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 CONFIG_SMP 10 /* 11 * The following implementation only for uniprocessor machines. 12 * It relies on preempt_disable() ensuring mutual exclusion. 13 * 14 */ 15 16 /** 17 * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant 18 * argument and comparison of the previous 19 * futex value with another constant. 20 * 21 * @encoded_op: encoded operation to execute 22 * @uaddr: pointer to user space address 23 * 24 * Return: 25 * 0 - On success 26 * -EFAULT - User access resulted in a page fault 27 * -EAGAIN - Atomic operation was unable to complete due to contention 28 * -ENOSYS - Operation not supported 29 */ 30 static inline int 31 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr) 32 { 33 int oldval, ret; 34 u32 tmp; 35 36 preempt_disable(); 37 pagefault_disable(); 38 39 ret = -EFAULT; 40 if (unlikely(get_user(oldval, uaddr) != 0)) 41 goto out_pagefault_enable; 42 43 ret = 0; 44 tmp = oldval; 45 46 switch (op) { 47 case FUTEX_OP_SET: 48 tmp = oparg; 49 break; 50 case FUTEX_OP_ADD: 51 tmp += oparg; 52 break; 53 case FUTEX_OP_OR: 54 tmp |= oparg; 55 break; 56 case FUTEX_OP_ANDN: 57 tmp &= ~oparg; 58 break; 59 case FUTEX_OP_XOR: 60 tmp ^= oparg; 61 break; 62 default: 63 ret = -ENOSYS; 64 } 65 66 if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0)) 67 ret = -EFAULT; 68 69 out_pagefault_enable: 70 pagefault_enable(); 71 preempt_enable(); 72 73 if (ret == 0) 74 *oval = oldval; 75 76 return ret; 77 } 78 79 /** 80 * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the 81 * uaddr with newval if the current value is 82 * oldval. 83 * @uval: pointer to store content of @uaddr 84 * @uaddr: pointer to user space address 85 * @oldval: old value 86 * @newval: new value to store to @uaddr 87 * 88 * Return: 89 * 0 - On success 90 * -EFAULT - User access resulted in a page fault 91 * -EAGAIN - Atomic operation was unable to complete due to contention 92 * -ENOSYS - Function not implemented (only if !HAVE_FUTEX_CMPXCHG) 93 */ 94 static inline int 95 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, 96 u32 oldval, u32 newval) 97 { 98 u32 val; 99 100 preempt_disable(); 101 if (unlikely(get_user(val, uaddr) != 0)) { 102 preempt_enable(); 103 return -EFAULT; 104 } 105 106 if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) { 107 preempt_enable(); 108 return -EFAULT; 109 } 110 111 *uval = val; 112 preempt_enable(); 113 114 return 0; 115 } 116 117 #else 118 static inline int 119 arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr) 120 { 121 return -ENOSYS; 122 } 123 124 static inline int 125 futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, 126 u32 oldval, u32 newval) 127 { 128 return -ENOSYS; 129 } 130 131 #endif /* CONFIG_SMP */ 132 #endif 133