lib/scudo/scudo_utils.cpp

//===-- scudo_utils.cpp -----------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// Platform specific utility functions.
///
//===----------------------------------------------------------------------===//

#include "scudo_utils.h"

#include <stdarg.h>
#if defined(__x86_64__) || defined(__i386__)
# include <cpuid.h>
#endif
#if defined(__arm__) || defined(__aarch64__)
# if SANITIZER_ANDROID && __ANDROID_API__ < 18
// getauxval() was introduced with API level 18 on Android. Emulate it using
// /proc/self/auxv for lower API levels.
#  include "sanitizer_common/sanitizer_posix.h"

#  include <fcntl.h>

#  define AT_HWCAP 16

namespace __sanitizer {

uptr getauxval(uptr Type) {
  uptr F = internal_open("/proc/self/auxv", O_RDONLY);
  if (internal_iserror(F))
    return 0;
  struct { uptr Tag; uptr Value; } Entry;
  uptr Result = 0;
  for (;;) {
    uptr N = internal_read(F, &Entry, sizeof(Entry));
    if (internal_iserror(N))
      break;
    if (N == 0 || N != sizeof(Entry) || (Entry.Tag == 0 && Entry.Value == 0))
      break;
    if (Entry.Tag == Type) {
      Result =  Entry.Value;
      break;
    }
  }
  internal_close(F);
  return Result;
}

}  // namespace __sanitizer
# else
#  include <sys/auxv.h>
# endif
#endif

// TODO(kostyak): remove __sanitizer *Printf uses in favor for our own less
//                complicated string formatting code. The following is a
//                temporary workaround to be able to use __sanitizer::VSNPrintf.
namespace __sanitizer {

extern int VSNPrintf(char *buff, int buff_length, const char *format,
                     va_list args);

}  // namespace __sanitizer

namespace __scudo {

FORMAT(1, 2)
void NORETURN dieWithMessage(const char *Format, ...) {
  // Our messages are tiny, 256 characters is more than enough.
  char Message[256];
  va_list Args;
  va_start(Args, Format);
  __sanitizer::VSNPrintf(Message, sizeof(Message), Format, Args);
  va_end(Args);
  RawWrite(Message);
  Die();
}

#if defined(__x86_64__) || defined(__i386__)
// i386 and x86_64 specific code to detect CRC32 hardware support via CPUID.
// CRC32 requires the SSE 4.2 instruction set.
typedef struct {
  u32 Eax;
  u32 Ebx;
  u32 Ecx;
  u32 Edx;
} CPUIDRegs;

static void getCPUID(CPUIDRegs *Regs, u32 Level) {
  __get_cpuid(Level, &Regs->Eax, &Regs->Ebx, &Regs->Ecx, &Regs->Edx);
}

CPUIDRegs getCPUFeatures() {
  CPUIDRegs VendorRegs = {};
  getCPUID(&VendorRegs, 0);
  bool IsIntel =
      (VendorRegs.Ebx == signature_INTEL_ebx) &&
      (VendorRegs.Edx == signature_INTEL_edx) &&
      (VendorRegs.Ecx == signature_INTEL_ecx);
  bool IsAMD =
      (VendorRegs.Ebx == signature_AMD_ebx) &&
      (VendorRegs.Edx == signature_AMD_edx) &&
      (VendorRegs.Ecx == signature_AMD_ecx);
  // Default to an empty feature set if not on a supported CPU.
  CPUIDRegs FeaturesRegs = {};
  if (IsIntel || IsAMD) {
    getCPUID(&FeaturesRegs, 1);
  }
  return FeaturesRegs;
}

# ifndef bit_SSE4_2
#  define bit_SSE4_2 bit_SSE42  // clang and gcc have different defines.
# endif

bool testCPUFeature(CPUFeature Feature) {
  CPUIDRegs FeaturesRegs = getCPUFeatures();

  switch (Feature) {
    case CRC32CPUFeature:  // CRC32 is provided by SSE 4.2.
      return !!(FeaturesRegs.Ecx & bit_SSE4_2);
    default:
      break;
  }
  return false;
}
#elif defined(__arm__) || defined(__aarch64__)
// For ARM and AArch64, hardware CRC32 support is indicated in the AT_HWVAL
// auxiliary vector.

# ifndef HWCAP_CRC32
#  define HWCAP_CRC32 (1 << 7)  // HWCAP_CRC32 is missing on older platforms.
# endif

bool testCPUFeature(CPUFeature Feature) {
  uptr HWCap = getauxval(AT_HWCAP);

  switch (Feature) {
    case CRC32CPUFeature:
      return !!(HWCap & HWCAP_CRC32);
    default:
      break;
  }
  return false;
}
#else
bool testCPUFeature(CPUFeature Feature) {
  return false;
}
#endif  // defined(__x86_64__) || defined(__i386__)

}  // namespace __scudo