> On Feb 24, 2015, at 2:59 PM, Brian J. Johnson <[email protected]> wrote:
>
> On 02/23/2015 04:55 PM, James Bottomley wrote:
>> On Wed, 2015-02-18 at 23:32 -0800, Andrew Fish wrote:
>>>> On Feb 18, 2015, at 11:19 PM, Sergey Isakov <[email protected]> wrote:
>>>>
>>>> No, memory change is not event for hardware. It is not interrupt
>>>> as well. No matter of UEFI or not.
>>>>
>>>
>>> From a hardware point of view you could make the page write protected
>>> and take a page fault on the write.
>>
>> Please don't do this: I don't think handling interrupts in UEFI is
>> something we want to get into. What happens at runtime when the OS is
>> supposed to be handling all the interrupts? ... the UEFI standard
>> defines no mechanism for handing off interrupts from the OS to the UEFI
>> layer (assuming the OS even determines that's where they belong).
>
> At runtime, the OS will control the interrupt vector table, so you will
> need to use something in the OS to handle it. The BIOS's exception
> handlers are gone at that point.
>
> But handling interrupts in UEFI firmware isn't that hard: debuggers do
> it all the time (see SourceLevelDebugPkg.) And
> UefiCpuPkg/Library/CpuExceptionHandlerLib gives a standardized way to
> register interrupt handlers within the UEFI environment. (Technically,
> that library is a PI spec thing, I believe....) You could make a page
> write protected, or set up a watchpoint in the the debug registers to
> catch writes to that particular address. Then do whatever you need to
> do in the corresponding exception handler. Not that it would be
> trivial, but it would at least be possible.
You could possibly do it on a platform you had total control of, but it would
not be a UEFI kind of thing.
You still have to worry about breaking a debugger.
Thanks,
Andrew Fish
> --
>
> Brian
>
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