1 /* Create /proc/self/fd-related names for subfiles of open directories.
3 Copyright (C) 2006 Free Software Foundation, Inc.
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2, or (at your option)
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software Foundation,
17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
19 /* Written by Paul Eggert. */
23 #include "openat-priv.h"
25 #include <sys/types.h>
34 #include "same-inode.h"
37 /* The results of open() in this file are not used with fchdir,
38 therefore save some unnecessary work in fchdir.c. */
42 #define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/%s"
44 #define PROC_SELF_FD_NAME_SIZE_BOUND(len) \
45 (sizeof PROC_SELF_FD_FORMAT - sizeof "%d%s" \
46 + INT_STRLEN_BOUND (int) + (len) + 1)
49 /* Set BUF to the expansion of PROC_SELF_FD_FORMAT, using FD and FILE
50 respectively for %d and %s. If successful, return BUF if the
51 result fits in BUF, dynamically allocated memory otherwise. But
52 return NULL if /proc is not reliable. */
54 openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
56 static int proc_status = 0;
60 /* Set PROC_STATUS to a positive value if /proc/self/fd is
61 reliable, and a negative value otherwise. Solaris 10
62 /proc/self/fd mishandles "..", and any file name might expand
63 to ".." after symbolic link expansion, so avoid /proc/self/fd
64 if it mishandles "..". Solaris 10 has openat, but this
65 problem is exhibited on code that built on Solaris 8 and
66 running on Solaris 10. */
68 int proc_self_fd = open ("/proc/self/fd", O_RDONLY);
73 struct stat proc_self_fd_dotdot_st;
74 struct stat proc_self_st;
75 char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof ".." - 1)];
76 sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "..");
78 ((stat (dotdot_buf, &proc_self_fd_dotdot_st) == 0
79 && stat ("/proc/self", &proc_self_st) == 0
80 && SAME_INODE (proc_self_fd_dotdot_st, proc_self_st))
90 size_t bufsize = PROC_SELF_FD_NAME_SIZE_BOUND (strlen (file));
91 char *result = (bufsize < OPENAT_BUFFER_SIZE ? buf : xmalloc (bufsize));
92 sprintf (result, PROC_SELF_FD_FORMAT, fd, file);