cpuid_arm.cpp

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/*
* Runtime CPU detection for ARM
* (C) 2009,2010,2013,2017 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/cpuid.h>

#if defined(BOTAN_TARGET_CPU_IS_ARM_FAMILY)

#if defined(BOTAN_TARGET_OS_IS_IOS)
  #include <sys/types.h>
  #include <sys/sysctl.h>

#else
  #include <botan/internal/os_utils.h>

#endif

#endif

namespace Botan {

#if defined(BOTAN_TARGET_CPU_IS_ARM_FAMILY)

#if defined(BOTAN_TARGET_OS_IS_IOS)

namespace {

uint64_t flags_by_ios_machine_type(const std::string& machine)
   {
   /*
   * This relies on a map of known machine names to features. This
   * will quickly grow out of date as new products are introduced, but
   * is apparently the best we can do for iOS.
   */

   struct version_info {
      std::string name;
      size_t min_version_neon;
      size_t min_version_armv8;
      };

   static const version_info min_versions[] = {
      { "iPhone", 2, 6 },
      { "iPad", 1, 4 },
      { "iPod", 4, 7 },
      { "AppleTV", 2, 5 },
   };

   if(machine.size() < 3)
      return 0;

   auto comma = machine.find(',');

   // Simulator, or something we don't know about
   if(comma == std::string::npos)
      return 0;

   std::string product = machine.substr(0, comma);

   size_t version = 0;
   size_t place = 1;
   while(product.size() > 1 && ::isdigit(product.back()))
      {
      const size_t digit = product.back() - '0';
      version += digit * place;
      place *= 10;
      product.pop_back();
      }

   if(version == 0)
      return 0;

   for(const version_info& info : min_versions)
      {
      if(info.name != product)
         continue;

      if(version >= info.min_version_armv8)
         {
         return CPUID::CPUID_ARM_AES_BIT |
                CPUID::CPUID_ARM_PMULL_BIT |
                CPUID::CPUID_ARM_SHA1_BIT |
                CPUID::CPUID_ARM_SHA2_BIT |
                CPUID::CPUID_ARM_NEON_BIT;
         }

      if(version >= info.min_version_neon)
         return CPUID::CPUID_ARM_NEON_BIT;
      }

   // Some other product we don't know about
   return 0;
   }

}

#endif

uint64_t CPUID::CPUID_Data::detect_cpu_features(size_t* cache_line_size)
   {
   uint64_t detected_features = 0;

#if defined(BOTAN_TARGET_OS_HAS_GETAUXVAL) || defined(BOTAN_TARGET_OS_HAS_ELF_AUX_INFO)
   /*
   * On systems with getauxval these bits should normally be defined
   * in bits/auxv.h but some buggy? glibc installs seem to miss them.
   * These following values are all fixed, for the Linux ELF format,
   * so we just hardcode them in ARM_hwcap_bit enum.
   */

   enum ARM_hwcap_bit {
#if defined(BOTAN_TARGET_ARCH_IS_ARM32)
      NEON_bit  = (1 << 12),
      AES_bit   = (1 << 0),
      PMULL_bit = (1 << 1),
      SHA1_bit  = (1 << 2),
      SHA2_bit  = (1 << 3),

      ARCH_hwcap_neon   = 16, // AT_HWCAP
      ARCH_hwcap_crypto = 26, // AT_HWCAP2
#elif defined(BOTAN_TARGET_ARCH_IS_ARM64)
      NEON_bit  = (1 << 1),
      AES_bit   = (1 << 3),
      PMULL_bit = (1 << 4),
      SHA1_bit  = (1 << 5),
      SHA2_bit  = (1 << 6),
      SHA3_bit  = (1 << 17),
      SM3_bit  = (1 << 18),
      SM4_bit  = (1 << 19),
      SHA2_512_bit  = (1 << 21),
      SVE_bit = (1 << 22),

      ARCH_hwcap_neon   = 16, // AT_HWCAP
      ARCH_hwcap_crypto = 16, // AT_HWCAP
#endif
   };

#if defined(AT_DCACHEBSIZE)
   // Exists only on Linux
   const unsigned long dcache_line = ::getauxval(AT_DCACHEBSIZE);

   // plausibility check
   if(dcache_line == 32 || dcache_line == 64 || dcache_line == 128)
      *cache_line_size = static_cast<size_t>(dcache_line);
#else
   BOTAN_UNUSED(cache_line_size);
#endif

   const unsigned long hwcap_neon = OS::get_auxval(ARM_hwcap_bit::ARCH_hwcap_neon);
   if(hwcap_neon & ARM_hwcap_bit::NEON_bit)
      detected_features |= CPUID::CPUID_ARM_NEON_BIT;

   /*
   On aarch64 this ends up calling getauxval twice with AT_HWCAP
   It doesn't seem worth optimizing this out, since getauxval is
   just reading a field in the ELF header.
   */
   const unsigned long hwcap_crypto = OS::get_auxval(ARM_hwcap_bit::ARCH_hwcap_crypto);
   if(hwcap_crypto & ARM_hwcap_bit::AES_bit)
      detected_features |= CPUID::CPUID_ARM_AES_BIT;
   if(hwcap_crypto & ARM_hwcap_bit::PMULL_bit)
      detected_features |= CPUID::CPUID_ARM_PMULL_BIT;
   if(hwcap_crypto & ARM_hwcap_bit::SHA1_bit)
      detected_features |= CPUID::CPUID_ARM_SHA1_BIT;
   if(hwcap_crypto & ARM_hwcap_bit::SHA2_bit)
      detected_features |= CPUID::CPUID_ARM_SHA2_BIT;

#if defined(BOTAN_TARGET_ARCH_IS_ARM64)
   if(hwcap_crypto & ARM_hwcap_bit::SHA3_bit)
      detected_features |= CPUID::CPUID_ARM_SHA3_BIT;
   if(hwcap_crypto & ARM_hwcap_bit::SM3_bit)
      detected_features |= CPUID::CPUID_ARM_SM3_BIT;
   if(hwcap_crypto & ARM_hwcap_bit::SM4_bit)
      detected_features |= CPUID::CPUID_ARM_SM4_BIT;
   if(hwcap_crypto & ARM_hwcap_bit::SHA2_512_bit)
      detected_features |= CPUID::CPUID_ARM_SHA2_512_BIT;
   if(hwcap_crypto & ARM_hwcap_bit::SVE_bit)
      detected_features |= CPUID::CPUID_ARM_SVE_BIT;
#endif

#elif defined(BOTAN_TARGET_OS_IS_IOS)

   char machine[64] = { 0 };
   size_t size = sizeof(machine) - 1;
   ::sysctlbyname("hw.machine", machine, &size, nullptr, 0);

   detected_features = flags_by_ios_machine_type(machine);

#elif defined(BOTAN_USE_GCC_INLINE_ASM) && defined(BOTAN_TARGET_ARCH_IS_ARM64)

   /*
   No getauxval API available, fall back on probe functions. We only
   bother with Aarch64 here to simplify the code and because going to
   extreme contortions to support detect NEON on devices that probably
   don't support it doesn't seem worthwhile.

   NEON registers v0-v7 are caller saved in Aarch64
   */

   auto neon_probe  = []() noexcept -> int { asm("and v0.16b, v0.16b, v0.16b"); return 1; };
   auto aes_probe   = []() noexcept -> int { asm(".word 0x4e284800"); return 1; };
   auto pmull_probe = []() noexcept -> int { asm(".word 0x0ee0e000"); return 1; };
   auto sha1_probe  = []() noexcept -> int { asm(".word 0x5e280800"); return 1; };
   auto sha2_probe  = []() noexcept -> int { asm(".word 0x5e282800"); return 1; };

   // Only bother running the crypto detection if we found NEON

   if(OS::run_cpu_instruction_probe(neon_probe) == 1)
      {
      detected_features |= CPUID::CPUID_ARM_NEON_BIT;

      if(OS::run_cpu_instruction_probe(aes_probe) == 1)
         detected_features |= CPUID::CPUID_ARM_AES_BIT;
      if(OS::run_cpu_instruction_probe(pmull_probe) == 1)
         detected_features |= CPUID::CPUID_ARM_PMULL_BIT;
      if(OS::run_cpu_instruction_probe(sha1_probe) == 1)
         detected_features |= CPUID::CPUID_ARM_SHA1_BIT;
      if(OS::run_cpu_instruction_probe(sha2_probe) == 1)
         detected_features |= CPUID::CPUID_ARM_SHA2_BIT;
      }

#endif

   return detected_features;
   }

#endif

}