From: Peter Zijlstra <peterz@infradead.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
dja@axtens.net, elver@google.com, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, christophe.leroy@c-s.fr,
linux-s390@vger.kernel.org, linux-arch@vger.kernel.org,
x86@kernel.org, kasan-dev@googlegroups.com,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [GIT PULL] Please pull powerpc/linux.git powerpc-5.5-2 tag (topic/kasan-bitops)
Date: Tue, 10 Dec 2019 11:15:45 +0100 [thread overview]
Message-ID: <20191210101545.GL2844@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <87wob4pwnl.fsf@mpe.ellerman.id.au>
On Tue, Dec 10, 2019 at 04:38:54PM +1100, Michael Ellerman wrote:
> Good question, I'll have a look.
>
> There seems to be confusion about what the type of the bit number is,
> which is leading to sign extension in some cases and not others.
Shiny.
> It looks like the type should be unsigned long?
I'm thinking unsigned makes most sense, I mean, negative bit offsets
should 'work' but that's almost always guaranteed to be an out-of-bound
operation.
As to 'long' vs 'int', I'm not sure, 4G bits is a long bitmap. But I
suppose since the bitmap itself is 'unsigned long', we might as well use
'unsigned long' for the bitnr too.
> Documentation/core-api/atomic_ops.rst: void __clear_bit_unlock(unsigned long nr, unsigned long *addr);
> arch/mips/include/asm/bitops.h:static inline void __clear_bit_unlock(unsigned long nr, volatile unsigned long *addr)
> arch/powerpc/include/asm/bitops.h:static inline void arch___clear_bit_unlock(int nr, volatile unsigned long *addr)
> arch/riscv/include/asm/bitops.h:static inline void __clear_bit_unlock(unsigned long nr, volatile unsigned long *addr)
> arch/s390/include/asm/bitops.h:static inline void arch___clear_bit_unlock(unsigned long nr,
> include/asm-generic/bitops/instrumented-lock.h:static inline void __clear_bit_unlock(long nr, volatile unsigned long *addr)
> include/asm-generic/bitops/lock.h:static inline void __clear_bit_unlock(unsigned int nr,
>
> So I guess step one is to convert our versions to use unsigned long, so
> we're at least not tripping over that difference when comparing the
> assembly.
Yeah, I'll look at fixing the generic code, bitops/atomic.h and
bitops/non-atomic.h don't even agree on the type of bitnr.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-s390@vger.kernel.org, elver@google.com,
Will Deacon <will@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
x86@kernel.org, linux-kernel@vger.kernel.org,
kasan-dev@googlegroups.com, linux-arch@vger.kernel.org,
Mark Rutland <mark.rutland@arm.com>,
linuxppc-dev@lists.ozlabs.org, dja@axtens.net
Subject: Re: [GIT PULL] Please pull powerpc/linux.git powerpc-5.5-2 tag (topic/kasan-bitops)
Date: Tue, 10 Dec 2019 11:15:45 +0100 [thread overview]
Message-ID: <20191210101545.GL2844@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <87wob4pwnl.fsf@mpe.ellerman.id.au>
On Tue, Dec 10, 2019 at 04:38:54PM +1100, Michael Ellerman wrote:
> Good question, I'll have a look.
>
> There seems to be confusion about what the type of the bit number is,
> which is leading to sign extension in some cases and not others.
Shiny.
> It looks like the type should be unsigned long?
I'm thinking unsigned makes most sense, I mean, negative bit offsets
should 'work' but that's almost always guaranteed to be an out-of-bound
operation.
As to 'long' vs 'int', I'm not sure, 4G bits is a long bitmap. But I
suppose since the bitmap itself is 'unsigned long', we might as well use
'unsigned long' for the bitnr too.
> Documentation/core-api/atomic_ops.rst: void __clear_bit_unlock(unsigned long nr, unsigned long *addr);
> arch/mips/include/asm/bitops.h:static inline void __clear_bit_unlock(unsigned long nr, volatile unsigned long *addr)
> arch/powerpc/include/asm/bitops.h:static inline void arch___clear_bit_unlock(int nr, volatile unsigned long *addr)
> arch/riscv/include/asm/bitops.h:static inline void __clear_bit_unlock(unsigned long nr, volatile unsigned long *addr)
> arch/s390/include/asm/bitops.h:static inline void arch___clear_bit_unlock(unsigned long nr,
> include/asm-generic/bitops/instrumented-lock.h:static inline void __clear_bit_unlock(long nr, volatile unsigned long *addr)
> include/asm-generic/bitops/lock.h:static inline void __clear_bit_unlock(unsigned int nr,
>
> So I guess step one is to convert our versions to use unsigned long, so
> we're at least not tripping over that difference when comparing the
> assembly.
Yeah, I'll look at fixing the generic code, bitops/atomic.h and
bitops/non-atomic.h don't even agree on the type of bitnr.
next prev parent reply other threads:[~2019-12-10 10:16 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-06 12:46 [GIT PULL] Please pull powerpc/linux.git powerpc-5.5-2 tag (topic/kasan-bitops) Michael Ellerman
2019-12-06 12:46 ` Michael Ellerman
2019-12-06 13:16 ` Peter Zijlstra
2019-12-06 13:16 ` Peter Zijlstra
2019-12-10 5:38 ` Michael Ellerman
2019-12-10 5:38 ` Michael Ellerman
2019-12-10 10:15 ` Peter Zijlstra [this message]
2019-12-10 10:15 ` Peter Zijlstra
2019-12-11 0:29 ` Michael Ellerman
2019-12-11 0:29 ` Michael Ellerman
2019-12-12 5:42 ` READ_ONCE() + STACKPROTECTOR_STRONG == :/ (was Re: [GIT PULL] Please pull powerpc/linux.git powerpc-5.5-2 tag (topic/kasan-bitops)) Michael Ellerman
2019-12-12 5:42 ` Michael Ellerman
2019-12-12 8:01 ` Peter Zijlstra
2019-12-12 8:01 ` Peter Zijlstra
2019-12-12 10:07 ` Will Deacon
2019-12-12 10:07 ` Will Deacon
2019-12-12 10:46 ` Peter Zijlstra
2019-12-12 10:46 ` Peter Zijlstra
2019-12-12 17:04 ` Will Deacon
2019-12-12 17:04 ` Will Deacon
2019-12-12 17:16 ` Will Deacon
2019-12-12 17:16 ` Will Deacon
2019-12-12 17:41 ` Linus Torvalds
2019-12-12 17:41 ` Linus Torvalds
2019-12-12 17:50 ` Segher Boessenkool
2019-12-12 17:50 ` Segher Boessenkool
2019-12-12 18:06 ` Will Deacon
2019-12-12 18:06 ` Will Deacon
2019-12-12 18:29 ` Christian Borntraeger
2019-12-12 18:29 ` Christian Borntraeger
2019-12-12 18:43 ` Linus Torvalds
2019-12-12 18:43 ` Linus Torvalds
2019-12-12 19:34 ` Will Deacon
2019-12-12 19:34 ` Will Deacon
2019-12-12 20:21 ` Peter Zijlstra
2019-12-12 20:21 ` Peter Zijlstra
2019-12-12 20:53 ` Peter Zijlstra
2019-12-12 20:53 ` Peter Zijlstra
2019-12-13 10:47 ` Luc Van Oostenryck
2019-12-13 10:47 ` Luc Van Oostenryck
2019-12-13 12:56 ` Peter Zijlstra
2019-12-13 12:56 ` Peter Zijlstra
2019-12-13 14:28 ` Luc Van Oostenryck
2019-12-13 14:28 ` Luc Van Oostenryck
2019-12-12 20:49 ` Linus Torvalds
2019-12-12 20:49 ` Linus Torvalds
2019-12-13 13:17 ` Arnd Bergmann
2019-12-13 13:17 ` Arnd Bergmann
2019-12-13 21:32 ` Arnd Bergmann
2019-12-13 21:32 ` Arnd Bergmann
2019-12-13 22:01 ` Linus Torvalds
2019-12-13 22:01 ` Linus Torvalds
2019-12-16 10:28 ` Will Deacon
2019-12-16 10:28 ` Will Deacon
2019-12-16 11:47 ` Peter Zijlstra
2019-12-16 11:47 ` Peter Zijlstra
2019-12-16 12:06 ` Arnd Bergmann
2019-12-16 12:06 ` Arnd Bergmann
2019-12-17 17:07 ` Will Deacon
2019-12-17 17:07 ` Will Deacon
2019-12-17 18:04 ` Linus Torvalds
2019-12-17 18:04 ` Linus Torvalds
2019-12-17 18:05 ` Linus Torvalds
2019-12-17 18:05 ` Linus Torvalds
2019-12-17 18:31 ` Will Deacon
2019-12-17 18:31 ` Will Deacon
2019-12-17 18:32 ` Linus Torvalds
2019-12-17 18:32 ` Linus Torvalds
2019-12-18 12:17 ` Michael Ellerman
2019-12-18 12:17 ` Michael Ellerman
2019-12-19 12:11 ` Will Deacon
2019-12-19 12:11 ` Will Deacon
2019-12-18 10:22 ` Christian Borntraeger
2019-12-18 10:22 ` Christian Borntraeger
2019-12-18 10:35 ` Will Deacon
2019-12-18 10:35 ` Will Deacon
2019-12-13 12:07 ` Michael Ellerman
2019-12-13 12:07 ` Michael Ellerman
2019-12-13 13:53 ` Segher Boessenkool
2019-12-13 13:53 ` Segher Boessenkool
2019-12-13 21:06 ` Michael Ellerman
2019-12-13 21:06 ` Michael Ellerman
2019-12-12 15:10 ` Segher Boessenkool
2019-12-12 15:10 ` Segher Boessenkool
2019-12-06 22:15 ` [GIT PULL] Please pull powerpc/linux.git powerpc-5.5-2 tag (topic/kasan-bitops) pr-tracker-bot
2019-12-06 22:15 ` pr-tracker-bot
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