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This commit is contained in:
Thomas Lovén 2017-11-15 21:43:00 +01:00
parent 4f9a4292e5
commit bb25b7ea35
1 changed files with 20 additions and 9 deletions
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29
src/kernel/boot/boot.S
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@ -11,7 +11,7 @@ BootStack:
.code32 .code32
error: error:
// Print "ERR!" in upper left corner //; Print "ERR!" in upper left corner
mov [0xb8000], dword ptr 0x4f004f00 mov [0xb8000], dword ptr 0x4f004f00
mov [0xb8004], dword ptr 0x4f004f00 mov [0xb8004], dword ptr 0x4f004f00
mov [0xb8000], byte ptr 'E' mov [0xb8000], byte ptr 'E'
@ -21,39 +21,39 @@ error:
jmp $ jmp $
check_cpuid: check_cpuid:
// Save EFLAGS //; Save EFLAGS
pushfd pushfd
// Try to modify EFLAGS.ID //; Try to modify EFLAGS.ID
pushfd pushfd
xor dword ptr [esp], 1<<21 xor dword ptr [esp], 1<<21
popfd popfd
//Read EFLAGS into eax //;Read EFLAGS into eax
pushfd pushfd
pop eax pop eax
// Restore original EFLAGS //; Restore original EFLAGS
popfd popfd
// Check if EFLAGS.ID was modified //; Check if EFLAGS.ID was modified
xor eax, [esp+4] xor eax, [esp+4]
and eax, 1<<21 and eax, 1<<21
jz error jz error
ret ret
check_longmode: check_longmode:
// cpuid 0x8000 0000 //; cpuid 0x8000 0000
mov eax, 0x80000000 mov eax, 0x80000000
cpuid cpuid
cmp eax, 0x80000001 cmp eax, 0x80000001
jb error jb error
// cpuid 0x8000 0001 //; cpuid 0x8000 0001
mov eax, 0x80000001 mov eax, 0x80000001
cpuid cpuid
// Test for long mode flag //; Test for long mode flag
test edx, 1<<29 test edx, 1<<29
jz error jz error
ret ret
@ -67,29 +67,39 @@ _start:
call check_cpuid call check_cpuid
call check_longmode call check_longmode
//; Set CR4.PAE
//; enabling Page Address Extension
mov eax, cr4 mov eax, cr4
or eax, 1<<5 or eax, 1<<5
mov cr4, eax mov cr4, eax
//; Load a P4 page table
mov eax, offset BootP4 mov eax, offset BootP4
mov cr3, eax mov cr3, eax
//; Set EFER.LME
//; enabling Long Mode
mov ecx, 0x0C0000080 mov ecx, 0x0C0000080
rdmsr rdmsr
or eax, 1<<8 or eax, 1<<8
wrmsr wrmsr
//; Set CR0.PG
//; enabling Paging
mov eax, cr0 mov eax, cr0
or eax, 1<<31 or eax, 1<<31
mov cr0, eax mov cr0, eax
//; Load a new GDT
lgdt [BootGDTp] lgdt [BootGDTp]
//; and update the code selector by a long jump
jmp 0x8:long_mode_start jmp 0x8:long_mode_start
.code64 .code64
long_mode_start: long_mode_start:
//; Clear out all other selectors
mov eax, 0x0 mov eax, 0x0
mov ss, eax mov ss, eax
mov ds, eax mov ds, eax
@ -97,4 +107,5 @@ _start:
mov fs, eax mov fs, eax
mov gs, eax mov gs, eax
//; Loop infinitely
jmp $ jmp $