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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_H7#define _VDSO_GETRANDOM_H8 9#include <linux/types.h>10 11#define CHACHA_KEY_SIZE 3212#define CHACHA_BLOCK_SIZE 6413 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 full22 * ChaCha20 blocks in size, so that @batch and @key can be filled23 * together.24 *25 * @generation: Snapshot of @rng_info->generation in the vDSO data page at26 * 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 thread31 * due to signal handlers.32 */33struct 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/**47 * __arch_chacha20_blocks_nostack - Generate ChaCha20 stream without using the stack.48 * @dst_bytes: Destination buffer to hold @nblocks * 64 bytes of output.49 * @key: 32-byte input key.50 * @counter: 8-byte counter, read on input and updated on return.51 * @nblocks: Number of blocks to generate.52 *53 * Generates a given positive number of blocks of ChaCha20 output with nonce=0, and does not write54 * to any stack or memory outside of the parameters passed to it, in order to mitigate stack data55 * leaking into forked child processes.56 */57extern void __arch_chacha20_blocks_nostack(u8 *dst_bytes, const u32 *key, u32 *counter, size_t nblocks);58 59/**60 * __vdso_getrandom - Architecture-specific vDSO implementation of getrandom() syscall.61 * @buffer: Passed to __cvdso_getrandom().62 * @len: Passed to __cvdso_getrandom().63 * @flags: Passed to __cvdso_getrandom().64 * @opaque_state: Passed to __cvdso_getrandom().65 * @opaque_len: Passed to __cvdso_getrandom();66 *67 * This function is implemented by making a single call to to __cvdso_getrandom(), whose68 * documentation may be consulted for more information.69 *70 * Returns: The return value of __cvdso_getrandom().71 */72extern ssize_t __vdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len);73 74#endif /* _VDSO_GETRANDOM_H */75