lkml.org 
[lkml]   [2003]   [May]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] i386 uaccess to fixmap pages

On Fri, 9 May 2003, Dave Hansen wrote:
>
> We've been playing with patches in the -mjb tree which make PAGE_OFFSET
> and TASK_SIZE move to some weird values. I have it to the point where I
> could do a 3.875:0.125 user:kernel split.

That's still not "weird" in the current sense.

We've always (well, for a long time) been able to handle a TASK_SIZE that
has a 111..00000 pattern - and in fact we used to _depend_ on that kind of
pattern, because macros like "virt_to_phys()" were simple bitwise-and
operations. There may be some code in the kernel that still depends on
that kind of bitwise operation with TASK_SIZE.

Your 3.875:0.125 split still fits that pattern, and thus doesn't create
any new cases.

In contrast, a TASK_SIZE of 0xc1000000 can no longer just "mask off" the
kernel address bits. And _that_ is what I meant with "strange value".

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 13:35    [W:0.076 / U:0.880 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site