Re: [PATCH v11 7/9] x86/traps: Communicate a LASS violation in #GP message

Sohil Mehta
2025-10-31T19:59:13Z

On 10/31/2025 10:16 AM, Dave Hansen wrote:
> On 10/29/25 14:03, Sohil Mehta wrote:
>> To make the transition easier, enhance the #GP Oops message to include a
>> hint about LASS violations. Also, add a special hint for kernel NULL
>> pointer dereferences to match with the existing #PF message.
>
> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
>
> This also reminds me... Are there tests for this somewhere? How did you
> test all these new messages?

I have some very simple kernel modules that access invalid user memory
and generate these faults. I configure the kernel not to panic/reboot.
But, I have been running them manually.

Invalid accesses from the kernel generate:
#PF (without LASS):
BUG: kernel NULL pointer dereference, address: 0000000000000000
BUG: unable to handle page fault for address: 0000000000100000

#GP (with LASS):
Oops: general protection fault, kernel NULL pointer dereference 0x0: 0000
Oops: general protection fault, probably LASS violation for address
0x100000: 0000

For testing user SIGSEGVs, the Vsyscall tests have been sufficient to
cover all scenarios.

Were you looking for anything specific? I can clean them up and post
them if required.