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- /* Create /proc/self/fd-related names for subfiles of open directories.
- Copyright (C) 2006, 2009-2015 Free Software Foundation, Inc.
- This program is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 3 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
- /* Written by Paul Eggert. */
- #include <config.h>
- #include "openat-priv.h"
- #include <sys/types.h>
- #include <sys/stat.h>
- #include <fcntl.h>
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <unistd.h>
- #include "intprops.h"
- #define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/%s"
- #define PROC_SELF_FD_NAME_SIZE_BOUND(len) \
- (sizeof PROC_SELF_FD_FORMAT - sizeof "%d%s" \
- + INT_STRLEN_BOUND (int) + (len) + 1)
- /* Set BUF to the expansion of PROC_SELF_FD_FORMAT, using FD and FILE
- respectively for %d and %s. If successful, return BUF if the
- result fits in BUF, dynamically allocated memory otherwise. But
- return NULL if /proc is not reliable, either because the operating
- system support is lacking or because memory is low. */
- char *
- openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
- {
- static int proc_status = 0;
- /* Make sure the caller gets ENOENT when appropriate. */
- if (!*file)
- {
- buf[0] = '\0';
- return buf;
- }
- if (! proc_status)
- {
- /* Set PROC_STATUS to a positive value if /proc/self/fd is
- reliable, and a negative value otherwise. Solaris 10
- /proc/self/fd mishandles "..", and any file name might expand
- to ".." after symbolic link expansion, so avoid /proc/self/fd
- if it mishandles "..". Solaris 10 has openat, but this
- problem is exhibited on code that built on Solaris 8 and
- running on Solaris 10. */
- int proc_self_fd = open ("/proc/self/fd",
- O_SEARCH | O_DIRECTORY | O_NOCTTY | O_NONBLOCK);
- if (proc_self_fd < 0)
- proc_status = -1;
- else
- {
- /* Detect whether /proc/self/fd/%i/../fd exists, where %i is the
- number of a file descriptor open on /proc/self/fd. On Linux,
- that name resolves to /proc/self/fd, which was opened above.
- However, on Solaris, it may resolve to /proc/self/fd/fd, which
- cannot exist, since all names in /proc/self/fd are numeric. */
- char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof "../fd" - 1)];
- sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "../fd");
- proc_status = access (dotdot_buf, F_OK) ? -1 : 1;
- close (proc_self_fd);
- }
- }
- if (proc_status < 0)
- return NULL;
- else
- {
- size_t bufsize = PROC_SELF_FD_NAME_SIZE_BOUND (strlen (file));
- char *result = buf;
- if (OPENAT_BUFFER_SIZE < bufsize)
- {
- result = malloc (bufsize);
- if (! result)
- return NULL;
- }
- sprintf (result, PROC_SELF_FD_FORMAT, fd, file);
- return result;
- }
- }
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