Attempt to fix bootloader.

Makefile

@@ -5,6 +5,14 @@ CC=x86_64-elf-gcc
 run: image.bin
 	qemu-system-i386 -drive format=raw,file=$<
 
+debug-preboot: image.bin mbr.elf
+	qemu-system-i386 -drive format=raw,file=$< -s -S &
+	x86_64-elf-gdb mbr.elf \
+		-ex "set architecture i8086" \
+		-ex "target remote localhost:1234" \
+		-ex "break *0x7c00" \
+		-ex "continue"
+
 debug-boot: image.bin mbr.elf
 	qemu-system-i386 -drive format=raw,file=$< -s -S &
 	x86_64-elf-gdb mbr.elf \
@@ -41,7 +49,7 @@ mbr.elf: mbr.o
 	$(LD) -m elf_i386 -Ttext=0x7c00 $^ -o $@
 
 clean:
-	rm -f *.elf *.bin *.o */*.o tools/mkfs
+	rm -f *.elf *.img *.bin *.o */*.o tools/mkfs
 
 tools/%: tools/%.c
 	gcc -Wall -Werror -g $^ -o $@

console.c

@@ -4,3 +4,11 @@
 void printk(const char* msg) {
     vga_print_string(msg);
 }
+
+void panic(const char* msg) {
+    printk("Kernel panic: ");
+    printk(msg);
+    while (1) {
+        asm("hlt");
+    }
+}

console.h

@@ -1,3 +1,4 @@
 #pragma once
 
 void printk(const char* msg);
+void panic(const char* msg);

cpu/idt.c

@@ -33,6 +33,9 @@ void set_idt_gate(int n, uint32_t handler) {
 extern uint32_t default_handlers[];
 
 void init_idt() {
+    if (default_handlers[0] == 0) {
+        panic("handler table empty\n");
+    }
     for (int i = 0; i < IDT_HANDLERS; i++) {
         set_idt_gate(i, default_handlers[i]);
     }
@@ -126,11 +129,12 @@ static idt_register_t idt_reg;
 
 void load_idt() {
     init_idt();
-    init_pic();
 
     idt_reg.base = &idt;
     idt_reg.limit = sizeof(idt) - 1;
-    asm("lidt %0" : : "m"(idt_reg));
+    asm("lidt (%0)" : : "r"(&idt_reg));
+
+    init_pic();
 }
 
 void cli() {

cpu/vectors.S

@@ -45,7 +45,7 @@ vector\i :
 .global default_handlers
 default_handlers:
 .set i,0
-.rept 40
+.rept 256
     irq_insertX %i
     .set i, i+1
 .endr

mbr.S

@@ -5,11 +5,19 @@ _start:
     mov $banner, %si
     call print_string
 
+    call get_drive_geometry
     call load_kernel
     call switch_to_32bit
 
+    hlt
     jmp . // loop forever
 
+get_drive_geometry:
+    mov $8, %ah
+    mov boot_drive, %dl
+    int $0x13
+    // TODO
+
 
 .equ ELF32_ENTRY_OFFSET, 0x18
 .equ ELF32_PHDR_OFFSET, 0x1c
@@ -53,15 +61,30 @@ load_kernel:
 
 bios_disk_read:
     // expects %al to specify number of sectors, %cl the initial sector
-    mov $2, %ah             // read mode
+    xor %ah, %ah
+    mov %ax, %si
     mov $0, %ch             // cylinder 0
     mov $0, %dh             // head 0
     mov $KERNEL_OFFSET, %bx // bx -> destination
     mov boot_drive, %dl     // dl -> disk
+    mov $1, %al
+
+1:
+    mov $2, %ah             // read mode
     int $0x13
-    // no error checking, let's hope it works
+    test %ah, %ah
+    jnz fail
+    add $SECTOR_SIZE, %bx
+    inc %cl
+    dec %si
+    jnz 1b
     ret
 
+fail:
+    mov $read_error, %si
+    call print_string
+    hlt
+    jmp .
 
 switch_to_32bit:
     mov	$2, %al
@@ -111,6 +134,8 @@ boot_drive:
     .byte 0
 banner:
     .asciz "YABLOKO bootloader started\r\n"
+read_error:
+    .asciz "Read error\r\n"
 
     .balign 2
 entry: