Support for collecting crash dumps on Windows

Add support for collecting "minidump" style crash dumps on
Windows, by setting up an exception handling filter. Crash
dumps will be generated in PGDATA/crashdumps if the directory
is created (the existance of the directory is used as on/off
switch for the generation of the dumps).

Craig Ringer and Magnus Hagander

2 files changed, 175 insertions, 1 deletions

diff --git a/src/backend/port/win32/Makefile b/src/backend/port/win32/Makefile
index 8bf9f74bc4..d00c33421e 100644
--- a/src/backend/port/win32/Makefile
+++ b/src/backend/port/win32/Makefile
@@ -12,6 +12,6 @@ subdir = src/backend/port/win32
 top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
-OBJS = timer.o socket.o signal.o security.o mingwcompat.o
+OBJS = timer.o socket.o signal.o security.o mingwcompat.o crashdump.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/port/win32/crashdump.c b/src/backend/port/win32/crashdump.c
new file mode 100644
index 0000000000..ba6fca7563
--- /dev/null
+++ b/src/backend/port/win32/crashdump.c
@@ -0,0 +1,174 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32_crashdump.c
+ *         Automatic crash dump creation for PostgreSQL on Windows
+ *
+ * The crashdump feature traps unhandled win32 exceptions produced by the
+ * backend, and tries to produce a Windows MiniDump crash
+ * dump for later debugging and analysis. The machine performing the dump
+ * doesn't need any special debugging tools; the user only needs to send
+ * the dump to somebody who has the same version of PostgreSQL and has debugging
+ * tools.
+ *
+ * crashdump module originally by Craig Ringer <ringerc@ringerc.id.au>
+ *
+ * LIMITATIONS
+ * ===========
+ * This *won't* work in hard OOM situations or stack overflows.
+ *
+ * For those, it'd be necessary to take a much more complicated approach where
+ * the handler switches to a new stack (if it can) and forks a helper process
+ * to debug it self.
+ *
+ * POSSIBLE FUTURE WORK
+ * ====================
+ * For bonus points, the crash dump format permits embedding of user-supplied
+ * data. If there's anything else that should always be supplied with a crash
+ * dump (postgresql.conf? Last few lines of a log file?), it could potentially
+ * be added, though at the cost of a greater chance of the crash dump failing.
+ *
+ *
+ * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/port/win32/crashdump.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <string.h>
+#include <dbghelp.h>
+
+/*
+ * Much of the following code is based on CodeProject and MSDN examples,
+ * particularly
+ * http://www.codeproject.com/KB/debug/postmortemdebug_standalone1.aspx
+ *
+ * Useful MSDN articles:
+ *
+ * http://msdn.microsoft.com/en-us/library/ff805116(v=VS.85).aspx
+ * http://msdn.microsoft.com/en-us/library/ms679294(VS.85).aspx
+ *
+ * Other useful articles on working with minidumps:
+ * http://www.debuginfo.com/articles/effminidumps.html
+ */
+
+typedef BOOL (WINAPI *MINIDUMPWRITEDUMP)(HANDLE hProcess, DWORD dwPid, HANDLE hFile, MINIDUMP_TYPE DumpType,
+									CONST PMINIDUMP_EXCEPTION_INFORMATION ExceptionParam,
+									CONST PMINIDUMP_USER_STREAM_INFORMATION UserStreamParam,
+									CONST PMINIDUMP_CALLBACK_INFORMATION CallbackParam
+									);
+
+
+/*
+ * This function is the exception handler passed to SetUnhandledExceptionFilter.
+ * It's invoked only if there's an unhandled exception. The handler will use
+ * dbghelp.dll to generate a crash dump, then resume the normal unhandled
+ * exception process, which will generally exit with an error message from
+ * the runtime.
+ *
+ * This function is run under the unhandled exception handler, effectively
+ * in a crash context, so it should be careful with memory and avoid using
+ * any PostgreSQL functions.
+ */
+static LONG WINAPI
+crashDumpHandler(struct _EXCEPTION_POINTERS *pExceptionInfo)
+{
+	/*
+	 * We only write crash dumps if the "crashdumps" directory within
+	 * the postgres data directory exists.
+	 */
+	DWORD attribs = GetFileAttributesA("crashdumps");
+	if (attribs != INVALID_FILE_ATTRIBUTES && (attribs & FILE_ATTRIBUTE_DIRECTORY) )
+	{
+		/* 'crashdumps' exists and is a directory. Try to write a dump' */
+		HMODULE hDll = NULL;
+		MINIDUMPWRITEDUMP pDump = NULL;
+		MINIDUMP_TYPE dumpType;
+		char dumpPath[_MAX_PATH];
+		HANDLE selfProcHandle = GetCurrentProcess();
+		DWORD selfPid = GetProcessId(selfProcHandle);
+		HANDLE dumpFile;
+		DWORD systemTicks;
+		struct _MINIDUMP_EXCEPTION_INFORMATION ExInfo;
+
+		ExInfo.ThreadId = GetCurrentThreadId();
+		ExInfo.ExceptionPointers = pExceptionInfo;
+		ExInfo.ClientPointers = FALSE;
+
+		/* Load the dbghelp.dll library and functions */
+		hDll = LoadLibrary("dbghelp.dll");
+		if (hDll == NULL)
+		{
+			write_stderr("could not load dbghelp.dll, cannot write crashdump\n");
+			return EXCEPTION_CONTINUE_SEARCH;
+		}
+
+		pDump = (MINIDUMPWRITEDUMP)GetProcAddress(hDll, "MiniDumpWriteDump");
+
+		if (pDump==NULL)
+		{
+			write_stderr("could not load required functions in dbghelp.dll, cannot write crashdump\n");
+			return EXCEPTION_CONTINUE_SEARCH;
+		}
+
+		/*
+		 * Dump as much as we can, except shared memory, code segments,
+		 * and memory mapped files.
+		 * Exactly what we can dump depends on the version of dbghelp.dll,
+		 * see:
+		 * http://msdn.microsoft.com/en-us/library/ms680519(v=VS.85).aspx
+		 */
+		dumpType = MiniDumpNormal | MiniDumpWithHandleData |
+			MiniDumpWithDataSegs;
+
+		if (GetProcAddress(hDll, "EnumDirTree") != NULL)
+		{
+			/* If this function exists, we have version 5.2 or newer */
+			dumpType |= MiniDumpWithIndirectlyReferencedMemory |
+				MiniDumpWithPrivateReadWriteMemory;
+		}
+		if (GetProcAddress(hDll, "SymFromIndex") != NULL)
+		{
+			/* If this function exists, we have version 6.2 or newer */
+			dumpType |= MiniDumpWithThreadInfo;
+		}
+
+		systemTicks = GetTickCount();
+		snprintf(dumpPath, _MAX_PATH,
+				 "crashdumps\\postgres-pid%0i-%0i.mdmp", selfPid, systemTicks);
+		dumpPath[_MAX_PATH-1] = '\0';
+
+		dumpFile = CreateFile(dumpPath, GENERIC_WRITE, FILE_SHARE_WRITE,
+							  NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL,
+							  NULL);
+		if (dumpFile==INVALID_HANDLE_VALUE)
+		{
+			write_stderr("could not open crash dump file %s for writing: error code %d\n",
+					dumpPath, GetLastError());
+			return EXCEPTION_CONTINUE_SEARCH;
+		}
+
+		if ((*pDump)(selfProcHandle, selfPid, dumpFile, dumpType, &ExInfo,
+					 NULL, NULL))
+			write_stderr("wrote crash dump to %s\n", dumpPath);
+		else
+			write_stderr("could not write crash dump to %s: error code %08x\n",
+					dumpPath, GetLastError());
+
+		CloseHandle(dumpFile);
+	}
+
+	return EXCEPTION_CONTINUE_SEARCH;
+}
+
+
+void
+pgwin32_install_crashdump_handler(void)
+{
+	SetUnhandledExceptionFilter(crashDumpHandler);
+}