Initial Import

1 files changed, 291 insertions, 0 deletions

diff --git a/events/events_signal.c b/events/events_signal.c
new file mode 100644
index 00000000..652df53d
--- /dev/null
+++ b/events/events_signal.c
@@ -0,0 +1,291 @@
+/* 
+   Unix SMB/CIFS implementation.
+
+   common events code for signal events
+
+   Copyright (C) Andrew Tridgell	2007
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <signal.h>
+#include "replace.h"
+#include "system/filesys.h"
+#include "system/select.h"
+#include "events.h"
+#include "events_internal.h"
+#include "events_util.h"
+
+#define NUM_SIGNALS 64
+
+/* maximum number of SA_SIGINFO signals to hold in the queue */
+#define SA_INFO_QUEUE_COUNT 10
+
+struct sigcounter {
+	uint32_t count;
+	uint32_t seen;
+};
+
+#define SIG_INCREMENT(s) (s).count++
+#define SIG_SEEN(s, n) (s).seen += (n)
+#define SIG_PENDING(s) ((s).seen != (s).count)
+
+
+/*
+  the poor design of signals means that this table must be static global
+*/
+static struct sig_state {
+	struct signal_event *sig_handlers[NUM_SIGNALS+1];
+	struct sigaction *oldact[NUM_SIGNALS+1];
+	struct sigcounter signal_count[NUM_SIGNALS+1];
+	struct sigcounter got_signal;
+	int pipe_hack[2];
+#ifdef SA_SIGINFO
+	/* with SA_SIGINFO we get quite a lot of info per signal */
+	siginfo_t *sig_info[NUM_SIGNALS+1];
+	struct sigcounter sig_blocked[NUM_SIGNALS+1];
+#endif
+} *sig_state;
+
+/*
+  return number of sigcounter events not processed yet
+*/
+static uint32_t sig_count(struct sigcounter s)
+{
+	if (s.count >= s.seen) {
+		return s.count - s.seen;
+	}
+	return 1 + (0xFFFFFFFF & ~(s.seen - s.count));
+}
+
+/*
+  signal handler - redirects to registered signals
+*/
+static void signal_handler(int signum)
+{
+	char c = 0;
+	SIG_INCREMENT(sig_state->signal_count[signum]);
+	SIG_INCREMENT(sig_state->got_signal);
+	/* doesn't matter if this pipe overflows */
+	write(sig_state->pipe_hack[1], &c, 1);
+}
+
+#ifdef SA_SIGINFO
+/*
+  signal handler with SA_SIGINFO - redirects to registered signals
+*/
+static void signal_handler_info(int signum, siginfo_t *info, void *uctx)
+{
+	uint32_t count = sig_count(sig_state->signal_count[signum]);
+	sig_state->sig_info[signum][count] = *info;
+
+	signal_handler(signum);
+
+	/* handle SA_SIGINFO */
+	if (count+1 == SA_INFO_QUEUE_COUNT) {
+		/* we've filled the info array - block this signal until
+		   these ones are delivered */
+		sigset_t set;
+		sigemptyset(&set);
+		sigaddset(&set, signum);
+		sigprocmask(SIG_BLOCK, &set, NULL);
+		SIG_INCREMENT(sig_state->sig_blocked[signum]);
+	}
+}
+#endif
+
+/*
+  destroy a signal event
+*/
+static int signal_event_destructor(struct signal_event *se)
+{
+	se->event_ctx->num_signal_handlers--;
+	DLIST_REMOVE(sig_state->sig_handlers[se->signum], se);
+	if (sig_state->sig_handlers[se->signum] == NULL) {
+		/* restore old handler, if any */
+		sigaction(se->signum, sig_state->oldact[se->signum], NULL);
+		sig_state->oldact[se->signum] = NULL;
+#ifdef SA_SIGINFO
+		if (se->sa_flags & SA_SIGINFO) {
+			talloc_free(sig_state->sig_info[se->signum]);
+			sig_state->sig_info[se->signum] = NULL;
+		}
+#endif
+	}
+	return 0;
+}
+
+/*
+  this is part of the pipe hack needed to avoid the signal race condition
+*/
+static void signal_pipe_handler(struct event_context *ev, struct fd_event *fde, 
+				uint16_t flags, void *private)
+{
+	char c[16];
+	/* its non-blocking, doesn't matter if we read too much */
+	read(sig_state->pipe_hack[0], c, sizeof(c));
+}
+
+/*
+  add a signal event
+  return NULL on failure (memory allocation error)
+*/
+struct signal_event *common_event_add_signal(struct event_context *ev, 
+					     TALLOC_CTX *mem_ctx,
+					     int signum,
+					     int sa_flags,
+					     event_signal_handler_t handler, 
+					     void *private_data) 
+{
+	struct signal_event *se;
+
+	if (signum >= NUM_SIGNALS) {
+		return NULL;
+	}
+
+	/* the sig_state needs to be on a global context as it can last across
+	   multiple event contexts */
+	if (sig_state == NULL) {
+		sig_state = talloc_zero(talloc_autofree_context(), struct sig_state);
+		if (sig_state == NULL) {
+			return NULL;
+		}
+	}
+
+	se = talloc(mem_ctx?mem_ctx:ev, struct signal_event);
+	if (se == NULL) return NULL;
+
+	se->event_ctx		= ev;
+	se->handler		= handler;
+	se->private_data	= private_data;
+	se->signum              = signum;
+	se->sa_flags            = sa_flags;
+	
+	/* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */
+	if (!talloc_reference(se, sig_state)) {
+		return NULL;
+	}
+
+	/* only install a signal handler if not already installed */
+	if (sig_state->sig_handlers[signum] == NULL) {
+		struct sigaction act;
+		ZERO_STRUCT(act);
+		act.sa_handler   = signal_handler;
+		act.sa_flags = sa_flags;
+#ifdef SA_SIGINFO
+		if (sa_flags & SA_SIGINFO) {
+			act.sa_handler   = NULL;
+			act.sa_sigaction = signal_handler_info;
+			if (sig_state->sig_info[signum] == NULL) {
+				sig_state->sig_info[signum] = talloc_array(sig_state, siginfo_t, SA_INFO_QUEUE_COUNT);
+				if (sig_state->sig_info[signum] == NULL) {
+					talloc_free(se);
+					return NULL;
+				}
+			}
+		}
+#endif
+		sig_state->oldact[signum] = talloc(sig_state, struct sigaction);
+		if (sig_state->oldact[signum] == NULL) {
+			talloc_free(se);
+			return NULL;			
+		}
+		if (sigaction(signum, &act, sig_state->oldact[signum]) == -1) {
+			talloc_free(se);
+			return NULL;
+		}
+	}
+
+	DLIST_ADD(sig_state->sig_handlers[signum], se);
+
+	talloc_set_destructor(se, signal_event_destructor);
+
+	/* we need to setup the pipe hack handler if not already
+	   setup */
+	if (ev->pipe_fde == NULL) {
+		if (sig_state->pipe_hack[0] == 0 && 
+		    sig_state->pipe_hack[1] == 0) {
+			pipe(sig_state->pipe_hack);
+			ev_set_blocking(sig_state->pipe_hack[0], false);
+			ev_set_blocking(sig_state->pipe_hack[1], false);
+		}
+		ev->pipe_fde = event_add_fd(ev, ev, sig_state->pipe_hack[0],
+					    EVENT_FD_READ, signal_pipe_handler, NULL);
+	}
+	ev->num_signal_handlers++;
+
+	return se;
+}
+
+
+/*
+  check if a signal is pending
+  return != 0 if a signal was pending
+*/
+int common_event_check_signal(struct event_context *ev)
+{
+	int i;
+
+	if (!sig_state || !SIG_PENDING(sig_state->got_signal)) {
+		return 0;
+	}
+	
+	for (i=0;i<NUM_SIGNALS+1;i++) {
+		struct signal_event *se, *next;
+		struct sigcounter counter = sig_state->signal_count[i];
+		uint32_t count = sig_count(counter);
+
+		if (count == 0) {
+			continue;
+		}
+		for (se=sig_state->sig_handlers[i];se;se=next) {
+			next = se->next;
+#ifdef SA_SIGINFO
+			if (se->sa_flags & SA_SIGINFO) {
+				int j;
+				for (j=0;j<count;j++) {
+					/* note the use of the sig_info array as a
+					   ring buffer */
+					int ofs = ((count-1) + j) % SA_INFO_QUEUE_COUNT;
+					se->handler(ev, se, i, 1, 
+						    (void*)&sig_state->sig_info[i][ofs], 
+						    se->private_data);
+				}
+				if (SIG_PENDING(sig_state->sig_blocked[i])) {
+					/* we'd filled the queue, unblock the
+					   signal now */
+					sigset_t set;
+					sigemptyset(&set);
+					sigaddset(&set, i);
+					SIG_SEEN(sig_state->sig_blocked[i], 
+						 sig_count(sig_state->sig_blocked[i]));
+					sigprocmask(SIG_UNBLOCK, &set, NULL);
+				}
+				if (se->sa_flags & SA_RESETHAND) {
+					talloc_free(se);
+				}
+				continue;
+			}
+#endif
+			se->handler(ev, se, i, count, NULL, se->private_data);
+			if (se->sa_flags & SA_RESETHAND) {
+				talloc_free(se);
+			}
+		}
+		SIG_SEEN(sig_state->signal_count[i], count);
+		SIG_SEEN(sig_state->got_signal, count);
+	}
+
+	return 1;
+}