LXR linux/include/asm-generic/futex.h

   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 * <0 - On error
  27 */
  28static inline int
  29arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
  30{
  31        int oldval, ret;
  32        u32 tmp;
  33
  34        preempt_disable();
  35        pagefault_disable();
  36
  37        ret = -EFAULT;
  38        if (unlikely(get_user(oldval, uaddr) != 0))
  39                goto out_pagefault_enable;
  40
  41        ret = 0;
  42        tmp = oldval;
  43
  44        switch (op) {
  45        case FUTEX_OP_SET:
  46                tmp = oparg;
  47                break;
  48        case FUTEX_OP_ADD:
  49                tmp += oparg;
  50                break;
  51        case FUTEX_OP_OR:
  52                tmp |= oparg;
  53                break;
  54        case FUTEX_OP_ANDN:
  55                tmp &= ~oparg;
  56                break;
  57        case FUTEX_OP_XOR:
  58                tmp ^= oparg;
  59                break;
  60        default:
  61                ret = -ENOSYS;
  62        }
  63
  64        if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
  65                ret = -EFAULT;
  66
  67out_pagefault_enable:
  68        pagefault_enable();
  69        preempt_enable();
  70
  71        if (ret == 0)
  72                *oval = oldval;
  73
  74        return ret;
  75}
  76
  77/**
  78 * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
  79 *                              uaddr with newval if the current value is
  80 *                              oldval.
  81 * @uval:       pointer to store content of @uaddr
  82 * @uaddr:      pointer to user space address
  83 * @oldval:     old value
  84 * @newval:     new value to store to @uaddr
  85 *
  86 * Return:
  87 * 0 - On success
  88 * <0 - On error
  89 */
  90static inline int
  91futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
  92                              u32 oldval, u32 newval)
  93{
  94        u32 val;
  95
  96        preempt_disable();
  97        if (unlikely(get_user(val, uaddr) != 0)) {
  98                preempt_enable();
  99                return -EFAULT;
 100        }
 101
 102        if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
 103                preempt_enable();
 104                return -EFAULT;
 105        }
 106
 107        *uval = val;
 108        preempt_enable();
 109
 110        return 0;
 111}
 112
 113#else
 114static inline int
 115arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
 116{
 117        int oldval = 0, ret;
 118
 119        pagefault_disable();
 120
 121        switch (op) {
 122        case FUTEX_OP_SET:
 123        case FUTEX_OP_ADD:
 124        case FUTEX_OP_OR:
 125        case FUTEX_OP_ANDN:
 126        case FUTEX_OP_XOR:
 127        default:
 128                ret = -ENOSYS;
 129        }
 130
 131        pagefault_enable();
 132
 133        if (!ret)
 134                *oval = oldval;
 135
 136        return ret;
 137}
 138
 139static inline int
 140futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 141                              u32 oldval, u32 newval)
 142{
 143        return -ENOSYS;
 144}
 145
 146#endif /* CONFIG_SMP */
 147#endif
 148