/* Create /proc/self/fd-related names for subfiles of open directories.
- Copyright (C) 2006 Free Software Foundation, Inc.
+ Copyright (C) 2006, 2009-2014 Free Software Foundation, Inc.
- This program is free software; you can redistribute it and/or modify
+ 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 2, or (at your option)
- any later version.
+ 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
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, write to the Free Software Foundation,
- Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* Written by Paul Eggert. */
#include <fcntl.h>
#include <stdio.h>
+#include <stdlib.h>
#include <string.h>
+#include <unistd.h>
-#include "dirname.h"
#include "intprops.h"
-#include "same-inode.h"
-#include "xalloc.h"
/* The results of open() in this file are not used with fchdir,
- therefore save some unnecessary work in fchdir.c. */
+ and we do not leak fds to any single-threaded code that could use stdio,
+ therefore save some unnecessary work in fchdir.c.
+ FIXME - if the kernel ever adds support for multi-thread safety for
+ avoiding standard fds, then we should use open_safer. */
#undef open
#undef close
/* 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. */
+ 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_RDONLY);
+ 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;
+ proc_status = -1;
else
- {
- struct stat proc_self_fd_dotdot_st;
- struct stat proc_self_st;
- char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof ".." - 1)];
- sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "..");
- proc_status =
- ((stat (dotdot_buf, &proc_self_fd_dotdot_st) == 0
- && stat ("/proc/self", &proc_self_st) == 0
- && SAME_INODE (proc_self_fd_dotdot_st, proc_self_st))
- ? 1 : -1);
- close (proc_self_fd);
- }
+ {
+ /* 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)
else
{
size_t bufsize = PROC_SELF_FD_NAME_SIZE_BOUND (strlen (file));
- char *result = (bufsize < OPENAT_BUFFER_SIZE ? buf : xmalloc (bufsize));
+ 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;
}
projects / gnulib.git / blobdiff