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