On Thu, 30 Jan 2025 at 04:54, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
>
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> Add support for architecture-optimized implementations of the CRC64
> library functions, following the approach taken for the CRC32 and
> CRC-T10DIF library functions.
>
> Also take the opportunity to tweak the function prototypes:
> - Use 'const void *' for the lib entry points (since this is easier for
> users) but 'const u8 *' for the underlying arch and generic functions
> (since this is easier for the implementations of these functions).
> - Don't bother with __pure. It's an unusual optimization that doesn't
> help properly written code. It's a weird quirk we can do without.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
> include/linux/crc64.h | 26 ++++++++++++++++++++++----
> lib/Kconfig | 7 +++++++
> lib/crc64.c | 36 ++++++++----------------------------
> 3 files changed, 37 insertions(+), 32 deletions(-)
>
Reviewed-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> diff --git a/include/linux/crc64.h b/include/linux/crc64.h
> index 17cf5af3e78e..41de30b907df 100644
> --- a/include/linux/crc64.h
> +++ b/include/linux/crc64.h
> @@ -5,12 +5,28 @@
> #ifndef _LINUX_CRC64_H
> #define _LINUX_CRC64_H
>
> #include <linux/types.h>
>
> -u64 __pure crc64_be(u64 crc, const void *p, size_t len);
> -u64 __pure crc64_nvme_generic(u64 crc, const void *p, size_t len);
> +u64 crc64_be_arch(u64 crc, const u8 *p, size_t len);
> +u64 crc64_be_generic(u64 crc, const u8 *p, size_t len);
> +u64 crc64_nvme_arch(u64 crc, const u8 *p, size_t len);
> +u64 crc64_nvme_generic(u64 crc, const u8 *p, size_t len);
> +
> +/**
> + * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
> + * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
> + * or the previous crc64 value if computing incrementally.
> + * @p: pointer to buffer over which CRC64 is run
> + * @len: length of buffer @p
> + */
> +static inline u64 crc64_be(u64 crc, const void *p, size_t len)
> +{
> + if (IS_ENABLED(CONFIG_CRC64_ARCH))
> + return crc64_be_arch(crc, p, len);
> + return crc64_be_generic(crc, p, len);
> +}
>
> /**
> * crc64_nvme - Calculate CRC64-NVME
> * @crc: seed value for computation. 0 for a new CRC calculation, or the
> * previous crc64 value if computing incrementally.
> @@ -18,11 +34,13 @@ u64 __pure crc64_nvme_generic(u64 crc, const void *p, size_t len);
> * @len: length of buffer @p
> *
> * This computes the CRC64 defined in the NVME NVM Command Set Specification,
> * *including the bitwise inversion at the beginning and end*.
> */
> -static inline u64 crc64_nvme(u64 crc, const u8 *p, size_t len)
> +static inline u64 crc64_nvme(u64 crc, const void *p, size_t len)
> {
> - return crc64_nvme_generic(crc, p, len);
> + if (IS_ENABLED(CONFIG_CRC64_ARCH))
> + return ~crc64_nvme_arch(~crc, p, len);
> + return ~crc64_nvme_generic(~crc, p, len);
> }
>
> #endif /* _LINUX_CRC64_H */
> diff --git a/lib/Kconfig b/lib/Kconfig
> index da07fd39cf97..67bbf4f64dd9 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -199,10 +199,17 @@ config CRC64
> This option is provided for the case where no in-kernel-tree
> modules require CRC64 functions, but a module built outside
> the kernel tree does. Such modules that use library CRC64
> functions require M here.
>
> +config ARCH_HAS_CRC64
> + bool
> +
> +config CRC64_ARCH
> + tristate
> + default CRC64 if ARCH_HAS_CRC64 && CRC_OPTIMIZATIONS
> +
> config CRC4
> tristate "CRC4 functions"
> help
> This option is provided for the case where no in-kernel-tree
> modules require CRC4 functions, but a module built outside
> diff --git a/lib/crc64.c b/lib/crc64.c
> index d6f3f245eede..5b1b17057f0a 100644
> --- a/lib/crc64.c
> +++ b/lib/crc64.c
> @@ -39,40 +39,20 @@
> #include "crc64table.h"
>
> MODULE_DESCRIPTION("CRC64 calculations");
> MODULE_LICENSE("GPL v2");
>
> -/**
> - * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
> - * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
> - * or the previous crc64 value if computing incrementally.
> - * @p: pointer to buffer over which CRC64 is run
> - * @len: length of buffer @p
> - */
> -u64 __pure crc64_be(u64 crc, const void *p, size_t len)
> +u64 crc64_be_generic(u64 crc, const u8 *p, size_t len)
> {
> - size_t i, t;
> -
> - const unsigned char *_p = p;
> -
> - for (i = 0; i < len; i++) {
> - t = ((crc >> 56) ^ (*_p++)) & 0xFF;
> - crc = crc64table[t] ^ (crc << 8);
> - }
> -
> + while (len--)
> + crc = (crc << 8) ^ crc64table[(crc >> 56) ^ *p++];
> return crc;
> }
> -EXPORT_SYMBOL_GPL(crc64_be);
> +EXPORT_SYMBOL_GPL(crc64_be_generic);
>
> -u64 __pure crc64_nvme_generic(u64 crc, const void *p, size_t len)
> +u64 crc64_nvme_generic(u64 crc, const u8 *p, size_t len)
> {
> - const unsigned char *_p = p;
> - size_t i;
> -
> - crc = ~crc;
> -
> - for (i = 0; i < len; i++)
> - crc = (crc >> 8) ^ crc64nvmetable[(crc & 0xff) ^ *_p++];
> -
> - return ~crc;
> + while (len--)
> + crc = (crc >> 8) ^ crc64nvmetable[(crc & 0xff) ^ *p++];
> + return crc;
> }
> EXPORT_SYMBOL_GPL(crc64_nvme_generic);
> --
> 2.48.1
>
