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Diffstat (limited to 'js/public/Debug.h')
| -rw-r--r-- | js/public/Debug.h | 354 |
1 files changed, 354 insertions, 0 deletions
diff --git a/js/public/Debug.h b/js/public/Debug.h new file mode 100644 index 0000000000..6d7fd8a4be --- /dev/null +++ b/js/public/Debug.h @@ -0,0 +1,354 @@ +/* -*- 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/. */ + +// Interfaces by which the embedding can interact with the Debugger API. + +#ifndef js_Debug_h +#define js_Debug_h + +#include "mozilla/Assertions.h" +#include "mozilla/Attributes.h" +#include "mozilla/MemoryReporting.h" + +#include <utility> + +#include "jstypes.h" + +#include "js/GCAPI.h" +#include "js/RootingAPI.h" +#include "js/TypeDecls.h" + +namespace js { +class Debugger; +} // namespace js + +/* Defined in vm/Debugger.cpp. */ +extern JS_PUBLIC_API bool JS_DefineDebuggerObject(JSContext* cx, + JS::HandleObject obj); + +namespace JS { +namespace dbg { + +// [SMDOC] Debugger builder API +// +// Helping embedding code build objects for Debugger +// ------------------------------------------------- +// +// Some Debugger API features lean on the embedding application to construct +// their result values. For example, Debugger.Frame.prototype.scriptEntryReason +// calls hooks provided by the embedding to construct values explaining why it +// invoked JavaScript; if F is a frame called from a mouse click event handler, +// F.scriptEntryReason would return an object of the form: +// +// { eventType: "mousedown", event: <object> } +// +// where <object> is a Debugger.Object whose referent is the event being +// dispatched. +// +// However, Debugger implements a trust boundary. Debuggee code may be +// considered untrusted; debugger code needs to be protected from debuggee +// getters, setters, proxies, Object.watch watchpoints, and any other feature +// that might accidentally cause debugger code to set the debuggee running. The +// Debugger API tries to make it easy to write safe debugger code by only +// offering access to debuggee objects via Debugger.Object instances, which +// ensure that only those operations whose explicit purpose is to invoke +// debuggee code do so. But this protective membrane is only helpful if we +// interpose Debugger.Object instances in all the necessary spots. +// +// SpiderMonkey's compartment system also implements a trust boundary. The +// debuggee and debugger are always in different compartments. Inter-compartment +// work requires carefully tracking which compartment each JSObject or JS::Value +// belongs to, and ensuring that is is correctly wrapped for each operation. +// +// It seems precarious to expect the embedding's hooks to implement these trust +// boundaries. Instead, the JS::dbg::Builder API segregates the code which +// constructs trusted objects from that which deals with untrusted objects. +// Trusted objects have an entirely different C++ type, so code that improperly +// mixes trusted and untrusted objects is caught at compile time. +// +// In the structure shown above, there are two trusted objects, and one +// untrusted object: +// +// - The overall object, with the 'eventType' and 'event' properties, is a +// trusted object. We're going to return it to D.F.p.scriptEntryReason's +// caller, which will handle it directly. +// +// - The Debugger.Object instance appearing as the value of the 'event' property +// is a trusted object. It belongs to the same Debugger instance as the +// Debugger.Frame instance whose scriptEntryReason accessor was called, and +// presents a safe reflection-oriented API for inspecting its referent, which +// is: +// +// - The actual event object, an untrusted object, and the referent of the +// Debugger.Object above. (Content can do things like replacing accessors on +// Event.prototype.) +// +// Using JS::dbg::Builder, all objects and values the embedding deals with +// directly are considered untrusted, and are assumed to be debuggee values. The +// only way to construct trusted objects is to use Builder's own methods, which +// return a separate Object type. The only way to set a property on a trusted +// object is through that Object type. The actual trusted object is never +// exposed to the embedding. +// +// So, for example, the embedding might use code like the following to construct +// the object shown above, given a Builder passed to it by Debugger: +// +// bool +// MyScriptEntryReason::explain(JSContext* cx, +// Builder& builder, +// Builder::Object& result) +// { +// JSObject* eventObject = ... obtain debuggee event object somehow ...; +// if (!eventObject) { +// return false; +// } +// result = builder.newObject(cx); +// return result && +// result.defineProperty(cx, "eventType", +// SafelyFetchType(eventObject)) && +// result.defineProperty(cx, "event", eventObject); +// } +// +// +// Object::defineProperty also accepts an Object as the value to store on the +// property. By its type, we know that the value is trusted, so we set it +// directly as the property's value, without interposing a Debugger.Object +// wrapper. This allows the embedding to builted nested structures of trusted +// objects. +// +// The Builder and Builder::Object methods take care of doing whatever +// compartment switching and wrapping are necessary to construct the trusted +// values in the Debugger's compartment. +// +// The Object type is self-rooting. Construction, assignment, and destruction +// all properly root the referent object. + +class BuilderOrigin; + +class Builder { + // The Debugger instance whose client we are building a value for. We build + // objects in this object's compartment. + PersistentRootedObject debuggerObject; + + // debuggerObject's Debugger structure, for convenience. + js::Debugger* debugger; + + // Check that |thing| is in the same compartment as our debuggerObject. Used + // for assertions when constructing BuiltThings. We can overload this as we + // add more instantiations of BuiltThing. +#ifdef DEBUG + void assertBuilt(JSObject* obj); +#else + void assertBuilt(JSObject* obj) {} +#endif + + protected: + // A reference to a trusted object or value. At the moment, we only use it + // with JSObject*. + template <typename T> + class BuiltThing { + friend class BuilderOrigin; + + protected: + // The Builder to which this trusted thing belongs. + Builder& owner; + + // A rooted reference to our value. + PersistentRooted<T> value; + + BuiltThing(JSContext* cx, Builder& owner_, + T value_ = SafelyInitialized<T>::create()) + : owner(owner_), value(cx, value_) { + owner.assertBuilt(value_); + } + + // Forward some things from our owner, for convenience. + js::Debugger* debugger() const { return owner.debugger; } + JSObject* debuggerObject() const { return owner.debuggerObject; } + + public: + BuiltThing(const BuiltThing& rhs) : owner(rhs.owner), value(rhs.value) {} + BuiltThing& operator=(const BuiltThing& rhs) { + MOZ_ASSERT(&owner == &rhs.owner); + owner.assertBuilt(rhs.value); + value = rhs.value; + return *this; + } + + explicit operator bool() const { + // If we ever instantiate BuiltThing<Value>, this might not suffice. + return value; + } + + private: + BuiltThing() = delete; + }; + + public: + // A reference to a trusted object, possibly null. Instances of Object are + // always properly rooted. They can be copied and assigned, as if they were + // pointers. + class Object : private BuiltThing<JSObject*> { + friend class Builder; // for construction + friend class BuilderOrigin; // for unwrapping + + typedef BuiltThing<JSObject*> Base; + + // This is private, because only Builders can create Objects that + // actually point to something (hence the 'friend' declaration). + Object(JSContext* cx, Builder& owner_, HandleObject obj) + : Base(cx, owner_, obj.get()) {} + + bool definePropertyToTrusted(JSContext* cx, const char* name, + JS::MutableHandleValue value); + + public: + Object(JSContext* cx, Builder& owner_) : Base(cx, owner_, nullptr) {} + Object(const Object& rhs) = default; + + // Our automatically-generated assignment operator can see our base + // class's assignment operator, so we don't need to write one out here. + + // Set the property named |name| on this object to |value|. + // + // If |value| is a string or primitive, re-wrap it for the debugger's + // compartment. + // + // If |value| is an object, assume it is a debuggee object and make a + // Debugger.Object instance referring to it. Set that as the propery's + // value. + // + // If |value| is another trusted object, store it directly as the + // property's value. + // + // On error, report the problem on cx and return false. + bool defineProperty(JSContext* cx, const char* name, JS::HandleValue value); + bool defineProperty(JSContext* cx, const char* name, + JS::HandleObject value); + bool defineProperty(JSContext* cx, const char* name, Object& value); + + using Base::operator bool; + }; + + // Build an empty object for direct use by debugger code, owned by this + // Builder. If an error occurs, report it on cx and return a false Object. + Object newObject(JSContext* cx); + + protected: + Builder(JSContext* cx, js::Debugger* debugger); +}; + +// Debugger itself instantiates this subclass of Builder, which can unwrap +// BuiltThings that belong to it. +class BuilderOrigin : public Builder { + template <typename T> + T unwrapAny(const BuiltThing<T>& thing) { + MOZ_ASSERT(&thing.owner == this); + return thing.value.get(); + } + + public: + BuilderOrigin(JSContext* cx, js::Debugger* debugger_) + : Builder(cx, debugger_) {} + + JSObject* unwrap(Object& object) { return unwrapAny(object); } +}; + +// Finding the size of blocks allocated with malloc +// ------------------------------------------------ +// +// Debugger.Memory wants to be able to report how many bytes items in memory are +// consuming. To do this, it needs a function that accepts a pointer to a block, +// and returns the number of bytes allocated to that block. SpiderMonkey itself +// doesn't know which function is appropriate to use, but the embedding does. + +// Tell Debuggers in |cx| to use |mallocSizeOf| to find the size of +// malloc'd blocks. +JS_PUBLIC_API void SetDebuggerMallocSizeOf(JSContext* cx, + mozilla::MallocSizeOf mallocSizeOf); + +// Get the MallocSizeOf function that the given context is using to find the +// size of malloc'd blocks. +JS_PUBLIC_API mozilla::MallocSizeOf GetDebuggerMallocSizeOf(JSContext* cx); + +// Debugger and Garbage Collection Events +// -------------------------------------- +// +// The Debugger wants to report about its debuggees' GC cycles, however entering +// JS after a GC is troublesome since SpiderMonkey will often do something like +// force a GC and then rely on the nursery being empty. If we call into some +// Debugger's hook after the GC, then JS runs and the nursery won't be +// empty. Instead, we rely on embedders to call back into SpiderMonkey after a +// GC and notify Debuggers to call their onGarbageCollection hook. + +// Determine whether it's necessary to call FireOnGarbageCollectionHook() after +// a GC. This is only required if there are debuggers with an +// onGarbageCollection hook observing a global in the set of collected zones. +JS_PUBLIC_API bool FireOnGarbageCollectionHookRequired(JSContext* cx); + +// For each Debugger that observed a debuggee involved in the given GC event, +// call its `onGarbageCollection` hook. +JS_PUBLIC_API bool FireOnGarbageCollectionHook( + JSContext* cx, GarbageCollectionEvent::Ptr&& data); + +// Return true if the given value is a Debugger object, false otherwise. +JS_PUBLIC_API bool IsDebugger(JSObject& obj); + +// Append each of the debuggee global objects observed by the Debugger object +// |dbgObj| to |vector|. Returns true on success, false on failure. +JS_PUBLIC_API bool GetDebuggeeGlobals(JSContext* cx, JSObject& dbgObj, + MutableHandleObjectVector vector); + +// Hooks for reporting where JavaScript execution began. +// +// Our performance tools would like to be able to label blocks of JavaScript +// execution with the function name and source location where execution began: +// the event handler, the callback, etc. +// +// Construct an instance of this class on the stack, providing a JSContext +// belonging to the runtime in which execution will occur. Each time we enter +// JavaScript --- specifically, each time we push a JavaScript stack frame that +// has no older JS frames younger than this AutoEntryMonitor --- we will +// call the appropriate |Entry| member function to indicate where we've begun +// execution. + +class MOZ_STACK_CLASS JS_PUBLIC_API AutoEntryMonitor { + JSContext* cx_; + AutoEntryMonitor* savedMonitor_; + + public: + explicit AutoEntryMonitor(JSContext* cx); + ~AutoEntryMonitor(); + + // SpiderMonkey reports the JavaScript entry points occuring within this + // AutoEntryMonitor's scope to the following member functions, which the + // embedding is expected to override. + // + // It is important to note that |asyncCause| is owned by the caller and its + // lifetime must outlive the lifetime of the AutoEntryMonitor object. It is + // strongly encouraged that |asyncCause| be a string constant or similar + // statically allocated string. + + // We have begun executing |function|. Note that |function| may not be the + // actual closure we are running, but only the canonical function object to + // which the script refers. + virtual void Entry(JSContext* cx, JSFunction* function, + HandleValue asyncStack, const char* asyncCause) = 0; + + // Execution has begun at the entry point of |script|, which is not a + // function body. (This is probably being executed by 'eval' or some + // JSAPI equivalent.) + virtual void Entry(JSContext* cx, JSScript* script, HandleValue asyncStack, + const char* asyncCause) = 0; + + // Execution of the function or script has ended. + virtual void Exit(JSContext* cx) {} +}; + +} // namespace dbg +} // namespace JS + +#endif /* js_Debug_h */ |