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/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _ASM_GENERIC_FUTEX_H #define _ASM_GENERIC_FUTEX_H #include <linux/futex.h> #include <linux/uaccess.h> #include <asm/errno.h> #ifndef CONFIG_SMP /* * The following implementation only for uniprocessor machines. * It relies on preempt_disable() ensuring mutual exclusion. * */ /** * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant * argument and comparison of the previous * futex value with another constant. * * @encoded_op: encoded operation to execute * @uaddr: pointer to user space address * * Return: * 0 - On success * -EFAULT - User access resulted in a page fault * -EAGAIN - Atomic operation was unable to complete due to contention * -ENOSYS - Operation not supported */ static inline int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr) { int oldval, ret; u32 tmp; preempt_disable(); ret = -EFAULT; if (unlikely(get_user(oldval, uaddr) != 0)) goto out_pagefault_enable; ret = 0; tmp = oldval; switch (op) { case FUTEX_OP_SET: tmp = oparg; break; case FUTEX_OP_ADD: tmp += oparg; break; case FUTEX_OP_OR: tmp |= oparg; break; case FUTEX_OP_ANDN: tmp &= ~oparg; break; case FUTEX_OP_XOR: tmp ^= oparg; break; default: ret = -ENOSYS; } if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0)) ret = -EFAULT; out_pagefault_enable: preempt_enable(); if (ret == 0) *oval = oldval; return ret; } /** * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the * uaddr with newval if the current value is * oldval. * @uval: pointer to store content of @uaddr * @uaddr: pointer to user space address * @oldval: old value * @newval: new value to store to @uaddr * * Return: * 0 - On success * -EFAULT - User access resulted in a page fault * -EAGAIN - Atomic operation was unable to complete due to contention * -ENOSYS - Function not implemented (only if !HAVE_FUTEX_CMPXCHG) */ static inline int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 oldval, u32 newval) { u32 val; preempt_disable(); if (unlikely(get_user(val, uaddr) != 0)) { preempt_enable(); return -EFAULT; } if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) { preempt_enable(); return -EFAULT; } *uval = val; preempt_enable(); return 0; } #else static inline int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr) { return -ENOSYS; } static inline int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 oldval, u32 newval) { return -ENOSYS; } #endif /* CONFIG_SMP */ #endif