From: Mark Rutland <mark.rutland@arm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Ingo Molnar <mingo@kernel.org>,
Dmitry Vyukov <dvyukov@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will.deacon@arm.com>,
"H. Peter Anvin" <hpa@zytor.com>,
kasan-dev <kasan-dev@googlegroups.com>,
"x86@kernel.org" <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] locking/atomics: don't alias ____ptr
Date: Wed, 28 Jun 2017 16:54:45 +0100 [thread overview]
Message-ID: <20170628155445.GD8252@leverpostej> (raw)
In-Reply-To: <alpine.DEB.2.20.1706281709140.1970@nanos>
On Wed, Jun 28, 2017 at 05:24:24PM +0200, Thomas Gleixner wrote:
> 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.
Sure, that makes sense to me.
>
> 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
Given we're gonig to clean things up, we may as well avoid the backwards
include of <asm-generic/atomic_instrumented.h>, whcih was only there as
a bodge:
For the UP arches we do:
# echo '#include <asm-generic/atomic_up.h>' >arch/xxx/include/asm/atomic.h
# mv include/asm-generic/atomic.h include/asm-generic/atomic_up.h
Then we add a <linux/atomic_instrumented.h>:
#ifndef __LINUX_ATOMIC_INSTRUMENTED_H
#define __LINUX_ATOMIC INSTRUMENTED_H
#include <asm/atomic.h>
#if CONFIG_ATOMIC_INSTRUMENTED_H
<instrumentation>
#endif
#endif /* __LINUX_ATOMIC_ARCH_H */
... and make <linux/atomic.h> incldue that rather than <asm/atomic.h>.
That way the instrumentation's orthogonal to the UP-ness of the arch,
and we can fold any other instrumentation in there, or later move it
directly into <linux/atomic.h>
Thanks,
Mark.
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next prev parent reply other threads:[~2017-06-28 15:55 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1498140468.git.dvyukov@google.com>
[not found] ` <cover.1498140838.git.dvyukov@google.com>
2017-06-22 14:14 ` [PATCH v5 1/4] x86: switch atomic.h to use atomic-instrumented.h Dmitry Vyukov
2017-06-22 21:14 ` Andrew Morton
2017-06-23 8:23 ` Dmitry Vyukov
2017-06-23 8:54 ` Ingo Molnar
2017-06-23 19:00 ` Andrew Morton
2017-06-22 14:14 ` [PATCH v5 2/4] kasan: allow kasan_check_read/write() to accept pointers to volatiles Dmitry Vyukov
2017-06-22 14:14 ` [PATCH v5 3/4] asm-generic: add KASAN instrumentation to atomic operations Dmitry Vyukov
2017-06-28 10:02 ` [PATCH] locking/atomics: don't alias ____ptr Sebastian Andrzej Siewior
2017-06-28 10:16 ` Dmitry Vyukov
2017-06-28 11:10 ` Thomas Gleixner
2017-06-28 11:12 ` Dmitry Vyukov
2017-06-28 11:21 ` Thomas Gleixner
2017-06-28 12:45 ` Mark Rutland
2017-06-28 12:24 ` Thomas Gleixner
2017-06-28 12:27 ` Dmitry Vyukov
2017-06-28 13:33 ` Thomas Gleixner
2017-06-28 11:15 ` Andrey Ryabinin
2017-06-28 12:12 ` Sebastian Andrzej Siewior
2017-06-28 13:20 ` Thomas Gleixner
2017-06-28 13:54 ` Thomas Gleixner
2017-06-28 14:14 ` Mark Rutland
2017-06-28 15:24 ` Thomas Gleixner
2017-06-28 15:54 ` Mark Rutland [this message]
2017-06-28 16:56 ` Ingo Molnar
2017-06-28 18:21 ` Thomas Gleixner
2017-06-29 6:47 ` Thomas Gleixner
2017-06-28 14:00 ` Andrey Ryabinin
2017-06-22 14:14 ` [PATCH v5 4/4] asm-generic, x86: add comments for atomic instrumentation Dmitry Vyukov
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