5798 fexecve() needed per POSIX 2008

*** 18,27 ****
--- 18,28 ----
   *
   * CDDL HEADER END
   */
  
  /*
+  * Copyright 2015 Garrett D'Amore <garrett@damore.org>
   * Copyright (c) 1988, 2010, Oracle and/or its affiliates. All rights reserved.
   */
  
  /*      Copyright (c) 1988 AT&T */
  /*        All Rights Reserved   */
*** 96,105 ****
--- 97,108 ----
  uint_t auxv_hwcap32_2 = 0;      /* 32-bit version of auxv_hwcap2 */
  #endif
  
  #define PSUIDFLAGS              (SNOCD|SUGID)
  
+ #define DEVFD                   "/dev/fd/"
+ 
  /*
   * exece() - system call wrapper around exec_common()
   */
  int
  exece(const char *fname, const char **argp, const char **envp)
*** 196,206 ****
           * there are other cases in which that failure may occur.
           */
          if ((error = pn_get((char *)fname, UIO_USERSPACE, &pn)) != 0)
                  goto out;
          pn_alloc(&resolvepn);
!         if ((error = lookuppn(&pn, &resolvepn, FOLLOW, &dir, &vp)) != 0) {
                  pn_free(&resolvepn);
                  pn_free(&pn);
                  if (error != EINVAL)
                          goto out;
  
--- 199,224 ----
           * there are other cases in which that failure may occur.
           */
          if ((error = pn_get((char *)fname, UIO_USERSPACE, &pn)) != 0)
                  goto out;
          pn_alloc(&resolvepn);
! 
!         if (strncmp(pn.pn_path, DEVFD, strlen(DEVFD)) == 0) {
!                 /* looks like a /dev/fd node */
!                 char *p = pn.pn_path + strlen(DEVFD);
!                 int fd = stoi(&p);
!                 if ((fd < 0) || (*p != 0) || (p == pn.pn_path)) {
!                         error = EBADF;
!                         goto out;
!                 }
!                 if ((error = fgetstartvp(fd, NULL, &vp)) != 0) {
!                         goto out;       /* error will be EBADF */
!                 }
!                 (void) pn_set(&resolvepn, pn.pn_path);
! 
!         } else if ((error =
!             lookuppn(&pn, &resolvepn, FOLLOW, &dir, &vp)) != 0) {
                  pn_free(&resolvepn);
                  pn_free(&pn);
                  if (error != EINVAL)
                          goto out;