tdep/2249: display base and limit for %gs segment

[jreiser@BitWagon.com]

>Number:         2249
>Category:       tdep
>Synopsis:       display base and limit for %gs segment
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Sun Apr 08 21:38:01 BST 2007
>Closed-Date:
>Last-Modified:
>Originator:     John Reiser
>Release:        6.6-7
>Organization:
>Environment:
i386 Linux (Fedora Core 7)
>Description:
"info registers" should display the base and limit for segment %gs, to aid in debugging thread implementation (or other code which uses %gs as an additional segment.)  The base and limit values are specified in the most recent __NR_modify_ldt or __NR_clone system call.  Track them as such system calls are made, or query the operating system for their current values.

Currently only the selector values are displayed:
-----
(gdb) info registers
   . . .
cs             0x73     115
ss             0x7b     123
ds             0x7b     123
es             0x7b     123
fs             0x0      0
gs             0x33     51
-----
>How-To-Repeat:
(gdb) info registers
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: