mozglue/build/arm.cpp

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 /* compile-time and runtime tests for whether to use various ARM extensions */
   6
   7 #include "arm.h"
   8
   9 #if defined(MOZILLA_ARM_HAVE_CPUID_DETECTION)
  10
  11 // arm.h has parallel #ifs which declare MOZILLA_ARM_HAVE_CPUID_DETECTION.
  12 // We don't check it here so that we get compile errors if it's defined, but
  13 // we don't compile one of these detection methods. The detection code here is
  14 // based on the CPU detection in libtheora.
  15
  16 #  if defined(__linux__) || defined(ANDROID)
  17 #    include <stdio.h>
  18 #    include <stdlib.h>
  19 #    include <string.h>
  20
  21 enum {
  22   MOZILLA_HAS_EDSP_FLAG = 1,
  23   MOZILLA_HAS_ARMV6_FLAG = 2,
  24   MOZILLA_HAS_ARMV7_FLAG = 4,
  25   MOZILLA_HAS_NEON_FLAG = 8,
  26   MOZILLA_HAS_AES_FLAG = 16
  27 };
  28
  29 static unsigned get_arm_cpu_flags(void) {
  30   unsigned flags;
  31   FILE* fin;
  32   bool armv6_processor = false;
  33   flags = 0;
  34   /*Reading /proc/self/auxv would be easier, but that doesn't work reliably on
  35     Android. This also means that detection will fail in Scratchbox, which is
  36     desirable, as NEON does not work in the qemu shipped with the Maemo 5 SDK.
  37     I don't know if /proc/self/auxv would do any better in that case, anyway,
  38     or if it would return random flags from the host CPU.*/
  39   fin = fopen("/proc/cpuinfo", "r");
  40   if (fin != nullptr) {
  41     /*512 should be enough for anybody (it's even enough for all the flags that
  42       x86 has accumulated... so far).*/
  43     char buf[512];
  44     while (fgets(buf, 511, fin) != nullptr) {
  45       if (memcmp(buf, "Features", 8) == 0) {
  46         char* p;
  47         p = strstr(buf, " edsp");
  48         if (p != nullptr && (p[5] == ' ' || p[5] == '\n'))
  49           flags |= MOZILLA_HAS_EDSP_FLAG;
  50         p = strstr(buf, " neon");
  51         if (p != nullptr && (p[5] == ' ' || p[5] == '\n'))
  52           flags |= MOZILLA_HAS_NEON_FLAG;
  53         p = strstr(buf, " aes");
  54         if (p != nullptr && (p[4] == ' ' || p[4] == '\n')) {
  55           flags |= MOZILLA_HAS_AES_FLAG;
  56         }
  57       }
  58       if (memcmp(buf, "CPU architecture:", 17) == 0) {
  59         int version;
  60         version = atoi(buf + 17);
  61         if (version >= 6) flags |= MOZILLA_HAS_ARMV6_FLAG;
  62         if (version >= 7) flags |= MOZILLA_HAS_ARMV7_FLAG;
  63       }
  64       /* media/webrtc/trunk/src/system_wrappers/source/cpu_features_arm.c
  65        * Unfortunately, it seems that certain ARMv6-based CPUs
  66        * report an incorrect architecture number of 7!
  67        *
  68        * We try to correct this by looking at the 'elf_format'
  69        * field reported by the 'Processor' field, which is of the
  70        * form of "(v7l)" for an ARMv7-based CPU, and "(v6l)" for
  71        * an ARMv6-one.
  72        */
  73       if (memcmp(buf, "Processor\t:", 11) == 0) {
  74         if (strstr(buf, "(v6l)") != 0) {
  75           armv6_processor = true;
  76         }
  77       }
  78     }
  79     fclose(fin);
  80   }
  81   if (armv6_processor) {
  82     // ARMv6 pretending to be ARMv7? clear flag
  83     if (flags & MOZILLA_HAS_ARMV7_FLAG) {
  84       flags &= ~MOZILLA_HAS_ARMV7_FLAG;
  85     }
  86   }
  87   return flags;
  88 }
  89
  90 // Cache a local copy so we only have to read /proc/cpuinfo once.
  91 static unsigned arm_cpu_flags = get_arm_cpu_flags();
  92
  93 #    if !defined(MOZILLA_PRESUME_EDSP)
  94 static bool check_edsp(void) {
  95   return (arm_cpu_flags & MOZILLA_HAS_EDSP_FLAG) != 0;
  96 }
  97 #    endif
  98
  99 #    if !defined(MOZILLA_PRESUME_ARMV6)
 100 static bool check_armv6(void) {
 101   return (arm_cpu_flags & MOZILLA_HAS_ARMV6_FLAG) != 0;
 102 }
 103 #    endif
 104
 105 #    if !defined(MOZILLA_PRESUME_ARMV7)
 106 static bool check_armv7(void) {
 107   return (arm_cpu_flags & MOZILLA_HAS_ARMV7_FLAG) != 0;
 108 }
 109 #    endif
 110
 111 #    if !defined(MOZILLA_PRESUME_NEON)
 112 static bool check_neon(void) {
 113   return (arm_cpu_flags & MOZILLA_HAS_NEON_FLAG) != 0;
 114 }
 115 #    endif
 116
 117 #    if !defined(MOZILLA_PRESUME_ARM_AES)
 118 static bool check_aes(void) {
 119   return (arm_cpu_flags & MOZILLA_HAS_AES_FLAG) != 0;
 120 }
 121 #    endif
 122
 123 #  endif  // defined(__linux__) || defined(ANDROID)
 124
 125 namespace mozilla {
 126 namespace arm_private {
 127 #  if !defined(MOZILLA_PRESUME_EDSP)
 128 bool edsp_enabled = check_edsp();
 129 #  endif
 130 #  if !defined(MOZILLA_PRESUME_ARMV6)
 131 bool armv6_enabled = check_armv6();
 132 #  endif
 133 #  if !defined(MOZILLA_PRESUME_ARMV7)
 134 bool armv7_enabled = check_armv7();
 135 #  endif
 136 #  if !defined(MOZILLA_PRESUME_NEON)
 137 bool neon_enabled = check_neon();
 138 #  endif
 139 #  if !defined(MOZILLA_PRESUME_ARM_AES)
 140 bool aes_enabled = check_aes();
 141 #  endif
 142 }  // namespace arm_private
 143 }  // namespace mozilla
 144
 145 #endif  // MOZILLA_ARM_HAVE_CPUID_DETECTION