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Message-ID: <1478020909.2236.31.camel@cvidal.org>
Date: Tue, 01 Nov 2016 18:21:49 +0100
From: Colin Vidal <colin@...dal.org>
To: kernel-hardening@...ts.openwall.com, "Reshetova, Elena"
<elena.reshetova@...el.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.
>
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)
Colin
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