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70 lines
2.2 KiB
70 lines
2.2 KiB
// SPDX-License-Identifier: GPL-2.0 |
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// Copyright(c) 2018 Linus Torvalds. All rights reserved. |
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// Copyright(c) 2018 Alexei Starovoitov. All rights reserved. |
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// Copyright(c) 2018 Intel Corporation. All rights reserved. |
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#ifndef _LINUX_NOSPEC_H |
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#define _LINUX_NOSPEC_H |
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#include <linux/compiler.h> |
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#include <asm/barrier.h> |
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struct task_struct; |
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/** |
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* array_index_mask_nospec() - generate a ~0 mask when index < size, 0 otherwise |
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* @index: array element index |
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* @size: number of elements in array |
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* |
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* When @index is out of bounds (@index >= @size), the sign bit will be |
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* set. Extend the sign bit to all bits and invert, giving a result of |
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* zero for an out of bounds index, or ~0 if within bounds [0, @size). |
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*/ |
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#ifndef array_index_mask_nospec |
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static inline unsigned long array_index_mask_nospec(unsigned long index, |
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unsigned long size) |
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{ |
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/* |
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* Always calculate and emit the mask even if the compiler |
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* thinks the mask is not needed. The compiler does not take |
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* into account the value of @index under speculation. |
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*/ |
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OPTIMIZER_HIDE_VAR(index); |
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return ~(long)(index | (size - 1UL - index)) >> (BITS_PER_LONG - 1); |
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} |
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#endif |
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/* |
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* array_index_nospec - sanitize an array index after a bounds check |
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* |
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* For a code sequence like: |
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* |
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* if (index < size) { |
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* index = array_index_nospec(index, size); |
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* val = array[index]; |
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* } |
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* |
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* ...if the CPU speculates past the bounds check then |
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* array_index_nospec() will clamp the index within the range of [0, |
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* size). |
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*/ |
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#define array_index_nospec(index, size) \ |
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({ \ |
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typeof(index) _i = (index); \ |
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typeof(size) _s = (size); \ |
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unsigned long _mask = array_index_mask_nospec(_i, _s); \ |
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\ |
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BUILD_BUG_ON(sizeof(_i) > sizeof(long)); \ |
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BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \ |
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\ |
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(typeof(_i)) (_i & _mask); \ |
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}) |
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/* Speculation control prctl */ |
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int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which); |
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int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which, |
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unsigned long ctrl); |
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/* Speculation control for seccomp enforced mitigation */ |
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void arch_seccomp_spec_mitigate(struct task_struct *task); |
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#endif /* _LINUX_NOSPEC_H */
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