diff options
Diffstat (limited to 'js/src/gc/Tracer.cpp')
| -rw-r--r-- | js/src/gc/Tracer.cpp | 377 |
1 files changed, 377 insertions, 0 deletions
diff --git a/js/src/gc/Tracer.cpp b/js/src/gc/Tracer.cpp new file mode 100644 index 0000000000..00d4ff0ff7 --- /dev/null +++ b/js/src/gc/Tracer.cpp @@ -0,0 +1,377 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- + * vim: set ts=8 sts=2 et sw=2 tw=80: + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "gc/Tracer.h" + +#include "mozilla/DebugOnly.h" + +#include "NamespaceImports.h" + +#include "gc/GCInternals.h" +#include "gc/Marking.h" +#include "gc/PublicIterators.h" +#include "gc/Zone.h" +#include "util/Memory.h" +#include "util/Text.h" +#include "vm/BigIntType.h" +#include "vm/JSFunction.h" +#include "vm/JSScript.h" +#include "vm/Shape.h" +#include "vm/SymbolType.h" + +#include "gc/GC-inl.h" +#include "gc/Marking-inl.h" +#include "vm/Realm-inl.h" + +using namespace js; +using namespace js::gc; +using mozilla::DebugOnly; + +/*** Callback Tracer Dispatch ***********************************************/ + +template <typename T> +bool DoCallback(GenericTracer* trc, T** thingp, const char* name) { + CheckTracedThing(trc, *thingp); + JS::AutoTracingName ctx(trc, name); + + T* thing = *thingp; + T* post = DispatchToOnEdge(trc, thing); + if (post != thing) { + *thingp = post; + } + + return post; +} +#define INSTANTIATE_ALL_VALID_TRACE_FUNCTIONS(name, type, _, _1) \ + template bool DoCallback<type>(GenericTracer*, type**, const char*); +JS_FOR_EACH_TRACEKIND(INSTANTIATE_ALL_VALID_TRACE_FUNCTIONS); +#undef INSTANTIATE_ALL_VALID_TRACE_FUNCTIONS + +template <typename T> +bool DoCallback(GenericTracer* trc, T* thingp, const char* name) { + JS::AutoTracingName ctx(trc, name); + + // Return true by default. For some types the lambda below won't be called. + bool ret = true; + auto thing = MapGCThingTyped(*thingp, [trc, &ret](auto thing) { + CheckTracedThing(trc, thing); + + auto* post = DispatchToOnEdge(trc, thing); + if (!post) { + ret = false; + return TaggedPtr<T>::empty(); + } + + return TaggedPtr<T>::wrap(post); + }); + + // Only update *thingp if the value changed, to avoid TSan false positives for + // template objects when using DumpHeapTracer or UbiNode tracers while Ion + // compiling off-thread. + if (thing.isSome() && thing.value() != *thingp) { + *thingp = thing.value(); + } + + return ret; +} +template bool DoCallback<JS::Value>(GenericTracer*, JS::Value*, const char*); +template bool DoCallback<JS::PropertyKey>(GenericTracer*, JS::PropertyKey*, + const char*); +template bool DoCallback<TaggedProto>(GenericTracer*, TaggedProto*, + const char*); + +void JS::TracingContext::getEdgeName(char* buffer, size_t bufferSize) { + MOZ_ASSERT(bufferSize > 0); + if (functor_) { + (*functor_)(this, buffer, bufferSize); + return; + } + if (index_ != InvalidIndex) { + snprintf(buffer, bufferSize, "%s[%zu]", name_, index_); + return; + } + snprintf(buffer, bufferSize, "%s", name_); +} + +/*** Public Tracing API *****************************************************/ + +JS_PUBLIC_API void JS::TraceChildren(JSTracer* trc, GCCellPtr thing) { + ApplyGCThingTyped(thing.asCell(), thing.kind(), [trc](auto t) { + MOZ_ASSERT_IF(t->runtimeFromAnyThread() != trc->runtime(), + t->isPermanentAndMayBeShared() || + t->zoneFromAnyThread()->isSelfHostingZone()); + t->traceChildren(trc); + }); +} + +void js::gc::TraceIncomingCCWs(JSTracer* trc, + const JS::CompartmentSet& compartments) { + for (CompartmentsIter source(trc->runtime()); !source.done(); source.next()) { + if (compartments.has(source)) { + continue; + } + // Iterate over all compartments that |source| has wrappers for. + for (Compartment::WrappedObjectCompartmentEnum dest(source); !dest.empty(); + dest.popFront()) { + if (!compartments.has(dest)) { + continue; + } + // Iterate over all wrappers from |source| to |dest| compartments. + for (Compartment::ObjectWrapperEnum e(source, dest); !e.empty(); + e.popFront()) { + JSObject* obj = e.front().key(); + MOZ_ASSERT(compartments.has(obj->compartment())); + mozilla::DebugOnly<JSObject*> prior = obj; + TraceManuallyBarrieredEdge(trc, &obj, + "cross-compartment wrapper target"); + MOZ_ASSERT(obj == prior); + } + } + } +} + +/*** Cycle Collector Helpers ************************************************/ + +// This function is used by the Cycle Collector (CC) to trace through -- or in +// CC parlance, traverse -- a Shape tree. The CC does not care about Shapes or +// BaseShapes, only the JSObjects held live by them. Thus, we walk the Shape +// lineage, but only report non-Shape things. This effectively makes the entire +// shape lineage into a single node in the CC, saving tremendous amounts of +// space and time in its algorithms. +// +// The algorithm implemented here uses only bounded stack space. This would be +// possible to implement outside the engine, but would require much extra +// infrastructure and many, many more slow GOT lookups. We have implemented it +// inside SpiderMonkey, despite the lack of general applicability, for the +// simplicity and performance of FireFox's embedding of this engine. +void gc::TraceCycleCollectorChildren(JS::CallbackTracer* trc, Shape* shape) { + do { + MOZ_ASSERT(shape->base()); + shape->base()->assertConsistency(); + + // Don't trace the propid because the CC doesn't care about jsid. + + if (shape->hasGetterObject()) { + JSObject* tmp = shape->getterObject(); + DoCallback(trc, &tmp, "getter"); + MOZ_ASSERT(tmp == shape->getterObject()); + } + + if (shape->hasSetterObject()) { + JSObject* tmp = shape->setterObject(); + DoCallback(trc, &tmp, "setter"); + MOZ_ASSERT(tmp == shape->setterObject()); + } + + shape = shape->previous(); + } while (shape); +} + +void gc::TraceCycleCollectorChildren(JS::CallbackTracer* trc, + ObjectGroup* group) { + MOZ_ASSERT(trc->isCallbackTracer()); + + group->traceChildren(trc); +} + +/*** Traced Edge Printer ****************************************************/ + +static size_t CountDecimalDigits(size_t num) { + size_t numDigits = 0; + do { + num /= 10; + numDigits++; + } while (num > 0); + + return numDigits; +} + +static const char* StringKindHeader(JSString* str) { + MOZ_ASSERT(str->isLinear()); + + if (str->isAtom()) { + if (str->isPermanentAtom()) { + return "permanent atom: "; + } + return "atom: "; + } + + if (str->isExtensible()) { + return "extensible: "; + } + + if (str->isInline()) { + if (str->isFatInline()) { + return "fat inline: "; + } + return "inline: "; + } + + if (str->isDependent()) { + return "dependent: "; + } + + if (str->isExternal()) { + return "external: "; + } + + return "linear: "; +} + +void js::gc::GetTraceThingInfo(char* buf, size_t bufsize, void* thing, + JS::TraceKind kind, bool details) { + const char* name = nullptr; /* silence uninitialized warning */ + size_t n; + + if (bufsize == 0) { + return; + } + + switch (kind) { + case JS::TraceKind::BaseShape: + name = "base_shape"; + break; + + case JS::TraceKind::JitCode: + name = "jitcode"; + break; + + case JS::TraceKind::Null: + name = "null_pointer"; + break; + + case JS::TraceKind::Object: { + name = static_cast<JSObject*>(thing)->getClass()->name; + break; + } + + case JS::TraceKind::ObjectGroup: + name = "object_group"; + break; + + case JS::TraceKind::RegExpShared: + name = "reg_exp_shared"; + break; + + case JS::TraceKind::Scope: + name = "scope"; + break; + + case JS::TraceKind::Script: + name = "script"; + break; + + case JS::TraceKind::Shape: + name = "shape"; + break; + + case JS::TraceKind::String: + name = ((JSString*)thing)->isDependent() ? "substring" : "string"; + break; + + case JS::TraceKind::Symbol: + name = "symbol"; + break; + + case JS::TraceKind::BigInt: + name = "BigInt"; + break; + + default: + name = "INVALID"; + break; + } + + n = strlen(name); + if (n > bufsize - 1) { + n = bufsize - 1; + } + js_memcpy(buf, name, n + 1); + buf += n; + bufsize -= n; + *buf = '\0'; + + if (details && bufsize > 2) { + switch (kind) { + case JS::TraceKind::Object: { + JSObject* obj = (JSObject*)thing; + if (obj->is<JSFunction>()) { + JSFunction* fun = &obj->as<JSFunction>(); + if (fun->displayAtom()) { + *buf++ = ' '; + bufsize--; + PutEscapedString(buf, bufsize, fun->displayAtom(), 0); + } + } else if (obj->getClass()->flags & JSCLASS_HAS_PRIVATE) { + snprintf(buf, bufsize, " %p", obj->as<NativeObject>().getPrivate()); + } else { + snprintf(buf, bufsize, " <no private>"); + } + break; + } + + case JS::TraceKind::Script: { + auto* script = static_cast<js::BaseScript*>(thing); + snprintf(buf, bufsize, " %s:%u", script->filename(), script->lineno()); + break; + } + + case JS::TraceKind::String: { + *buf++ = ' '; + bufsize--; + JSString* str = (JSString*)thing; + + if (str->isLinear()) { + const char* header = StringKindHeader(str); + bool willFit = str->length() + strlen("<length > ") + strlen(header) + + CountDecimalDigits(str->length()) < + bufsize; + + n = snprintf(buf, bufsize, "<%slength %zu%s> ", header, str->length(), + willFit ? "" : " (truncated)"); + buf += n; + bufsize -= n; + + PutEscapedString(buf, bufsize, &str->asLinear(), 0); + } else { + snprintf(buf, bufsize, "<rope: length %zu>", str->length()); + } + break; + } + + case JS::TraceKind::Symbol: { + auto* sym = static_cast<JS::Symbol*>(thing); + if (JSAtom* desc = sym->description()) { + *buf++ = ' '; + bufsize--; + PutEscapedString(buf, bufsize, desc, 0); + } else { + snprintf(buf, bufsize, "<null>"); + } + break; + } + + case JS::TraceKind::Scope: { + auto* scope = static_cast<js::Scope*>(thing); + snprintf(buf, bufsize, " %s", js::ScopeKindString(scope->kind())); + break; + } + + default: + break; + } + } + buf[bufsize - 1] = '\0'; +} + +JS::CallbackTracer::CallbackTracer(JSContext* cx, JS::TracerKind kind, + JS::TraceOptions options) + : CallbackTracer(cx->runtime(), kind, options) {} + +uint32_t JSTracer::gcNumberForMarking() const { + MOZ_ASSERT(isMarkingTracer()); + return runtime()->gc.gcNumber(); +} |