Re: [PATCH V8 26/44] x86/fault: Print PKS MSR on fault

Edgecombe, Rick P
2022-02-01T18:15:47Z

On Thu, 2022-01-27 at 09:54 -0800, ira.weiny@intel.com wrote:
> + if (error_code & X86_PF_PK)
> + pks_dump_fault_info(regs);
> +

If the kernel makes an errant accesses to a userspace address with PKU
enabled and the usersapce page marked AD, it should oops and get here,
but will the X86_PF_PK bit be set even if smap is the real cause? Per
the SDM, it sounds like it would:
"
For accesses to user-mode addresses, the flag is set if
(1) CR4.PKE = 1;
(2) the linear address has protection key i; and
(3) the PKRU register (see Section 4.6.2) is such that either
(a) ADi = 1; or
(b) the following all hold:
(i) WDi = 1;
(ii) the access is a write access; and
(iii) either CR0.WP = 1 or the access causing the
page-fault exception was a user-mode access.
"

...and then this somewhat confusingly dumps the pks register. Is that
the real behavior?