73 lines
1.5 KiB
C
73 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Kernel interface for the RISCV arch_random_* functions
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*
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* Copyright (c) 2023 Rivos Inc.
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*
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*/
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#ifndef ASM_RISCV_ARCHRANDOM_H
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#define ASM_RISCV_ARCHRANDOM_H
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#include <asm/csr.h>
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#include <asm/processor.h>
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#define SEED_RETRY_LOOPS 100
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static inline bool __must_check csr_seed_long(unsigned long *v)
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{
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unsigned int retry = SEED_RETRY_LOOPS, valid_seeds = 0;
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const int needed_seeds = sizeof(long) / sizeof(u16);
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u16 *entropy = (u16 *)v;
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do {
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/*
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* The SEED CSR must be accessed with a read-write instruction.
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*/
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unsigned long csr_seed = csr_swap(CSR_SEED, 0);
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unsigned long opst = csr_seed & SEED_OPST_MASK;
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switch (opst) {
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case SEED_OPST_ES16:
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entropy[valid_seeds++] = csr_seed & SEED_ENTROPY_MASK;
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if (valid_seeds == needed_seeds)
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return true;
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break;
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case SEED_OPST_DEAD:
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pr_err_once("archrandom: Unrecoverable error\n");
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return false;
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case SEED_OPST_BIST:
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case SEED_OPST_WAIT:
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default:
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cpu_relax();
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continue;
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}
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} while (--retry);
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return false;
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}
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static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
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{
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return 0;
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}
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static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
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{
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if (!max_longs)
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return 0;
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/*
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* If Zkr is supported and csr_seed_long succeeds, we return one long
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* worth of entropy.
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*/
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if (riscv_has_extension_likely(RISCV_ISA_EXT_ZKR) && csr_seed_long(v))
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return 1;
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return 0;
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}
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#endif /* ASM_RISCV_ARCHRANDOM_H */
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