46f5d51343
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>
36 lines
1.1 KiB
C
36 lines
1.1 KiB
C
/*
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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
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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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#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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