[Xen-devel] Re: possible changes was Re: [PATCH] make domu_debug run-time option + fix int3 handling for MP

[Kip Macy <kmacy@xxxxxxxxxx>]

> 
> Not if I understand the purpose of this patch. As I understand it, the 
> sole reason for making domu_debug configurable per-domain is to 
> distinguish the cause of an 'int3' when you take an int3 trap. If a 
> domain is a domu_debug domain then you assume that any int3 is for the 
> domu debugger; otherwise, none are.

Correct.

> Apart from not being a very nice extension of the domain-building 
> interface, 

I won't argue that enabling it belongs in the domain-building interface. So 
lets 
not get stuck on that aspect.


> I think the correct solution is to have a breakpoint-setting 
> API within Xen that is shared by all of the debugger stubs. 

This is a very kernel-stub centric point of view.

> This would 
> allow each debugger to set and clear breakpoints (i.e., add and remove 
> int3 instructions), and would automatically demux int3 traps to the 
> correct debugger(s), and/or propagate the trap up to the guest kernel 
> if appropriate.

No differentiation is made between setting / removing int3 and other
modifications to memory in ptrace, /proc or the GDB stub protocol. What you're
basically asking is to move debugger state into xen by having xen know about who
put what breakpoints where. This is a non-trivial imposition and incompatible 
with the tools with which I am acquainted.



                                -Kip

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel