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