lkml.org 
[lkml]   [2015]   [Dec]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 26/34] mm: implement new mprotect_key() system call
From
Date
Hi Michael,

Thanks for all the comments! I'll fix most of it when I post a new
version of the manpage, but I have a few general questions.

On 12/09/2015 03:08 AM, Michael Kerrisk (man-pages) wrote:
>>
>> +is the protection or storage key to assign to the memory.
>
> Why "protection or storage key" here? This phrasing seems a
> little ambiguous to me, given that we also have a 'prot'
> argument. I think it would be clearer just to say
> "protection key". But maybe I'm missing something.

x86 calls it a "protection key" while powerpc calls it a "storage key".
They're called "protection keys" consistently inside the kernel.

Should we just stick to one name in the manpages?

> * A general overview of why this functionality is useful.

Any preference on a central spot to do the general overview? Does it go
in one of the manpages I'm already modifying, or a new one?

> * A note on which architectures support/will support
> this functionality.

x86 only for now. We might get powerpc support down the road somewhere.

> * Explanation of what a protection domain is.

A protection domain is a unique view of memory and is represented by the
value in the PKRU register.

> * Explanation of how a process (thread?) changes its
> protection domain.

Changing protection domains is done by pkey_set() system call, or by
using the WRPKRU instruction. The system call is preferred and less
error-prone since it enforces that a protection is allocated before its
access protection can be modified.

> * Explanation of the relationship between page permission
> bits (PROT_READ/PROT_WRITE/PROTE_EXEC) and
> PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE.
> It's still not clear to me. Do the PKEY_* bits
> override the PROT_* bits. Or, something else?

Protection keys add access restrictions in addition to existing page
permissions. They can only take away access; they never grant
additional access.



\
 
 \ /
  Last update: 2015-12-09 17:01    [W:0.070 / U:0.056 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site