crypto/cpu_aarch64_sysreg.cc

// Copyright 2023 The BoringSSL Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "internal.h"

// While Arm system registers are normally not available to userspace, FreeBSD
// expects userspace to simply read them. It traps the reads and fills in CPU
// capabilities.
#if defined(OPENSSL_AARCH64) && !defined(OPENSSL_STATIC_ARMCAP) && \
    (defined(ANDROID_BAREMETAL) || defined(OPENSSL_FREEBSD)) &&    \
    !defined(OPENSSL_NO_ASM)

#define ID_AA64PFR0_EL1_ADVSIMD 5

#define ID_AA64ISAR0_EL1_AES 1
#define ID_AA64ISAR0_EL1_SHA1 2
#define ID_AA64ISAR0_EL1_SHA2 3

#define NBITS_ID_FIELD 4

#define READ_SYSREG(name)                \
  ({                                     \
    uint64_t _r;                         \
    __asm__("mrs %0, " name : "=r"(_r)); \
    _r;                                  \
  })

static unsigned get_id_field(uint64_t reg, unsigned field) {
  return (reg >> (field * NBITS_ID_FIELD)) & ((1 << NBITS_ID_FIELD) - 1);
}

static int get_signed_id_field(uint64_t reg, unsigned field) {
  unsigned value = get_id_field(reg, field);
  if (value & (1 << (NBITS_ID_FIELD - 1))) {
    return (int)(value | (UINT64_MAX << NBITS_ID_FIELD));
  } else {
    return (int)value;
  }
}

static uint32_t read_armcap(void) {
  uint32_t armcap = ARMV7_NEON;

  uint64_t id_aa64pfr0_el1 = READ_SYSREG("id_aa64pfr0_el1");

  if (get_signed_id_field(id_aa64pfr0_el1, ID_AA64PFR0_EL1_ADVSIMD) < 0) {
    // If AdvSIMD ("NEON") is missing, don't report other features either.
    // This matches OpenSSL.
    return 0;
  }

  uint64_t id_aa64isar0_el1 = READ_SYSREG("id_aa64isar0_el1");

  unsigned aes = get_id_field(id_aa64isar0_el1, ID_AA64ISAR0_EL1_AES);
  if (aes > 0) {
    armcap |= ARMV8_AES;
  }
  if (aes > 1) {
    armcap |= ARMV8_PMULL;
  }

  unsigned sha1 = get_id_field(id_aa64isar0_el1, ID_AA64ISAR0_EL1_SHA1);
  if (sha1 > 0) {
    armcap |= ARMV8_SHA1;
  }

  unsigned sha2 = get_id_field(id_aa64isar0_el1, ID_AA64ISAR0_EL1_SHA2);
  if (sha2 > 0) {
    armcap |= ARMV8_SHA256;
  }
  if (sha2 > 1) {
    armcap |= ARMV8_SHA512;
  }

  return armcap;
}

void OPENSSL_cpuid_setup(void) { OPENSSL_armcap_P |= read_armcap(); }

#endif  // OPENSSL_AARCH64 && !OPENSSL_STATIC_ARMCAP &&
        // (ANDROID_BAREMETAL || OPENSSL_FREEBSD)