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gdt: remove anything left from C implementation of GDT

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This commit is contained in:
rusya
2025-03-18 16:24:11 +03:00
parent 086bac07ed
commit 22c7380c8d
8 changed files with 52 additions and 112 deletions
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src/boot.asm
+23 -5
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@@ -1,20 +1,39 @@
bits 32
section .text
section .multiboot
align 4
dd 0x1BADB002
dd 0x00
dd - (0x1BADB002+0x00)
section.data
align 4
multiboot_info:
dd 0 ; flags
dd 0 ; mem_lower
dd 0 ; mem_upper
dd 0 ; boot_device
dd 0 ; cmdline
dd 0 ; mods_count
dd 0 ; mods_addr
section .bss
stack_bottom:
resb 16384
stack_top:
section .gdt
%include "src/gdt.asm"
section .text
global start
;global start
global start:function (start.end - start)
extern kmain ; this function is gonna be located in our c code(kernel.c)
start:
cli ;clears the interrupts
mov esp, stack_top
; cli ;clears the interrupts
lgdt [gdt]
mov ax, DATA_SEG
@@ -29,7 +48,6 @@ start:
push ebx
call kmain ;send processor to continue execution from the kamin funtion in c code
;;;;;;;;;;;DIVISION BY ZERO TEST
; mov ax, 10
; mov bx, 0
@@ -37,4 +55,4 @@ start:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
hlt ; halt the cpu(pause it from executing from this address
.end:
src/gdt.c
-84
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@@ -1,84 +0,0 @@
#include "../include/gdt.h"
#include "../include/stdio.h"
#include <stdint.h>
struct gdt_entry {
uint64_t descriptor;
};
struct gdt_entry gdt[5];
// Each define here is for a specific flag in the descriptor.
// Refer to the intel documentation for a description of what each one does.
#define SEG_DESCTYPE(x) ((x) << 0x04) // Descriptor type (0 for system, 1 for code/data)
#define SEG_PRES(x) ((x) << 0x07) // Present
#define SEG_SAVL(x) ((x) << 0x0C) // Available for system use
#define SEG_LONG(x) ((x) << 0x0D) // Long mode
#define SEG_SIZE(x) ((x) << 0x0E) // Size (0 for 16-bit, 1 for 32)
#define SEG_GRAN(x) ((x) << 0x0F) // Granularity (0 for 1B - 1MB, 1 for 4KB - 4GB)
#define SEG_PRIV(x) (((x) & 0x03) << 0x05) // Set privilege level (0 - 3)
#define SEG_DATA_RD 0x00 // Read-Only
#define SEG_DATA_RDA 0x01 // Read-Only, accessed
#define SEG_DATA_RDWR 0x02 // Read/Write
#define SEG_DATA_RDWRA 0x03 // Read/Write, accessed
#define SEG_DATA_RDEXPD 0x04 // Read-Only, expand-down
#define SEG_DATA_RDEXPDA 0x05 // Read-Only, expand-down, accessed
#define SEG_DATA_RDWREXPD 0x06 // Read/Write, expand-down
#define SEG_DATA_RDWREXPDA 0x07 // Read/Write, expand-down, accessed
#define SEG_CODE_EX 0x08 // Execute-Only
#define SEG_CODE_EXA 0x09 // Execute-Only, accessed
#define SEG_CODE_EXRD 0x0A // Execute/Read
#define SEG_CODE_EXRDA 0x0B // Execute/Read, accessed
#define SEG_CODE_EXC 0x0C // Execute-Only, conforming
#define SEG_CODE_EXCA 0x0D // Execute-Only, conforming, accessed
#define SEG_CODE_EXRDC 0x0E // Execute/Read, conforming
#define SEG_CODE_EXRDCA 0x0F // Execute/Read, conforming, accessed
#define GDT_CODE_PL0 SEG_DESCTYPE(1) | SEG_PRES(1) | SEG_SAVL(0) | \
SEG_LONG(0) | SEG_SIZE(1) | SEG_GRAN(1) | \
SEG_PRIV(0) | SEG_CODE_EXRD
#define GDT_DATA_PL0 SEG_DESCTYPE(1) | SEG_PRES(1) | SEG_SAVL(0) | \
SEG_LONG(0) | SEG_SIZE(1) | SEG_GRAN(1) | \
SEG_PRIV(0) | SEG_DATA_RDWR
#define GDT_CODE_PL3 SEG_DESCTYPE(1) | SEG_PRES(1) | SEG_SAVL(0) | \
SEG_LONG(0) | SEG_SIZE(1) | SEG_GRAN(1) | \
SEG_PRIV(3) | SEG_CODE_EXRD
#define GDT_DATA_PL3 SEG_DESCTYPE(1) | SEG_PRES(1) | SEG_SAVL(0) | \
SEG_LONG(0) | SEG_SIZE(1) | SEG_GRAN(1) | \
SEG_PRIV(3) | SEG_DATA_RDWR
void create_descriptor(uint32_t base, uint32_t limit, uint16_t flag)
{
uint64_t descriptor;
// Create the high 32 bit segment
descriptor = limit & 0x000F0000; // set limit bits 19:16
descriptor |= (flag << 8) & 0x00F0FF00; // set type, p, dpl, s, g, d/b, l and avl fields
descriptor |= (base >> 16) & 0x000000FF; // set base bits 23:16
descriptor |= base & 0xFF000000; // set base bits 31:24
// Shift by 32 to allow for low part of segment
descriptor <<= 32;
// Create the low 32 bit segment
descriptor |= base << 16; // set base bits 15:0
descriptor |= limit & 0x0000FFFF; // set limit bits 15:0
printf("GDT descriptor 0x%X flag: 0x%X\n", descriptor, flag);
}
void gdt_install()
{
create_descriptor(0, 0, 0);
create_descriptor(0, 0x000FFFFF, (GDT_CODE_PL0));
create_descriptor(0, 0x000FFFFF, (GDT_DATA_PL0));
create_descriptor(0, 0x000FFFFF, (GDT_CODE_PL3));
create_descriptor(0, 0x000FFFFF, (GDT_DATA_PL3));
__asm__ __volatile__("lgdt (%0)" : : "r" (gdt));
printf("gdt_install done\n");
}
src/idt.c
+2 -1
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@@ -9,7 +9,8 @@ extern void* isr_stub_table[];
void idt_set() {
idtr.base = (uint32) &idt;
idtr.limit = sizeof(idt) * sizeof(idt_entry_t) - 1;
__asm__ __volatile__("lidtl (%0)" : : "r" (&idtr));
__asm__ __volatile__("lidt %0" : : "m" (idtr));
// __asm__ __volatile__("sti"); //TODO: fixme, make this fucking stinking sti work
}
src/isr.c
+9
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@@ -3,6 +3,8 @@
#include "../include/types.h"
#include "../include/screen.h"
void isr_custom();
void isr_install() {
idt_set_descriptor(0, (uint32)isr0, 0x8E);
idt_set_descriptor(1, (uint32)isr1, 0x8E);
@@ -36,11 +38,18 @@ void isr_install() {
idt_set_descriptor(29, (uint32)isr29, 0x8E);
idt_set_descriptor(30, (uint32)isr30, 0x8E);
idt_set_descriptor(31, (uint32)isr31, 0x8E);
idt_set_descriptor(0x21, (uint32)isr_custom, 0x8E);
idt_set(); // Load with ASM
terminal_writestring("isr_install done\n");
}
void isr_custom()
{
terminal_writestring("YOOOOO!!!!!! I LOVE KATYA!!!!");
asm("hlt");
}
void isr0()
{
terminal_writestring(exception_messages[0]);
src/kernel.c
-2
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@@ -1,5 +1,4 @@
#include "../include/isr.h"
#include "../include/gdt.h"
#include "../include/screen.h"
#include "../include/stdio.h"
#include "../include/utils.h"
@@ -12,7 +11,6 @@ void kmain()
{
terminal_initialize();
printf("KatauOS booting up\n");
// gdt_install();
isr_install();
printf("Kernel init sequence completed\n");