/* 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;
}
}
/* 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);
if (proc_self_fd < 0)
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);
}
}
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;
}
}
