mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-12-22 10:26:20 +00:00
111 lines
3.7 KiB
C
111 lines
3.7 KiB
C
/* Create /proc/self/fd-related names for subfiles of open directories.
|
|
|
|
Copyright (C) 2006, 2009-2014 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"
|
|
|
|
/* The results of open() in this file are not used with fchdir,
|
|
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
|
|
|
|
#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;
|
|
}
|
|
}
|