Re: [uml-devel] UML patches against vanilla 2.6.0

[BlaisorBlade <blaisorblade_spam@yahoo.it>]

Alle 19:27, venerdì 26 dicembre 2003, Cameron Patrick ha scritto:
> On Fri, Dec 26, 2003 at 07:05:48PM +0100, BlaisorBlade wrote:
> | Go here:
> |
> | http://web.tiscali.it/no-redirect-tiscali/blaisorblade/index.html
>
> Which says:
>
> 	The only problematic patch is A-04-MM-compile-fix.patch, but
> 	maybe i386 can live even with it (I don't remember if I got a
> 	successful compilation with it applied). However, I think it's
> 	not at all safe even if it compiles.
>
> and in the README:
>
> 	but I think you'd better avoid doing this or do a complete
> 	backup, since you'll need it...).

> Eeek!  I just upgraded my home desktop to a 2.6.0 kernel with that patch
> applied (actually as part of Jeff's 2.6.0-test9 patch) and so far it
> seems to be working.
Are you sure? If you compile a stock 2.6.0 with Jeff's 2.6.0-test9 patch and 
try to compile an i386 kernel, you'll get soon errors about 
do_mmap_pgoff(except if you applied a host-skas to your 2.6 tree).

> Looking at the patch, it seems innocuous enough -
> why should it be unsafe on an i386 kernel?

I don't know actually, but it doesn't seem innocuous.

Instead, FIXADDR_USER_START is replaced by FIXADDR_START(+ some syntactical 
changes that do not hurt). And they have a different meaning(see 
include/asm-i386/fixmap.h).

Since I'm not a VM hacker, and I don't understand the change, I just say that 
that shouldn't be used, for prudence's sake. That mention about backup is 
maybe a bit exaggerated, but it's a form of "no warranty" disclaimer.

*NOTE*: the combo patches from Ingo Molnar contain this, too(I don't know if 
he noticed this change at all), and he probably used this without problem. So 
I may be wrong at all.

Bye
-- 
cat <<EOSIGN
Paolo Giarrusso, aka Blaisorblade
Linux Kernel 2.4.21/2.6.0-test on an i686; Linux registered user n. 292729
EOSIGN



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