From: Yury Norov <yury.norov@xxxxxxxxx> Generalize __GENMASK() to support different types, and implement fixed-types versions of GENMASK() based on it. The fixed-type version allows more strict checks to the min/max values accepted, which is useful for defining registers like implemented by i915 and xe drivers with their REG_GENMASK*() macros. The strict checks rely on shift-count-overflow compiler check to fail the build if a number outside of the range allowed is passed. Example: #define FOO_MASK GENMASK_U32(33, 4) will generate a warning like: ../include/linux/bits.h:41:31: error: left shift count >= width of type [-Werror=shift-count-overflow] 41 | (((t)~0ULL - ((t)(1) << (l)) + 1) & \ | ^~ Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx> Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> Acked-by: Jani Nikula <jani.nikula@xxxxxxxxx> --- include/linux/bitops.h | 1 - include/linux/bits.h | 32 ++++++++++++++++++++++---------- 2 files changed, 22 insertions(+), 11 deletions(-) diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 2ba557e067fe..1db50c69cfdb 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -15,7 +15,6 @@ # define aligned_byte_mask(n) (~0xffUL << (BITS_PER_LONG - 8 - 8*(n))) #endif -#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE) #define BITS_TO_LONGS(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(long)) #define BITS_TO_U64(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(u64)) #define BITS_TO_U32(nr) __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(u32)) diff --git a/include/linux/bits.h b/include/linux/bits.h index 7c0cf5031abe..bd56f32de44e 100644 --- a/include/linux/bits.h +++ b/include/linux/bits.h @@ -6,6 +6,8 @@ #include <vdso/bits.h> #include <asm/bitsperlong.h> +#define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE) + #define BIT_MASK(nr) (UL(1) << ((nr) % BITS_PER_LONG)) #define BIT_WORD(nr) ((nr) / BITS_PER_LONG) #define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG)) @@ -30,16 +32,26 @@ #define GENMASK_INPUT_CHECK(h, l) 0 #endif -#define __GENMASK(h, l) \ - (((~UL(0)) - (UL(1) << (l)) + 1) & \ - (~UL(0) >> (BITS_PER_LONG - 1 - (h)))) -#define GENMASK(h, l) \ - (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) +/* + * Generate a mask for the specified type @t. Additional checks are made to + * guarantee the value returned fits in that type, relying on + * shift-count-overflow compiler check to detect incompatible arguments. + * For example, all these create build errors or warnings: + * + * - GENMASK(15, 20): wrong argument order + * - GENMASK(72, 15): doesn't fit unsigned long + * - GENMASK_U32(33, 15): doesn't fit in a u32 + */ +#define __GENMASK(t, h, l) \ + (GENMASK_INPUT_CHECK(h, l) + \ + (((t)~0ULL - ((t)(1) << (l)) + 1) & \ + ((t)~0ULL >> (BITS_PER_TYPE(t) - 1 - (h))))) -#define __GENMASK_ULL(h, l) \ - (((~ULL(0)) - (ULL(1) << (l)) + 1) & \ - (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h)))) -#define GENMASK_ULL(h, l) \ - (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l)) +#define GENMASK(h, l) __GENMASK(unsigned long, h, l) +#define GENMASK_ULL(h, l) __GENMASK(unsigned long long, h, l) +#define GENMASK_U8(h, l) __GENMASK(u8, h, l) +#define GENMASK_U16(h, l) __GENMASK(u16, h, l) +#define GENMASK_U32(h, l) __GENMASK(u32, h, l) +#define GENMASK_U64(h, l) __GENMASK(u64, h, l) #endif /* __LINUX_BITS_H */ -- 2.43.0
