Add some "kernel" code written in C

Draw few message on VGA
Setup Interruption Description Table
Setup IRQ

Makefile

@@ -1,8 +1,8 @@
 AS=nasm
 ASFLAGS += -f elf32
-LDFLAGS += -m32 -nostdlib -static -fno-common -fno-use-cxa-atexit -fno-exceptions -fno-non-call-exceptions -fno-weak -fno-rtti
+LDFLAGS += -m32 -nostdlib -static -fno-common -fno-use-cxa-atexit -fno-exceptions -fno-non-call-exceptions -fno-weak -fno-rtti -fno-stack-protector
-CFLAGS += -m32 -Wall -Wextra -Werror -ffreestanding  -fno-exceptions
+CFLAGS += -m32 -Wall -Wextra -Werror -ffreestanding  -fno-exceptions -fno-pie -fno-stack-protector
-CXXFLAGS += -m32 -Wall -Wextra -Werror -ffreestanding  -fno-exceptions -fno-rtti
+CXXFLAGS += -m32 -Wall -Wextra -Werror -ffreestanding  -fno-exceptions -fno-rtti -fno-pie 
 
 
 asmsrc=$(wildcard *.asm)

idt.c

@@ -0,0 +1,44 @@
+#include "idt.h"
+static struct idtEntry    idt[IDT_NUM];
+
+
+int idtSetup()
+{
+  struct idtRegister idtr;
+
+  for (int i = 0; i < IDT_NUM; i++) {
+	  struct idtEntry *idte = idt + i;
+
+	  /* Setup an empty IDTE interrupt gate, see figure 5-2 in Intel
+	     x86 doc, vol 3 */
+	  idte->seg_sel     = BUILD_SEGMENT_SELECTOR(RING_0, 0, SEGMENT_IDX_CODE);
+	  idte->reserved    = 0;
+	  idte->flags       = 0;
+	  idte->type	      = 0x6; /* Interrupt gate (110b) */
+	  idte->op_size     = 1;   /* 32bits instructions */
+
+    /* Disabled it for now */
+	  idte->zero	      = 0;
+	  idte->offset_low  = 0;
+	  idte->offset_high = 0;
+	  idte->dpl	        = 0;
+	  idte->present     = 0; 
+  }
+
+  /*
+   * Setup the IDT register, see Intel x86 doc vol 3, section 5.8.
+   */
+
+  /* Address of the IDT */
+  idtr.base_addr  = (uint32_t) idt;
+
+  /* The limit is the maximum offset in bytes from the base address of
+     the IDT */
+  idtr.limit      = sizeof(idt) - 1;
+
+  /* Commit the IDT into the CPU */
+  asm volatile ("lidt %0\n"::"m"(idtr):"memory");
+  
+  return 0;
+}
+

idt.h

@@ -0,0 +1,44 @@
+#pragma once
+#include "types.h"
+
+#define IDT_NUM 256
+
+#define RING_0 0
+#define RING_1 1
+#define RING_2 2
+#define RING_3 3
+
+#define SEGMENT_IDX_NULL 0
+#define SEGMENT_IDX_CODE 1
+#define SEGMENT_IDX_DATA 2
+
+struct idtEntry {
+	uint16_t offset_low;
+	uint16_t seg_sel;
+	uint8_t reserved : 5;
+	uint8_t flags : 3;
+	uint8_t type : 3;
+	uint8_t op_size : 1;
+	uint8_t zero : 1;
+	uint8_t dpl : 2;
+	uint8_t present : 1;
+	uint16_t offset_high;
+} __attribute__((packed));
+
+/**
+ * The IDT register, which stores the address and size of the
+ * IDT.
+ *
+ * @see Intel x86 doc vol 3, section 2.4, figure 2-4
+ */
+struct idtRegister {
+	uint16_t limit;
+	uint32_t base_addr;
+} __attribute__((packed, aligned(8)));
+
+/* Build segment http://wiki.osdev.org/Selector*/
+#define BUILD_SEGMENT_SELECTOR(desc_privilege, in_ldt, index)                  \
+	((((desc_privilege)&0x3) << 0) | (((in_ldt) ? 1 : 0) << 2) |           \
+	 ((index) << 3))
+
+int idtSetup();

io.h

@@ -0,0 +1,21 @@
+#pragma once
+#include "types.h"
+
+// NIH http://wiki.osdev.org/Inline_Assembly/Examples#I.2FO_access
+static inline void outb(uint16_t port, uint8_t val)
+{
+    asm volatile ( "outb %0, %1" : : "a"(val), "Nd"(port) );
+    /* There's an outb %al, $imm8  encoding, for compile-time constant port numbers that fit in 8b.  (N constraint).
+     * Wider immediate constants would be truncated at assemble-time (e.g. "i" constraint).
+     * The  outb  %al, %dx  encoding is the only option for all other cases.
+     * %1 expands to %dx because  port  is a uint16_t.  %w1 could be used if we had the port number a wider C type */
+}
+
+static inline uint8_t inb(uint16_t port)
+{
+    uint8_t ret;
+    asm volatile ( "inb %1, %0"
+                   : "=a"(ret)
+                   : "Nd"(port) );
+    return ret;
+}

irq.c

@@ -0,0 +1,8 @@
+#include "irq.h"
+#include "pic.h"
+
+int irqSetup()
+{
+	initPic();
+	return 0;
+}

irq.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#define IRQ_TIMER         0 // MASTER IRQ
+#define IRQ_KEYBOARD      1 
+#define IRQ_SLAVE_PIC     2 
+#define IRQ_COM2          3 
+#define IRQ_COM1          4 
+#define IRQ_LPT2          5 
+#define IRQ_FLOPPY        6 
+#define IRQ_LPT1          7
+#define IRQ_8_NOT_DEFINED 8 // SLAVE
+#define IRQ_RESERVED_1    9 // SLAVE IRQ
+#define IRQ_RESERVED_2    10
+#define IRQ_RESERVED_3    11
+#define IRQ_RESERVED_4    12
+#define IRQ_COPROCESSOR   13
+#define IRQ_HARDDISK      14
+#define IRQ_RESERVED_5    15
+
+typedef void (*irq_handler)(int irq);
+int irqSetup();

main.c

@@ -0,0 +1,37 @@
+#include "idt.h"
+#include "io.h"
+#include "irq.h"
+#include "types.h"
+#include "vga.h"
+
+char getScancode()
+{
+	char c = 0;
+	do {
+		if (inb(0x60) != c) {
+			c = inb(0x60);
+			if (c > 0)
+				return c;
+		}
+	} while (1);
+}
+
+void cpuid(int code, uint32_t *a, uint32_t *d)
+{
+	asm volatile("cpuid" : "=a"(*a), "=d"(*d) : "0"(code) : "ebx", "ecx");
+}
+
+void kmain()
+{
+	const short color = GREEN;
+	clearScreen(BLACK);
+	printString("Setting up IDT", color, BLACK, 0, 0);
+	idtSetup();
+	printString("Setting up IRQ", color, BLACK, 0, 1);
+	irqSetup();
+
+	while (1) {
+		char c = getScancode();
+		printChar(c, color, BLACK, 0, 5);
+	}
+}

mbr.asm

@@ -152,6 +152,14 @@ boot2:
 	add ebx,2
 	jmp .loop32
 halt:
+	mov esp,kernel_stack_top
+	extern kmain
+	call kmain
 	cli
 	hlt
 hello32: db "Hello 32 bits world!",0
+section .bss
+align 4
+kernel_stack_bottom: equ $
+	resb 16384 ; 16 KB
+kernel_stack_top:

pic.c

@@ -0,0 +1,64 @@
+#include "pic.h"
+#include "io.h"
+
+#define ICW1_ICW4	0x01		/* ICW4 (not) needed */
+#define ICW1_SINGLE	0x02		/* Single (cascade) mode */
+#define ICW1_INTERVAL4	0x04		/* Call address interval 4 (8) */
+#define ICW1_LEVEL	0x08		/* Level triggered (edge) mode */
+#define ICW1_INIT	0x10		/* Initialization - required! */
+
+#define ICW4_8086	0x01		/* 8086/88 (MCS-80/85) mode */
+#define ICW4_AUTO	0x02		/* Auto (normal) EOI */
+#define ICW4_BUF_SLAVE	0x08		/* Buffered mode/slave */
+#define ICW4_BUF_MASTER	0x0C		/* Buffered mode/master */
+#define ICW4_SFNM	0x10		/* Special fully nested (not) */
+
+void initPic(void)
+{
+	/* Send CMD: Init + senquence in 4 DATA */
+	outb(ICW1_INIT + ICW1_ICW4, PIC_MASTER_CMD);
+	outb(ICW1_INIT + ICW1_ICW4, PIC_SLAVE_CMD);
+
+	/* Send ICW2: ctrl base address. Remap IRQ from interupt range 0x0-0xF to 0x20-0x2F as
+	 * intel
+	 * reserve interupt 0x0-0x1F in protected mode (e.g. 0-7 are CPU exception)  */
+	outb(0x20, PIC_MASTER_DATA);
+	outb(0x28, PIC_SLAVE_DATA);
+
+	/* Send ICW3 master: mask where slaves are connected */
+	outb(0x4, PIC_MASTER_DATA);
+	/* Send ICW3 slave: index where the slave is connected on master */
+	outb(0x2, PIC_SLAVE_DATA);
+
+	/* Send ICW4: 8086 mode, fully nested, not buffered, no implicit EOI */
+	outb(ICW4_8086, PIC_MASTER_DATA);
+	outb(ICW4_8086, PIC_SLAVE_DATA);
+
+	/* Send OCW1:
+	 * Closing all IRQs : waiting for a correct handler The only IRQ
+	 * enabled is the cascade (that's why we use 0xFB for the master) */
+	outb(0xFB, PIC_MASTER_DATA);
+	outb(0xFF, PIC_SLAVE_DATA);
+}
+
+void enableIrq(int irq)
+{
+	if (irq < 8) {
+		uint8_t status = inb(PIC_MASTER_DATA);
+		outb((status | (1 << irq)), PIC_MASTER_DATA);
+	} else {
+		uint8_t status = inb(PIC_SLAVE_DATA);
+		outb((status | (1 << irq)), PIC_SLAVE_DATA);
+	}
+}
+
+void disableIrq(int irq)
+{
+	if (irq < 8) {
+		uint8_t status = inb(PIC_MASTER_DATA);
+		outb((status & ~(1 << irq)), PIC_MASTER_DATA);
+	} else {
+		uint8_t status = inb(PIC_SLAVE_DATA);
+		outb((status & ~(1 << irq)), PIC_SLAVE_DATA);
+	}
+}

pic.h

@@ -0,0 +1,18 @@
+#pragma once
+//2 PIC 8259 are available on x86
+//
+//    Master - command: 0x20, data: 0x21
+//    Slave - command: 0xA0, data: 0xA1
+//
+// http://www.jamesmolloy.co.uk/tutorial_html/5.-IRQs%20and%20the%20PIT.html
+// SimpleOS art2
+// http://wiki.osdev.org/PIC
+
+#define PIC_MASTER_CMD 0x20
+#define PIC_SLAVE_CMD  0xa0
+#define PIC_MASTER_DATA 0x21
+#define PIC_SLAVE_DATA  0xa0
+
+void initPic(void);
+void enableIrq(int irq);
+void disableIrq(int irq);

types.h

@@ -0,0 +1,36 @@
+#pragma once
+
+typedef __signed__ char __s8;
+typedef unsigned char __u8;
+
+typedef __signed__ short __s16;
+typedef unsigned short __u16;
+
+typedef __signed__ int __s32;
+typedef unsigned int __u32;
+
+#ifdef __GNUC__
+__extension__ typedef __signed__ long long __s64;
+__extension__ typedef unsigned long long __u64;
+#else
+typedef __signed__ long long __s64;
+typedef unsigned long long __u64;
+#endif
+
+/* sysv */
+typedef unsigned char		unchar;
+typedef unsigned short		ushort;
+typedef unsigned int		uint;
+typedef unsigned long		ulong;
+
+typedef		__s8		int8_t;
+typedef		__s16		int16_t;
+typedef		__s32		int32_t;
+
+typedef		__u8		uint8_t;
+typedef		__u16		uint16_t;
+typedef		__u32		uint32_t;
+
+typedef		__u64		uint64_t;
+typedef		__u64		u_int64_t;
+typedef		__s64		int64_t;

vga.c

@@ -0,0 +1,30 @@
+#include "vga.h"
+
+void clearScreen(int bgColor)
+{
+	volatile short *vga = (short *)VGA_ADDR;
+	long int colorAttr  = bgColor << 12;
+	for (int i = 0; i < VGA_WIDTH * VGA_HEIGHT; i++) {
+		vga[i] = colorAttr;
+	}
+}
+
+void printChar(const char str, int color, int bgColor, int startX, int startY)
+{
+	volatile short *vga	   = (short *)VGA_ADDR;
+	long int colorAttr	    = (bgColor << 4 | (color & 0x0f)) << 8;
+	vga[80 * startY + startX] = colorAttr | str;
+}
+
+void printString(const char *str, int color, int bgColor, int startX,
+		 int startY)
+{
+	volatile short *vga = (short *)VGA_ADDR;
+	int i		    = 0;
+	long int colorAttr  = (bgColor << 4 | (color & 0x0f)) << 8;
+	while (*str) {
+		vga[80 * startY + startX + i] = colorAttr | *str;
+		str++;
+		i++;
+	}
+}

vga.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#define BLACK   0x00
+#define BLUE    0x01
+#define GREEN   0x02
+#define CYAN    0x03
+#define RED     0x04
+#define MAGENTA 0x05
+#define BROWN   0x06
+#define GREY    0x07
+#define WHITE   0x0F
+
+#define VGA_ADDR   0xB8000
+#define VGA_WIDTH  80
+#define VGA_HEIGHT 15
+
+void clearScreen(int bgColor);
+void printChar(const char str, int color, int bgColor, int startX, int startY);
+void printString(const char *str, int color, int bgColor, int startX, int startY);