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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
*
* Copyright 2025 Mozilla Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "wasm/WasmContext.h"
#include "jit/JitRuntime.h"
#include "js/friend/StackLimits.h"
#include "js/TracingAPI.h"
#include "vm/JSContext.h"
#include "wasm/WasmPI.h"
#ifdef XP_WIN
// We only need the `windows.h` header, but this file can get unified built
// with WasmSignalHandlers.cpp, which requires `winternal.h` to be included
// before the `windows.h` header, and so we must include it here for that case.
# include <winternl.h> // must include before util/WindowsWrapper.h's `#undef`s
# include "util/WindowsWrapper.h"
#endif
using namespace js::wasm;
Context::Context()
: triedToInstallSignalHandlers(false),
haveSignalHandlers(false),
stackLimit(JS::NativeStackLimitMin),
mainStackLimit(JS::NativeStackLimitMin)
#ifdef ENABLE_WASM_JSPI
,
activeSuspender_(nullptr)
#endif
{
}
Context::~Context() {
#ifdef ENABLE_WASM_JSPI
MOZ_ASSERT(activeSuspender_ == nullptr);
MOZ_ASSERT(suspenders_.empty());
#endif
}
void Context::initStackLimit(JSContext* cx) {
// The wasm stack limit is the same as the jit stack limit. We also don't
// use the stack limit for triggering interrupts.
stackLimit = cx->jitStackLimitNoInterrupt;
mainStackLimit = stackLimit;
// See the comment on wasm::Context for why we do this.
#ifdef ENABLE_WASM_JSPI
# if defined(_WIN32)
tib_ = reinterpret_cast<_NT_TIB*>(::NtCurrentTeb());
tibStackBase_ = tib_->StackBase;
tibStackLimit_ = tib_->StackLimit;
# endif
#endif
}
#ifdef ENABLE_WASM_JSPI
SuspenderObject* Context::findSuspenderForStackAddress(
const void* stackAddress) {
// TODO: add a fast path for the main stack that avoids linear search. We
// need an accurate main stack base/limit for that.
for (auto iter = suspenders_.iter(); !iter.done(); iter.next()) {
SuspenderObject* object = iter.get();
if (object->isActive() && object->hasStackAddress(stackAddress)) {
return object;
}
}
return nullptr;
}
void Context::trace(JSTracer* trc) {
if (activeSuspender_) {
TraceEdge(trc, &activeSuspender_, "suspender");
}
}
void Context::traceRoots(JSTracer* trc) {
// The suspendedStacks_ contains suspended stacks frames that need to be
// traced only during minor GC. The major GC tracing is happening via
// SuspenderObject::trace.
// Non-suspended stack frames are traced as part of TraceJitActivations.
if (!trc->isTenuringTracer()) {
return;
}
gc::AssertRootMarkingPhase(trc);
for (auto iter = suspenders_.iter(); !iter.done(); iter.next()) {
SuspenderObject* object = iter.get();
if (object->state() == SuspenderState::Suspended) {
TraceSuspendableStack(trc, object);
}
}
}
void Context::enterSuspendableStack(JSContext* cx, SuspenderObject* suspender) {
MOZ_ASSERT(!activeSuspender_);
activeSuspender_ = suspender;
stackLimit = suspender->stackMemoryLimitForJit();
// See the comment on wasm::Context for why we do this.
# if defined(_WIN32)
tibStackBase_ = tib_->StackBase;
tibStackLimit_ = tib_->StackLimit;
tib_->StackBase = reinterpret_cast<void*>(suspender->stackMemoryBase());
tib_->StackLimit =
reinterpret_cast<void*>(suspender->stackMemoryLimitForSystem());
# endif
# ifdef DEBUG
cx->runtime()->jitRuntime()->disallowArbitraryCode();
# endif
}
void Context::leaveSuspendableStack(JSContext* cx) {
MOZ_ASSERT(activeSuspender_);
activeSuspender_ = nullptr;
stackLimit = mainStackLimit;
// See the comment on wasm::Context for why we do this.
# if defined(_WIN32)
tib_->StackBase = static_cast<void*>(tibStackBase_);
tib_->StackLimit = static_cast<void*>(tibStackLimit_);
# endif
# ifdef DEBUG
cx->runtime()->jitRuntime()->clearDisallowArbitraryCode();
# endif
}
#endif