msr: Add new MSR modules (rdmsr/wrmsr)
In order to be able to read from and write to model-specific registers, two new modules are added. They are i386 specific, as the cpuid module. rdmsr module registers the command rdmsr that allows reading from a MSR. wrmsr module registers the command wrmsr that allows writing to a MSR. wrmsr module is disabled if UEFI secure boot is enabled. Please note that on SMP systems, interacting with a MSR that has a scope per hardware thread, implies that the value only applies to the particular cpu/core/thread that ran the command. Also, if you specify a reserved or unimplemented MSR address, it will cause a general protection exception (which is not currently being handled) and the system will reboot. Signed-off-by: Jesús Diéguez Fernández <jesusdf@gmail.com> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
parent
3611c4f42e
commit
46f5d51343
7 changed files with 324 additions and 6 deletions
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@ -3931,6 +3931,7 @@ you forget a command, you can run the command @command{help}
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* play:: Play a tune
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* probe:: Retrieve device info
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* pxe_unload:: Unload the PXE environment
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* rdmsr:: Read values from model-specific registers
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* read:: Read user input
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* reboot:: Reboot your computer
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* regexp:: Test if regular expression matches string
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@ -3953,6 +3954,7 @@ you forget a command, you can run the command @command{help}
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* verify_detached:: Verify detached digital signature
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* videoinfo:: List available video modes
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@comment * xen_*:: Xen boot commands for AArch64
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* wrmsr:: Write values to model-specific registers
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* xen_hypervisor:: Load xen hypervisor binary (only on AArch64)
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* xen_module:: Load xen modules for xen hypervisor (only on AArch64)
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@end menu
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@ -4785,6 +4787,24 @@ This command is only available on PC BIOS systems.
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@end deffn
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@node rdmsr
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@subsection rdmsr
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@deffn Command: rdmsr 0xADDR [-v VARNAME]
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Read a model-specific register at address 0xADDR. If the parameter
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@option{-v} is used and an environment variable @var{VARNAME} is
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given, set that environment variable to the value that was read.
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Please note that on SMP systems, reading from a MSR that has a
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scope per hardware thread, implies that the value that is returned
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only applies to the particular cpu/core/thread that runs the command.
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Also, if you specify a reserved or unimplemented MSR address, it will
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cause a general protection exception (which is not currently being handled)
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and the system will reboot.
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@end deffn
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@node read
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@subsection read
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@ -5223,6 +5243,21 @@ successfully. If validation fails, it is set to a non-zero value.
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List available video modes. If resolution is given, show only matching modes.
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@end deffn
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@node wrmsr
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@subsection wrmsr
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@deffn Command: wrmsr 0xADDR 0xVALUE
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Write a 0xVALUE to a model-specific register at address 0xADDR.
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Please note that on SMP systems, writing to a MSR that has a scope
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per hardware thread, implies that the value that is written
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only applies to the particular cpu/core/thread that runs the command.
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Also, if you specify a reserved or unimplemented MSR address, it will
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cause a general protection exception (which is not currently being handled)
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and the system will reboot.
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@end deffn
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@node xen_hypervisor
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@subsection xen_hypervisor
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@ -5716,11 +5751,11 @@ boot and the shim. This functionality is provided by the shim_lock module. It
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is recommend to build in this and other required modules into the @file{core.img}.
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All modules not stored in the @file{core.img} and the ACPI tables for the
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@command{acpi} command have to be signed, e.g. using PGP. Additionally, the
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@command{iorw} and the @command{memrw} commands are prohibited if the UEFI
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secure boot is enabled. This is done due to security reasons. All above
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mentioned requirements are enforced by the shim_lock module. And itself it
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is a persistent module which means that it cannot be unloaded if it was
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loaded into the memory.
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@command{iorw}, the @command{memrw} and the @command{wrmsr} commands are
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prohibited if the UEFI secure boot is enabled. This is done due to
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security reasons. All above mentioned requirements are enforced by the
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shim_lock module. And itself it is a persistent module which means that
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it cannot be unloaded if it was loaded into the memory.
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@node Measured Boot
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@section Measuring boot components
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@ -5831,6 +5866,8 @@ to install to is specified, UUID is used instead as well.
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@item USB @tab yes @tab yes @tab yes @tab yes
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@item chainloader @tab local @tab yes @tab yes @tab no
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@item cpuid @tab partial @tab partial @tab partial @tab partial
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@item rdmsr @tab partial @tab partial @tab partial @tab partial
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@item wrmsr @tab partial @tab partial @tab partial @tab partial
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@item hints @tab guess @tab guess @tab guess @tab guess
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@item PCI @tab yes @tab yes @tab yes @tab yes
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@item badram @tab yes @tab yes @tab yes @tab yes
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@item USB @tab yes @tab yes @tab yes @tab no
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@item chainloader @tab local @tab local @tab no @tab local
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@item cpuid @tab partial @tab partial @tab partial @tab no
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@item rdmsr @tab partial @tab partial @tab partial @tab no
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@item wrmsr @tab partial @tab partial @tab partial @tab no
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@item hints @tab guess @tab guess @tab good @tab guess
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@item PCI @tab yes @tab yes @tab yes @tab no
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@item badram @tab yes @tab yes @tab no @tab yes
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@item USB @tab yes @tab no @tab no @tab no
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@item chainloader @tab yes @tab no @tab no @tab no
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@item cpuid @tab no @tab no @tab no @tab no
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@item rdmsr @tab no @tab no @tab no @tab no
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@item wrmsr @tab no @tab no @tab no @tab no
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@item hints @tab good @tab good @tab good @tab no
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@item PCI @tab yes @tab no @tab no @tab no
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@item badram @tab yes (*) @tab no @tab no @tab no
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@item USB @tab N/A @tab yes @tab no
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@item chainloader @tab yes @tab no @tab yes
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@item cpuid @tab no @tab no @tab yes
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@item rdmsr @tab no @tab no @tab yes
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@item wrmsr @tab no @tab no @tab yes
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@item hints @tab guess @tab no @tab no
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@item PCI @tab no @tab no @tab no
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@item badram @tab yes (*) @tab no @tab no
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@ -2485,3 +2485,13 @@ module = {
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common = loader/i386/xen_file64.c;
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extra_dist = loader/i386/xen_fileXX.c;
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};
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module = {
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name = rdmsr;
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common = commands/i386/rdmsr.c;
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enable = x86;
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};
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module = {
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name = wrmsr;
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common = commands/i386/wrmsr.c;
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enable = x86;
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};
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@ -43,7 +43,7 @@ static grub_efi_guid_t shim_lock_guid = GRUB_EFI_SHIM_LOCK_GUID;
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static grub_efi_shim_lock_protocol_t *sl;
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/* List of modules which cannot be loaded if UEFI secure boot mode is enabled. */
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static const char * const disabled_mods[] = {"iorw", "memrw", NULL};
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static const char * const disabled_mods[] = {"iorw", "memrw", "wrmsr", NULL};
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static grub_err_t
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shim_lock_init (grub_file_t io, enum grub_file_type type,
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102
grub-core/commands/i386/rdmsr.c
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102
grub-core/commands/i386/rdmsr.c
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@ -0,0 +1,102 @@
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/* rdmsr.c - Read CPU model-specific registers. */
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2019 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/dl.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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#include <grub/command.h>
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#include <grub/extcmd.h>
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#include <grub/i18n.h>
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#include <grub/i386/cpuid.h>
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#include <grub/i386/rdmsr.h>
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GRUB_MOD_LICENSE("GPLv3+");
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static grub_extcmd_t cmd_read;
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static const struct grub_arg_option options[] =
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{
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{0, 'v', 0, N_("Save read value into variable VARNAME."),
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N_("VARNAME"), ARG_TYPE_STRING},
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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_msr_read (grub_extcmd_context_t ctxt, int argc, char **argv)
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{
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grub_uint32_t manufacturer[3], max_cpuid, a, b, c, features, addr;
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grub_uint64_t value;
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char *ptr;
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char buf[sizeof("1122334455667788")];
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/*
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* The CPUID instruction should be used to determine whether MSRs
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* are supported. (CPUID.01H:EDX[5] = 1)
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*/
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if (! grub_cpu_is_cpuid_supported ())
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return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
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grub_cpuid (0, max_cpuid, manufacturer[0], manufacturer[2], manufacturer[1]);
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if (max_cpuid < 1)
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return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
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grub_cpuid (1, a, b, c, features);
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if (!(features & (1 << 5)))
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return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
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if (argc != 1)
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return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument expected"));
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grub_errno = GRUB_ERR_NONE;
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ptr = argv[0];
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addr = grub_strtoul (ptr, &ptr, 0);
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if (grub_errno != GRUB_ERR_NONE)
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return grub_errno;
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if (*ptr != '\0')
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return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid argument"));
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value = grub_msr_read (addr);
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if (ctxt->state[0].set)
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{
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grub_snprintf (buf, sizeof(buf), "%llx", (unsigned long long) value);
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grub_env_set (ctxt->state[0].arg, buf);
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}
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else
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grub_printf ("0x%llx\n", (unsigned long long) value);
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return GRUB_ERR_NONE;
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}
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GRUB_MOD_INIT(rdmsr)
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{
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cmd_read = grub_register_extcmd ("rdmsr", grub_cmd_msr_read, 0, N_("ADDR"),
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N_("Read a CPU model specific register."),
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options);
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}
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GRUB_MOD_FINI(rdmsr)
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{
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grub_unregister_extcmd (cmd_read);
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}
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93
grub-core/commands/i386/wrmsr.c
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93
grub-core/commands/i386/wrmsr.c
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@ -0,0 +1,93 @@
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/* wrmsr.c - Write CPU model-specific registers. */
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2019 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/dl.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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#include <grub/command.h>
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#include <grub/extcmd.h>
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#include <grub/i18n.h>
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#include <grub/i386/cpuid.h>
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#include <grub/i386/wrmsr.h>
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GRUB_MOD_LICENSE("GPLv3+");
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static grub_command_t cmd_write;
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static grub_err_t
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grub_cmd_msr_write (grub_command_t cmd __attribute__ ((unused)), int argc, char **argv)
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{
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grub_uint32_t manufacturer[3], max_cpuid, a, b, c, features, addr;
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grub_uint64_t value;
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char *ptr;
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/*
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* The CPUID instruction should be used to determine whether MSRs
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* are supported. (CPUID.01H:EDX[5] = 1)
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*/
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if (!grub_cpu_is_cpuid_supported ())
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return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
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grub_cpuid (0, max_cpuid, manufacturer[0], manufacturer[2], manufacturer[1]);
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if (max_cpuid < 1)
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return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
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grub_cpuid (1, a, b, c, features);
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if (!(features & (1 << 5)))
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return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
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if (argc != 2)
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return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("two arguments expected"));
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grub_errno = GRUB_ERR_NONE;
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ptr = argv[0];
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addr = grub_strtoul (ptr, &ptr, 0);
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if (grub_errno != GRUB_ERR_NONE)
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return grub_errno;
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if (*ptr != '\0')
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return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid argument"));
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ptr = argv[1];
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value = grub_strtoull (ptr, &ptr, 0);
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if (grub_errno != GRUB_ERR_NONE)
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return grub_errno;
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if (*ptr != '\0')
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return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid argument"));
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grub_msr_write (addr, value);
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return GRUB_ERR_NONE;
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}
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GRUB_MOD_INIT(wrmsr)
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{
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cmd_write = grub_register_command ("wrmsr", grub_cmd_msr_write, N_("ADDR VALUE"),
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N_("Write a value to a CPU model specific register."));
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}
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GRUB_MOD_FINI(wrmsr)
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{
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grub_unregister_command (cmd_write);
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}
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36
include/grub/i386/rdmsr.h
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36
include/grub/i386/rdmsr.h
Normal file
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@ -0,0 +1,36 @@
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2019 Free Software Foundation, Inc.
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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
|
||||
* 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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||||
*
|
||||
* 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.
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||||
*
|
||||
* You should have received a copy of the GNU General Public License
|
||||
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
|
||||
*/
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#ifndef GRUB_RDMSR_H
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#define GRUB_RDMSR_H 1
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/*
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* TODO: Add a general protection exception handler.
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* Accessing a reserved or unimplemented MSR address results in a GP#.
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*/
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extern inline grub_uint64_t grub_msr_read (grub_uint32_t msr_id)
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{
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grub_uint32_t low, high;
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asm volatile ("rdmsr" : "=a" (low), "=d" (high) : "c" (msr_id));
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return ((grub_uint64_t)high << 32) | low;
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}
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#endif /* GRUB_RDMSR_H */
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34
include/grub/i386/wrmsr.h
Normal file
34
include/grub/i386/wrmsr.h
Normal file
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@ -0,0 +1,34 @@
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/*
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||||
* GRUB -- GRand Unified Bootloader
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||||
* Copyright (C) 2019 Free Software Foundation, Inc.
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||||
*
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||||
* 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/>.
|
||||
*/
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||||
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#ifndef GRUB_WRMSR_H
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#define GRUB_WRMSR_H 1
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/*
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* TODO: Add a general protection exception handler.
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* Accessing a reserved or unimplemented MSR address results in a GP#.
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*/
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extern inline void grub_msr_write(grub_uint32_t msr_id, grub_uint64_t msr_value)
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{
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grub_uint32_t low = msr_value, high = msr_value >> 32;
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asm volatile ("wrmsr" : : "c" (msr_id), "a" (low), "d" (high));
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}
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#endif /* GRUB_WRMSR_H */
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Loading…
Reference in a new issue