client/crashpad_info.cc

// Copyright 2014 The Crashpad Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "client/crashpad_info.h"

#include <type_traits>

#include "base/numerics/safe_conversions.h"
#include "build/build_config.h"
#include "util/misc/address_sanitizer.h"
#include "util/misc/from_pointer_cast.h"

#if BUILDFLAG(IS_APPLE)
#include <mach-o/loader.h>
#endif

namespace {

// Don’t change this when simply adding fields. Readers will size-check the
// structure and ignore fields they’re aware of when not present, as well as
// fields they’re not aware of. Only change this when introducing an
// incompatible layout, with the understanding that existing readers will not
// understand new versions.
constexpr uint32_t kCrashpadInfoVersion = 1;

// Creates a `UserDataMinidumpStreamListEntry` with the given fields, and
// returns a pointer to it. The caller takes ownership of the returned object.
crashpad::internal::UserDataMinidumpStreamListEntry* CreateListEntry(
    uint64_t next,
    uint32_t stream_type,
    const void* data,
    size_t size) {
  auto to_be_added = new crashpad::internal::UserDataMinidumpStreamListEntry();
  to_be_added->next = next;
  to_be_added->stream_type = stream_type;
  to_be_added->base_address = crashpad::FromPointerCast<uint64_t>(data);
  to_be_added->size = base::checked_cast<uint64_t>(size);
  return to_be_added;
}

}  // namespace

namespace crashpad {

static_assert(std::is_standard_layout<CrashpadInfo>::value,
              "CrashpadInfo must be standard layout");

// This structure needs to be stored somewhere that is easy to find without
// external information.
//
// It isn’t placed in an unnamed namespace: hopefully, this will catch attempts
// to place multiple copies of this structure into the same module. If that’s
// attempted, and the name of the symbol is the same in each translation unit,
// it will result in a linker error, which is better than having multiple
// structures show up.
//
// This may result in a static module initializer in debug-mode builds, but
// because it’s POD, no code should need to run to initialize this under
// release-mode optimization.

#if BUILDFLAG(IS_POSIX)
__attribute__((

#if BUILDFLAG(IS_APPLE)
    // Put the structure in a well-known section name where it can be easily
    // found without having to consult the symbol table.
    section(SEG_DATA ",crashpad_info"),
#endif

#if defined(ADDRESS_SANITIZER)
    // AddressSanitizer would add a trailing red zone of at least 32 bytes,
    // which would be reflected in the size of the custom section. This confuses
    // MachOImageReader::GetCrashpadInfo(), which finds that the section’s size
    // disagrees with the structure’s size_ field. By specifying an alignment
    // greater than the red zone size, the red zone will be suppressed.
    aligned(64),
#endif  // defined(ADDRESS_SANITIZER)

    // There's no need to expose this as a public symbol from the symbol table.
    // All accesses from the outside can locate the well-known section name.
    visibility("hidden"),

    // The “used” attribute prevents the structure from being dead-stripped.
    used))

#elif BUILDFLAG(IS_WIN)

// Put the struct in a section name CPADinfo where it can be found without the
// symbol table.
#pragma section("CPADinfo", read, write)
__declspec(allocate("CPADinfo"))

#else  // !BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_WIN)
#error Port
#endif  // !BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_WIN)

CrashpadInfo g_crashpad_info;

extern "C" int* CRASHPAD_NOTE_REFERENCE;

// static
CrashpadInfo* CrashpadInfo::GetCrashpadInfo() {
#if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID) || \
    BUILDFLAG(IS_FUCHSIA)
  // This otherwise-unused reference is used so that any module that
  // references GetCrashpadInfo() will also include the note in the
  // .note.crashpad.info section. That note in turn contains the address of
  // g_crashpad_info. This allows the module reader to find the CrashpadInfo
  // structure without requiring the use of the dynamic symbol table.
  static volatile int* pointer_to_note_section = CRASHPAD_NOTE_REFERENCE;
  (void)pointer_to_note_section;
#endif
  return &g_crashpad_info;
}

CrashpadInfo::CrashpadInfo()
    : signature_(kSignature),
      size_(sizeof(*this)),
      version_(kCrashpadInfoVersion),
      indirectly_referenced_memory_cap_(0),
      padding_0_(0),
      crashpad_handler_behavior_(TriState::kUnset),
      system_crash_reporter_forwarding_(TriState::kUnset),
      gather_indirectly_referenced_memory_(TriState::kUnset),
      padding_1_(0),
      extra_memory_ranges_(nullptr),
      simple_annotations_(nullptr),
      user_data_minidump_stream_head_(nullptr),
      annotations_list_(nullptr) {}

UserDataMinidumpStreamHandle* CrashpadInfo::AddUserDataMinidumpStream(
    uint32_t stream_type,
    const void* data,
    size_t size) {
  user_data_minidump_stream_head_ = CreateListEntry(
      crashpad::FromPointerCast<uint64_t>(user_data_minidump_stream_head_),
      stream_type,
      data,
      size);
  return user_data_minidump_stream_head_;
}

UserDataMinidumpStreamHandle* CrashpadInfo::UpdateUserDataMinidumpStream(
    UserDataMinidumpStreamHandle* stream_to_update,
    uint32_t stream_type,
    const void* data,
    size_t size) {
  // Create a new stream that points to the node `stream_to_update` points to.
  const auto new_stream =
      CreateListEntry(stream_to_update->next, stream_type, data, size);

  // If `stream_to_update` is head of the list, replace the head with
  // `new_stream`.
  if (stream_to_update == user_data_minidump_stream_head_) {
    user_data_minidump_stream_head_ = new_stream;
  } else {
    // Otherwise, find the node before `stream_to_update`, and make it point to
    // `new_stream` instead.
    auto current = user_data_minidump_stream_head_;
    while (current) {
      auto next = reinterpret_cast<internal::UserDataMinidumpStreamListEntry*>(
          current->next);
      if (next == stream_to_update) {
        current->next = FromPointerCast<uint64_t>(new_stream);
        break;
      }
      current = next;
    }
    CHECK(current)
        << "Tried to update a UserDataMinidumpStream that doesn't exist";
  }

  delete stream_to_update;
  return new_stream;
}

}  // namespace crashpad