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Date: Wed, 2 Nov 2016 04:51:56 +0000
From: "Reshetova, Elena" <elena.reshetova@...el.com>
To: Colin Vidal <colin@...dal.org>, "kernel-hardening@...ts.openwall.com"
<kernel-hardening@...ts.openwall.com>
CC: "keescook@...omium.org" <keescook@...omium.org>, "arnd@...db.de"
<arnd@...db.de>, "tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>, "Anvin, H Peter"
<h.peter.anvin@...el.com>, David Windsor <dwindsor@...il.com>
Subject: RE: [RFC v3 PATCH 01/13] Add architecture
independent hardened atomic base
On Tue, 2016-11-01 at 14:55 +0200, Hans Liljestrand wrote:
> On Tue, Nov 01, 2016 at 12:15:25PM +0000, Reshetova, Elena wrote:
> >
> > >
> > > Hi (again :-)) Elena, Hans,
> >
> > >
> > > diff --git a/include/linux/atomic.h b/include/linux/atomic.h
> > <snip>
> > >
> > > +#ifndef atomic_cmpxchg_wrap
> > > +#define atomic_cmpxchg_wrap(...) \
> > > + __atomic_op_fence(atomic_cmpxchg_wrap, __VA_ARGS__) #endif
> > > #endif /* atomic_cmpxchg_relaxed */
> > >
> >
> > >
> > > I have a problem here. With ARMv7 (without any of my patches), I
> > > have a implicit declaration of atomic_cmpxchg_wrap. Perhaps
> > > something like
> >
> > >
> > > #ifndef atomic_cmpxchg_wrap_relaxed
> > > #define atomic_cmpxchg_wrap_relaxed atomic_cmpxchg_wrap
> >
> > >
> > > is missing? I didn't follow the recent changes of that part, so I
> > > am not quite sure...
> >
> > >
> > > Thanks!
> >
> > >
> > > Colin
> >
> > >
> > > In file included from ./include/linux/spinlock.h:406:0,
> > from ./include/linux/seqlock.h:35,
> > from ./include/linux/time.h:5,
> > from ./include/linux/stat.h:18,
> > from ./include/linux/module.h:10,
> > from net/ipv4/route.c:67:
> > >
> > > net/ipv4/route.c: In function ‘ip_idents_reserve’:
> > > ./include/linux/atomic.h:459:20: error: implicit declaration of
> > > function ‘atomic_cmpxchg_wrap_relaxed’
> > > [-Werror=implicit-function-declaration]
> > __atomic_op_fence(atomic_cmpxchg_wrap, __VA_ARGS__)
> > ^
> > >
> > > ./include/linux/atomic.h:62:9: note: in definition of macro ‘__atomic_op_fence’
> > > typeof(op##_relaxed(args)) __ret; \
> > ^~
> > >
> > > net/ipv4/route.c:488:11: note: in expansion of macro ‘atomic_cmpxchg_wrap’
> > > } while (atomic_cmpxchg_wrap(p_id, old, new) != old);
> >
> > Oh, I think this is because we don't have atomic_cmpxchg_wrap_relaxed defined neither atomic_xchg_wrap_relaxed. Wonder why this doesn't show up on x86, I did many builds without our x86 changes to verify.
> > Hans could you please handle this change today to unblock Colin?
>
> Could have been this was an error that didn't show up on x86, but not
> sure why cmpxchg and xchg wasn't guarded as the other atomic_*_relaxed
> functions. This whole section is a bit iffy, the aim is to be
> analogous to the non-wrap relaxed functions, but without actually
> having relaxed_wrap functions, so basically these probably always just end up defining the _wrap_relaxed as _wrap functions.
>
> I've committed a possible "fix". But I cannot confirm since I don't
> see the error on my build setups.
Thank you Hans!
>
>Yep, seems good here! Thanks!
>FYI, I use generic config files generated by
>
> make ARCH=arm defconfig #for v7
> make ARCH=arm imx_v6_v7_defconfig #for generic atomic64 (v6)
We will add this configuration to our build test set to make sure we don't make mistakes here again.
Best Regards,
Elena.
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