Revert "tty: Add a new file /proc/tty/consoles"

This reverts commit f4a3e0bceb57466c31757f25e4e0ed108d1299ec.  Jiri
Sladby points out that the tty structure we're using may already be
gone, and Al Viro doesn't hold back in complaining about the random
loading of 'filp->private_data' which doesn't have to be a pointer at
all, nor does checking the magic field for TTY_MAGIC prove anything.

Belated review by Al:

 "a) global variable depending on stdin of the last opener? Affecting
     output of read(2)? Really?

  b) iterator is broken; list should be locked in ->start(), unlocked in
     ->stop() and *NOT* unlocked/relocked in ->next()

  c) ->show() ought to do nothing in case of ->device == NULL, instead
     of skipping those in ->next()/->start()

  d) regardless of the merits of the bright idea about asterisk at that
     line in output *and* regardless of (a), the implementation is not
     only atrociously ugly, it's actually very likely to be a roothole.
     Verifying that Cthulhu knows what number happens to be address of a
     tty_struct by blindly dereferencing memory at that address...
     Ouch.

  Please revert that crap."

And Christoph pipes in and NAK's the approach of walking fd tables etc
too.  So it's pretty unanimous.

Noticed-by: Jri Slaby <jslaby@suse.cz>
Requested-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Werner Fink <werner@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 32 deletions

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 98223a676940..a6aca8740883 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1075,7 +1075,6 @@ Table 1-11: Files in /proc/tty
  drivers       list of drivers and their usage                
  ldiscs        registered line disciplines                    
  driver/serial usage statistic and status of single tty lines 
- consoles      registered system console lines
 ..............................................................................
 
 To see  which  tty's  are  currently in use, you can simply look into the file
@@ -1094,37 +1093,6 @@ To see  which  tty's  are  currently in use, you can simply look into the file
   /dev/tty             /dev/tty        5       0 system:/dev/tty 
   unknown              /dev/tty        4    1-63 console 
 
-To see which character device lines are currently used for the system console
-/dev/console, you may simply look into the file /proc/tty/consoles:
-
-  > cat /proc/tty/consoles
-  tty0                 -WU (ECp)       4:7
-  ttyS0                -W- (Ep)        4:64
-
-The columns are:
-
-  device               name of the device
-  operations           R = can do read operations
-                       W = can do write operations
-                       U = can do unblank
-  flags                E = it is enabled
-                       C = it is prefered console
-                       B = it is primary boot console
-                       p = it is used for printk buffer
-                       b = it is not a TTY but a Braille device
-                       a = it is safe to use when cpu is offline
-                       * = it is standard input of the reading process
-  major:minor          major and minor number of the device separated by a colon
-
-If the reading process holds /dev/console open at the regular standard input
-stream the active device will be marked by an asterisk:
-
-  > cat /proc/tty/consoles < /dev/console
-  tty0                 -WU (ECp*)      4:7
-  ttyS0                -W- (Ep)        4:64
-  > tty
-  /dev/pts/3
-
 
 1.8 Miscellaneous kernel statistics in /proc/stat
 -------------------------------------------------