Dump EPT contents for an isolate

external-pointer-table-tracer.cc

// Copyright 2024 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.

#include "src/sandbox/external-pointer-table-tracer.h"

#include <iostream>

#include "src/common/globals.h"
#include "src/execution/isolate.h"
#include "src/sandbox/external-entity-table-inl.h"
#include "src/sandbox/external-pointer-table.h"
#include "src/utils/ostreams.h"

namespace v8 {

namespace internal {

// static 
void EPTTracer::Print(IsolateForSandbox ifs) {
  //ExternalPointerTable& ept = ifs.isolate()->external_pointer_table();
  ExternalPointerTable& shared_ept = ifs.isolate()->shared_external_pointer_table();
  StdoutStream os;
  /*if (reinterpret_cast<ExternalPointerTableEntry*>(ept.base()) != nullptr) {
    os << "External Pointer Table Layout" << std::endl;
    os << "Base address: 0x" << std::hex << ept.base() << std::endl;
  }*/
  if (reinterpret_cast<ExternalPointerTableEntry*>(shared_ept.base()) != nullptr) {
    os << "Shared External Pointer Table Layout" << std::endl;
    os << "Base address: 0x" << std::hex << shared_ept.base() << std::endl;
    auto* space = ifs.isolate()->shared_external_pointer_space();
    DCHECK(space->BelongsTo(&shared_ept));
    base::MutexGuard guard(&space->mutex_);
    if (!space->is_empty()) {
      os << "Number of segments in the space: " << space->num_segments() << std::endl;
      for (auto segment : space->segments_) {
        os << "Segment: " << segment.number() << std::endl;
        uint32_t first = segment.first_entry();
        uint32_t last = segment.last_entry();
        os << "| Index | Marked | Encoded Address | Description |" << std::endl;
        for (uint32_t i = first; i < last; i++) {
          auto& entry = reinterpret_cast<ExternalPointerTableEntry*>(shared_ept.base())[i];
          bool is_freelist = entry.GetRawPayload().ContainsFreelistLink();
          if (is_freelist)
            continue;
          bool is_marked = entry.GetRawPayload().HasMarkBitSet();
          os << "| " << i << " | " << is_marked << " | ";
          uint64_t value = static_cast<uint64_t>(entry.GetRawPayload().encoded_word());
          for (int i = 63; i >= 0; --i) {
            if (value & (1ULL << i)) {
              os << '1';
            } else {
              os << '0';
            }
          }
          if (is_freelist) {
            //uint32_t next_free_entry = entry.GetRawPayload().ExtractFreelistLink();
            //os << " | Next free entry index: " << next_free_entry << " |" << std::endl;
          } else {
            os << " | External pointer object |" << std::endl;
          }
        }
      }
    }
  }
  os << std::endl << std::flush;
}

}  // namespace internal

}  // namespace v8

sample.txt

demohan@Deepaks-MacBook-Pro v8 % ./out/Release/d8 --expose-gc --expose-externalize-string ./test/mjsunit/large-external-string.js
Address of resource data to validate: 0x600002afcb91
Shared External Pointer Table Layout
Base address: 0x340000000
Number of segments in the space: 1
Segment: 1
| Index | Marked | Encoded Address | Description |
| 1000 | 1 | 0100000000010111011000000000000000000000000111111100001010000000 | External pointer object |
| 1001 | 1 | 0100000000011011011000000000000000000010101011111100101110010001 | External pointer object |

Address of resource to validate: 0x6000001fc280
Address of resource data to validate: 0x125705171
Shared External Pointer Table Layout
Base address: 0x340000000
Number of segments in the space: 1
Segment: 1
| Index | Marked | Encoded Address | Description |
| 1000 | 1 | 0100000000010111011000000000000000000000000111111100001010000000 | External pointer object |
| 1001 | 1 | 0100000000011011011000000000000000000010101011111100101110010001 | External pointer object |
| 1002 | 1 | 0100000000010111011000000000000000000000000111111100001010100000 | External pointer object |
| 1003 | 1 | 0100000000011011000000000000000100100101011100000101000101110001 | External pointer object |

Address of resource to validate: 0x6000001fc2a0
Address of resource data to validate: 0x1181c0000
Shared External Pointer Table Layout
Base address: 0x340000000
Number of segments in the space: 1
Segment: 1
| Index | Marked | Encoded Address | Description |
| 1000 | 1 | 0100000000010111011000000000000000000000000111111100001010000000 | External pointer object |
| 1001 | 1 | 0100000000011011011000000000000000000010101011111100101110010001 | External pointer object |
| 1002 | 1 | 0100000000010111011000000000000000000000000111111100001010100000 | External pointer object |
| 1003 | 1 | 0100000000011011000000000000000100100101011100000101000101110001 | External pointer object |
| 1004 | 1 | 0100000000010111011000000000000000000000000111101000100001000000 | External pointer object |
| 1005 | 1 | 0100000000011011000000000000000100011000000111000000000000000000 | External pointer object |
demohan@Deepaks-MacBook-Pro v8 % 

Table layout with separate space for double pointer-sized word entries

Shared External Pointer Table Layout
Base address: 0x340000000
Number of segments in the space: 1
Segment: 1
| Index | Marked | Encoded Address | Description |
| 2000 | 1 | 00100000000010111011000000000000000000000011011001101000101100000 | External pointer object |
| 2001 | 1 | 00100000000010111011000000000000000000000011011001101000110000000 | External pointer object |
| 2002 | 1 | 00100000000010111011000000000000000000000011011000100011001000000 | External pointer object |
Number of segments in the space: 1
Segment: 2
| Index | Marked | Encoded Address | Description |
| 2000 | 1 | 101000000000110110110000000000000000000101101110000001001011000010100000000011011011000000000000000000010110111000000100101100001 | External pointer object |
| 2001 | 1 | 101000000000110110000000000000001001001001111000001010111010100010100000000011011000000000000000100100100111100000101011101010001 | External pointer object |
| 2002 | 1 | 001000000000110110000000000000001000110000000000010000000000000000100000000011011000000000000000100011000000000001000000000000000 | External pointer object |