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Message-ID: <alpine.DEB.2.20.1706281709140.1970@nanos>
Date: Wed, 28 Jun 2017 17:24:24 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Mark Rutland <mark.rutland@....com>
cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Ingo Molnar <mingo@...nel.org>,
Dmitry Vyukov <dvyukov@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Will Deacon <will.deacon@....com>,
"H. Peter Anvin" <hpa@...or.com>,
kasan-dev <kasan-dev@...glegroups.com>,
"x86@...nel.org" <x86@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] locking/atomics: don't alias ____ptr
On Wed, 28 Jun 2017, Mark Rutland wrote:
> On Wed, Jun 28, 2017 at 03:54:42PM +0200, Thomas Gleixner wrote:
> > > static inline unsigned long cmpxchg_varsize(void *ptr, unsigned long old,
> > > unsigned long new, int size)
> > > {
> > > switch (size) {
> > > case 1:
> > > case 2:
> > > case 4:
> > > break;
> > > case 8:
> > > if (sizeof(unsigned long) == 8)
> > > break;
> > > default:
> > > BUILD_BUG_ON(1);
> > > }
> > > kasan_check(ptr, size);
> > > return arch_cmpxchg(ptr, old, new);
> > > }
>
> This'll need to re-cast things before the call to arch_cmpxchg(), and we
> can move the check above the switch, as in [2].
Sure, but I rather see that changed to:
1) Create arch_cmpxchg8/16/32/64() inlines first
2) Add that varsize wrapper:
static inline unsigned long cmpxchg_varsize(void *ptr, unsigned long old,
unsigned long new, int size)
{
switch (size) {
case 1:
kasan_check_write(ptr, size);
return arch_cmpxchg8((u8 *)ptr, (u8) old, (u8)new);
case 2:
kasan_check_write(ptr, size);
return arch_cmpxchg16((u16 *)ptr, (u16) old, (u16)new);
case 4:
kasan_check_write(ptr, size);
return arch_cmpxchg32((u32 *)ptr, (u32) old, (u32)new);
case 8:
if (sizeof(unsigned long) == 8) {
kasan_check_write(ptr, size);
return arch_cmpxchg64((u64 *)ptr, (u64) old, (u64)new);
}
default:
BUILD_BUG();
}
}
#define cmpxchg(ptr, o, n) \
({ \
((__typeof__(*(ptr)))cmpxchg_varsize((ptr), (unsigned long)(o), \
(unsigned long)(n), sizeof(*(ptr)))); \
})
Which allows us to create:
static inline u8 cmpxchg8(u8 *ptr, u8 old, u8 new)
{
kasan_check_write(ptr, sizeof(old));
return arch_cmpxchg8(ptr, old, new);
}
and friends as well and later migrate the existing users away from that
untyped macro mess.
And instead of adding
#include <asm/atomic-instrumented.h>
to the architecture code, we rather do
# mv arch/xxx/include/asm/atomic.h mv arch/xxx/include/asm/arch_atomic.h
# echo '#include <asm-generic/atomic.h>' >arch/xxx/include/asm/atomic.h
# mv include/asm-generic/atomic.h include/asm-generic/atomic_up.h
and create a new include/asm-generic/atomic.h
#ifndef __ASM_GENERIC_ATOMIC_H
#define __ASM_GENERIC_ATOMIC_H
#ifdef CONFIG_ATOMIC_INSTRUMENTED_H
#include <asm-generic/atomic_instrumented.h>
#else
#include <asm-generic/atomic_up.h>
#endif
#endif
Thanks,
tglx
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