Debug registers on FreeBSD

[Anderson Eduardo]

Thanks all,

Now I understood too more. I found some manuals of the AMD and I saw more some details about debug registers. I'm going to try doing some hacks today.  If I have questions I send it again.


> From: jhb at freebsd.org
> To: kostikbel at gmail.com
> Subject: Re: Debug registers on FreeBSD
> Date: Thu, 18 Feb 2010 10:23:34 -0500
> CC: freebsd-hackers at freebsd.org; anderson_underground at hotmail.com
> 
> On Thursday 18 February 2010 10:12:39 am Kostik Belousov wrote:
> > On Thu, Feb 18, 2010 at 09:44:24AM -0500, John Baldwin wrote:
> > > On Wednesday 17 February 2010 11:07:36 pm Anderson Eduardo wrote:
> > > > 
> > > > Hello Folks,
> > > > 
> > > > First, I'm starting in the world of the debugging FreeBSD Kernel and, I 
> > > don't know to use kgdb and ddb properly and, I need set breakpoints using 
> > > debug register. Those breakpoints in the all tasks.
> > > 
> > > This last might be tricky to accomplish because cpu_switch() will swap out
> > > the debug registers if a thread is using them.  However, you can easily
> > > manage hardware breakpoints from ddb using the 'hwatch' command.  It is 
> > > documented in ddb(4).  kgdb doesn't support setting hardware watch points
> > > it seems.  Note that you can try to use 'db_md_set_watchpoint()' from your
> > > kernel module (with DDB compiled into your kernel) if you want to set the
> > > address progammatically rather than via the 'hwatch' command in ddb.
> > 
> > I remember that ddb only sets %dr on the CPU it happens to execute.
> 
> Yes, same with the db_md_* callbacks.
> 
> -- 
> John Baldwin
 		 	   		  
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