diff --git a/docs/grub.texi b/docs/grub.texi index ecaba9d5c..308b25074 100644 --- a/docs/grub.texi +++ b/docs/grub.texi @@ -3931,6 +3931,7 @@ you forget a command, you can run the command @command{help} * play:: Play a tune * probe:: Retrieve device info * pxe_unload:: Unload the PXE environment +* rdmsr:: Read values from model-specific registers * read:: Read user input * reboot:: Reboot your computer * regexp:: Test if regular expression matches string @@ -3953,6 +3954,7 @@ you forget a command, you can run the command @command{help} * verify_detached:: Verify detached digital signature * videoinfo:: List available video modes @comment * xen_*:: Xen boot commands for AArch64 +* wrmsr:: Write values to model-specific registers * xen_hypervisor:: Load xen hypervisor binary (only on AArch64) * xen_module:: Load xen modules for xen hypervisor (only on AArch64) @end menu @@ -4785,6 +4787,24 @@ This command is only available on PC BIOS systems. @end deffn +@node rdmsr +@subsection rdmsr + +@deffn Command: rdmsr 0xADDR [-v VARNAME] +Read a model-specific register at address 0xADDR. If the parameter +@option{-v} is used and an environment variable @var{VARNAME} is +given, set that environment variable to the value that was read. + +Please note that on SMP systems, reading from a MSR that has a +scope per hardware thread, implies that the value that is returned +only applies to the particular cpu/core/thread that runs 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. +@end deffn + + @node read @subsection read @@ -5223,6 +5243,21 @@ successfully. If validation fails, it is set to a non-zero value. List available video modes. If resolution is given, show only matching modes. @end deffn +@node wrmsr +@subsection wrmsr + +@deffn Command: wrmsr 0xADDR 0xVALUE +Write a 0xVALUE to a model-specific register at address 0xADDR. + +Please note that on SMP systems, writing to a MSR that has a scope +per hardware thread, implies that the value that is written +only applies to the particular cpu/core/thread that runs 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. +@end deffn + @node xen_hypervisor @subsection xen_hypervisor @@ -5716,11 +5751,11 @@ boot and the shim. This functionality is provided by the shim_lock module. It is recommend to build in this and other required modules into the @file{core.img}. All modules not stored in the @file{core.img} and the ACPI tables for the @command{acpi} command have to be signed, e.g. using PGP. Additionally, the -@command{iorw} and the @command{memrw} commands are prohibited if the UEFI -secure boot is enabled. This is done due to security reasons. All above -mentioned requirements are enforced by the shim_lock module. And itself it -is a persistent module which means that it cannot be unloaded if it was -loaded into the memory. +@command{iorw}, the @command{memrw} and the @command{wrmsr} commands are +prohibited if the UEFI secure boot is enabled. This is done due to +security reasons. All above mentioned requirements are enforced by the +shim_lock module. And itself it is a persistent module which means that +it cannot be unloaded if it was loaded into the memory. @node Measured Boot @section Measuring boot components @@ -5831,6 +5866,8 @@ to install to is specified, UUID is used instead as well. @item USB @tab yes @tab yes @tab yes @tab yes @item chainloader @tab local @tab yes @tab yes @tab no @item cpuid @tab partial @tab partial @tab partial @tab partial +@item rdmsr @tab partial @tab partial @tab partial @tab partial +@item wrmsr @tab partial @tab partial @tab partial @tab partial @item hints @tab guess @tab guess @tab guess @tab guess @item PCI @tab yes @tab yes @tab yes @tab yes @item badram @tab yes @tab yes @tab yes @tab yes @@ -5850,6 +5887,8 @@ to install to is specified, UUID is used instead as well. @item USB @tab yes @tab yes @tab yes @tab no @item chainloader @tab local @tab local @tab no @tab local @item cpuid @tab partial @tab partial @tab partial @tab no +@item rdmsr @tab partial @tab partial @tab partial @tab no +@item wrmsr @tab partial @tab partial @tab partial @tab no @item hints @tab guess @tab guess @tab good @tab guess @item PCI @tab yes @tab yes @tab yes @tab no @item badram @tab yes @tab yes @tab no @tab yes @@ -5869,6 +5908,8 @@ to install to is specified, UUID is used instead as well. @item USB @tab yes @tab no @tab no @tab no @item chainloader @tab yes @tab no @tab no @tab no @item cpuid @tab no @tab no @tab no @tab no +@item rdmsr @tab no @tab no @tab no @tab no +@item wrmsr @tab no @tab no @tab no @tab no @item hints @tab good @tab good @tab good @tab no @item PCI @tab yes @tab no @tab no @tab no @item badram @tab yes (*) @tab no @tab no @tab no @@ -5888,6 +5929,8 @@ to install to is specified, UUID is used instead as well. @item USB @tab N/A @tab yes @tab no @item chainloader @tab yes @tab no @tab yes @item cpuid @tab no @tab no @tab yes +@item rdmsr @tab no @tab no @tab yes +@item wrmsr @tab no @tab no @tab yes @item hints @tab guess @tab no @tab no @item PCI @tab no @tab no @tab no @item badram @tab yes (*) @tab no @tab no diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def index ea8b99823..43ed42191 100644 --- a/grub-core/Makefile.core.def +++ b/grub-core/Makefile.core.def @@ -2485,3 +2485,13 @@ module = { common = loader/i386/xen_file64.c; extra_dist = loader/i386/xen_fileXX.c; }; +module = { + name = rdmsr; + common = commands/i386/rdmsr.c; + enable = x86; +}; +module = { + name = wrmsr; + common = commands/i386/wrmsr.c; + enable = x86; +}; diff --git a/grub-core/commands/efi/shim_lock.c b/grub-core/commands/efi/shim_lock.c index 83568cb2b..764098cfc 100644 --- a/grub-core/commands/efi/shim_lock.c +++ b/grub-core/commands/efi/shim_lock.c @@ -43,7 +43,7 @@ static grub_efi_guid_t shim_lock_guid = GRUB_EFI_SHIM_LOCK_GUID; static grub_efi_shim_lock_protocol_t *sl; /* List of modules which cannot be loaded if UEFI secure boot mode is enabled. */ -static const char * const disabled_mods[] = {"iorw", "memrw", NULL}; +static const char * const disabled_mods[] = {"iorw", "memrw", "wrmsr", NULL}; static grub_err_t shim_lock_init (grub_file_t io, enum grub_file_type type, diff --git a/grub-core/commands/i386/rdmsr.c b/grub-core/commands/i386/rdmsr.c new file mode 100644 index 000000000..15b9adfca --- /dev/null +++ b/grub-core/commands/i386/rdmsr.c @@ -0,0 +1,102 @@ +/* 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 . + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +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; + 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); +} diff --git a/grub-core/commands/i386/wrmsr.c b/grub-core/commands/i386/wrmsr.c new file mode 100644 index 000000000..9c5e510eb --- /dev/null +++ b/grub-core/commands/i386/wrmsr.c @@ -0,0 +1,93 @@ +/* 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 . + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +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; + 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 ("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); +} diff --git a/include/grub/i386/rdmsr.h b/include/grub/i386/rdmsr.h new file mode 100644 index 000000000..bddb7bbbb --- /dev/null +++ b/include/grub/i386/rdmsr.h @@ -0,0 +1,36 @@ +/* + * GRUB -- GRand Unified Bootloader + * Copyright (C) 2019 Free Software Foundation, Inc. + * + * 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 . + */ + +#ifndef GRUB_RDMSR_H +#define GRUB_RDMSR_H 1 + +/* + * TODO: Add a general protection exception handler. + * Accessing a reserved or unimplemented MSR address results in a GP#. + */ + +extern inline grub_uint64_t grub_msr_read (grub_uint32_t msr_id) +{ + grub_uint32_t low, high; + + asm volatile ("rdmsr" : "=a" (low), "=d" (high) : "c" (msr_id)); + + return ((grub_uint64_t)high << 32) | low; +} + +#endif /* GRUB_RDMSR_H */ diff --git a/include/grub/i386/wrmsr.h b/include/grub/i386/wrmsr.h new file mode 100644 index 000000000..e14d7807f --- /dev/null +++ b/include/grub/i386/wrmsr.h @@ -0,0 +1,34 @@ +/* + * GRUB -- GRand Unified Bootloader + * Copyright (C) 2019 Free Software Foundation, Inc. + * + * 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 . + */ + +#ifndef GRUB_WRMSR_H +#define GRUB_WRMSR_H 1 + +/* + * TODO: Add a general protection exception handler. + * Accessing a reserved or unimplemented MSR address results in a GP#. + */ + +extern inline void grub_msr_write(grub_uint32_t msr_id, grub_uint64_t msr_value) +{ + grub_uint32_t low = msr_value, high = msr_value >> 32; + + asm volatile ("wrmsr" : : "c" (msr_id), "a" (low), "d" (high)); +} + +#endif /* GRUB_WRMSR_H */