1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Copyright (C) 2022-2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. 4 */ 5 #ifndef __ASM_VDSO_GETRANDOM_H 6 #define __ASM_VDSO_GETRANDOM_H 7 8 #ifndef __ASSEMBLY__ 9 10 #include <asm/unistd.h> 11 #include <asm/vvar.h> 12 13 /** 14 * getrandom_syscall - Invoke the getrandom() syscall. 15 * @buffer: Destination buffer to fill with random bytes. 16 * @len: Size of @buffer in bytes. 17 * @flags: Zero or more GRND_* flags. 18 * Returns: The number of random bytes written to @buffer, or a negative value indicating an error. 19 */ 20 static __always_inline ssize_t getrandom_syscall(void *buffer, size_t len, unsigned int flags) 21 { 22 long ret; 23 24 asm ("syscall" : "=a" (ret) : 25 "0" (__NR_getrandom), "D" (buffer), "S" (len), "d" (flags) : 26 "rcx", "r11", "memory"); 27 28 return ret; 29 } 30 31 #define __vdso_rng_data (VVAR(_vdso_rng_data)) 32 33 static __always_inline const struct vdso_rng_data *__arch_get_vdso_rng_data(void) 34 { 35 if (IS_ENABLED(CONFIG_TIME_NS) && __vdso_data->clock_mode == VDSO_CLOCKMODE_TIMENS) 36 return (void *)&__vdso_rng_data + ((void *)&__timens_vdso_data - (void *)&__vdso_data); 37 return &__vdso_rng_data; 38 } 39 40 /** 41 * __arch_chacha20_blocks_nostack - Generate ChaCha20 stream without using the stack. 42 * @dst_bytes: Destination buffer to hold @nblocks * 64 bytes of output. 43 * @key: 32-byte input key. 44 * @counter: 8-byte counter, read on input and updated on return. 45 * @nblocks: Number of blocks to generate. 46 * 47 * Generates a given positive number of blocks of ChaCha20 output with nonce=0, and does not write 48 * to any stack or memory outside of the parameters passed to it, in order to mitigate stack data 49 * leaking into forked child processes. 50 */ 51 extern void __arch_chacha20_blocks_nostack(u8 *dst_bytes, const u32 *key, u32 *counter, size_t nblocks); 52 53 #endif /* !__ASSEMBLY__ */ 54 55 #endif /* __ASM_VDSO_GETRANDOM_H */ 56