sdk/runtime/vm/stack_frame.cc

// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/stack_frame.h"

#include "platform/memory_sanitizer.h"
#include "vm/assembler.h"
#include "vm/deopt_instructions.h"
#include "vm/isolate.h"
#include "vm/object.h"
#include "vm/object_store.h"
#include "vm/os.h"
#include "vm/parser.h"
#include "vm/raw_object.h"
#include "vm/reusable_handles.h"
#include "vm/stub_code.h"
#include "vm/visitor.h"

namespace dart {


bool StackFrame::IsStubFrame() const {
  ASSERT(!(IsEntryFrame() || IsExitFrame()));
#if !defined(TARGET_OS_WINDOWS)
  // On Windows, the profiler calls this from a separate thread where
  // Thread::Current() is NULL, so we cannot create a NoSafepointScope.
  NoSafepointScope no_safepoint;
#endif
  RawCode* code = GetCodeObject();
  intptr_t cid = code->ptr()->owner_->GetClassId();
  ASSERT(cid == kNullCid || cid == kClassCid || cid == kFunctionCid);
  return cid == kNullCid || cid == kClassCid;
}


const char* StackFrame::ToCString() const {
  ASSERT(thread_ == Thread::Current());
  Zone* zone = Thread::Current()->zone();
  if (IsDartFrame()) {
    const Code& code = Code::Handle(LookupDartCode());
    ASSERT(!code.IsNull());
    const Object& owner = Object::Handle(code.owner());
    ASSERT(!owner.IsNull());
    if (owner.IsFunction()) {
      const Function& function = Function::Cast(owner);
      return zone->PrintToString(
          "[%-8s : sp(%#" Px ") fp(%#" Px ") pc(%#" Px ") %s ]",
          GetName(), sp(), fp(), pc(),
          function.ToFullyQualifiedCString());
    } else {
      return zone->PrintToString(
          "[%-8s : sp(%#" Px ") fp(%#" Px ") pc(%#" Px ") %s ]",
          GetName(), sp(), fp(), pc(),
          owner.ToCString());
    }
  } else {
    return zone->PrintToString(
        "[%-8s : sp(%#" Px ") fp(%#" Px ") pc(%#" Px ")]",
        GetName(), sp(), fp(), pc());
  }
}


void ExitFrame::VisitObjectPointers(ObjectPointerVisitor* visitor) {
  // There are no objects to visit in this frame.
}


void EntryFrame::VisitObjectPointers(ObjectPointerVisitor* visitor) {
  ASSERT(thread() == Thread::Current());
  // Visit objects between SP and (FP - callee_save_area).
  ASSERT(visitor != NULL);
  RawObject** first = reinterpret_cast<RawObject**>(sp());
  RawObject** last = reinterpret_cast<RawObject**>(
      fp() + (kExitLinkSlotFromEntryFp - 1) * kWordSize);
  visitor->VisitPointers(first, last);
}


void StackFrame::VisitObjectPointers(ObjectPointerVisitor* visitor) {
  // NOTE: This code runs while GC is in progress and runs within
  // a NoHandleScope block. Hence it is not ok to use regular Zone or
  // Scope handles. We use direct stack handles, the raw pointers in
  // these handles are not traversed. The use of handles is mainly to
  // be able to reuse the handle based code and avoid having to add
  // helper functions to the raw object interface.
  ASSERT(thread() == Thread::Current());
  ASSERT(visitor != NULL);
  NoSafepointScope no_safepoint;
  Code code;
  code = LookupDartCode();
  if (!code.IsNull()) {
    // Visit the code object.
    RawObject* raw_code = code.raw();
    visitor->VisitPointer(&raw_code);

    // Optimized frames have a stack map. We need to visit the frame based
    // on the stack map.
    Array maps;
    maps = Array::null();
    Stackmap map;
    const uword entry = reinterpret_cast<uword>(code.instructions()->ptr()) +
                        Instructions::HeaderSize();
    map = code.GetStackmap(pc() - entry, &maps, &map);
    if (!map.IsNull()) {
      RawObject** first = reinterpret_cast<RawObject**>(sp());
      RawObject** last = reinterpret_cast<RawObject**>(
          fp() + (kFirstLocalSlotFromFp * kWordSize));

      // A stack map is present in the code object, use the stack map to
      // visit frame slots which are marked as having objects.
      //
      // The layout of the frame is (lower addresses to the right):
      // | spill slots | outgoing arguments | saved registers |
      // |XXXXXXXXXXXXX|--------------------|XXXXXXXXXXXXXXXXX|
      //
      // The spill slots and any saved registers are described in the stack
      // map.  The outgoing arguments are assumed to be tagged; the number
      // of outgoing arguments is not explicitly tracked.
      //
      // TODO(kmillikin): This does not handle slow path calls with
      // arguments, where the arguments are pushed after the live registers.
      // Enable such calls.
      intptr_t length = map.Length();
      // Spill slots are at the 'bottom' of the frame.
      intptr_t spill_slot_count = length - map.RegisterBitCount();
      for (intptr_t bit = 0; bit < spill_slot_count; ++bit) {
        if (map.IsObject(bit)) {
          visitor->VisitPointer(last);
        }
        --last;
      }

      // The live registers at the 'top' of the frame comprise the rest of the
      // stack map.
      for (intptr_t bit = length - 1; bit >= spill_slot_count; --bit) {
        if (map.IsObject(bit)) {
          visitor->VisitPointer(first);
        }
        ++first;
      }

      // The last slot can be one slot (but not more) past the last slot
      // in the case that all slots were covered by the stack map.
      ASSERT((last + 1) >= first);
      visitor->VisitPointers(first, last);

      // Now visit other slots which might be part of the calling convention.
      first = reinterpret_cast<RawObject**>(
          fp() + ((kFirstLocalSlotFromFp + 1) * kWordSize));
      last = reinterpret_cast<RawObject**>(
          fp() + (kFirstObjectSlotFromFp * kWordSize));
      visitor->VisitPointers(first, last);
      return;
    }
  }
  // For normal unoptimized Dart frames and Stub frames each slot
  // between the first and last included are tagged objects.
  RawObject** first = reinterpret_cast<RawObject**>(sp());
  RawObject** last = reinterpret_cast<RawObject**>(
      fp() + (kFirstObjectSlotFromFp * kWordSize));
  visitor->VisitPointers(first, last);
}


RawFunction* StackFrame::LookupDartFunction() const {
  const Code& code = Code::Handle(LookupDartCode());
  if (!code.IsNull()) {
    return code.function();
  }
  return Function::null();
}


RawCode* StackFrame::LookupDartCode() const {
  // We add a no gc scope to ensure that the code below does not trigger
  // a GC as we are handling raw object references here. It is possible
  // that the code is called while a GC is in progress, that is ok.
#if !defined(TARGET_OS_WINDOWS)
  // On Windows, the profiler calls this from a separate thread where
  // Thread::Current() is NULL, so we cannot create a NoSafepointScope.
  NoSafepointScope no_safepoint;
#endif
  RawCode* code = GetCodeObject();
  if ((code != Code::null()) &&
      (code->ptr()->owner_->GetClassId() == kFunctionCid)) {
    return code;
  }
  return Code::null();
}


RawCode* StackFrame::GetCodeObject() const {
  const uword pc_marker =
      *(reinterpret_cast<uword*>(fp() + (kPcMarkerSlotFromFp * kWordSize)));
  ASSERT(pc_marker != 0);
  ASSERT(reinterpret_cast<RawObject*>(pc_marker)->GetClassId() == kCodeCid ||
         reinterpret_cast<RawObject*>(pc_marker) == Object::null());
  return reinterpret_cast<RawCode*>(pc_marker);
}


bool StackFrame::FindExceptionHandler(Thread* thread,
                                      uword* handler_pc,
                                      bool* needs_stacktrace,
                                      bool* has_catch_all) const {
  REUSABLE_CODE_HANDLESCOPE(thread);
  Code& code = reused_code_handle.Handle();
  code = LookupDartCode();
  if (code.IsNull()) {
    return false;  // Stub frames do not have exception handlers.
  }
  uword pc_offset = pc() - code.EntryPoint();

  REUSABLE_EXCEPTION_HANDLERS_HANDLESCOPE(thread);
  ExceptionHandlers& handlers = reused_exception_handlers_handle.Handle();
  handlers = code.exception_handlers();
  if (handlers.num_entries() == 0) {
    return false;
  }

  // Find pc descriptor for the current pc.
  REUSABLE_PC_DESCRIPTORS_HANDLESCOPE(thread);
  PcDescriptors& descriptors = reused_pc_descriptors_handle.Handle();
  descriptors = code.pc_descriptors();
  PcDescriptors::Iterator iter(descriptors, RawPcDescriptors::kAnyKind);
  while (iter.MoveNext()) {
    const intptr_t current_try_index = iter.TryIndex();
    if ((iter.PcOffset() == pc_offset) && (current_try_index != -1)) {
      RawExceptionHandlers::HandlerInfo handler_info;
      handlers.GetHandlerInfo(current_try_index, &handler_info);
      *handler_pc = code.EntryPoint() + handler_info.handler_pc_offset;
      *needs_stacktrace = handler_info.needs_stacktrace;
      *has_catch_all = handler_info.has_catch_all;
      return true;
    }
  }
  return false;
}


intptr_t StackFrame::GetTokenPos() const {
  const Code& code = Code::Handle(LookupDartCode());
  if (code.IsNull()) {
    return -1;  // Stub frames do not have token_pos.
  }
  uword pc_offset = pc() - code.EntryPoint();
  const PcDescriptors& descriptors =
      PcDescriptors::Handle(code.pc_descriptors());
  ASSERT(!descriptors.IsNull());
  PcDescriptors::Iterator iter(descriptors, RawPcDescriptors::kAnyKind);
  while (iter.MoveNext()) {
    if (iter.PcOffset() == pc_offset) {
      return iter.TokenPos();
    }
  }
  return -1;
}


bool StackFrame::IsValid() const {
  if (IsEntryFrame() || IsExitFrame() || IsStubFrame()) {
    return true;
  }
  return (LookupDartCode() != Code::null());
}


void StackFrameIterator::SetupLastExitFrameData() {
  ASSERT(thread_ != NULL);
  uword exit_marker = thread_->top_exit_frame_info();
  frames_.fp_ = exit_marker;
}


void StackFrameIterator::SetupNextExitFrameData() {
  uword exit_address = entry_.fp() + (kExitLinkSlotFromEntryFp * kWordSize);
  uword exit_marker = *reinterpret_cast<uword*>(exit_address);
  frames_.fp_ = exit_marker;
  frames_.sp_ = 0;
  frames_.pc_ = 0;
}


// Tell MemorySanitizer that generated code initializes part of the stack.
// TODO(koda): Limit to frames that are actually written by generated code.
static void UnpoisonStack(uword fp) {
  ASSERT(fp != 0);
  uword size = OSThread::GetSpecifiedStackSize();
  MSAN_UNPOISON(reinterpret_cast<void*>(fp - size), 2 * size);
}


StackFrameIterator::StackFrameIterator(bool validate, Thread* thread)
    : validate_(validate),
      entry_(thread),
      exit_(thread),
      frames_(thread),
      current_frame_(NULL),
      thread_(thread) {
  ASSERT((thread_ == Thread::Current()) ||
         OS::AllowStackFrameIteratorFromAnotherThread());
  SetupLastExitFrameData();  // Setup data for last exit frame.
}


StackFrameIterator::StackFrameIterator(uword last_fp, bool validate,
                                       Thread* thread)
    : validate_(validate),
      entry_(thread),
      exit_(thread),
      frames_(thread),
      current_frame_(NULL),
      thread_(thread) {
  ASSERT((thread_ == Thread::Current()) ||
         OS::AllowStackFrameIteratorFromAnotherThread());
  frames_.fp_ = last_fp;
  frames_.sp_ = 0;
  frames_.pc_ = 0;
}


StackFrameIterator::StackFrameIterator(uword fp, uword sp, uword pc,
                                       bool validate, Thread* thread)
    : validate_(validate),
      entry_(thread),
      exit_(thread),
      frames_(thread),
      current_frame_(NULL),
      thread_(thread) {
  ASSERT((thread_ == Thread::Current()) ||
         OS::AllowStackFrameIteratorFromAnotherThread());
  frames_.fp_ = fp;
  frames_.sp_ = sp;
  frames_.pc_ = pc;
}


StackFrame* StackFrameIterator::NextFrame() {
  // When we are at the start of iteration after having created an
  // iterator object, current_frame_ will be NULL as we haven't seen
  // any frames yet (unless we start iterating in the simulator from a given
  // triplet of fp, sp, and pc). At this point, if NextFrame is called, it tries
  // to set up the next exit frame by reading the top_exit_frame_info
  // from the isolate. If we do not have any dart invocations yet,
  // top_exit_frame_info will be 0 and so we would return NULL.

  // current_frame_ will also be NULL, when we are at the end of having
  // iterated through all the frames. If NextFrame is called at this
  // point, we will try and set up the next exit frame, but since we are
  // at the end of the iteration, fp_ will be 0 and we would return NULL.
  if (current_frame_ == NULL) {
    if (!HasNextFrame()) {
      return NULL;
    }
    UnpoisonStack(frames_.fp_);
    if (frames_.pc_ == 0) {
      // Iteration starts from an exit frame given by its fp.
      current_frame_ = NextExitFrame();
    } else if (*(reinterpret_cast<uword*>(
        frames_.fp_ + (kSavedCallerFpSlotFromFp * kWordSize))) == 0) {
      // Iteration starts from an entry frame given by its fp, sp, and pc.
      current_frame_ = NextEntryFrame();
    } else {
      // Iteration starts from a Dart or stub frame given by its fp, sp, and pc.
      current_frame_ = frames_.NextFrame(validate_);
    }
    return current_frame_;
  }
  ASSERT((validate_ == kDontValidateFrames) || current_frame_->IsValid());
  if (current_frame_->IsEntryFrame()) {
    if (HasNextFrame()) {  // We have another chained block.
      current_frame_ = NextExitFrame();
      return current_frame_;
    }
    current_frame_ = NULL;  // No more frames.
    return current_frame_;
  }
  ASSERT(current_frame_->IsExitFrame() ||
         current_frame_->IsDartFrame(validate_) ||
         current_frame_->IsStubFrame());

  // Consume dart/stub frames using StackFrameIterator::FrameSetIterator
  // until we are out of dart/stub frames at which point we return the
  // corresponding entry frame for that set of dart/stub frames.
  current_frame_ =
      (frames_.HasNext()) ? frames_.NextFrame(validate_) : NextEntryFrame();
  return current_frame_;
}


StackFrame* StackFrameIterator::FrameSetIterator::NextFrame(bool validate) {
  StackFrame* frame;
  ASSERT(HasNext());
  frame = &stack_frame_;
  frame->sp_ = sp_;
  frame->fp_ = fp_;
  frame->pc_ = pc_;
  sp_ = frame->GetCallerSp();
  fp_ = frame->GetCallerFp();
  pc_ = frame->GetCallerPc();
  ASSERT((validate == kDontValidateFrames) || frame->IsValid());
  return frame;
}


ExitFrame* StackFrameIterator::NextExitFrame() {
  exit_.sp_ = frames_.sp_;
  exit_.fp_ = frames_.fp_;
  exit_.pc_ = frames_.pc_;
  frames_.sp_ = exit_.GetCallerSp();
  frames_.fp_ = exit_.GetCallerFp();
  frames_.pc_ = exit_.GetCallerPc();
  ASSERT(exit_.IsValid());
  return &exit_;
}


EntryFrame* StackFrameIterator::NextEntryFrame() {
  ASSERT(!frames_.HasNext());
  entry_.sp_ = frames_.sp_;
  entry_.fp_ = frames_.fp_;
  entry_.pc_ = frames_.pc_;
  SetupNextExitFrameData();  // Setup data for next exit frame in chain.
  ASSERT(entry_.IsValid());
  return &entry_;
}


InlinedFunctionsIterator::InlinedFunctionsIterator(const Code& code, uword pc)
  : index_(0),
    num_materializations_(0),
    code_(Code::Handle(code.raw())),
    deopt_info_(TypedData::Handle()),
    function_(Function::Handle()),
    pc_(pc),
    deopt_instructions_(),
    object_table_(ObjectPool::Handle()) {
  ASSERT(code_.is_optimized());
  ASSERT(pc_ != 0);
  ASSERT(code.ContainsInstructionAt(pc));
  ICData::DeoptReasonId deopt_reason = ICData::kDeoptUnknown;
  uint32_t deopt_flags = 0;
  deopt_info_ = code_.GetDeoptInfoAtPc(pc, &deopt_reason, &deopt_flags);
  if (deopt_info_.IsNull()) {
    // This is the case when a call without deopt info in optimized code
    // throws an exception. (e.g. in the parameter copying prologue).
    // In that case there won't be any inlined frames.
    function_ = code_.function();
  } else {
    // Unpack deopt info into instructions (translate away suffixes).
    const Array& deopt_table = Array::Handle(code_.deopt_info_array());
    ASSERT(!deopt_table.IsNull());
    DeoptInfo::Unpack(deopt_table, deopt_info_, &deopt_instructions_);
    num_materializations_ = DeoptInfo::NumMaterializations(deopt_instructions_);
    object_table_ = code_.GetObjectPool();
    Advance();
  }
}


void InlinedFunctionsIterator::Advance() {
  // Iterate over the deopt instructions and determine the inlined
  // functions if any and iterate over them.
  ASSERT(!Done());

  if (deopt_info_.IsNull()) {
    SetDone();
    return;
  }

  ASSERT(deopt_instructions_.length() != 0);
  while (index_ < deopt_instructions_.length()) {
    DeoptInstr* deopt_instr = deopt_instructions_[index_++];
    if (deopt_instr->kind() == DeoptInstr::kRetAddress) {
      pc_ = DeoptInstr::GetRetAddress(deopt_instr, object_table_, &code_);
      function_ = code_.function();
      return;
    }
  }
  SetDone();
}


// Finds the potential offset for the current function's FP if the
// current frame were to be deoptimized.
intptr_t InlinedFunctionsIterator::GetDeoptFpOffset() const {
  ASSERT(deopt_instructions_.length() != 0);
  for (intptr_t index = index_;
       index < deopt_instructions_.length();
       index++) {
    DeoptInstr* deopt_instr = deopt_instructions_[index];
    if (deopt_instr->kind() == DeoptInstr::kCallerFp) {
      return (index - num_materializations_);
    }
  }
  UNREACHABLE();
  return 0;
}


}  // namespace dart