Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue

[Borislav Petkov <bp@amd64.org>]

On Tue, Jul 26, 2011 at 02:34:30PM -0400, Ingo Molnar wrote:
> 
> * Borislav Petkov <bp@amd64.org> wrote:
> 
> > Ok, I went and installed a Debian wheezy with gnome and started 
> > almost everything I could find in the startup menu. Kernel is 3.0 
> > with Linus' simpler fix.
> > 
> > The attached file shows all libraries which would create aliases 
> > (i.e. 2 or more unique values for bits [14:12] along with the 
> > respective count) in the total of:
> > 
> > Total r-xp mappings: 831, aliasing: 240 (0.289%)
> 
> 28.9%, right?

Yessir.

> > For example, libc gets mapped into all possible slots for [14:12]
> > 
> > Library                                 [14:12] count
> > =======                                 ======= =====
> > /lib/libc-2.11.2.so
> >                                         0       12
> >                                         1       12
> >                                         2       11
> >                                         3       12
> >                                         4       13
> >                                         5       16
> >                                         6       13
> >                                         7       9
> > 
> > 
> > and so on.
> 
> Was this done with a stock kernel, or with the simple patch applied?

with the simplest version of Linus' patch:

diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 1dab519..6b1094d 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -90,6 +90,8 @@ static unsigned long mmap_rnd(void)
                        rnd = (long)get_random_int() % (1<<8);
                else
                        rnd = (long)(get_random_int() % (1<<28));
+
+               rnd &= ~0x7;
        }
        return rnd << PAGE_SHIFT;
 }

-- 
Regards/Gruss,
Boris.

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