Lecture 1. How to Boot a PC. Andrei Pitiș. October 8, Operating Systems Practical. OSP Lecture 1, Booting 1/30

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1 Lecture 1 How to Boot a PC Andrei Pitiș Operating Systems Practical October 8, 2014 OSP Lecture 1, Booting 1/30

2 Table of Contents Hardware Processor Memory I/O subsystems Boot Process Keywords Resources Questions OSP Lecture 1, Booting 2/30

3 Outline Hardware Processor Memory I/O subsystems Boot Process Keywords Resources Questions OSP Lecture 1, Booting 3/30

4 Hardware Processor Protected mode Memory Segmentation I/O subsystems Interrupt controller (8259) Timer (8253/8254) Keyboard Display OSP Lecture 1, Booting 4/30

5 Outline Hardware Processor Memory I/O subsystems Boot Process Keywords Resources Questions OSP Lecture 1, Booting 5/30

6 Processor - x86 Registers: AX, BX, CX, DX SI, DI CS, DS, ES, SS SP, BP, IP Flags GDTR, LDTR, IDTR OSP Lecture 1, Booting 6/30

7 Protected Mode OSP Lecture 1, Booting 7/30

8 Outline Hardware Processor Memory I/O subsystems Boot Process Keywords Resources Questions OSP Lecture 1, Booting 8/30

9 Segmentation OSP Lecture 1, Booting 9/30

10 LDT/GDT LDT1 d e s c r i p t o r <,,, > ; dummy 07h d e s c r i p t o r <01000h, o f f s e t code1,, b> ; code 0Fh d e s c r i p t o r <01000h, o f f s e t data1,, b> ; data 17h d e s c r i p t o r <,, 2, b> ; s t a c k 1Fh d e s c r i p t o r <00001h, o f f s e t shdata,, b> ; s h a r e d data 27h GDT d e s c r i p t o r <,,, > ; dummy 0h d e s c r i p t o r <0FFFFh,,, b> ; code 8h d e s c r i p t o r <0FFFFh,,, b> ; data 10h d e s c r i p t o r <,,, b> ; s t a c k 18h d e s c r i p t o r <0FFFFh, 8000h, 0Bh, b> ; v i d e o 23h d e s c r i p t o r <00007h, o f f s e t LDT0,, b> ; LDT0 28h d e s c r i p t o r <0002Bh, o f f s e t TSS0,, b> ; TSS0 30h OSP Lecture 1, Booting 10/30

11 Outline Hardware Processor Memory I/O subsystems Boot Process Keywords Resources Questions OSP Lecture 1, Booting 11/30

12 PIC OSP Lecture 1, Booting 12/30

13 cascade The original 8086 had only one PIC Needed more devices - cascaded a second PIC OSP Lecture 1, Booting 13/30

14 Interrupts - real mode Exception handlers 02 - NMI Exception handlers 08-0F - IRQ0 - IRQ7 10-6F - Software interrupts IRQ8 - IRQ15 78-FF - Software interrupts OSP Lecture 1, Booting 14/30

15 Interrupts - protected mode IDT - Interrupt Descriptor Table OSP Lecture 1, Booting 15/30

16 init 8259 i n i t proc near mov al, 1 1 h ; ICW1 : edge, c a l l a d d r e s s i n t e r v a l 8, cascaded, sed ICW4 out 20h, a l out 0A0h, a l mov al, 2 0 h ; ICW2 : f i r s t 8 IRQs s t a r t a t 20h a f t e r t h e r e s e r v e d e x c e p t i o n s out 21h, a l mov al, 28 h ; ICW2 : next 8 IRQS are immediately a f t e r out 0A1h, a l mov al, 4 ; ICW3 : IRQ2 i s c o n n e c t e d to a s l a v e out 21h, a l mov al, 2 out 0A1h, a l ; ICW3 : Slave ID 2 mov al, 1 ; ICW4 : 8086 Mode out 021h, a l out 0A1h, a l mov al, 0 FFh out 0A1h, a l ; OCW1: Mask a l l i n t s on PIC2 mov al, 0 FCh ; OCW1: mask a l l i n t s but timer and keyboard on PIC1 out 021h, a l r e t endp OSP Lecture 1, Booting 16/30

17 Timer OSP Lecture 1, Booting 17/30

18 Timer OSP Lecture 1, Booting 18/30

19 Timer i n i t proc near mov al, 36 h ; LSB then MSB, mode 011 out 43h, a l mov ax, ; c l o c k f r e q i s H z, 1/3 NTSC c o l o r s u b c a r r i e r f r e q jmp $ + 2 jmp $ + 2 out 40h, a l jmp $ + 2 jmp $ + 2 mov al, ah out 40h, a l r e t s endp OSP Lecture 1, Booting 19/30

20 Scheduler c l k proc f a r ; Task s c h e d u l e r (100 Hz ) push ax push bx push ds mov ax, 1 0 h mov ds, ax add cmp j n e mov jmp task, 18 h task, 88 h j m p f a r task, 40 h j m p f a r jmpfar : mov bx, task and GDT[ bx ]. r i g h t s, 0 FDh mov out pop pop pop al, 2 0 h 20h, a l ds bx ax t a s k db 0EAh ; jmp TSSi ( i = 1, 2, 3) dw 0 dw 40h i r e t OSP Lecture 1, Booting 20/30

21 Outline Hardware Processor Memory I/O subsystems Boot Process Keywords Resources Questions OSP Lecture 1, Booting 21/30

22 Boot process POST Search boot device: floppy, HD, etc Load MBR at 0000:7C00 Jump at that address Usually the code in the MBR looks for the active partition, loads its first sector also at 7C00 and jumps there We will instead load sectors from the disk and jump OSP Lecture 1, Booting 22/30

23 Boot sequence OSP Lecture 1, Booting 23/30

24 Bootstrap s t a r t : c l i r e a l s t a r t : xor ax, ax mov ss, ax mov sp, 7 C00h mov s i, sp mov ds, ax mov es, ax s t i c l d mov di, h mov cx, h repnz movsw db 0EAh dw 61Dh, 0 ; jmp f a r ptr 0000:061D OSP Lecture 1, Booting 24/30

25 Outline Hardware Processor Memory I/O subsystems Boot Process Keywords Resources Questions OSP Lecture 1, Booting 25/30

26 Keywords processor memory i/o subsystems boot process bootstrap 0x7c00 interrupts timer OSP Lecture 1, Booting 26/30

27 Outline Hardware Processor Memory I/O subsystems Boot Process Keywords Resources Questions OSP Lecture 1, Booting 27/30

28 Resources Use the source, Luke! OSP Lecture 1, Booting 28/30

29 Outline Hardware Processor Memory I/O subsystems Boot Process Keywords Resources Questions OSP Lecture 1, Booting 29/30

30 Questions? OSP Lecture 1, Booting 30/30

EEE Lecture 1 -1-

EEE Lecture 1 -1- EEE3410 - Lecture 1-1- 1. PC -> Address Move content of the Program Counter to Address Bus 2. Mem(Add) -> ID Move the Data at Location Add from main memory to Instruction Decoder (ID) 3. Acc s -> ALU Move