75 lines
2.0 KiB
C
75 lines
2.0 KiB
C
/*
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* VAS_EBOOT -- GRand Unified Bootloader
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* Copyright (C) 2019 Free Software Foundation, Inc.
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*
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* VAS_EBOOT 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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* VAS_EBOOT 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 VAS_EBOOT. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef VAS_EBOOT_I386_MSR_H
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#define VAS_EBOOT_I386_MSR_H 1
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#include <VasEBoot/err.h>
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#include <VasEBoot/i386/cpuid.h>
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#include <VasEBoot/types.h>
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static inline VasEBoot_err_t
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VasEBoot_cpu_is_msr_supported (void)
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{
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VasEBoot_uint32_t eax, ebx, ecx, edx;
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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 (!VasEBoot_cpu_is_cpuid_supported ())
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return VAS_EBOOT_ERR_BAD_DEVICE;
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VasEBoot_cpuid (0, eax, ebx, ecx, edx);
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if (eax < 1)
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return VAS_EBOOT_ERR_BAD_DEVICE;
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VasEBoot_cpuid (1, eax, ebx, ecx, edx);
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if (!(edx & (1 << 5)))
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return VAS_EBOOT_ERR_BAD_DEVICE;
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return VAS_EBOOT_ERR_NONE;
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}
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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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static inline VasEBoot_uint64_t
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VasEBoot_rdmsr (VasEBoot_uint32_t msr_id)
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{
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VasEBoot_uint32_t low, high;
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asm volatile ("rdmsr" : "=a" (low), "=d" (high) : "c" (msr_id));
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return ((VasEBoot_uint64_t) high << 32) | low;
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}
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static inline void
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VasEBoot_wrmsr (VasEBoot_uint32_t msr_id, VasEBoot_uint64_t msr_value)
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{
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VasEBoot_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 /* VAS_EBOOT_I386_MSR_H */
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