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Basics for an proper GDT and IDT

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This commit is contained in:
Nigel Barink 2021-05-12 23:03:00 +01:00
parent b41f6a380e
commit 5e668f5e67
10 changed files with 590 additions and 26 deletions
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6
Makefile
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@ -5,7 +5,7 @@ CC = ${HOME}/opt/cross/bin/i686-elf-gcc
CPP = ${HOME}/opt/cross/bin/i686-elf-g++
CFLAGS = -ffreestanding -O2 -Wall -Wextra
OFILES = $(BUILD_DIR)/boot.o $(BUILD_DIR)/kterm.o $(BUILD_DIR)/kernel.o $(BUILD_DIR)/io.o $(BUILD_DIR)/MMU.o
OFILES = $(BUILD_DIR)/boot.o $(BUILD_DIR)/kterm.o $(BUILD_DIR)/kernel.o $(BUILD_DIR)/io.o $(BUILD_DIR)/MMU.o $(BUILD_DIR)/idt.o
SRC_DIR = src
BUILD_DIR = build
@ -56,4 +56,6 @@ $(BUILD_DIR)/crtn.o:
$(BUILD_DIR)/io.o:
$(CPP) -c $(SRC_DIR)/kernel/io.cpp -o $(BUILD_DIR)/io.o $(CFLAGS) -fno-exceptions -fno-rtti
$(BUILD_DIR)/MMU.o:
$(CPP) -c $(SRC_DIR)/kernel/MMU.cpp -o $(BUILD_DIR)/MMU.o $(CFLAGS) -fno-exceptions -fno-rtti
$(CPP) -c $(SRC_DIR)/kernel/MMU.cpp -o $(BUILD_DIR)/MMU.o $(CFLAGS) -fno-exceptions -fno-rtti
$(BUILD_DIR)/idt.o:
$(CPP) -c $(SRC_DIR)/kernel/idt.cpp -o $(BUILD_DIR)/idt.o $(CFLAGS) -fno-exceptions -fno-rtti

381
src/kernel/arch/i386/boot.s
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@ -20,8 +20,12 @@ stack_bottom:
.skip 16384 # 16 KiB
stack_top:
.text
.globl idt_flush
idt_flush:
mov 4(%esp), %eax
lidt (%eax)
ret
.text
.globl enablePaging
@ -51,20 +55,369 @@ loadPageDirectory:
.global _start
.type _start, @function
_start:
/*Setup the stack pointer to point to the beginning of our stack */
/* I believe its a hight address growing down to lower adress for the stack on x86*/
mov $stack_top, %esp
call early_main
load_gdt:
lgdt gdt
# set the segment selecters
movw $0x10, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
movw %ax, %gs
movw %ax, %ss
ljmp $0x08, $flush
flush:
#load idt
call init_idt
# Try enable A20
# mov $0x2401, %ax
# int $0x15
call _init
call kernel_main
# enable protected mode
mov %cr0, %eax
or $1, %eax
mov %eax, %cr0
cli
1: hlt
jmp 1b
call kernel_main
.size _start, . - _start
cli
1: hlt
jmp 1b
/* Tell processor to use our gdt*/
gdt:
.word (gdt_end - gdt_start -1) # Size of the GDT in bytes minus 1 for math reasons
.int gdt_start # linear address of our GDT
.att_syntax
.size _start, . - _start
/*
* Interupt handlers
*/
.text
.macro irq_NoErrCode code:req
.globl irq\code
irq\code:
cli
pushb $0
pushb \code
jmp irq_common
.endm
.text
.macro irq_ErrCode code
.globl irq\code
irq\code:
cli
pushb \code
jmp irq_common
.endm
.globl irq0
irq0:
cli
push $0
push $0
jmp irq_common
.globl irq1
irq1:
cli
push $0
push $1
jmp irq_common
.globl irq2
irq2:
cli
push $0
push $2
jmp irq_common
.globl irq3
irq3:
cli
push $0
push $3
jmp irq_common
.globl irq4
irq4:
cli
push $0
push $4
jmp irq_common
.globl irq5
irq5:
cli
push $0
push $5
jmp irq_common
.globl irq6
irq6:
cli
push $0
push $6
jmp irq_common
.globl irq7
irq7:
cli
push $0
push $7
jmp irq_common
.globl irq8
irq8:
cli
push $0
push $8
jmp irq_common
.globl irq9
irq9:
cli
push $0
push $9
jmp irq_common
.globl irq10
irq10:
cli
push $0
push $10
jmp irq_common
.globl irq11
irq11:
cli
push $0
push $11
jmp irq_common
.globl irq12
irq12:
cli
push $0
push $12
jmp irq_common
.globl irq13
irq13:
cli
push $0
push $13
jmp irq_common
.globl irq14
irq14:
cli
push $0
push $14
jmp irq_common
.globl irq15
irq15:
cli
push $0
push $15
jmp irq_common
.globl irq16
irq16:
cli
push $0
push $16
jmp irq_common
.globl irq17
irq17:
cli
push $0
push $17
jmp irq_common
.globl irq18
irq18:
cli
push $0
push $18
jmp irq_common
.globl irq19
irq19:
cli
push $0
push $19
jmp irq_common
.globl irq20
irq20:
cli
push $0
push $20
jmp irq_common
.globl irq21
irq21:
cli
push $0
push $21
jmp irq_common
.globl irq22
irq22:
cli
push $0
push $22
jmp irq_common
.globl irq23
irq23:
cli
push $0
push $23
jmp irq_common
.globl irq24
irq24:
cli
push $0
push $24
jmp irq_common
.globl irq25
irq25:
cli
push $0
push $25
jmp irq_common
.globl irq26
irq26:
cli
push $0
push $26
jmp irq_common
.globl irq27
irq27:
cli
push $0
push $27
jmp irq_common
.globl irq28
irq28:
cli
push $0
push $28
jmp irq_common
.globl irq29
irq29:
cli
push $0
push $29
jmp irq_common
.globl irq30
irq30:
cli
push $0
push $30
jmp irq_common
.globl irq31
irq31:
cli
push $0
push $31
jmp irq_common
.text
irq_common:
pusha # Pushes edi,esi,ebp,esp,ebx,edx,ecx,eax
mov %ds, %ax
push %eax
/* load the kernel data segment descriptor*/
mov $0x10, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
call irq_handler
pop %eax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
popa
add $8, %esp # cleans push error and irq code
sti
iret # pops 5 things at once: CS, EIP, EFLAGS, SS, and ESP
/*
* Create the GDT
*/
.section .data
gdt_start:
gdt_null:
.long 0x0
.long 0x0
gdt_kcode:
.word 0xFFFF # limit
.word 0x0 # base
.byte 0x0 # base
.byte 0b10011010 # 1st flags | type flags
.byte 0b11001111 # 2nd flags | limit
.byte 0x0 # base
gdt_kdata:
.word 0xFFFF # limit
.word 0x0 # base
.byte 0x0 # base
.byte 0b10010010 # 1st flags | type flags
.byte 0b11001111 # 2nd flags | limit
.byte 0x0 # base
gdt_end:

1
src/kernel/arch/i386/tty/kterm.c
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@ -89,4 +89,3 @@ void kterm_writestring(const char* data ){
AS_KERNEL();
kterm_write(data, strlen(data));
}

1
src/kernel/arch/i386/tty/kterm.h
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@ -15,6 +15,7 @@ void kterm_putat(char, uint8_t, size_t, size_t);
void kterm_put(char);
void kterm_write(const char*, size_t);
void kterm_writestring(const char*);
void kterm_scrollup();
#define KernelTag "[Kernel]: "

29
src/kernel/gdtc.cpp Normal file
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@ -0,0 +1,29 @@
#include "gdtc.h"
gdtEntry_t gdt[3];
void gdtSetGate(int num, uint64_t base, uint64_t limit, uint8_t access,
uint8_t gran){
gdt[num].lBase = (base & 0xFFFF);
gdt[num].mBase = (base >> 16) & 0xFF;
gdt[num].hBase = (base >> 24) & 0xFF;
gdt[num].lLimit = (limit & 0xFFFF);
gdt[num].granularity = ((limit >> 16) & 0x0F);
gdt[num].granularity |= (gran & 0xF0);
gdt[num].access = access;
}
void setupGdt(){
gdtPointer.limit = (sizeof(gdtEntry_t) * 3) - 1;
gdtPointer.base = &gdt;
gdtSetGate(0, 0, 0, 0, 0);
gdtSetGate(1, 0, 0xFFFFFFFF, 0x9A, 0xCF);
gdtSetGate(2, 0, 0xFFFFFFFF, 0x92, 0xCF);
loadGdt();
}

20
src/kernel/gdtc.h Normal file
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@ -0,0 +1,20 @@
#include <stdint.h>
extern "c"{
typedef struct {
uint16_t lLimit;
uint16_t lBase;
uint8_t mBase;
uint8_t access;
uint8_t granularity;
uint8_t hBase;
} gdtEntry_t;
struct {
uint16_t limit;
uint32_t base;
} gdtPointer;
extern void loadGdt();
void setupGdt();
}

64
src/kernel/idt.cpp Normal file
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@ -0,0 +1,64 @@
#include "idt.h"
IDT_entry idt_table[256];
IDT_ptr idt_ptr;
void set_id_entry (uint8_t num , uint32_t base, uint16_t sel, uint8_t flags){
idt_table[num].offset_1 = base & 0xFFFF;
idt_table[num].selector = sel;
idt_table[num].zero = 0;
idt_table[num].type_attr = flags;
idt_table[num].offset_2 = (base >> 16) & 0xFFFF;
};
void irq_handler (registers regs) {
kterm_writestring("received interrupt!");
}
void init_idt(){
// Initialise the IDT pointer
idt_ptr.length = sizeof(IDT_entry) * 255;
idt_ptr.base = (uint32_t)&idt_table;
// TODO: Set everything to zero first
set_id_entry(0, (uint32_t) irq0 , 0x08, 0x8E);
set_id_entry(1, (uint32_t) irq1 , 0x08, 0x8E);
set_id_entry(2, (uint32_t) irq2 , 0x08, 0x8E);
set_id_entry(3, (uint32_t) irq3 , 0x08, 0x8E);
set_id_entry(4, (uint32_t) irq4 , 0x08, 0x8E);
set_id_entry(5, (uint32_t) irq5 , 0x08, 0x8E);
set_id_entry(6, (uint32_t) irq6 , 0x08, 0x8E);
set_id_entry(7, (uint32_t) irq7 , 0x08, 0x8E);
set_id_entry(8, (uint32_t) irq8 , 0x08, 0x8E);
set_id_entry(9, (uint32_t) irq9 , 0x08, 0x8E);
set_id_entry(10, (uint32_t) irq10 , 0x08, 0x8E);
set_id_entry(11, (uint32_t) irq11 , 0x08, 0x8E);
set_id_entry(12, (uint32_t) irq12 , 0x08, 0x8E);
set_id_entry(13, (uint32_t) irq13 , 0x08, 0x8E);
set_id_entry(14, (uint32_t) irq14 , 0x08, 0x8E);
set_id_entry(15, (uint32_t) irq15 , 0x08, 0x8E);
set_id_entry(16, (uint32_t) irq16 , 0x08, 0x8E);
set_id_entry(17, (uint32_t) irq17 , 0x08, 0x8E);
set_id_entry(18, (uint32_t) irq18 , 0x08, 0x8E);
set_id_entry(19, (uint32_t) irq19 , 0x08, 0x8E);
set_id_entry(20, (uint32_t) irq20 , 0x08, 0x8E);
set_id_entry(21, (uint32_t) irq21 , 0x08, 0x8E);
set_id_entry(22, (uint32_t) irq22 , 0x08, 0x8E);
set_id_entry(23, (uint32_t) irq23 , 0x08, 0x8E);
set_id_entry(24, (uint32_t) irq24 , 0x08, 0x8E);
set_id_entry(25, (uint32_t) irq25 , 0x08, 0x8E);
set_id_entry(26, (uint32_t) irq26 , 0x08, 0x8E);
set_id_entry(27, (uint32_t) irq27 , 0x08, 0x8E);
set_id_entry(28, (uint32_t) irq28 , 0x08, 0x8E);
set_id_entry(29, (uint32_t) irq29 , 0x08, 0x8E);
set_id_entry(30, (uint32_t) irq30 , 0x08, 0x8E);
set_id_entry(31, (uint32_t) irq31 , 0x08, 0x8E);
idt_flush((uint32_t)&idt_ptr);
}

70
src/kernel/idt.h Normal file
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@ -0,0 +1,70 @@
#pragma once
#include "stdint.h"
extern "C" void kterm_writestring(const char* data );
extern "C" {
struct __attribute__((__packed__)) IDT_entry {
uint16_t offset_1;
uint16_t selector;
uint8_t zero;
uint8_t type_attr;
uint16_t offset_2;
};
struct __attribute__((__packed__)) IDT_ptr {
unsigned short length;
unsigned long base;
};
struct registers {
uint32_t ds; // Data segment selector
uint32_t edi, esi, ebp, esp, ebx, edx, ecx, eax; // Pushed by pusha.
uint32_t int_no, err_code; // Interrupt number and error code (if applicable)
uint32_t eip, cs, eflags, useresp, ss;
};
extern void idt_flush(uint32_t);
void set_id_entry (uint8_t num , uint32_t base, uint16_t sel, uint8_t flags);
void init_idt();
void irq_handler (registers regs);
extern void irq0 ();
extern void irq1 ();
extern void irq2 ();
extern void irq3 ();
extern void irq4 ();
extern void irq5 ();
extern void irq6 ();
extern void irq7 ();
extern void irq8 ();
extern void irq9 ();
extern void irq10 ();
extern void irq11 ();
extern void irq12 ();
extern void irq13 ();
extern void irq14 ();
extern void irq15 ();
extern void irq16 ();
extern void irq17 ();
extern void irq18 ();
extern void irq19 ();
extern void irq20 ();
extern void irq21 ();
extern void irq22 ();
extern void irq23 ();
extern void irq24 ();
extern void irq25 ();
extern void irq26 ();
extern void irq27 ();
extern void irq28 ();
extern void irq29 ();
extern void irq30 ();
extern void irq31 ();
}

39
src/kernel/kernel.cpp
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@ -74,6 +74,12 @@ char read_serial() {
}
void print_serial(const char* string ){
for(size_t i = 0; i < strlen(string); i ++){
write_serial(string[i]);
}
}
void test_serial(){
/** Serial test **/
kterm_writestring("Writing to COM1 serial port:");
@ -93,11 +99,34 @@ void test_serial(){
}
extern "C" {
void early_main(){
init_serial();
print_serial("\033[31;42mEarly main called!\n");
}
void kernel_main (void) {
print_serial("\033[31;42mKernel main called!\n");
/** initialize terminal interface */
kterm_init();
/** Setup the MMU **/
kterm_writestring("Starting MMU...\n");
auto mmu = MMU();
mmu.enable();
kterm_writestring("MMU enabled!\n");
/** Wrtite stuff to the screen to test the terminal**/
kterm_writestring("Hello world!\n");
kterm_writestring("We got newline support!\n");
@ -114,14 +143,11 @@ extern "C" {
auto testObject = Test();
testObject.printMe();
/** Setup the MMU **/
kterm_writestring("Starting MMU...\n");
auto mmu = MMU();
mmu.enable();
kterm_writestring("MMU enabled!\n");
/** test interrupt handlers **/
//asm volatile ("int $0x3");
//asm volatile ("int $0x4");
/** Lets start using the serial port for debugging .. **/
// Hopefully once we go into realmode or do something that
@ -129,7 +155,6 @@ extern "C" {
// some situational awareness
//Serial serialbus = Serial::init();
test_serial();
}

5
src/kernel/kernel.h
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@ -1,7 +1,8 @@
#pragma once
extern "C" {
#include "../libc/include/string.h"
#include "arch/i386/tty/kterm.h"
#include "../libc/include/string.h"
#include "arch/i386/tty/kterm.h"
}
#include "MMU.h"
#include "io.h"
#include "idt.h"