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

>> 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.

Should FIXADDR_USER_END point to the last byte of the relevant page,
or to the first byte of the following page as per Linus's suggestion?
The above looks like an off-by-one bug to me?

Best wishes from Riley.
---
* Nothing as pretty as a smile, nothing as ugly as a frown.

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.488 / Virus Database: 287 - Release Date: 5-Jun-2003

-
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:0.032 / U:2.564 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site