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/* rdmsr.c - Read 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/i18n.h>
#include <grub/i386/cpuid.h>
#include <grub/i386/rdmsr.h>
GRUB_MOD_LICENSE("GPLv3+");
static grub_extcmd_t cmd_read;
static const struct grub_arg_option options[] =
{
{0, 'v', 0, N_("Save read value into variable VARNAME."),
N_("VARNAME"), ARG_TYPE_STRING},
{0, 0, 0, 0, 0, 0}
};
static grub_err_t
grub_cmd_msr_read (grub_extcmd_context_t ctxt, int argc, char **argv)
{
grub_uint32_t manufacturer[3], max_cpuid, a, b, c, features, addr;
grub_uint64_t value;
const char *ptr;
char buf[sizeof("1122334455667788")];
/*
* 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 != 1)
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument 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"));
value = grub_msr_read (addr);
if (ctxt->state[0].set)
{
grub_snprintf (buf, sizeof(buf), "%llx", (unsigned long long) value);
grub_env_set (ctxt->state[0].arg, buf);
}
else
grub_printf ("0x%llx\n", (unsigned long long) value);
return GRUB_ERR_NONE;
}
GRUB_MOD_INIT(rdmsr)
{
cmd_read = grub_register_extcmd ("rdmsr", grub_cmd_msr_read, 0, N_("ADDR"),
N_("Read a CPU model specific register."),
options);
}
GRUB_MOD_FINI(rdmsr)
{
grub_unregister_extcmd (cmd_read);
}
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