lkml.org 
[lkml]   [2014]   [Jun]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86: be more helpful with SMEP faults
On 06/10/2014 01:18 PM, Borislav Petkov wrote:
>> static void
>> show_fault_oops(struct pt_regs *regs, unsigned long error_code,
>> @@ -594,6 +596,11 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code,
>>
>> if (pte && pte_present(*pte) && !pte_exec(*pte))
>> printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
>> + if (pte && pte_present(*pte) && pte_exec(*pte) &&
>> + (pgd_flags(*pgd) & _PAGE_USER) &&
>> + static_cpu_has(X86_FEATURE_SMEP) &&
>
> Btw, we could probably save us this line as CR4 reserved bits should be
> Must-Be-Zero and setting any of those should #GP. And I'm talking about
> pre-SMEP Intel, and AMD machines.
>
> IOW, if CR4.SMEP is set, it definitely means SMEP is present and
> enabled.
>
> hpa, that true?
>

Yes. Also, the Linux kernel will set or clear X86_FEATURE_SMEP to
match, so the two are redundant.

-hpa




\
 
 \ /
  Last update: 2014-06-10 23:01    [W:0.043 / U:0.056 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site