Re: [PATCH] x86/bhi: BHI mitigation can trigger warning in #DB handler

[Andrew Cooper]

On 23/05/2024 6:03 pm, Alexandre Chartre wrote:
>
> On 5/23/24 17:36, Dave Hansen wrote:
>> On 5/23/24 07:52, Alexandre Chartre wrote:
>>>> Should we wrap up this gem and put it with the other entry selftests?
>>>
>>> It looks like tools/testing/selftests/x86/single_step_syscall.c tests
>>> sysenter with TF set but it doesn't check if the kernel issues any
>>> warning.
>>
>> Does it actually trip the warning though? I'm a bit surprised that
>> nobody reported it if so.
>
> single_step_syscall does trigger the warning:
>
> $ ./single_step_syscall
> [RUN]    Set TF and check nop
> [OK]    Survived with TF set and 26 traps
> [RUN]    Set TF and check syscall-less opportunistic sysret
> [OK]    Survived with TF set and 30 traps
> [RUN]    Set TF and check a fast syscall
> [OK]    Survived with TF set and 40 traps
> [RUN]    Fast syscall with TF cleared
> [OK]    Nothing unexpected happened
> [RUN]    Set TF and check SYSENTER
>     Got SIGSEGV with RIP=ed7fe579, TF=256
> [RUN]    Fast syscall with TF cleared
> [OK]    Nothing unexpected happened

:-/

What about the exit code?

I find the absence of a [FAIL] concerning...

~Andrew