Пример #1
0
static char *
appendSignalName(char *buf, int signo) {
	switch (signo) {
	case SIGABRT:
		buf = appendText(buf, "SIGABRT");
		break;
	case SIGSEGV:
		buf = appendText(buf, "SIGSEGV");
		break;
	case SIGBUS:
		buf = appendText(buf, "SIGBUS");
		break;
	case SIGFPE:
		buf = appendText(buf, "SIGFPE");
		break;
	case SIGILL:
		buf = appendText(buf, "SIGILL");
		break;
	default:
		return appendULL(buf, (unsigned long long) signo);
	}
	buf = appendText(buf, "(");
	buf = appendULL(buf, (unsigned long long) signo);
	buf = appendText(buf, ")");
	return buf;
}
Пример #2
0
static int
runInSubprocessWithTimeLimit(AbortHandlerState &state, Callback callback, void *userData, int timeLimit) {
	char *end;
	pid_t child;
	int p[2], e;

	if (pipe(p) == -1) {
		e = errno;
		end = state.messageBuf;
		end = appendText(end, "Could not create subprocess: pipe() failed with errno=");
		end = appendULL(end, e);
		end = appendText(end, "\n");
		write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
		return -1;
	}

	child = asyncFork();
	if (child == 0) {
		close(p[0]);
		callback(state, userData);
		_exit(0);
		return -1;

	} else if (child == -1) {
		e = errno;
		close(p[0]);
		close(p[1]);
		end = state.messageBuf;
		end = appendText(end, "Could not create subprocess: fork() failed with errno=");
		end = appendULL(end, e);
		end = appendText(end, "\n");
		write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
		return -1;

	} else {
		int status;
		close(p[1]);

		// We give the child process a time limit. If it doesn't succeed in
		// exiting within the time limit, we assume that it has frozen
		// and we kill it.
		struct pollfd fd;
		fd.fd = p[0];
		fd.events = POLLIN | POLLHUP | POLLERR;
		if (poll(&fd, 1, timeLimit) <= 0) {
			kill(child, SIGKILL);
			safePrintErr("Could not run child process: it did not exit in time\n");
		}
		close(p[0]);
		if (waitpid(child, &status, 0) == child) {
			return status;
		} else {
			return -1;
		}
	}
}
Пример #3
0
static void
dumpFileDescriptorInfoWithLsof(AbortHandlerState &state, void *userData) {
	char *end;

	end = state.messageBuf;
	end = appendULL(end, state.pid);
	*end = '\0';

	closeAllFileDescriptors(2, true);

	execlp("lsof", "lsof", "-p", state.messageBuf, "-nP", (const char * const) 0);

	end = state.messageBuf;
	end = appendText(end, "ERROR: cannot execute command 'lsof': errno=");
	end = appendULL(end, errno);
	end = appendText(end, "\n");
	write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
	_exit(1);
}
Пример #4
0
static void
dumpWithCrashWatch(AbortHandlerState &state) {
	char *messageBuf = state.messageBuf;
	const char *pidStr = messageBuf;
	char *end = messageBuf;
	end = appendULL(end, (unsigned long long) state.pid);
	*end = '\0';
	
	pid_t child = asyncFork();
	if (child == 0) {
		closeAllFileDescriptors(2, true);
		execlp("crash-watch", "crash-watch", "--dump", pidStr, (char * const) 0);
		if (errno == ENOENT) {
			safePrintErr("Crash-watch is not installed. Please install it with 'gem install crash-watch' "
				"or download it from https://github.com/FooBarWidget/crash-watch.\n");
		} else {
			int e = errno;
			end = messageBuf;
			end = appendText(end, "crash-watch is installed, but it could not be executed! ");
			end = appendText(end, "(execlp() returned errno=");
			end = appendULL(end, e);
			end = appendText(end, ") Please check your file permissions or something.\n");
			write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);
		}
		_exit(1);

	} else if (child == -1) {
		int e = errno;
		end = messageBuf;
		end = appendText(end, "Could not execute crash-watch: fork() failed with errno=");
		end = appendULL(end, e);
		end = appendText(end, "\n");
		write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);

	} else {
		waitpid(child, NULL, 0);
	}
}
Пример #5
0
static bool
createCrashLogFile(char *filename, time_t t) {
	char *end = filename;
	end = appendText(end, "/var/tmp/passenger-crash-log.");
	end = appendULL(end, (unsigned long long) t);
	*end = '\0';

	int fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
	if (fd == -1) {
		end = filename;
		end = appendText(end, "/tmp/passenger-crash-log.");
		end = appendULL(end, (unsigned long long) t);
		*end = '\0';
		fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
	}
	if (fd == -1) {
		*filename = '\0';
		return false;
	} else {
		close(fd);
		return true;
	}
}
Пример #6
0
static void
dumpFileDescriptorInfo(AbortHandlerState &state) {
	char *messageBuf = state.messageBuf;
	char *end;
	struct stat buf;
	int status;

	end = messageBuf;
	end = appendText(end, state.messagePrefix);
	end = appendText(end, " ] Open files and file descriptors:\n");
	write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);

	status = runInSubprocessWithTimeLimit(state, dumpFileDescriptorInfoWithLsof, NULL, 4000);

	if (status != 0) {
		safePrintErr("Falling back to another mechanism for dumping file descriptors.\n");

		end = messageBuf;
		end = appendText(end, "/proc/");
		end = appendULL(end, state.pid);
		end = appendText(end, "/fd");
		*end = '\0';
		if (stat(messageBuf, &buf) == 0) {
			dumpFileDescriptorInfoWithLs(state, end + 1);
		} else {
			end = messageBuf;
			end = appendText(end, "/dev/fd");
			*end = '\0';
			if (stat(messageBuf, &buf) == 0) {
				dumpFileDescriptorInfoWithLs(state, end + 1);
			} else {
				end = messageBuf;
				end = appendText(end, "ERROR: No other file descriptor dumping mechanism on current platform detected.\n");
				write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);
			}
		}
	}
}
Пример #7
0
static void
abortHandler(int signo, siginfo_t *info, void *ctx) {
	pid_t pid = getpid();
	char messageBuf[1024];
	#ifdef LIBC_HAS_BACKTRACE_FUNC
		void *backtraceStore[512];
		backtraceStore[0] = '\0'; // Don't let gdb print uninitialized contents.
	#endif
	
	char *end = messageBuf;
	end = appendText(end, "[ pid=");
	end = appendULL(end, (unsigned long long) pid);
	end = appendText(end, ", timestamp=");
	end = appendULL(end, (unsigned long long) time(NULL));
	end = appendText(end, " ] Process aborted! signo=");
	end = appendSignalName(end, signo);
	end = appendText(end, ", reason=");
	end = appendSignalReason(end, info);
	
	// It is important that writing the message and the backtrace are two
	// seperate operations because it's not entirely clear whether the
	// latter is async signal safe and thus can crash.
	#ifdef LIBC_HAS_BACKTRACE_FUNC
		end = appendText(end, ", backtrace available.\n");
	#else
		end = appendText(end, "\n");
	#endif
	write(STDERR_FILENO, messageBuf, end - messageBuf);
	
	#ifdef LIBC_HAS_BACKTRACE_FUNC
		/* For some reason, it would appear that fatal signal
		 * handlers have a deadline on some systems: the process will
		 * be killed if the signal handler doesn't finish in time.
		 * This killing appears to be triggered at some system calls,
		 * including but not limited to nanosleep().
		 * backtrace() might be slow and running crash-watch is
		 * definitely slow, so we do our work in a child process
		 * in order not to be affected by the deadline. But preferably
		 * we don't fork because forking will cause us to lose
		 * thread information.
		 */
		#ifdef __linux__
			bool hasDeadline = false;
		#else
			// Mac OS X has a deadline. Not sure about other systems.
			bool hasDeadline = true;
		#endif
		if (!hasDeadline || fork() == 0) {
			int frames = backtrace(backtraceStore, sizeof(backtraceStore) / sizeof(void *));
			end = messageBuf;
			end = appendText(end, "--------------------------------------\n");
			end = appendText(end, "[ pid=");
			end = appendULL(end, (unsigned long long) pid);
			end = appendText(end, " ] Backtrace with ");
			end = appendULL(end, (unsigned long long) frames);
			end = appendText(end, " frames:\n");
			write(STDERR_FILENO, messageBuf, end - messageBuf);
			backtrace_symbols_fd(backtraceStore, frames, STDERR_FILENO);
			
			end = messageBuf;
			end = appendText(end, "--------------------------------------\n");
			end = appendText(end, "[ pid=");
			end = appendULL(end, (unsigned long long) pid);
			end = appendText(end, " ] Dumping a more detailed backtrace with crash-watch "
				"('gem install crash-watch' if you don't have it)...\n");
			write(STDERR_FILENO, messageBuf, end - messageBuf);
			
			end = messageBuf;
			end = appendText(end, "crash-watch --dump ");
			end = appendULL(end, (unsigned long long) getpid());
			*end = '\0';
			system(messageBuf);
			_exit(1);
		}
	#endif
	
	// Run default signal handler.
	kill(getpid(), signo);
}
Пример #8
0
// Must be async signal safe.
static char *
appendSignalReason(char *buf, siginfo_t *info) {
	bool handled = true;
	
	switch (info->si_code) {
	SI_CODE_HANDLER(SI_USER);
	#ifdef SI_KERNEL
		SI_CODE_HANDLER(SI_KERNEL);
	#endif
	SI_CODE_HANDLER(SI_QUEUE);
	SI_CODE_HANDLER(SI_TIMER);
	#ifdef SI_ASYNCIO
		SI_CODE_HANDLER(SI_ASYNCIO);
	#endif
	#ifdef SI_MESGQ
		SI_CODE_HANDLER(SI_MESGQ);
	#endif
	#ifdef SI_SIGIO
		SI_CODE_HANDLER(SI_SIGIO);
	#endif
	#ifdef SI_TKILL
		SI_CODE_HANDLER(SI_TKILL);
	#endif
	default:
		switch (info->si_signo) {
		case SIGSEGV:
			switch (info->si_code) {
			SI_CODE_HANDLER(SEGV_MAPERR);
			SI_CODE_HANDLER(SEGV_ACCERR);
			default:
				handled = false;
				break;
			}
			break;
		case SIGBUS:
			switch (info->si_code) {
			SI_CODE_HANDLER(BUS_ADRALN);
			SI_CODE_HANDLER(BUS_ADRERR);
			SI_CODE_HANDLER(BUS_OBJERR);
			default:
				handled = false;
				break;
			}
			break;
		};
		if (!handled) {
			buf = appendText(buf, "#");
			buf = appendULL(buf, (unsigned long long) info->si_code);
		}
		break;
	}
	
	if (info->si_code <= 0) {
		buf = appendText(buf, ", signal sent by PID ");
		buf = appendULL(buf, (unsigned long long) info->si_pid);
		buf = appendText(buf, " with UID ");
		buf = appendULL(buf, (unsigned long long) info->si_uid);
	}
	
	return buf;
}
Пример #9
0
static void
abortHandler(int signo, siginfo_t *info, void *ctx) {
	AbortHandlerState state;
	state.pid = getpid();
	state.signo = signo;
	state.info = info;
	pid_t child;
	time_t t = time(NULL);
	char crashLogFile[256];

	abortHandlerCalled++;
	if (abortHandlerCalled > 1) {
		// The abort handler itself crashed!
		char *end = state.messageBuf;
		end = appendText(end, "[ origpid=");
		end = appendULL(end, (unsigned long long) state.pid);
		end = appendText(end, ", pid=");
		end = appendULL(end, (unsigned long long) getpid());
		end = appendText(end, ", timestamp=");
		end = appendULL(end, (unsigned long long) t);
		if (abortHandlerCalled == 2) {
			// This is the first time it crashed.
			end = appendText(end, " ] Abort handler crashed! signo=");
			end = appendSignalName(end, state.signo);
			end = appendText(end, ", reason=");
			end = appendSignalReason(end, state.info);
			end = appendText(end, "\n");
			write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
			// Run default signal handler.
			raise(signo);
		} else {
			// This is the second time it crashed, meaning it failed to
			// invoke the default signal handler to abort the process!
			end = appendText(end, " ] Abort handler crashed again! Force exiting this time. signo=");
			end = appendSignalName(end, state.signo);
			end = appendText(end, ", reason=");
			end = appendSignalReason(end, state.info);
			end = appendText(end, "\n");
			write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
			_exit(1);
		}
		return;
	}

	if (emergencyPipe1[0] != -1) {
		close(emergencyPipe1[0]);
	}
	if (emergencyPipe1[1] != -1) {
		close(emergencyPipe1[1]);
	}
	if (emergencyPipe2[0] != -1) {
		close(emergencyPipe2[0]);
	}
	if (emergencyPipe2[1] != -1) {
		close(emergencyPipe2[1]);
	}
	emergencyPipe1[0] = emergencyPipe1[1] = -1;
	emergencyPipe2[0] = emergencyPipe2[1] = -1;

	/* We want to dump the entire crash log to both stderr and a log file.
	 * We use 'tee' for this.
	 */
	if (createCrashLogFile(crashLogFile, t)) {
		forkAndRedirectToTee(crashLogFile);
	}

	char *end = state.messagePrefix;
	end = appendText(end, "[ pid=");
	end = appendULL(end, (unsigned long long) state.pid);
	*end = '\0';

	end = state.messageBuf;
	end = appendText(end, state.messagePrefix);
	end = appendText(end, ", timestamp=");
	end = appendULL(end, (unsigned long long) t);
	end = appendText(end, " ] Process aborted! signo=");
	end = appendSignalName(end, state.signo);
	end = appendText(end, ", reason=");
	end = appendSignalReason(end, state.info);
	end = appendText(end, ", randomSeed=");
	end = appendULL(end, (unsigned long long) randomSeed);
	end = appendText(end, "\n");
	write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);

	end = state.messageBuf;
	if (*crashLogFile != '\0') {
		end = appendText(end, state.messagePrefix);
		end = appendText(end, " ] Crash log dumped to ");
		end = appendText(end, crashLogFile);
		end = appendText(end, "\n");
	} else {
		end = appendText(end, state.messagePrefix);
		end = appendText(end, " ] Could not create crash log file, so dumping to stderr only.\n");
	}
	write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);

	if (beepOnAbort) {
		end = state.messageBuf;
		end = appendText(end, state.messagePrefix);
		end = appendText(end, " ] PASSENGER_BEEP_ON_ABORT on, executing beep...\n");
		write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);

		child = asyncFork();
		if (child == 0) {
			closeAllFileDescriptors(2, true);
			#ifdef __APPLE__
				execlp("osascript", "osascript", "-e", "beep 2", (const char * const) 0);
				safePrintErr("Cannot execute 'osascript' command\n");
			#else
				execlp("beep", "beep", (const char * const) 0);
				safePrintErr("Cannot execute 'beep' command\n");
			#endif
			_exit(1);

		} else if (child == -1) {
			int e = errno;
			end = state.messageBuf;
			end = appendText(end, state.messagePrefix);
			end = appendText(end, " ] Could fork a child process for invoking a beep: fork() failed with errno=");
			end = appendULL(end, e);
			end = appendText(end, "\n");
			write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
		}
	}

	if (stopOnAbort) {
		end = state.messageBuf;
		end = appendText(end, state.messagePrefix);
		end = appendText(end, " ] PASSENGER_STOP_ON_ABORT on, so process stopped. Send SIGCONT when you want to continue.\n");
		write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
		raise(SIGSTOP);
	}

	// It isn't safe to call any waiting functions in this signal handler,
	// not even read() and waitpid() even though they're async signal safe.
	// So we fork a child process and let it dump as much diagnostics as possible
	// instead of doing it in this process.
	child = asyncFork();
	if (child == 0) {
		// Sleep for a short while to allow the parent process to raise SIGSTOP.
		// usleep() and nanosleep() aren't async signal safe so we use select()
		// instead.
		struct timeval tv;
		tv.tv_sec = 0;
		tv.tv_usec = 100000;
		select(0, NULL, NULL, NULL, &tv);

		resetSignalHandlersAndMask();

		child = asyncFork();
		if (child == 0) {
			// OS X: for some reason the SIGPIPE handler may be reset to default after forking.
			// Later in this program we're going to pipe backtrace_symbols_fd() into the backtrace
			// sanitizer, which may fail, and we don't want the diagnostics process to crash
			// with SIGPIPE as a result, so we ignore SIGPIPE again.
			ignoreSigpipe();
			dumpDiagnostics(state);
			// The child process may or may or may not resume the original process.
			// We do it ourselves just to be sure.
			kill(state.pid, SIGCONT);
			_exit(0);

		} else if (child == -1) {
			int e = errno;
			end = state.messageBuf;
			end = appendText(end, state.messagePrefix);
			end = appendText(end, "] Could fork a child process for dumping diagnostics: fork() failed with errno=");
			end = appendULL(end, e);
			end = appendText(end, "\n");
			write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
			_exit(1);

		} else {
			// Exit immediately so that child process is adopted by init process.
			_exit(0);
		}

	} else if (child == -1) {
		int e = errno;
		end = state.messageBuf;
		end = appendText(end, state.messagePrefix);
		end = appendText(end, " ] Could fork a child process for dumping diagnostics: fork() failed with errno=");
		end = appendULL(end, e);
		end = appendText(end, "\n");
		write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);

	} else {
		raise(SIGSTOP);
		// Will continue after the child process has done its job.
	}

	// Run default signal handler.
	raise(signo);
}
Пример #10
0
// This function is performed in a child process.
static void
dumpDiagnostics(AbortHandlerState &state) {
	char *messageBuf = state.messageBuf;
	char *end;
	pid_t pid;
	int status;

	end = messageBuf;
	end = appendText(end, state.messagePrefix);
	end = appendText(end, " ] Date, uname and ulimits:\n");
	write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);

	// Dump human-readable time string and string.
	pid = asyncFork();
	if (pid == 0) {
		closeAllFileDescriptors(2, true);
		execlp("date", "date", (const char * const) 0);
		_exit(1);
	} else if (pid == -1) {
		safePrintErr("ERROR: Could not fork a process to dump the time!\n");
	} else if (waitpid(pid, &status, 0) != pid || status != 0) {
		safePrintErr("ERROR: Could not run 'date'!\n");
	}

	// Dump system uname.
	pid = asyncFork();
	if (pid == 0) {
		closeAllFileDescriptors(2, true);
		execlp("uname", "uname", "-mprsv", (const char * const) 0);
		_exit(1);
	} else if (pid == -1) {
		safePrintErr("ERROR: Could not fork a process to dump the uname!\n");
	} else if (waitpid(pid, &status, 0) != pid || status != 0) {
		safePrintErr("ERROR: Could not run 'uname -mprsv'!\n");
	}

	// Dump ulimit.
	pid = asyncFork();
	if (pid == 0) {
		closeAllFileDescriptors(2, true);
		execlp("ulimit", "ulimit", "-a", (const char * const) 0);
		// On Linux 'ulimit' is a shell builtin, not a command.
		execlp("/bin/sh", "/bin/sh", "-c", "ulimit -a", (const char * const) 0);
		_exit(1);
	} else if (pid == -1) {
		safePrintErr("ERROR: Could not fork a process to dump the ulimit!\n");
	} else if (waitpid(pid, &status, 0) != pid || status != 0) {
		safePrintErr("ERROR: Could not run 'ulimit -a'!\n");
	}

	end = messageBuf;
	end = appendText(end, state.messagePrefix);
	end = appendText(end, " ] Phusion Passenger version: " PASSENGER_VERSION "\n");
	write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);

	if (lastAssertionFailure.filename != NULL) {
		end = messageBuf;
		end = appendText(end, state.messagePrefix);
		end = appendText(end, " ] Last assertion failure: (");
		end = appendText(end, lastAssertionFailure.expression);
		end = appendText(end, "), ");
		if (lastAssertionFailure.function != NULL) {
			end = appendText(end, "function ");
			end = appendText(end, lastAssertionFailure.function);
			end = appendText(end, ", ");
		}
		end = appendText(end, "file ");
		end = appendText(end, lastAssertionFailure.filename);
		end = appendText(end, ", line ");
		end = appendULL(end, lastAssertionFailure.line);
		end = appendText(end, ".\n");
		write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);
	}

	// It is important that writing the message and the backtrace are two
	// seperate operations because it's not entirely clear whether the
	// latter is async signal safe and thus can crash.
	end = messageBuf;
	end = appendText(end, state.messagePrefix);
	#ifdef LIBC_HAS_BACKTRACE_FUNC
		end = appendText(end, " ] libc backtrace available!\n");
	#else
		end = appendText(end, " ] libc backtrace not available.\n");
	#endif
	write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);

	#ifdef LIBC_HAS_BACKTRACE_FUNC
		runInSubprocessWithTimeLimit(state, dumpBacktrace, NULL, 4000);
	#endif

	safePrintErr("--------------------------------------\n");

	if (customDiagnosticsDumper != NULL) {
		end = messageBuf;
		end = appendText(end, state.messagePrefix);
		end = appendText(end, " ] Dumping additional diagnostical information...\n");
		write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);
		safePrintErr("--------------------------------------\n");
		runInSubprocessWithTimeLimit(state, runCustomDiagnosticsDumper, NULL, 2000);
		safePrintErr("--------------------------------------\n");
	}

	dumpFileDescriptorInfo(state);
	safePrintErr("--------------------------------------\n");

	if (shouldDumpWithCrashWatch) {
		end = messageBuf;
		end = appendText(end, state.messagePrefix);
		#ifdef LIBC_HAS_BACKTRACE_FUNC
			end = appendText(end, " ] Dumping a more detailed backtrace with crash-watch...\n");
		#else
			end = appendText(end, " ] Dumping a backtrace with crash-watch...\n");
		#endif
		write_nowarn(STDERR_FILENO, messageBuf, end - messageBuf);
		dumpWithCrashWatch(state);
	} else {
		write_nowarn(STDERR_FILENO, "\n", 1);
	}
}
Пример #11
0
	static void
	dumpBacktrace(AbortHandlerState &state, void *userData) {
		void *backtraceStore[512];
		int frames = backtrace(backtraceStore, sizeof(backtraceStore) / sizeof(void *));
		char *end = state.messageBuf;
		end = appendText(end, "--------------------------------------\n");
		end = appendText(end, "[ pid=");
		end = appendULL(end, (unsigned long long) state.pid);
		end = appendText(end, " ] Backtrace with ");
		end = appendULL(end, (unsigned long long) frames);
		end = appendText(end, " frames:\n");
		write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);

		if (backtraceSanitizerCommand != NULL) {
			int p[2];
			if (pipe(p) == -1) {
				int e = errno;
				end = state.messageBuf;
				end = appendText(end, "Could not dump diagnostics through backtrace sanitizer: pipe() failed with errno=");
				end = appendULL(end, e);
				end = appendText(end, "\n");
				end = appendText(end, "Falling back to writing to stderr directly...\n");
				write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
				backtrace_symbols_fd(backtraceStore, frames, STDERR_FILENO);
				return;
			}

			pid_t pid = asyncFork();
			if (pid == 0) {
				const char *pidStr = end = state.messageBuf;
				end = appendULL(end, (unsigned long long) state.pid);
				*end = '\0';
				end++;

				close(p[1]);
				dup2(p[0], STDIN_FILENO);
				closeAllFileDescriptors(2, true);
				
				char *command = end;
				end = appendText(end, "exec ");
				end = appendText(end, backtraceSanitizerCommand);
				if (backtraceSanitizerPassProgramInfo) {
					end = appendText(end, " \"");
					end = appendText(end, argv0);
					end = appendText(end, "\" ");
					end = appendText(end, pidStr);
				}
				*end = '\0';
				end++;
				execlp("/bin/sh", "/bin/sh", "-c", command, (const char * const) 0);

				end = state.messageBuf;
				end = appendText(end, "ERROR: cannot execute '");
				end = appendText(end, backtraceSanitizerCommand);
				end = appendText(end, "' for sanitizing the backtrace, trying 'cat'...\n");
				write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
				execlp("cat", "cat", (const char * const) 0);
				execlp("/bin/cat", "cat", (const char * const) 0);
				execlp("/usr/bin/cat", "cat", (const char * const) 0);
				safePrintErr("ERROR: cannot execute 'cat'\n");
				_exit(1);

			} else if (pid == -1) {
				close(p[0]);
				close(p[1]);
				int e = errno;
				end = state.messageBuf;
				end = appendText(end, "Could not dump diagnostics through backtrace sanitizer: fork() failed with errno=");
				end = appendULL(end, e);
				end = appendText(end, "\n");
				end = appendText(end, "Falling back to writing to stderr directly...\n");
				write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
				backtrace_symbols_fd(backtraceStore, frames, STDERR_FILENO);

			} else {
				int status = -1;

				close(p[0]);
				backtrace_symbols_fd(backtraceStore, frames, p[1]);
				close(p[1]);
				if (waitpid(pid, &status, 0) == -1 || status != 0) {
					end = state.messageBuf;
					end = appendText(end, "ERROR: cannot execute '");
					end = appendText(end, backtraceSanitizerCommand);
					end = appendText(end, "' for sanitizing the backtrace, writing to stderr directly...\n");
					write_nowarn(STDERR_FILENO, state.messageBuf, end - state.messageBuf);
					backtrace_symbols_fd(backtraceStore, frames, STDERR_FILENO);
				}
			}

		} else {
			backtrace_symbols_fd(backtraceStore, frames, STDERR_FILENO);
		}
	}