Re: [PATCH v2 0/5] implement lightweight guard pages

[Vlastimil Babka]

On 10/23/24 10:56, Dmitry Vyukov wrote:
>>
>> Overall while I sympathise with this, it feels dangerous and a pretty major
>> change, because there'll be something somewhere that will break because it
>> expects faults to be swallowed that we no longer do swallow.
>>
>> So I'd say it'd be something we should defer, but of course it's a highly
>> user-facing change so how easy that would be I don't know.
>>
>> But I definitely don't think a 'introduce the ability to do cheap PROT_NONE
>> guards' series is the place to also fundmentally change how user access
>> page faults are handled within the kernel :)
> 
> Will delivering signals on kernel access be a backwards compatible
> change? Or will we need a different API? MADV_GUARD_POISON_KERNEL?
> It's just somewhat painful to detect/update all userspace if we add
> this feature in future. Can we say signal delivery on kernel accesses
> is unspecified?

Would adding signal delivery to guard PTEs only help enough the ASAN etc
usecase? Wouldn't it be instead possible to add some prctl to opt-in the
whole ASANized process to deliver all existing segfaults as signals instead
of -EFAULT ?