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      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
    115