diff --git a/arch/riscv/include/asm/archrandom.h b/arch/riscv/include/asm/archrandom.h new file mode 100644 index 000000000000..5345360adfb9 --- /dev/null +++ b/arch/riscv/include/asm/archrandom.h @@ -0,0 +1,72 @@ +/* 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 +#include + +#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 */ diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h index 306a19a5509c..510014051f5d 100644 --- a/arch/riscv/include/asm/csr.h +++ b/arch/riscv/include/asm/csr.h @@ -411,6 +411,15 @@ #define CSR_VTYPE 0xc21 #define CSR_VLENB 0xc22 +/* Scalar Crypto Extension - Entropy */ +#define CSR_SEED 0x015 +#define SEED_OPST_MASK _AC(0xC0000000, UL) +#define SEED_OPST_BIST _AC(0x00000000, UL) +#define SEED_OPST_WAIT _AC(0x40000000, UL) +#define SEED_OPST_ES16 _AC(0x80000000, UL) +#define SEED_OPST_DEAD _AC(0xC0000000, UL) +#define SEED_ENTROPY_MASK _AC(0xFFFF, UL) + #ifdef CONFIG_RISCV_M_MODE # define CSR_STATUS CSR_MSTATUS # define CSR_IE CSR_MIE