1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __LINUX_BITS_H 3 #define __LINUX_BITS_H 4 5 #include <linux/const.h> 6 #include <vdso/bits.h> 7 #include <uapi/linux/bits.h> 8 #include <asm/bitsperlong.h> 9 10 #define BIT_MASK(nr) (UL(1) << ((nr) % BITS_PER_LONG)) 11 #define BIT_WORD(nr) ((nr) / BITS_PER_LONG) 12 #define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG)) 13 #define BIT_ULL_WORD(nr) ((nr) / BITS_PER_LONG_LONG) 14 #define BITS_PER_BYTE 8 15 #define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE) 16 17 /* 18 * Create a contiguous bitmask starting at bit position @l and ending at 19 * position @h. For example 20 * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000. 21 */ 22 #if !defined(__ASSEMBLY__) 23 24 /* 25 * Missing asm support 26 * 27 * GENMASK_U*() and BIT_U*() depend on BITS_PER_TYPE() which relies on sizeof(), 28 * something not available in asm. Nevertheless, fixed width integers is a C 29 * concept. Assembly code can rely on the long and long long versions instead. 30 */ 31 32 #include <linux/build_bug.h> 33 #include <linux/compiler.h> 34 #include <linux/overflow.h> 35 36 #define GENMASK_INPUT_CHECK(h, l) BUILD_BUG_ON_ZERO(const_true((l) > (h))) 37 38 /* 39 * Generate a mask for the specified type @t. Additional checks are made to 40 * guarantee the value returned fits in that type, relying on 41 * -Wshift-count-overflow compiler check to detect incompatible arguments. 42 * For example, all these create build errors or warnings: 43 * 44 * - GENMASK(15, 20): wrong argument order 45 * - GENMASK(72, 15): doesn't fit unsigned long 46 * - GENMASK_U32(33, 15): doesn't fit in a u32 47 */ 48 #define GENMASK_TYPE(t, h, l) \ 49 ((t)(GENMASK_INPUT_CHECK(h, l) + \ 50 (type_max(t) << (l) & \ 51 type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h))))) 52 53 #define GENMASK_U8(h, l) GENMASK_TYPE(u8, h, l) 54 #define GENMASK_U16(h, l) GENMASK_TYPE(u16, h, l) 55 #define GENMASK_U32(h, l) GENMASK_TYPE(u32, h, l) 56 #define GENMASK_U64(h, l) GENMASK_TYPE(u64, h, l) 57 58 /* 59 * Fixed-type variants of BIT(), with additional checks like GENMASK_TYPE(). The 60 * following examples generate compiler warnings due to -Wshift-count-overflow: 61 * 62 * - BIT_U8(8) 63 * - BIT_U32(-1) 64 * - BIT_U32(40) 65 */ 66 #define BIT_INPUT_CHECK(type, nr) \ 67 BUILD_BUG_ON_ZERO(const_true((nr) >= BITS_PER_TYPE(type))) 68 69 #define BIT_TYPE(type, nr) ((type)(BIT_INPUT_CHECK(type, nr) + BIT_ULL(nr))) 70 71 #define BIT_U8(nr) BIT_TYPE(u8, nr) 72 #define BIT_U16(nr) BIT_TYPE(u16, nr) 73 #define BIT_U32(nr) BIT_TYPE(u32, nr) 74 #define BIT_U64(nr) BIT_TYPE(u64, nr) 75 76 #else /* defined(__ASSEMBLY__) */ 77 78 /* 79 * BUILD_BUG_ON_ZERO is not available in h files included from asm files, 80 * disable the input check if that is the case. 81 */ 82 #define GENMASK_INPUT_CHECK(h, l) 0 83 84 #endif /* !defined(__ASSEMBLY__) */ 85 86 #define GENMASK(h, l) \ 87 (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l)) 88 #define GENMASK_ULL(h, l) \ 89 (GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l)) 90 91 #if !defined(__ASSEMBLY__) 92 /* 93 * Missing asm support 94 * 95 * __GENMASK_U128() depends on _BIT128() which would not work 96 * in the asm code, as it shifts an 'unsigned __int128' data 97 * type instead of direct representation of 128 bit constants 98 * such as long and unsigned long. The fundamental problem is 99 * that a 128 bit constant will get silently truncated by the 100 * gcc compiler. 101 */ 102 #define GENMASK_U128(h, l) \ 103 (GENMASK_INPUT_CHECK(h, l) + __GENMASK_U128(h, l)) 104 #endif 105 106 #endif /* __LINUX_BITS_H */ 107