Improve system calls

- Wrap clock_getres()
- Wrap sched_setscheduler()
- Make sleep() api conformant
- Polyfill sleep() using select()
- Improve clock_gettime() polyfill
- Make nanosleep() POSIX conformant
- Slightly improve some DNS functions
- Further strengthen pledge() sandboxing
- Improve rounding of timeval / timespec
- Allow layering of pledge() calls on Linux
- Polyfill sched_yield() using select() on XNU
- Delete more system constants we probably don't need

test/libc/calls/nanosleep_test.c

@@ -0,0 +1,64 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/calls/struct/itimerval.h"
+#include "libc/calls/struct/sigaction.h"
+#include "libc/calls/struct/timespec.h"
+#include "libc/intrin/describeflags.internal.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/sysv/consts/itimer.h"
+#include "libc/sysv/consts/sa.h"
+#include "libc/sysv/consts/sig.h"
+#include "libc/testlib/testlib.h"
+#include "libc/time/time.h"
+
+void OnAlrm(int sig) {
+  // do nothing
+}
+
+TEST(nanosleep, testFault) {
+  EXPECT_SYS(EFAULT, -1, nanosleep(0, 0));
+}
+
+TEST(nanosleep, testInvalid) {
+  struct timespec ts = {0, -1};
+  EXPECT_SYS(EINVAL, -1, nanosleep(&ts, 0));
+}
+
+TEST(nanosleep, testNoSignalIsDelivered_remIsSetToZero) {
+  struct timespec ts = {0, 1};
+  ASSERT_SYS(0, 0, nanosleep(&ts, &ts));
+  EXPECT_EQ(0, ts.tv_sec);
+  EXPECT_EQ(0, ts.tv_nsec);
+}
+
+TEST(nanosleep, testInterrupt_remIsUpdated) {
+  struct sigaction sa = {
+      .sa_handler = OnAlrm,
+      .sa_flags = SA_RESETHAND,
+  };
+  ASSERT_SYS(0, 0, sigaction(SIGALRM, &sa, 0));
+  struct itimerval it = {{0, 0}, {0, 10000}};  // 10ms singleshot
+  ASSERT_SYS(0, 0, setitimer(ITIMER_REAL, &it, 0));
+  struct timespec ts = {500, 0};
+  ASSERT_SYS(EINTR, -1, nanosleep(&ts, &ts));
+  ASSERT_LT(ts.tv_sec, 500);
+  ASSERT_GT(ts.tv_sec, 400);
+  ASSERT_NE(0, ts.tv_nsec);
+}