Merge GH #843 Refactor CPUID impl, add ARM feature detection

6 files changed, 463 insertions, 159 deletions

diff --git a/src/build-data/os/android.txt b/src/build-data/os/android.txt
index 50d97fd8f..db06bab1d 100644
--- a/src/build-data/os/android.txt
+++ b/src/build-data/os/android.txt
@@ -7,6 +7,7 @@ clock_gettime
 gettimeofday
 posix_mlock
 gmtime_r
+getauxval
 dlopen
 readdir
 threads
diff --git a/src/build-data/os/linux.txt b/src/build-data/os/linux.txt
index 6bd81f7f2..59f995fc2 100644
--- a/src/build-data/os/linux.txt
+++ b/src/build-data/os/linux.txt
@@ -8,6 +8,7 @@ gettimeofday
 posix_mlock
 gmtime_r
 dlopen
+getauxval
 readdir
 timegm
 sockets
diff --git a/src/lib/utils/cpuid.cpp b/src/lib/utils/cpuid.cpp
index 428ca2715..325421d71 100644
--- a/src/lib/utils/cpuid.cpp
+++ b/src/lib/utils/cpuid.cpp
@@ -1,6 +1,6 @@
 /*
 * Runtime CPU detection
-* (C) 2009-2010,2013 Jack Lloyd
+* (C) 2009,2010,2013,2017 Jack Lloyd
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
@@ -14,59 +14,66 @@
 
 #if defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY)
 
+/*
+* On Darwin and OpenBSD ppc, use sysctl to detect AltiVec
+*/
 #if defined(BOTAN_TARGET_OS_IS_DARWIN)
   #include <sys/sysctl.h>
-#endif
-
-#if defined(BOTAN_TARGET_OS_IS_OPENBSD)
+#elif defined(BOTAN_TARGET_OS_IS_OPENBSD)
   #include <sys/param.h>
   #include <sys/sysctl.h>
   #include <machine/cpu.h>
 #endif
 
+#elif defined(BOTAN_TARGET_CPU_IS_ARM_FAMILY)
+
+/*
+* On ARM, use getauxval if available, otherwise fall back to
+* running probe functions with a SIGILL handler.
+*/
+#if defined(BOTAN_TARGET_OS_HAS_GETAUXVAL)
+  #include <sys/auxv.h>
 #endif
 
-#if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
+#include <botan/internal/os_utils.h>
 
-#if defined(BOTAN_BUILD_COMPILER_IS_MSVC)
+#elif defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
 
-#include <intrin.h>
+#if defined(BOTAN_BUILD_COMPILER_IS_MSVC)
 
-#define X86_CPUID(type, out) do { __cpuid((int*)out, type); } while(0)
-#define X86_CPUID_SUBLEVEL(type, level, out) do { __cpuidex((int*)out, type, level); } while(0)
+  #include <intrin.h>
+  #define X86_CPUID(type, out) do { __cpuid((int*)out, type); } while(0)
+  #define X86_CPUID_SUBLEVEL(type, level, out) do { __cpuidex((int*)out, type, level); } while(0)
 
 #elif defined(BOTAN_BUILD_COMPILER_IS_INTEL)
 
-#include <ia32intrin.h>
-
-#define X86_CPUID(type, out) do { __cpuid(out, type); } while(0)
-#define X86_CPUID_SUBLEVEL(type, level, out) do { __cpuidex((int*)out, type, level); } while(0)
+  #include <ia32intrin.h>
+  #define X86_CPUID(type, out) do { __cpuid(out, type); } while(0)
+  #define X86_CPUID_SUBLEVEL(type, level, out) do { __cpuidex((int*)out, type, level); } while(0)
 
 #elif defined(BOTAN_TARGET_ARCH_IS_X86_64) && defined(BOTAN_USE_GCC_INLINE_ASM)
 
-#define X86_CPUID(type, out)                                                    \
-   asm("cpuid\n\t" : "=a" (out[0]), "=b" (out[1]), "=c" (out[2]), "=d" (out[3]) \
-       : "0" (type))
+  #define X86_CPUID(type, out)                                                    \
+     asm("cpuid\n\t" : "=a" (out[0]), "=b" (out[1]), "=c" (out[2]), "=d" (out[3]) \
+         : "0" (type))
 
-#define X86_CPUID_SUBLEVEL(type, level, out)                                    \
-   asm("cpuid\n\t" : "=a" (out[0]), "=b" (out[1]), "=c" (out[2]), "=d" (out[3]) \
-       : "0" (type), "2" (level))
+  #define X86_CPUID_SUBLEVEL(type, level, out)                                    \
+     asm("cpuid\n\t" : "=a" (out[0]), "=b" (out[1]), "=c" (out[2]), "=d" (out[3]) \
+         : "0" (type), "2" (level))
 
 #elif defined(BOTAN_BUILD_COMPILER_IS_GCC) || defined(BOTAN_BUILD_COMPILER_IS_CLANG)
 
-#include <cpuid.h>
+  #include <cpuid.h>
 
-#define X86_CPUID(type, out) do { __get_cpuid(type, out, out+1, out+2, out+3); } while(0)
+  #define X86_CPUID(type, out) do { __get_cpuid(type, out, out+1, out+2, out+3); } while(0)
 
-#define X86_CPUID_SUBLEVEL(type, level, out) \
-   do { __cpuid_count(type, level, out[0], out[1], out[2], out[3]); } while(0)
+  #define X86_CPUID_SUBLEVEL(type, level, out) \
+     do { __cpuid_count(type, level, out[0], out[1], out[2], out[3]); } while(0)
 
 #else
-
-#warning "No way of calling cpuid for this compiler"
-
-#define X86_CPUID(type, out) do { clear_mem(out, 4); } while(0)
-#define X86_CPUID_SUBLEVEL(type, level, out) do { clear_mem(out, 4); } while(0)
+  #warning "No way of calling cpuid for this compiler"
+  #define X86_CPUID(type, out) do { clear_mem(out, 4); } while(0)
+  #define X86_CPUID_SUBLEVEL(type, level, out) do { clear_mem(out, 4); } while(0)
 
 #endif
 
@@ -74,18 +81,22 @@
 
 namespace Botan {
 
-uint64_t CPUID::g_processor_flags[2] = { 0, 0 };
+uint64_t CPUID::g_processor_features = 0;
 size_t CPUID::g_cache_line_size = BOTAN_TARGET_CPU_DEFAULT_CACHE_LINE_SIZE;
-bool CPUID::g_initialized = false;
 bool CPUID::g_little_endian = false;
 
 namespace {
 
 #if defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY)
 
-bool altivec_check_sysctl()
+/*
+* PowerPC specific block: check for AltiVec using either
+* sysctl or by reading processor version number register.
+*/
+uint64_t powerpc_detect_cpu_featutures()
    {
 #if defined(BOTAN_TARGET_OS_IS_DARWIN) || defined(BOTAN_TARGET_OS_IS_OPENBSD)
+   // On Darwin/OS X and OpenBSD, use sysctl
 
 #if defined(BOTAN_TARGET_OS_IS_OPENBSD)
    int sels[2] = { CTL_MACHDEP, CPU_ALTIVEC };
@@ -98,18 +109,9 @@ bool altivec_check_sysctl()
    int error = sysctl(sels, 2, &vector_type, &length, NULL, 0);
 
    if(error == 0 && vector_type > 0)
-      return true;
-#endif
-
-   return false;
-   }
-
-bool altivec_check_pvr_emul()
-   {
-   bool altivec_capable = false;
-
-#if defined(BOTAN_TARGET_OS_IS_LINUX) || defined(BOTAN_TARGET_OS_IS_NETBSD)
+      return (1ULL << CPUID::CPUID_ALTIVEC_BIT);
 
+#elif defined(BOTAN_TARGET_OS_IS_LINUX) || defined(BOTAN_TARGET_OS_IS_NETBSD)
    /*
    On PowerPC, MSR 287 is PVR, the Processor Version Number
    Normally it is only accessible to ring 0, but Linux and NetBSD
@@ -119,6 +121,14 @@ bool altivec_check_pvr_emul()
    PearPC and Linux sources, mostly.
    */
 
+   uint32_t pvr = 0;
+
+   // TODO: we could run inside SIGILL handler block
+   asm volatile("mfspr %0, 287" : "=r" (pvr));
+
+   // Top 16 bit suffice to identify model
+   pvr >>= 16;
+
    const uint16_t PVR_G4_7400  = 0x000C;
    const uint16_t PVR_G5_970   = 0x0039;
    const uint16_t PVR_G5_970FX = 0x003C;
@@ -129,29 +139,197 @@ bool altivec_check_pvr_emul()
    const uint16_t PVR_POWER8   = 0x004B;
    const uint16_t PVR_CELL_PPU = 0x0070;
 
-   // Motorola produced G4s with PVR 0x800[0123C] (at least)
-   const uint16_t PVR_G4_74xx_24  = 0x800;
+   if(pvr == PVR_G4_7400 ||
+      pvr == PVR_G5_970 || pvr == PVR_G5_970FX ||
+      pvr == PVR_G5_970MP || pvr == PVR_G5_970GX ||
+      pvr == PVR_POWER6 || pvr == PVR_POWER7 || pvr == PVR_POWER8 ||
+      pvr == PVR_CELL_PPU)
+      {
+      return (1ULL << CPUID::CPUID_ALTIVEC_BIT);
+      }
+#else
+  #warning "No PowerPC feature detection available for this platform"
+#endif
 
-   uint32_t pvr = 0;
+   return 0;
+   }
 
-   asm volatile("mfspr %0, 287" : "=r" (pvr));
+#elif defined(BOTAN_TARGET_CPU_IS_ARM_FAMILY)
 
-   // Top 16 bit suffice to identify model
-   pvr >>= 16;
+uint64_t arm_detect_cpu_features(size_t* cache_line_size)
+   {
+   uint64_t detected_features = 0;
+   *cache_line_size = BOTAN_TARGET_CPU_DEFAULT_CACHE_LINE_SIZE;
+
+#if defined(BOTAN_TARGET_OS_HAS_GETAUXVAL)
+   errno = 0;
+
+   /*
+   * 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),
+
+      ARCH_hwcap_neon   = 16, // AT_HWCAP
+      ARCH_hwcap_crypto = 16, // AT_HWCAP
+#endif
+   };
+
+   const unsigned long hwcap_neon = ::getauxval(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
+   This doesn't seem worth optimizing this out, since getauxval is
+   just reading a field in the ELF header.
+   */
+   const unsigned long hwcap_crypto = ::getauxval(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;
+
+   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);
+#endif
+
+   // TODO: probe functions
+
+   return detected_features;
+   }
+
+#elif defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
+
+uint64_t x86_detect_cpu_features(size_t* cache_line_size)
+   {
+   uint64_t features_detected = 0;
+   uint32_t cpuid[4] = { 0 };
+
+   // CPUID 0: vendor identification, max sublevel
+   X86_CPUID(0, cpuid);
+
+   const uint32_t max_supported_sublevel = cpuid[0];
+
+   const uint32_t INTEL_CPUID[3] = { 0x756E6547, 0x6C65746E, 0x49656E69 };
+   const uint32_t AMD_CPUID[3] = { 0x68747541, 0x444D4163, 0x69746E65 };
+   const bool is_intel = same_mem(cpuid + 1, INTEL_CPUID, 3);
+   const bool is_amd = same_mem(cpuid + 1, AMD_CPUID, 3);
+
+   if(max_supported_sublevel >= 1)
+      {
+      // CPUID 1: feature bits
+      X86_CPUID(1, cpuid);
+      const uint64_t flags0 = (static_cast<uint64_t>(cpuid[2]) << 32) | cpuid[3];
+
+      enum x86_CPUID_1_bits : uint64_t {
+         RDTSC = (1ULL << 4),
+         SSE2 = (1ULL << 26),
+         CLMUL = (1ULL << 33),
+         SSSE3 = (1ULL << 41),
+         SSE41 = (1ULL << 51),
+         SSE42 = (1ULL << 52),
+         AESNI = (1ULL << 57),
+         RDRAND = (1ULL << 62)
+      };
+
+      if(flags0 & x86_CPUID_1_bits::RDTSC)
+         features_detected |= CPUID::CPUID_RDTSC_BIT;
+      if(flags0 & x86_CPUID_1_bits::SSE2)
+         features_detected |= CPUID::CPUID_SSE2_BIT;
+      if(flags0 & x86_CPUID_1_bits::CLMUL)
+         features_detected |= CPUID::CPUID_CLMUL_BIT;
+      if(flags0 & x86_CPUID_1_bits::SSSE3)
+         features_detected |= CPUID::CPUID_SSSE3_BIT;
+      if(flags0 & x86_CPUID_1_bits::SSE41)
+         features_detected |= CPUID::CPUID_SSE41_BIT;
+      if(flags0 & x86_CPUID_1_bits::SSE42)
+         features_detected |= CPUID::CPUID_SSE42_BIT;
+      if(flags0 & x86_CPUID_1_bits::AESNI)
+         features_detected |= CPUID::CPUID_AESNI_BIT;
+      if(flags0 & x86_CPUID_1_bits::RDRAND)
+         features_detected |= CPUID::CPUID_RDRAND_BIT;
+      }
+
+   if(is_intel)
+      {
+      // Intel cache line size is in cpuid(1) output
+      *cache_line_size = 8 * get_byte(2, cpuid[1]);
+      }
+   else if(is_amd)
+      {
+      // AMD puts it in vendor zone
+      X86_CPUID(0x80000005, cpuid);
+      *cache_line_size = get_byte(3, cpuid[2]);
+      }
 
-   altivec_capable |= (pvr == PVR_G4_7400);
-   altivec_capable |= ((pvr >> 4) == PVR_G4_74xx_24);
-   altivec_capable |= (pvr == PVR_G5_970);
-   altivec_capable |= (pvr == PVR_G5_970FX);
-   altivec_capable |= (pvr == PVR_G5_970MP);
-   altivec_capable |= (pvr == PVR_G5_970GX);
-   altivec_capable |= (pvr == PVR_POWER6);
-   altivec_capable |= (pvr == PVR_POWER7);
-   altivec_capable |= (pvr == PVR_POWER8);
-   altivec_capable |= (pvr == PVR_CELL_PPU);
+   if(max_supported_sublevel >= 7)
+      {
+      clear_mem(cpuid, 4);
+      X86_CPUID_SUBLEVEL(7, 0, cpuid);
+
+      enum x86_CPUID_7_bits : uint64_t {
+         AVX2 = (1ULL << 5),
+         BMI2 = (1ULL << 8),
+         AVX512F = (1ULL << 16),
+         RDSEED = (1ULL << 18),
+         ADX = (1ULL << 19),
+         SHA = (1ULL << 29),
+      };
+      uint64_t flags7 = (static_cast<uint64_t>(cpuid[2]) << 32) | cpuid[1];
+
+      if(flags7 & x86_CPUID_7_bits::AVX2)
+         features_detected |= CPUID::CPUID_AVX2_BIT;
+      if(flags7 & x86_CPUID_7_bits::BMI2)
+         features_detected |= CPUID::CPUID_BMI2_BIT;
+      if(flags7 & x86_CPUID_7_bits::AVX512F)
+         features_detected |= CPUID::CPUID_AVX512F_BIT;
+      if(flags7 & x86_CPUID_7_bits::RDSEED)
+         features_detected |= CPUID::CPUID_RDSEED_BIT;
+      if(flags7 & x86_CPUID_7_bits::ADX)
+         features_detected |= CPUID::CPUID_ADX_BIT;
+      if(flags7 & x86_CPUID_7_bits::SHA)
+         features_detected |= CPUID::CPUID_SHA_BIT;
+      }
+
+   /*
+   * If we don't have access to CPUID, we can still safely assume that
+   * any x86-64 processor has SSE2 and RDTSC
+   */
+#if defined(BOTAN_TARGET_ARCH_IS_X86_64)
+   if(features_detected == 0)
+      {
+      features_detected |= CPUID::CPUID_SSE2_BIT;
+      features_detected |= CPUID::CPUID_RDTSC_BIT;
+      }
 #endif
 
-   return altivec_capable;
+   return features_detected;
    }
 
 #endif
@@ -185,79 +363,46 @@ void CPUID::print(std::ostream& o)
 
    CPUID_PRINT(rdtsc);
    CPUID_PRINT(bmi2);
-   CPUID_PRINT(clmul);
+   CPUID_PRINT(adx);
+
    CPUID_PRINT(aes_ni);
+   CPUID_PRINT(clmul);
    CPUID_PRINT(rdrand);
    CPUID_PRINT(rdseed);
    CPUID_PRINT(intel_sha);
-   CPUID_PRINT(adx);
 #endif
 
 #if defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY)
    CPUID_PRINT(altivec);
 #endif
 
+#if defined(BOTAN_TARGET_CPU_IS_ARM_FAMILY)
+   CPUID_PRINT(neon);
+   CPUID_PRINT(arm_sha1);
+   CPUID_PRINT(arm_sha2);
+   CPUID_PRINT(arm_aes);
+   CPUID_PRINT(arm_pmull);
+#endif
+
 #undef CPUID_PRINT
    o << "\n";
    }
 
 void CPUID::initialize()
    {
-   clear_mem(g_processor_flags, 2);
+   g_processor_features = 0;
 
 #if defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY)
-   if(altivec_check_sysctl() || altivec_check_pvr_emul())
-      {
-      g_processor_flags[0] |= CPUID_ALTIVEC_BIT;
-      }
+   g_processor_features = powerpc_detect_cpu_featutures();
+#elif defined(BOTAN_TARGET_CPU_IS_ARM_FAMILY)
+   g_processor_features = arm_detect_cpu_features(&g_cache_line_size);
+#elif defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
+   g_processor_features = x86_detect_cpu_features(&g_cache_line_size);
 #endif
 
-#if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
-   const uint32_t INTEL_CPUID[3] = { 0x756E6547, 0x6C65746E, 0x49656E69 };
-   const uint32_t AMD_CPUID[3] = { 0x68747541, 0x444D4163, 0x69746E65 };
-
-   uint32_t cpuid[4] = { 0 };
-   X86_CPUID(0, cpuid);
-
-   const uint32_t max_supported_sublevel = cpuid[0];
-
-   if(max_supported_sublevel == 0)
-      return;
-
-   const bool is_intel = same_mem(cpuid + 1, INTEL_CPUID, 3);
-   const bool is_amd = same_mem(cpuid + 1, AMD_CPUID, 3);
-
-   X86_CPUID(1, cpuid);
-
-   g_processor_flags[0] = (static_cast<uint64_t>(cpuid[2]) << 32) | cpuid[3];
-
-   if(is_intel)
-      g_cache_line_size = 8 * get_byte(2, cpuid[1]);
-
-   if(max_supported_sublevel >= 7)
-      {
-      clear_mem(cpuid, 4);
-      X86_CPUID_SUBLEVEL(7, 0, cpuid);
-      g_processor_flags[1] = (static_cast<uint64_t>(cpuid[2]) << 32) | cpuid[1];
-      }
-
-   if(is_amd)
-      {
-      X86_CPUID(0x80000005, cpuid);
-      g_cache_line_size = get_byte(3, cpuid[2]);
-      }
-
-#endif
-
-#if defined(BOTAN_TARGET_ARCH_IS_X86_64)
-   /*
-   * If we don't have access to CPUID, we can still safely assume that
-   * any x86-64 processor has SSE2 and RDTSC
-   */
-   if(g_processor_flags[0] == 0)
-      g_processor_flags[0] = (1 << CPUID_SSE2_BIT) | (1 << CPUID_RDTSC_BIT);
-#endif
+   g_processor_features |= CPUID::CPUID_INITIALIZED_BIT;
 
+   // Check runtime endian
    const uint32_t endian32 = 0x01234567;
    const uint8_t* e8 = reinterpret_cast<const uint8_t*>(&endian32);
 
@@ -274,14 +419,13 @@ void CPUID::initialize()
       throw Internal_Error("Unexpected endian at runtime, neither big nor little");
       }
 
-   // If we were compiled with a known endian, verify if matches at runtime
+   // If we were compiled with a known endian, verify it matches at runtime
 #if defined(BOTAN_TARGET_CPU_IS_LITTLE_ENDIAN)
-   BOTAN_ASSERT(g_little_endian, "Little-endian build but big-endian at runtime");
+   BOTAN_ASSERT(g_little_endian == true, "Build and runtime endian match");
 #elif defined(BOTAN_TARGET_CPU_IS_BIG_ENDIAN)
-   BOTAN_ASSERT(!g_little_endian, "Big-endian build but little-endian at runtime");
+   BOTAN_ASSERT(g_little_endian == false, "Build and runtime endian match");
 #endif
 
-   g_initialized = true;
    }
 
 }
diff --git a/src/lib/utils/cpuid.h b/src/lib/utils/cpuid.h
index 634305aa1..2bb5a8301 100644
--- a/src/lib/utils/cpuid.h
+++ b/src/lib/utils/cpuid.h
@@ -1,6 +1,6 @@
 /*
 * Runtime CPU detection
-* (C) 2009-2010,2013 Jack Lloyd
+* (C) 2009,2010,2013,2017 Jack Lloyd
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
@@ -14,9 +14,22 @@
 namespace Botan {
 
 /**
-* A class handling runtime CPU feature detection
+* A class handling runtime CPU feature detection. It is limited to
+* just the features necessary to implement CPU specific code in Botan,
+* rather than being a general purpose utility.
 *
-* Currently this class supports only x86 (via CPUID) and PowerPC (AltiVec detection)
+* This class supports:
+*
+*  - x86 features using CPUID. x86 is also the only processor with
+*    accurate cache line detection currently.
+*
+*  - PowerPC AltiVec detection on Linux, NetBSD, OpenBSD, and Darwin
+*
+*  - ARM NEON and crypto extensions detection. On Linux and Android
+*    systems which support getauxval, that is used to access CPU
+*    feature information. Otherwise a relatively portable but
+*    thread-unsafe mechanism involving executing probe functions which
+*    catching SIGILL signal is used.
 */
 class BOTAN_DLL CPUID
    {
@@ -35,7 +48,7 @@ class BOTAN_DLL CPUID
       */
       static size_t cache_line_size()
          {
-         if(!g_initialized)
+         if(g_processor_features == 0)
             {
             initialize();
             }
@@ -44,38 +57,51 @@ class BOTAN_DLL CPUID
 
       static bool is_little_endian()
          {
-         if(!g_initialized)
+         if(g_processor_features == 0)
             {
             initialize();
             }
          return g_little_endian;
          }
 
-      enum CPUID_bits {
+      enum CPUID_bits : uint64_t {
 #if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
-         // This matches the layout of cpuid(1)
-         CPUID_RDTSC_BIT = 4,
-         CPUID_SSE2_BIT = 26,
-         CPUID_CLMUL_BIT = 33,
-         CPUID_SSSE3_BIT = 41,
-         CPUID_SSE41_BIT = 51,
-         CPUID_SSE42_BIT = 52,
-         CPUID_AESNI_BIT = 57,
-         CPUID_RDRAND_BIT = 62,
-
-         CPUID_AVX2_BIT = 64+5,
-         CPUID_BMI2_BIT = 64+8,
-         CPUID_AVX512F_BIT = 64+16,
-         CPUID_RDSEED_BIT = 64+18,
-         CPUID_ADX_BIT = 64+19,
-         CPUID_SHA_BIT = 64+29,
+         // These values have no relation to cpuid bitfields
+
+         // SIMD instruction sets
+         CPUID_SSE2_BIT    = (1ULL << 0),
+         CPUID_SSSE3_BIT   = (1ULL << 1),
+         CPUID_SSE41_BIT   = (1ULL << 2),
+         CPUID_SSE42_BIT   = (1ULL << 3),
+         CPUID_AVX2_BIT    = (1ULL << 4),
+         CPUID_AVX512F_BIT = (1ULL << 5),
+
+         // Misc useful instructions
+         CPUID_RDTSC_BIT   = (1ULL << 10),
+         CPUID_BMI2_BIT    = (1ULL << 11),
+         CPUID_ADX_BIT     = (1ULL << 12),
+
+         // Crypto-specific ISAs
+         CPUID_AESNI_BIT   = (1ULL << 16),
+         CPUID_CLMUL_BIT   = (1ULL << 17),
+         CPUID_RDRAND_BIT  = (1ULL << 18),
+         CPUID_RDSEED_BIT  = (1ULL << 19),
+         CPUID_SHA_BIT     = (1ULL << 20),
 #endif
 
 #if defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY)
-         CPUID_ALTIVEC_BIT = 0
+         CPUID_ALTIVEC_BIT = (1ULL << 0),
 #endif
 
-         // TODO: ARMv8 feature detection
+#if defined(BOTAN_TARGET_CPU_IS_ARM_FAMILY)
+         CPUID_ARM_NEON_BIT  = (1ULL << 0),
+         CPUID_ARM_AES_BIT   = (1ULL << 16),
+         CPUID_ARM_PMULL_BIT = (1ULL << 17),
+         CPUID_ARM_SHA1_BIT  = (1ULL << 18),
+         CPUID_ARM_SHA2_BIT  = (1ULL << 19),
+#endif
+
+         CPUID_INITIALIZED_BIT = (1ULL << 63)
       };
 
 #if defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY)
@@ -86,6 +112,38 @@ class BOTAN_DLL CPUID
          { return has_cpuid_bit(CPUID_ALTIVEC_BIT); }
 #endif
 
+#if defined(BOTAN_TARGET_CPU_IS_ARM_FAMILY)
+      /**
+      * Check if the processor supports NEON SIMD
+      */
+      static bool has_neon()
+         { return has_cpuid_bit(CPUID_ARM_NEON_BIT); }
+
+      /**
+      * Check if the processor supports ARMv8 SHA1
+      */
+      static bool has_arm_sha1()
+         { return has_cpuid_bit(CPUID_ARM_SHA1_BIT); }
+
+      /**
+      * Check if the processor supports ARMv8 SHA2
+      */
+      static bool has_arm_sha2()
+         { return has_cpuid_bit(CPUID_ARM_SHA2_BIT); }
+
+      /**
+      * Check if the processor supports ARMv8 AES
+      */
+      static bool has_arm_aes()
+         { return has_cpuid_bit(CPUID_ARM_AES_BIT); }
+
+      /**
+      * Check if the processor supports ARMv8 PMULL
+      */
+      static bool has_arm_pmull()
+         { return has_cpuid_bit(CPUID_ARM_PMULL_BIT); }
+#endif
+
 #if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
 
       /**
@@ -176,26 +234,31 @@ class BOTAN_DLL CPUID
       /*
       * Clear a CPUID bit
       * Call CPUID::initialize to reset
+      *
+      * This is only exposed for testing, don't use unless you know
+      * what you are doing.
       */
       static void clear_cpuid_bit(CPUID_bits bit)
          {
-         const uint64_t mask = ~(static_cast<uint64_t>(1) << (bit % 64));
-         g_processor_flags[bit/64] &= mask;
+         const uint64_t mask = ~(static_cast<uint64_t>(bit));
+         g_processor_features &= mask;
          }
 
+      /*
+      * Don't call this function, use CPUID::has_xxx above
+      * It should have been private.
+      */
       static bool has_cpuid_bit(CPUID_bits elem)
          {
-         if(!g_initialized)
+         if(g_processor_features == 0)
             initialize();
-         const size_t bit = static_cast<size_t>(elem);
-         return ((g_processor_flags[bit/64] >> (bit % 64)) & 1);
+         return ((g_processor_features & static_cast<uint64_t>(elem)) != 0);
          }
 
    private:
-      static bool g_initialized;
       static bool g_little_endian;
       static size_t g_cache_line_size;
-      static uint64_t g_processor_flags[2];
+      static uint64_t g_processor_features;
    };
 
 }
diff --git a/src/lib/utils/os_utils.cpp b/src/lib/utils/os_utils.cpp
index 46ce2a056..4dac4f9af 100644
--- a/src/lib/utils/os_utils.cpp
+++ b/src/lib/utils/os_utils.cpp
@@ -17,6 +17,8 @@
   #include <sys/mman.h>
   #include <sys/resource.h>
   #include <unistd.h>
+  #include <signal.h>
+  #include <setjmp.h>
 #endif
 
 #if defined(BOTAN_TARGET_OS_IS_WINDOWS) || defined(BOTAN_TARGET_OS_IS_MINGW)
@@ -298,6 +300,74 @@ void free_locked_pages(void* ptr, size_t length)
 #endif
    }
 
+#if defined(BOTAN_TARGET_OS_TYPE_IS_UNIX)
+namespace {
+
+static ::sigjmp_buf g_sigill_jmp_buf;
+
+void botan_sigill_handler(int)
+   {
+   ::siglongjmp(g_sigill_jmp_buf, /*non-zero return value*/1);
+   }
+
+}
+#endif
+
+int run_cpu_instruction_probe(std::function<int ()> probe_fn)
+   {
+#if defined(BOTAN_TARGET_OS_TYPE_IS_UNIX)
+   struct sigaction old_sigaction;
+   struct sigaction sigaction;
+
+   sigaction.sa_handler = botan_sigill_handler;
+   sigemptyset(&sigaction.sa_mask);
+   sigaction.sa_flags = 0;
+
+   int rc = ::sigaction(SIGILL, &sigaction, &old_sigaction);
+
+   if(rc != 0)
+      throw Exception("run_cpu_instruction_probe sigaction failed");
+
+   /*
+   There doesn't seem to be any way for probe_result to not be initialized
+   by some code path below, but this initializer is left as error just in case.
+   */
+   int probe_result = -3;
+
+   try
+      {
+      rc = ::sigsetjmp(g_sigill_jmp_buf, /*save sigs*/1);
+
+      if(rc == 0)
+         {
+         // first call to sigsetjmp
+         probe_result = probe_fn();
+         }
+      else if(rc == 1)
+         {
+         // non-local return from siglongjmp in signal handler: return error
+         probe_result = -1;
+         }
+      else
+         throw Exception("run_cpu_instruction_probe unexpected sigsetjmp return value");
+      }
+   catch(...)
+      {
+      probe_result = -2;
+      }
+
+   rc = ::sigaction(SIGILL, &old_sigaction, nullptr);
+   if(rc != 0)
+      throw Exception("run_cpu_instruction_probe sigaction restore failed");
+
+   return probe_result;
+#else
+   // TODO: Windows support
+   return -9; // not supported
+#endif
+   }
+
+
 }
 
 }
diff --git a/src/lib/utils/os_utils.h b/src/lib/utils/os_utils.h
index 213c5982b..b74debc46 100644
--- a/src/lib/utils/os_utils.h
+++ b/src/lib/utils/os_utils.h
@@ -1,6 +1,6 @@
 /*
 * OS specific utility functions
-* (C) 2015,2016 Jack Lloyd
+* (C) 2015,2016,2017 Jack Lloyd
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
@@ -9,24 +9,28 @@
 #define BOTAN_OS_UTILS_H__
 
 #include <botan/types.h>
+#include <functional>
 
 namespace Botan {
 
 namespace OS {
 
 /**
-* Returns the OS assigned process ID, if available. Otherwise throws.
+* @return process ID assigned by the operating system.
+* On Unix and Windows systems, this always returns a result
+* On IncludeOS it returns 0 since there is no process ID to speak of
+* in a unikernel.
 */
 uint32_t get_process_id();
 
 /**
-* Return the highest resolution clock available on the system.
+* @return highest resolution clock available on the system.
 *
 * The epoch and update rate of this clock is arbitrary and depending
 * on the hardware it may not tick at a constant rate.
 *
-* Returns the value of the hardware cycle counter, if available.
-* On Windows calls QueryPerformanceCounter.
+* Uses hardware cycle counter, if available.
+* On Windows, always calls QueryPerformanceCounter.
 * Under GCC or Clang on supported platforms the hardware cycle counter is queried:
 *  x86, PPC, Alpha, SPARC, IA-64, S/390x, and HP-PA
 * On other platforms clock_gettime is used with some monotonic timer, if available.
@@ -35,30 +39,51 @@ uint32_t get_process_id();
 uint64_t get_processor_timestamp();
 
 /**
-* Returns the value of the system clock with best resolution available,
-* normalized to nanoseconds resolution.
+* @return system clock with best resolution available, normalized to
+* nanoseconds resolution.
 */
 uint64_t get_system_timestamp_ns();
 
-/*
-* Returns the maximum amount of memory (in bytes) we could/should
-* hyptothetically allocate. Reads "BOTAN_MLOCK_POOL_SIZE" from
-* environment which can be set to zero.
+/**
+* @return maximum amount of memory (in bytes) Botan could/should
+* hyptothetically allocate for the memory poool. Reads environment
+* variable "BOTAN_MLOCK_POOL_SIZE", set to "0" to disable pool.
 */
 size_t get_memory_locking_limit();
 
-/*
+/**
 * Request so many bytes of page-aligned RAM locked into memory using
 * mlock, VirtualLock, or similar. Returns null on failure. The memory
 * returned is zeroed. Free it with free_locked_pages.
+* @param length requested allocation in bytes
 */
 void* allocate_locked_pages(size_t length);
 
-/*
+/**
 * Free memory allocated by allocate_locked_pages
+* @param ptr a pointer returned by allocate_locked_pages
+* @param length length passed to allocate_locked_pages
 */
 void free_locked_pages(void* ptr, size_t length);
 
+/**
+* Run a probe instruction to test for support for a CPU instruction.
+* Runs in system-specific env that catches illegal instructions; this
+* function always fails if the OS doesn't provide this.
+* Returns value of probe_fn, if it could run.
+* If error occurs, returns negative number.
+* This allows probe_fn to indicate errors of its own, if it wants.
+* For example the instruction might not only be only available on some
+* CPUs, but also buggy on some subset of these - the probe function
+* can test to make sure the instruction works properly before
+* indicating that the instruction is available.
+*
+* Return codes:
+* -1 illegal instruction detected
+* -2 exception thrown
+*/
+int run_cpu_instruction_probe(std::function<int ()> probe_fn);
+
 }
 
 }