Make improvements

- Clean up sigaction() code
- Add a port scanner example
- Introduce a ParseCidr() API
- Clean up our futex abstraction code
- Fix a harmless integer overflow in ParseIp()
- Use kernel semaphores on NetBSD to make threads much faster

libc/thread/pthread_cancel.c

@@ -51,10 +51,10 @@ int _pthread_cancel_sys(void) {
   return ecanceled();
 }
 
-static void OnSigCancel(int sig, siginfo_t *si, void *ctx) {
+static void OnSigThr(int sig, siginfo_t *si, void *ctx) {
   ucontext_t *uc = ctx;
-  struct CosmoTib *tib = __get_tls();
-  struct PosixThread *pt = (struct PosixThread *)tib->tib_pthread;
+  struct CosmoTib *t = __get_tls();
+  struct PosixThread *pt = (struct PosixThread *)t->tib_pthread;
   if (pt && !(pt->flags & PT_NOCANCEL) &&
       atomic_load_explicit(&pt->cancelled, memory_order_acquire)) {
     sigaddset(&uc->uc_sigmask, sig);
@@ -64,15 +64,14 @@ static void OnSigCancel(int sig, siginfo_t *si, void *ctx) {
     } else if (pt->flags & PT_ASYNC) {
       pthread_exit(PTHREAD_CANCELED);
     } else {
-      __tkill(atomic_load_explicit(&tib->tib_tid, memory_order_relaxed), sig,
-              tib);
+      __tkill(atomic_load_explicit(&t->tib_tid, memory_order_relaxed), sig, t);
     }
   }
 }
 
-static void ListenForSigCancel(void) {
+static void ListenForSigThr(void) {
   struct sigaction sa;
-  sa.sa_sigaction = OnSigCancel;
+  sa.sa_sigaction = OnSigThr;
   sa.sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK;
   memset(&sa.sa_mask, -1, sizeof(sa.sa_mask));
   _npassert(!sigaction(SIGTHR, &sa, 0));
@@ -262,7 +261,7 @@ errno_t pthread_cancel(pthread_t thread) {
   int e, rc, tid;
   static bool once;
   struct PosixThread *pt;
-  if (!once) ListenForSigCancel(), once = true;
+  if (!once) ListenForSigThr(), once = true;
   pt = (struct PosixThread *)thread;
   switch (atomic_load_explicit(&pt->status, memory_order_acquire)) {
     case kPosixThreadZombie:

libc/thread/sem_init.c

@@ -35,13 +35,9 @@
  * @param value is initial count of semaphore
  * @return 0 on success, or -1 w/ errno
  * @raise EINVAL if `value` exceeds `SEM_VALUE_MAX`
- * @raise EPERM on OpenBSD if `pshared` is true
  */
 int sem_init(sem_t *sem, int pshared, unsigned value) {
   if (value > SEM_VALUE_MAX) return einval();
-  // OpenBSD MAP_ANONYMOUS|MAP_SHARED memory is kind of busted.
-  // The OpenBSD implementation of sem_init() also EPERMs here.
-  if (IsOpenbsd() && pshared) return eperm();
   sem->sem_magic = SEM_MAGIC_UNNAMED;
   atomic_store_explicit(&sem->sem_value, value, memory_order_relaxed);
   sem->sem_pshared = !!pshared;

libc/thread/sem_open.c

@@ -209,7 +209,7 @@ sem_t *sem_open(const char *name, int oflag, ...) {
       sem = SEM_FAILED;
     } else if (~oflag & O_EXCL) {
       sem = s->sem;
-      atomic_fetch_add_explicit(&sem->sem_prefs, 1, memory_order_acquire);
+      atomic_fetch_add_explicit(&sem->sem_prefs, 1, memory_order_acq_rel);
       ++s->refs;
     } else {
       eexist();
@@ -218,7 +218,7 @@ sem_t *sem_open(const char *name, int oflag, ...) {
   } else if ((s = calloc(1, sizeof(struct Semaphore)))) {
     if ((s->path = strdup(path))) {
       if ((sem = sem_open_impl(path, oflag, mode, value)) != SEM_FAILED) {
-        atomic_fetch_add_explicit(&sem->sem_prefs, 1, memory_order_relaxed);
+        atomic_fetch_add_explicit(&sem->sem_prefs, 1, memory_order_acq_rel);
         s->next = g_semaphores.list;
         s->sem = sem;
         s->refs = 1;
@@ -260,7 +260,7 @@ int sem_close(sem_t *sem) {
   sem_open_init();
   sem_open_lock();
   _npassert((s = sem_open_get(sem, &p)));
-  prefs = atomic_fetch_add_explicit(&sem->sem_prefs, -1, memory_order_release);
+  prefs = atomic_fetch_add_explicit(&sem->sem_prefs, -1, memory_order_acq_rel);
   _npassert(s->refs > 0);
   if ((unmap = !--s->refs)) {
     _npassert(prefs > 0);

libc/thread/sem_timedwait.c

@@ -33,26 +33,6 @@ static void sem_delay(int n) {
   for (i = 0; i != 1 << n; i++) donothing;
 }
 
-// TODO(jart): This should be abstracted by polyfill.
-static struct timespec *sem_timeout(struct timespec *memory,
-                                    const struct timespec *abstime) {
-  struct timespec now;
-  if (!abstime) {
-    return 0;
-  } else if (FUTEX_TIMEOUT_IS_ABSOLUTE) {
-    *memory = *abstime;
-    return memory;
-  } else {
-    now = timespec_real();
-    if (timespec_cmp(now, *abstime) > 0) {
-      *memory = (struct timespec){0};
-    } else {
-      *memory = timespec_sub(*abstime, now);
-    }
-    return memory;
-  }
-}
-
 static void sem_timedwait_cleanup(void *arg) {
   sem_t *sem = arg;
   _unassert(atomic_fetch_add_explicit(&sem->sem_waiters, -1,
@@ -95,8 +75,7 @@ int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
 
   do {
     if (!(v = atomic_load_explicit(&sem->sem_value, memory_order_relaxed))) {
-      rc = nsync_futex_wait_(&sem->sem_value, v, sem->sem_pshared,
-                             sem_timeout(&ts, abstime));
+      rc = nsync_futex_wait_(&sem->sem_value, v, sem->sem_pshared, abstime);
       if (rc == -EINTR || rc == -ECANCELED) {
         errno = -rc;
         rc = -1;