Make improvements

- You can now run `make -j8 toolchain` on Windows
- You can now run `make -j` on MacOS ARM64 and BSD OSes
- You can now use our Emacs dev environment on MacOS/Windows
- Fix bug where the x16 register was being corrupted by --ftrace
- The programs under build/bootstrap/ are updated as fat binaries
- The Makefile now explains how to download cosmocc-0.0.12 toolchain
- The build scripts under bin/ now support "cosmo" branded toolchains
- stat() now goes faster on Windows (shaves 100ms off `make` latency)
- Code cleanup and added review on the Windows signal checking code
- posix_spawnattr_setrlimit() now works around MacOS ARM64 bugs
- Landlock Make now favors posix_spawn() on non-Linux/OpenBSD
- posix_spawn() now has better --strace logging on Windows
- fstatat() can now avoid EACCES in more cases on Windows
- fchmod() can now change the readonly bit on Windows

libc/calls/getrandom-metal.c

@@ -0,0 +1,94 @@
+/*-*- 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 2023 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/intrin/asmflag.h"
+#include "libc/nexgen32e/x86feature.h"
+#include "libc/sysv/consts/grnd.h"
+#include "libc/sysv/errfuns.h"
+#ifdef __x86_64__
+
+static bool GetRandomRdseed(uint64_t *out) {
+  int i;
+  char cf;
+  uint64_t x;
+  for (i = 0; i < 10; ++i) {
+    asm volatile(CFLAG_ASM("rdseed\t%1")
+                 : CFLAG_CONSTRAINT(cf), "=r"(x)
+                 : /* no inputs */
+                 : "cc");
+    if (cf) {
+      *out = x;
+      return true;
+    }
+    asm volatile("pause");
+  }
+  return false;
+}
+
+static bool GetRandomRdrand(uint64_t *out) {
+  int i;
+  char cf;
+  uint64_t x;
+  for (i = 0; i < 10; ++i) {
+    asm volatile(CFLAG_ASM("rdrand\t%1")
+                 : CFLAG_CONSTRAINT(cf), "=r"(x)
+                 : /* no inputs */
+                 : "cc");
+    if (cf) {
+      *out = x;
+      return true;
+    }
+    asm volatile("pause");
+  }
+  return false;
+}
+
+static ssize_t GetRandomCpu(char *p, size_t n, int f, bool impl(uint64_t *)) {
+  uint64_t x;
+  size_t i, j;
+  for (i = 0; i < n; i += j) {
+  TryAgain:
+    if (!impl(&x)) {
+      if (f || i >= 256) break;
+      goto TryAgain;
+    }
+    for (j = 0; j < 8 && i + j < n; ++j) {
+      p[i + j] = x;
+      x >>= 8;
+    }
+  }
+  return n;
+}
+
+ssize_t sys_getrandom_metal(char *p, size_t n, int f) {
+  if (f & GRND_RANDOM) {
+    if (X86_HAVE(RDSEED)) {
+      return GetRandomCpu(p, n, f, GetRandomRdseed);
+    } else {
+      return enosys();
+    }
+  } else {
+    if (X86_HAVE(RDRND)) {
+      return GetRandomCpu(p, n, f, GetRandomRdrand);
+    } else {
+      return enosys();
+    }
+  }
+}
+
+#endif /* __x86_64__ */