libuv 2022-07-12 (0c1fa696)

Code extracted from:

    https://github.com/libuv/libuv.git

at commit 0c1fa696aa502eb749c2c4735005f41ba00a27b8 (v1.44.2).

1 files changed, 661 insertions, 125 deletions

diff --git a/src/unix/process.c b/src/unix/process.c
index 91bf3c5..f841536 100644
--- a/src/unix/process.c
+++ b/src/unix/process.c
@@ -27,6 +27,7 @@
 #include <assert.h>
 #include <errno.h>
 #include <signal.h>
+#include <string.h>
 
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -34,9 +35,22 @@
 #include <fcntl.h>
 #include <poll.h>
 
-#if defined(__APPLE__) && !TARGET_OS_IPHONE
+#if defined(__APPLE__)
+# include <spawn.h>
+# include <paths.h>
+# include <sys/kauth.h>
+# include <sys/types.h>
+# include <sys/sysctl.h>
+# include <dlfcn.h>
 # include <crt_externs.h>
+# include <xlocale.h>
 # define environ (*_NSGetEnviron())
+
+/* macOS 10.14 back does not define this constant */
+# ifndef POSIX_SPAWN_SETSID
+#  define POSIX_SPAWN_SETSID 1024
+# endif
+
 #else
 extern char **environ;
 #endif
@@ -49,22 +63,36 @@ extern char **environ;
 # include "zos-base.h"
 #endif
 
+#if defined(__APPLE__) || \
+    defined(__DragonFly__) || \
+    defined(__FreeBSD__) || \
+    defined(__NetBSD__) || \
+    defined(__OpenBSD__)
+#include <sys/event.h>
+#else
+#define UV_USE_SIGCHLD
+#endif
+
 
+#ifdef UV_USE_SIGCHLD
 static void uv__chld(uv_signal_t* handle, int signum) {
+  assert(signum == SIGCHLD);
+  uv__wait_children(handle->loop);
+}
+#endif
+
+void uv__wait_children(uv_loop_t* loop) {
   uv_process_t* process;
-  uv_loop_t* loop;
   int exit_status;
   int term_signal;
   int status;
+  int options;
   pid_t pid;
   QUEUE pending;
   QUEUE* q;
   QUEUE* h;
 
-  assert(signum == SIGCHLD);
-
   QUEUE_INIT(&pending);
-  loop = handle->loop;
 
   h = &loop->process_handles;
   q = QUEUE_HEAD(h);
@@ -72,19 +100,33 @@ static void uv__chld(uv_signal_t* handle, int signum) {
     process = QUEUE_DATA(q, uv_process_t, queue);
     q = QUEUE_NEXT(q);
 
+#ifndef UV_USE_SIGCHLD
+    if ((process->flags & UV_HANDLE_REAP) == 0)
+      continue;
+    options = 0;
+    process->flags &= ~UV_HANDLE_REAP;
+#else
+    options = WNOHANG;
+#endif
+
     do
-      pid = waitpid(process->pid, &status, WNOHANG);
+      pid = waitpid(process->pid, &status, options);
     while (pid == -1 && errno == EINTR);
 
-    if (pid == 0)
+#ifdef UV_USE_SIGCHLD
+    if (pid == 0) /* Not yet exited */
       continue;
+#endif
 
     if (pid == -1) {
       if (errno != ECHILD)
         abort();
+      /* The child died, and we missed it. This probably means someone else
+       * stole the waitpid from us. Handle this by not handling it at all. */
       continue;
     }
 
+    assert(pid == process->pid);
     process->status = status;
     QUEUE_REMOVE(&process->queue);
     QUEUE_INSERT_TAIL(&pending, &process->queue);
@@ -195,16 +237,14 @@ static void uv__write_int(int fd, int val) {
     n = write(fd, &val, sizeof(val));
   while (n == -1 && errno == EINTR);
 
-  if (n == -1 && errno == EPIPE)
-    return; /* parent process has quit */
-
-  assert(n == sizeof(val));
+  /* The write might have failed (e.g. if the parent process has died),
+   * but we have nothing left but to _exit ourself now too. */
+  _exit(127);
 }
 
 
 static void uv__write_errno(int error_fd) {
   uv__write_int(error_fd, UV__ERR(errno));
-  _exit(127);
 }
 
 
@@ -254,22 +294,31 @@ static void uv__process_child_init(const uv_process_options_t* options,
     use_fd = pipes[fd][1];
     if (use_fd < 0 || use_fd >= fd)
       continue;
+#ifdef F_DUPFD_CLOEXEC /* POSIX 2008 */
+    pipes[fd][1] = fcntl(use_fd, F_DUPFD_CLOEXEC, stdio_count);
+#else
     pipes[fd][1] = fcntl(use_fd, F_DUPFD, stdio_count);
+#endif
     if (pipes[fd][1] == -1)
       uv__write_errno(error_fd);
+#ifndef F_DUPFD_CLOEXEC /* POSIX 2008 */
+    n = uv__cloexec(pipes[fd][1], 1);
+    if (n)
+      uv__write_int(error_fd, n);
+#endif
   }
 
   for (fd = 0; fd < stdio_count; fd++) {
-    close_fd = pipes[fd][0];
+    close_fd = -1;
     use_fd = pipes[fd][1];
 
     if (use_fd < 0) {
       if (fd >= 3)
         continue;
       else {
-        /* redirect stdin, stdout and stderr to /dev/null even if UV_IGNORE is
-         * set
-         */
+        /* Redirect stdin, stdout and stderr to /dev/null even if UV_IGNORE is
+         * set. */
+        uv__close_nocheckstdio(fd); /* Free up fd, if it happens to be open. */
         use_fd = open("/dev/null", fd == 0 ? O_RDONLY : O_RDWR);
         close_fd = use_fd;
 
@@ -278,28 +327,27 @@ static void uv__process_child_init(const uv_process_options_t* options,
       }
     }
 
-    if (fd == use_fd)
-      uv__cloexec_fcntl(use_fd, 0);
-    else
+    if (fd == use_fd) {
+      if (close_fd == -1) {
+        n = uv__cloexec(use_fd, 0);
+        if (n)
+          uv__write_int(error_fd, n);
+      }
+    }
+    else {
       fd = dup2(use_fd, fd);
+    }
 
     if (fd == -1)
       uv__write_errno(error_fd);
 
-    if (fd <= 2)
+    if (fd <= 2 && close_fd == -1)
       uv__nonblock_fcntl(fd, 0);
 
     if (close_fd >= stdio_count)
       uv__close(close_fd);
   }
 
-  for (fd = 0; fd < stdio_count; fd++) {
-    use_fd = pipes[fd][1];
-
-    if (use_fd >= stdio_count)
-      uv__close(use_fd);
-  }
-
   if (options->cwd != NULL && chdir(options->cwd))
     uv__write_errno(error_fd);
 
@@ -320,9 +368,8 @@ static void uv__process_child_init(const uv_process_options_t* options,
   if ((options->flags & UV_PROCESS_SETUID) && setuid(options->uid))
     uv__write_errno(error_fd);
 
-  if (options->env != NULL) {
+  if (options->env != NULL)
     environ = options->env;
-  }
 
   /* Reset signal mask just before exec. */
   sigemptyset(&signewset);
@@ -336,11 +383,555 @@ static void uv__process_child_init(const uv_process_options_t* options,
 #endif
 
   uv__write_errno(error_fd);
-  abort();
 }
 #endif
 
 
+#if defined(__APPLE__)
+typedef struct uv__posix_spawn_fncs_tag {
+  struct {
+    int (*addchdir_np)(const posix_spawn_file_actions_t *, const char *);
+  } file_actions;
+} uv__posix_spawn_fncs_t;
+
+
+static uv_once_t posix_spawn_init_once = UV_ONCE_INIT;
+static uv__posix_spawn_fncs_t posix_spawn_fncs;
+static int posix_spawn_can_use_setsid;
+
+
+static void uv__spawn_init_posix_spawn_fncs(void) {
+  /* Try to locate all non-portable functions at runtime */
+  posix_spawn_fncs.file_actions.addchdir_np =
+    dlsym(RTLD_DEFAULT, "posix_spawn_file_actions_addchdir_np");
+}
+
+
+static void uv__spawn_init_can_use_setsid(void) {
+  int which[] = {CTL_KERN, KERN_OSRELEASE};
+  unsigned major;
+  unsigned minor;
+  unsigned patch;
+  char buf[256];
+  size_t len;
+
+  len = sizeof(buf);
+  if (sysctl(which, ARRAY_SIZE(which), buf, &len, NULL, 0))
+    return;
+
+  /* NULL specifies to use LC_C_LOCALE */
+  if (3 != sscanf_l(buf, NULL, "%u.%u.%u", &major, &minor, &patch))
+    return;
+
+  posix_spawn_can_use_setsid = (major >= 19);  /* macOS Catalina */
+}
+
+
+static void uv__spawn_init_posix_spawn(void) {
+  /* Init handles to all potentially non-defined functions */
+  uv__spawn_init_posix_spawn_fncs();
+
+  /* Init feature detection for POSIX_SPAWN_SETSID flag */
+  uv__spawn_init_can_use_setsid();
+}
+
+
+static int uv__spawn_set_posix_spawn_attrs(
+    posix_spawnattr_t* attrs,
+    const uv__posix_spawn_fncs_t* posix_spawn_fncs,
+    const uv_process_options_t* options) {
+  int err;
+  unsigned int flags;
+  sigset_t signal_set;
+
+  err = posix_spawnattr_init(attrs);
+  if (err != 0) {
+    /* If initialization fails, no need to de-init, just return */
+    return err;
+  }
+
+  if (options->flags & (UV_PROCESS_SETUID | UV_PROCESS_SETGID)) {
+    /* kauth_cred_issuser currently requires exactly uid == 0 for these
+     * posixspawn_attrs (set_groups_np, setuid_np, setgid_np), which deviates
+     * from the normal specification of setuid (which also uses euid), and they
+     * are also undocumented syscalls, so we do not use them. */
+    err = ENOSYS;
+    goto error;
+  }
+
+  /* Set flags for spawn behavior
+   * 1) POSIX_SPAWN_CLOEXEC_DEFAULT: (Apple Extension) All descriptors in the
+   *    parent will be treated as if they had been created with O_CLOEXEC. The
+   *    only fds that will be passed on to the child are those manipulated by
+   *    the file actions
+   * 2) POSIX_SPAWN_SETSIGDEF: Signals mentioned in spawn-sigdefault in the
+   *    spawn attributes will be reset to behave as their default
+   * 3) POSIX_SPAWN_SETSIGMASK: Signal mask will be set to the value of
+   *    spawn-sigmask in attributes
+   * 4) POSIX_SPAWN_SETSID: Make the process a new session leader if a detached
+   *    session was requested. */
+  flags = POSIX_SPAWN_CLOEXEC_DEFAULT |
+          POSIX_SPAWN_SETSIGDEF |
+          POSIX_SPAWN_SETSIGMASK;
+  if (options->flags & UV_PROCESS_DETACHED) {
+    /* If running on a version of macOS where this flag is not supported,
+     * revert back to the fork/exec flow. Otherwise posix_spawn will
+     * silently ignore the flag. */
+    if (!posix_spawn_can_use_setsid) {
+      err = ENOSYS;
+      goto error;
+    }
+
+    flags |= POSIX_SPAWN_SETSID;
+  }
+  err = posix_spawnattr_setflags(attrs, flags);
+  if (err != 0)
+    goto error;
+
+  /* Reset all signal the child to their default behavior */
+  sigfillset(&signal_set);
+  err = posix_spawnattr_setsigdefault(attrs, &signal_set);
+  if (err != 0)
+    goto error;
+
+  /* Reset the signal mask for all signals */
+  sigemptyset(&signal_set);
+  err = posix_spawnattr_setsigmask(attrs, &signal_set);
+  if (err != 0)
+    goto error;
+
+  return err;
+
+error:
+  (void) posix_spawnattr_destroy(attrs);
+  return err;
+}
+
+
+static int uv__spawn_set_posix_spawn_file_actions(
+    posix_spawn_file_actions_t* actions,
+    const uv__posix_spawn_fncs_t* posix_spawn_fncs,
+    const uv_process_options_t* options,
+    int stdio_count,
+    int (*pipes)[2]) {
+  int fd;
+  int fd2;
+  int use_fd;
+  int err;
+
+  err = posix_spawn_file_actions_init(actions);
+  if (err != 0) {
+    /* If initialization fails, no need to de-init, just return */
+    return err;
+  }
+
+  /* Set the current working directory if requested */
+  if (options->cwd != NULL) {
+    if (posix_spawn_fncs->file_actions.addchdir_np == NULL) {
+      err = ENOSYS;
+      goto error;
+    }
+
+    err = posix_spawn_fncs->file_actions.addchdir_np(actions, options->cwd);
+    if (err != 0)
+      goto error;
+  }
+
+  /* Do not return ENOSYS after this point, as we may mutate pipes. */
+
+  /* First duplicate low numbered fds, since it's not safe to duplicate them,
+   * they could get replaced. Example: swapping stdout and stderr; without
+   * this fd 2 (stderr) would be duplicated into fd 1, thus making both
+   * stdout and stderr go to the same fd, which was not the intention. */
+  for (fd = 0; fd < stdio_count; fd++) {
+    use_fd = pipes[fd][1];
+    if (use_fd < 0 || use_fd >= fd)
+      continue;
+    use_fd = stdio_count;
+    for (fd2 = 0; fd2 < stdio_count; fd2++) {
+      /* If we were not setting POSIX_SPAWN_CLOEXEC_DEFAULT, we would need to
+       * also consider whether fcntl(fd, F_GETFD) returned without the
+       * FD_CLOEXEC flag set. */
+      if (pipes[fd2][1] == use_fd) {
+        use_fd++;
+        fd2 = 0;
+      }
+    }
+    err = posix_spawn_file_actions_adddup2(
+      actions,
+      pipes[fd][1],
+      use_fd);
+    assert(err != ENOSYS);
+    if (err != 0)
+      goto error;
+    pipes[fd][1] = use_fd;
+  }
+
+  /* Second, move the descriptors into their respective places */
+  for (fd = 0; fd < stdio_count; fd++) {
+    use_fd = pipes[fd][1];
+    if (use_fd < 0) {
+      if (fd >= 3)
+        continue;
+      else {
+        /* If ignored, redirect to (or from) /dev/null, */
+        err = posix_spawn_file_actions_addopen(
+          actions,
+          fd,
+          "/dev/null",
+          fd == 0 ? O_RDONLY : O_RDWR,
+          0);
+        assert(err != ENOSYS);
+        if (err != 0)
+          goto error;
+        continue;
+      }
+    }
+
+    if (fd == use_fd)
+        err = posix_spawn_file_actions_addinherit_np(actions, fd);
+    else
+        err = posix_spawn_file_actions_adddup2(actions, use_fd, fd);
+    assert(err != ENOSYS);
+    if (err != 0)
+      goto error;
+
+    /* Make sure the fd is marked as non-blocking (state shared between child
+     * and parent). */
+    uv__nonblock_fcntl(use_fd, 0);
+  }
+
+  /* Finally, close all the superfluous descriptors */
+  for (fd = 0; fd < stdio_count; fd++) {
+    use_fd = pipes[fd][1];
+    if (use_fd < stdio_count)
+      continue;
+
+    /* Check if we already closed this. */
+    for (fd2 = 0; fd2 < fd; fd2++) {
+      if (pipes[fd2][1] == use_fd)
+          break;
+    }
+    if (fd2 < fd)
+      continue;
+
+    err = posix_spawn_file_actions_addclose(actions, use_fd);
+    assert(err != ENOSYS);
+    if (err != 0)
+      goto error;
+  }
+
+  return 0;
+
+error:
+  (void) posix_spawn_file_actions_destroy(actions);
+  return err;
+}
+
+char* uv__spawn_find_path_in_env(char** env) {
+  char** env_iterator;
+  const char path_var[] = "PATH=";
+
+  /* Look for an environment variable called PATH in the
+   * provided env array, and return its value if found */
+  for (env_iterator = env; *env_iterator != NULL; env_iterator++) {
+    if (strncmp(*env_iterator, path_var, sizeof(path_var) - 1) == 0) {
+      /* Found "PATH=" at the beginning of the string */
+      return *env_iterator + sizeof(path_var) - 1;
+    }
+  }
+
+  return NULL;
+}
+
+
+static int uv__spawn_resolve_and_spawn(const uv_process_options_t* options,
+                                       posix_spawnattr_t* attrs,
+                                       posix_spawn_file_actions_t* actions,
+                                       pid_t* pid) {
+  const char *p;
+  const char *z;
+  const char *path;
+  size_t l;
+  size_t k;
+  int err;
+  int seen_eacces;
+
+  path = NULL;
+  err = -1;
+  seen_eacces = 0;
+
+  /* Short circuit for erroneous case */
+  if (options->file == NULL)
+    return ENOENT;
+
+  /* The environment for the child process is that of the parent unless overriden
+   * by options->env */
+  char** env = environ;
+  if (options->env != NULL)
+    env = options->env;
+
+  /* If options->file contains a slash, posix_spawn/posix_spawnp should behave
+   * the same, and do not involve PATH resolution at all. The libc
+   * `posix_spawnp` provided by Apple is buggy (since 10.15), so we now emulate it
+   * here, per https://github.com/libuv/libuv/pull/3583. */
+  if (strchr(options->file, '/') != NULL) {
+    do
+      err = posix_spawn(pid, options->file, actions, attrs, options->args, env);
+    while (err == EINTR);
+    return err;
+  }
+
+  /* Look for the definition of PATH in the provided env */
+  path = uv__spawn_find_path_in_env(env);
+
+  /* The following resolution logic (execvpe emulation) is copied from
+   * https://git.musl-libc.org/cgit/musl/tree/src/process/execvp.c
+   * and adapted to work for our specific usage */
+
+  /* If no path was provided in env, use the default value
+   * to look for the executable */
+  if (path == NULL)
+    path = _PATH_DEFPATH;
+
+  k = strnlen(options->file, NAME_MAX + 1);
+  if (k > NAME_MAX)
+    return ENAMETOOLONG;
+
+  l = strnlen(path, PATH_MAX - 1) + 1;
+
+  for (p = path;; p = z) {
+    /* Compose the new process file from the entry in the PATH
+     * environment variable and the actual file name */
+    char b[PATH_MAX + NAME_MAX];
+    z = strchr(p, ':');
+    if (!z)
+      z = p + strlen(p);
+    if ((size_t)(z - p) >= l) {
+      if (!*z++)
+        break;
+
+      continue;
+    }
+    memcpy(b, p, z - p);
+    b[z - p] = '/';
+    memcpy(b + (z - p) + (z > p), options->file, k + 1);
+
+    /* Try to spawn the new process file. If it fails with ENOENT, the
+     * new process file is not in this PATH entry, continue with the next
+     * PATH entry. */
+    do
+      err = posix_spawn(pid, b, actions, attrs, options->args, env);
+    while (err == EINTR);
+
+    switch (err) {
+    case EACCES:
+      seen_eacces = 1;
+      break; /* continue search */
+    case ENOENT:
+    case ENOTDIR:
+      break; /* continue search */
+    default:
+      return err;
+    }
+
+    if (!*z++)
+      break;
+  }
+
+  if (seen_eacces)
+    return EACCES;
+  return err;
+}
+
+
+static int uv__spawn_and_init_child_posix_spawn(
+    const uv_process_options_t* options,
+    int stdio_count,
+    int (*pipes)[2],
+    pid_t* pid,
+    const uv__posix_spawn_fncs_t* posix_spawn_fncs) {
+  int err;
+  posix_spawnattr_t attrs;
+  posix_spawn_file_actions_t actions;
+
+  err = uv__spawn_set_posix_spawn_attrs(&attrs, posix_spawn_fncs, options);
+  if (err != 0)
+    goto error;
+
+  /* This may mutate pipes. */
+  err = uv__spawn_set_posix_spawn_file_actions(&actions,
+                                               posix_spawn_fncs,
+                                               options,
+                                               stdio_count,
+                                               pipes);
+  if (err != 0) {
+    (void) posix_spawnattr_destroy(&attrs);
+    goto error;
+  }
+
+  /* Try to spawn options->file resolving in the provided environment
+   * if any */
+  err = uv__spawn_resolve_and_spawn(options, &attrs, &actions, pid);
+  assert(err != ENOSYS);
+
+  /* Destroy the actions/attributes */
+  (void) posix_spawn_file_actions_destroy(&actions);
+  (void) posix_spawnattr_destroy(&attrs);
+
+error:
+  /* In an error situation, the attributes and file actions are
+   * already destroyed, only the happy path requires cleanup */
+  return UV__ERR(err);
+}
+#endif
+
+static int uv__spawn_and_init_child_fork(const uv_process_options_t* options,
+                                         int stdio_count,
+                                         int (*pipes)[2],
+                                         int error_fd,
+                                         pid_t* pid) {
+  sigset_t signewset;
+  sigset_t sigoldset;
+
+  /* Start the child with most signals blocked, to avoid any issues before we
+   * can reset them, but allow program failures to exit (and not hang). */
+  sigfillset(&signewset);
+  sigdelset(&signewset, SIGKILL);
+  sigdelset(&signewset, SIGSTOP);
+  sigdelset(&signewset, SIGTRAP);
+  sigdelset(&signewset, SIGSEGV);
+  sigdelset(&signewset, SIGBUS);
+  sigdelset(&signewset, SIGILL);
+  sigdelset(&signewset, SIGSYS);
+  sigdelset(&signewset, SIGABRT);
+  if (pthread_sigmask(SIG_BLOCK, &signewset, &sigoldset) != 0)
+    abort();
+
+  *pid = fork();
+
+  if (*pid == 0) {
+    /* Fork succeeded, in the child process */
+    uv__process_child_init(options, stdio_count, pipes, error_fd);
+    abort();
+  }
+
+  if (pthread_sigmask(SIG_SETMASK, &sigoldset, NULL) != 0)
+    abort();
+
+  if (*pid == -1)
+    /* Failed to fork */
+    return UV__ERR(errno);
+
+  /* Fork succeeded, in the parent process */
+  return 0;
+}
+
+static int uv__spawn_and_init_child(
+    uv_loop_t* loop,
+    const uv_process_options_t* options,
+    int stdio_count,
+    int (*pipes)[2],
+    pid_t* pid) {
+  int signal_pipe[2] = { -1, -1 };
+  int status;
+  int err;
+  int exec_errorno;
+  ssize_t r;
+
+#if defined(__APPLE__)
+  uv_once(&posix_spawn_init_once, uv__spawn_init_posix_spawn);
+
+  /* Special child process spawn case for macOS Big Sur (11.0) onwards
+   *
+   * Big Sur introduced a significant performance degradation on a call to
+   * fork/exec when the process has many pages mmaped in with MAP_JIT, like, say
+   * a javascript interpreter. Electron-based applications, for example,
+   * are impacted; though the magnitude of the impact depends on how much the
+   * app relies on subprocesses.
+   *
+   * On macOS, though, posix_spawn is implemented in a way that does not
+   * exhibit the problem. This block implements the forking and preparation
+   * logic with posix_spawn and its related primitives. It also takes advantage of
+   * the macOS extension POSIX_SPAWN_CLOEXEC_DEFAULT that makes impossible to
+   * leak descriptors to the child process. */
+  err = uv__spawn_and_init_child_posix_spawn(options,
+                                             stdio_count,
+                                             pipes,
+                                             pid,
+                                             &posix_spawn_fncs);
+
+  /* The posix_spawn flow will return UV_ENOSYS if any of the posix_spawn_x_np
+   * non-standard functions is both _needed_ and _undefined_. In those cases,
+   * default back to the fork/execve strategy. For all other errors, just fail. */
+  if (err != UV_ENOSYS)
+    return err;
+
+#endif
+
+  /* This pipe is used by the parent to wait until
+   * the child has called `execve()`. We need this
+   * to avoid the following race condition:
+   *
+   *    if ((pid = fork()) > 0) {
+   *      kill(pid, SIGTERM);
+   *    }
+   *    else if (pid == 0) {
+   *      execve("/bin/cat", argp, envp);
+   *    }
+   *
+   * The parent sends a signal immediately after forking.
+   * Since the child may not have called `execve()` yet,
+   * there is no telling what process receives the signal,
+   * our fork or /bin/cat.
+   *
+   * To avoid ambiguity, we create a pipe with both ends
+   * marked close-on-exec. Then, after the call to `fork()`,
+   * the parent polls the read end until it EOFs or errors with EPIPE.
+   */
+  err = uv__make_pipe(signal_pipe, 0);
+  if (err)
+    return err;
+
+  /* Acquire write lock to prevent opening new fds in worker threads */
+  uv_rwlock_wrlock(&loop->cloexec_lock);
+
+  err = uv__spawn_and_init_child_fork(options, stdio_count, pipes, signal_pipe[1], pid);
+
+  /* Release lock in parent process */
+  uv_rwlock_wrunlock(&loop->cloexec_lock);
+
+  uv__close(signal_pipe[1]);
+
+  if (err == 0) {
+    do
+      r = read(signal_pipe[0], &exec_errorno, sizeof(exec_errorno));
+    while (r == -1 && errno == EINTR);
+
+    if (r == 0)
+      ; /* okay, EOF */
+    else if (r == sizeof(exec_errorno)) {
+      do
+        err = waitpid(*pid, &status, 0); /* okay, read errorno */
+      while (err == -1 && errno == EINTR);
+      assert(err == *pid);
+      err = exec_errorno;
+    } else if (r == -1 && errno == EPIPE) {
+      /* Something unknown happened to our child before spawn */
+      do
+        err = waitpid(*pid, &status, 0); /* okay, got EPIPE */
+      while (err == -1 && errno == EINTR);
+      assert(err == *pid);
+      err = UV_EPIPE;
+    } else
+      abort();
+  }
+
+  uv__close_nocheckstdio(signal_pipe[0]);
+
+  return err;
+}
+
 int uv_spawn(uv_loop_t* loop,
              uv_process_t* process,
              const uv_process_options_t* options) {
@@ -348,18 +939,13 @@ int uv_spawn(uv_loop_t* loop,
   /* fork is marked __WATCHOS_PROHIBITED __TVOS_PROHIBITED. */
   return UV_ENOSYS;
 #else
-  sigset_t signewset;
-  sigset_t sigoldset;
-  int signal_pipe[2] = { -1, -1 };
   int pipes_storage[8][2];
   int (*pipes)[2];
   int stdio_count;
-  ssize_t r;
   pid_t pid;
   int err;
   int exec_errorno;
   int i;
-  int status;
 
   assert(options->file != NULL);
   assert(!(options->flags & ~(UV_PROCESS_DETACHED |
@@ -372,6 +958,7 @@ int uv_spawn(uv_loop_t* loop,
 
   uv__handle_init(loop, (uv_handle_t*)process, UV_PROCESS);
   QUEUE_INIT(&process->queue);
+  process->status = 0;
 
   stdio_count = options->stdio_count;
   if (stdio_count < 3)
@@ -396,92 +983,43 @@ int uv_spawn(uv_loop_t* loop,
       goto error;
   }
 
-  /* This pipe is used by the parent to wait until
-   * the child has called `execve()`. We need this
-   * to avoid the following race condition:
-   *
-   *    if ((pid = fork()) > 0) {
-   *      kill(pid, SIGTERM);
-   *    }
-   *    else if (pid == 0) {
-   *      execve("/bin/cat", argp, envp);
-   *    }
-   *
-   * The parent sends a signal immediately after forking.
-   * Since the child may not have called `execve()` yet,
-   * there is no telling what process receives the signal,
-   * our fork or /bin/cat.
-   *
-   * To avoid ambiguity, we create a pipe with both ends
-   * marked close-on-exec. Then, after the call to `fork()`,
-   * the parent polls the read end until it EOFs or errors with EPIPE.
-   */
-  err = uv__make_pipe(signal_pipe, 0);
-  if (err)
-    goto error;
-
+#ifdef UV_USE_SIGCHLD
   uv_signal_start(&loop->child_watcher, uv__chld, SIGCHLD);
+#endif
 
-  /* Acquire write lock to prevent opening new fds in worker threads */
-  uv_rwlock_wrlock(&loop->cloexec_lock);
-
-  /* Start the child with most signals blocked, to avoid any issues before we
-   * can reset them, but allow program failures to exit (and not hang). */
-  sigfillset(&signewset);
-  sigdelset(&signewset, SIGKILL);
-  sigdelset(&signewset, SIGSTOP);
-  sigdelset(&signewset, SIGTRAP);
-  sigdelset(&signewset, SIGSEGV);
-  sigdelset(&signewset, SIGBUS);
-  sigdelset(&signewset, SIGILL);
-  sigdelset(&signewset, SIGSYS);
-  sigdelset(&signewset, SIGABRT);
-  if (pthread_sigmask(SIG_BLOCK, &signewset, &sigoldset) != 0)
-    abort();
-
-  pid = fork();
-  if (pid == -1)
-    err = UV__ERR(errno);
-
-  if (pid == 0)
-    uv__process_child_init(options, stdio_count, pipes, signal_pipe[1]);
-
-  if (pthread_sigmask(SIG_SETMASK, &sigoldset, NULL) != 0)
-    abort();
+  /* Spawn the child */
+  exec_errorno = uv__spawn_and_init_child(loop, options, stdio_count, pipes, &pid);
 
-  /* Release lock in parent process */
-  uv_rwlock_wrunlock(&loop->cloexec_lock);
+#if 0
+  /* This runs into a nodejs issue (it expects initialized streams, even if the
+   * exec failed).
+   * See https://github.com/libuv/libuv/pull/3107#issuecomment-782482608 */
+  if (exec_errorno != 0)
+      goto error;
+#endif
 
-  uv__close(signal_pipe[1]);
+  /* Activate this handle if exec() happened successfully, even if we later
+   * fail to open a stdio handle. This ensures we can eventually reap the child
+   * with waitpid. */
+  if (exec_errorno == 0) {
+#ifndef UV_USE_SIGCHLD
+    struct kevent event;
+    EV_SET(&event, pid, EVFILT_PROC, EV_ADD | EV_ONESHOT, NOTE_EXIT, 0, 0);
+    if (kevent(loop->backend_fd, &event, 1, NULL, 0, NULL)) {
+      if (errno != ESRCH)
+        abort();
+      /* Process already exited. Call waitpid on the next loop iteration. */
+      process->flags |= UV_HANDLE_REAP;
+      loop->flags |= UV_LOOP_REAP_CHILDREN;
+    }
+#endif
 
-  if (pid == -1) {
-    uv__close(signal_pipe[0]);
-    goto error;
+    process->pid = pid;
+    process->exit_cb = options->exit_cb;
+    QUEUE_INSERT_TAIL(&loop->process_handles, &process->queue);
+    uv__handle_start(process);
   }
 
-  process->status = 0;
-  exec_errorno = 0;
-  do
-    r = read(signal_pipe[0], &exec_errorno, sizeof(exec_errorno));
-  while (r == -1 && errno == EINTR);
-
-  if (r == 0)
-    ; /* okay, EOF */
-  else if (r == sizeof(exec_errorno)) {
-    do
-      err = waitpid(pid, &status, 0); /* okay, read errorno */
-    while (err == -1 && errno == EINTR);
-    assert(err == pid);
-  } else if (r == -1 && errno == EPIPE) {
-    do
-      err = waitpid(pid, &status, 0); /* okay, got EPIPE */
-    while (err == -1 && errno == EINTR);
-    assert(err == pid);
-  } else
-    abort();
-
-  uv__close_nocheckstdio(signal_pipe[0]);
-
   for (i = 0; i < options->stdio_count; i++) {
     err = uv__process_open_stream(options->stdio + i, pipes[i]);
     if (err == 0)
@@ -493,15 +1031,6 @@ int uv_spawn(uv_loop_t* loop,
     goto error;
   }
 
-  /* Only activate this handle if exec() happened successfully */
-  if (exec_errorno == 0) {
-    QUEUE_INSERT_TAIL(&loop->process_handles, &process->queue);
-    uv__handle_start(process);
-  }
-
-  process->pid = pid;
-  process->exit_cb = options->exit_cb;
-
   if (pipes != pipes_storage)
     uv__free(pipes);
 
@@ -534,9 +1063,16 @@ int uv_process_kill(uv_process_t* process, int signum) {
 
 
 int uv_kill(int pid, int signum) {
-  if (kill(pid, signum))
+  if (kill(pid, signum)) {
+#if defined(__MVS__)
+    /* EPERM is returned if the process is a zombie. */
+    siginfo_t infop;
+    if (errno == EPERM &&
+        waitid(P_PID, pid, &infop, WNOHANG | WNOWAIT | WEXITED) == 0)
+      return 0;
+#endif
     return UV__ERR(errno);
-  else
+  } else
     return 0;
 }