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Dan Williams478742c2018-01-29 17:02:22 -08001// SPDX-License-Identifier: GPL-2.0
2// Copyright(c) 2018 Linus Torvalds. All rights reserved.
3// Copyright(c) 2018 Alexei Starovoitov. All rights reserved.
4// Copyright(c) 2018 Intel Corporation. All rights reserved.
5
6#ifndef _LINUX_NOSPEC_H
7#define _LINUX_NOSPEC_H
Dan Williams2e192772018-02-16 13:20:54 -08008#include <asm/barrier.h>
Dan Williams478742c2018-01-29 17:02:22 -08009
Kees Cook7d1254a2018-05-01 15:19:04 -070010struct task_struct;
11
Dave Hansene0fbff12023-02-21 12:30:15 -080012#ifndef barrier_nospec
13# define barrier_nospec() do { } while (0)
14#endif
15
Dan Williams478742c2018-01-29 17:02:22 -080016/**
17 * array_index_mask_nospec() - generate a ~0 mask when index < size, 0 otherwise
18 * @index: array element index
19 * @size: number of elements in array
20 *
21 * When @index is out of bounds (@index >= @size), the sign bit will be
22 * set. Extend the sign bit to all bits and invert, giving a result of
23 * zero for an out of bounds index, or ~0 if within bounds [0, @size).
24 */
25#ifndef array_index_mask_nospec
26static inline unsigned long array_index_mask_nospec(unsigned long index,
27 unsigned long size)
28{
29 /*
Dan Williams478742c2018-01-29 17:02:22 -080030 * Always calculate and emit the mask even if the compiler
31 * thinks the mask is not needed. The compiler does not take
32 * into account the value of @index under speculation.
33 */
34 OPTIMIZER_HIDE_VAR(index);
35 return ~(long)(index | (size - 1UL - index)) >> (BITS_PER_LONG - 1);
36}
37#endif
38
39/*
40 * array_index_nospec - sanitize an array index after a bounds check
41 *
42 * For a code sequence like:
43 *
44 * if (index < size) {
45 * index = array_index_nospec(index, size);
46 * val = array[index];
47 * }
48 *
49 * ...if the CPU speculates past the bounds check then
50 * array_index_nospec() will clamp the index within the range of [0,
51 * size).
52 */
53#define array_index_nospec(index, size) \
54({ \
55 typeof(index) _i = (index); \
56 typeof(size) _s = (size); \
Dan Williamsbebe3992018-02-16 13:20:42 -080057 unsigned long _mask = array_index_mask_nospec(_i, _s); \
Dan Williams478742c2018-01-29 17:02:22 -080058 \
59 BUILD_BUG_ON(sizeof(_i) > sizeof(long)); \
60 BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \
61 \
Rasmus Villemoes656772c2018-02-16 13:20:48 -080062 (typeof(_i)) (_i & _mask); \
Dan Williams478742c2018-01-29 17:02:22 -080063})
Thomas Gleixner33f6a062018-04-29 15:20:11 +020064
65/* Speculation control prctl */
Kees Cook7d1254a2018-05-01 15:19:04 -070066int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which);
67int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
68 unsigned long ctrl);
Thomas Gleixner61dfdc12018-05-04 15:12:06 +020069/* Speculation control for seccomp enforced mitigation */
70void arch_seccomp_spec_mitigate(struct task_struct *task);
Thomas Gleixner33f6a062018-04-29 15:20:11 +020071
Dan Williams478742c2018-01-29 17:02:22 -080072#endif /* _LINUX_NOSPEC_H */