[PATCH] riscv: support KASAN instrumentation of bitops

[Alexandre Ghiti]

Hi Qingfang,

On 02/08/2024 06:05, Qingfang Deng wrote:
> From: Qingfang Deng <qingfang.deng at siflower.com.cn>
>
> The arch-specific bitops are not being picked up by the KASAN test
> suite.
>
> 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.
>
> As most comments are identical to the ones in the instrumented headers,
> remove them.
>
> Signed-off-by: Qingfang Deng <qingfang.deng at siflower.com.cn>
> ---
>   arch/riscv/include/asm/bitops.h | 100 +++++---------------------------
>   1 file changed, 15 insertions(+), 85 deletions(-)
>
> diff --git a/arch/riscv/include/asm/bitops.h b/arch/riscv/include/asm/bitops.h
> index 71af9ecfcfcb..44ff3114c112 100644
> --- a/arch/riscv/include/asm/bitops.h
> +++ b/arch/riscv/include/asm/bitops.h
> @@ -221,134 +221,62 @@ static __always_inline int variable_fls(unsigned int x)
>   #define __NOP(x)	(x)
>   #define __NOT(x)	(~(x))
>   
> -/**
> - * test_and_set_bit - Set a bit and return its old value
> - * @nr: Bit to set
> - * @addr: Address to count from
> - *
> - * This operation may be reordered on other architectures than x86.
> - */
> -static inline int test_and_set_bit(int nr, volatile unsigned long *addr)
> +static inline int arch_test_and_set_bit(int nr, volatile unsigned long *addr)
>   {
>   	return __test_and_op_bit(or, __NOP, nr, addr);
>   }
>   
> -/**
> - * test_and_clear_bit - Clear a bit and return its old value
> - * @nr: Bit to clear
> - * @addr: Address to count from
> - *
> - * This operation can be reordered on other architectures other than x86.
> - */
> -static inline int test_and_clear_bit(int nr, volatile unsigned long *addr)
> +static inline int arch_test_and_clear_bit(int nr, volatile unsigned long *addr)
>   {
>   	return __test_and_op_bit(and, __NOT, nr, addr);
>   }
>   
> -/**
> - * test_and_change_bit - Change a bit and return its old value
> - * @nr: Bit to change
> - * @addr: Address to count from
> - *
> - * This operation is atomic and cannot be reordered.
> - * It also implies a memory barrier.
> - */
> -static inline int test_and_change_bit(int nr, volatile unsigned long *addr)
> +static inline int arch_test_and_change_bit(int nr, volatile unsigned long *addr)
>   {
>   	return __test_and_op_bit(xor, __NOP, nr, addr);
>   }
>   
> -/**
> - * set_bit - Atomically set a bit in memory
> - * @nr: the bit to set
> - * @addr: the address to start counting from
> - *
> - * Note: there are no guarantees that this function will not be reordered
> - * on non x86 architectures, so if you are writing portable code,
> - * make sure not to rely on its reordering guarantees.
> - *
> - * Note that @nr may be almost arbitrarily large; this function is not
> - * restricted to acting on a single-word quantity.
> - */
> -static inline void set_bit(int nr, volatile unsigned long *addr)
> +static inline void arch_set_bit(int nr, volatile unsigned long *addr)
>   {
>   	__op_bit(or, __NOP, nr, addr);
>   }
>   
> -/**
> - * clear_bit - Clears a bit in memory
> - * @nr: Bit to clear
> - * @addr: Address to start counting from
> - *
> - * Note: there are no guarantees that this function will not be reordered
> - * on non x86 architectures, so if you are writing portable code,
> - * make sure not to rely on its reordering guarantees.
> - */
> -static inline void clear_bit(int nr, volatile unsigned long *addr)
> +static inline void arch_clear_bit(int nr, volatile unsigned long *addr)
>   {
>   	__op_bit(and, __NOT, nr, addr);
>   }
>   
> -/**
> - * change_bit - Toggle a bit in memory
> - * @nr: Bit to change
> - * @addr: Address to start counting from
> - *
> - * change_bit()  may be reordered on other architectures than x86.
> - * Note that @nr may be almost arbitrarily large; this function is not
> - * restricted to acting on a single-word quantity.
> - */
> -static inline void change_bit(int nr, volatile unsigned long *addr)
> +static inline void arch_change_bit(int nr, volatile unsigned long *addr)
>   {
>   	__op_bit(xor, __NOP, nr, addr);
>   }
>   
> -/**
> - * test_and_set_bit_lock - Set a bit and return its old value, for lock
> - * @nr: Bit to set
> - * @addr: Address to count from
> - *
> - * This operation is atomic and provides acquire barrier semantics.
> - * It can be used to implement bit locks.
> - */
> -static inline int test_and_set_bit_lock(
> +static inline int arch_test_and_set_bit_lock(
>   	unsigned long nr, volatile unsigned long *addr)
>   {
>   	return __test_and_op_bit_ord(or, __NOP, nr, addr, .aq);
>   }
>   
> -/**
> - * clear_bit_unlock - Clear a bit in memory, for unlock
> - * @nr: the bit to set
> - * @addr: the address to start counting from
> - *
> - * This operation is atomic and provides release barrier semantics.
> - */
> -static inline void clear_bit_unlock(
> +static inline void arch_clear_bit_unlock(
>   	unsigned long nr, volatile unsigned long *addr)
>   {
>   	__op_bit_ord(and, __NOT, nr, addr, .rl);
>   }
>   
>   /**
> - * __clear_bit_unlock - Clear a bit in memory, for unlock
> - * @nr: the bit to set
> - * @addr: the address to start counting from
> + * arch___clear_bit_unlock - Clear a bit in memory, for unlock
>    *
> - * This operation is like clear_bit_unlock, however it is not atomic.
> - * It does provide release barrier semantics so it can be used to unlock
> - * a bit lock, however it would only be used if no other CPU can modify
> - * any bits in the memory until the lock is released (a good example is
> - * if the bit lock itself protects access to the other bits in the word).
> + * This should not be used directly, use the instrumented __clear_bit_unlock
> + * instead. See asm-generic/bitops/instrumented-lock.h
>    *
>    * On RISC-V systems there seems to be no benefit to taking advantage of the
>    * non-atomic property here: it's a lot more instructions and we still have to
>    * provide release semantics anyway.
>    */
> -static inline void __clear_bit_unlock(
> +static inline void arch___clear_bit_unlock(
>   	unsigned long nr, volatile unsigned long *addr)
>   {
> -	clear_bit_unlock(nr, addr);
> +	arch_clear_bit_unlock(nr, addr);
>   }
>   
>   static inline bool xor_unlock_is_negative_byte(unsigned long mask,
> @@ -369,6 +297,8 @@ static inline bool xor_unlock_is_negative_byte(unsigned long mask,
>   #undef __NOT
>   #undef __AMO
>   
> +#include <asm-generic/bitops/instrumented-atomic.h>
> +#include <asm-generic/bitops/instrumented-lock.h>
>   #include <asm-generic/bitops/non-atomic.h>
>   #include <asm-generic/bitops/le.h>
>   #include <asm-generic/bitops/ext2-atomic.h>


Samuel has just posted a similar patch here 
https://lore.kernel.org/linux-riscv/20240801033725.28816-1-samuel.holland@sifive.com/T/#t

Thanks,

Alex