[arm] Correctly detect ARMv8 platforms with old kernels.

src/base/cpu.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/base/cpu.h"
 
 #if V8_LIBC_MSVCRT
 #include <intrin.h>  // __cpuid()
 #endif
 #if V8_OS_LINUX
@@ skipping 450 matching lines @@
   // The list is well-known, unlike the the output of
   // the 'Processor' field which can vary greatly.
   // See the definition of the 'proc_arch' array in
   // $KERNEL/arch/arm/kernel/setup.c and the 'c_show' function in
   // same file.
   char* architecture = cpu_info.ExtractField("CPU architecture");
   if (architecture != NULL) {
     char* end;
     architecture_ = strtol(architecture, &end, 10);
     if (end == architecture) {
-      architecture_ = 0;
+      // Kernels older than 3.18 report "CPU architecture: AArch64" on ARMv8.
+      if (strcmp(architecture, "AArch64") == 0) {
+        architecture_ = 8;
+      } else {
+        architecture_ = 0;
+      }
     }
     delete[] architecture;
 
     // Unfortunately, it seems that certain ARMv6-based CPUs
     // report an incorrect architecture number of 7!
     //
     // See http://code.google.com/p/android/issues/detail?id=10812
     //
     // We try to correct this by looking at the 'elf_platform'
     // field reported by the 'Processor' field, which is of the
@@ skipping 213 matching lines @@
       part_ = PPC_POWER5;
       break;
   }
 #endif  // V8_OS_AIX
 #endif  // !USE_SIMULATOR
 #endif  // V8_HOST_ARCH_PPC
 }
 
 }  // namespace base
 }  // namespace v8