lkml.org 
[lkml]   [2018]   [Aug]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 2/3] x86/mm/pti: Don't clear permissions in pti_clone_pmd()
On Tue, Aug 7, 2018 at 11:34 AM, Dave Hansen <dave.hansen@intel.com> wrote:
> On 08/07/2018 03:24 AM, Joerg Roedel wrote:
>> The function sets the global-bit on cloned PMD entries,
>> which only makes sense when the permissions are identical
>> between the user and the kernel page-table.
>>
>> Further, only write-permissions are cleared for entry-text
>> and kernel-text sections, which are not writeable anyway.
>
> I think this patch is correct, but I'd be curious if Andy remembers why
> we chose to clear _PAGE_RW on these things. It might have been that we
> were trying to say that the *entry* code shouldn't write to this stuff,
> regardless of whether the normal kernel can.
>
> But, either way, I agree with the logic here that Global pages must
> share permissions between both mappings, so feel free to add my Ack. I
> just want to make sure Andy doesn't remember some detail I'm forgetting.

I suspect it's because we used to (and maybe still do) initialize the
user tables before mark_read_only().

\
 
 \ /
  Last update: 2018-08-07 21:39    [W:0.081 / U:0.404 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site