Rewrite special file handling on Windows

This change gets GNU grep working. What caused it to not work, is it wouldn't write to an output file descriptor when its dev/ino equaled /dev/null's. So now we invent special dev/ino values for these files
2025-06-26 22:38:30 +00:00 · 2023-10-14 01:06:00 -07:00 · 2023-10-14 01:06:00 -07:00 · 2db2f40a98
commit 2db2f40a98
parent aca2261cda
53 changed files with 485 additions and 299 deletions
--- a/libc/calls/abort.c
+++ b/libc/calls/abort.c
@ -33,9 +33,7 @@
 * @noreturn
 */
 wontreturn void abort(void) {
-  sigset_t m;
-  sigemptyset(&m);
-  sigaddset(&m, SIGABRT);
+  sigset_t m = 1ull << (SIGABRT - 1);
  sigprocmask(SIG_UNBLOCK, &m, 0);
  raise(SIGABRT);
  signal(SIGABRT, SIG_DFL);
--- a/libc/calls/fcntl-nt.c
+++ b/libc/calls/fcntl-nt.c
@ -321,63 +321,18 @@ static textwindows int sys_fcntl_nt_dupfd(int fd, int cmd, int start) {
  return sys_dup_nt(fd, -1, (cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0), start);
 }

-static textwindows int sys_fcntl_nt_setfl(int fd, unsigned *flags,
-                                          unsigned mode, unsigned arg,
-                                          intptr_t *handle) {
-
-  // you may change the following:
-  //
-  // - O_NONBLOCK     make read() raise EAGAIN
-  // - O_APPEND       for toggling append mode
-  // - O_RANDOM       alt. for posix_fadvise()
-  // - O_SEQUENTIAL   alt. for posix_fadvise()
-  // - O_DIRECT       works but haven't tested
-  //
-  // the other bits are ignored.
-  unsigned allowed = O_APPEND | O_SEQUENTIAL | O_RANDOM | O_DIRECT | O_NONBLOCK;
-  unsigned needreo = O_APPEND | O_SEQUENTIAL | O_RANDOM | O_DIRECT;
-  unsigned newflag = (*flags & ~allowed) | (arg & allowed);
-
-  if ((*flags & needreo) ^ (arg & needreo)) {
-    unsigned perm, share, attr;
-    if (GetNtOpenFlags(newflag, mode, &perm, &share, 0, &attr) == -1) {
-      return -1;
-    }
-    // MSDN says only these are allowed, otherwise it returns EINVAL.
-    attr &= kNtFileFlagBackupSemantics | kNtFileFlagDeleteOnClose |
-            kNtFileFlagNoBuffering | kNtFileFlagOpenNoRecall |
-            kNtFileFlagOpenReparsePoint | kNtFileFlagOverlapped |
-            kNtFileFlagPosixSemantics | kNtFileFlagRandomAccess |
-            kNtFileFlagSequentialScan | kNtFileFlagWriteThrough;
-    intptr_t hand;
-    if ((hand = ReOpenFile(*handle, perm, share, attr)) != -1) {
-      if (hand != *handle) {
-        CloseHandle(*handle);
-        *handle = hand;
-      }
-    } else {
-      return __winerr();
-    }
-  }
-
-  // 1. ignore flags that aren't access mode flags
-  // 2. return zero if nothing's changed
-  *flags = newflag;
-  return 0;
-}
-
 textwindows int sys_fcntl_nt(int fd, int cmd, uintptr_t arg) {
  int rc;
  BLOCK_SIGNALS;
-  if (__isfdkind(fd, kFdFile) ||    //
-      __isfdkind(fd, kFdSocket) ||  //
-      __isfdkind(fd, kFdConsole)) {
+  if (__isfdkind(fd, kFdFile) ||     //
+      __isfdkind(fd, kFdSocket) ||   //
+      __isfdkind(fd, kFdConsole) ||  //
+      __isfdkind(fd, kFdDevNull)) {
    if (cmd == F_GETFL) {
      rc = g_fds.p[fd].flags & (O_ACCMODE | O_APPEND | O_DIRECT | O_NONBLOCK |
                                O_RANDOM | O_SEQUENTIAL);
    } else if (cmd == F_SETFL) {
-      rc = sys_fcntl_nt_setfl(fd, &g_fds.p[fd].flags, g_fds.p[fd].mode, arg,
-                              &g_fds.p[fd].handle);
+      rc = sys_fcntl_nt_setfl(fd, arg);
    } else if (cmd == F_GETFD) {
      if (g_fds.p[fd].flags & O_CLOEXEC) {
        rc = FD_CLOEXEC;
--- a/libc/calls/fstat-nt.c
+++ b/libc/calls/fstat-nt.c
@ -19,7 +19,9 @@
 #include "libc/assert.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/struct/fd.internal.h"
 #include "libc/calls/struct/stat.h"
+#include "libc/calls/struct/stat.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/fmt/wintime.internal.h"
 #include "libc/intrin/atomic.h"
@ -76,13 +78,47 @@ static textwindows long GetSizeOfReparsePoint(int64_t fh) {
  return z;
 }

-textwindows int sys_fstat_nt(int64_t handle, struct stat *out_st) {
+static textwindows int sys_fstat_nt_socket(int kind, struct stat *st) {
+  bzero(st, sizeof(*st));
+  st->st_blksize = 512;
+  st->st_mode = S_IFSOCK | 0666;
+  st->st_dev = 0x44444444;
+  st->st_ino = kind;
+  return 0;
+}
+
+textwindows int sys_fstat_nt_special(int kind, struct stat *st) {
+  bzero(st, sizeof(*st));
+  st->st_blksize = 512;
+  st->st_mode = S_IFCHR | 0666;
+  st->st_dev = 0x77777777;
+  st->st_ino = kind;
+  return 0;
+}
+
+textwindows int sys_fstat_nt(int fd, struct stat *st) {
+  if (fd + 0u >= g_fds.n) return ebadf();
+  switch (g_fds.p[fd].kind) {
+    case kFdEmpty:
+      return ebadf();
+    case kFdConsole:
+    case kFdDevNull:
+      return sys_fstat_nt_special(g_fds.p[fd].kind, st);
+    case kFdSocket:
+      return sys_fstat_nt_socket(g_fds.p[fd].kind, st);
+    default:
+      return sys_fstat_nt_handle(g_fds.p[fd].handle, st);
+  }
+}
+
+textwindows int sys_fstat_nt_handle(int64_t handle, struct stat *out_st) {
  struct stat st = {0};

  // Always set st_blksize to avoid divide by zero issues.
  // The Linux kernel sets this for /dev/tty and similar too.
  // TODO(jart): GetVolumeInformationByHandle?
  st.st_blksize = 4096;
+  st.st_gid = st.st_uid = sys_getuid_nt();

  // We'll use the "umask" to fake out the mode bits.
  uint32_t umask = atomic_load_explicit(&__umask, memory_order_acquire);
@ -92,9 +128,13 @@ textwindows int sys_fstat_nt(int64_t handle, struct stat *out_st) {
      break;
    case kNtFileTypeChar:
      st.st_mode = S_IFCHR | (0666 & ~umask);
+      st.st_dev = 0x66666666;
+      st.st_ino = handle;
      break;
    case kNtFileTypePipe:
      st.st_mode = S_IFIFO | (0666 & ~umask);
+      st.st_dev = 0x55555555;
+      st.st_ino = handle;
      break;
    case kNtFileTypeDisk: {
      struct NtByHandleFileInformation wst;
@ -126,7 +166,6 @@ textwindows int sys_fstat_nt(int64_t handle, struct stat *out_st) {
      } else {
        st.st_ctim = st.st_mtim;
      }
-      st.st_gid = st.st_uid = sys_getuid_nt();
      st.st_size = (wst.nFileSizeHigh + 0ull) << 32 | wst.nFileSizeLow;
      st.st_dev = wst.dwVolumeSerialNumber;
      st.st_ino = (wst.nFileIndexHigh + 0ull) << 32 | wst.nFileIndexLow;
--- a/libc/calls/fstat.c
+++ b/libc/calls/fstat.c
@ -52,7 +52,7 @@ int fstat(int fd, struct stat *st) {
  } else if (IsMetal()) {
    rc = sys_fstat_metal(fd, st);
  } else if (IsWindows()) {
-    rc = sys_fstat_nt(__getfdhandleactual(fd), st);
+    rc = sys_fstat_nt(fd, st);
  } else {
    rc = enosys();
  }
--- a/libc/calls/fstatat-nt.c
+++ b/libc/calls/fstatat-nt.c
@ -16,9 +16,8 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/calls/sig.internal.h"
+#include "libc/calls/struct/fd.internal.h"
 #include "libc/calls/struct/sigset.internal.h"
-#include "libc/calls/struct/stat.h"
 #include "libc/calls/struct/stat.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/errno.h"
@ -29,18 +28,43 @@
 #include "libc/nt/enum/filesharemode.h"
 #include "libc/nt/errors.h"
 #include "libc/nt/runtime.h"
+#include "libc/str/str.h"
 #include "libc/sysv/consts/at.h"
+#include "libc/sysv/consts/fileno.h"
+#include "libc/sysv/errfuns.h"

 textwindows int sys_fstatat_nt(int dirfd, const char *path, struct stat *st,
                               int flags) {
-  int rc, e;
-  int64_t fh;
-  uint32_t dwDesiredAccess;
+
+  // handle special files
+  if (startswith(path, "/dev/")) {
+    if (!strcmp(path + 5, "tty")) {
+      return sys_fstat_nt_special(kFdConsole, st);
+    } else if (!strcmp(path + 5, "null")) {
+      return sys_fstat_nt_special(kFdDevNull, st);
+    } else if (!strcmp(path + 5, "stdin")) {
+      return sys_fstat_nt(STDIN_FILENO, st);
+    } else if (!strcmp(path + 5, "stdout")) {
+      return sys_fstat_nt(STDOUT_FILENO, st);
+    } else if (!strcmp(path + 5, "stderr")) {
+      return sys_fstat_nt(STDERR_FILENO, st);
+    } else {
+      return enoent();
+    }
+  }
+
+  // convert path from utf-8 to utf-16
  uint16_t path16[PATH_MAX];
-  if (__mkntpathat(dirfd, path, 0, path16) == -1) return -1;
+  if (__mkntpathat(dirfd, path, 0, path16) == -1) {
+    return -1;
+  }
+
+  // open an actual file
+  int rc;
+  int64_t fh;
+  int e = errno;
+  uint32_t dwDesiredAccess = kNtFileGenericRead;
  BLOCK_SIGNALS;
-  e = errno;
-  dwDesiredAccess = kNtFileGenericRead;
 TryAgain:
  if ((fh = CreateFile(
           path16, dwDesiredAccess,
@ -50,7 +74,7 @@ TryAgain:
               ((flags & AT_SYMLINK_NOFOLLOW) ? kNtFileFlagOpenReparsePoint
                                              : 0),
           0)) != -1) {
-    rc = st ? sys_fstat_nt(fh, st) : 0;
+    rc = st ? sys_fstat_nt_handle(fh, st) : 0;
    CloseHandle(fh);
  } else if (dwDesiredAccess == kNtFileGenericRead &&
             GetLastError() == kNtErrorSharingViolation) {
@ -61,5 +85,7 @@ TryAgain:
    rc = __winerr();
  }
  ALLOW_SIGNALS;
+
+  // mop up errors
  return __fix_enotdir(rc, path16);
 }
--- a/libc/calls/getloadavg-nt.c
+++ b/libc/calls/getloadavg-nt.c
@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
+#include "libc/calls/struct/sigset.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/dce.h"
 #include "libc/fmt/conv.h"
@ -36,6 +37,7 @@ textwindows int sys_getloadavg_nt(double *a, int n) {
  int i, rc;
  uint64_t elapsed, used;
  struct NtFileTime idle, kern, user;
+  BLOCK_SIGNALS;
  pthread_spin_lock(&lock);
  if (GetSystemTimes(&idle, &kern, &user)) {
    elapsed = (FT(kern) - FT(kern1)) + (FT(user) - FT(user1));
@ -53,6 +55,7 @@ textwindows int sys_getloadavg_nt(double *a, int n) {
    rc = __winerr();
  }
  pthread_spin_unlock(&lock);
+  ALLOW_SIGNALS;
  return rc;
 }

--- a/libc/calls/getuid-nt.c
+++ b/libc/calls/getuid-nt.c
@ -20,15 +20,7 @@
 #include "libc/intrin/atomic.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/accounting.h"
-
-static textwindows uint32_t __kmp32(const void *buf, size_t size) {
-  size_t i;
-  uint32_t h;
-  const uint32_t kPhiPrime = 0x9e3779b1;
-  const unsigned char *p = (const unsigned char *)buf;
-  for (h = i = 0; i < size; i++) h = (p[i] + h) * kPhiPrime;
-  return h;
-}
+#include "libc/str/str.h"

 textwindows uint32_t sys_getuid_nt(void) {
  char16_t buf[257];
@ -36,7 +28,7 @@ textwindows uint32_t sys_getuid_nt(void) {
  uint32_t tmp, size = ARRAYLEN(buf);
  if (!(tmp = atomic_load_explicit(&uid, memory_order_acquire))) {
    GetUserName(&buf, &size);
-    tmp = __kmp32(buf, size >> 1) & 32767;
+    tmp = __fnv(buf, size >> 1) & 32767;
    if (!tmp) ++tmp;
    atomic_store_explicit(&uid, tmp, memory_order_release);
  }
--- a/libc/calls/ioctl.c
+++ b/libc/calls/ioctl.c
@ -106,6 +106,9 @@ static int ioctl_fionread(int fd, uint32_t *arg) {
      int bytes = CountConsoleInputBytes();
      *arg = MAX(0, bytes);
      return 0;
+    } else if (g_fds.p[fd].kind == kFdDevNull) {
+      *arg = 1;
+      return 0;
    } else if (GetFileType(handle) == kNtFileTypePipe) {
      uint32_t avail;
      if (PeekNamedPipe(handle, 0, 0, 0, &avail, 0)) {
--- a/libc/calls/ischardev.c
+++ b/libc/calls/ischardev.c
@ -54,7 +54,7 @@ bool32 ischardev(int fd) {
      return false;
    }
  } else {
-    return __isfdkind(fd, kFdConsole) ||
+    return __isfdkind(fd, kFdConsole) || __isfdkind(fd, kFdDevNull) ||
           (__isfdkind(fd, kFdFile) &&
            GetFileType(__getfdhandleactual(fd)) == kNtFileTypeChar);
  }
--- a/libc/calls/lseek-nt.c
+++ b/libc/calls/lseek-nt.c
@ -62,7 +62,9 @@ static textwindows int64_t Seek(struct Fd *f, int64_t offset, int whence) {
 }

 textwindows int64_t sys_lseek_nt(int fd, int64_t offset, int whence) {
-  if (__isfdkind(fd, kFdFile)) {
+  if (__isfdkind(fd, kFdDevNull)) {
+    return offset;
+  } else if (__isfdkind(fd, kFdFile)) {
    struct Fd *f = g_fds.p + fd;
    int filetype = GetFileType(f->handle);
    if (filetype != kNtFileTypePipe && filetype != kNtFileTypeChar) {
--- a/libc/calls/mkntpath.c
+++ b/libc/calls/mkntpath.c
@ -16,7 +16,6 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/calls/ntmagicpaths.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
@ -36,24 +35,6 @@ static inline int IsAlpha(int c) {
  return ('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z');
 }

-textwindows static const char *FixNtMagicPath(const char *path,
-                                              unsigned flags) {
-  const struct NtMagicPaths *mp = &kNtMagicPaths;
-  asm("" : "+r"(mp));
-  if (!IsSlash(path[0])) return path;
-  if (strcmp(path, mp->devtty) == 0) {
-    if ((flags & O_ACCMODE) == O_RDONLY) {
-      return mp->conin;
-    } else if ((flags & O_ACCMODE) == O_WRONLY) {
-      return mp->conout;
-    }
-  }
-  if (strcmp(path, mp->devnull) == 0) return mp->nul;
-  if (strcmp(path, mp->devstdin) == 0) return mp->conin;
-  if (strcmp(path, mp->devstdout) == 0) return mp->conout;
-  return path;
-}
-
 textwindows size_t __normntpath(char16_t *p, size_t n) {
  size_t i, j;
  for (j = i = 0; i < n; ++i) {
@ -116,7 +97,6 @@ textwindows int __mkntpath2(const char *path,
  if (!path || (IsAsan() && !__asan_is_valid_str(path))) {
    return efault();
  }
-  path = FixNtMagicPath(path, flags);

  size_t x, z;
  char16_t *p = path16;
--- a/libc/calls/ntmagicpaths.c
+++ b/libc/calls/ntmagicpaths.c
@ -1,25 +0,0 @@
-/*-*- 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 2020 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/ntmagicpaths.internal.h"
-
-const struct NtMagicPaths kNtMagicPaths = {
-#define TAB(NAME, STRING) STRING,
-#include "libc/calls/ntmagicpaths.inc"
-#undef TAB
-};
--- a/libc/calls/ntmagicpaths.inc
+++ b/libc/calls/ntmagicpaths.inc
@ -1,7 +0,0 @@
-TAB(devtty, "/dev/tty")
-TAB(devnull, "/dev/null")
-TAB(devstdin, "/dev/stdin")
-TAB(devstdout, "/dev/stdout")
-TAB(nul, "NUL")
-TAB(conin, "CONIN$")
-TAB(conout, "CONOUT$")
--- a/libc/calls/ntmagicpaths.internal.h
+++ b/libc/calls/ntmagicpaths.internal.h
@ -1,16 +0,0 @@
-#ifndef COSMOPOLITAN_LIBC_CALLS_NTMAGICPATHS_H_
-#define COSMOPOLITAN_LIBC_CALLS_NTMAGICPATHS_H_
-#if !(__ASSEMBLER__ + __LINKER__ + 0)
-COSMOPOLITAN_C_START_
-
-struct NtMagicPaths {
-#define TAB(NAME, STRING) char NAME[sizeof(STRING)];
-#include "libc/calls/ntmagicpaths.inc"
-#undef TAB
-};
-
-extern const struct NtMagicPaths kNtMagicPaths;
-
-COSMOPOLITAN_C_END_
-#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
-#endif /* COSMOPOLITAN_LIBC_CALLS_NTMAGICPATHS_H_ */
--- a/libc/calls/open-nt.c
+++ b/libc/calls/open-nt.c
@ -18,8 +18,8 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
 #include "libc/calls/internal.h"
-#include "libc/calls/ntmagicpaths.internal.h"
 #include "libc/calls/state.internal.h"
+#include "libc/calls/struct/sigset.internal.h"
 #include "libc/calls/syscall-nt.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/errno.h"
@ -131,24 +131,13 @@ static textwindows int64_t sys_open_nt_impl(int dirfd, const char *path,
  return __fix_enotdir(hand, path16);
 }

-static textwindows int sys_open_nt_console(int dirfd,
-                                           const struct NtMagicPaths *mp,
-                                           uint32_t flags, int32_t mode,
-                                           size_t fd) {
-  g_fds.p[fd].kind = kFdConsole;
-  g_fds.p[fd].flags = flags;
-  g_fds.p[fd].mode = mode;
-  g_fds.p[fd].handle =
-      CreateFile(u"CONIN$", kNtGenericRead | kNtGenericWrite, kNtFileShareRead,
-                 &kNtIsInheritable, kNtOpenExisting, 0, 0);
-  return fd;
-}
-
 static textwindows int sys_open_nt_file(int dirfd, const char *file,
                                        uint32_t flags, int32_t mode,
                                        size_t fd) {
-  if ((g_fds.p[fd].handle = sys_open_nt_impl(dirfd, file, flags, mode,
-                                             kNtFileFlagOverlapped)) != -1) {
+  int64_t handle;
+  if ((handle = sys_open_nt_impl(dirfd, file, flags, mode,
+                                 kNtFileFlagOverlapped)) != -1) {
+    g_fds.p[fd].handle = handle;
    g_fds.p[fd].kind = kFdFile;
    g_fds.p[fd].flags = flags;
    g_fds.p[fd].mode = mode;
@ -158,15 +147,61 @@ static textwindows int sys_open_nt_file(int dirfd, const char *file,
  }
 }

+static textwindows int sys_open_nt_special(int fd, int flags, int mode,
+                                           int kind, const char16_t *name) {
+  g_fds.p[fd].kind = kind;
+  g_fds.p[fd].mode = mode;
+  g_fds.p[fd].flags = flags;
+  g_fds.p[fd].handle = CreateFile(name, kNtGenericRead | kNtGenericWrite,
+                                  kNtFileShareRead | kNtFileShareWrite,
+                                  &kNtIsInheritable, kNtOpenExisting, 0, 0);
+  return fd;
+}
+
+static textwindows int sys_open_nt_dup(int fd, int flags, int mode, int oldfd) {
+  int64_t handle;
+  if (!__isfdopen(oldfd)) {
+    return enoent();
+  }
+  if (DuplicateHandle(GetCurrentProcess(), g_fds.p[oldfd].handle,
+                      GetCurrentProcess(), &handle, 0, true,
+                      kNtDuplicateSameAccess)) {
+    g_fds.p[fd] = g_fds.p[oldfd];
+    g_fds.p[fd].handle = handle;
+    g_fds.p[fd].mode = mode;
+    if (!sys_fcntl_nt_setfl(fd, flags)) {
+      return fd;
+    } else {
+      CloseHandle(handle);
+      return -1;
+    }
+  } else {
+    return __winerr();
+  }
+}
+
 textwindows int sys_open_nt(int dirfd, const char *file, uint32_t flags,
                            int32_t mode) {
  int fd;
  ssize_t rc;
+  BLOCK_SIGNALS;
  __fds_lock();
  if (!(flags & O_CREAT)) mode = 0;
  if ((rc = fd = __reservefd_unlocked(-1)) != -1) {
-    if (!strcmp(file, kNtMagicPaths.devtty)) {
-      rc = sys_open_nt_console(dirfd, &kNtMagicPaths, flags, mode, fd);
+    if (startswith(file, "/dev/")) {
+      if (!strcmp(file + 5, "tty")) {
+        rc = sys_open_nt_special(fd, flags, mode, kFdConsole, u"CONIN$");
+      } else if (!strcmp(file + 5, "null")) {
+        rc = sys_open_nt_special(fd, flags, mode, kFdDevNull, u"NUL");
+      } else if (!strcmp(file + 5, "stdin")) {
+        rc = sys_open_nt_dup(fd, flags, mode, STDIN_FILENO);
+      } else if (!strcmp(file + 5, "stdout")) {
+        rc = sys_open_nt_dup(fd, flags, mode, STDOUT_FILENO);
+      } else if (!strcmp(file + 5, "stderr")) {
+        rc = sys_open_nt_dup(fd, flags, mode, STDERR_FILENO);
+      } else {
+        rc = enoent();
+      }
    } else {
      rc = sys_open_nt_file(dirfd, file, flags, mode, fd);
    }
@ -175,5 +210,6 @@ textwindows int sys_open_nt(int dirfd, const char *file, uint32_t flags,
    }
    __fds_unlock();
  }
+  ALLOW_SIGNALS;
  return rc;
 }
--- a/libc/calls/openat-sysv.c
+++ b/libc/calls/openat-sysv.c
@ -27,11 +27,9 @@
 int sys_openat(int dirfd, const char *file, int flags, unsigned mode) {
  static bool once, modernize;
  int d, e, f;
-  /*
-   * RHEL5 doesn't support O_CLOEXEC. It's hard to test for this.
-   * Sometimes the system call succeeds and it just doesn't set the
-   * flag. Other times, it return -530 which makes no sense.
-   */
+  // RHEL5 doesn't support O_CLOEXEC. It's hard to test for this.
+  // Sometimes the system call succeeds and it just doesn't set the
+  // flag. Other times, it return -530 which makes no sense.
  if (!IsLinux() || !(flags & O_CLOEXEC) || modernize) {
    d = __sys_openat(dirfd, file, flags, mode);
  } else if (once) {
--- a/libc/calls/park.c
+++ b/libc/calls/park.c
@ -47,13 +47,9 @@ static textwindows int _park_thread(uint32_t msdelay, sigset_t waitmask,
  om = __sig_beginwait(waitmask);
  if ((rc = _check_cancel()) != -1 && (rc = _check_signal(restartable)) != -1) {
    unassert((wi = WaitForSingleObject(sem, msdelay)) != -1u);
-    if (wi != kNtWaitTimeout) {
-      _check_signal(false);
-      rc = eintr();
-      _check_cancel();
-    } else if ((rc = _check_signal(restartable))) {
-      _check_cancel();
-    }
+    if (restartable && !(pt->pt_flags & PT_RESTARTABLE)) rc = eintr();
+    rc |= _check_signal(restartable);
+    if (rc == -1 && errno == EINTR) _check_cancel();
  }
  __sig_finishwait(om);
  atomic_store_explicit(&pt->pt_blocker, PT_BLOCKER_CPU, memory_order_release);
--- a/libc/calls/pause-nt.c
+++ b/libc/calls/pause-nt.c
@ -17,7 +17,6 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
-#include "libc/calls/sig.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #ifdef __x86_64__

--- a/libc/calls/poll-nt.c
+++ b/libc/calls/poll-nt.c
@ -58,10 +58,10 @@
 // Polls on the New Technology.
 //
 // This function is used to implement poll() and select(). You may poll
-// on both sockets and files at the same time. We also poll for signals
-// while poll is polling.
-textwindows int sys_poll_nt(struct pollfd *fds, uint64_t nfds, uint32_t *ms,
-                            const sigset_t *sigmask) {
+// on sockets, files and the console at the same time. We also poll for
+// both signals and posix thread cancelation, while the poll is polling
+static textwindows int sys_poll_nt_impl(struct pollfd *fds, uint64_t nfds,
+                                        uint32_t *ms, sigset_t sigmask) {
  bool ok;
  uint64_t millis;
  uint32_t cm, avail, waitfor;
@ -72,7 +72,6 @@ textwindows int sys_poll_nt(struct pollfd *fds, uint64_t nfds, uint32_t *ms,
  struct timespec started, deadline, remain, now;
  int i, rc, sn, pn, gotinvals, gotpipes, gotsocks;

-  BLOCK_SIGNALS;
  started = timespec_real();
  deadline = timespec_add(started, timespec_frommillis(ms ? *ms : -1u));

@ -128,7 +127,7 @@ textwindows int sys_poll_nt(struct pollfd *fds, uint64_t nfds, uint32_t *ms,
  __fds_unlock();
  if (rc) {
    // failed to create a polling solution
-    goto Finished;
+    return rc;
  }

  // perform the i/o and sleeping and looping
@ -170,8 +169,7 @@ textwindows int sys_poll_nt(struct pollfd *fds, uint64_t nfds, uint32_t *ms,
    // compute a small time slice we don't mind sleeping for
    if (sn) {
      if ((gotsocks = WSAPoll(sockfds, sn, 0)) == -1) {
-        rc = __winsockerr();
-        goto Finished;
+        return __winsockerr();
      }
    } else {
      gotsocks = 0;
@ -190,8 +188,8 @@ textwindows int sys_poll_nt(struct pollfd *fds, uint64_t nfds, uint32_t *ms,
        if (waitfor) {
          POLLTRACE("poll() sleeping for %'d out of %'lu ms", waitfor,
                    timespec_tomillis(remain));
-          if ((rc = _park_norestart(waitfor, sigmask ? *sigmask : 0)) == -1) {
-            goto Finished;  // eintr, ecanceled, etc.
+          if ((rc = _park_norestart(waitfor, sigmask)) == -1) {
+            return -1;  // eintr, ecanceled, etc.
          }
        }
      }
@ -221,9 +219,14 @@ textwindows int sys_poll_nt(struct pollfd *fds, uint64_t nfds, uint32_t *ms,
  }

  // and finally return
-  rc = gotinvals + gotpipes + gotsocks;
+  return gotinvals + gotpipes + gotsocks;
+}

-Finished:
+textwindows int sys_poll_nt(struct pollfd *fds, uint64_t nfds, uint32_t *ms,
+                            const sigset_t *sigmask) {
+  int rc;
+  BLOCK_SIGNALS;
+  rc = sys_poll_nt_impl(fds, nfds, ms, sigmask ? *sigmask : 0);
  ALLOW_SIGNALS;
  return rc;
 }
--- a/libc/calls/pread.c
+++ b/libc/calls/pread.c
@ -72,7 +72,7 @@ ssize_t pread(int fd, void *buf, size_t size, int64_t offset) {
    rc = sys_pread(fd, buf, size, offset, offset);
  } else if (__isfdkind(fd, kFdSocket)) {
    rc = espipe();
-  } else if (__isfdkind(fd, kFdFile)) {
+  } else if (__isfdkind(fd, kFdFile) || __isfdkind(fd, kFdDevNull)) {
    rc = sys_read_nt(fd, (struct iovec[]){{buf, size}}, 1, offset);
  } else {
    rc = ebadf();
--- a/libc/calls/printfds.c
+++ b/libc/calls/printfds.c
@ -32,6 +32,8 @@ static const char *__fdkind2str(int x) {
      return "kFdSocket";
    case kFdConsole:
      return "kFdConsole";
+    case kFdDevNull:
+      return "kFdDevNull";
    case kFdSerial:
      return "kFdSerial";
    case kFdZip:
--- a/libc/calls/pwrite.c
+++ b/libc/calls/pwrite.c
@ -65,7 +65,7 @@ ssize_t pwrite(int fd, const void *buf, size_t size, int64_t offset) {
    rc = sys_pwrite(fd, buf, size, offset, offset);
  } else if (__isfdkind(fd, kFdSocket)) {
    rc = espipe();
-  } else if (__isfdkind(fd, kFdFile)) {
+  } else if (__isfdkind(fd, kFdFile) || __isfdkind(fd, kFdDevNull)) {
    rc = sys_write_nt(fd, (struct iovec[]){{(void *)buf, size}}, 1, offset);
  } else {
    return ebadf();
--- a/libc/calls/read-nt.c
+++ b/libc/calls/read-nt.c
@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
 #include "libc/atomic.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/sig.internal.h"
@ -733,8 +734,10 @@ static textwindows int WaitForConsole(struct Fd *f, sigset_t waitmask) {
  atomic_store_explicit(&pt->pt_blocker, PT_BLOCKER_SEM, memory_order_release);
  m = __sig_beginwait(waitmask);
  if ((rc = _check_cancel()) != -1 && (rc = _check_signal(true)) != -1) {
-    WaitForMultipleObjects(2, (int64_t[2]){sem, __keystroke.cin}, 0, ms);
+    int64_t hands[2] = {sem, __keystroke.cin};
+    unassert(WaitForMultipleObjects(2, hands, 0, ms) != -1u);
    if (~pt->pt_flags & PT_RESTARTABLE) rc = eintr();
+    rc |= _check_signal(true);
    if (rc == -1 && errno == EINTR) _check_cancel();
  }
  __sig_finishwait(m);
@ -763,6 +766,11 @@ textwindows ssize_t sys_read_nt_impl(int fd, void *data, size_t size,

  // switch to terminal polyfill if reading from win32 console
  struct Fd *f = g_fds.p + fd;
+
+  if (f->kind == kFdDevNull) {
+    return 0;
+  }
+
  if (f->kind == kFdConsole) {
    return ReadFromConsole(f, data, size, waitmask);
  }
--- a/libc/calls/readv-nt.c
+++ b/libc/calls/readv-nt.c
@ -28,6 +28,7 @@ textwindows ssize_t sys_readv_nt(int fd, const struct iovec *iov, int iovlen) {
  switch (g_fds.p[fd].kind) {
    case kFdFile:
    case kFdConsole:
+    case kFdDevNull:
      return sys_read_nt(fd, iov, iovlen, -1);
    case kFdSocket:
      return _weaken(sys_recv_nt)(fd, iov, iovlen, 0);
--- a/libc/calls/readwrite-nt.c
+++ b/libc/calls/readwrite-nt.c
@ -83,7 +83,9 @@ sys_readwrite_nt(int fd, void *data, size_t size, ssize_t offset,
  // similar to the lseek() system call, they too raise ESPIPE when
  // operating on a non-seekable file.
  bool pwriting = offset != -1;
-  bool seekable = f->kind == kFdFile && GetFileType(handle) == kNtFileTypeDisk;
+  bool seekable =
+      (f->kind == kFdFile && GetFileType(handle) == kNtFileTypeDisk) ||
+      f->kind == kFdDevNull;
  if (pwriting && !seekable) {
    return espipe();
  }
--- a/libc/calls/setfl.c
+++ b/libc/calls/setfl.c
@ -0,0 +1,71 @@
+/*-*- 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/calls/internal.h"
+#include "libc/calls/struct/fd.internal.h"
+#include "libc/calls/syscall_support-nt.internal.h"
+#include "libc/nt/createfile.h"
+#include "libc/nt/enum/fileflagandattributes.h"
+#include "libc/nt/files.h"
+#include "libc/nt/runtime.h"
+#include "libc/sysv/consts/o.h"
+
+textwindows int sys_fcntl_nt_setfl(int fd, unsigned flags) {
+
+  // you may change the following:
+  //
+  // - O_NONBLOCK     make read() raise EAGAIN
+  // - O_APPEND       for toggling append mode
+  // - O_RANDOM       alt. for posix_fadvise()
+  // - O_SEQUENTIAL   alt. for posix_fadvise()
+  // - O_DIRECT       works but haven't tested
+  //
+  // the other bits are ignored.
+  unsigned allowed = O_APPEND | O_SEQUENTIAL | O_RANDOM | O_DIRECT | O_NONBLOCK;
+  unsigned needreo = O_APPEND | O_SEQUENTIAL | O_RANDOM | O_DIRECT;
+  unsigned newflag = (g_fds.p[fd].flags & ~allowed) | (flags & allowed);
+
+  if (g_fds.p[fd].kind == kFdFile &&
+      ((g_fds.p[fd].flags & needreo) ^ (flags & needreo))) {
+    unsigned perm, share, attr;
+    if (GetNtOpenFlags(newflag, g_fds.p[fd].mode, &perm, &share, 0, &attr) ==
+        -1) {
+      return -1;
+    }
+    // MSDN says only these are allowed, otherwise it returns EINVAL.
+    attr &= kNtFileFlagBackupSemantics | kNtFileFlagDeleteOnClose |
+            kNtFileFlagNoBuffering | kNtFileFlagOpenNoRecall |
+            kNtFileFlagOpenReparsePoint | kNtFileFlagOverlapped |
+            kNtFileFlagPosixSemantics | kNtFileFlagRandomAccess |
+            kNtFileFlagSequentialScan | kNtFileFlagWriteThrough;
+    intptr_t hand;
+    if ((hand = ReOpenFile(g_fds.p[fd].handle, perm, share, attr)) != -1) {
+      if (hand != g_fds.p[fd].handle) {
+        CloseHandle(g_fds.p[fd].handle);
+        g_fds.p[fd].handle = hand;
+      }
+    } else {
+      return __winerr();
+    }
+  }
+
+  // 1. ignore flags that aren't access mode flags
+  // 2. return zero if nothing's changed
+  g_fds.p[fd].flags = newflag;
+  return 0;
+}
--- a/libc/calls/sig.c
+++ b/libc/calls/sig.c
@ -88,11 +88,13 @@ textwindows bool __sig_ignored(int sig) {
 textwindows void __sig_delete(int sig) {
  struct Dll *e;
  __sig.pending &= ~(1ull << (sig - 1));
+  BLOCK_SIGNALS;
  _pthread_lock();
  for (e = dll_last(_pthread_list); e; e = dll_prev(_pthread_list, e)) {
    POSIXTHREAD_CONTAINER(e)->tib->tib_sigpending &= ~(1ull << (sig - 1));
  }
  _pthread_unlock();
+  ALLOW_SIGNALS;
 }

 static textwindows bool __sig_should_use_altstack(unsigned flags,
@ -219,7 +221,7 @@ textwindows void __sig_cancel(struct PosixThread *pt, int sig, unsigned flags) {
 }

 static textwindows wontreturn void __sig_tramp(struct SignalFrame *sf) {
-  ++__sig.count;
+  atomic_fetch_add_explicit(&__sig.count, 1, memory_order_relaxed);
  int sig = sf->si.si_signo;
  sigset_t blocksigs = __sighandmask[sig];
  if (!(sf->flags & SA_NODEFER)) blocksigs |= 1ull << (sig - 1);
@ -309,7 +311,9 @@ static int __sig_killer(struct PosixThread *pt, int sig, int sic) {
 textwindows int __sig_kill(struct PosixThread *pt, int sig, int sic) {
  int rc;
  BLOCK_SIGNALS;
+  _pthread_ref(pt);
  rc = __sig_killer(pt, sig, sic);
+  _pthread_unref(pt);
  ALLOW_SIGNALS;
  return rc;
 }
@ -333,7 +337,7 @@ textwindows void __sig_generate(int sig, int sic) {
        atomic_load_explicit(&pt->pt_status, memory_order_acquire) <
            kPosixThreadTerminated &&
        !(pt->tib->tib_sigmask & (1ull << (sig - 1)))) {
-      mark = pt;
+      _pthread_ref((mark = pt));
      break;
    }
  }
@ -345,6 +349,7 @@ textwindows void __sig_generate(int sig, int sic) {
    STRACE("all threads block %G so adding to pending signals of process", sig);
    __sig.pending |= 1ull << (sig - 1);
  }
+  _pthread_unref(mark);
  ALLOW_SIGNALS;
 }

@ -411,7 +416,7 @@ static void __sig_unmaskable(struct NtExceptionPointers *ep, int code, int sig,
                             struct CosmoTib *tib) {

  // increment the signal count for getrusage()
-  ++__sig.count;
+  atomic_fetch_add_explicit(&__sig.count, 1, memory_order_relaxed);

  // log vital crash information reliably for --strace before doing much
  // we don't print this without the flag since raw numbers scare people
--- a/libc/calls/sigignore.c
+++ b/libc/calls/sigignore.c
@ -18,14 +18,11 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/struct/sigaction.h"
-#include "libc/str/str.h"

 /**
 * Configures process to ignore signal.
 */
 int sigignore(int sig) {
-  struct sigaction sa;
-  bzero(&sa, sizeof(sa));
-  sa.sa_handler = SIG_IGN;
+  struct sigaction sa = {.sa_handler = SIG_IGN};
  return sigaction(sig, &sa, 0);
 }
--- a/libc/calls/sigpending.c
+++ b/libc/calls/sigpending.c
@ -21,6 +21,7 @@
 #include "libc/calls/struct/sigset.internal.h"
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
+#include "libc/intrin/atomic.h"
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/sysv/errfuns.h"
@ -53,7 +54,8 @@ int sigpending(sigset_t *pending) {
    }
    rc = 0;
  } else if (IsWindows()) {
-    *pending = __sig.pending | __get_tls()->tib_sigpending;
+    *pending = atomic_load_explicit(&__sig.pending, memory_order_acquire) |
+               __get_tls()->tib_sigpending;
    rc = 0;
  } else {
    rc = enosys();
--- a/libc/calls/state.internal.h
+++ b/libc/calls/state.internal.h
@ -1,6 +1,7 @@
 #ifndef COSMOPOLITAN_LIBC_CALLS_STATE_INTERNAL_H_
 #define COSMOPOLITAN_LIBC_CALLS_STATE_INTERNAL_H_
 #include "libc/calls/calls.h"
+#include "libc/nt/struct/securityattributes.h"
 #include "libc/thread/thread.h"
 #include "libc/thread/tls.h"
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
--- a/libc/calls/struct/fd.internal.h
+++ b/libc/calls/struct/fd.internal.h
@ -11,6 +11,7 @@ COSMOPOLITAN_C_START_
 #define kFdZip      6
 #define kFdEpoll    7
 #define kFdReserved 8
+#define kFdDevNull  9

 struct Fd {
  char kind;
--- a/libc/calls/struct/stat.internal.h
+++ b/libc/calls/struct/stat.internal.h
@ -7,7 +7,9 @@ COSMOPOLITAN_C_START_

 int sys_fstat(int, struct stat *);
 int sys_fstatat(int, const char *, struct stat *, int);
-int sys_fstat_nt(int64_t, struct stat *);
+int sys_fstat_nt(int, struct stat *);
+int sys_fstat_nt_special(int, struct stat *);
+int sys_fstat_nt_handle(int64_t, struct stat *);
 int sys_fstatat_nt(int, const char *, struct stat *, int);
 int sys_lstat_nt(const char *, struct stat *);
 int sys_fstat_metal(int, struct stat *);
--- a/libc/calls/syscall_support-nt.internal.h
+++ b/libc/calls/syscall_support-nt.internal.h
@ -16,6 +16,7 @@ int __mkntpath2(const char *, char16_t[hasatleast PATH_MAX], int);
 int __mkntpathat(int, const char *, int, char16_t[hasatleast PATH_MAX]);
 int __mkntpathath(int64_t, const char *, int, char16_t[hasatleast PATH_MAX]);
 int ntaccesscheck(const char16_t *, uint32_t) paramsnonnull();
+int sys_fcntl_nt_setfl(int, unsigned);
 int sys_pause_nt(void);
 int64_t __fix_enotdir(int64_t, char16_t *);
 int64_t __fix_enotdir3(int64_t, char16_t *, char16_t *);
--- a/libc/calls/writev-nt.c
+++ b/libc/calls/writev-nt.c
@ -27,6 +27,7 @@ textwindows ssize_t sys_writev_nt(int fd, const struct iovec *iov, int iovlen) {
  switch (g_fds.p[fd].kind) {
    case kFdFile:
    case kFdConsole:
+    case kFdDevNull:
      return sys_write_nt(fd, iov, iovlen, -1);
    case kFdSocket:
      return _weaken(sys_send_nt)(fd, iov, iovlen, 0);