arguments.h

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// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#ifndef V8_EXECUTION_ARGUMENTS_H_
#define V8_EXECUTION_ARGUMENTS_H_
 
#include "src/execution/clobber-registers.h"
#include "src/handles/handles.h"
#include "src/logging/runtime-call-stats-scope.h"
#include "src/objects/objects.h"
#include "src/objects/slots.h"
#include "src/sandbox/check.h"
#include "src/tracing/trace-event.h"
#include "src/utils/allocation.h"
 
namespace v8 {
namespace internal {
 
// Arguments provides access to runtime call parameters.
//
// It uses the fact that the instance fields of Arguments
// (length_, arguments_) are "overlayed" with the parameters
// (no. of parameters, and the parameter pointer) passed so
// that inside the C++ function, the parameters passed can
// be accessed conveniently:
//
//   Object Runtime_function(Arguments args) {
//     ... use args[i] here ...
//   }
//
// Note that length_ (whose value is in the integer range) is defined
// as intptr_t to provide endian-neutrality on 64-bit archs.
 
template <ArgumentsType arguments_type>
class Arguments {
 public:
  // Scope to temporarily change the value of an argument.
  class ChangeValueScope {
   public:
    inline ChangeValueScope(Isolate* isolate, Arguments* args, int index,
                            Tagged<Object> value);
    ~ChangeValueScope() { *location_ = (*old_value_).ptr(); }
 
   private:
    Address* location_;
    DirectHandle<Object> old_value_;
  };
 
  Arguments(int length, Address* arguments)
      : length_(length), arguments_(arguments) {
    DCHECK_GE(length_, 0);
  }
 
  V8_INLINE Tagged<Object> operator[](int index) const {
    return Tagged<Object>(*address_of_arg_at(index));
  }
 
  template <class S = Object>
  V8_INLINE Handle<S> at(int index) const;
 
  V8_INLINE FullObjectSlot slot_from_address_at(int index, int offset) const;
 
  V8_INLINE int smi_value_at(int index) const;
  V8_INLINE uint32_t positive_smi_value_at(int index) const;
 
  V8_INLINE int tagged_index_value_at(int index) const;
 
  V8_INLINE double number_value_at(int index) const;
 
  V8_INLINE Handle<Object> atOrUndefined(Isolate* isolate, int index) const;
 
  V8_INLINE Address* address_of_arg_at(int index) const {
    // Corruption of certain heap objects (see e.g. crbug.com/1507223) can lead
    // to OOB arguments access, and therefore OOB stack access. This SBXCHECK
    // defends against that.
    // Note: "LE" is intentional: it's okay to compute the address of the
    // first nonexistent entry.
    SBXCHECK_LE(static_cast<uint32_t>(index), static_cast<uint32_t>(length_));
    uintptr_t offset = index * kSystemPointerSize;
    if (arguments_type == ArgumentsType::kJS) {
      offset = (length_ - index - 1) * kSystemPointerSize;
    }
    return reinterpret_cast<Address*>(reinterpret_cast<Address>(arguments_) -
                                      offset);
  }
 
  // Get the total number of arguments including the receiver.
  V8_INLINE int length() const { return static_cast<int>(length_); }
 
 private:
  intptr_t length_;
  Address* arguments_;
};
 
template <ArgumentsType T>
template <class S>
Handle<S> Arguments<T>::at(int index) const {
  Handle<Object> obj = Handle<Object>(address_of_arg_at(index));
  return Cast<S>(obj);
}
 
template <ArgumentsType T>
FullObjectSlot Arguments<T>::slot_from_address_at(int index, int offset) const {
  Address* location = *reinterpret_cast<Address**>(address_of_arg_at(index));
  return FullObjectSlot(location + offset);
}
 
#ifdef DEBUG
#define CLOBBER_DOUBLE_REGISTERS() ClobberDoubleRegisters(1, 2, 3, 4);
#else
#define CLOBBER_DOUBLE_REGISTERS()
#endif
 
// TODO(cbruni): add global flag to check whether any tracing events have been
// enabled.
#ifdef V8_RUNTIME_CALL_STATS
#define RUNTIME_ENTRY_WITH_RCS(Type, InternalType, Convert, Name)             \
  V8_NOINLINE static Type Stats_##Name(int args_length, Address* args_object, \
                                       Isolate* isolate) {                    \
    RCS_SCOPE(isolate, RuntimeCallCounterId::k##Name);                        \
    TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.runtime"),                     \
                 "V8.Runtime_" #Name);                                        \
    RuntimeArguments args(args_length, args_object);                          \
    return Convert(__RT_impl_##Name(args, isolate));                          \
  }
 
#define TEST_AND_CALL_RCS(Name)                                \
  if (V8_UNLIKELY(TracingFlags::is_runtime_stats_enabled())) { \
    return Stats_##Name(args_length, args_object, isolate);    \
  }
 
#else  // V8_RUNTIME_CALL_STATS
#define RUNTIME_ENTRY_WITH_RCS(Type, InternalType, Convert, Name)
#define TEST_AND_CALL_RCS(Name)
 
#endif  // V8_RUNTIME_CALL_STATS
 
#define RUNTIME_FUNCTION_RETURNS_TYPE(Type, InternalType, Convert, Name)   \
  static V8_INLINE InternalType __RT_impl_##Name(RuntimeArguments args,    \
                                                 Isolate* isolate);        \
  RUNTIME_ENTRY_WITH_RCS(Type, InternalType, Convert, Name)                \
  Type Name(int args_length, Address* args_object, Isolate* isolate) {     \
    DCHECK(isolate->context().is_null() || IsContext(isolate->context())); \
    DCHECK(isolate->IsOnCentralStack());                                   \
    CLOBBER_DOUBLE_REGISTERS();                                            \
    TEST_AND_CALL_RCS(Name)                                                \
    RuntimeArguments args(args_length, args_object);                       \
    return Convert(__RT_impl_##Name(args, isolate));                       \
  }                                                                        \
                                                                           \
  static InternalType __RT_impl_##Name(RuntimeArguments args, Isolate* isolate)
 
#ifdef DEBUG
#define BUILTIN_CONVERT_RESULT(x) (isolate->VerifyBuiltinsResult(x)).ptr()
#define BUILTIN_CONVERT_RESULT_PAIR(x) isolate->VerifyBuiltinsResult(x)
#else  // DEBUG
#define BUILTIN_CONVERT_RESULT(x) (x).ptr()
#define BUILTIN_CONVERT_RESULT_PAIR(x) (x)
#endif  // DEBUG
 
#define RUNTIME_FUNCTION(Name)                           \
  RUNTIME_FUNCTION_RETURNS_TYPE(Address, Tagged<Object>, \
                                BUILTIN_CONVERT_RESULT, Name)
 
#define RUNTIME_FUNCTION_RETURN_PAIR(Name)              \
  RUNTIME_FUNCTION_RETURNS_TYPE(ObjectPair, ObjectPair, \
                                BUILTIN_CONVERT_RESULT_PAIR, Name)
 
}  // namespace internal
}  // namespace v8
 
#endif  // V8_EXECUTION_ARGUMENTS_H_