lkml.org 
[lkml]   [2003]   [Jun]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: FIXMAP-related change to mm/memory.c

On Thu, 12 Jun 2003, David Mosberger wrote:
>
> Is it possible to constrain the FIXADDR range on x86/x86-64
> (FIXADDR_START-FIXADDR_TOP) such that the entire range is read-only by
> user-level? If so, we could simplify the permission test like this:

Well, you could replace the uses of FIXADDR_START/FIXADDR_TOP with
something like FIXADDR_USER_START/FIXADDR_USER_TOP, and then force those
to cover only the _one_ user-accessible page.

Something like

#define FIXADDR_USER_START (fix_to_virt(FIX_VSYSCALL))
#define FIXADDR_USER_END (FIXADDR_USER_START + PAGE_SIZE)

should work. In that case you can drop the page table testing, since we
"know" it is safe.

But I'm too lazy to test, so please send a tested patch,

Linus

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:36    [W:0.037 / U:0.732 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site