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SubjectRe: [PATCH] Fix int1 recursion with unregistered breakpoints
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On 12/14/15, H. Peter Anvin <hpa@zytor.com> wrote:
> On 12/14/15 13:03, Jeff Merkey wrote:
>> Please consider the attached patch.
>>
>> I have reviewed all the code that touches this patch and have
>> determined it will function and support all of the software that
>> depends on this handler properly. I have compiled and tested this
>> patch with a test harness that tests the robustness of the linux
>> breakpoint API and handlers in the following ways:
>>
>> 1. Setting multiple conditional breakpoints through
>> arch_install_hw_breakpoint API across four processors to test the rate
>> at which the interface can handle breakpoint exceptions
>>
>> 2. Setting unregistered breakpoints to test the handlers robustness
>> in dealing with error handling conditions and errant or spurious
>> hardware conditions and to simulate actual "lazy debug register
>> switching" (which does not work BTW) with null bp handlers to test the
>> robustness of the handlers.
>>
>> 3. Clearing and setting breakpoints across multiple processors then
>> triggering concurrent exceptions in both interrupt and process
>> contexts.
>>
>> This patch improves robustness in several ways in the linux kernel:
>>
>> 1. Corrects bug in handling unregistered breakpoints.
>>
>> 2. Provides hardware check of dr7 to determine source of breakpoint
>> if OS cannot ascertain the int1 source from its own state and
>> variables.
>>
>> 3. Actually allows "lazy debug register switching" to function, which
>> until recently has apparently never been actually seen on live
>> hardware or actually tested.
>>
>
> This is all fine and good, but you are missing one of the most important
> parts of a patch: a patch description, describing in detail the problem
> that it solves and why. This description needs to be comprehensible not
> just for people already initiated but for someone doing code archaeology
> a decade from now.
>
> Thanks,
>
> -hpa
>
>
>

Yes sir, I'll get that added right away.

Jeff


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