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/* wrmsr.c - Write CPU model-specific registers. */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2019 Free Software Foundation, Inc.
* Based on gcc/gcc/config/i386/driver-i386.c
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/dl.h>
#include <grub/misc.h>
#include <grub/mm.h>
#include <grub/env.h>
#include <grub/command.h>
#include <grub/extcmd.h>
#include <grub/lockdown.h>
#include <grub/i18n.h>
#include <grub/i386/cpuid.h>
#include <grub/i386/wrmsr.h>
GRUB_MOD_LICENSE("GPLv3+");
static grub_command_t cmd_write;
static grub_err_t
grub_cmd_msr_write (grub_command_t cmd __attribute__ ((unused)), int argc, char **argv)
{
grub_uint32_t manufacturer[3], max_cpuid, a, b, c, features, addr;
grub_uint64_t value;
const char *ptr;
/*
* The CPUID instruction should be used to determine whether MSRs
* are supported. (CPUID.01H:EDX[5] = 1)
*/
if (!grub_cpu_is_cpuid_supported ())
return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
grub_cpuid (0, max_cpuid, manufacturer[0], manufacturer[2], manufacturer[1]);
if (max_cpuid < 1)
return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
grub_cpuid (1, a, b, c, features);
if (!(features & (1 << 5)))
return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
if (argc != 2)
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("two arguments expected"));
grub_errno = GRUB_ERR_NONE;
ptr = argv[0];
addr = grub_strtoul (ptr, &ptr, 0);
if (grub_errno != GRUB_ERR_NONE)
return grub_errno;
if (*ptr != '\0')
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid argument"));
ptr = argv[1];
value = grub_strtoull (ptr, &ptr, 0);
if (grub_errno != GRUB_ERR_NONE)
return grub_errno;
if (*ptr != '\0')
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid argument"));
grub_msr_write (addr, value);
return GRUB_ERR_NONE;
}
GRUB_MOD_INIT(wrmsr)
{
cmd_write = grub_register_command_lockdown ("wrmsr", grub_cmd_msr_write, N_("ADDR VALUE"),
N_("Write a value to a CPU model specific register."));
}
GRUB_MOD_FINI(wrmsr)
{
grub_unregister_command (cmd_write);
}
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