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