94 lines
2.4 KiB
C
94 lines
2.4 KiB
C
/* cpuid.c - test for CPU features */
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2006, 2007 Free Software Foundation, Inc.
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* Based on gcc/gcc/config/i386/driver-i386.c
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <grub/normal.h>
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#include <grub/dl.h>
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#include <grub/arg.h>
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#include <grub/misc.h>
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#include <grub/mm.h>
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#include <grub/env.h>
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#define cpuid(num,a,b,c,d) \
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asm volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1" \
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: "=a" (a), "=r" (b), "=c" (c), "=d" (d) \
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: "0" (num))
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#define bit_LM (1 << 29)
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unsigned char has_longmode = 0;
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static const struct grub_arg_option options[] =
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{
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{"long-mode", 'l', 0, "check for long mode flag (default)", 0, 0},
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{0, 0, 0, 0, 0, 0}
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};
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static grub_err_t
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grub_cmd_cpuid (struct grub_arg_list *state __attribute__ ((unused)), int argc,
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char **args)
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{
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return !has_longmode;
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}
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GRUB_MOD_INIT(cpuid)
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{
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#ifdef __x86_64__
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/* grub-emu */
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has_longmode = 1;
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#else
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unsigned int eax, ebx, ecx, edx;
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unsigned int max_level;
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unsigned int ext_level;
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/* See if we can use cpuid. */
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asm volatile ("pushfl; pushfl; popl %0; movl %0,%1; xorl %2,%0;"
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"pushl %0; popfl; pushfl; popl %0; popfl"
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: "=&r" (eax), "=&r" (ebx)
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: "i" (0x00200000));
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if (((eax ^ ebx) & 0x00200000) == 0)
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goto done;
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/* Check the highest input value for eax. */
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cpuid (0, eax, ebx, ecx, edx);
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/* We only look at the first four characters. */
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max_level = eax;
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if (max_level == 0)
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goto done;
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cpuid (0x80000000, eax, ebx, ecx, edx);
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ext_level = eax;
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if (ext_level < 0x80000000)
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goto done;
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cpuid (0x80000001, eax, ebx, ecx, edx);
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has_longmode = !!(edx & bit_LM);
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done:
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#endif
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grub_register_command ("cpuid", grub_cmd_cpuid, GRUB_COMMAND_FLAG_CMDLINE,
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"cpuid", "Check for CPU features", options);
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}
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GRUB_MOD_FINI(cpuid)
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{
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grub_unregister_command ("cpuid");
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}
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