/* Copyright (c) 2001-2009 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "ioloop.h"
#include "fd-close-on-exec.h"
#include "lib-signals.h"

#include <signal.h>
#include <unistd.h>

#define MAX_SIGNAL_VALUE 31

struct signal_handler {
	signal_handler_t *handler;
	void *context;

	bool delayed;
        struct signal_handler *next;
};

/* Remember that these are accessed inside signal handler which may be called
   even while we're initializing/deinitializing. Try hard to keep everything
   in consistent state. */
static struct signal_handler *signal_handlers[MAX_SIGNAL_VALUE+1] = { NULL, };
static int sig_pipe_fd[2] = { -1, -1 };

static bool signals_initialized = FALSE;
static struct io *io_sig = NULL;

static siginfo_t pending_signals[MAX_SIGNAL_VALUE+1];
static bool have_pending_signals = FALSE;

const char *lib_signal_code_to_str(int signo, int sicode)
{
	/* common */
	switch (sicode) {
	case SI_USER:
		return "kill";
#ifdef SI_KERNEL
	case SI_KERNEL:
		return "kernel";
#endif
	case SI_TIMER:
		return "timer";
	}

	/* If SEGV_MAPERR is supported, the rest of them must be too.
	   FreeBSD 6 at least doesn't support these. */
#ifdef SEGV_MAPERR
	switch (signo) {
	case SIGSEGV:
		switch (sicode) {
		case SEGV_MAPERR:
			return "address not mapped";
		case SEGV_ACCERR:
			return "invalid permissions";
		}
		break;
	case SIGBUS:
		switch (sicode) {
		case BUS_ADRALN:
			return "invalid address alignment";
		case BUS_ADRERR:
			return "nonexistent physical address";
		case BUS_OBJERR:
			return "object-specific hardware error";
		}
	}
#endif
	return t_strdup_printf("unknown %d", sicode);
}

static void sig_handler(int signo, siginfo_t *si, void *context ATTR_UNUSED)
{
	struct signal_handler *h;
	char c = 0;

	if (signo < 0 || signo > MAX_SIGNAL_VALUE)
		return;

	/* remember that we're inside a signal handler which might have been
	   called at any time. don't do anything that's unsafe. */
	for (h = signal_handlers[signo]; h != NULL; h = h->next) {
		if (!h->delayed)
			h->handler(si, h->context);
		else if (pending_signals[signo].si_signo == 0) {
			pending_signals[signo] = *si;
			if (!have_pending_signals) {
				int saved_errno = errno;

				if (write(sig_pipe_fd[1], &c, 1) != 1)
					i_error("write(sigpipe) failed: %m");
				have_pending_signals = TRUE;
				errno = saved_errno;
			}
		}
	}
}

static void sig_ignore(int signo ATTR_UNUSED, siginfo_t *si ATTR_UNUSED,
		       void *context ATTR_UNUSED)
{
	/* if we used SIG_IGN instead of this function,
	   the system call might be restarted */
}

static void signal_read(void *context ATTR_UNUSED)
{
	siginfo_t signals[MAX_SIGNAL_VALUE+1];
	sigset_t fullset, oldset;
	struct signal_handler *h;
	char buf[2];
	int signo;
	ssize_t ret;

	if (sigfillset(&fullset) < 0)
		i_fatal("sigfillset() failed: %m");
	if (sigprocmask(SIG_BLOCK, &fullset, &oldset) < 0)
		i_fatal("sigprocmask() failed: %m");

	ret = read(sig_pipe_fd[0], buf, sizeof(buf));
	i_assert(ret <= 1);
	if (ret > 0) {
		memcpy(signals, pending_signals, sizeof(signals));
		memset(pending_signals, 0, sizeof(pending_signals));
		have_pending_signals = FALSE;
	} else if (ret < 0) {
		if (errno != EAGAIN)
			i_fatal("read(sigpipe) failed: %m");
	} else {
		i_fatal("read(sigpipe) failed: EOF");
	}
	if (sigprocmask(SIG_SETMASK, &oldset, NULL) < 0)
		i_fatal("sigprocmask() failed: %m");

	if (ret < 0)
		return;

	/* call the delayed handlers after signals are copied and unblocked */
	for (signo = 0; signo < MAX_SIGNAL_VALUE; signo++) {
		if (signals[signo].si_signo == 0)
			continue;

		for (h = signal_handlers[signo]; h != NULL; h = h->next) {
			if (h->delayed)
				h->handler(&signals[signo], h->context);
		}
	}
}

static void lib_signals_set(int signo, bool ignore)
{
	struct sigaction act;

	if (sigemptyset(&act.sa_mask) < 0)
		i_fatal("sigemptyset(): %m");
	act.sa_flags = SA_SIGINFO;
	act.sa_sigaction = ignore ? sig_ignore : sig_handler;
	if (sigaction(signo, &act, NULL) < 0)
		i_fatal("sigaction(%d): %m", signo);
}

void lib_signals_set_handler(int signo, bool delayed,
			     signal_handler_t *handler, void *context)
{
	struct signal_handler *h;

	i_assert(handler != NULL);

	if (signo < 0 || signo > MAX_SIGNAL_VALUE) {
		i_panic("Trying to set signal %d handler, but max is %d",
			signo, MAX_SIGNAL_VALUE);
	}

	if (signal_handlers[signo] == NULL && signals_initialized)
		lib_signals_set(signo, FALSE);

	if (delayed && sig_pipe_fd[0] == -1) {
		/* first delayed handler */
		if (pipe(sig_pipe_fd) < 0)
			i_fatal("pipe() failed: %m");
		fd_close_on_exec(sig_pipe_fd[0], TRUE);
		fd_close_on_exec(sig_pipe_fd[1], TRUE);
		if (signals_initialized) {
			io_sig = io_add(sig_pipe_fd[0], IO_READ,
					signal_read, NULL);
		}
	}

	h = i_new(struct signal_handler, 1);
	h->handler = handler;
	h->context = context;
	h->delayed = delayed;

	/* atomically set to signal_handlers[] list */
	h->next = signal_handlers[signo];
	signal_handlers[signo] = h;
}

void lib_signals_ignore(int signo, bool restart_syscalls)
{
	struct sigaction act;

	if (signo < 0 || signo > MAX_SIGNAL_VALUE) {
		i_panic("Trying to ignore signal %d, but max is %d",
			signo, MAX_SIGNAL_VALUE);
	}

	i_assert(signal_handlers[signo] == NULL);

	if (sigemptyset(&act.sa_mask) < 0)
		i_fatal("sigemptyset(): %m");
	if (restart_syscalls) {
		act.sa_flags = SA_RESTART;
		act.sa_handler = SIG_IGN;
	} else {
		act.sa_flags = SA_SIGINFO;
		act.sa_sigaction = sig_ignore;
	}

	if (sigaction(signo, &act, NULL) < 0)
		i_fatal("sigaction(%d): %m", signo);
}

void lib_signals_unset_handler(int signo, signal_handler_t *handler,
			       void *context)
{
	struct signal_handler *h, **p;

	for (p = &signal_handlers[signo]; *p != NULL; p = &(*p)->next) {
		if ((*p)->handler == handler && (*p)->context == context) {
			h = *p;
			*p = h->next;
			i_free(h);
			return;
		}
	}

	i_panic("lib_signals_unset_handler(%d, %p, %p): handler not found",
		signo, (void *)handler, context);
}

void lib_signals_reset_ioloop(void)
{
	if (io_sig != NULL) {
		io_remove(&io_sig);
		io_sig = io_add(sig_pipe_fd[0], IO_READ, signal_read, NULL);
	}
}

void lib_signals_init(void)
{
	int i;

	signals_initialized = TRUE;

	/* add signals that were already registered */
	for (i = 0; i < MAX_SIGNAL_VALUE; i++) {
		if (signal_handlers[i] != NULL)
			lib_signals_set(i, FALSE);
	}

	if (sig_pipe_fd[0] != -1)
		io_sig = io_add(sig_pipe_fd[0], IO_READ, signal_read, NULL);
}

void lib_signals_deinit(void)
{
	struct signal_handler *handlers, *h;
	int i;

	for (i = 0; i < MAX_SIGNAL_VALUE; i++) {
		if (signal_handlers[i] != NULL) {
			/* atomically remove from signal_handlers[] list */
			handlers = signal_handlers[i];
			signal_handlers[i] = NULL;

			while (handlers != NULL) {
				h = handlers;
				handlers = h->next;
				i_free(h);
			}
		}
	}

	if (io_sig != NULL)
		io_remove(&io_sig);
	if (sig_pipe_fd[0] != -1) {
		if (close(sig_pipe_fd[0]) < 0)
			i_error("close(sigpipe) failed: %m");
		if (close(sig_pipe_fd[1]) < 0)
			i_error("close(sigpipe) failed: %m");
	}
}