#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/param.h>
#include <string.h>
#include <errno.h>

#ifdef __linux__
#include <sys/prctl.h>
#ifndef PR_SET_PTRACER
#define PR_SET_PTRACER 0x59616d61
#endif
#elif defined (__APPLE__) || defined (BSD)
#include <signal.h>
#endif

int I_FileAvailable(const char* filename);


static const char crash_switch[] = "--cc-handle-crash";

static const char fatal_err[] = "\n\n*** Fatal Error ***\n";
static const char pipe_err[] = "!!! Failed to create pipe\n";
static const char fork_err[] = "!!! Failed to fork debug process\n";
static const char exec_err[] = "!!! Failed to exec debug process\n";

static char argv0[PATH_MAX];

static char altstack[SIGSTKSZ];


static struct {
	int signum;
	pid_t pid;
	int has_siginfo;
	siginfo_t siginfo;
	char buf[4096];
} crash_info;


static const struct {
	const char *name;
	int signum;
} signals[] = {
	{ "Segmentation fault", SIGSEGV },
	{ "Illegal instruction", SIGILL },
	{ "FPU exception", SIGFPE },
	{ "System BUS error", SIGBUS },
	{ NULL, 0 }
};

static const struct {
	int code;
	const char *name;
} sigill_codes[] = {
#ifndef __FreeBSD__
	{ ILL_ILLOPC, "Illegal opcode" },
	{ ILL_ILLOPN, "Illegal operand" },
	{ ILL_ILLADR, "Illegal addressing mode" },
	{ ILL_ILLTRP, "Illegal trap" },
	{ ILL_PRVOPC, "Privileged opcode" },
	{ ILL_PRVREG, "Privileged register" },
	{ ILL_COPROC, "Coprocessor error" },
	{ ILL_BADSTK, "Internal stack error" },
#endif
	{ 0, NULL }
};

static const struct {
	int code;
	const char *name;
} sigfpe_codes[] = {
	{ FPE_INTDIV, "Integer divide by zero" },
	{ FPE_INTOVF, "Integer overflow" },
	{ FPE_FLTDIV, "Floating point divide by zero" },
	{ FPE_FLTOVF, "Floating point overflow" },
	{ FPE_FLTUND, "Floating point underflow" },
	{ FPE_FLTRES, "Floating point inexact result" },
	{ FPE_FLTINV, "Floating point invalid operation" },
	{ FPE_FLTSUB, "Subscript out of range" },
	{ 0, NULL }
};

static const struct {
	int code;
	const char *name;
} sigsegv_codes[] = {
#ifndef __FreeBSD__
	{ SEGV_MAPERR, "Address not mapped to object" },
	{ SEGV_ACCERR, "Invalid permissions for mapped object" },
#endif
	{ 0, NULL }
};

static const struct {
	int code;
	const char *name;
} sigbus_codes[] = {
#ifndef __FreeBSD__
	{ BUS_ADRALN, "Invalid address alignment" },
	{ BUS_ADRERR, "Non-existent physical address" },
	{ BUS_OBJERR, "Object specific hardware error" },
#endif
	{ 0, NULL }
};

static int (*cc_user_info)(char*, char*);


static void gdb_info(pid_t pid)
{
	char respfile[64];
	char cmd_buf[128];
	FILE *f;
	int fd;

	/* Create a temp file to put gdb commands into */
	strcpy(respfile, "gdb-respfile-XXXXXX");
	if((fd=mkstemp(respfile)) >= 0 && (f=fdopen(fd, "w")) != NULL)
	{
		fprintf(f, "attach %d\n"
		           "shell echo \"\"\n"
		           "shell echo \"* Loaded Libraries\"\n"
		           "info sharedlibrary\n"
		           "shell echo \"\"\n"
		           "shell echo \"* Threads\"\n"
		           "info threads\n"
		           "shell echo \"\"\n"
		           "shell echo \"* FPU Status\"\n"
		           "info float\n"
		           "shell echo \"\"\n"
		           "shell echo \"* Registers\"\n"
		           "info registers\n"
		           "shell echo \"\"\n"
		           "shell echo \"* Backtrace\"\n"
		           "thread apply all backtrace full\n"
		           "detach\n"
		           "quit\n", pid);
		fclose(f);

		/* Run gdb and print process info. */
		snprintf(cmd_buf, sizeof(cmd_buf), "gdb --quiet --batch --command=%s", respfile);
		printf("Executing: %s\n", cmd_buf);
		fflush(stdout);

		system(cmd_buf);
		/* Clean up */
		remove(respfile);
	}
	else
	{
		/* Error creating temp file */
		if(fd >= 0)
		{
			close(fd);
			remove(respfile);
		}
		printf("!!! Could not create gdb command file\n");
	}
	fflush(stdout);
}

static void sys_info(void)
{
#ifdef __unix__
	system("echo \"System: `uname -a`\"");
	putchar('\n');
	fflush(stdout);
#endif
}


static size_t safe_write(int fd, const void *buf, size_t len)
{
	size_t ret = 0;
	while(ret < len)
	{
		ssize_t rem;
		if((rem=write(fd, (const char*)buf+ret, len-ret)) == -1)
		{
			if(errno == EINTR)
				continue;
			break;
		}
		ret += rem;
	}
	return ret;
}

static void crash_catcher(int signum, siginfo_t *siginfo, void *context)
{
	//ucontext_t *ucontext = (ucontext_t*)context;
	pid_t dbg_pid;
	int fd[2];

	/* Make sure the effective uid is the real uid */
	if(getuid() != geteuid())
	{
		raise(signum);
		return;
	}

	safe_write(STDERR_FILENO, fatal_err, sizeof(fatal_err)-1);
	if(pipe(fd) == -1)
	{
		safe_write(STDERR_FILENO, pipe_err, sizeof(pipe_err)-1);
		raise(signum);
		return;
	}

	crash_info.signum = signum;
	crash_info.pid = getpid();
	crash_info.has_siginfo = !!siginfo;
	if(siginfo)
		crash_info.siginfo = *siginfo;
	if(cc_user_info)
		cc_user_info(crash_info.buf, crash_info.buf+sizeof(crash_info.buf));

	/* Fork off to start a crash handler */
	switch((dbg_pid=fork()))
	{
		/* Error */
		case -1:
			safe_write(STDERR_FILENO, fork_err, sizeof(fork_err)-1);
			raise(signum);
			return;

		case 0:
			dup2(fd[0], STDIN_FILENO);
			close(fd[0]);
			close(fd[1]);

			execl(argv0, argv0, crash_switch, NULL);

			safe_write(STDERR_FILENO, exec_err, sizeof(exec_err)-1);
			_exit(1);

		default:
#ifdef __linux__
			prctl(PR_SET_PTRACER, dbg_pid, 0, 0, 0);
#endif
			safe_write(fd[1], &crash_info, sizeof(crash_info));
			close(fd[0]);
			close(fd[1]);

			/* Wait; we'll be killed when gdb is done */
			do {
				int status;
				if(waitpid(dbg_pid, &status, 0) == dbg_pid &&
				   (WIFEXITED(status) || WIFSIGNALED(status)))
				{
					/* The debug process died before it could kill us */
					raise(signum);
					break;
				}
			} while(1);
	}
}

static void crash_handler(const char *logfile)
{
	const char *sigdesc = "";
	int i;

	if(fread(&crash_info, sizeof(crash_info), 1, stdin) != 1)
	{
		fprintf(stderr, "!!! Failed to retrieve info from crashed process\n");
		exit(1);
	}

	/* Get the signal description */
	for(i = 0;signals[i].name;++i)
	{
		if(signals[i].signum == crash_info.signum)
		{
			sigdesc = signals[i].name;
			break;
		}
	}

	if(crash_info.has_siginfo)
	{
		switch(crash_info.signum)
		{
			case SIGSEGV:
				for(i = 0;sigsegv_codes[i].name;++i)
				{
					if(sigsegv_codes[i].code == crash_info.siginfo.si_code)
					{
						sigdesc = sigsegv_codes[i].name;
						break;
					}
				}
				break;

			case SIGFPE:
				for(i = 0;sigfpe_codes[i].name;++i)
				{
					if(sigfpe_codes[i].code == crash_info.siginfo.si_code)
					{
						sigdesc = sigfpe_codes[i].name;
						break;
					}
				}
				break;

			case SIGILL:
				for(i = 0;sigill_codes[i].name;++i)
				{
					if(sigill_codes[i].code == crash_info.siginfo.si_code)
					{
						sigdesc = sigill_codes[i].name;
						break;
					}
				}
				break;

			case SIGBUS:
				for(i = 0;sigbus_codes[i].name;++i)
				{
					if(sigbus_codes[i].code == crash_info.siginfo.si_code)
					{
						sigdesc = sigbus_codes[i].name;
						break;
					}
				}
				break;
		}
	}
	fprintf(stderr, "%s (signal %i)\n", sigdesc, crash_info.signum);
	if(crash_info.has_siginfo)
		fprintf(stderr, "Address: %p\n", crash_info.siginfo.si_addr);
	fputc('\n', stderr);

	if(logfile)
	{
		/* Create crash log file and redirect shell output to it */
		if(freopen(logfile, "wa", stdout) != stdout)
		{
			fprintf(stderr, "!!! Could not create %s following signal\n", logfile);
			exit(1);
		}
		fprintf(stderr, "Generating %s and killing process %d, please wait... ", logfile, crash_info.pid);

		printf("*** Fatal Error ***\n"
		       "%s (signal %i)\n", sigdesc, crash_info.signum);
		if(crash_info.has_siginfo)
			printf("Address: %p\n", crash_info.siginfo.si_addr);
		fputc('\n', stdout);
		fflush(stdout);
	}

	sys_info();

	crash_info.buf[sizeof(crash_info.buf)-1] = '\0';
	printf("%s\n", crash_info.buf);
	fflush(stdout);

	if(crash_info.pid > 0)
	{
		gdb_info(crash_info.pid);
		kill(crash_info.pid, SIGKILL);
	}

	if(logfile)
	{
		char buf[512];

		if(I_FileAvailable("kdialog"))
			snprintf(buf, sizeof(buf), "kdialog --title \"Very Fatal Error\" --textbox \"%s\" 800 600", logfile);
		else if(I_FileAvailable("gxmessage"))
			snprintf(buf, sizeof(buf), "gxmessage -buttons \"Okay:0\" -geometry 800x600 -title \"Very Fatal Error\" -center -file \"%s\"", logfile);
		else
			snprintf(buf, sizeof(buf), "xmessage -buttons \"Okay:0\" -center -file \"%s\"", logfile);

		system(buf);
	}
	exit(0);
}

int cc_install_handlers(int argc, char **argv, int num_signals, int *signals, const char *logfile, int (*user_info)(char*, char*))
{
	struct sigaction sa;
	stack_t altss;
	int retval;

	if(argc == 2 && strcmp(argv[1], crash_switch) == 0)
		crash_handler(logfile);

	cc_user_info = user_info;

	if(argv[0][0] == '/')
		snprintf(argv0, sizeof(argv0), "%s", argv[0]);
	else
	{
		getcwd(argv0, sizeof(argv0));
		retval = strlen(argv0);
		snprintf(argv0+retval, sizeof(argv0)-retval, "/%s", argv[0]);
	}

	/* Set an alternate signal stack so SIGSEGVs caused by stack overflows
	 * still run */
	altss.ss_sp = altstack;
	altss.ss_flags = 0;
	altss.ss_size = sizeof(altstack);
	sigaltstack(&altss, NULL);

	memset(&sa, 0, sizeof(sa));
	sa.sa_sigaction = crash_catcher;
	sa.sa_flags = SA_RESETHAND | SA_NODEFER | SA_SIGINFO | SA_ONSTACK;
	sigemptyset(&sa.sa_mask);

	retval = 0;
	while(num_signals--)
	{
		if((*signals != SIGSEGV && *signals != SIGILL && *signals != SIGFPE &&
		    *signals != SIGBUS) || sigaction(*signals, &sa, NULL) == -1)
		{
			*signals = 0;
			retval = -1;
		}
		++signals;
	}
	return retval;
}