Initial implementation of GDT
This commit is contained in:
parent
72ffbdee0d
commit
2859788682
@ -32,20 +32,20 @@ $(KERNEL_ARCH_OBJS) \
|
||||
kernel/kernel.o \
|
||||
|
||||
OBJS=\
|
||||
$(ARCHDIR)/crti.o \
|
||||
$(ARCHDIR)/boot/crti.o \
|
||||
$(ARCHDIR)/crtbegin.o \
|
||||
$(KERNEL_OBJS) \
|
||||
$(ARCHDIR)/crtend.o \
|
||||
$(ARCHDIR)/crtn.o \
|
||||
$(ARCHDIR)/boot/crtn.o \
|
||||
|
||||
LINK_LIST=\
|
||||
$(LDFLAGS) \
|
||||
$(ARCHDIR)/crti.o \
|
||||
$(ARCHDIR)/boot/crti.o \
|
||||
$(ARCHDIR)/crtbegin.o \
|
||||
$(KERNEL_OBJS) \
|
||||
$(LIBS) \
|
||||
$(ARCHDIR)/crtend.o \
|
||||
$(ARCHDIR)/crtn.o \
|
||||
$(ARCHDIR)/boot/crtn.o \
|
||||
|
||||
.PHONY: all clean install install-headers install-kernel
|
||||
.SUFFIXES: .o .c .S
|
||||
|
@ -25,10 +25,11 @@ stack_top:
|
||||
.type _start, @function
|
||||
_start:
|
||||
movl $stack_top, %esp
|
||||
call _init # call global constructors
|
||||
cli
|
||||
call gdt_init # call global constructors
|
||||
call kernel_main # transfer control to main kernel
|
||||
# Hang if kernel_main unexpectedly returns
|
||||
cli
|
||||
1: hlt
|
||||
jmp 1b
|
||||
|
||||
.size _start, . - _start
|
48
kernel/arch/i386/boot/gdt.c
Normal file
48
kernel/arch/i386/boot/gdt.c
Normal file
@ -0,0 +1,48 @@
|
||||
/**
|
||||
* Referenced from https://github.com/tendstofortytwo/clay
|
||||
* kernel/kernel.c
|
||||
*/
|
||||
|
||||
#include <kernel/gdt.h>
|
||||
#include <stdio.h>
|
||||
#include <stdint.h>
|
||||
|
||||
uint32_t TSS[32];
|
||||
gdt_entry GDT[GDT_ENTRIES];
|
||||
gdt_ptr gp;
|
||||
|
||||
void gdt_fill(gdt_entry* target, gdt* source) {
|
||||
if(source->limit > 0xFFFFF) {
|
||||
printf("Invalid GDT limit %d\n", source->limit);
|
||||
for(;;);
|
||||
}
|
||||
|
||||
target->limit_lo = source->limit & 0xFFFF;
|
||||
target->limit_hi_flags = (source->limit >> 16) & 0x0F;
|
||||
target->base_lo = source->base & 0xFFFF;
|
||||
target->base_mid = (source->base >> 16) & 0xFF;
|
||||
target->base_hi = (source->base >> 24) & 0xFF;
|
||||
target->access = source->access;
|
||||
target->limit_hi_flags |= (source->flags << 4);
|
||||
}
|
||||
|
||||
void gdt_init(void) {
|
||||
uint32_t tssRef = (uint32_t) TSS;
|
||||
gdt rows[GDT_ENTRIES] = {
|
||||
{0, 0x00000, 0x00, 0x0}, // 0x0000 Null Descriptor
|
||||
{0, 0xFFFFF, 0x9A, 0xC}, // 0x0008 Kernel Mode Code Segment
|
||||
{0, 0xFFFFF, 0x92, 0xC}, // 0x0010 Kernel Mode Data Segment
|
||||
{0, 0xFFFFF, 0xFA, 0xC}, // 0x0018 User Mode Code Segment
|
||||
{0, 0xFFFFF, 0xF2, 0xC}, // 0x0020 User Mode Data Segment
|
||||
{tssRef, sizeof(TSS), 0x89, 0x0}, // 0x0028 Task State Segment
|
||||
};
|
||||
|
||||
for(uint32_t i = 0; i < GDT_ENTRIES; ++i) {
|
||||
gdt_fill(GDT+i, rows+i);
|
||||
}
|
||||
|
||||
gp.base = (void*) GDT;
|
||||
gp.limit = (GDT_ENTRIES * sizeof(gdt_entry)) - 1;
|
||||
|
||||
gdt_load();
|
||||
}
|
20
kernel/arch/i386/boot/gdt_load.S
Normal file
20
kernel/arch/i386/boot/gdt_load.S
Normal file
@ -0,0 +1,20 @@
|
||||
# Referenced from https://github.com/tendstofortytwo/clay
|
||||
# kernel/boot/gdt.s
|
||||
|
||||
.global gdt_load
|
||||
.type gdt_load, @function
|
||||
gdt_load:
|
||||
lgdt (gp)
|
||||
mov %cr0, %eax
|
||||
or $0x1, %eax
|
||||
mov %eax, %cr0
|
||||
jmp $0x08, $reload
|
||||
|
||||
reload:
|
||||
mov $0x10, %ax
|
||||
mov %ax, %ds
|
||||
mov %ax, %es
|
||||
mov %ax, %fs
|
||||
mov %ax, %gs
|
||||
mov %ax, %ss
|
||||
ret
|
@ -4,5 +4,7 @@ KERNEL_ARCH_LDFLAGS=
|
||||
KERNEL_ARCH_LIBS=
|
||||
|
||||
KERNEL_ARCH_OBJS=\
|
||||
$(ARCHDIR)/boot.o \
|
||||
$(ARCHDIR)/tty.o \
|
||||
$(ARCHDIR)/boot/boot.o \
|
||||
$(ARCHDIR)/vga/tty.o \
|
||||
$(ARCHDIR)/boot/gdt.o \
|
||||
$(ARCHDIR)/boot/gdt_load.o
|
||||
|
42
kernel/include/kernel/gdt.h
Normal file
42
kernel/include/kernel/gdt.h
Normal file
@ -0,0 +1,42 @@
|
||||
/**
|
||||
* Referenced from https://tendstofortytwo/clay
|
||||
* kernel/kernel.c
|
||||
*/
|
||||
|
||||
#ifndef _KERNEL_GDT_H
|
||||
#define _KERNEL_GDT_H
|
||||
|
||||
#include <stdint.h>
|
||||
|
||||
#define GDT_ENTRIES 0x6
|
||||
|
||||
typedef struct {
|
||||
uint16_t limit;
|
||||
uint32_t base;
|
||||
}__attribute__((packed)) gdt_ptr;
|
||||
|
||||
typedef struct {
|
||||
uint16_t limit_lo;
|
||||
uint16_t base_lo;
|
||||
uint8_t base_mid;
|
||||
uint8_t access;
|
||||
uint8_t limit_hi_flags;
|
||||
uint8_t base_hi;
|
||||
}__attribute__((packed)) gdt_entry;
|
||||
|
||||
typedef struct {
|
||||
uint32_t base;
|
||||
uint32_t limit;
|
||||
uint8_t access;
|
||||
uint8_t flags;
|
||||
}__attribute__((packed)) gdt;
|
||||
|
||||
void gdt_fill(gdt_entry*, gdt*);
|
||||
void gdt_init(void);
|
||||
extern void gdt_load();
|
||||
|
||||
extern uint32_t TSS[32];
|
||||
extern gdt_entry GDT[GDT_ENTRIES];
|
||||
extern gdt_ptr gp;
|
||||
|
||||
#endif
|
@ -1,6 +1,7 @@
|
||||
#include <stdio.h>
|
||||
|
||||
#include <kernel/tty.h>
|
||||
#include <kernel/gdt.h>
|
||||
|
||||
void kernel_main(void) {
|
||||
terminal_initialize();
|
||||
|
Reference in New Issue
Block a user