1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_DIV64_H 3 #define _ASM_X86_DIV64_H 4 5 #ifdef CONFIG_X86_32 6 7 #include <linux/types.h> 8 #include <linux/log2.h> 9 10 /* 11 * do_div() is NOT a C function. It wants to return 12 * two values (the quotient and the remainder), but 13 * since that doesn't work very well in C, what it 14 * does is: 15 * 16 * - modifies the 64-bit dividend _in_place_ 17 * - returns the 32-bit remainder 18 * 19 * This ends up being the most efficient "calling 20 * convention" on x86. 21 */ 22 #define do_div(n, base) \ 23 ({ \ 24 unsigned long __upper, __low, __high, __mod, __base; \ 25 __base = (base); \ 26 if (__builtin_constant_p(__base) && is_power_of_2(__base)) { \ 27 __mod = n & (__base - 1); \ 28 n >>= ilog2(__base); \ 29 } else { \ 30 asm("" : "=a" (__low), "=d" (__high) : "A" (n));\ 31 __upper = __high; \ 32 if (__high) { \ 33 __upper = __high % (__base); \ 34 __high = __high / (__base); \ 35 } \ 36 asm("divl %2" : "=a" (__low), "=d" (__mod) \ 37 : "rm" (__base), "0" (__low), "1" (__upper)); \ 38 asm("" : "=A" (n) : "a" (__low), "d" (__high)); \ 39 } \ 40 __mod; \ 41 }) 42 43 static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder) 44 { 45 union { 46 u64 v64; 47 u32 v32[2]; 48 } d = { dividend }; 49 u32 upper; 50 51 upper = d.v32[1]; 52 d.v32[1] = 0; 53 if (upper >= divisor) { 54 d.v32[1] = upper / divisor; 55 upper %= divisor; 56 } 57 asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) : 58 "rm" (divisor), "0" (d.v32[0]), "1" (upper)); 59 return d.v64; 60 } 61 #define div_u64_rem div_u64_rem 62 63 static inline u64 mul_u32_u32(u32 a, u32 b) 64 { 65 u32 high, low; 66 67 asm ("mull %[b]" : "=a" (low), "=d" (high) 68 : [a] "a" (a), [b] "rm" (b) ); 69 70 return low | ((u64)high) << 32; 71 } 72 #define mul_u32_u32 mul_u32_u32 73 74 /* 75 * __div64_32() is never called on x86, so prevent the 76 * generic definition from getting built. 77 */ 78 #define __div64_32 79 80 #else 81 # include <asm-generic/div64.h> 82 83 /* 84 * Will generate an #DE when the result doesn't fit u64, could fix with an 85 * __ex_table[] entry when it becomes an issue. 86 */ 87 static inline u64 mul_u64_u64_div_u64(u64 a, u64 mul, u64 div) 88 { 89 u64 q; 90 91 asm ("mulq %2; divq %3" : "=a" (q) 92 : "a" (a), "rm" (mul), "rm" (div) 93 : "rdx"); 94 95 return q; 96 } 97 #define mul_u64_u64_div_u64 mul_u64_u64_div_u64 98 99 static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 div) 100 { 101 return mul_u64_u64_div_u64(a, mul, div); 102 } 103 #define mul_u64_u32_div mul_u64_u32_div 104 105 #endif /* CONFIG_X86_32 */ 106 107 #endif /* _ASM_X86_DIV64_H */ 108