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/* Create /proc/self/fd-related names for subfiles of open directories.
Copyright (C) 2006, 2009-2022 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 <https://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>
#ifdef __KLIBC__
# include <InnoTekLIBC/backend.h>
#endif
#include "intprops.h"
/* Set BUF to the name of the subfile of the directory identified by
FD, where the subfile is named FILE. If successful, return BUF if
the result fits in BUF, dynamically allocated memory otherwise.
Return NULL (setting errno) on error. */
char *
openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
{
char *result = buf;
int dirlen;
/* Make sure the caller gets ENOENT when appropriate. */
if (!*file)
{
buf[0] = '\0';
return buf;
}
#ifndef __KLIBC__
# define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/"
{
enum {
PROC_SELF_FD_DIR_SIZE_BOUND
= (sizeof PROC_SELF_FD_FORMAT - (sizeof "%d" - 1)
+ INT_STRLEN_BOUND (int))
};
static int proc_status = 0;
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 | O_CLOEXEC);
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_DIR_SIZE_BOUND + sizeof "../fd" - 1];
sprintf (dotdot_buf, PROC_SELF_FD_FORMAT "../fd", proc_self_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_DIR_SIZE_BOUND + strlen (file);
if (OPENAT_BUFFER_SIZE < bufsize)
{
result = malloc (bufsize);
if (! result)
return NULL;
}
dirlen = sprintf (result, PROC_SELF_FD_FORMAT, fd);
}
}
#else
/* OS/2 kLIBC provides a function to retrieve a path from a fd. */
{
char dir[_MAX_PATH];
size_t bufsize;
if (__libc_Back_ioFHToPath (fd, dir, sizeof dir))
return NULL;
dirlen = strlen (dir);
bufsize = dirlen + 1 + strlen (file) + 1; /* 1 for '/', 1 for null */
if (OPENAT_BUFFER_SIZE < bufsize)
{
result = malloc (bufsize);
if (! result)
return NULL;
}
strcpy (result, dir);
result[dirlen++] = '/';
}
#endif
strcpy (result + dirlen, file);
return result;
}
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