Getting a file_t from a file descriptor (was: Tiny error w.r.t. change from 2005-12-05)

[Thomas Schwinge]

[Cced to bug-hurd.]

Hello!

On Thu, Jul 20, 2006 at 08:45:37AM -0700, Paul Eggert wrote:
> Thanks for the fix.

Sure, sure.  :-)


> By the way, is there some way in the Hurd to change the author of a
> file, given only its Unix file descriptor?  I'd like to fix the FIXME
> about 5 lines before your fix, as that problem leads to a potential
> race condition.  I'd appreciate any info you can provide for how to
> map a Unix file descriptor to a Hurd file_t.

While I'm not that proficient in these issues, is this what you're
looking for?

<hurd.h> 
#v+
[...]
/* Return the io server port for file descriptor FD.
   This adds a Mach user reference to the returned port.
   On error, sets `errno' and returns MACH_PORT_NULL.  */

extern io_t __getdport (int fd), getdport (int fd);
[...]
#v-

Used e.g. like this:

[hurd]/utils/login.c
#v+
[...]
  mach_port_t fds[3];           /* File descriptors passed. */
[...]
  for (i = 0; i < 3; i++)
    fds[i] = getdport (i);
[...]
#v-


Please tell if you (or anyone else, of course) need access to a GNU/Hurd
system.


Regards,
 Thomas