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