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