chrome_elf/ntdll_cache.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include <stdint.h>
   6 #include <windows.h>
   7
   8 #include "chrome_elf/ntdll_cache.h"
   9
  10 FunctionLookupTable g_ntdll_lookup;
  11
  12 void InitCache() {
  13   HMODULE ntdll_handle = ::GetModuleHandle(L"ntdll.dll");
  14
  15   // To find the Export Address Table address, we start from the DOS header.
  16   // The module handle is actually the address of the header.
  17   IMAGE_DOS_HEADER* dos_header =
  18       reinterpret_cast<IMAGE_DOS_HEADER*>(ntdll_handle);
  19   // The e_lfanew is an offset from the DOS header to the NT header. It should
  20   // never be 0.
  21   IMAGE_NT_HEADERS* nt_headers = reinterpret_cast<IMAGE_NT_HEADERS*>(
  22       ntdll_handle + dos_header->e_lfanew / sizeof(uint32_t));
  23   // For modules that have an import address table, its offset from the
  24   // DOS header is stored in the second data directory's VirtualAddress.
  25   if (!nt_headers->OptionalHeader.DataDirectory[0].VirtualAddress)
  26     return;
  27
  28   BYTE* base_addr = reinterpret_cast<BYTE*>(ntdll_handle);
  29
  30   IMAGE_DATA_DIRECTORY* exports_data_dir =
  31       &nt_headers->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT];
  32
  33   IMAGE_EXPORT_DIRECTORY* exports = reinterpret_cast<IMAGE_EXPORT_DIRECTORY*>(
  34       base_addr + exports_data_dir->VirtualAddress);
  35
  36   WORD* ordinals = reinterpret_cast<WORD*>(
  37       base_addr + exports->AddressOfNameOrdinals);
  38   DWORD* names = reinterpret_cast<DWORD*>(
  39       base_addr + exports->AddressOfNames);
  40   DWORD* funcs = reinterpret_cast<DWORD*>(
  41       base_addr + exports->AddressOfFunctions);
  42   int num_entries = exports->NumberOfNames;
  43
  44   for (int i = 0; i < num_entries; i++) {
  45     char* name = reinterpret_cast<char*>(base_addr + names[i]);
  46     WORD ord =  ordinals[i];
  47     DWORD func = funcs[ord];
  48     FARPROC func_addr = reinterpret_cast<FARPROC>(func + base_addr);
  49     g_ntdll_lookup[std::string(name)] = func_addr;
  50   }
  51 }