1 /* Create /proc/self/fd-related names for subfiles of open directories.
3 Copyright (C) 2006, 2009-2010 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 3 of the License, or
8 (at your option) any later version.
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, see <http://www.gnu.org/licenses/>. */
18 /* Written by Paul Eggert. */
22 #include "openat-priv.h"
24 #include <sys/types.h>
34 #include "same-inode.h"
37 /* The results of open() in this file are not used with fchdir,
38 and we do not leak fds to any single-threaded code that could use stdio,
39 therefore save some unnecessary work in fchdir.c.
40 FIXME - if the kernel ever adds support for multi-thread safety for
41 avoiding standard fds, then we should use open_safer. */
45 #define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/%s"
47 #define PROC_SELF_FD_NAME_SIZE_BOUND(len) \
48 (sizeof PROC_SELF_FD_FORMAT - sizeof "%d%s" \
49 + INT_STRLEN_BOUND (int) + (len) + 1)
52 /* Set BUF to the expansion of PROC_SELF_FD_FORMAT, using FD and FILE
53 respectively for %d and %s. If successful, return BUF if the
54 result fits in BUF, dynamically allocated memory otherwise. But
55 return NULL if /proc is not reliable. */
57 openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
59 static int proc_status = 0;
61 /* Make sure the caller gets ENOENT when appropriate. */
70 /* Set PROC_STATUS to a positive value if /proc/self/fd is
71 reliable, and a negative value otherwise. Solaris 10
72 /proc/self/fd mishandles "..", and any file name might expand
73 to ".." after symbolic link expansion, so avoid /proc/self/fd
74 if it mishandles "..". Solaris 10 has openat, but this
75 problem is exhibited on code that built on Solaris 8 and
76 running on Solaris 10. */
78 int proc_self_fd = open ("/proc/self/fd", O_RDONLY);
83 struct stat proc_self_fd_dotdot_st;
84 struct stat proc_self_st;
85 char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof ".." - 1)];
86 sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "..");
88 ((stat (dotdot_buf, &proc_self_fd_dotdot_st) == 0
89 && stat ("/proc/self", &proc_self_st) == 0
90 && SAME_INODE (proc_self_fd_dotdot_st, proc_self_st))
100 size_t bufsize = PROC_SELF_FD_NAME_SIZE_BOUND (strlen (file));
101 char *result = (bufsize < OPENAT_BUFFER_SIZE ? buf : xmalloc (bufsize));
102 sprintf (result, PROC_SELF_FD_FORMAT, fd, file);