libposix: complete POSIX_signal_execute

sys/src/lib/posix/signals.c

@@ -0,0 +1,168 @@
+/*
+ * This file is part of Jehanne.
+ *
+ * Copyright (C) 2017 Giacomo Tesio <giacomo@tesio.it>
+ *
+ * This is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3 of the License.
+ *
+ * Jehanne 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 Affero General Public License
+ * along with Jehanne.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <u.h>
+#include <lib9.h>
+#include <posix.h>
+#include "internal.h"
+
+#define __POSIX_SIGNAL_PREFIX_LEN (sizeof(__POSIX_SIGNAL_PREFIX)-1)
+
+static PosixSignalTrampoline __libposix_signal_trampoline;
+
+static int
+note_all_writable_processes(int *errnop, char *note)
+{
+	// TODO: loop over writable note files and post note.
+	*errnop = __libposix_get_errno(PosixEPERM);
+	return -1;
+}
+
+int
+POSIX_kill(int *errnop, int pid, int sig)
+{
+	char msg[64], file[128];
+	int mode;
+	int ret;
+
+	snprint(msg, sizeof(msg), __POSIX_SIGNAL_PREFIX "%d", sig);
+	switch(pid){
+	case 0:
+		mode = PNGROUP;
+		break;
+	case -1:
+		return note_all_writable_processes(errnop, msg);
+	default:
+		if(pid < 0){
+			mode = PNGROUP;
+			pid = -pid;
+		} else {
+			mode = PNPROC;
+		}
+	}
+
+	snprint(file, sizeof(file), "/proc/%d/note", pid);
+	if(access(file, AWRITE) != 0){
+		if(access(file, AEXIST) == 0)
+			*errnop = __libposix_get_errno(PosixEPERM);
+		else
+			*errnop = __libposix_get_errno(PosixESRCH);
+		return -1;
+	}
+	ret = postnote(mode, pid, msg);
+	if(ret != 0){
+		*errnop = __libposix_translate_errstr((uintptr_t)POSIX_kill);
+		return -1;
+	}
+	return 0;
+}
+
+static int
+translate_jehanne_note(char *note)
+{
+	// TODO: implement
+	return 0;
+}
+
+static void
+terminated_by_signal(int sig)
+{
+	char buf[64];
+
+	__libposix_free_wait_list();
+
+	snprint(buf, sizeof(buf), __POSIX_EXIT_SIGNAL_PREFIX "%d", sig);
+	exits(buf);
+}
+
+static int
+send_control_msg(int pid, char *msg)
+{
+	int fd, n;
+	char buf[256];
+
+	n = snprint(buf, sizeof(buf), "/proc/%d/ctl", pid);
+	if(n < 0)
+		goto ErrorBeforeOpen;
+	fd = open(buf, OWRITE);
+	if(fd < 0)
+		goto ErrorBeforeOpen;
+	n = snprint(buf, sizeof(buf), "%s", msg);
+	if(n < 0)
+		goto ErrorAfterOpen;
+	if(write(fd, buf, n) < n)
+		goto ErrorAfterOpen;
+	close(fd);
+	return 1;
+
+ErrorAfterOpen:
+	close(fd);
+ErrorBeforeOpen:
+	return 0;
+}
+
+int
+POSIX_signal_execute(int sig, PosixSignalDisposition action, int pid)
+{
+	switch(action){
+	case SignalHandled:
+		return 1;
+	case TerminateTheProcess:
+	case TerminateTheProcessAndCoreDump:
+		terminated_by_signal(sig);
+		break;
+	case StopTheProcess:
+		if(pid < 0)
+			sysfatal("libposix: signal %d with stop disposition reached process %d", sig, pid);
+		return send_control_msg(pid, "stop");
+	case ResumeTheProcess:
+		if(pid < 0)
+			sysfatal("libposix: signal %d with continue disposition reached process %d", sig, pid);
+		return send_control_msg(pid, "start");
+	}
+	return 0;
+}
+
+int
+__libposix_note_handler(void *ureg, char *note)
+{
+	int sig;
+	PosixSignalDisposition action;
+	if(strncmp(note, __POSIX_SIGNAL_PREFIX, __POSIX_SIGNAL_PREFIX_LEN) != 0)
+		return translate_jehanne_note(note); // TODO: should we translate common notes?
+	sig = atoi(note+__POSIX_SIGNAL_PREFIX_LEN);
+	action = __libposix_signal_trampoline(sig);
+	return POSIX_signal_execute(sig, action, -1);
+}
+
+int
+libposix_set_signal_trampoline(PosixSignalTrampoline trampoline)
+{
+	if(__libposix_initialized())
+		return 0;
+	if(trampoline == nil)
+		return 0;
+	__libposix_signal_trampoline = trampoline;
+	return 1;
+}
+
+void
+__libposix_signal_check_conf(void)
+{
+	if(__libposix_signal_trampoline == nil)
+		sysfatal("libposix: no signal trampoline");
+}