debugserver memory writes and instruction-cache flushes

llvm-project/lldb/tools/debugserver/source/MacOSX/MachVMMemory.cpp · 402 lines · browse source

Region-aware debugger writes: temporarily make mapped memory writable, write page-sized chunks with mach_vm_write, and flush the target instruction cache on non-x86 systems.

MachVMMemory::Write source

nub_size_t MachVMMemory::Write(task_t task, nub_addr_t address,
                               const void *data, nub_size_t data_count) {
  MachVMRegion vmRegion(task);

  nub_size_t total_bytes_written = 0;
  nub_addr_t curr_addr = address;
  const uint8_t *curr_data = (const uint8_t *)data;

  while (total_bytes_written < data_count) {
    if (vmRegion.GetRegionForAddress(curr_addr)) {
      mach_vm_size_t curr_data_count = data_count - total_bytes_written;
      mach_vm_size_t region_bytes_left = vmRegion.BytesRemaining(curr_addr);
      if (region_bytes_left == 0) {
        break;
      }
      if (curr_data_count > region_bytes_left)
        curr_data_count = region_bytes_left;

      if (vmRegion.SetProtections(curr_addr, curr_data_count,
                                  VM_PROT_READ | VM_PROT_WRITE)) {
        nub_size_t bytes_written =
            WriteRegion(task, curr_addr, curr_data, curr_data_count);
        if (bytes_written <= 0) {
          // Status should have already be posted by WriteRegion...
          break;
        } else {
          total_bytes_written += bytes_written;
          curr_addr += bytes_written;
          curr_data += bytes_written;
        }
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MachVMMemory::WriteRegion source

nub_size_t MachVMMemory::WriteRegion(task_t task, const nub_addr_t address,
                                     const void *data,
                                     const nub_size_t data_count) {
  if (data == NULL || data_count == 0)
    return 0;

  nub_size_t total_bytes_written = 0;
  nub_addr_t curr_addr = address;
  const uint8_t *curr_data = (const uint8_t *)data;
  while (total_bytes_written < data_count) {
    mach_msg_type_number_t curr_data_count =
        static_cast<mach_msg_type_number_t>(MaxBytesLeftInPage(
            task, curr_addr, data_count - total_bytes_written));
    m_err =
        ::mach_vm_write(task, curr_addr, (pointer_t)curr_data, curr_data_count);
    if (DNBLogCheckLogBit(LOG_MEMORY) || m_err.Fail())
      m_err.LogThreaded("::mach_vm_write ( task = 0x%4.4x, addr = 0x%8.8llx, "
                        "data = %8.8p, dataCnt = %u )",
                        task, (uint64_t)curr_addr, curr_data, curr_data_count);

#if !defined(__i386__) && !defined(__x86_64__)
    vm_machine_attribute_val_t mattr_value = MATTR_VAL_CACHE_FLUSH;

    m_err = ::vm_machine_attribute(task, curr_addr, curr_data_count,
                                   MATTR_CACHE, &mattr_value);
    if (DNBLogCheckLogBit(LOG_MEMORY) || m_err.Fail())
      m_err.LogThreaded("::vm_machine_attribute ( task = 0x%4.4x, addr = "
                        "0x%8.8llx, size = %u, attr = MATTR_CACHE, mattr_value "
                        "=> MATTR_VAL_CACHE_FLUSH )",
                        task, (uint64_t)curr_addr, curr_data_count);
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