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

libc/calls/clock_getres.c

@@ -0,0 +1,69 @@
+/*-*- 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/asan.internal.h"
+#include "libc/calls/strace.internal.h"
+#include "libc/dce.h"
+#include "libc/intrin/describeflags.internal.h"
+#include "libc/sysv/consts/clock.h"
+#include "libc/sysv/errfuns.h"
+#include "libc/time/time.h"
+
+int sys_clock_getres(int, struct timespec *) hidden;
+
+static int sys_clock_getres_poly(int clock, struct timespec *ts, int64_t real) {
+  if (clock == CLOCK_REALTIME) {
+    ts->tv_sec = 0;
+    ts->tv_nsec = real;
+    return 0;
+  } else if (clock == CLOCK_MONOTONIC) {
+    ts->tv_sec = 0;
+    ts->tv_nsec = 1;
+    return 0;
+  } else {
+    return einval();
+  }
+}
+
+static int sys_clock_getres_nt(int clock, struct timespec *ts) {
+  return sys_clock_getres_poly(clock, ts, 100);
+}
+
+static int sys_clock_getres_xnu(int clock, struct timespec *ts) {
+  return sys_clock_getres_poly(clock, ts, 1000);
+}
+
+/**
+ * Returns granularity of clock.
+ */
+int clock_getres(int clock, struct timespec *ts) {
+  int rc;
+  if (!ts || (IsAsan() && !__asan_is_valid_timespec(ts))) {
+    rc = efault();
+  } else if (clock == 127) {
+    rc = einval();  // 127 is used by consts.sh to mean unsupported
+  } else if (IsWindows()) {
+    rc = sys_clock_getres_nt(clock, ts);
+  } else if (IsXnu()) {
+    rc = sys_clock_getres_xnu(clock, ts);
+  } else {
+    rc = sys_clock_getres(clock, ts);
+  }
+  STRACE("clock_getres(%d, [%s]) → %d% m", clock, DescribeTimespec(rc, ts), rc);
+  return rc;
+}