| | 1 | org 0xA8000 |
| | 2 | [bits 16] |
| | 3 | entry: |
| | 4 | mov ax, 0xA800 ; Take us out of flat unreal mode, |
| | 5 | mov ds, ax ; and put us in true real mode. |
| | 6 | mov es, ax |
| | 7 | mov fs, ax |
| | 8 | mov gs, ax |
| | 9 | mov ss, ax |
| | 10 | jmp 0xA800:(entry2-0xA8000) ; Long jump to a correct cs. |
| | 11 | entry2: |
| | 12 | lgdt [(gdtr-0xA8000)] ; Set up a new GDT. |
| | 13 | mov eax, 0x1 |
| | 14 | mov cr0, eax ; ... and enter pmode! |
| | 15 | jmp long 0x10:continue ; Now longjmp into the new code. |
| | 16 | [bits 32] |
| | 17 | continue: |
| | 18 | mov ax, 0x08 ; Set up segment selectors. |
| | 19 | mov ds, ax |
| | 20 | mov es, ax |
| | 21 | mov fs, ax |
| | 22 | mov gs, ax |
| | 23 | mov ss, ax |
| | 24 | mov esp, [dataptr] ; Load stack pointer. |
| | 25 | |
| | 26 | mov al, [needclear] ; Has the aseg been run before? |
| | 27 | cmp al, 0 ; If so, |
| | 28 | jz noclear ; don't clear BSS. |
| | 29 | mov al, 0 ; Otherwise, clear BSS. |
| | 30 | mov edi, [dataptr+4] |
| | 31 | mov ecx, [dataptr+8] |
| | 32 | rep stosb |
| | 33 | mov [needclear], al |
| | 34 | |
| | 35 | noclear: |
| | 36 | mov eax, [dataptr+12] ; Load target jump address |
| | 37 | call eax ; then jump into C. |
| | 38 | |
| | 39 | rsm ; and leave SMM |
| | 40 | |
| | 41 | align 0x4 |
| | 42 | gdtr: |
| | 43 | db 0x17, 0x00 |
| | 44 | dd gdt |
| | 45 | align 0x4 |
| | 46 | gdt: |
| | 47 | db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 ; initial null entry |
| | 48 | db 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x93, 0xCF, 0x00 ; data segment |
| | 49 | db 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x9B, 0xCF, 0x00 ; code segment |
| | 50 | |
| | 51 | needclear: |
| | 52 | db 0x01 |
| | 53 | |
| | 54 | dataptr: |
| | 55 | ; 4 bytes of stack top |
| | 56 | ; 4 bytes of BSS start |
| | 57 | ; 4 bytes of BSS length |
| | 58 | ; 4 bytes of C entry point |
| | 59 | ; These show up |
git.joshuawise.com / netwatch.git / blame_incremental