48 lines
879 B
PHP
48 lines
879 B
PHP
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/*
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* For starting coreboot in long mode.
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*
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* For reference see "AMD64 ArchitectureProgrammer's Manual Volume 2",
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* Document 24593-Rev. 3.31-July 2019 Chapter 5.3
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*
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* Clobbers: eax, ecx, edx
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*/
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#if defined(__x86_64__)
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.code32
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#if (CONFIG_ARCH_X86_64_PGTBL_LOC & 0xfff) > 0
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#error pagetables must be 4KiB aligned!
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#endif
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#include <cpu/x86/msr.h>
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#include <arch/rom_segs.h>
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setup_longmode:
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/* Get page table address */
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movl $(CONFIG_ARCH_X86_64_PGTBL_LOC), %eax
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/* load identity mapped page tables */
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movl %eax, %cr3
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/* enable PAE */
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movl %cr4, %eax
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btsl $5, %eax
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movl %eax, %cr4
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/* enable long mode */
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movl $(IA32_EFER), %ecx
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rdmsr
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btsl $8, %eax
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wrmsr
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/* enable paging */
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movl %cr0, %eax
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btsl $31, %eax
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movl %eax, %cr0
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/* use long jump to switch to 64-bit code segment */
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ljmp $ROM_CODE_SEG64, $__longmode_start
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.code64
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__longmode_start:
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#endif
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