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