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From: Daniel Axtens <dja@axtens.net>
To: Christophe Leroy <christophe.leroy@c-s.fr>, linux-s390@vger.kernel.org,
 linux-arch@vger.kernel.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 2/2] powerpc: support KASAN instrumentation of bitops
In-Reply-To: <a1932e9e-3697-b8a0-c936-098b390b817f@c-s.fr>
References: <20190819062814.5315-1-dja@axtens.net>
 <20190819062814.5315-2-dja@axtens.net>
 <a1932e9e-3697-b8a0-c936-098b390b817f@c-s.fr>
Date: Tue, 20 Aug 2019 12:51:10 +1000
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Cc: Nicholas Piggin <npiggin@gmail.com>, kasan-dev@googlegroups.com
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 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

Christophe Leroy <christophe.leroy@c-s.fr> writes:

> Le 19/08/2019 =C3=A0 08:28, Daniel Axtens a =C3=A9crit=C2=A0:
>> In KASAN development I noticed that the powerpc-specific bitops
>> were not being picked up by the KASAN test suite.
>
> I'm not sure anybody cares about who noticed the problem. This sentence=20
> could be rephrased as:
>
> The powerpc-specific bitops are not being picked up by the KASAN test sui=
te.
>
>>=20
>> Instrumentation is done via the bitops/instrumented-{atomic,lock}.h
>> headers. They require that arch-specific versions of bitop functions
>> are renamed to arch_*. Do this renaming.
>>=20
>> For clear_bit_unlock_is_negative_byte, the current implementation
>> uses the PG_waiters constant. This works because it's a preprocessor
>> macro - so it's only actually evaluated in contexts where PG_waiters
>> is defined. With instrumentation however, it becomes a static inline
>> function, and all of a sudden we need the actual value of PG_waiters.
>> Because of the order of header includes, it's not available and we
>> fail to compile. Instead, manually specify that we care about bit 7.
>> This is still correct: bit 7 is the bit that would mark a negative
>> byte.
>>=20
>> Cc: Nicholas Piggin <npiggin@gmail.com> # clear_bit_unlock_negative_byte
>> Signed-off-by: Daniel Axtens <dja@axtens.net>
>
> Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
>
> Note that this patch might be an opportunity to replace all the=20
> '__inline__' by the standard 'inline' keyword.

New patches sent with these things fixed, thanks.=20
>
> Some () alignment to be fixes as well, see checkpatch warnings/checks at=
=20
> https://openpower.xyz/job/snowpatch/job/snowpatch-linux-checkpatch/8601//=
artifact/linux/checkpatch.log
>
>> ---
>>   arch/powerpc/include/asm/bitops.h | 31 +++++++++++++++++++------------
>>   1 file changed, 19 insertions(+), 12 deletions(-)
>>=20
>> diff --git a/arch/powerpc/include/asm/bitops.h b/arch/powerpc/include/as=
m/bitops.h
>> index 603aed229af7..8615b2bc35fe 100644
>> --- a/arch/powerpc/include/asm/bitops.h
>> +++ b/arch/powerpc/include/asm/bitops.h
>> @@ -86,22 +86,22 @@ DEFINE_BITOP(clear_bits, andc, "")
>>   DEFINE_BITOP(clear_bits_unlock, andc, PPC_RELEASE_BARRIER)
>>   DEFINE_BITOP(change_bits, xor, "")
>>=20=20=20
>> -static __inline__ void set_bit(int nr, volatile unsigned long *addr)
>> +static __inline__ void arch_set_bit(int nr, volatile unsigned long *add=
r)
>>   {
>>   	set_bits(BIT_MASK(nr), addr + BIT_WORD(nr));
>>   }
>>=20=20=20
>> -static __inline__ void clear_bit(int nr, volatile unsigned long *addr)
>> +static __inline__ void arch_clear_bit(int nr, volatile unsigned long *a=
ddr)
>>   {
>>   	clear_bits(BIT_MASK(nr), addr + BIT_WORD(nr));
>>   }
>>=20=20=20
>> -static __inline__ void clear_bit_unlock(int nr, volatile unsigned long =
*addr)
>> +static __inline__ void arch_clear_bit_unlock(int nr, volatile unsigned =
long *addr)
>>   {
>>   	clear_bits_unlock(BIT_MASK(nr), addr + BIT_WORD(nr));
>>   }
>>=20=20=20
>> -static __inline__ void change_bit(int nr, volatile unsigned long *addr)
>> +static __inline__ void arch_change_bit(int nr, volatile unsigned long *=
addr)
>>   {
>>   	change_bits(BIT_MASK(nr), addr + BIT_WORD(nr));
>>   }
>> @@ -138,26 +138,26 @@ DEFINE_TESTOP(test_and_clear_bits, andc, PPC_ATOMI=
C_ENTRY_BARRIER,
>>   DEFINE_TESTOP(test_and_change_bits, xor, PPC_ATOMIC_ENTRY_BARRIER,
>>   	      PPC_ATOMIC_EXIT_BARRIER, 0)
>>=20=20=20
>> -static __inline__ int test_and_set_bit(unsigned long nr,
>> +static __inline__ int arch_test_and_set_bit(unsigned long nr,
>>   				       volatile unsigned long *addr)
>>   {
>>   	return test_and_set_bits(BIT_MASK(nr), addr + BIT_WORD(nr)) !=3D 0;
>>   }
>>=20=20=20
>> -static __inline__ int test_and_set_bit_lock(unsigned long nr,
>> +static __inline__ int arch_test_and_set_bit_lock(unsigned long nr,
>>   				       volatile unsigned long *addr)
>>   {
>>   	return test_and_set_bits_lock(BIT_MASK(nr),
>>   				addr + BIT_WORD(nr)) !=3D 0;
>>   }
>>=20=20=20
>> -static __inline__ int test_and_clear_bit(unsigned long nr,
>> +static __inline__ int arch_test_and_clear_bit(unsigned long nr,
>>   					 volatile unsigned long *addr)
>>   {
>>   	return test_and_clear_bits(BIT_MASK(nr), addr + BIT_WORD(nr)) !=3D 0;
>>   }
>>=20=20=20
>> -static __inline__ int test_and_change_bit(unsigned long nr,
>> +static __inline__ int arch_test_and_change_bit(unsigned long nr,
>>   					  volatile unsigned long *addr)
>>   {
>>   	return test_and_change_bits(BIT_MASK(nr), addr + BIT_WORD(nr)) !=3D 0;
>> @@ -185,15 +185,18 @@ static __inline__ unsigned long clear_bit_unlock_r=
eturn_word(int nr,
>>   	return old;
>>   }
>>=20=20=20
>> -/* This is a special function for mm/filemap.c */
>> -#define clear_bit_unlock_is_negative_byte(nr, addr)			\
>> -	(clear_bit_unlock_return_word(nr, addr) & BIT_MASK(PG_waiters))
>> +/*
>> + * This is a special function for mm/filemap.c
>> + * Bit 7 corresponds to PG_waiters.
>> + */
>> +#define arch_clear_bit_unlock_is_negative_byte(nr, addr)		\
>> +	(clear_bit_unlock_return_word(nr, addr) & BIT_MASK(7))
>>=20=20=20
>>   #endif /* CONFIG_PPC64 */
>>=20=20=20
>>   #include <asm-generic/bitops/non-atomic.h>
>>=20=20=20
>> -static __inline__ void __clear_bit_unlock(int nr, volatile unsigned lon=
g *addr)
>> +static __inline__ void arch___clear_bit_unlock(int nr, volatile unsigne=
d long *addr)
>>   {
>>   	__asm__ __volatile__(PPC_RELEASE_BARRIER "" ::: "memory");
>>   	__clear_bit(nr, addr);
>> @@ -239,6 +242,10 @@ unsigned long __arch_hweight64(__u64 w);
>>=20=20=20
>>   #include <asm-generic/bitops/find.h>
>>=20=20=20
>> +/* wrappers that deal with KASAN instrumentation */
>> +#include <asm-generic/bitops/instrumented-atomic.h>
>> +#include <asm-generic/bitops/instrumented-lock.h>
>> +
>>   /* Little-endian versions */
>>   #include <asm-generic/bitops/le.h>
>>=20=20=20
>>=20