Carlos Fenollosa
9 years ago
parent
a833ee8f9e
commit
69a7c1c2a6
@ -0,0 +1,46 @@
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C_SOURCES = $(wildcard kernel/*.c drivers/*.c cpu/*.c)
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HEADERS = $(wildcard kernel/*.h drivers/*.h cpu/*.h)
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# Nice syntax for file extension replacement
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OBJ = ${C_SOURCES:.c=.o cpu/interrupt.o}
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# Change this if your cross-compiler is somewhere else
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CC = /usr/local/i386elfgcc/bin/i386-elf-gcc
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GDB = /usr/local/i386elfgcc/bin/i386-elf-gdb
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# -g: Use debugging symbols in gcc
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CFLAGS = -g
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# First rule is run by default
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os-image.bin: boot/bootsect.bin kernel.bin
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cat $^ > os-image.bin
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# '--oformat binary' deletes all symbols as a collateral, so we don't need
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# to 'strip' them manually on this case
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kernel.bin: boot/kernel_entry.o ${OBJ}
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i386-elf-ld -o $@ -Ttext 0x1000 $^ --oformat binary
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# Used for debugging purposes
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kernel.elf: boot/kernel_entry.o ${OBJ}
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i386-elf-ld -o $@ -Ttext 0x1000 $^
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run: os-image.bin
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qemu-system-i386 -fda os-image.bin
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# Open the connection to qemu and load our kernel-object file with symbols
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debug: os-image.bin kernel.elf
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qemu-system-i386 -s -fda os-image.bin -d guest_errors,int &
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${GDB} -ex "target remote localhost:1234" -ex "symbol-file kernel.elf"
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# Generic rules for wildcards
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# To make an object, always compile from its .c
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%.o: %.c ${HEADERS}
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${CC} ${CFLAGS} -ffreestanding -c $< -o $@
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%.o: %.asm
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nasm $< -f elf -o $@
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%.bin: %.asm
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nasm $< -f bin -o $@
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clean:
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rm -rf *.bin *.dis *.o os-image.bin *.elf
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rm -rf kernel/*.o boot/*.bin drivers/*.o boot/*.o cpu/*.o
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@ -0,0 +1,80 @@
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*Concepts you may want to Google beforehand: C types and structs, include guards, type attributes: packed, extern, volatile, exceptions*
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**Goal: Set up the Interrupt Descriptor Table to handle CPU interrupts**
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This lesson and the following ones have been heavily inspired
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by [JamesM's tutorial](http://www.jamesmolloy.co.uk/tutorial_html/index.html)
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Data types
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----------
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First, we will define some special data types in `cpu/types.h`,
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which will help us uncouple data structures for raw bytes from chars and ints.
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It has been carefully placed on the `cpu/` folder, where we will
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put machine-dependent code from now on. Yes, the boot code
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is specifically x86 and is still on `boot/`, but let's leave
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that alone for now.
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Some of the already existing files have been changed to use
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the new `u8`, `u16` and `u32` data types.
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From now on, our C header files will also have include guards.
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Interrupts
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----------
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Interrupts are one of the main things that a kernel needs to
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handle. We will implement it now, as soon as possible, to be able
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to receive keyboard input in future lessons.
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Another examples of interrupts are: divisions by zero, out of bounds,
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invalid opcodes, page faults, etc.
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Interrupts are handled on a vector, with entries which are
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similar to those of the GDT (lesson 9). However, instead of
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programming the IDT in assembly, we'll do it in C.
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`cpu/idt.h` defines how an idt entry is stored `idt_gate` (there need to be
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256 of them, even if null, or the CPU may panic) and the actual
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idt structure that the BIOS will load, `idt_register` which is
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just a memory address and a size, similar to the GDT register.
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Finally, we define a couple variables to access those data structures
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from assembler code.
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`cpu/idt.c` just fills in every struct with a handler.
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As you can see, it is a matter
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of setting the struct values and calling the `lidt` assembler command.
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ISRs
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----
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The Interrupt Service Routines run every time the CPU detects an
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interrupt, which is usually fatal.
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We will write just enough code to handle them, print an error message,
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and halt the CPU.
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On `cpu/isr.h` we define 32 of them, manually. They are declared as
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`extern` because they will be implemented in assembler, in `cpu/interrupt.asm`
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Before jumping to the assembler code, check out `cpu/isr.c`. As you can see,
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we define a function to install all isrs at once and load the IDT, a list of error
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messages, and the high level handler, which kprints some information. You
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can customize `isr_handler` to print/do whatever you want.
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Now to the low level which glues every `idt_gate` with its low-level and
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high-level handler. Open `cpu/interrupt.asm`. Here we define a common
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low level ISR code, which basically saves/restores the state and calls
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the C code, and then the actual ISR assembler functions which are referenced
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on `cpu/isr.h`
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Note how the `registers_t` struct is a representation of all the registers
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we pushed in `interrupt.asm`
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That's basically it. Now we need to reference `cpu/interrupt.asm` from our
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Makefile, and make the kernel install the ISRs and launch one of them.
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Notice how the CPU doesn't halt even though it would be good practice
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to do it after some interrupts.
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@ -0,0 +1,26 @@
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[bits 32] ; using 32-bit protected mode
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; this is how constants are defined
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VIDEO_MEMORY equ 0xb8000
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WHITE_OB_BLACK equ 0x0f ; the color byte for each character
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print_string_pm:
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pusha
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mov edx, VIDEO_MEMORY
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print_string_pm_loop:
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mov al, [ebx] ; [ebx] is the address of our character
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mov ah, WHITE_OB_BLACK
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cmp al, 0 ; check if end of string
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je print_string_pm_done
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mov [edx], ax ; store character + attribute in video memory
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add ebx, 1 ; next char
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add edx, 2 ; next video memory position
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jmp print_string_pm_loop
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print_string_pm_done:
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popa
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ret
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@ -0,0 +1,52 @@
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; Identical to lesson 13's boot sector, but the %included files have new paths
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[org 0x7c00]
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KERNEL_OFFSET equ 0x1000 ; The same one we used when linking the kernel
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mov [BOOT_DRIVE], dl ; Remember that the BIOS sets us the boot drive in 'dl' on boot
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mov bp, 0x9000
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mov sp, bp
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mov bx, MSG_REAL_MODE
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call print
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call print_nl
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call load_kernel ; read the kernel from disk
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call switch_to_pm ; disable interrupts, load GDT, etc. Finally jumps to 'BEGIN_PM'
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jmp $ ; Never executed
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%include "boot/print.asm"
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%include "boot/print_hex.asm"
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%include "boot/disk.asm"
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%include "boot/gdt.asm"
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%include "boot/32bit_print.asm"
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%include "boot/switch_pm.asm"
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[bits 16]
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load_kernel:
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mov bx, MSG_LOAD_KERNEL
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call print
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call print_nl
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mov bx, KERNEL_OFFSET ; Read from disk and store in 0x1000
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mov dh, 31 ; Our future kernel will be larger, make this big
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mov dl, [BOOT_DRIVE]
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call disk_load
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ret
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[bits 32]
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BEGIN_PM:
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mov ebx, MSG_PROT_MODE
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call print_string_pm
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call KERNEL_OFFSET ; Give control to the kernel
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jmp $ ; Stay here when the kernel returns control to us (if ever)
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BOOT_DRIVE db 0 ; It is a good idea to store it in memory because 'dl' may get overwritten
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MSG_REAL_MODE db "Started in 16-bit Real Mode", 0
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MSG_PROT_MODE db "Landed in 32-bit Protected Mode", 0
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MSG_LOAD_KERNEL db "Loading kernel into memory", 0
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MSG_RETURNED_KERNEL db "Returned from kernel. Error?", 0
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; padding
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times 510 - ($-$$) db 0
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dw 0xaa55
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@ -0,0 +1,46 @@
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; load 'dh' sectors from drive 'dl' into ES:BX
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disk_load:
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pusha
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; reading from disk requires setting specific values in all registers
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; so we will overwrite our input parameters from 'dx'. Let's save it
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; to the stack for later use.
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push dx
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mov ah, 0x02 ; ah <- int 0x13 function. 0x02 = 'read'
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mov al, dh ; al <- number of sectors to read (0x01 .. 0x80)
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mov cl, 0x02 ; cl <- sector (0x01 .. 0x11)
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; 0x01 is our boot sector, 0x02 is the first 'available' sector
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mov ch, 0x00 ; ch <- cylinder (0x0 .. 0x3FF, upper 2 bits in 'cl')
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; dl <- drive number. Our caller sets it as a parameter and gets it from BIOS
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; (0 = floppy, 1 = floppy2, 0x80 = hdd, 0x81 = hdd2)
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mov dh, 0x00 ; dh <- head number (0x0 .. 0xF)
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; [es:bx] <- pointer to buffer where the data will be stored
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; caller sets it up for us, and it is actually the standard location for int 13h
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int 0x13 ; BIOS interrupt
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jc disk_error ; if error (stored in the carry bit)
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pop dx
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cmp al, dh ; BIOS also sets 'al' to the # of sectors read. Compare it.
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jne sectors_error
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popa
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ret
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disk_error:
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mov bx, DISK_ERROR
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call print
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call print_nl
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mov dh, ah ; ah = error code, dl = disk drive that dropped the error
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call print_hex ; check out the code at http://stanislavs.org/helppc/int_13-1.html
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jmp disk_loop
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sectors_error:
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mov bx, SECTORS_ERROR
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call print
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disk_loop:
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jmp $
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DISK_ERROR: db "Disk read error", 0
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SECTORS_ERROR: db "Incorrect number of sectors read", 0
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@ -0,0 +1,35 @@
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gdt_start: ; don't remove the labels, they're needed to compute sizes and jumps
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; the GDT starts with a null 8-byte
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dd 0x0 ; 4 byte
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dd 0x0 ; 4 byte
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; GDT for code segment. base = 0x00000000, length = 0xfffff
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; for flags, refer to os-dev.pdf document, page 36
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gdt_code:
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dw 0xffff ; segment length, bits 0-15
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dw 0x0 ; segment base, bits 0-15
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db 0x0 ; segment base, bits 16-23
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db 10011010b ; flags (8 bits)
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db 11001111b ; flags (4 bits) + segment length, bits 16-19
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db 0x0 ; segment base, bits 24-31
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; GDT for data segment. base and length identical to code segment
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; some flags changed, again, refer to os-dev.pdf
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gdt_data:
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dw 0xffff
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dw 0x0
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db 0x0
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db 10010010b
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db 11001111b
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db 0x0
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gdt_end:
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; GDT descriptor
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gdt_descriptor:
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dw gdt_end - gdt_start - 1 ; size (16 bit), always one less of its true size
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dd gdt_start ; address (32 bit)
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; define some constants for later use
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CODE_SEG equ gdt_code - gdt_start
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DATA_SEG equ gdt_data - gdt_start
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@ -0,0 +1,4 @@
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[bits 32]
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[extern main] ; Define calling point. Must have same name as kernel.c 'main' function
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call main ; Calls the C function. The linker will know where it is placed in memory
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jmp $
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@ -0,0 +1,37 @@
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print:
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pusha
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; keep this in mind:
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; while (string[i] != 0) { print string[i]; i++ }
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; the comparison for string end (null byte)
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start:
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mov al, [bx] ; 'bx' is the base address for the string
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cmp al, 0
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je done
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; the part where we print with the BIOS help
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mov ah, 0x0e
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int 0x10 ; 'al' already contains the char
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; increment pointer and do next loop
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add bx, 1
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jmp start
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done:
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popa
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ret
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print_nl:
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pusha
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mov ah, 0x0e
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mov al, 0x0a ; newline char
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int 0x10
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mov al, 0x0d ; carriage return
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int 0x10
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popa
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ret
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@ -0,0 +1,46 @@
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; receiving the data in 'dx'
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; For the examples we'll assume that we're called with dx=0x1234
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print_hex:
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pusha
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mov cx, 0 ; our index variable
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; Strategy: get the last char of 'dx', then convert to ASCII
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; Numeric ASCII values: '0' (ASCII 0x30) to '9' (0x39), so just add 0x30 to byte N.
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; For alphabetic characters A-F: 'A' (ASCII 0x41) to 'F' (0x46) we'll add 0x40
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; Then, move the ASCII byte to the correct position on the resulting string
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hex_loop:
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cmp cx, 4 ; loop 4 times
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je end
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; 1. convert last char of 'dx' to ascii
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mov ax, dx ; we will use 'ax' as our working register
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and ax, 0x000f ; 0x1234 -> 0x0004 by masking first three to zeros
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add al, 0x30 ; add 0x30 to N to convert it to ASCII "N"
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cmp al, 0x39 ; if > 9, add extra 8 to represent 'A' to 'F'
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jle step2
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add al, 7 ; 'A' is ASCII 65 instead of 58, so 65-58=7
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step2:
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; 2. get the correct position of the string to place our ASCII char
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; bx <- base address + string length - index of char
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mov bx, HEX_OUT + 5 ; base + length
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sub bx, cx ; our index variable
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mov [bx], al ; copy the ASCII char on 'al' to the position pointed by 'bx'
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ror dx, 4 ; 0x1234 -> 0x4123 -> 0x3412 -> 0x2341 -> 0x1234
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; increment index and loop
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add cx, 1
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jmp hex_loop
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end:
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; prepare the parameter and call the function
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; remember that print receives parameters in 'bx'
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mov bx, HEX_OUT
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call print
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popa
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ret
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HEX_OUT:
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db '0x0000',0 ; reserve memory for our new string
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@ -0,0 +1,22 @@
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[bits 16]
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switch_to_pm:
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cli ; 1. disable interrupts
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lgdt [gdt_descriptor] ; 2. load the GDT descriptor
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mov eax, cr0
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or eax, 0x1 ; 3. set 32-bit mode bit in cr0
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mov cr0, eax
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jmp CODE_SEG:init_pm ; 4. far jump by using a different segment
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[bits 32]
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init_pm: ; we are now using 32-bit instructions
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mov ax, DATA_SEG ; 5. update the segment registers
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mov ds, ax
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mov ss, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ebp, 0x90000 ; 6. update the stack right at the top of the free space
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mov esp, ebp
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call BEGIN_PM ; 7. Call a well-known label with useful code
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@ -0,0 +1,17 @@
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#include "idt.h"
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#include "../kernel/util.h"
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void set_idt_gate(int n, u32 handler) {
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idt[n].low_offset = low_16(handler);
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idt[n].sel = KERNEL_CS;
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idt[n].always0 = 0;
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idt[n].flags = 0x8E;
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idt[n].high_offset = high_16(handler);
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}
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void set_idt() {
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idt_reg.base = (u32) &idt;
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idt_reg.limit = IDT_ENTRIES * sizeof(idt_gate_t) - 1;
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/* Don't make the mistake of loading &idt -- always load &idt_reg */
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__asm__ __volatile__("lidtl (%0)" : : "r" (&idt_reg));
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}
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@ -0,0 +1,39 @@
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#ifndef IDT_H
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#define IDT_H
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#include "types.h"
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/* Segment selectors */
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#define KERNEL_CS 0x08
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/* How every interrupt gate (handler) is defined */
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typedef struct {
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u16 low_offset; /* Lower 16 bits of handler function address */
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u16 sel; /* Kernel segment selector */
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u8 always0;
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/* First byte
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* Bit 7: "Interrupt is present"
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* Bits 6-5: Privilege level of caller (0=kernel..3=user)
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* Bit 4: Set to 0 for interrupt gates
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* Bits 3-0: bits 1110 = decimal 14 = "32 bit interrupt gate" */
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u8 flags;
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u16 high_offset; /* Higher 16 bits of handler function address */
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} __attribute__((packed)) idt_gate_t ;
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/* A pointer to the array of interrupt handlers.
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* Assembly instruction 'lidt' will read it */
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typedef struct {
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u16 limit;
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u32 base;
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} __attribute__((packed)) idt_register_t;
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#define IDT_ENTRIES 256
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idt_gate_t idt[IDT_ENTRIES];
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idt_register_t idt_reg;
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/* Functions implemented in idt.c */
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void set_idt_gate(int n, u32 handler);
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void set_idt();
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#endif
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@ -0,0 +1,289 @@
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; Defined in isr.c
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[extern isr_handler]
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; Common ISR code
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isr_common_stub:
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; 1. Save CPU state
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pusha ; Pushes edi,esi,ebp,esp,ebx,edx,ecx,eax
|
||||
mov ax, ds ; Lower 16-bits of eax = ds.
|
||||
push eax ; save the data segment descriptor
|
||||
mov ax, 0x10 ; kernel data segment descriptor
|
||||
mov ds, ax
|
||||
mov es, ax
|
||||
mov fs, ax
|
||||
mov gs, ax
|
||||
|
||||
; 2. Call C handler
|
||||
call isr_handler
|
||||
|
||||
; 3. Restore state
|
||||
pop eax
|
||||
mov ds, ax
|
||||
mov es, ax
|
||||
mov fs, ax
|
||||
mov gs, ax
|
||||
popa
|
||||
add esp, 8 ; Cleans up the pushed error code and pushed ISR number
|
||||
sti
|
||||
iret ; pops 5 things at once: CS, EIP, EFLAGS, SS, and ESP
|
||||
|
||||
; We don't get information about which interrupt was caller
|
||||
; when the handler is run, so we will need to have a different handler
|
||||
; for every interrupt.
|
||||
; Furthermore, some interrupts push an error code onto the stack but others
|
||||
; don't, so we will push a dummy error code for those which don't, so that
|
||||
; we have a consistent stack for all of them.
|
||||
|
||||
; First make the ISRs global
|
||||
global isr0
|
||||
global isr1
|
||||
global isr2
|
||||
global isr3
|
||||
global isr4
|
||||
global isr5
|
||||
global isr6
|
||||
global isr7
|
||||
global isr8
|
||||
global isr9
|
||||
global isr10
|
||||
global isr11
|
||||
global isr12
|
||||
global isr13
|
||||
global isr14
|
||||
global isr15
|
||||
global isr16
|
||||
global isr17
|
||||
global isr18
|
||||
global isr19
|
||||
global isr20
|
||||
global isr21
|
||||
global isr22
|
||||
global isr23
|
||||
global isr24
|
||||
global isr25
|
||||
global isr26
|
||||
global isr27
|
||||
global isr28
|
||||
global isr29
|
||||
global isr30
|
||||
global isr31
|
||||
|
||||
; 0: Divide By Zero Exception
|
||||
isr0:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 0
|
||||
jmp isr_common_stub
|
||||
|
||||
; 1: Debug Exception
|
||||
isr1:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 1
|
||||
jmp isr_common_stub
|
||||
|
||||
; 2: Non Maskable Interrupt Exception
|
||||
isr2:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 2
|
||||
jmp isr_common_stub
|
||||
|
||||
; 3: Int 3 Exception
|
||||
isr3:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 3
|
||||
jmp isr_common_stub
|
||||
|
||||
; 4: INTO Exception
|
||||
isr4:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 4
|
||||
jmp isr_common_stub
|
||||
|
||||
; 5: Out of Bounds Exception
|
||||
isr5:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 5
|
||||
jmp isr_common_stub
|
||||
|
||||
; 6: Invalid Opcode Exception
|
||||
isr6:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 6
|
||||
jmp isr_common_stub
|
||||
|
||||
; 7: Coprocessor Not Available Exception
|
||||
isr7:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 7
|
||||
jmp isr_common_stub
|
||||
|
||||
; 8: Double Fault Exception (With Error Code!)
|
||||
isr8:
|
||||
cli
|
||||
push byte 8
|
||||
jmp isr_common_stub
|
||||
|
||||
; 9: Coprocessor Segment Overrun Exception
|
||||
isr9:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 9
|
||||
jmp isr_common_stub
|
||||
|
||||
; 10: Bad TSS Exception (With Error Code!)
|
||||
isr10:
|
||||
cli
|
||||
push byte 10
|
||||
jmp isr_common_stub
|
||||
|
||||
; 11: Segment Not Present Exception (With Error Code!)
|
||||
isr11:
|
||||
cli
|
||||
push byte 11
|
||||
jmp isr_common_stub
|
||||
|
||||
; 12: Stack Fault Exception (With Error Code!)
|
||||
isr12:
|
||||
cli
|
||||
push byte 12
|
||||
jmp isr_common_stub
|
||||
|
||||
; 13: General Protection Fault Exception (With Error Code!)
|
||||
isr13:
|
||||
cli
|
||||
push byte 13
|
||||
jmp isr_common_stub
|
||||
|
||||
; 14: Page Fault Exception (With Error Code!)
|
||||
isr14:
|
||||
cli
|
||||
push byte 14
|
||||
jmp isr_common_stub
|
||||
|
||||
; 15: Reserved Exception
|
||||
isr15:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 15
|
||||
jmp isr_common_stub
|
||||
|
||||
; 16: Floating Point Exception
|
||||
isr16:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 16
|
||||
jmp isr_common_stub
|
||||
|
||||
; 17: Alignment Check Exception
|
||||
isr17:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 17
|
||||
jmp isr_common_stub
|
||||
|
||||
; 18: Machine Check Exception
|
||||
isr18:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 18
|
||||
jmp isr_common_stub
|
||||
|
||||
; 19: Reserved
|
||||
isr19:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 19
|
||||
jmp isr_common_stub
|
||||
|
||||
; 20: Reserved
|
||||
isr20:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 20
|
||||
jmp isr_common_stub
|
||||
|
||||
; 21: Reserved
|
||||
isr21:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 21
|
||||
jmp isr_common_stub
|
||||
|
||||
; 22: Reserved
|
||||
isr22:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 22
|
||||
jmp isr_common_stub
|
||||
|
||||
; 23: Reserved
|
||||
isr23:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 23
|
||||
jmp isr_common_stub
|
||||
|
||||
; 24: Reserved
|
||||
isr24:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 24
|
||||
jmp isr_common_stub
|
||||
|
||||
; 25: Reserved
|
||||
isr25:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 25
|
||||
jmp isr_common_stub
|
||||
|
||||
; 26: Reserved
|
||||
isr26:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 26
|
||||
jmp isr_common_stub
|
||||
|
||||
; 27: Reserved
|
||||
isr27:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 27
|
||||
jmp isr_common_stub
|
||||
|
||||
; 28: Reserved
|
||||
isr28:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 28
|
||||
jmp isr_common_stub
|
||||
|
||||
; 29: Reserved
|
||||
isr29:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 29
|
||||
jmp isr_common_stub
|
||||
|
||||
; 30: Reserved
|
||||
isr30:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 30
|
||||
jmp isr_common_stub
|
||||
|
||||
; 31: Reserved
|
||||
isr31:
|
||||
cli
|
||||
push byte 0
|
||||
push byte 31
|
||||
jmp isr_common_stub
|
||||
|
||||
|
||||
@ -0,0 +1,92 @@
|
||||
#include "isr.h"
|
||||
#include "idt.h"
|
||||
#include "../drivers/screen.h"
|
||||
#include "../kernel/util.h"
|
||||
|
||||
/* Can't do this with a loop because we need the address
|
||||
* of the function names */
|
||||
void isr_install() {
|
||||
set_idt_gate(0, (u32)isr0);
|
||||
set_idt_gate(1, (u32)isr1);
|
||||
set_idt_gate(2, (u32)isr2);
|
||||
set_idt_gate(3, (u32)isr3);
|
||||
set_idt_gate(4, (u32)isr4);
|
||||
set_idt_gate(5, (u32)isr5);
|
||||
set_idt_gate(6, (u32)isr6);
|
||||
set_idt_gate(7, (u32)isr7);
|
||||
set_idt_gate(8, (u32)isr8);
|
||||
set_idt_gate(9, (u32)isr9);
|
||||
set_idt_gate(10, (u32)isr10);
|
||||
set_idt_gate(11, (u32)isr11);
|
||||
set_idt_gate(12, (u32)isr12);
|
||||
set_idt_gate(13, (u32)isr13);
|
||||
set_idt_gate(14, (u32)isr14);
|
||||
set_idt_gate(15, (u32)isr15);
|
||||
set_idt_gate(16, (u32)isr16);
|
||||
set_idt_gate(17, (u32)isr17);
|
||||
set_idt_gate(18, (u32)isr18);
|
||||
set_idt_gate(19, (u32)isr19);
|
||||
set_idt_gate(20, (u32)isr20);
|
||||
set_idt_gate(21, (u32)isr21);
|
||||
set_idt_gate(22, (u32)isr22);
|
||||
set_idt_gate(23, (u32)isr23);
|
||||
set_idt_gate(24, (u32)isr24);
|
||||
set_idt_gate(25, (u32)isr25);
|
||||
set_idt_gate(26, (u32)isr26);
|
||||
set_idt_gate(27, (u32)isr27);
|
||||
set_idt_gate(28, (u32)isr28);
|
||||
set_idt_gate(29, (u32)isr29);
|
||||
set_idt_gate(30, (u32)isr30);
|
||||
set_idt_gate(31, (u32)isr31);
|
||||
|
||||
set_idt(); // Load with ASM
|
||||
}
|
||||
|
||||
/* To print the message which defines every exception */
|
||||
char *exception_messages[] = {
|
||||
"Division By Zero",
|
||||
"Debug",
|
||||
"Non Maskable Interrupt",
|
||||
"Breakpoint",
|
||||
"Into Detected Overflow",
|
||||
"Out of Bounds",
|
||||
"Invalid Opcode",
|
||||
"No Coprocessor",
|
||||
|
||||
"Double Fault",
|
||||
"Coprocessor Segment Overrun",
|
||||
"Bad TSS",
|
||||
"Segment Not Present",
|
||||
"Stack Fault",
|
||||
"General Protection Fault",
|
||||
"Page Fault",
|
||||
"Unknown Interrupt",
|
||||
|
||||
"Coprocessor Fault",
|
||||
"Alignment Check",
|
||||
"Machine Check",
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
"Reserved",
|
||||
"Reserved"
|
||||
};
|
||||
|
||||
void isr_handler(registers_t r) {
|
||||
kprint("received interrupt: ");
|
||||
char s[3];
|
||||
int_to_ascii(r.int_no, s);
|
||||
kprint(s);
|
||||
kprint("\n");
|
||||
kprint(exception_messages[r.int_no]);
|
||||
kprint("\n");
|
||||
}
|
||||
@ -0,0 +1,51 @@
|
||||
#ifndef ISR_H
|
||||
#define ISR_H
|
||||
|
||||
#include "types.h"
|
||||
|
||||
/* ISRs reserved for CPU exceptions */
|
||||
extern void isr0();
|
||||
extern void isr1();
|
||||
extern void isr2();
|
||||
extern void isr3();
|
||||
extern void isr4();
|
||||
extern void isr5();
|
||||
extern void isr6();
|
||||
extern void isr7();
|
||||
extern void isr8();
|
||||
extern void isr9();
|
||||
extern void isr10();
|
||||
extern void isr11();
|
||||
extern void isr12();
|
||||
extern void isr13();
|
||||
extern void isr14();
|
||||
extern void isr15();
|
||||
extern void isr16();
|
||||
extern void isr17();
|
||||
extern void isr18();
|
||||
extern void isr19();
|
||||
extern void isr20();
|
||||
extern void isr21();
|
||||
extern void isr22();
|
||||
extern void isr23();
|
||||
extern void isr24();
|
||||
extern void isr25();
|
||||
extern void isr26();
|
||||
extern void isr27();
|
||||
extern void isr28();
|
||||
extern void isr29();
|
||||
extern void isr30();
|
||||
extern void isr31();
|
||||
|
||||
/* Struct which aggregates many registers */
|
||||
typedef struct {
|
||||
u32 ds; /* Data segment selector */
|
||||
u32 edi, esi, ebp, esp, ebx, edx, ecx, eax; /* Pushed by pusha. */
|
||||
u32 int_no, err_code; /* Interrupt number and error code (if applicable) */
|
||||
u32 eip, cs, eflags, useresp, ss; /* Pushed by the processor automatically */
|
||||
} registers_t;
|
||||
|
||||
void isr_install();
|
||||
void isr_handler(registers_t r);
|
||||
|
||||
#endif
|
||||
@ -0,0 +1,16 @@
|
||||
#ifndef TYPES_H
|
||||
#define TYPES_H
|
||||
|
||||
/* Instead of using 'chars' to allocate non-character bytes,
|
||||
* we will use these new type with no semantic meaning */
|
||||
typedef unsigned int u32;
|
||||
typedef int s32;
|
||||
typedef unsigned short u16;
|
||||
typedef short s16;
|
||||
typedef unsigned char u8;
|
||||
typedef char s8;
|
||||
|
||||
#define low_16(address) (u16)((address) & 0xFFFF)
|
||||
#define high_16(address) (u16)(((address) >> 16) & 0xFFFF)
|
||||
|
||||
#endif
|
||||
@ -0,0 +1,37 @@
|
||||
#include "ports.h"
|
||||
|
||||
/**
|
||||
* Read a byte from the specified port
|
||||
*/
|
||||
u8 port_byte_in (u16 port) {
|
||||
u8 result;
|
||||
/* Inline assembler syntax
|
||||
* !! Notice how the source and destination registers are switched from NASM !!
|
||||
*
|
||||
* '"=a" (result)'; set '=' the C variable '(result)' to the value of register e'a'x
|
||||
* '"d" (port)': map the C variable '(port)' into e'd'x register
|
||||
*
|
||||
* Inputs and outputs are separated by colons
|
||||
*/
|
||||
__asm__("in %%dx, %%al" : "=a" (result) : "d" (port));
|
||||
return result;
|
||||
}
|
||||
|
||||
void port_byte_out (u16 port, u8 data) {
|
||||
/* Notice how here both registers are mapped to C variables and
|
||||
* nothing is returned, thus, no equals '=' in the asm syntax
|
||||
* However we see a comma since there are two variables in the input area
|
||||
* and none in the 'return' area
|
||||
*/
|
||||
__asm__ __volatile__("out %%al, %%dx" : : "a" (data), "d" (port));
|
||||
}
|
||||
|
||||
u16 port_word_in (u16 port) {
|
||||
u16 result;
|
||||
__asm__("in %%dx, %%ax" : "=a" (result) : "d" (port));
|
||||
return result;
|
||||
}
|
||||
|
||||
void port_word_out (u16 port, u16 data) {
|
||||
__asm__ __volatile__("out %%ax, %%dx" : : "a" (data), "d" (port));
|
||||
}
|
||||
@ -0,0 +1,11 @@
|
||||
#ifndef PORTS_H
|
||||
#define PORTS_H
|
||||
|
||||
#include "../cpu/types.h"
|
||||
|
||||
unsigned char port_byte_in (u16 port);
|
||||
void port_byte_out (u16 port, u8 data);
|
||||
unsigned short port_word_in (u16 port);
|
||||
void port_word_out (u16 port, u16 data);
|
||||
|
||||
#endif
|
||||
@ -0,0 +1,139 @@
|
||||
#include "screen.h"
|
||||
#include "ports.h"
|
||||
#include "../kernel/util.h"
|
||||
|
||||
/* Declaration of private functions */
|
||||
int get_cursor_offset();
|
||||
void set_cursor_offset(int offset);
|
||||
int print_char(char c, int col, int row, char attr);
|
||||
int get_offset(int col, int row);
|
||||
int get_offset_row(int offset);
|
||||
int get_offset_col(int offset);
|
||||
|
||||
/**********************************************************
|
||||
* Public Kernel API functions *
|
||||
**********************************************************/
|
||||
|
||||
/**
|
||||
* Print a message on the specified location
|
||||
* If col, row, are negative, we will use the current offset
|
||||
*/
|
||||
void kprint_at(char *message, int col, int row) {
|
||||
/* Set cursor if col/row are negative */
|
||||
int offset;
|
||||
if (col >= 0 && row >= 0)
|
||||
offset = get_offset(col, row);
|
||||
else {
|
||||
offset = get_cursor_offset();
|
||||
row = get_offset_row(offset);
|
||||
col = get_offset_col(offset);
|
||||
}
|
||||
|
||||
/* Loop through message and print it */
|
||||
int i = 0;
|
||||
while (message[i] != 0) {
|
||||
offset = print_char(message[i++], col, row, WHITE_ON_BLACK);
|
||||
/* Compute row/col for next iteration */
|
||||
row = get_offset_row(offset);
|
||||
col = get_offset_col(offset);
|
||||
}
|
||||
}
|
||||
|
||||
void kprint(char *message) {
|
||||
kprint_at(message, -1, -1);
|
||||
}
|
||||
|
||||
|
||||
/**********************************************************
|
||||
* Private kernel functions *
|
||||
**********************************************************/
|
||||
|
||||
|
||||
/**
|
||||
* Innermost print function for our kernel, directly accesses the video memory
|
||||
*
|
||||
* If 'col' and 'row' are negative, we will print at current cursor location
|
||||
* If 'attr' is zero it will use 'white on black' as default
|
||||
* Returns the offset of the next character
|
||||
* Sets the video cursor to the returned offset
|
||||
*/
|
||||
int print_char(char c, int col, int row, char attr) {
|
||||
unsigned char *vidmem = (unsigned char*) VIDEO_ADDRESS;
|
||||
if (!attr) attr = WHITE_ON_BLACK;
|
||||
|
||||
/* Error control: print a red 'E' if the coords aren't right */
|
||||
if (col >= MAX_COLS || row >= MAX_ROWS) {
|
||||
vidmem[2*(MAX_COLS)*(MAX_ROWS)-2] = 'E';
|
||||
vidmem[2*(MAX_COLS)*(MAX_ROWS)-1] = RED_ON_WHITE;
|
||||
return get_offset(col, row);
|
||||
}
|
||||
|
||||
int offset;
|
||||
if (col >= 0 && row >= 0) offset = get_offset(col, row);
|
||||
else offset = get_cursor_offset();
|
||||
|
||||
if (c == '\n') {
|
||||
row = get_offset_row(offset);
|
||||
offset = get_offset(0, row+1);
|
||||
} else {
|
||||
vidmem[offset] = c;
|
||||
vidmem[offset+1] = attr;
|
||||
offset += 2;
|
||||
}
|
||||
|
||||
/* Check if the offset is over screen size and scroll */
|
||||
if (offset >= MAX_ROWS * MAX_COLS * 2) {
|
||||
int i;
|
||||
for (i = 1; i < MAX_ROWS; i++)
|
||||
memory_copy(get_offset(0, i) + VIDEO_ADDRESS,
|
||||
get_offset(0, i-1) + VIDEO_ADDRESS,
|
||||
MAX_COLS * 2);
|
||||
|
||||
/* Blank last line */
|
||||
char *last_line = get_offset(0, MAX_ROWS-1) + VIDEO_ADDRESS;
|
||||
for (i = 0; i < MAX_COLS * 2; i++) last_line[i] = 0;
|
||||
|
||||
offset -= 2 * MAX_COLS;
|
||||
}
|
||||
|
||||
set_cursor_offset(offset);
|
||||
return offset;
|
||||
}
|
||||
|
||||
int get_cursor_offset() {
|
||||
/* Use the VGA ports to get the current cursor position
|
||||
* 1. Ask for high byte of the cursor offset (data 14)
|
||||
* 2. Ask for low byte (data 15)
|
||||
*/
|
||||
port_byte_out(REG_SCREEN_CTRL, 14);
|
||||
int offset = port_byte_in(REG_SCREEN_DATA) << 8; /* High byte: << 8 */
|
||||
port_byte_out(REG_SCREEN_CTRL, 15);
|
||||
offset += port_byte_in(REG_SCREEN_DATA);
|
||||
return offset * 2; /* Position * size of character cell */
|
||||
}
|
||||
|
||||
void set_cursor_offset(int offset) {
|
||||
/* Similar to get_cursor_offset, but instead of reading we write data */
|
||||
offset /= 2;
|
||||
port_byte_out(REG_SCREEN_CTRL, 14);
|
||||
port_byte_out(REG_SCREEN_DATA, (unsigned char)(offset >> 8));
|
||||
port_byte_out(REG_SCREEN_CTRL, 15);
|
||||
port_byte_out(REG_SCREEN_DATA, (unsigned char)(offset & 0xff));
|
||||
}
|
||||
|
||||
void clear_screen() {
|
||||
int screen_size = MAX_COLS * MAX_ROWS;
|
||||
int i;
|
||||
char *screen = VIDEO_ADDRESS;
|
||||
|
||||
for (i = 0; i < screen_size; i++) {
|
||||
screen[i*2] = ' ';
|
||||
screen[i*2+1] = WHITE_ON_BLACK;
|
||||
}
|
||||
set_cursor_offset(get_offset(0, 0));
|
||||
}
|
||||
|
||||
|
||||
int get_offset(int col, int row) { return 2 * (row * MAX_COLS + col); }
|
||||
int get_offset_row(int offset) { return offset / (2 * MAX_COLS); }
|
||||
int get_offset_col(int offset) { return (offset - (get_offset_row(offset)*2*MAX_COLS))/2; }
|
||||
@ -0,0 +1,19 @@
|
||||
#ifndef SCREEN_H
|
||||
#define SCREEN_H
|
||||
|
||||
#define VIDEO_ADDRESS 0xb8000
|
||||
#define MAX_ROWS 25
|
||||
#define MAX_COLS 80
|
||||
#define WHITE_ON_BLACK 0x0f
|
||||
#define RED_ON_WHITE 0xf4
|
||||
|
||||
/* Screen i/o ports */
|
||||
#define REG_SCREEN_CTRL 0x3d4
|
||||
#define REG_SCREEN_DATA 0x3d5
|
||||
|
||||
/* Public kernel API */
|
||||
void clear_screen();
|
||||
void kprint_at(char *message, int col, int row);
|
||||
void kprint(char *message);
|
||||
|
||||
#endif
|
||||
@ -0,0 +1,11 @@
|
||||
#include "../drivers/screen.h"
|
||||
#include "util.h"
|
||||
#include "../cpu/isr.h"
|
||||
#include "../cpu/idt.h"
|
||||
|
||||
void main() {
|
||||
isr_install();
|
||||
/* Test the interrupts */
|
||||
__asm__ __volatile__("int $2");
|
||||
__asm__ __volatile__("int $3");
|
||||
}
|
||||
@ -0,0 +1,30 @@
|
||||
#include "util.h"
|
||||
|
||||
void memory_copy(char *source, char *dest, int nbytes) {
|
||||
int i;
|
||||
for (i = 0; i < nbytes; i++) {
|
||||
*(dest + i) = *(source + i);
|
||||
}
|
||||
}
|
||||
|
||||
void memory_set(u8 *dest, u8 val, u32 len) {
|
||||
u8 *temp = (u8 *)dest;
|
||||
for ( ; len != 0; len--) *temp++ = val;
|
||||
}
|
||||
|
||||
/**
|
||||
* K&R implementation
|
||||
*/
|
||||
void int_to_ascii(int n, char str[]) {
|
||||
int i, sign;
|
||||
if ((sign = n) < 0) n = -n;
|
||||
i = 0;
|
||||
do {
|
||||
str[i++] = n % 10 + '0';
|
||||
} while ((n /= 10) > 0);
|
||||
|
||||
if (sign < 0) str[i++] = '-';
|
||||
str[i] = '\0';
|
||||
|
||||
/* TODO: implement "reverse" */
|
||||
}
|
||||
@ -0,0 +1,5 @@
|
||||
#include "../cpu/types.h"
|
||||
|
||||
void memory_copy(char *source, char *dest, int nbytes);
|
||||
void memory_set(u8 *dest, u8 val, u32 len);
|
||||
void int_to_ascii(int n, char str[]);
|
||||
Loading…
Reference in new issue