Kernel fix (#28)

* cleaned up stuff

* fixed the looping issue on interrupts. it was the motherfucking kernel_entry page directory offset.

* yoinked aaron's GDT code to test paging issue. turns out it was.

* GDT fix

Makefile

@@ -51,6 +51,12 @@ image: boot kernel
 run: default
  $(QEMU) -drive format=raw,file=$(BUILD_DIR)/os_image -serial stdio
 
+monitor: default
+ $(QEMU) -drive format=raw,file=$(BUILD_DIR)/os_image -serial stdio -monitor unix:qemu-monitor-socket,server,nowait
+
+connect:
+ socat -,echo=0,icanon=0 unix-connect:qemu-monitor-socket
+
 gdb: default
  # Need to have GEF installed for this to work
  $(QEMU) -drive format=raw,file=$(BUILD_DIR)/os_image -s -S & gdb -ex "gef-remote --qemu-user localhost 1234" build/kernel.elf

source/kernel/gdt.c

@@ -0,0 +1,16 @@
+#include "gdt.h"
+#include <stdint.h>
+
+gdt_t gdt;
+
+void init_gdt() {
+ gdt_entry_t null_entry = {0,0,0,0,0,0};
+ gdt_entry_t code_segment = {0xffff,0,0,0b10011010,0b11001111,0};
+ gdt_entry_t data_segment = {0xffff,0,0,0b10010010,0b11001111,0};
+ gdt = (gdt_t) {
+ .limit = sizeof(gdt.entries)-1,
+ .base = (uint32_t) &gdt.entries,
+ .entries = {null_entry, code_segment, data_segment}
+ };
+ gdt_flush((uint32_t) &gdt);
+}

source/kernel/gdt_flush.asm

@@ -0,0 +1,15 @@
+global gdt_flush
+gdt_flush:
+ mov eax, [esp+4] ; eax = gdt_ptr
+ lgdt [eax] ; load the GDT pointer
+
+ mov ax, 0x10 ; 0x10 is kernel segment data descriptor offset
+ mov ds, ax 
+ mov es, ax
+ mov fs, ax
+ mov gs, ax
+ mov ss, ax
+ jmp 0x08:.flush ; 0x08 is kernel segment code descriptor offset
+ ; far jump to .flush
+.flush:
+ ret

source/kernel/idt.c

@@ -19,39 +19,6 @@ __attribute__((aligned(0x10))) static idt_entry_t idt[NUM_IDTS];
 // define the idtr
 static idtr_t idtr;
 
-static uint32_t has_triggered = 0;
-static uint32_t hits = 0;
-static uint32_t oopsie_woopsie = 0;
-
-uint32_t get_hits(void) { return oopsie_woopsie; }
-
-// we no-inline because I don't want it inlined :lemonthink:
-// also i want the actual isr to only have save register, call, then iret
-__attribute__((noinline)) static void actual_exception_handler(void)
-{
- oopsie_woopsie++;
-}
-
-// this currently will triple-fault on pressing a keyboard
-__attribute__((noinline)) static void actualirq1Handler(void)
-{
- // seems to triple fault before reaching here, idk pls can we get serial
- // driver
- hits++;
- if (terminal_driver_loaded() && !has_triggered) {
- terminal_putchar('U');
- terminal_update_cursor();
- // inb(0x60) is the port containing the key pressed
- terminal_put64(inb(0x60));
- terminal_update_cursor();
-
- // send eoi to the master PIC
- // this is needed in the PIC remapping, don't question it
- outb(0x20, 0x20);
- __asm__ volatile("cli");
- }
-}
-
 void idt_set_entry(int idx, uint32_t handler_ptr, uint16_t code_selector,
  uint8_t attributes)
 {

source/kernel/include/gdt.h

@@ -0,0 +1,22 @@
+#pragma once
+#include <stdint.h>
+
+#define GDT_ENTRIES 3
+
+typedef struct {
+ uint16_t limit;
+ uint16_t base_low;
+ uint8_t base_mid;
+ uint8_t access;
+ uint8_t granularity;
+ uint8_t base_high;
+} __attribute__((packed)) gdt_entry_t;
+
+typedef struct {
+ uint16_t limit;
+ uint32_t base;
+ gdt_entry_t entries[GDT_ENTRIES];
+} __attribute__((packed)) gdt_t;
+
+void init_gdt();
+extern void gdt_flush(uint32_t gdt_descriptor_ptr);

source/kernel/isr.c

@@ -21,6 +21,8 @@ void breakpoint(registers_t *frame) { printf("breakpoint\n"); }
 
 void overflow(registers_t *frame) { printf("overflow trap\n"); }
 
+void pagefault(registers_t *frame) { printf("page fault\n"); asm volatile("hlt");}
+
 void init_isr()
 {
  for (int i = 0; i < 256; i++)
@@ -31,6 +33,8 @@ void init_isr()
  register_interrupt_handler(3, &breakpoint);
  register_interrupt_handler(4, &overflow);
 
+ register_interrupt_handler(0xe, &pagefault);
+
  // irq handlers
  register_interrupt_handler(33, &keyboard_irq);
 

source/kernel/kernel.c

@@ -7,37 +7,14 @@
 #include "terminal_driver.h"
 #include "timer.h"
 #include <stdint.h>
+#include "gdt.h"
 
 void main()
 {
+ init_gdt();
  init_drivers();
  terminal_clear();
- init_paging();
  terminal_update_cursor();
  init_idt();
- asm volatile("int $0x3");
- asm volatile("int $0x4");
-
- write_serial(COM1, "Hello From SecureOS!");
- // printf(s.data);
-
- // init_paging();
- // string s;
- // s.data =
- // "HEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEELLLLLLLLLLLLLLLLLLLLLLLLLLL"
- // "LLOOOOOOOOOOOOOOOOOOOOOOOOOOOOO";
- // s.len = 96;
- // printf(&s);
- // uint32_t* wow = (uint32_t*) 0x12340000;
- // palloc(wow, PAGE_PRESENT | PAGE_RW);
- // *wow = 0x42042069;
- // terminal_put64(*wow);
- // for (int i = 0; i < 30; i ++) {
- // uint32_t* smol = kalloc(200);
- // *smol = 0x12345678;
- // terminal_put64(smol);
- // terminal_putchar(' ');
- // terminal_put64(*smol);
- // terminal_putchar('\n');
- // }
+ init_paging();
 }

source/kernel/memory.c

@@ -1,7 +1,7 @@
 #include "memory.h"
 #include "terminal_driver.h"
+#include "io.h"
 #include <stdint.h>
-#include <stdlib.h>
 
 uint32_t l2_page_table[1024] __attribute__((aligned(4096)));
 
@@ -263,6 +263,7 @@ void print_chunks()
  printf("}\n\n");
 }
 
+#include "serial.h"
 void init_paging()
 {
  // unmap lower page