1 /*-------------------------------------------------------------------------
2 *
3 * crashdump.c
4 * Automatic crash dump creation for PostgreSQL on Windows
5 *
6 * The crashdump feature traps unhandled win32 exceptions produced by the
7 * backend, and tries to produce a Windows MiniDump crash
8 * dump for later debugging and analysis. The machine performing the dump
9 * doesn't need any special debugging tools; the user only needs to send
10 * the dump to somebody who has the same version of PostgreSQL and has debugging
11 * tools.
12 *
13 * crashdump module originally by Craig Ringer <ringerc@ringerc.id.au>
14 *
15 * LIMITATIONS
16 * ===========
17 * This *won't* work in hard OOM situations or stack overflows.
18 *
19 * For those, it'd be necessary to take a much more complicated approach where
20 * the handler switches to a new stack (if it can) and forks a helper process
21 * to debug it self.
22 *
23 * POSSIBLE FUTURE WORK
24 * ====================
25 * For bonus points, the crash dump format permits embedding of user-supplied
26 * data. If there's anything else that should always be supplied with a crash
27 * dump (postgresql.conf? Last few lines of a log file?), it could potentially
28 * be added, though at the cost of a greater chance of the crash dump failing.
29 *
30 *
31 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
32 *
33 * IDENTIFICATION
34 * src/backend/port/win32/crashdump.c
35 *
36 *-------------------------------------------------------------------------
37 */
38
39 #include "postgres.h"
40
41 #define WIN32_LEAN_AND_MEAN
42
43 /*
44 * Some versions of the MS SDK contain "typedef enum { ... } ;" which the MS
45 * compiler quite sanely complains about. Well done, Microsoft.
46 * This pragma disables the warning just while we include the header.
47 * The pragma is known to work with all (as at the time of writing) supported
48 * versions of MSVC.
49 */
50 #ifdef _MSC_VER
51 #pragma warning(push)
52 #pragma warning(disable : 4091)
53 #endif
54 #include <dbghelp.h>
55 #ifdef _MSC_VER
56 #pragma warning(pop)
57 #endif
58
59 /*
60 * Much of the following code is based on CodeProject and MSDN examples,
61 * particularly
62 * http://www.codeproject.com/KB/debug/postmortemdebug_standalone1.aspx
63 *
64 * Useful MSDN articles:
65 *
66 * http://msdn.microsoft.com/en-us/library/ff805116(v=VS.85).aspx
67 * http://msdn.microsoft.com/en-us/library/ms679294(VS.85).aspx
68 *
69 * Other useful articles on working with minidumps:
70 * http://www.debuginfo.com/articles/effminidumps.html
71 */
72
73 typedef BOOL (WINAPI * MINIDUMPWRITEDUMP) (HANDLE hProcess, DWORD dwPid, HANDLE hFile, MINIDUMP_TYPE DumpType,
74 CONST PMINIDUMP_EXCEPTION_INFORMATION ExceptionParam,
75 CONST PMINIDUMP_USER_STREAM_INFORMATION UserStreamParam,
76 CONST PMINIDUMP_CALLBACK_INFORMATION CallbackParam
77 );
78
79
80 /*
81 * This function is the exception handler passed to SetUnhandledExceptionFilter.
82 * It's invoked only if there's an unhandled exception. The handler will use
83 * dbghelp.dll to generate a crash dump, then resume the normal unhandled
84 * exception process, which will generally exit with an error message from
85 * the runtime.
86 *
87 * This function is run under the unhandled exception handler, effectively
88 * in a crash context, so it should be careful with memory and avoid using
89 * any PostgreSQL functions.
90 */
91 static LONG WINAPI
crashDumpHandler(struct _EXCEPTION_POINTERS * pExceptionInfo)92 crashDumpHandler(struct _EXCEPTION_POINTERS *pExceptionInfo)
93 {
94 /*
95 * We only write crash dumps if the "crashdumps" directory within the
96 * postgres data directory exists.
97 */
98 DWORD attribs = GetFileAttributesA("crashdumps");
99
100 if (attribs != INVALID_FILE_ATTRIBUTES && (attribs & FILE_ATTRIBUTE_DIRECTORY))
101 {
102 /* 'crashdumps' exists and is a directory. Try to write a dump' */
103 HMODULE hDll = NULL;
104 MINIDUMPWRITEDUMP pDump = NULL;
105 MINIDUMP_TYPE dumpType;
106 char dumpPath[_MAX_PATH];
107 HANDLE selfProcHandle = GetCurrentProcess();
108 DWORD selfPid = GetProcessId(selfProcHandle);
109 HANDLE dumpFile;
110 DWORD systemTicks;
111 struct _MINIDUMP_EXCEPTION_INFORMATION ExInfo;
112
113 ExInfo.ThreadId = GetCurrentThreadId();
114 ExInfo.ExceptionPointers = pExceptionInfo;
115 ExInfo.ClientPointers = FALSE;
116
117 /* Load the dbghelp.dll library and functions */
118 hDll = LoadLibrary("dbghelp.dll");
119 if (hDll == NULL)
120 {
121 write_stderr("could not load dbghelp.dll, cannot write crash dump\n");
122 return EXCEPTION_CONTINUE_SEARCH;
123 }
124
125 pDump = (MINIDUMPWRITEDUMP) (pg_funcptr_t) GetProcAddress(hDll, "MiniDumpWriteDump");
126
127 if (pDump == NULL)
128 {
129 write_stderr("could not load required functions in dbghelp.dll, cannot write crash dump\n");
130 return EXCEPTION_CONTINUE_SEARCH;
131 }
132
133 /*
134 * Dump as much as we can, except shared memory, code segments, and
135 * memory mapped files. Exactly what we can dump depends on the
136 * version of dbghelp.dll, see:
137 * http://msdn.microsoft.com/en-us/library/ms680519(v=VS.85).aspx
138 */
139 dumpType = MiniDumpNormal | MiniDumpWithHandleData |
140 MiniDumpWithDataSegs;
141
142 if (GetProcAddress(hDll, "EnumDirTree") != NULL)
143 {
144 /* If this function exists, we have version 5.2 or newer */
145 dumpType |= MiniDumpWithIndirectlyReferencedMemory |
146 MiniDumpWithPrivateReadWriteMemory;
147 }
148
149 systemTicks = GetTickCount();
150 snprintf(dumpPath, _MAX_PATH,
151 "crashdumps\\postgres-pid%0i-%0i.mdmp",
152 (int) selfPid, (int) systemTicks);
153 dumpPath[_MAX_PATH - 1] = '\0';
154
155 dumpFile = CreateFile(dumpPath, GENERIC_WRITE, FILE_SHARE_WRITE,
156 NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL,
157 NULL);
158 if (dumpFile == INVALID_HANDLE_VALUE)
159 {
160 write_stderr("could not open crash dump file \"%s\" for writing: error code %lu\n",
161 dumpPath, GetLastError());
162 return EXCEPTION_CONTINUE_SEARCH;
163 }
164
165 if ((*pDump) (selfProcHandle, selfPid, dumpFile, dumpType, &ExInfo,
166 NULL, NULL))
167 write_stderr("wrote crash dump to file \"%s\"\n", dumpPath);
168 else
169 write_stderr("could not write crash dump to file \"%s\": error code %lu\n",
170 dumpPath, GetLastError());
171
172 CloseHandle(dumpFile);
173 }
174
175 return EXCEPTION_CONTINUE_SEARCH;
176 }
177
178
179 void
pgwin32_install_crashdump_handler(void)180 pgwin32_install_crashdump_handler(void)
181 {
182 SetUnhandledExceptionFilter(crashDumpHandler);
183 }
184