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 * -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 */
  30static inline int
  31arch_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
  69out_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 */
  94static inline int
  95futex_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
 118static inline int
 119arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
 120{
 121        return -ENOSYS;
 122}
 123
 124static inline int
 125futex_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