base/debug/debugger_win.cc

   1 // Copyright (c) 2010 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 "base/debug/debugger.h"
   6
   7 #include <windows.h>
   8 #include <dbghelp.h>
   9
  10 #include "base/basictypes.h"
  11 #include "base/logging.h"
  12
  13 namespace base {
  14 namespace debug {
  15
  16 namespace {
  17
  18 // Minimalist key reader.
  19 // Note: Does not use the CRT.
  20 bool RegReadString(HKEY root, const wchar_t* subkey,
  21                    const wchar_t* value_name, wchar_t* buffer, int* len) {
  22   HKEY key = NULL;
  23   DWORD res = RegOpenKeyEx(root, subkey, 0, KEY_READ, &key);
  24   if (ERROR_SUCCESS != res || key == NULL)
  25     return false;
  26
  27   DWORD type = 0;
  28   DWORD buffer_size = *len * sizeof(wchar_t);
  29   // We don't support REG_EXPAND_SZ.
  30   res = RegQueryValueEx(key, value_name, NULL, &type,
  31                         reinterpret_cast<BYTE*>(buffer), &buffer_size);
  32   if (ERROR_SUCCESS == res && buffer_size != 0 && type == REG_SZ) {
  33     // Make sure the buffer is NULL terminated.
  34     buffer[*len - 1] = 0;
  35     *len = lstrlen(buffer);
  36     RegCloseKey(key);
  37     return true;
  38   }
  39   RegCloseKey(key);
  40   return false;
  41 }
  42
  43 // Replaces each "%ld" in input per a value. Not efficient but it works.
  44 // Note: Does not use the CRT.
  45 bool StringReplace(const wchar_t* input, int value, wchar_t* output,
  46                    int output_len) {
  47   memset(output, 0, output_len*sizeof(wchar_t));
  48   int input_len = lstrlen(input);
  49
  50   for (int i = 0; i < input_len; ++i) {
  51     int current_output_len = lstrlen(output);
  52
  53     if (input[i] == L'%' && input[i + 1] == L'l' && input[i + 2] == L'd') {
  54       // Make sure we have enough place left.
  55       if ((current_output_len + 12) >= output_len)
  56         return false;
  57
  58       // Cheap _itow().
  59       wsprintf(output+current_output_len, L"%d", value);
  60       i += 2;
  61     } else {
  62       if (current_output_len >= output_len)
  63         return false;
  64       output[current_output_len] = input[i];
  65     }
  66   }
  67   return true;
  68 }
  69
  70 }  // namespace
  71
  72 // Note: Does not use the CRT.
  73 bool SpawnDebuggerOnProcess(unsigned process_id) {
  74   wchar_t reg_value[1026];
  75   int len = arraysize(reg_value);
  76   if (RegReadString(HKEY_LOCAL_MACHINE,
  77       L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug",
  78       L"Debugger", reg_value, &len)) {
  79     wchar_t command_line[1026];
  80     if (StringReplace(reg_value, process_id, command_line,
  81                       arraysize(command_line))) {
  82       // We don't mind if the debugger is present because it will simply fail
  83       // to attach to this process.
  84       STARTUPINFO startup_info = {0};
  85       startup_info.cb = sizeof(startup_info);
  86       PROCESS_INFORMATION process_info = {0};
  87
  88       if (CreateProcess(NULL, command_line, NULL, NULL, FALSE, 0, NULL, NULL,
  89                         &startup_info, &process_info)) {
  90         CloseHandle(process_info.hThread);
  91         WaitForInputIdle(process_info.hProcess, 10000);
  92         CloseHandle(process_info.hProcess);
  93         return true;
  94       }
  95     }
  96   }
  97   return false;
  98 }
  99
 100 bool BeingDebugged() {
 101   return ::IsDebuggerPresent() != 0;
 102 }
 103
 104 void BreakDebugger() {
 105   if (IsDebugUISuppressed())
 106     _exit(1);
 107   __debugbreak();
 108 #if defined(NDEBUG)
 109   _exit(1);
 110 #endif
 111 }
 112
 113 }  // namespace debug
 114 }  // namespace base