Re: [Kgdb-bugreport] [PATCH] i386/x86_64 h/w breakpoints: do update DR3 (take 3)

[Pete/Piet D. <pe...@bl...>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Sergei Shtylyov wrote:
> Hello.
> 
> Jason Wessel wrote:
> 
>>>    Hm... yet the kernel I was booting was UP.  The same happened with 
>>> SMP kernel I've just tried.  Now I'm confused. :-/
> 
>>>>> something was broken WRT handling of the h/w breask as being per-CPU 
>>>>> resource but not seeing anything obvious...
> 
>> The piece that clears DR7 is called _cpu_init().
>> It seems that we'll have to patch this to contain the state of the hw 
>> registers from KGDB.  Part of this is due to the lazy way the kernel 
>> handles the breakpoints today.  My thoughts are that other debuggers or 
>> tools besides kgdb should be able to make use of this so it should be
> 
>     Yes, that would be good thing to use for the userspace debugging to.
> 
>> done in a platform independent way and the initialization values should 
>> perhaps be globals, or that there should be a kernel space version of 
>> the registers.  Doing this would be useful to in that you could check it 
>> on the task swap
> 
>     Task reschedule you mean?

I think so, as I recall each task has it's own copy of the debug registers.


> 
>> and set it on the jump from user to kernel space if you 
>> really wanted to have complete control.
> 
>     Yes, that needs to be done when gdb starts using h/w breakpoints for the 
> userspace debugging...
> 
>> An initial work around might be the attached patch.
> 
>     It seems both an overkill as it's x86 specific -- we already have 
> kernel-side breakpoint info mirrored in hw_breakpoint[], so I don't see why 
> would we need another array...

Yea, I was also wondering about the need for the additional array.

- -piet

> 
>> Jason.
> 
> WBR, Sergei
> 
> -------------------------------------------------------------------------
> This SF.net email is sponsored by: Splunk Inc.
> Still grepping through log files to find problems?  Stop.
> Now Search log events and configuration files using AJAX and a browser.
> Download your FREE copy of Splunk now >> http://get.splunk.com/
> _______________________________________________
> Kgdb-bugreport mailing list
> Kgd...@li...
> https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport
> 

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFHCyM5JICwm/rv3hoRAu75AJ93ZprcrU2O9FRjUHT+ezmtxfL1EwCcCU5k
LxvpU3WvI6/l3Ke+ZcXIovw=
=9t0l
-----END PGP SIGNATURE-----