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Without a prototype, we'll have to add a prototype for each architecture implementing vDSO getrandom. As most architectures will likely have the vDSO getrandom implemented in a near future, and we'd like to keep the declarations compatible everywhere (to ease the libc implementor work), we should really just have one copy of the prototype. This also is what's already done inside of include/vdso/gettime.h for those vDSO functions, so this continues that convention. Suggested-by: Huacai Chen <chenhuacai@kernel.org> Signed-off-by: Xi Ruoyao <xry111@xry111.site> Acked-by: Huacai Chen <chenhuacai@kernel.org> [Jason: rewrite docbook comment for prototype.] Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
75 lines
2.4 KiB
C
75 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2022-2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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*/
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#ifndef _VDSO_GETRANDOM_H
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#define _VDSO_GETRANDOM_H
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#include <linux/types.h>
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#define CHACHA_KEY_SIZE 32
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#define CHACHA_BLOCK_SIZE 64
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/**
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* struct vgetrandom_state - State used by vDSO getrandom().
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*
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* @batch: One and a half ChaCha20 blocks of buffered RNG output.
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*
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* @key: Key to be used for generating next batch.
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*
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* @batch_key: Union of the prior two members, which is exactly two full
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* ChaCha20 blocks in size, so that @batch and @key can be filled
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* together.
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*
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* @generation: Snapshot of @rng_info->generation in the vDSO data page at
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* the time @key was generated.
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*
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* @pos: Offset into @batch of the next available random byte.
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*
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* @in_use: Reentrancy guard for reusing a state within the same thread
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* due to signal handlers.
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*/
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struct vgetrandom_state {
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union {
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struct {
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u8 batch[CHACHA_BLOCK_SIZE * 3 / 2];
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u32 key[CHACHA_KEY_SIZE / sizeof(u32)];
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};
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u8 batch_key[CHACHA_BLOCK_SIZE * 2];
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};
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u64 generation;
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u8 pos;
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bool in_use;
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};
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/**
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* __arch_chacha20_blocks_nostack - Generate ChaCha20 stream without using the stack.
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* @dst_bytes: Destination buffer to hold @nblocks * 64 bytes of output.
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* @key: 32-byte input key.
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* @counter: 8-byte counter, read on input and updated on return.
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* @nblocks: Number of blocks to generate.
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*
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* Generates a given positive number of blocks of ChaCha20 output with nonce=0, and does not write
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* to any stack or memory outside of the parameters passed to it, in order to mitigate stack data
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* leaking into forked child processes.
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*/
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extern void __arch_chacha20_blocks_nostack(u8 *dst_bytes, const u32 *key, u32 *counter, size_t nblocks);
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/**
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* __vdso_getrandom - Architecture-specific vDSO implementation of getrandom() syscall.
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* @buffer: Passed to __cvdso_getrandom().
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* @len: Passed to __cvdso_getrandom().
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* @flags: Passed to __cvdso_getrandom().
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* @opaque_state: Passed to __cvdso_getrandom().
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* @opaque_len: Passed to __cvdso_getrandom();
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*
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* This function is implemented by making a single call to to __cvdso_getrandom(), whose
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* documentation may be consulted for more information.
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*
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* Returns: The return value of __cvdso_getrandom().
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*/
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extern ssize_t __vdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len);
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#endif /* _VDSO_GETRANDOM_H */
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