The Tor Browser: mozglue/build/arm.cpp@97036ab72558 (annotated)

mozglue/build/arm.cpp@97036ab72558 (annotated)

mozglue/build/arm.cpp

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 /* compile-time and runtime tests for whether to use various ARM extensions */
 #include "mozilla/NullPtr.h"
 #include "arm.h"
 #if defined(MOZILLA_ARM_HAVE_CPUID_DETECTION)
 namespace {
 // arm.h has parallel #ifs which declare MOZILLA_ARM_HAVE_CPUID_DETECTION.
 // We don't check it here so that we get compile errors if it's defined, but
 // we don't compile one of these detection methods. The detection code here is
 // based on the CPU detection in libtheora.
 #  if defined(_MSC_VER)
 //For GetExceptionCode() and EXCEPTION_ILLEGAL_INSTRUCTION.
 #    define WIN32_LEAN_AND_MEAN
 #    define WIN32_EXTRA_LEAN
 #    include <windows.h>
 #    if !defined(MOZILLA_PRESUME_EDSP)
 static bool
 check_edsp(void)
 {
 #      if defined(MOZILLA_MAY_SUPPORT_EDSP)
   __try
   {
     //PLD [r13]
     __emit(0xF5DDF000);
     return true;
   }
   __except(GetExceptionCode()==EXCEPTION_ILLEGAL_INSTRUCTION)
   {
     //Ignore exception.
   }
 #      endif
   return false;
 }
 #    endif // !MOZILLA_PRESUME_EDSP
 #    if !defined(MOZILLA_PRESUME_ARMV6)
 static bool
 check_armv6(void)
 {
 #      if defined(MOZILLA_MAY_SUPPORT_ARMV6)
   __try
   {
     //SHADD8 r3,r3,r3
     __emit(0xE6333F93);
     return true;
   }
   __except(GetExceptionCode()==EXCEPTION_ILLEGAL_INSTRUCTION)
   {
     //Ignore exception.
   }
 #      endif
   return false;
 }
 #    endif // !MOZILLA_PRESUME_ARMV6
 #    if !defined(MOZILLA_PRESUME_ARMV7)
 static bool
 check_armv7(void)
 {
 #      if defined(MOZILLA_MAY_SUPPORT_ARMV7)
   __try
   {
     // ARMv7 DMB (Data Memory Barrier) for stores (DMB.ST)
     // The Data Memory Barrier existed before ARMv7 as a
     // cp15 operation, but ARMv7 introduced a dedicated
     // instruction, DMB.
     emit(0xF57FF05E);
     return true;
   }
   __except(GetExceptionCode()==EXCEPTION_ILLEGAL_INSTRUCTION)
   {
     //Ignore exception.
   }
 #      endif
   return false;
 }
 #    endif // !MOZILLA_PRESUME_ARMV7
 #    if !defined(MOZILLA_PRESUME_NEON)
 static bool
 check_neon(void)
 {
 #      if defined(MOZILLA_MAY_SUPPORT_NEON)
   __try
   {
     //VORR q0,q0,q0
     __emit(0xF2200150);
     return true;
   }
   __except(GetExceptionCode()==EXCEPTION_ILLEGAL_INSTRUCTION)
   {
     //Ignore exception.
   }
 #      endif
   return false;
 }
 #    endif // !MOZILLA_PRESUME_NEON
 #  elif defined(__linux__) || defined(ANDROID)
 #    include <stdio.h>
 #    include <stdlib.h>
 #    include <string.h>
 enum{
   MOZILLA_HAS_EDSP_FLAG=1,
   MOZILLA_HAS_ARMV6_FLAG=2,
   MOZILLA_HAS_ARMV7_FLAG=4,
   MOZILLA_HAS_NEON_FLAG=8
 };
 static unsigned
 get_arm_cpu_flags(void)
 {
   unsigned  flags;
   FILE     *fin;
   bool      armv6_processor = false;
   flags = 0;
   /*Reading /proc/self/auxv would be easier, but that doesn't work reliably on
     Android. This also means that detection will fail in Scratchbox, which is
     desirable, as NEON does not work in the qemu shipped with the Maemo 5 SDK.
     I don't know if /proc/self/auxv would do any better in that case, anyway,
     or if it would return random flags from the host CPU.*/
   fin = fopen ("/proc/cpuinfo","r");
   if (fin != nullptr)
   {
     /*512 should be enough for anybody (it's even enough for all the flags that
       x86 has accumulated... so far).*/
     char buf[512];
     while (fgets(buf, 511, fin) != nullptr)
     {
       if (memcmp(buf, "Features", 8) == 0)
       {
         char *p;
         p = strstr(buf, " edsp");
         if (p != nullptr && (p[5] == ' ' || p[5] == '\n'))
           flags |= MOZILLA_HAS_EDSP_FLAG;
         p = strstr(buf, " neon");
         if( p != nullptr && (p[5] == ' ' || p[5] == '\n'))
           flags |= MOZILLA_HAS_NEON_FLAG;
       }
       if (memcmp(buf, "CPU architecture:", 17) == 0)
       {
         int version;
         version = atoi(buf + 17);
         if (version >= 6)
           flags |= MOZILLA_HAS_ARMV6_FLAG;
         if (version >= 7)
           flags |= MOZILLA_HAS_ARMV7_FLAG;
       }
       /* media/webrtc/trunk/src/system_wrappers/source/cpu_features_arm.c
        * Unfortunately, it seems that certain ARMv6-based CPUs
        * report an incorrect architecture number of 7!
        *
        * We try to correct this by looking at the 'elf_format'
        * field reported by the 'Processor' field, which is of the
        * form of "(v7l)" for an ARMv7-based CPU, and "(v6l)" for
        * an ARMv6-one.
        */
       if (memcmp(buf, "Processor\t:", 11) == 0) {
           if (strstr(buf, "(v6l)") != 0) {
               armv6_processor = true;
           }
       }
     }
     fclose(fin);
   }
   if (armv6_processor) {
       // ARMv6 pretending to be ARMv7? clear flag
       if (flags & MOZILLA_HAS_ARMV7_FLAG) {
           flags &= ~MOZILLA_HAS_ARMV7_FLAG;
       }
   }
   return flags;
 }
 // Cache a local copy so we only have to read /proc/cpuinfo once.
 static unsigned arm_cpu_flags = get_arm_cpu_flags();
 #    if !defined(MOZILLA_PRESUME_EDSP)
 static bool
 check_edsp(void)
 {
   return (arm_cpu_flags & MOZILLA_HAS_EDSP_FLAG) != 0;
 }
 #    endif
 #    if !defined(MOZILLA_PRESUME_ARMV6)
 static bool
 check_armv6(void)
 {
   return (arm_cpu_flags & MOZILLA_HAS_ARMV6_FLAG) != 0;
 }
 #    endif
 #    if !defined(MOZILLA_PRESUME_ARMV7)
 static bool
 check_armv7(void)
 {
   return (arm_cpu_flags & MOZILLA_HAS_ARMV7_FLAG) != 0;
 }
 #    endif
 #    if !defined(MOZILLA_PRESUME_NEON)
 static bool
 check_neon(void)
 {
   return (arm_cpu_flags & MOZILLA_HAS_NEON_FLAG) != 0;
 }
 #    endif
 #  endif // defined(__linux__) || defined(ANDROID)
 }
 namespace mozilla {
   namespace arm_private {
 #  if !defined(MOZILLA_PRESUME_EDSP)
     bool edsp_enabled = check_edsp();
 #  endif
 #  if !defined(MOZILLA_PRESUME_ARMV6)
     bool armv6_enabled = check_armv6();
 #  endif
 #  if !defined(MOZILLA_PRESUME_ARMV7)
     bool armv7_enabled = check_armv7();
 #  endif
 #  if !defined(MOZILLA_PRESUME_NEON)
     bool neon_enabled = check_neon();
 #  endif
   } // namespace arm_private
 } // namespace mozilla
 #endif // MOZILLA_ARM_HAVE_CPUID_DETECTION

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mozglue/build/arm.cpp@97036ab72558 (annotated)

mozglue/build/arm.cpp