1 files changed, 359 insertions, 0 deletions
diff --git a/lib/sigevent.c b/lib/sigevent.c
new file mode 100644
index 0000000..3cd65eb
--- /dev/null
+++ b/lib/sigevent.c
@@ -0,0 +1,359 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Quagga signal handling functions.
+ * Copyright (C) 2004 Paul Jakma,
+ */
+
+#include <zebra.h>
+#include <sigevent.h>
+#include <log.h>
+#include <memory.h>
+#include <lib_errors.h>
+
+#ifdef HAVE_UCONTEXT_H
+#ifdef GNU_LINUX
+/* get REG_EIP from ucontext.h */
+#ifndef __USE_GNU
+#define __USE_GNU
+#endif /* __USE_GNU */
+#endif /* GNU_LINUX */
+#include <ucontext.h>
+#endif /* HAVE_UCONTEXT_H */
+
+
+/* master signals descriptor struct */
+static struct frr_sigevent_master_t {
+	struct event *t;
+
+	struct frr_signal_t *signals;
+	int sigc;
+
+	volatile sig_atomic_t caught;
+} sigmaster;
+
+/* Generic signal handler
+ * Schedules signal event thread
+ */
+static void frr_signal_handler(int signo)
+{
+	int i;
+	struct frr_signal_t *sig;
+
+	for (i = 0; i < sigmaster.sigc; i++) {
+		sig = &(sigmaster.signals[i]);
+
+		if (sig->signal == signo)
+			sig->caught = 1;
+	}
+
+	sigmaster.caught = 1;
+}
+
+/*
+ * Check whether any signals have been received and are pending. This is done
+ * with the application's key signals blocked. The complete set of signals
+ * is returned in 'setp', so the caller can restore them when appropriate.
+ * If there are pending signals, returns 'true', 'false' otherwise.
+ */
+bool frr_sigevent_check(sigset_t *setp)
+{
+	sigset_t blocked;
+	int i;
+	bool ret;
+
+	sigemptyset(setp);
+	sigemptyset(&blocked);
+
+	/* Set up mask of application's signals */
+	for (i = 0; i < sigmaster.sigc; i++)
+		sigaddset(&blocked, sigmaster.signals[i].signal);
+
+	pthread_sigmask(SIG_BLOCK, &blocked, setp);
+
+	/* Now that the application's signals are blocked, test. */
+	ret = (sigmaster.caught != 0);
+
+	return ret;
+}
+
+/* check if signals have been caught and run appropriate handlers */
+int frr_sigevent_process(void)
+{
+	struct frr_signal_t *sig;
+	int i;
+#ifdef SIGEVENT_BLOCK_SIGNALS
+	/* shouldn't need to block signals, but potentially may be needed */
+	sigset_t newmask, oldmask;
+
+	/*
+	 * Block most signals, but be careful not to defer SIGTRAP because
+	 * doing so breaks gdb, at least on NetBSD 2.0.  Avoid asking to
+	 * block SIGKILL, just because we shouldn't be able to do so.
+	 */
+	sigfillset(&newmask);
+	sigdelset(&newmask, SIGTRAP);
+	sigdelset(&newmask, SIGKILL);
+
+	if ((sigprocmask(SIG_BLOCK, &newmask, &oldmask)) < 0) {
+		flog_err_sys(EC_LIB_SYSTEM_CALL,
+			     "frr_signal_timer: couldnt block signals!");
+		return -1;
+	}
+#endif /* SIGEVENT_BLOCK_SIGNALS */
+
+	if (sigmaster.caught > 0) {
+		sigmaster.caught = 0;
+		/* must not read or set sigmaster.caught after here,
+		 * race condition with per-sig caught flags if one does
+		 */
+
+		for (i = 0; i < sigmaster.sigc; i++) {
+			sig = &(sigmaster.signals[i]);
+
+			if (sig->caught > 0) {
+				sig->caught = 0;
+				if (sig->handler)
+					sig->handler();
+			}
+		}
+	}
+
+#ifdef SIGEVENT_BLOCK_SIGNALS
+	if (sigprocmask(SIG_UNBLOCK, &oldmask, NULL) < 0)
+		return -1;
+#endif /* SIGEVENT_BLOCK_SIGNALS */
+
+	return 0;
+}
+
+#ifdef SIGEVENT_SCHEDULE_THREAD
+/* timer thread to check signals. shouldn't be needed */
+void frr_signal_timer(struct event *t)
+{
+	struct frr_sigevent_master_t *sigm;
+
+	sigm = EVENT_ARG(t);
+	sigm->t = NULL;
+	event_add_timer(sigm->t->master, frr_signal_timer, &sigmaster,
+			FRR_SIGNAL_TIMER_INTERVAL, &sigm->t);
+	frr_sigevent_process();
+}
+#endif /* SIGEVENT_SCHEDULE_THREAD */
+
+/* Initialization of signal handles. */
+/* Signal wrapper. */
+static int signal_set(int signo)
+{
+	int ret;
+	struct sigaction sig;
+	struct sigaction osig;
+
+	sig.sa_handler = &frr_signal_handler;
+	sigfillset(&sig.sa_mask);
+	sig.sa_flags = 0;
+	if (signo == SIGALRM) {
+#ifdef SA_INTERRUPT
+		sig.sa_flags |= SA_INTERRUPT; /* SunOS */
+#endif
+	} else {
+#ifdef SA_RESTART
+		sig.sa_flags |= SA_RESTART;
+#endif /* SA_RESTART */
+	}
+
+	ret = sigaction(signo, &sig, &osig);
+	if (ret < 0)
+		return ret;
+	else
+		return 0;
+}
+
+/* XXX This function should be enhanced to support more platforms
+       (it currently works only on Linux/x86). */
+static void *program_counter(void *context)
+{
+#ifdef HAVE_UCONTEXT_H
+#ifdef GNU_LINUX
+/* these are from GNU libc, rather than Linux, strictly speaking */
+#if defined(REG_EIP)
+#  define REG_INDEX REG_EIP
+#elif defined(REG_RIP)
+#  define REG_INDEX REG_RIP
+#elif defined(__powerpc__)
+#  define REG_INDEX 32
+#endif
+#endif		       /* GNU_LINUX */
+
+#ifdef REG_INDEX
+#ifdef HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS
+#  define REGS gregs[REG_INDEX]
+#elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_UC_REGS)
+#  define REGS uc_regs->gregs[REG_INDEX]
+#endif /* HAVE_UCONTEXT_T_UC_MCONTEXT_GREGS */
+#endif /* REG_INDEX */
+
+#ifdef REGS
+	if (context)
+		return (void *)(((ucontext_t *)context)->uc_mcontext.REGS);
+#elif defined(HAVE_UCONTEXT_T_UC_MCONTEXT_REGS__NIP)
+	/* older Linux / struct pt_regs ? */
+	if (context)
+		return (void *)(((ucontext_t *)context)->uc_mcontext.regs->nip);
+#endif /* REGS */
+
+#endif /* HAVE_UCONTEXT_H */
+	return NULL;
+}
+
+static void __attribute__((noreturn))
+exit_handler(int signo, siginfo_t *siginfo, void *context)
+{
+	void *pc = program_counter(context);
+
+	zlog_signal(signo, "exiting...", siginfo, pc);
+	_exit(128 + signo);
+}
+
+static void __attribute__((noreturn))
+core_handler(int signo, siginfo_t *siginfo, void *context)
+{
+	void *pc = program_counter(context);
+
+	/* make sure we don't hang in here.  default for SIGALRM is terminate.
+	 * - if we're in backtrace for more than a second, abort. */
+	struct sigaction sa_default = {.sa_handler = SIG_DFL};
+
+	sigaction(SIGALRM, &sa_default, NULL);
+	sigaction(signo, &sa_default, NULL);
+
+	sigset_t sigset;
+
+	sigemptyset(&sigset);
+	sigaddset(&sigset, SIGALRM);
+	sigprocmask(SIG_UNBLOCK, &sigset, NULL);
+
+	alarm(1);
+
+	zlog_signal(signo, "aborting...", siginfo, pc);
+
+	/* dump memory stats on core */
+	log_memstats(stderr, "core_handler");
+
+	zlog_tls_buffer_fini();
+
+	/* give the kernel a chance to generate a coredump */
+	sigaddset(&sigset, signo);
+	sigprocmask(SIG_UNBLOCK, &sigset, NULL);
+	raise(signo);
+
+	/* only chance to end up here is if the default action for signo is
+	 * something other than kill or coredump the process
+	 */
+	_exit(128 + signo);
+}
+
+static void trap_default_signals(void)
+{
+	static const int core_signals[] = {
+		SIGQUIT, SIGILL, SIGABRT,
+#ifdef SIGEMT
+		SIGEMT,
+#endif
+		SIGFPE,  SIGBUS, SIGSEGV,
+#ifdef SIGSYS
+		SIGSYS,
+#endif
+#ifdef SIGXCPU
+		SIGXCPU,
+#endif
+#ifdef SIGXFSZ
+		SIGXFSZ,
+#endif
+	};
+	static const int exit_signals[] = {
+		SIGHUP,    SIGINT, SIGALRM, SIGTERM, SIGUSR1, SIGUSR2,
+#ifdef SIGPOLL
+		SIGPOLL,
+#endif
+#ifdef SIGVTALRM
+		SIGVTALRM,
+#endif
+#ifdef SIGSTKFLT
+		SIGSTKFLT,
+#endif
+	};
+	static const int ignore_signals[] = {
+		SIGPIPE,
+	};
+	static const struct {
+		const int *sigs;
+		unsigned int nsigs;
+		void (*handler)(int signo, siginfo_t *info, void *context);
+	} sigmap[] = {
+		{core_signals, array_size(core_signals), core_handler},
+		{exit_signals, array_size(exit_signals), exit_handler},
+		{ignore_signals, array_size(ignore_signals), NULL},
+	};
+	unsigned int i;
+
+	for (i = 0; i < array_size(sigmap); i++) {
+		unsigned int j;
+
+		for (j = 0; j < sigmap[i].nsigs; j++) {
+			struct sigaction oact;
+			if ((sigaction(sigmap[i].sigs[j], NULL, &oact) == 0)
+			    && (oact.sa_handler == SIG_DFL)) {
+				struct sigaction act;
+				sigfillset(&act.sa_mask);
+				if (sigmap[i].handler == NULL) {
+					act.sa_handler = SIG_IGN;
+					act.sa_flags = 0;
+				} else {
+					/* Request extra arguments to signal
+					 * handler. */
+					act.sa_sigaction = sigmap[i].handler;
+					act.sa_flags = SA_SIGINFO;
+#ifdef SA_RESETHAND
+					/* don't try to print backtraces
+					 * recursively */
+					if (sigmap[i].handler == core_handler)
+						act.sa_flags |= SA_RESETHAND;
+#endif
+				}
+				if (sigaction(sigmap[i].sigs[j], &act, NULL)
+				    < 0)
+					flog_err(
+						EC_LIB_SYSTEM_CALL,
+						"Unable to set signal handler for signal %d: %s",
+						sigmap[i].sigs[j],
+						safe_strerror(errno));
+			}
+		}
+	}
+}
+
+void signal_init(struct event_loop *m, int sigc, struct frr_signal_t signals[])
+{
+
+	int i = 0;
+	struct frr_signal_t *sig;
+
+	/* First establish some default handlers that can be overridden by
+	   the application. */
+	trap_default_signals();
+
+	while (i < sigc) {
+		sig = &signals[i];
+		if (signal_set(sig->signal) < 0)
+			exit(-1);
+		i++;
+	}
+
+	sigmaster.sigc = sigc;
+	sigmaster.signals = signals;
+
+#ifdef SIGEVENT_SCHEDULE_THREAD
+	sigmaster.t = NULL;
+	event_add_timer(m, frr_signal_timer, &sigmaster,
+			FRR_SIGNAL_TIMER_INTERVAL, &sigmaster.t);
+#endif /* SIGEVENT_SCHEDULE_THREAD */
+}