commands/i386/cpuid.c

   1 /* cpuid.c - test for CPU features */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2006, 2007, 2009  Free Software Foundation, Inc.
   5  *  Based on gcc/gcc/config/i386/driver-i386.c
   6  *
   7  *  GRUB is free software: you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License as published by
   9  *  the Free Software Foundation, either version 3 of the License, or
  10  *  (at your option) any later version.
  11  *
  12  *  GRUB is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License
  18  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <grub/dl.h>
  22 #include <grub/misc.h>
  23 #include <grub/mm.h>
  24 #include <grub/env.h>
  25 #include <grub/command.h>
  26 #include <grub/extcmd.h>
  27 #include <grub/i386/cpuid.h>
  28
  29 #define cpuid(num,a,b,c,d) \
  30   asm volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1" \
  31                 : "=a" (a), "=r" (b), "=c" (c), "=d" (d)  \
  32                 : "0" (num))
  33
  34 static const struct grub_arg_option options[] =
  35   {
  36     {"long-mode", 'l', 0, "check for long mode flag (default)", 0, 0},
  37     {0, 0, 0, 0, 0, 0}
  38   };
  39
  40 #define bit_LM (1 << 29)
  41
  42 unsigned char grub_cpuid_has_longmode = 0;
  43
  44 static grub_err_t
  45 grub_cmd_cpuid (grub_extcmd_t cmd __attribute__ ((unused)),
  46                 int argc __attribute__ ((unused)),
  47                 char **args __attribute__ ((unused)))
  48 {
  49   return grub_cpuid_has_longmode ? GRUB_ERR_NONE
  50     : grub_error (GRUB_ERR_TEST_FAILURE, "false");
  51 }
  52
  53 static grub_extcmd_t cmd;
  54
  55 GRUB_MOD_INIT(cpuid)
  56 {
  57 #ifdef __x86_64__
  58   /* grub-emu */
  59   grub_cpuid_has_longmode = 1;
  60 #else
  61   unsigned int eax, ebx, ecx, edx;
  62   unsigned int max_level;
  63   unsigned int ext_level;
  64
  65   /* See if we can use cpuid.  */
  66   asm volatile ("pushfl; pushfl; popl %0; movl %0,%1; xorl %2,%0;"
  67                 "pushl %0; popfl; pushfl; popl %0; popfl"
  68                 : "=&r" (eax), "=&r" (ebx)
  69                 : "i" (0x00200000));
  70   if (((eax ^ ebx) & 0x00200000) == 0)
  71     goto done;
  72
  73   /* Check the highest input value for eax.  */
  74   cpuid (0, eax, ebx, ecx, edx);
  75   /* We only look at the first four characters.  */
  76   max_level = eax;
  77   if (max_level == 0)
  78     goto done;
  79
  80   cpuid (0x80000000, eax, ebx, ecx, edx);
  81   ext_level = eax;
  82   if (ext_level < 0x80000000)
  83     goto done;
  84
  85   cpuid (0x80000001, eax, ebx, ecx, edx);
  86   grub_cpuid_has_longmode = !!(edx & bit_LM);
  87 done:
  88 #endif
  89
  90   cmd = grub_register_extcmd ("cpuid", grub_cmd_cpuid, GRUB_COMMAND_FLAG_BOTH,
  91                               "cpuid [-l]", "Check for CPU features", options);
  92 }
  93
  94 GRUB_MOD_FINI(cpuid)
  95 {
  96   grub_unregister_extcmd (cmd);
  97 }