OPENSSL_riscvcap(3) | OpenSSL | OPENSSL_riscvcap(3)

# NAME

OPENSSL_riscvcap - the RISC-V processor capabilities vector

# SYNOPSIS

     env OPENSSL_riscvcap=... <application>

# DESCRIPTION

libcrypto supports RISC-V instruction set extensions. These extensions are denoted by individual extension names in the capabilities vector. For Linux platform, when libcrypto is initialized, the results returned by the RISC-V Hardware Probing syscall (hwprobe) are stored in the vector. Otherwise all capabilities are disabled.

To override the set of instructions available to an application, you can set the OPENSSL_riscvcap environment variable before you start the application.

The environment variable is similar to the RISC-V ISA string defined in the RISC-V Instruction Set Manual. It is case insensitive. Though due to the limit of the environment variable parser inside libcrypto, an extension must be prefixed with an underscore to make it recognizable. This also applies to the Vector extension.

     OPENSSL_riscvcap="rv64gc_v_zba_zbb_zbs..."

Note that extension implication is currently not implemented. For example, when "rv64gc_b" is provided as the environment variable, zba/zbb/zbs would not be implied in the capability vector.

Currently only these extensions are recognized:

ZBA
  Address Generation

  Could be detected using hwprobe for Linux kernel >= 6.5

ZBB
  Basic bit-manipulation

  Could be detected using hwprobe for Linux kernel >= 6.5

ZBC
  Carry-less multiplication

  Could be detected using hwprobe for Linux kernel >= 6.8

ZBS
  Single-bit instructions

  Could be detected using hwprobe for Linux kernel >= 6.5

ZBKB
  Bit-manipulation for Cryptography

  Could be detected using hwprobe for Linux kernel >= 6.8

ZBKC
  Carry-less multiplication for Cryptography

  Could be detected using hwprobe for Linux kernel >= 6.8

ZBKX
  Crossbar permutations

  Could be detected using hwprobe for Linux kernel >= 6.8

ZKND
  NIST Suite: AES Decryption

  Could be detected using hwprobe for Linux kernel >= 6.8

ZKNE
  NIST Suite: AES Encryption

  Could be detected using hwprobe for Linux kernel >= 6.8

ZKNH
  NIST Suite: Hash Function Instructions

  Could be detected using hwprobe for Linux kernel >= 6.8

ZKSED
  ShangMi Suite: SM4 Block Cipher Instructions

  Could be detected using hwprobe for Linux kernel >= 6.8

ZKSH
  ShangMi Suite: SM3 Hash Function Instructions

  Could be detected using hwprobe for Linux kernel >= 6.8

ZKR
  Entropy Source Extension
ZKT
  Data Independent Execution Latency

  Could be detected using hwprobe for Linux kernel >= 6.8

V
  Vector Extension for Application Processors

  Could be detected using hwprobe for Linux kernel >= 6.5

ZVBB
  Vector Basic Bit-manipulation

  Could be detected using hwprobe for Linux kernel >= 6.8

ZVBC
  Vector Carryless Multiplication

  Could be detected using hwprobe for Linux kernel >= 6.8

ZVKB
  Vector Cryptography Bit-manipulation

  Could be detected using hwprobe for Linux kernel >= 6.8

ZVKG
  Vector GCM/GMAC

  Could be detected using hwprobe for Linux kernel >= 6.8

ZVKNED
  NIST Suite: Vector AES Block Cipher

  Could be detected using hwprobe for Linux kernel >= 6.8

ZVKNHA
  NIST Suite: Vector SHA-2 Secure Hash

  Could be detected using hwprobe for Linux kernel >= 6.8

ZVKNHB
  NIST Suite: Vector SHA-2 Secure Hash

  Could be detected using hwprobe for Linux kernel >= 6.8

ZVKSED
  ShangMi Suite: SM4 Block Cipher

  Could be detected using hwprobe for Linux kernel >= 6.8

ZVKSH
  ShangMi Suite: SM3 Secure Hash

  Could be detected using hwprobe for Linux kernel >= 6.8

# RETURN VALUES

Not available.

# EXAMPLES

Check currently detected capabilities

     $ openssl info -cpusettings
     OPENSSL_riscvcap=RV64GC_ZBA_ZBB_ZBC_ZBS_V vlen:256

Note: The first word in the displayed capabilities is the RISC-V base architecture value, which is derived from the compiler configuration. It is therefore not overridable by the environment variable. When the V extension is given the riscv_vlen value is always displayed, there is no way to override the riscv_vlen by the environment variable.

Disables all instruction set extensions:

     export OPENSSL_riscvcap="rv64gc"

Only enable the vector extension:

     export OPENSSL_riscvcap="rv64gc_v"

# COPYRIGHT

Copyright 2024 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

2026-06-09 | 3.5.7