Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 565 insertions, 0 deletions

diff --git a/js/src/vm/Activation.h b/js/src/vm/Activation.h
new file mode 100644
index 0000000000..4153e27478
--- /dev/null
+++ b/js/src/vm/Activation.h
@@ -0,0 +1,565 @@
+/* -*- 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/. */
+
+#ifndef vm_Activation_h
+#define vm_Activation_h
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT
+#include "mozilla/Attributes.h"  // MOZ_RAII
+
+#include <stddef.h>  // size_t
+#include <stdint.h>  // uint8_t, uint32_t
+
+#include "jstypes.h"  // JS_PUBLIC_API
+
+#include "jit/CalleeToken.h"  // js::jit::CalleeToken
+#include "js/RootingAPI.h"    // JS::Handle, JS::Rooted
+#include "js/TypeDecls.h"     // jsbytecode
+#include "js/Value.h"         // JS::Value
+#include "vm/SavedFrame.h"    // js::SavedFrame
+#include "vm/Stack.h"         // js::InterpreterRegs
+
+struct JS_PUBLIC_API JSContext;
+
+class JSFunction;
+class JSObject;
+class JSScript;
+
+namespace JS {
+
+class CallArgs;
+class JS_PUBLIC_API Compartment;
+
+namespace dbg {
+class JS_PUBLIC_API AutoEntryMonitor;
+}  // namespace dbg
+
+}  // namespace JS
+
+namespace js {
+
+class InterpreterActivation;
+
+namespace jit {
+class JitActivation;
+}  // namespace jit
+
+// This class is separate from Activation, because it calls Compartment::wrap()
+// which can GC and walk the stack. It's not safe to do that within the
+// JitActivation constructor.
+class MOZ_RAII ActivationEntryMonitor {
+  JSContext* cx_;
+
+  // The entry point monitor that was set on cx_->runtime() when this
+  // ActivationEntryMonitor was created.
+  JS::dbg::AutoEntryMonitor* entryMonitor_;
+
+  explicit inline ActivationEntryMonitor(JSContext* cx);
+
+  ActivationEntryMonitor(const ActivationEntryMonitor& other) = delete;
+  void operator=(const ActivationEntryMonitor& other) = delete;
+
+  void init(JSContext* cx, jit::CalleeToken entryToken);
+  void init(JSContext* cx, InterpreterFrame* entryFrame);
+
+  JS::Value asyncStack(JSContext* cx);
+
+ public:
+  inline ActivationEntryMonitor(JSContext* cx, InterpreterFrame* entryFrame);
+  inline ActivationEntryMonitor(JSContext* cx, jit::CalleeToken entryToken);
+  inline ~ActivationEntryMonitor();
+};
+
+// [SMDOC] LiveSavedFrameCache: SavedFrame caching to minimize stack walking
+//
+// Since each SavedFrame object includes a 'parent' pointer to the SavedFrame
+// for its caller, if we could easily find the right SavedFrame for a given
+// stack frame, we wouldn't need to walk the rest of the stack. Traversing deep
+// stacks can be expensive, and when we're profiling or instrumenting code, we
+// may want to capture JavaScript stacks frequently, so such cases would benefit
+// if we could avoid walking the entire stack.
+//
+// We could have a cache mapping frame addresses to their SavedFrame objects,
+// but invalidating its entries would be a challenge. Popping a stack frame is
+// extremely performance-sensitive, and SpiderMonkey stack frames can be OSR'd,
+// thrown, rematerialized, and perhaps meet other fates; we would rather our
+// cache not depend on handling so many tricky cases.
+//
+// It turns out that we can keep the cache accurate by reserving a single bit in
+// the stack frame, which must be clear on any newly pushed frame. When we
+// insert an entry into the cache mapping a given frame address to its
+// SavedFrame, we set the bit in the frame. Then, we take care to probe the
+// cache only for frames whose bit is set; the bit tells us that the frame has
+// never left the stack, so its cache entry must be accurate, at least about
+// which function the frame is executing (the line may have changed; more about
+// that below). The code refers to this bit as the 'hasCachedSavedFrame' flag.
+//
+// We could manage such a cache replacing least-recently used entries, but we
+// can do better than that: the cache can be a stack, of which we need examine
+// only entries from the top.
+//
+// First, observe that stacks are walked from the youngest frame to the oldest,
+// but SavedFrame chains are built from oldest to youngest, to ensure common
+// tails are shared. This means that capturing a stack is necessarily a
+// two-phase process: walk the stack, and then build the SavedFrames.
+//
+// Naturally, the first time we capture the stack, the cache is empty, and we
+// must traverse the entire stack. As we build each SavedFrame, we push an entry
+// associating the frame's address to its SavedFrame on the cache, and set the
+// frame's bit. At the end, every frame has its bit set and an entry in the
+// cache.
+//
+// Then the program runs some more. Some, none, or all of the frames are popped.
+// Any new frames are pushed with their bit clear. Any frame with its bit set
+// has never left the stack. The cache is left untouched.
+//
+// For the next capture, we walk the stack up to the first frame with its bit
+// set, if there is one. Call it F; it must have a cache entry. We pop entries
+// from the cache - all invalid, because they are above F's entry, and hence
+// younger - until we find the entry matching F's address. Since F's bit is set,
+// we know it never left the stack, and hence that no younger frame could have
+// had a colliding address. And since the frame's bit was set when we pushed the
+// cache entry, we know the entry is still valid.
+//
+// F's cache entry's SavedFrame covers the rest of the stack, so we don't need
+// to walk the stack any further. Now we begin building SavedFrame objects for
+// the new frames, pushing cache entries, and setting bits on the frames. By the
+// end, the cache again covers the full stack, and every frame's bit is set.
+//
+// If we walk the stack to the end, and find no frame with its bit set, then the
+// entire cache is invalid. At this point, it must be emptied, so that the new
+// entries we are about to push are the only frames in the cache.
+//
+// For example, suppose we have the following stack (let 'A > B' mean "A called
+// B", so the frames are listed oldest first):
+//
+//     P  > Q  > R  > S          Initial stack, bits not set.
+//     P* > Q* > R* > S*         Capture a SavedFrame stack, set bits.
+//                               The cache now holds: P > Q > R > S.
+//     P* > Q* > R*              Return from S.
+//     P* > Q*                   Return from R.
+//     P* > Q* > T  > U          Call T and U. New frames have clear bits.
+//
+// If we capture the stack now, the cache still holds:
+//
+//     P  > Q  > R  > S
+//
+// As we traverse the stack, we'll cross U and T, and then find Q with its bit
+// set. We pop entries from the cache until we find the entry for Q; this
+// removes entries R and S, which were indeed invalid. In Q's cache entry, we
+// find the SavedFrame representing the stack P > Q. Now we build SavedFrames
+// for the new portion of the stack, pushing an entry for T and setting the bit
+// on the frame, and then doing the same for U. In the end, the call stack again
+// has bits set on all its frames:
+//
+//     P* > Q* > T* > U*         All frames are now in the cache.
+//
+// And the cache again holds entries for the entire stack:
+//
+//     P  > Q  > T  > U
+//
+// Details:
+//
+// - When we find a cache entry whose frame address matches our frame F, we know
+//   that F has never left the stack, but it may certainly be the case that
+//   execution took place in that frame, and that the current source position
+//   within F's function has changed. This means that the entry's SavedFrame,
+//   which records the source line and column as well as the function, is not
+//   correct. To detect this case, when we push a cache entry, we record the
+//   frame's pc. When consulting the cache, if a frame's address matches but its
+//   pc does not, then we pop the cache entry, clear the frame's bit, and
+//   continue walking the stack. The next stack frame will definitely hit: since
+//   its callee frame never left the stack, the calling frame never got the
+//   chance to execute.
+//
+// - Generators, at least conceptually, have long-lived stack frames that
+//   disappear from the stack when the generator yields, and reappear on the
+//   stack when the generator's 'next' method is called. When a generator's
+//   frame is placed again atop the stack, its bit must be cleared - for the
+//   purposes of the cache, treating the frame as a new frame - to respect the
+//   invariants we used to justify the algorithm above. Async function
+//   activations usually appear atop empty stacks, since they are invoked as a
+//   promise callback, but the same rule applies.
+//
+// - SpiderMonkey has many types of stack frames, and not all have a place to
+//   store a bit indicating a cached SavedFrame. But as long as we don't create
+//   cache entries for frames we can't mark, simply omitting them from the cache
+//   is harmless. Uncacheable frame types include inlined Ion frames and
+//   non-Debug wasm frames. The LiveSavedFrameCache::FramePtr type represents
+//   only pointers to frames that can be cached, so if you have a FramePtr, you
+//   don't need to further check the frame for cachability. FramePtr provides
+//   access to the hasCachedSavedFrame bit.
+//
+// - We actually break up the cache into one cache per Activation. Popping an
+//   activation invalidates all its cache entries, simply by freeing the cache
+//   altogether.
+//
+// - The entire chain of SavedFrames for a given stack capture is created in the
+//   compartment of the code that requested the capture, *not* in that of the
+//   frames it represents, so in general, different compartments may have
+//   different SavedFrame objects representing the same actual stack frame. The
+//   LiveSavedFrameCache simply records whichever SavedFrames were used in the
+//   most recent captures. When we find a cache hit, we check the entry's
+//   SavedFrame's compartment against the current compartment; if they do not
+//   match, we clear the entire cache.
+//
+//   This means that it is not always true that, if a frame's
+//   hasCachedSavedFrame bit is set, it must have an entry in the cache. The
+//   actual invariant is: either the cache is completely empty, or the frames'
+//   bits are trustworthy. This invariant holds even though capture can be
+//   interrupted at many places by OOM failures. Clearing the cache is a single,
+//   uninterruptible step. When we try to look up a frame whose bit is set and
+//   find an empty cache, we clear the frame's bit. And we only add the first
+//   frame to an empty cache once we've walked the stack all the way, so we know
+//   that all frames' bits are cleared by that point.
+//
+// - When the Debugger API evaluates an expression in some frame (the 'target
+//   frame'), it's SpiderMonkey's convention that the target frame be treated as
+//   the parent of the eval frame. In reality, of course, the eval frame is
+//   pushed on the top of the stack like any other frame, but stack captures
+//   simply jump straight over the intervening frames, so that the '.parent'
+//   property of a SavedFrame for the eval is the SavedFrame for the target.
+//   This is arranged by giving the eval frame an 'evalInFramePrev` link
+//   pointing to the target, which an ordinary FrameIter will notice and
+//   respect.
+//
+//   If the LiveSavedFrameCache were presented with stack traversals that
+//   skipped frames in this way, it would cause havoc. First, with no debugger
+//   eval frames present, capture the stack, populating the cache. Then push a
+//   debugger eval frame and capture again; the skipped frames to appear to be
+//   absent from the stack. Now pop the debugger eval frame, and capture a third
+//   time: the no-longer-skipped frames seem to reappear on the stack, with
+//   their cached bits still set.
+//
+//   The LiveSavedFrameCache assumes that the stack it sees is used in a
+//   stack-like fashion: if a frame has its bit set, it has never left the
+//   stack. To support this assumption, when the cache is in use, we do not skip
+//   the frames between a debugger eval frame an its target; we always traverse
+//   the entire stack, invalidating and populating the cache in the usual way.
+//   Instead, when we construct a SavedFrame for a debugger eval frame, we
+//   select the appropriate parent at that point: rather than the next-older
+//   frame, we find the SavedFrame for the eval's target frame. The skip appears
+//   in the SavedFrame chains, even as the traversal covers all the frames.
+//
+// - Rematerialized frames (see ../jit/RematerializedFrame.h) are always created
+//   with their hasCachedSavedFrame bits clear: although there may be extant
+//   SavedFrames built from the original IonMonkey frame, the Rematerialized
+//   frames will not have cache entries for them until they are traversed in a
+//   capture themselves.
+//
+//   This means that, oddly, it is not always true that, once we reach a frame
+//   with its hasCachedSavedFrame bit set, all its parents will have the bit set
+//   as well. However, clear bits under younger set bits will only occur on
+//   Rematerialized frames.
+class LiveSavedFrameCache {
+ public:
+  // The address of a live frame for which we can cache SavedFrames: it has a
+  // 'hasCachedSavedFrame' bit we can examine and set, and can be converted to
+  // a Key to index the cache.
+  class FramePtr {
+    // We use jit::CommonFrameLayout for both Baseline frames and Ion
+    // physical frames.
+    using Ptr = mozilla::Variant<InterpreterFrame*, jit::CommonFrameLayout*,
+                                 jit::RematerializedFrame*, wasm::DebugFrame*>;
+
+    Ptr ptr;
+
+    template <typename Frame>
+    explicit FramePtr(Frame ptr) : ptr(ptr) {}
+
+    struct HasCachedMatcher;
+    struct SetHasCachedMatcher;
+    struct ClearHasCachedMatcher;
+
+   public:
+    // If iter's frame is of a type that can be cached, construct a FramePtr
+    // for its frame. Otherwise, return Nothing.
+    static inline mozilla::Maybe<FramePtr> create(const FrameIter& iter);
+
+    inline bool hasCachedSavedFrame() const;
+    inline void setHasCachedSavedFrame();
+    inline void clearHasCachedSavedFrame();
+
+    // Return true if this FramePtr refers to an interpreter frame.
+    inline bool isInterpreterFrame() const {
+      return ptr.is<InterpreterFrame*>();
+    }
+
+    // If this FramePtr is an interpreter frame, return a pointer to it.
+    inline InterpreterFrame& asInterpreterFrame() const {
+      return *ptr.as<InterpreterFrame*>();
+    }
+
+    // Return true if this FramePtr refers to a rematerialized frame.
+    inline bool isRematerializedFrame() const {
+      return ptr.is<jit::RematerializedFrame*>();
+    }
+
+    bool operator==(const FramePtr& rhs) const { return rhs.ptr == this->ptr; }
+    bool operator!=(const FramePtr& rhs) const { return !(rhs == *this); }
+  };
+
+ private:
+  // A key in the cache: the address of a frame, live or dead, for which we
+  // can cache SavedFrames. Since the pointer may not be live, the only
+  // operation this type permits is comparison.
+  class Key {
+    FramePtr framePtr;
+
+   public:
+    MOZ_IMPLICIT Key(const FramePtr& framePtr) : framePtr(framePtr) {}
+
+    bool operator==(const Key& rhs) const {
+      return rhs.framePtr == this->framePtr;
+    }
+    bool operator!=(const Key& rhs) const { return !(rhs == *this); }
+  };
+
+  struct Entry {
+    const Key key;
+    const jsbytecode* pc;
+    HeapPtr<SavedFrame*> savedFrame;
+
+    Entry(const Key& key, const jsbytecode* pc, SavedFrame* savedFrame)
+        : key(key), pc(pc), savedFrame(savedFrame) {}
+  };
+
+  using EntryVector = Vector<Entry, 0, SystemAllocPolicy>;
+  EntryVector* frames;
+
+  LiveSavedFrameCache(const LiveSavedFrameCache&) = delete;
+  LiveSavedFrameCache& operator=(const LiveSavedFrameCache&) = delete;
+
+ public:
+  explicit LiveSavedFrameCache() : frames(nullptr) {}
+
+  LiveSavedFrameCache(LiveSavedFrameCache&& rhs) : frames(rhs.frames) {
+    MOZ_ASSERT(this != &rhs, "self-move disallowed");
+    rhs.frames = nullptr;
+  }
+
+  ~LiveSavedFrameCache() {
+    if (frames) {
+      js_delete(frames);
+      frames = nullptr;
+    }
+  }
+
+  bool initialized() const { return !!frames; }
+  bool init(JSContext* cx) {
+    frames = js_new<EntryVector>();
+    if (!frames) {
+      JS_ReportOutOfMemory(cx);
+      return false;
+    }
+    return true;
+  }
+
+  void trace(JSTracer* trc);
+
+  // Set |frame| to the cached SavedFrame corresponding to |framePtr| at |pc|.
+  // |framePtr|'s hasCachedSavedFrame bit must be set. Remove all cache
+  // entries for frames younger than that one.
+  //
+  // This may set |frame| to nullptr if |pc| is different from the pc supplied
+  // when the cache entry was inserted. In this case, the cached SavedFrame
+  // (probably) has the wrong source position. Entries for younger frames are
+  // still removed. The next frame, if any, will be a cache hit.
+  //
+  // This may also set |frame| to nullptr if the cache was populated with
+  // SavedFrame objects for a different compartment than cx's current
+  // compartment. In this case, the entire cache is flushed.
+  void find(JSContext* cx, FramePtr& framePtr, const jsbytecode* pc,
+            MutableHandle<SavedFrame*> frame) const;
+
+  // Search the cache for a frame matching |framePtr|, without removing any
+  // entries. Return the matching saved frame, or nullptr if none is found.
+  // This is used for resolving |evalInFramePrev| links.
+  void findWithoutInvalidation(const FramePtr& framePtr,
+                               MutableHandle<SavedFrame*> frame) const;
+
+  // Push a cache entry mapping |framePtr| and |pc| to |savedFrame| on the top
+  // of the cache's stack. You must insert entries for frames from oldest to
+  // youngest. They must all be younger than the frame that the |find| method
+  // found a hit for; or you must have cleared the entire cache with the
+  // |clear| method.
+  bool insert(JSContext* cx, FramePtr&& framePtr, const jsbytecode* pc,
+              Handle<SavedFrame*> savedFrame);
+
+  // Remove all entries from the cache.
+  void clear() {
+    if (frames) frames->clear();
+  }
+};
+
+static_assert(
+    sizeof(LiveSavedFrameCache) == sizeof(uintptr_t),
+    "Every js::Activation has a LiveSavedFrameCache, so we need to be pretty "
+    "careful "
+    "about avoiding bloat. If you're adding members to LiveSavedFrameCache, "
+    "maybe you "
+    "should consider figuring out a way to make js::Activation have a "
+    "LiveSavedFrameCache* instead of a Rooted<LiveSavedFrameCache>.");
+
+class Activation {
+ protected:
+  JSContext* cx_;
+  JS::Compartment* compartment_;
+  Activation* prev_;
+  Activation* prevProfiling_;
+
+  // Counter incremented by JS::HideScriptedCaller and decremented by
+  // JS::UnhideScriptedCaller. If > 0 for the top activation,
+  // DescribeScriptedCaller will return null instead of querying that
+  // activation, which should prompt the caller to consult embedding-specific
+  // data structures instead.
+  size_t hideScriptedCallerCount_;
+
+  // The cache of SavedFrame objects we have already captured when walking
+  // this activation's stack.
+  JS::Rooted<LiveSavedFrameCache> frameCache_;
+
+  // Youngest saved frame of an async stack that will be iterated during stack
+  // capture in place of the actual stack of previous activations. Note that
+  // the stack of this activation is captured entirely before this is used.
+  //
+  // Usually this is nullptr, meaning that normal stack capture will occur.
+  // When this is set, the stack of any previous activation is ignored.
+  JS::Rooted<SavedFrame*> asyncStack_;
+
+  // Value of asyncCause to be attached to asyncStack_.
+  const char* asyncCause_;
+
+  // True if the async call was explicitly requested, e.g. via
+  // callFunctionWithAsyncStack.
+  bool asyncCallIsExplicit_;
+
+  enum Kind { Interpreter, Jit };
+  Kind kind_;
+
+  inline Activation(JSContext* cx, Kind kind);
+  inline ~Activation();
+
+ public:
+  JSContext* cx() const { return cx_; }
+  JS::Compartment* compartment() const { return compartment_; }
+  Activation* prev() const { return prev_; }
+  Activation* prevProfiling() const { return prevProfiling_; }
+  inline Activation* mostRecentProfiling();
+
+  bool isInterpreter() const { return kind_ == Interpreter; }
+  bool isJit() const { return kind_ == Jit; }
+  inline bool hasWasmExitFP() const;
+
+  inline bool isProfiling() const;
+  void registerProfiling();
+  void unregisterProfiling();
+
+  InterpreterActivation* asInterpreter() const {
+    MOZ_ASSERT(isInterpreter());
+    return (InterpreterActivation*)this;
+  }
+  jit::JitActivation* asJit() const {
+    MOZ_ASSERT(isJit());
+    return (jit::JitActivation*)this;
+  }
+
+  void hideScriptedCaller() { hideScriptedCallerCount_++; }
+  void unhideScriptedCaller() {
+    MOZ_ASSERT(hideScriptedCallerCount_ > 0);
+    hideScriptedCallerCount_--;
+  }
+  bool scriptedCallerIsHidden() const { return hideScriptedCallerCount_ > 0; }
+
+  SavedFrame* asyncStack() { return asyncStack_; }
+
+  const char* asyncCause() const { return asyncCause_; }
+
+  bool asyncCallIsExplicit() const { return asyncCallIsExplicit_; }
+
+  inline LiveSavedFrameCache* getLiveSavedFrameCache(JSContext* cx);
+  void clearLiveSavedFrameCache() { frameCache_.get().clear(); }
+
+ private:
+  Activation(const Activation& other) = delete;
+  void operator=(const Activation& other) = delete;
+};
+
+// This variable holds a special opcode value which is greater than all normal
+// opcodes, and is chosen such that the bitwise or of this value with any
+// opcode is this value.
+constexpr jsbytecode EnableInterruptsPseudoOpcode = -1;
+
+static_assert(EnableInterruptsPseudoOpcode >= JSOP_LIMIT,
+              "EnableInterruptsPseudoOpcode must be greater than any opcode");
+static_assert(
+    EnableInterruptsPseudoOpcode == jsbytecode(-1),
+    "EnableInterruptsPseudoOpcode must be the maximum jsbytecode value");
+
+class InterpreterFrameIterator;
+class RunState;
+
+class InterpreterActivation : public Activation {
+  friend class js::InterpreterFrameIterator;
+
+  InterpreterRegs regs_;
+  InterpreterFrame* entryFrame_;
+  size_t opMask_;  // For debugger interrupts, see js::Interpret.
+
+#ifdef DEBUG
+  size_t oldFrameCount_;
+#endif
+
+ public:
+  inline InterpreterActivation(RunState& state, JSContext* cx,
+                               InterpreterFrame* entryFrame);
+  inline ~InterpreterActivation();
+
+  inline bool pushInlineFrame(const JS::CallArgs& args,
+                              JS::Handle<JSScript*> script,
+                              MaybeConstruct constructing);
+  inline void popInlineFrame(InterpreterFrame* frame);
+
+  inline bool resumeGeneratorFrame(JS::Handle<JSFunction*> callee,
+                                   JS::Handle<JSObject*> envChain);
+
+  InterpreterFrame* current() const { return regs_.fp(); }
+  InterpreterRegs& regs() { return regs_; }
+  InterpreterFrame* entryFrame() const { return entryFrame_; }
+  size_t opMask() const { return opMask_; }
+
+  bool isProfiling() const { return false; }
+
+  // If this js::Interpret frame is running |script|, enable interrupts.
+  void enableInterruptsIfRunning(JSScript* script) {
+    if (regs_.fp()->script() == script) {
+      enableInterruptsUnconditionally();
+    }
+  }
+  void enableInterruptsUnconditionally() {
+    opMask_ = EnableInterruptsPseudoOpcode;
+  }
+  void clearInterruptsMask() { opMask_ = 0; }
+};
+
+// Iterates over a thread's activation list.
+class ActivationIterator {
+ protected:
+  Activation* activation_;
+
+ public:
+  explicit ActivationIterator(JSContext* cx);
+
+  ActivationIterator& operator++();
+
+  Activation* operator->() const { return activation_; }
+  Activation* activation() const { return activation_; }
+  bool done() const { return activation_ == nullptr; }
+};
+
+}  // namespace js
+
+#endif  // vm_Activation_h