1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_GENERIC_FUTEX_H 3 #define _ASM_GENERIC_FUTEX_H 4 5 #include <linux/futex.h> 6 #include <linux/uaccess.h> 7 #include <asm/errno.h> 8 9 #ifndef futex_atomic_cmpxchg_inatomic 10 #ifndef CONFIG_SMP 11 /* 12 * The following implementation only for uniprocessor machines. 13 * It relies on preempt_disable() ensuring mutual exclusion. 14 * 15 */ 16 #define futex_atomic_cmpxchg_inatomic(uval, uaddr, oldval, newval) \ 17 futex_atomic_cmpxchg_inatomic_local(uval, uaddr, oldval, newval) 18 #define arch_futex_atomic_op_inuser(op, oparg, oval, uaddr) \ 19 futex_atomic_op_inuser_local(op, oparg, oval, uaddr) 20 #endif /* CONFIG_SMP */ 21 #endif 22 23 /** 24 * futex_atomic_op_inuser_local() - Atomic arithmetic operation with constant 25 * argument and comparison of the previous 26 * futex value with another constant. 27 * 28 * @op: operation to execute 29 * @oparg: argument of the operation 30 * @oval: previous value at @uaddr on successful return 31 * @uaddr: pointer to user space address 32 * 33 * Return: 34 * 0 - On success 35 * -EFAULT - User access resulted in a page fault 36 * -EAGAIN - Atomic operation was unable to complete due to contention 37 * -ENOSYS - Operation not supported 38 */ 39 static inline int 40 futex_atomic_op_inuser_local(int op, u32 oparg, int *oval, u32 __user *uaddr) 41 { 42 int oldval, ret; 43 u32 tmp; 44 45 preempt_disable(); 46 47 ret = -EFAULT; 48 if (unlikely(get_user(oldval, uaddr) != 0)) 49 goto out_pagefault_enable; 50 51 ret = 0; 52 tmp = oldval; 53 54 switch (op) { 55 case FUTEX_OP_SET: 56 tmp = oparg; 57 break; 58 case FUTEX_OP_ADD: 59 tmp += oparg; 60 break; 61 case FUTEX_OP_OR: 62 tmp |= oparg; 63 break; 64 case FUTEX_OP_ANDN: 65 tmp &= ~oparg; 66 break; 67 case FUTEX_OP_XOR: 68 tmp ^= oparg; 69 break; 70 default: 71 ret = -ENOSYS; 72 } 73 74 if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0)) 75 ret = -EFAULT; 76 77 out_pagefault_enable: 78 preempt_enable(); 79 80 if (ret == 0) 81 *oval = oldval; 82 83 return ret; 84 } 85 86 /** 87 * futex_atomic_cmpxchg_inatomic_local() - Compare and exchange the content of the 88 * uaddr with newval if the current value is 89 * oldval. 90 * @uval: pointer to store content of @uaddr 91 * @uaddr: pointer to user space address 92 * @oldval: old value 93 * @newval: new value to store to @uaddr 94 * 95 * Return: 96 * 0 - On success 97 * -EFAULT - User access resulted in a page fault 98 * -EAGAIN - Atomic operation was unable to complete due to contention 99 */ 100 static inline int 101 futex_atomic_cmpxchg_inatomic_local(u32 *uval, u32 __user *uaddr, 102 u32 oldval, u32 newval) 103 { 104 u32 val; 105 106 preempt_disable(); 107 if (unlikely(get_user(val, uaddr) != 0)) { 108 preempt_enable(); 109 return -EFAULT; 110 } 111 112 if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) { 113 preempt_enable(); 114 return -EFAULT; 115 } 116 117 *uval = val; 118 preempt_enable(); 119 120 return 0; 121 } 122 123 #endif 124