1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Copyright (C) 2022-2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
4 */
5
6 #ifndef _VDSO_GETRANDOM_H
7 #define _VDSO_GETRANDOM_H
8
9 #include <linux/types.h>
10
11 #define CHACHA_KEY_SIZE 32
12 #define CHACHA_BLOCK_SIZE 64
13
14 /**
15 * struct vgetrandom_state - State used by vDSO getrandom().
16 *
17 * @batch: One and a half ChaCha20 blocks of buffered RNG output.
18 *
19 * @key: Key to be used for generating next batch.
20 *
21 * @batch_key: Union of the prior two members, which is exactly two full
22 * ChaCha20 blocks in size, so that @batch and @key can be filled
23 * together.
24 *
25 * @generation: Snapshot of @rng_info->generation in the vDSO data page at
26 * the time @key was generated.
27 *
28 * @pos: Offset into @batch of the next available random byte.
29 *
30 * @in_use: Reentrancy guard for reusing a state within the same thread
31 * due to signal handlers.
32 */
33 struct vgetrandom_state {
34 union {
35 struct {
36 u8 batch[CHACHA_BLOCK_SIZE * 3 / 2];
37 u32 key[CHACHA_KEY_SIZE / sizeof(u32)];
38 };
39 u8 batch_key[CHACHA_BLOCK_SIZE * 2];
40 };
41 u64 generation;
42 u8 pos;
43 bool in_use;
44 };
45
46 #endif /* _VDSO_GETRANDOM_H */
47
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