crypto: disable NSS AES-NI support when AVX is disabled by OS.

base/cpu.cc

 // Copyright (c) 2012 The Chromium 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 "base/cpu.h"
 
 #include <string.h>
 
 #include <algorithm>
 
+#include "base/basictypes.h"
 #include "build/build_config.h"
 
 #if defined(ARCH_CPU_X86_FAMILY)
 #if defined(_MSC_VER)
 #include <intrin.h>
+#include <immintrin.h>  // For _xgetbv()
 #endif
 #endif
 
 namespace base {
 
 CPU::CPU()
   : signature_(0),
     type_(0),
     family_(0),
     model_(0),
     stepping_(0),
     ext_model_(0),
     ext_family_(0),
     has_mmx_(false),
     has_sse_(false),
     has_sse2_(false),
     has_sse3_(false),
     has_ssse3_(false),
     has_sse41_(false),
     has_sse42_(false),
+    has_avx_(false),
+    has_avx_hardware_(false),
     has_non_stop_time_stamp_counter_(false),
     cpu_vendor_("unknown") {
   Initialize();
 }
 
+namespace {
+
 #if defined(ARCH_CPU_X86_FAMILY)
 #ifndef _MSC_VER
 
 #if defined(__pic__) && defined(__i386__)
 
 void __cpuid(int cpu_info[4], int info_type) {
   __asm__ volatile (
     "mov %%ebx, %%edi\n"
     "cpuid\n"
     "xchg %%edi, %%ebx\n"
@@ skipping 24 matching lines @@
 
 void __cpuidex(int cpu_info[4], int info_type, int info_index) {
   __asm__ volatile (
     "cpuid \n\t"
     : "=a"(cpu_info[0]), "=b"(cpu_info[1]), "=c"(cpu_info[2]), "=d"(cpu_info[3])
     : "a"(info_type), "c"(info_index)
   );
 }
 
 #endif
-#endif  // _MSC_VER
+
+// _xgetbv returns the value of an Intel Extended Control Register (XCR).
+// Currently only XCR0 is defined by Intel so |xcr| should always be zero.
+uint64 _xgetbv(uint32 xcr) {
+  uint32 eax, edx;
+
+  __asm__ volatile ("xgetbv" : "=a" (eax), "=d" (edx) : "c" (xcr));
+  return (static_cast<uint64>(edx) << 32) | eax;
+}
+
+#endif  // !_MSC_VER
 #endif  // ARCH_CPU_X86_FAMILY
 
+}  // anonymous namespace
+
 void CPU::Initialize() {
 #if defined(ARCH_CPU_X86_FAMILY)
   int cpu_info[4] = {-1};
   char cpu_string[48];
 
   // __cpuid with an InfoType argument of 0 returns the number of
   // valid Ids in CPUInfo[0] and the CPU identification string in
   // the other three array elements. The CPU identification string is
   // not in linear order. The code below arranges the information
   // in a human readable form. The human readable order is CPUInfo[1] |
   // CPUInfo[3] | CPUInfo[2]. CPUInfo[2] and CPUInfo[3] are swapped
   // before using memcpy to copy these three array elements to cpu_string.
   __cpuid(cpu_info, 0);
   int num_ids = cpu_info[0];
   std::swap(cpu_info[2], cpu_info[3]);
   memcpy(cpu_string, &cpu_info[1], 3 * sizeof(cpu_info[1]));
   cpu_vendor_.assign(cpu_string, 3 * sizeof(cpu_info[1]));
 
   // Interpret CPU feature information.
   if (num_ids > 0) {
     __cpuid(cpu_info, 1);
     signature_ = cpu_info[0];
     stepping_ = cpu_info[0] & 0xf;
     model_ = ((cpu_info[0] >> 4) & 0xf) + ((cpu_info[0] >> 12) & 0xf0);
     family_ = (cpu_info[0] >> 8) & 0xf;
     type_ = (cpu_info[0] >> 12) & 0x3;
     ext_model_ = (cpu_info[0] >> 16) & 0xf;
     ext_family_ = (cpu_info[0] >> 20) & 0xff;
-    has_mmx_ = (cpu_info[3] & 0x00800000) != 0;
-    has_sse_ = (cpu_info[3] & 0x02000000) != 0;
-    has_sse2_ = (cpu_info[3] & 0x04000000) != 0;
-    has_sse3_ = (cpu_info[2] & 0x00000001) != 0;
+    has_mmx_ =   (cpu_info[3] & 0x00800000) != 0;
+    has_sse_ =   (cpu_info[3] & 0x02000000) != 0;
+    has_sse2_ =  (cpu_info[3] & 0x04000000) != 0;
+    has_sse3_ =  (cpu_info[2] & 0x00000001) != 0;
     has_ssse3_ = (cpu_info[2] & 0x00000200) != 0;
     has_sse41_ = (cpu_info[2] & 0x00080000) != 0;
     has_sse42_ = (cpu_info[2] & 0x00100000) != 0;
-    has_avx_ = (cpu_info[2] & 0x10000000) != 0;
+    has_avx_hardware_ =
+                 (cpu_info[2] & 0x10000000) != 0;
+    /* AVX instructions will generate an illegal instruction exception unless
+     *   a) they are supported by the CPU,
+     *   b) XSAVE is supported by the CPU and
+     *   c) XSAVE is enabled by the kernel.
+     * See http://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled */
+    has_avx_ =
+      has_avx_hardware_ &&
+      (cpu_info[2] & 0x08000000) == 0x08000000 /* OSXSAVE */ &&
+      (_xgetbv(0) & 6) == 6 /* XSAVE enabled by kernel */;
   }
 
   // Get the brand string of the cpu.
   __cpuid(cpu_info, 0x80000000);
   const int parameter_end = 0x80000004;
   int max_parameter = cpu_info[0];
 
   if (cpu_info[0] >= parameter_end) {
     char* cpu_string_ptr = cpu_string;
 
@@ skipping 26 matching lines @@
   if (has_sse42()) return SSE42;
   if (has_sse41()) return SSE41;
   if (has_ssse3()) return SSSE3;
   if (has_sse3()) return SSE3;
   if (has_sse2()) return SSE2;
   if (has_sse()) return SSE;
   return PENTIUM;
 }
 
 }  // namespace base