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/sched_get_priority_min.c

@@ -0,0 +1,53 @@
+/*-*- 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/sched-sysv.internal.h"
+#include "libc/calls/strace.internal.h"
+#include "libc/dce.h"
+#include "libc/intrin/describeflags.internal.h"
+#include "libc/sysv/consts/sched.h"
+#include "libc/sysv/errfuns.h"
+
+static int sys_sched_get_priority_min_netbsd(int policy) {
+  if (policy == SCHED_OTHER) {
+    return -1;
+  } else if (policy == SCHED_RR || policy == SCHED_FIFO) {
+    return 0;  // NetBSD Libc needs 19 system calls to compute this!
+  } else {
+    return einval();
+  }
+}
+
+/**
+ * Returns minimum `sched_param::sched_priority` for `policy`.
+ *
+ * @return priority, or -1 w/ errno
+ * @raise ENOSYS on XNU, Windows, OpenBSD
+ * @raise EINVAL if `policy` is invalid
+ */
+int sched_get_priority_min(int policy) {
+  int rc;
+  if (IsNetbsd()) {
+    rc = sys_sched_get_priority_min_netbsd(policy);
+  } else {
+    rc = sys_sched_get_priority_min(policy);
+  }
+  STRACE("sched_get_priority_min(%s) → %d% m", DescribeSchedPolicy(policy), rc);
+  return rc;
+}