src/cpuinfo_arm.c

// Copyright 2017 Google LLC
//
// 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
//
//    http://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 "cpuinfo_arm.h"

#include <assert.h>
#include <ctype.h>

#include "internal/bit_utils.h"
#include "internal/filesystem.h"
#include "internal/hwcaps.h"
#include "internal/stack_line_reader.h"
#include "internal/string_view.h"

// Generation of feature's getters/setters functions and kGetters, kSetters,
// kCpuInfoFlags and kHardwareCapabilities global tables.
#define DEFINE_TABLE_FEATURE_TYPE ArmFeatures
#define DEFINE_TABLE_DB_FILENAME "cpuinfo_arm_db.inl"
#include "define_tables.h"

typedef struct {
  bool processor_reports_armv6;
  bool hardware_reports_goldfish;
} ProcCpuInfoData;

static int IndexOfNonDigit(StringView str) {
  size_t index = 0;
  while (str.size && isdigit(CpuFeatures_StringView_Front(str))) {
    str = CpuFeatures_StringView_PopFront(str, 1);
    ++index;
  }
  return index;
}

static bool HandleArmLine(const LineResult result, ArmInfo* const info,
                          ProcCpuInfoData* const proc_info) {
  StringView line = result.line;
  StringView key, value;
  if (CpuFeatures_StringView_GetAttributeKeyValue(line, &key, &value)) {
    if (CpuFeatures_StringView_IsEquals(key, str("Features"))) {
      for (size_t i = 0; i < ARM_LAST_; ++i) {
        kSetters[i](&info->features,
                    CpuFeatures_StringView_HasWord(value, kCpuInfoFlags[i]));
      }
    } else if (CpuFeatures_StringView_IsEquals(key, str("CPU implementer"))) {
      info->implementer = CpuFeatures_StringView_ParsePositiveNumber(value);
    } else if (CpuFeatures_StringView_IsEquals(key, str("CPU variant"))) {
      info->variant = CpuFeatures_StringView_ParsePositiveNumber(value);
    } else if (CpuFeatures_StringView_IsEquals(key, str("CPU part"))) {
      info->part = CpuFeatures_StringView_ParsePositiveNumber(value);
    } else if (CpuFeatures_StringView_IsEquals(key, str("CPU revision"))) {
      info->revision = CpuFeatures_StringView_ParsePositiveNumber(value);
    } else if (CpuFeatures_StringView_IsEquals(key, str("CPU architecture"))) {
      // CPU architecture is a number that may be followed by letters. e.g.
      // "6TEJ", "7".
      const StringView digits =
          CpuFeatures_StringView_KeepFront(value, IndexOfNonDigit(value));
      info->architecture = CpuFeatures_StringView_ParsePositiveNumber(digits);
    } else if (CpuFeatures_StringView_IsEquals(key, str("Processor")) ||
               CpuFeatures_StringView_IsEquals(key, str("model name"))) {
      // Android reports this in a non-Linux standard "Processor" but sometimes
      // also in "model name", Linux reports it only in "model name"
      // see RaspberryPiZero (Linux) vs InvalidArmv7 (Android) test-cases
      proc_info->processor_reports_armv6 =
          CpuFeatures_StringView_IndexOf(value, str("(v6l)")) >= 0;
    } else if (CpuFeatures_StringView_IsEquals(key, str("Hardware"))) {
      proc_info->hardware_reports_goldfish =
          CpuFeatures_StringView_IsEquals(value, str("Goldfish"));
    }
  }
  return !result.eof;
}

uint32_t GetArmCpuId(const ArmInfo* const info) {
  return (ExtractBitRange(info->implementer, 7, 0) << 24) |
         (ExtractBitRange(info->variant, 3, 0) << 20) |
         (ExtractBitRange(info->part, 11, 0) << 4) |
         (ExtractBitRange(info->revision, 3, 0) << 0);
}

static void FixErrors(ArmInfo* const info,
                      ProcCpuInfoData* const proc_cpu_info_data) {
  // Fixing Samsung kernel reporting invalid cpu architecture.
  // http://code.google.com/p/android/issues/detail?id=10812
  if (proc_cpu_info_data->processor_reports_armv6 && info->architecture >= 7) {
    info->architecture = 6;
  }

  // Handle kernel configuration bugs that prevent the correct reporting of CPU
  // features.
  switch (GetArmCpuId(info)) {
    case 0x4100C080:
      // Special case: The emulator-specific Android 4.2 kernel fails to report
      // support for the 32-bit ARM IDIV instruction. Technically, this is a
      // feature of the virtual CPU implemented by the emulator. Note that it
      // could also support Thumb IDIV in the future, and this will have to be
      // slightly updated.
      if (info->architecture >= 7 &&
          proc_cpu_info_data->hardware_reports_goldfish) {
        info->features.idiva = true;
      }
      break;
    case 0x511004D0:
      // https://crbug.com/341598.
      info->features.neon = false;
      break;
    case 0x510006F2:
    case 0x510006F3:
      // The Nexus 4 (Qualcomm Krait) kernel configuration forgets to report
      // IDIV support.
      info->features.idiva = true;
      info->features.idivt = true;
      break;
  }

  // Propagate cpu features.
  if (info->features.vfpv4) info->features.vfpv3 = true;
  if (info->features.neon) info->features.vfpv3 = true;
  if (info->features.vfpv3) info->features.vfp = true;
}

static void FillProcCpuInfoData(ArmInfo* const info,
                                ProcCpuInfoData* proc_cpu_info_data) {
  const int fd = CpuFeatures_OpenFile("/proc/cpuinfo");
  if (fd >= 0) {
    StackLineReader reader;
    StackLineReader_Initialize(&reader, fd);
    for (;;) {
      if (!HandleArmLine(StackLineReader_NextLine(&reader), info,
                         proc_cpu_info_data)) {
        break;
      }
    }
    CpuFeatures_CloseFile(fd);
  }
}

static const ArmInfo kEmptyArmInfo;

static const ProcCpuInfoData kEmptyProcCpuInfoData;

ArmInfo GetArmInfo(void) {
  // capabilities are fetched from both getauxval and /proc/cpuinfo so we can
  // have some information if the executable is sandboxed (aka no access to
  // /proc/cpuinfo).
  ArmInfo info = kEmptyArmInfo;
  ProcCpuInfoData proc_cpu_info_data = kEmptyProcCpuInfoData;

  FillProcCpuInfoData(&info, &proc_cpu_info_data);
  const HardwareCapabilities hwcaps = CpuFeatures_GetHardwareCapabilities();
  for (size_t i = 0; i < ARM_LAST_; ++i) {
    if (CpuFeatures_IsHwCapsSet(kHardwareCapabilities[i], hwcaps)) {
      kSetters[i](&info.features, true);
    }
  }

  FixErrors(&info, &proc_cpu_info_data);

  return info;
}

////////////////////////////////////////////////////////////////////////////////
// Introspection functions

int GetArmFeaturesEnumValue(const ArmFeatures* features,
                            ArmFeaturesEnum value) {
  if (value >= ARM_LAST_) return false;
  return kGetters[value](features);
}

const char* GetArmFeaturesEnumName(ArmFeaturesEnum value) {
  if (value >= ARM_LAST_) return "unknown feature";
  return kCpuInfoFlags[value];
}