220d6d8071
Added first ISR (ISR0). git-svn-id: https://spexeah.com:8443/svn/Asuro@37 6dbc8c32-bb84-406f-8558-d1cf31a0ab0c
66 lines
1.8 KiB
ObjectPascal
66 lines
1.8 KiB
ObjectPascal
unit gdt;
|
|
|
|
interface
|
|
|
|
type
|
|
TGDT_Entry = bitpacked record
|
|
limit_low : uint16;
|
|
base_low : uint16;
|
|
base_middle : uint8;
|
|
access : uint8;
|
|
granularity : uint8;
|
|
base_high : uint8;
|
|
end;
|
|
PGDT_Entry = ^TGDT_Entry;
|
|
|
|
TGDT_Pointer = bitpacked record
|
|
limit : uint16;
|
|
base : uint32;
|
|
end;
|
|
|
|
var
|
|
gdt_entries : array[0..4] of TGDT_Entry;
|
|
gdt_pointer : TGDT_Pointer;
|
|
|
|
procedure init();
|
|
|
|
implementation
|
|
|
|
procedure flush_gdt(gdt_pointer : uint32); assembler; nostackframe;
|
|
asm
|
|
MOV EAX, gdt_pointer
|
|
LGDT [EAX]
|
|
MOV AX, $10
|
|
MOV DS, AX
|
|
MOV ES, AX
|
|
MOV FS, AX
|
|
MOV GS, AX
|
|
MOV SS, AX
|
|
db $EA // Bypass stupid inline ASM restrictions-
|
|
dw @@flush, $08 // by assembling the farjump instruction ourselves.
|
|
@@flush: // It's just data, honest gov'.
|
|
end;
|
|
|
|
procedure set_gate(Gate_Number : uint32; Base : uint32; Limit : uint32; Access : uint8; Granularity : uint8);
|
|
begin
|
|
gdt_entries[Gate_Number].base_low := (Base AND $FFFF);
|
|
gdt_entries[Gate_Number].base_middle := (Base SHR 16) AND $FF;
|
|
gdt_entries[Gate_Number].base_high := (Base SHR 24) AND $FF;
|
|
gdt_entries[Gate_Number].limit_low := (Limit AND $FFFF);
|
|
gdt_entries[Gate_Number].granularity := ((Limit SHR 16) AND $0F) OR (Granularity AND $F0);
|
|
gdt_entries[Gate_Number].access := Access;
|
|
end;
|
|
|
|
procedure init();
|
|
begin
|
|
gdt_pointer.limit := (sizeof(TGDT_Entry) * 5) - 1;
|
|
gdt_pointer.base := uint32(@gdt_entries);
|
|
set_gate($00, $00, $00, $00, $00);
|
|
set_gate($01, $00, $FFFFFFFF, $9A, $CF);
|
|
set_gate($02, $00, $FFFFFFFF, $92, $CF);
|
|
set_gate($03, $00, $FFFFFFFF, $FA, $CF);
|
|
set_gate($04, $00, $FFFFFFFF, $F2, $CF);
|
|
flush_gdt(uint32(@gdt_pointer))
|
|
end;
|
|
|
|
end. |