@@ -49,12 +49,6 @@ struct CallableOffsets;
 //
 // If you want to handle every kind of frames (including JS jit frames), use
 // JitFrameIter.
-//
-// The one exception is that this iterator may be called from the interrupt
-// callback which may be called asynchronously from asm.js code; in this case,
-// the backtrace may not be correct. That being said, we try our best printing
-// an informative message to the user and at least the name of the innermost
-// function stack frame.
 
 class WasmFrameIter
 {
@@ -158,7 +152,7 @@ class ExitReason
 };
 
 // Iterates over the frames of a single wasm JitActivation, given an
-// asynchronously-interrupted thread's state.
+// asynchronously-profiled thread's state.
 class ProfilingFrameIterator
 {
     const Code* code_;

js/src/wasm/WasmGenerator.cpp

@@ -550,10 +550,6 @@ ModuleGenerator::noteCodeRange(uint32_t codeRangeIndex, const CodeRange& codeRan
         MOZ_ASSERT(!linkDataTier_->unalignedAccessOffset);
         linkDataTier_->unalignedAccessOffset = codeRange.begin();
         break;
-      case CodeRange::Interrupt:
-        MOZ_ASSERT(!linkDataTier_->interruptOffset);
-        linkDataTier_->interruptOffset = codeRange.begin();
-        break;
       case CodeRange::TrapExit:
         MOZ_ASSERT(!linkDataTier_->trapOffset);
         linkDataTier_->trapOffset = codeRange.begin();

js/src/wasm/WasmIonCompile.cpp

@@ -251,8 +251,6 @@ class FunctionCompiler
                 return false;
         }
 
-        addInterruptCheck();
-
         return true;
     }
 
@@ -1035,8 +1033,7 @@ class FunctionCompiler
 
     void addInterruptCheck()
     {
-        // We rely on signal handlers for interrupts on Asm.JS/Wasm
-        MOZ_RELEASE_ASSERT(wasm::HaveSignalHandlers());
+        // TODO
     }
 
     MDefinition* extractSimdElement(unsigned lane, MDefinition* base, MIRType type, SimdSign sign)

js/src/wasm/WasmModule.h

@@ -42,7 +42,6 @@ struct CompileArgs;
 
 struct LinkDataTierCacheablePod
 {
-    uint32_t interruptOffset;
     uint32_t outOfBoundsOffset;
     uint32_t unalignedAccessOffset;
     uint32_t trapOffset;

js/src/wasm/WasmProcess.cpp

@@ -50,15 +50,14 @@ class ProcessCodeSegmentMap
     CodeSegmentVector segments1_;
     CodeSegmentVector segments2_;
 
-    // Because of sampling/interruptions/stack iteration in general, the
-    // thread running wasm might need to know to which CodeSegment the
-    // current PC belongs, during a call to lookup(). A lookup is a
-    // read-only operation, and we don't want to take a lock then
+    // Because of profiling, the thread running wasm might need to know to which
+    // CodeSegment the current PC belongs, during a call to lookup(). A lookup
+    // is a read-only operation, and we don't want to take a lock then
     // (otherwise, we could have a deadlock situation if an async lookup
     // happened on a given thread that was holding mutatorsMutex_ while getting
-    // interrupted/sampled). Since the writer could be modifying the data that
-    // is getting looked up, the writer functions use spin-locks to know if
-    // there are any observers (i.e. calls to lookup()) of the atomic data.
+    // sampled). Since the writer could be modifying the data that is getting
+    // looked up, the writer functions use spin-locks to know if there are any
+    // observers (i.e. calls to lookup()) of the atomic data.
 
     Atomic<size_t> observers_;
 

js/src/wasm/WasmProcess.h

@@ -30,7 +30,7 @@ class CodeSegment;
 
 // These methods return the wasm::CodeSegment (resp. wasm::Code) containing
 // the given pc, if any exist in the process. These methods do not take a lock,
-// and thus are safe to use in a profiling or async interrupt context.
+// and thus are safe to use in a profiling context.
 
 const CodeSegment*
 LookupCodeSegment(const void* pc, const CodeRange** codeRange = nullptr);

js/src/wasm/WasmSignalHandlers.cpp

@@ -31,20 +31,32 @@
 
 #include "vm/ArrayBufferObject-inl.h"
 
+#if defined(XP_WIN)
+# include "util/Windows.h"
+#else
+# include <signal.h>
+# include <sys/mman.h>
+#endif
+
+#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
+# include <sys/ucontext.h> // for ucontext_t, mcontext_t
+#endif
+
+#if defined(__x86_64__)
+# if defined(__DragonFly__)
+#  include <machine/npx.h> // for union savefpu
+# elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || \
+       defined(__NetBSD__) || defined(__OpenBSD__)
+#  include <machine/fpu.h> // for struct savefpu/fxsave64
+# endif
+#endif
+
 using namespace js;
 using namespace js::jit;
 using namespace js::wasm;
 
 using JS::GenericNaN;
 using mozilla::DebugOnly;
-using mozilla::PodArrayZero;
-
-#if defined(ANDROID)
-# include <sys/system_properties.h>
-# if defined(MOZ_LINKER)
-extern "C" MFBT_API bool IsSignalHandlingBroken();
-# endif
-#endif
 
 // Crashing inside the signal handler can cause the handler to be recursively
 // invoked, eventually blowing the stack without actually showing a crash
@@ -257,38 +269,20 @@ struct AutoSignalHandler
 #  define RFP_sig(p) ((p)->uc_mcontext.mc_regs[30])
 # endif
 #elif defined(XP_DARWIN)
-# define EIP_sig(p) ((p)->uc_mcontext->__ss.__eip)
-# define EBP_sig(p) ((p)->uc_mcontext->__ss.__ebp)
-# define ESP_sig(p) ((p)->uc_mcontext->__ss.__esp)
-# define RIP_sig(p) ((p)->uc_mcontext->__ss.__rip)
-# define RBP_sig(p) ((p)->uc_mcontext->__ss.__rbp)
-# define RSP_sig(p) ((p)->uc_mcontext->__ss.__rsp)
-# define R14_sig(p) ((p)->uc_mcontext->__ss.__lr)
-# define R15_sig(p) ((p)->uc_mcontext->__ss.__pc)
+# define EIP_sig(p) ((p)->thread.uts.ts32.__eip)
+# define EBP_sig(p) ((p)->thread.uts.ts32.__ebp)
+# define ESP_sig(p) ((p)->thread.uts.ts32.__esp)
+# define RIP_sig(p) ((p)->thread.__rip)
+# define RBP_sig(p) ((p)->thread.__rbp)
+# define RSP_sig(p) ((p)->thread.__rsp)
+# define R11_sig(p) ((p)->thread.__r[11])
+# define R13_sig(p) ((p)->thread.__sp)
+# define R14_sig(p) ((p)->thread.__lr)
+# define R15_sig(p) ((p)->thread.__pc)
 #else
 # error "Don't know how to read/write to the thread state via the mcontext_t."
 #endif
 
-#if defined(XP_WIN)
-# include "util/Windows.h"
-#else
-# include <signal.h>
-# include <sys/mman.h>
-#endif
-
-#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
-# include <sys/ucontext.h> // for ucontext_t, mcontext_t
-#endif
-
-#if defined(__x86_64__)
-# if defined(__DragonFly__)
-#  include <machine/npx.h> // for union savefpu
-# elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || \
-       defined(__NetBSD__) || defined(__OpenBSD__)
-#  include <machine/fpu.h> // for struct savefpu/fxsave64
-# endif
-#endif
-
 #if defined(ANDROID)
 // Not all versions of the Android NDK define ucontext_t or mcontext_t.
 // Detect this and provide custom but compatible definitions. Note that these
@@ -369,38 +363,30 @@ enum { REG_EIP = 14 };
 # endif  // !defined(__BIONIC_HAVE_UCONTEXT_T)
 #endif // defined(ANDROID)
 
-#if !defined(XP_WIN)
-# define CONTEXT ucontext_t
-#endif
-
-// Define a context type for use in the emulator code. This is usually just
-// the same as CONTEXT, but on Mac we use a different structure since we call
-// into the emulator code from a Mach exception handler rather than a
-// sigaction-style signal handler.
 #if defined(XP_DARWIN)
 # if defined(__x86_64__)
 struct macos_x64_context {
     x86_thread_state64_t thread;
     x86_float_state64_t float_;
 };
-#  define EMULATOR_CONTEXT macos_x64_context
+#  define CONTEXT macos_x64_context
 # elif defined(__i386__)
 struct macos_x86_context {
     x86_thread_state_t thread;
     x86_float_state_t float_;
 };
-#  define EMULATOR_CONTEXT macos_x86_context
+#  define CONTEXT macos_x86_context
 # elif defined(__arm__)
 struct macos_arm_context {
     arm_thread_state_t thread;
     arm_neon_state_t float_;
 };
-#  define EMULATOR_CONTEXT macos_arm_context
+#  define CONTEXT macos_arm_context
 # else
 #  error Unsupported architecture
 # endif
-#else
-# define EMULATOR_CONTEXT CONTEXT
+#elif !defined(XP_WIN)
+# define CONTEXT ucontext_t
 #endif
 
 #if defined(_M_X64) || defined(__x86_64__)
@@ -428,14 +414,10 @@ struct macos_arm_context {
 # define LR_sig(p) R31_sig(p)
 #endif
 
-#if defined(PC_sig) && defined(FP_sig) && defined(SP_sig)
-# define KNOWS_MACHINE_STATE
-#endif
-
 static uint8_t**
 ContextToPC(CONTEXT* context)
 {
-#ifdef KNOWS_MACHINE_STATE
+#ifdef PC_sig
     return reinterpret_cast<uint8_t**>(&PC_sig(context));
 #else
     MOZ_CRASH();
@@ -445,116 +427,48 @@ ContextToPC(CONTEXT* context)
 static uint8_t*
 ContextToFP(CONTEXT* context)
 {
-#ifdef KNOWS_MACHINE_STATE
+#ifdef FP_sig
     return reinterpret_cast<uint8_t*>(FP_sig(context));
 #else
     MOZ_CRASH();
 #endif
 }
 
-#ifdef KNOWS_MACHINE_STATE
 static uint8_t*
 ContextToSP(CONTEXT* context)
 {
+#ifdef SP_sig
     return reinterpret_cast<uint8_t*>(SP_sig(context));
+#else
+    MOZ_CRASH();
+#endif
 }
 
-# if defined(__arm__) || defined(__aarch64__) || defined(__mips__)
+#if defined(__arm__) || defined(__aarch64__) || defined(__mips__)
 static uint8_t*
 ContextToLR(CONTEXT* context)
 {
+# ifdef LR_sig
     return reinterpret_cast<uint8_t*>(LR_sig(context));
-}
-# endif
-#endif // KNOWS_MACHINE_STATE
-
-#if defined(XP_DARWIN)
-
-static uint8_t**
-ContextToPC(EMULATOR_CONTEXT* context)
-{
-# if defined(__x86_64__)
-    static_assert(sizeof(context->thread.__rip) == sizeof(void*),
-                  "stored IP should be compile-time pointer-sized");
-    return reinterpret_cast<uint8_t**>(&context->thread.__rip);
-# elif defined(__i386__)
-    static_assert(sizeof(context->thread.uts.ts32.__eip) == sizeof(void*),
-                  "stored IP should be compile-time pointer-sized");
-    return reinterpret_cast<uint8_t**>(&context->thread.uts.ts32.__eip);
-# elif defined(__arm__)
-    static_assert(sizeof(context->thread.__pc) == sizeof(void*),
-                  "stored IP should be compile-time pointer-sized");
-    return reinterpret_cast<uint8_t**>(&context->thread.__pc);
 # else
-#  error Unsupported architecture
+    MOZ_CRASH();
 # endif
 }
-
-static uint8_t*
-ContextToFP(EMULATOR_CONTEXT* context)
-{
-# if defined(__x86_64__)
-    return (uint8_t*)context->thread.__rbp;
-# elif defined(__i386__)
-    return (uint8_t*)context->thread.uts.ts32.__ebp;
-# elif defined(__arm__)
-    return (uint8_t*)context->thread.__r[11];
-# else
-#  error Unsupported architecture
-# endif
-}
-
-# if defined(__arm__) || defined(__aarch64__)
-static uint8_t*
-ContextToLR(EMULATOR_CONTEXT* context)
-{
-    return (uint8_t*)context->thread.__lr;
-}
-# endif
-
-static uint8_t*
-ContextToSP(EMULATOR_CONTEXT* context)
-{
-# if defined(__x86_64__)
-    return (uint8_t*)context->thread.__rsp;
-# elif defined(__i386__)
-    return (uint8_t*)context->thread.uts.ts32.__esp;
-# elif defined(__arm__)
-    return (uint8_t*)context->thread.__sp;
-# else
-#  error Unsupported architecture
-# endif
-}
-
-static JS::ProfilingFrameIterator::RegisterState
-ToRegisterState(EMULATOR_CONTEXT* context)
-{
-    JS::ProfilingFrameIterator::RegisterState state;
-    state.fp = ContextToFP(context);
-    state.pc = *ContextToPC(context);
-    state.sp = ContextToSP(context);
-# if defined(__arm__) || defined(__aarch64__)
-    state.lr = ContextToLR(context);
-# endif
-    return state;
-}
-#endif // XP_DARWIN
+#endif
 
 static JS::ProfilingFrameIterator::RegisterState
 ToRegisterState(CONTEXT* context)
 {
-#ifdef KNOWS_MACHINE_STATE
     JS::ProfilingFrameIterator::RegisterState state;
     state.fp = ContextToFP(context);
     state.pc = *ContextToPC(context);
     state.sp = ContextToSP(context);
-# if defined(__arm__) || defined(__aarch64__) || defined(__mips__)
+#if defined(__arm__) || defined(__aarch64__) || defined(__mips__)
     state.lr = ContextToLR(context);
-# endif
-    return state;
 #else
-    MOZ_CRASH();
+    state.lr = (void*)UINTPTR_MAX;
 #endif
+    return state;
 }
 
 #if defined(WASM_HUGE_MEMORY)
@@ -653,7 +567,7 @@ AddressOfFPRegisterSlot(CONTEXT* context, FloatRegisters::Encoding encoding)
 }
 
 MOZ_COLD static void*
-AddressOfGPRegisterSlot(EMULATOR_CONTEXT* context, Registers::Code code)
+AddressOfGPRegisterSlot(CONTEXT* context, Registers::Code code)
 {
     switch (code) {
       case X86Encoding::rax: return &RAX_sig(context);
@@ -678,7 +592,7 @@ AddressOfGPRegisterSlot(EMULATOR_CONTEXT* context, Registers::Code code)
 }
 # else
 MOZ_COLD static void*
-AddressOfFPRegisterSlot(EMULATOR_CONTEXT* context, FloatRegisters::Encoding encoding)
+AddressOfFPRegisterSlot(CONTEXT* context, FloatRegisters::Encoding encoding)
 {
     switch (encoding) {
       case X86Encoding::xmm0:  return &context->float_.__fpu_xmm0;
@@ -703,7 +617,7 @@ AddressOfFPRegisterSlot(EMULATOR_CONTEXT* context, FloatRegisters::Encoding enco
 }
 
 MOZ_COLD static void*
-AddressOfGPRegisterSlot(EMULATOR_CONTEXT* context, Registers::Code code)
+AddressOfGPRegisterSlot(CONTEXT* context, Registers::Code code)
 {
     switch (code) {
       case X86Encoding::rax: return &context->thread.__rax;
@@ -729,20 +643,20 @@ AddressOfGPRegisterSlot(EMULATOR_CONTEXT* context, Registers::Code code)
 # endif  // !XP_DARWIN
 #elif defined(JS_CODEGEN_ARM64)
 MOZ_COLD static void*
-AddressOfFPRegisterSlot(EMULATOR_CONTEXT* context, FloatRegisters::Encoding encoding)
+AddressOfFPRegisterSlot(CONTEXT* context, FloatRegisters::Encoding encoding)
 {
     MOZ_CRASH("NYI - asm.js not supported yet on this platform");
 }
 
 MOZ_COLD static void*
-AddressOfGPRegisterSlot(EMULATOR_CONTEXT* context, Registers::Code code)
+AddressOfGPRegisterSlot(CONTEXT* context, Registers::Code code)
 {
     MOZ_CRASH("NYI - asm.js not supported yet on this platform");
 }
 #endif
 
 MOZ_COLD static void
-SetRegisterToCoercedUndefined(EMULATOR_CONTEXT* context, size_t size,
+SetRegisterToCoercedUndefined(CONTEXT* context, size_t size,
                               const Disassembler::OtherOperand& value)
 {
     if (value.kind() == Disassembler::OtherOperand::FPR)
@@ -752,7 +666,7 @@ SetRegisterToCoercedUndefined(EMULATOR_CONTEXT* context, size_t size,
 }
 
 MOZ_COLD static void
-SetRegisterToLoadedValue(EMULATOR_CONTEXT* context, SharedMem<void*> addr, size_t size,
+SetRegisterToLoadedValue(CONTEXT* context, SharedMem<void*> addr, size_t size,
                          const Disassembler::OtherOperand& value)
 {
     if (value.kind() == Disassembler::OtherOperand::FPR)
@@ -762,14 +676,14 @@ SetRegisterToLoadedValue(EMULATOR_CONTEXT* context, SharedMem<void*> addr, size_
 }
 
 MOZ_COLD static void
-SetRegisterToLoadedValueSext32(EMULATOR_CONTEXT* context, SharedMem<void*> addr, size_t size,
+SetRegisterToLoadedValueSext32(CONTEXT* context, SharedMem<void*> addr, size_t size,
                                const Disassembler::OtherOperand& value)
 {
     SetGPRegToLoadedValueSext32(addr, size, AddressOfGPRegisterSlot(context, value.gpr()));
 }
 
 MOZ_COLD static void
-StoreValueFromRegister(EMULATOR_CONTEXT* context, SharedMem<void*> addr, size_t size,
+StoreValueFromRegister(CONTEXT* context, SharedMem<void*> addr, size_t size,
                        const Disassembler::OtherOperand& value)
 {
     if (value.kind() == Disassembler::OtherOperand::FPR)
@@ -781,7 +695,7 @@ StoreValueFromRegister(EMULATOR_CONTEXT* context, SharedMem<void*> addr, size_t
 }
 
 MOZ_COLD static uint8_t*
-ComputeAccessAddress(EMULATOR_CONTEXT* context, const Disassembler::ComplexAddress& address)
+ComputeAccessAddress(CONTEXT* context, const Disassembler::ComplexAddress& address)
 {
     MOZ_RELEASE_ASSERT(!address.isPCRelative(), "PC-relative addresses not supported yet");
 
@@ -806,7 +720,7 @@ ComputeAccessAddress(EMULATOR_CONTEXT* context, const Disassembler::ComplexAddre
 }
 
 MOZ_COLD static void
-HandleMemoryAccess(EMULATOR_CONTEXT* context, uint8_t* pc, uint8_t* faultingAddress,
+HandleMemoryAccess(CONTEXT* context, uint8_t* pc, uint8_t* faultingAddress,
                    const ModuleSegment* segment, const Instance& instance, JitActivation* activation,
                    uint8_t** ppc)
 {
@@ -818,7 +732,7 @@ HandleMemoryAccess(EMULATOR_CONTEXT* context, uint8_t* pc, uint8_t* faultingAddr
         // experimental SIMD.js or Atomics. When these are converted to
         // non-experimental wasm features, this case, as well as outOfBoundsCode,
         // can be removed.
-        MOZ_ALWAYS_TRUE(activation->startWasmInterrupt(ToRegisterState(context)));
+        activation->startWasmTrap(wasm::Trap::OutOfBounds, 0, ToRegisterState(context));
         *ppc = segment->outOfBoundsCode();
         return;
     }
@@ -962,7 +876,7 @@ HandleMemoryAccess(EMULATOR_CONTEXT* context, uint8_t* pc, uint8_t* faultingAddr
 #else // WASM_HUGE_MEMORY
 
 MOZ_COLD static void
-HandleMemoryAccess(EMULATOR_CONTEXT* context, uint8_t* pc, uint8_t* faultingAddress,
+HandleMemoryAccess(CONTEXT* context, uint8_t* pc, uint8_t* faultingAddress,
                    const ModuleSegment* segment, const Instance& instance, JitActivation* activation,
                    uint8_t** ppc)
 {
@@ -971,7 +885,7 @@ HandleMemoryAccess(EMULATOR_CONTEXT* context, uint8_t* pc, uint8_t* faultingAddr
     const MemoryAccess* memoryAccess = instance.code().lookupMemoryAccess(pc);
     if (!memoryAccess) {
         // See explanation in the WASM_HUGE_MEMORY HandleMemoryAccess.
-        MOZ_ALWAYS_TRUE(activation->startWasmInterrupt(ToRegisterState(context)));
+        activation->startWasmTrap(wasm::Trap::OutOfBounds, 0, ToRegisterState(context));
         *ppc = segment->outOfBoundsCode();
         return;
     }
@@ -1019,33 +933,8 @@ HandleFault(PEXCEPTION_POINTERS exception)
     MOZ_ASSERT(activation);
 
     const Instance* instance = LookupFaultingInstance(*moduleSegment, pc, ContextToFP(context));
-    if (!instance) {
-        // On Windows, it is possible for InterruptRunningJitCode to execute
-        // between a faulting instruction and the handling of the fault due
-        // to InterruptRunningJitCode's use of SuspendThread. When this happens,
-        // after ResumeThread, the exception handler is called with pc equal to
-        // ModuleSegment.interrupt, which is logically wrong. The Right Thing would
-        // be for the OS to make fault-handling atomic (so that CONTEXT.pc was
-        // always the logically-faulting pc). Fortunately, we can detect this
-        // case and silence the exception ourselves (the exception will
-        // retrigger after the interrupt jumps back to resumePC).
-        return activation->isWasmInterrupted() &&
-               pc == moduleSegment->interruptCode() &&
-               moduleSegment->containsCodePC(activation->wasmInterruptResumePC());
-    }
-
-    // In the same race-with-interrupt situation above, it's *also* possible
-    // that the reported 'pc' is the pre-interrupt pc, not post-interrupt
-    // moduleSegment->interruptCode (this may be windows-version-specific). In
-    // this case, lookupTrap()/lookupMemoryAccess() will all succeed causing the
-    // pc to be redirected *again* (to a trap stub), leading to the interrupt
-    // stub never being called. Since the goal of the async interrupt is to break
-    // out iloops and trapping does just that, this is fine, we just clear the
-    // "interrupted" state.
-    if (activation->isWasmInterrupted()) {
-        MOZ_ASSERT(activation->wasmInterruptResumePC() == pc);
-        activation->finishWasmInterrupt();
-    }
+    if (!instance)
+        return false;
 
     if (record->ExceptionCode == EXCEPTION_ILLEGAL_INSTRUCTION) {
         Trap trap;
@@ -1125,7 +1014,7 @@ HandleMachException(JSContext* cx, const ExceptionRequest& request)
     mach_port_t cxThread = request.body.thread.name;
 
     // Read out the JSRuntime thread's register state.
-    EMULATOR_CONTEXT context;
+    CONTEXT context;
 # if defined(__x86_64__)
     unsigned int thread_state_count = x86_THREAD_STATE64_COUNT;
     unsigned int float_state_count = x86_FLOAT_STATE64_COUNT;
@@ -1446,7 +1335,7 @@ HandleFault(int signum, siginfo_t* info, void* ctx)
         // partly overlaps the end of the heap.  In this case, it is an out-of-bounds
         // error and we should signal that properly, but to do so we must inspect
         // the operand of the failed access.
-        MOZ_ALWAYS_TRUE(activation->startWasmInterrupt(ToRegisterState(context)));
+        activation->startWasmTrap(wasm::Trap::UnalignedAccess, 0, ToRegisterState(context));
         *ppc = moduleSegment->unalignedAccessCode();
         return true;
     }
@@ -1495,119 +1384,8 @@ WasmFaultHandler(int signum, siginfo_t* info, void* context)
 }
 # endif // XP_WIN || XP_DARWIN || assume unix
 
-static void
-RedirectIonBackedgesToInterruptCheck(JSContext* cx)
-{
-    if (!cx->runtime()->hasJitRuntime())
-        return;
-    jit::JitRuntime* jitRuntime = cx->runtime()->jitRuntime();
-    Zone* zone = cx->zoneRaw();
-    if (zone && !zone->isAtomsZone()) {
-        // If the backedge list is being mutated, the pc must be in C++ code and
-        // thus not in a JIT iloop. We assume that the interrupt flag will be
-        // checked at least once before entering JIT code (if not, no big deal;
-        // the browser will just request another interrupt in a second).
-        if (!jitRuntime->preventBackedgePatching()) {
-            jit::JitZoneGroup* jzg = zone->group()->jitZoneGroup;
-            jzg->patchIonBackedges(cx, jit::JitZoneGroup::BackedgeInterruptCheck);
-        }
-    }
-}
-
-bool
-wasm::InInterruptibleCode(JSContext* cx, uint8_t* pc, const ModuleSegment** ms)
-{
-    // Only interrupt in function code so that the frame iterators have the
-    // invariant that resumePC always has a function CodeRange and we can't
-    // get into any weird interrupt-during-interrupt-stub cases.
-
-    if (!cx->compartment())
-        return false;
-
-    const CodeSegment* cs = LookupCodeSegment(pc);
-    if (!cs || !cs->isModule())
-        return false;
-
-    *ms = cs->asModule();
-    return !!(*ms)->code().lookupFuncRange(pc);
-}
-
-// The return value indicates whether the PC was changed, not whether there was
-// a failure.
-static bool
-RedirectJitCodeToInterruptCheck(JSContext* cx, CONTEXT* context)
-{
-    // Jitcode may only be modified on the runtime's active thread.
-    if (cx != cx->runtime()->activeContext())
-        return false;
-
-    // The faulting thread is suspended so we can access cx fields that can
-    // normally only be accessed by the cx's active thread.
-    AutoNoteSingleThreadedRegion anstr;
-
-    RedirectIonBackedgesToInterruptCheck(cx);
-
-#ifdef JS_SIMULATOR
-    uint8_t* pc = cx->simulator()->get_pc_as<uint8_t*>();
-#else
-    uint8_t* pc = *ContextToPC(context);
-#endif
-
-    const ModuleSegment* moduleSegment = nullptr;
-    if (!InInterruptibleCode(cx, pc, &moduleSegment))
-        return false;
-
-#ifdef JS_SIMULATOR
-    // The checks performed by the !JS_SIMULATOR path happen in
-    // Simulator::handleWasmInterrupt.
-    cx->simulator()->trigger_wasm_interrupt();
-#else
-    // Only probe cx->activation() after we know the pc is in wasm code. This
-    // way we don't depend on signal-safe update of cx->activation().
-    JitActivation* activation = cx->activation()->asJit();
-
-    // The out-of-bounds/unaligned trap paths which call startWasmInterrupt() go
-    // through function code, so test if already interrupted. These paths are
-    // temporary though, so this case can be removed later.
-    if (activation->isWasmInterrupted())
-        return false;
-
-    if (!activation->startWasmInterrupt(ToRegisterState(context)))
-        return false;
-
-    *ContextToPC(context) = moduleSegment->interruptCode();
-#endif
-
-    return true;
-}
-
-#if !defined(XP_WIN)
-// For the interrupt signal, pick a signal number that:
-//  - is not otherwise used by mozilla or standard libraries
-//  - defaults to nostop and noprint on gdb/lldb so that noone is bothered
-// SIGVTALRM a relative of SIGALRM, so intended for user code, but, unlike
-// SIGALRM, not used anywhere else in Mozilla.
-static const int sInterruptSignal = SIGVTALRM;
-
-static void
-JitInterruptHandler(int signum, siginfo_t* info, void* context)
-{
-    if (JSContext* cx = TlsContext.get()) {
-
-#if defined(JS_SIMULATOR_ARM) || defined(JS_SIMULATOR_MIPS32) || defined(JS_SIMULATOR_MIPS64)
-        SimulatorProcess::ICacheCheckingDisableCount++;
-#endif
-
-        RedirectJitCodeToInterruptCheck(cx, (CONTEXT*)context);
-
-#if defined(JS_SIMULATOR_ARM) || defined(JS_SIMULATOR_MIPS32) || defined(JS_SIMULATOR_MIPS64)
-        SimulatorProcess::cacheInvalidatedBySignalHandler_ = true;
-        SimulatorProcess::ICacheCheckingDisableCount--;
-#endif
-
-        cx->finishHandlingJitInterrupt();
-    }
-}
+#if defined(ANDROID) && defined(MOZ_LINKER)
+extern "C" MFBT_API bool IsSignalHandlingBroken();
 #endif
 
 static bool sTriedInstallSignalHandlers = false;
@@ -1621,73 +1399,35 @@ ProcessHasSignalHandlers()
         return sHaveSignalHandlers;
     sTriedInstallSignalHandlers = true;
 
-#if defined(ANDROID)
-# if !defined(__aarch64__)
-    // Before Android 4.4 (SDK version 19), there is a bug
-    //   https://android-review.googlesource.com/#/c/52333
-    // in Bionic's pthread_join which causes pthread_join to return early when
-    // pthread_kill is used (on any thread). Nobody expects the pthread_cond_wait
-    // EINTRquisition.
-    char version_string[PROP_VALUE_MAX];
-    PodArrayZero(version_string);
-    if (__system_property_get("ro.build.version.sdk", version_string) > 0) {
-        if (atol(version_string) < 19)
-            return false;
-    }
-# endif
-# if defined(MOZ_LINKER)
+#if defined(ANDROID) && defined(MOZ_LINKER)
     // Signal handling is broken on some android systems.
     if (IsSignalHandlingBroken())
         return false;
-# endif
 #endif
 
-    // The interrupt handler allows the active thread to be paused from another
-    // thread (see InterruptRunningJitCode).
-#if defined(XP_WIN)
-    // Windows uses SuspendThread to stop the active thread from another thread.
-#else
-    struct sigaction interruptHandler;
-    interruptHandler.sa_flags = SA_SIGINFO;
-    interruptHandler.sa_sigaction = &JitInterruptHandler;
-    sigemptyset(&interruptHandler.sa_mask);
-    struct sigaction prev;
-    if (sigaction(sInterruptSignal, &interruptHandler, &prev))
-        MOZ_CRASH("unable to install interrupt handler");
-
-    // There shouldn't be any other handlers installed for sInterruptSignal. If
-    // there are, we could always forward, but we need to understand what we're
-    // doing to avoid problematic interference.
-    if ((prev.sa_flags & SA_SIGINFO && prev.sa_sigaction) ||
-        (prev.sa_handler != SIG_DFL && prev.sa_handler != SIG_IGN))
-    {
-        MOZ_CRASH("contention for interrupt signal");
-    }
-#endif // defined(XP_WIN)
-
     // Initalize ThreadLocal flag used by WasmFaultHandler
     sAlreadyInSignalHandler.infallibleInit();
 
     // Install a SIGSEGV handler to handle safely-out-of-bounds asm.js heap
     // access and/or unaligned accesses.
-# if defined(XP_WIN)
-#  if defined(MOZ_ASAN)
+#if defined(XP_WIN)
+# if defined(MOZ_ASAN)
     // Under ASan we need to let the ASan runtime's ShadowExceptionHandler stay
     // in the first handler position. This requires some coordination with
     // MemoryProtectionExceptionHandler::isDisabled().
     const bool firstHandler = false;
-#  else
+# else
     // Otherwise, WasmFaultHandler needs to go first, so that we can recover
     // from wasm faults and continue execution without triggering handlers
     // such as MemoryProtectionExceptionHandler that assume we are crashing.
     const bool firstHandler = true;
-#  endif
+# endif
     if (!AddVectoredExceptionHandler(firstHandler, WasmFaultHandler))
         return false;
-# elif defined(XP_DARWIN)
+#elif defined(XP_DARWIN)
     // OSX handles seg faults via the Mach exception handler above, so don't
     // install WasmFaultHandler.
-# else
+#else
     // SA_NODEFER allows us to reenter the signal handler if we crash while
     // handling the signal, and fall through to the Breakpad handler by testing
     // handlingSegFault.
@@ -1700,7 +1440,7 @@ ProcessHasSignalHandlers()
     if (sigaction(SIGSEGV, &faultHandler, &sPrevSEGVHandler))
         MOZ_CRASH("unable to install segv handler");
 
-#  if defined(JS_CODEGEN_ARM)
+# if defined(JS_CODEGEN_ARM)
     // On Arm Handle Unaligned Accesses
     struct sigaction busHandler;
     busHandler.sa_flags = SA_SIGINFO | SA_NODEFER | SA_ONSTACK;
@@ -1708,7 +1448,7 @@ ProcessHasSignalHandlers()
     sigemptyset(&busHandler.sa_mask);
     if (sigaction(SIGBUS, &busHandler, &sPrevSIGBUSHandler))
         MOZ_CRASH("unable to install sigbus handler");
-#  endif
+# endif
 
     // Install a handler to handle the instructions that are emitted to implement
     // wasm traps.
@@ -1718,7 +1458,7 @@ ProcessHasSignalHandlers()
     sigemptyset(&wasmTrapHandler.sa_mask);
     if (sigaction(kWasmTrapSignal, &wasmTrapHandler, &sPrevWasmTrapHandler))
         MOZ_CRASH("unable to install wasm trap handler");
-# endif
+#endif
 
     sHaveSignalHandlers = true;
     return true;
@@ -1746,61 +1486,3 @@ wasm::HaveSignalHandlers()
     MOZ_ASSERT(sTriedInstallSignalHandlers);
     return sHaveSignalHandlers;
 }
-
-// JSRuntime::requestInterrupt sets interrupt_ (which is checked frequently by
-// C++ code at every Baseline JIT loop backedge) and jitStackLimit_ (which is
-// checked at every Baseline and Ion JIT function prologue). The remaining
-// sources of potential iloops (Ion loop backedges and all wasm code) are
-// handled by this function:
-//  1. Ion loop backedges are patched to instead point to a stub that handles
-//     the interrupt;
-//  2. if the active thread's pc is inside wasm code, the pc is updated to point
-//     to a stub that handles the interrupt.
-void
-js::InterruptRunningJitCode(JSContext* cx)
-{
-    // If signal handlers weren't installed, then Ion and wasm emit normal
-    // interrupt checks and don't need asynchronous interruption.
-    if (!HaveSignalHandlers())
-        return;
-
-    // Do nothing if we're already handling an interrupt here, to avoid races
-    // below and in JitRuntime::patchIonBackedges.
-    if (!cx->startHandlingJitInterrupt())
-        return;
-
-    // If we are on context's thread, then: pc is not in wasm code (so nothing
-    // to do for wasm) and we can patch Ion backedges without any special
-    // synchronization.
-    if (cx == TlsContext.get()) {
-        RedirectIonBackedgesToInterruptCheck(cx);
-        cx->finishHandlingJitInterrupt();
-        return;
-    }
-
-    // We are not on the runtime's active thread, so to do 1 and 2 above, we need
-    // to halt the runtime's active thread first.
-#if defined(XP_WIN)
-    // On Windows, we can simply suspend the active thread and work directly on
-    // its context from this thread. SuspendThread can sporadically fail if the
-    // thread is in the middle of a syscall. Rather than retrying in a loop,
-    // just wait for the next request for interrupt.
-    HANDLE thread = (HANDLE)cx->threadNative();
-    if (SuspendThread(thread) != (DWORD)-1) {
-        CONTEXT context;
-        context.ContextFlags = CONTEXT_FULL;
-        if (GetThreadContext(thread, &context)) {
-            if (RedirectJitCodeToInterruptCheck(cx, &context))
-                SetThreadContext(thread, &context);
-        }
-        ResumeThread(thread);
-    }
-    cx->finishHandlingJitInterrupt();
-#else
-    // On Unix, we instead deliver an async signal to the active thread which
-    // halts the thread and callers our JitInterruptHandler (which has already
-    // been installed by EnsureSignalHandlersInstalled).
-    pthread_t thread = (pthread_t)cx->threadNative();
-    pthread_kill(thread, sInterruptSignal);
-#endif
-}

js/src/wasm/WasmSignalHandlers.h

@@ -30,11 +30,6 @@
 #include "wasm/WasmTypes.h"
 
 namespace js {
-
-// Force any currently-executing asm.js/ion code to call HandleExecutionInterrupt.
-extern void
-InterruptRunningJitCode(JSContext* cx);
-
 namespace wasm {
 
 // Ensure the given JSRuntime is set up to use signals. Failure to enable signal
@@ -43,18 +38,11 @@ namespace wasm {
 MOZ_MUST_USE bool
 EnsureSignalHandlers(JSContext* cx);
 
-// Return whether signals can be used in this process for interrupts or
-// asm.js/wasm out-of-bounds.
+// Return whether signals can be used in this process for asm.js/wasm
+// out-of-bounds.
 bool
 HaveSignalHandlers();
 
-class ModuleSegment;
-
-// Returns true if wasm code is on top of the activation stack (and fills out
-// the code segment outparam in this case), or false otherwise.
-bool
-InInterruptibleCode(JSContext* cx, uint8_t* pc, const ModuleSegment** ms);
-
 #if defined(XP_DARWIN)
 // On OSX we are forced to use the lower-level Mach exception mechanism instead
 // of Unix signals. Mach exceptions are not handled on the victim's stack but
@@ -79,23 +67,7 @@ class MachExceptionHandler
 };
 #endif
 
-// Typed wrappers encapsulating the data saved by the signal handler on async
-// interrupt or trap. On interrupt, the PC at which to resume is saved. On trap,
-// the bytecode offset to be reported in callstacks is saved.
-
-struct InterruptData
-{
-    // The pc to use for unwinding purposes which is kept consistent with fp at
-    // call boundaries.
-    void* unwindPC;
-
-    // The pc at which we should return if the interrupt doesn't stop execution.
-    void* resumePC;
-
-    InterruptData(void* unwindPC, void* resumePC)
-      : unwindPC(unwindPC), resumePC(resumePC)
-    {}
-};
+// On trap, the bytecode offset to be reported in callstacks is saved.
 
 struct TrapData
 {

js/src/wasm/WasmStubs.cpp

@@ -1251,8 +1251,6 @@ GenerateImportJitExit(MacroAssembler& masm, const FuncImport& fi, Label* throwLa
     //   need to worry about rooting anymore.
     // - or the value needs to be rooted, but nothing can cause a GC between
     //   here and CoerceInPlace, which roots before coercing to a primitive.
-    //   In particular, this is true because wasm::InInterruptibleCode will
-    //   return false when PC is in the jit exit.
 
     // The JIT callee clobbers all registers, including WasmTlsReg and
     // FramePointer, so restore those here. During this sequence of
@@ -1618,227 +1616,10 @@ static const LiveRegisterSet AllRegsExceptSP(
     FloatRegisterSet(FloatRegisters::AllMask));
 #endif
 
-// The async interrupt-callback exit is called from arbitrarily-interrupted wasm
-// code. It calls into the WasmHandleExecutionInterrupt to determine whether we must
-// really halt execution which can reenter the VM (e.g., to display the slow
-// script dialog). If execution is not interrupted, this stub must carefully
-// preserve *all* register state. If execution is interrupted, the entire
-// activation will be popped by the throw stub, so register state does not need
-// to be restored.
-static bool
-GenerateInterruptExit(MacroAssembler& masm, Label* throwLabel, Offsets* offsets)
-{
-    AssertExpectedSP(masm);
-    masm.haltingAlign(CodeAlignment);
-
-    offsets->begin = masm.currentOffset();
-
-#if defined(JS_CODEGEN_X86) || defined(JS_CODEGEN_X64)
-    // Be very careful here not to perturb the machine state before saving it
-    // to the stack. In particular, add/sub instructions may set conditions in
-    // the flags register.
-    masm.push(Imm32(0));            // space used as return address, updated below
-    masm.setFramePushed(0);         // set to 0 now so that framePushed is offset of return address
-    masm.PushFlags();               // after this we are safe to use sub
-    masm.PushRegsInMask(AllRegsExceptSP); // save all GP/FP registers (except SP)
-
-    // We know that StackPointer is word-aligned, but not necessarily
-    // stack-aligned, so we need to align it dynamically.
-    masm.moveStackPtrTo(ABINonVolatileReg);
-    masm.andToStackPtr(Imm32(~(ABIStackAlignment - 1)));
-    if (ShadowStackSpace)
-        masm.subFromStackPtr(Imm32(ShadowStackSpace));
-
-    // Make the call to C++, which preserves ABINonVolatileReg.
-    masm.assertStackAlignment(ABIStackAlignment);
-    masm.call(SymbolicAddress::HandleExecutionInterrupt);
-
-    // HandleExecutionInterrupt returns null if execution is interrupted and
-    // the resumption pc otherwise.
-    masm.branchTestPtr(Assembler::Zero, ReturnReg, ReturnReg, throwLabel);
-
-    // Restore the stack pointer then store resumePC into the stack slow that
-    // will be popped by the 'ret' below.
-    masm.moveToStackPtr(ABINonVolatileReg);
-    masm.storePtr(ReturnReg, Address(StackPointer, masm.framePushed()));
-
-    // Restore the machine state to before the interrupt. After popping flags,
-    // no instructions can be executed which set flags.
-    masm.PopRegsInMask(AllRegsExceptSP);
-    masm.PopFlags();
-
-    // Return to the resumePC stored into this stack slot above.
-    MOZ_ASSERT(masm.framePushed() == 0);
-    masm.ret();
-#elif defined(JS_CODEGEN_MIPS32) || defined(JS_CODEGEN_MIPS64)
-    // Reserve space to store resumePC and HeapReg.
-    masm.subFromStackPtr(Imm32(2 * sizeof(intptr_t)));
-    // Set to zero so we can use masm.framePushed() below.
-    masm.setFramePushed(0);
-
-    // Save all registers, except sp.
-    masm.PushRegsInMask(AllUserRegsExceptSP);
-
-    // Save the stack pointer and FCSR in a non-volatile registers.
-    masm.moveStackPtrTo(s0);
-    masm.as_cfc1(s1, Assembler::FCSR);
-
-    // Align the stack.
-    masm.ma_and(StackPointer, StackPointer, Imm32(~(ABIStackAlignment - 1)));
-
-    // Store HeapReg into the reserved space.
-    masm.storePtr(HeapReg, Address(s0, masm.framePushed() + sizeof(intptr_t)));
-
-# ifdef USES_O32_ABI
-    // MIPS ABI requires rewserving stack for registes $a0 to $a3.
-    masm.subFromStackPtr(Imm32(4 * sizeof(intptr_t)));
-# endif
-
-    masm.assertStackAlignment(ABIStackAlignment);
-    masm.call(SymbolicAddress::HandleExecutionInterrupt);
-
-    masm.branchTestPtr(Assembler::Zero, ReturnReg, ReturnReg, throwLabel);
-
-    // This will restore stack to the address before the call.
-    masm.moveToStackPtr(s0);
-
-    // Restore FCSR.
-    masm.as_ctc1(s1, Assembler::FCSR);
-
-    // Store resumePC into the reserved space.
-    masm.storePtr(ReturnReg, Address(s0, masm.framePushed()));
-
-    masm.PopRegsInMask(AllUserRegsExceptSP);
-
-    // Pop resumePC into PC. Clobber HeapReg to make the jump and restore it
-    // during jump delay slot.
-    masm.loadPtr(Address(StackPointer, 0), HeapReg);
-    // Reclaim the reserve space.
-    masm.addToStackPtr(Imm32(2 * sizeof(intptr_t)));
-    masm.as_jr(HeapReg);
-    masm.loadPtr(Address(StackPointer, -int32_t(sizeof(intptr_t))), HeapReg);
-#elif defined(JS_CODEGEN_ARM)
-    {
-        // Be careful not to clobber scratch registers before they are saved.
-        ScratchRegisterScope scratch(masm);
-        SecondScratchRegisterScope secondScratch(masm);
-
-        // Reserve a word to receive the return address.
-        masm.as_alu(StackPointer, StackPointer, Imm8(4), OpSub);
-
-        // Set framePushed to 0 now so that framePushed can be used later as the
-        // stack offset to the return-address space reserved above.
-        masm.setFramePushed(0);
-
-        // Save all GP/FP registers (except PC and SP).
-        masm.PushRegsInMask(AllRegsExceptPCSP);
-    }
-
-    // Save SP, APSR and FPSCR in non-volatile registers.
-    masm.as_mrs(r4);
-    masm.as_vmrs(r5);
-    masm.mov(sp, r6);
-
-    // We know that StackPointer is word-aligned, but not necessarily
-    // stack-aligned, so we need to align it dynamically.
-    masm.andToStackPtr(Imm32(~(ABIStackAlignment - 1)));
-
-    // Make the call to C++, which preserves the non-volatile registers.
-    masm.assertStackAlignment(ABIStackAlignment);
-    masm.call(SymbolicAddress::HandleExecutionInterrupt);
-
-    // HandleExecutionInterrupt returns null if execution is interrupted and
-    // the resumption pc otherwise.
-    masm.branchTestPtr(Assembler::Zero, ReturnReg, ReturnReg, throwLabel);
-
-    // Restore the stack pointer then store resumePC into the stack slot that
-    // will be popped by the 'ret' below.
-    masm.mov(r6, sp);
-    masm.storePtr(ReturnReg, Address(sp, masm.framePushed()));
-
-    // Restore the machine state to before the interrupt. After popping flags,
-    // no instructions can be executed which set flags.
-    masm.as_vmsr(r5);
-    masm.as_msr(r4);
-    masm.PopRegsInMask(AllRegsExceptPCSP);
-
-    // Return to the resumePC stored into this stack slot above.
-    MOZ_ASSERT(masm.framePushed() == 0);
-    masm.ret();
-#elif defined(JS_CODEGEN_ARM64)
-    // Reserve aligned space to receive the saved LR and the new return address.
-    static constexpr unsigned SAVE_AREA = 16;
-    static constexpr unsigned LR_OFFSET = 0;
-    static constexpr unsigned PC_OFFSET = 8;
-    masm.subFromStackPtr(Imm32(SAVE_AREA));
-
-    uint32_t oldFramePushed = masm.framePushed();
-
-    // Set framePushed to 0 now so that framePushed can be used later as the
-    // stack offset to the return-address space reserved above.
-    masm.setFramePushed(0);
-
-    // Store LR specially so that PushRegsInMask gets an even number of words to
-    // store.
-    masm.Str(ARMRegister(lr, 64), vixl::MemOperand(sp, LR_OFFSET));
-
-    // Save all GP/FP registers (except SP and LR).
-    masm.PushRegsInMask(AllRegsExceptSPLR);
-
-    MOZ_ASSERT(masm.framePushed() % 16 == 0);
-
-    // Save SP, APSR and FPSCR in non-volatile registers, prior instructions
-    // must not update the flags.
-    masm.Mrs(x20, vixl::NZCV);
-    masm.Mrs(x21, vixl::FPCR);
-    masm.Mov(x22, sp);
-
-    // The stack is already aligned.
-    static_assert(ABIStackAlignment == 16, "ARM64 SP alignment");
-
-    // Make the call to C++, which preserves the non-volatile registers.
-    masm.assertStackAlignment(ABIStackAlignment);
-    masm.call(SymbolicAddress::HandleExecutionInterrupt);
-
-    // HandleExecutionInterrupt returns null if execution is interrupted and
-    // the resumption pc otherwise.
-    masm.branchTestPtr(Assembler::Zero, ReturnReg, ReturnReg, throwLabel);
-
-    // Restore the stack pointer then store resumePC into a stack slot where the
-    // return code below will find it.
-    masm.Mov(sp, x22);
-    masm.Str(ARMRegister(ReturnReg, 64), vixl::MemOperand(sp, masm.framePushed() + PC_OFFSET));
-
-    // Restore the machine state to before the interrupt. After popping flags,
-    // no instructions can be executed which set flags.
-    masm.Msr(vixl::FPCR, x21);
-    masm.Msr(vixl::NZCV, x20);
-    masm.PopRegsInMask(AllRegsExceptSPLR);
-    masm.Ldr(ARMRegister(lr, 64), vixl::MemOperand(sp, LR_OFFSET));
-
-    // Return to the resumePC stored into this stack slot above.
-    MOZ_ASSERT(masm.framePushed() == 0);
-
-    masm.setFramePushed(oldFramePushed);
-
-    // We can clobber PseudoStackPointer because wasm code does not use it.
-    masm.loadPtr(Address(masm.getStackPointer(), PC_OFFSET), PseudoStackPointer);
-    masm.addToStackPtr(Imm32(SAVE_AREA));
-    masm.Ret(PseudoStackPointer64);
-#elif defined (JS_CODEGEN_NONE)
-    MOZ_CRASH();
-#else
-# error "Unknown architecture!"
-#endif
-
-    return FinishOffsets(masm, offsets);
-}
-
 // Generate a stub that restores the stack pointer to what it was on entry to
 // the wasm activation, sets the return register to 'false' and then executes a
 // return which will return from this wasm activation to the caller. This stub
-// should only be called after the caller has reported an error (or, in the case
-// of the interrupt stub, intends to interrupt execution).
+// should only be called after the caller has reported an error.
 static bool
 GenerateThrowStub(MacroAssembler& masm, Label* throwLabel, Offsets* offsets)
 {
@@ -1849,8 +1630,7 @@ GenerateThrowStub(MacroAssembler& masm, Label* throwLabel, Offsets* offsets)
 
     offsets->begin = masm.currentOffset();
 
-    // The throw stub can be jumped to from an async interrupt that is halting
-    // execution. Thus the stack pointer can be unaligned and we must align it
+    // Conservatively, the stack pointer can be unaligned and we must align it
     // dynamically.
     masm.andToStackPtr(Imm32(~(ABIStackAlignment - 1)));
     if (ShadowStackSpace)
@@ -2044,19 +1824,12 @@ wasm::GenerateStubs(const ModuleEnvironment& env, const FuncImportVector& import
     if (!code->codeRanges.emplaceBack(CodeRange::TrapExit, offsets))
         return false;
 
-    if (!GenerateInterruptExit(masm, &throwLabel, &offsets))
+    CallableOffsets callableOffsets;
+    if (!GenerateDebugTrapStub(masm, &throwLabel, &callableOffsets))
         return false;
-    if (!code->codeRanges.emplaceBack(CodeRange::Interrupt, offsets))
+    if (!code->codeRanges.emplaceBack(CodeRange::DebugTrap, callableOffsets))
         return false;
 
-    {
-        CallableOffsets offsets;
-        if (!GenerateDebugTrapStub(masm, &throwLabel, &offsets))
-            return false;
-        if (!code->codeRanges.emplaceBack(CodeRange::DebugTrap, offsets))
-            return false;
-    }
-
     if (!GenerateThrowStub(masm, &throwLabel, &offsets))
         return false;
     if (!code->codeRanges.emplaceBack(CodeRange::Throw, offsets))

js/src/wasm/WasmTypes.cpp

@@ -790,7 +790,6 @@ CodeRange::CodeRange(Kind kind, Offsets offsets)
       case UnalignedExit:
       case TrapExit:
       case Throw:
-      case Interrupt:
         break;
       default:
         MOZ_CRASH("should use more specific constructor");

js/src/wasm/WasmTypes.h

@@ -1064,7 +1064,6 @@ class CodeRange
         OutOfBoundsExit,   // stub jumped to by non-standard asm.js SIMD/Atomics
         UnalignedExit,     // stub jumped to by wasm Atomics and non-standard
                            // ARM unaligned trap
-        Interrupt,         // stub executes asynchronously to interrupt wasm
         Throw              // special stack-unwinding stub jumped to by other stubs
     };
 
@@ -1373,7 +1372,6 @@ enum class SymbolicAddress
     LogD,
     PowD,
     ATan2D,
-    HandleExecutionInterrupt,
     HandleDebugTrap,
     HandleThrow,
     ReportTrap,