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Date: Fri, 4 Nov 2016 07:04:07 +0000
From: "Reshetova, Elena" <elena.reshetova@...el.com>
To: "kernel-hardening@...ts.openwall.com"
<kernel-hardening@...ts.openwall.com>
CC: Colin Vidal <colin@...dal.org>, "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>, "Hans
Liljestrand" <ishkamiel@...il.com>, David Windsor <dwindsor@...il.com>
Subject: RE: [RFC v3 PATCH 01/13] Add architecture
independent hardened atomic base
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?
>
> Actually this brings us to the fact that we tried to stay away from various relaxed/acquire/release functions (in providing default wrap implementations), but it seems that they are also needed...
>This is just a reminder.
>There is a potential inconsistency in naming:
> atomic_xx_wrap_relaxed vs. atomic_xx_relaxed_wrap
>See:
>http://www.openwall.com/lists/kernel-hardening/2016/10/25/7
>-Takahiro AKASHI
Yes, thank you for reminder! Eeasy to forget all the small things. I propose to stick to atomic_xx_relaxed_wrap (having wrap always at the end),
Since this is what we have for other functions. Any objections?
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