Small changes before adding gdt

7 files changed, 76 insertions, 271 deletions

diff --git a/Makefile b/Makefile
index 0a86795..86585c5 100644
--- a/Makefile
+++ b/Makefile
@@ -1,37 +1,34 @@
-CC = i686-elf-gcc
-AS = i686-elf-as
-CFLAGS = 
+CC=i686-elf-gcc
+AS=i686-elf-as
+CFLAGS=-ffreestanding -O2 -Wall -Wextra
 
-MKDIR = mkdir -p
-RM = rm -rf
-CP = cp
+MKDIR=mkdir -p
+RM=rm -rf
+CP=cp
 
-SOURCE_DIR = src
-BUILD_DIR = build
-ISO_DIR = isodir
+SOURCE_DIR=src
+BUILD_DIR=build
+ISO_DIR=isodir
 
-AS_SOURCE = boot.s
-C_SOURCE = kernel.c
+TARGET=myos
 
-OBJ_FILES = boot.o kernel.o
-CRTBEGIN_OBJ:=$(shell $(CC) -print-file-name=crtbegin.o)
-CRTEND_OBJ:=$(shell $(CC) -print-file-name=crtend.o)
-
-OBJ = $(BUILD_DIR)/crti.o $(CRTBEGIN_OBJ) $(patsubst %,$(BUILD_DIR)/%,$(OBJ_FILES)) $(CRTEND_OBJ) $(BUILD_DIR)/crtn.o
+OBJ_FILES=boot.o kernel.o
+CRTBEGIN_OBJ=$(shell $(CC) -print-file-name=crtbegin.o)
+CRTEND_OBJ=$(shell $(CC) -print-file-name=crtend.o)
+OBJ=$(BUILD_DIR)/crti.o $(CRTBEGIN_OBJ) $(patsubst %,$(BUILD_DIR)/%,$(OBJ_FILES)) $(CRTEND_OBJ) $(BUILD_DIR)/crtn.o
 
 # Creating iso file
-.PHONY: all
-all: $(BUILD_DIR)/myos.bin
+$(TARGET).iso: $(BUILD_DIR)/$(TARGET).bin
 	grub-file --is-x86-multiboot $(BUILD_DIR)/myos.bin
 	mkdir -p $(ISO_DIR)/boot/grub
 	$(CP) $(BUILD_DIR)/myos.bin $(ISO_DIR)/boot/myos.bin
 	$(CP) $(SOURCE_DIR)/grub.cfg $(ISO_DIR)/boot/grub/grub.cfg
-	grub-mkrescue -o myos.iso $(ISO_DIR)
+	grub-mkrescue -o $(TARGET).iso $(ISO_DIR)
 
 # Linking object files
-$(BUILD_DIR)/myos.bin: $(OBJ)
+$(BUILD_DIR)/$(TARGET).bin: $(OBJ)
 	$(MKDIR) $(BUILD_DIR)
-	$(CC) -T $(SOURCE_DIR)/linker.ld -o $(BUILD_DIR)/myos.bin -ffreestanding -O2 -nostdlib $(OBJ) -lgcc
+	$(CC) -T $(SOURCE_DIR)/linker.ld -o $@ $(CFLAGS) -nostdlib $^ -lgcc
 
 # Compiling as sources
 $(BUILD_DIR)/%.o: $(SOURCE_DIR)/%.s
@@ -41,9 +38,14 @@ $(BUILD_DIR)/%.o: $(SOURCE_DIR)/%.s
 # Compiling C sources
 $(BUILD_DIR)/%.o: $(SOURCE_DIR)/%.c
 	$(MKDIR) $(BUILD_DIR)
-	$(CC) -c $< -o $@ -std=gnu99 -ffreestanding -O2 -Wall -Wextra
+	$(CC) -c $< -o $@ -std=gnu99 $(CFLAGS)
+
+# Boot kernel in qemu
+.PHONY: run
+run: $(TARGET).iso
+	qemu-system-x86_64 -cdrom $(TARGET).iso
 
-# Cleaning
+# Clean build files
 .PHONY: clean
 clean:
-	$(RM) $(BUILD_DIR) $(ISO_DIR) myos.iso
+	$(RM) $(BUILD_DIR) $(ISO_DIR) $(TARGET).iso
diff --git a/qemu.sh b/qemu.sh
deleted file mode 100755
index 8080024..0000000
--- a/qemu.sh
+++ /dev/null
@@ -1 +0,0 @@
-qemu-system-x86_64 -cdrom myos.iso
diff --git a/src/boot.asm b/src/boot.asm
deleted file mode 100644
index 94b4c57..0000000
--- a/src/boot.asm
+++ /dev/null
@@ -1,90 +0,0 @@
-; Declare constants for the multiboot header.
-MBALIGN  equ  1 << 0            ; align loaded modules on page boundaries
-MEMINFO  equ  1 << 1            ; provide memory map
-FLAGS    equ  MBALIGN | MEMINFO ; this is the Multiboot 'flag' field
-MAGIC    equ  0x1BADB002        ; 'magic number' lets bootloader find the header
-CHECKSUM equ -(MAGIC + FLAGS)   ; checksum of above, to prove we are multiboot
- 
-; Declare a multiboot header that marks the program as a kernel. These are magic
-; values that are documented in the multiboot standard. The bootloader will
-; search for this signature in the first 8 KiB of the kernel file, aligned at a
-; 32-bit boundary. The signature is in its own section so the header can be
-; forced to be within the first 8 KiB of the kernel file.
-section .multiboot
-align 4
-	dd MAGIC
-	dd FLAGS
-	dd CHECKSUM
- 
-; The multiboot standard does not define the value of the stack pointer register
-; (esp) and it is up to the kernel to provide a stack. This allocates room for a
-; small stack by creating a symbol at the bottom of it, then allocating 16384
-; bytes for it, and finally creating a symbol at the top. The stack grows
-; downwards on x86. The stack is in its own section so it can be marked nobits,
-; which means the kernel file is smaller because it does not contain an
-; uninitialized stack. The stack on x86 must be 16-byte aligned according to the
-; System V ABI standard and de-facto extensions. The compiler will assume the
-; stack is properly aligned and failure to align the stack will result in
-; undefined behavior.
-section .bss
-align 16
-stack_bottom:
-resb 16384 ; 16 KiB
-stack_top:
- 
-; The linker script specifies _start as the entry point to the kernel and the
-; bootloader will jump to this position once the kernel has been loaded. It
-; doesn't make sense to return from this function as the bootloader is gone.
-; Declare _start as a function symbol with the given symbol size.
-section .text
-global _start:function (_start.end - _start)
-_start:
-	; The bootloader has loaded us into 32-bit protected mode on a x86
-	; machine. Interrupts are disabled. Paging is disabled. The processor
-	; state is as defined in the multiboot standard. The kernel has full
-	; control of the CPU. The kernel can only make use of hardware features
-	; and any code it provides as part of itself. There's no printf
-	; function, unless the kernel provides its own <stdio.h> header and a
-	; printf implementation. There are no security restrictions, no
-	; safeguards, no debugging mechanisms, only what the kernel provides
-	; itself. It has absolute and complete power over the
-	; machine.
- 
-	; To set up a stack, we set the esp register to point to the top of our
-	; stack (as it grows downwards on x86 systems). This is necessarily done
-	; in assembly as languages such as C cannot function without a stack.
-	mov esp, stack_top
- 
-	; This is a good place to initialize crucial processor state before the
-	; high-level kernel is entered. It's best to minimize the early
-	; environment where crucial features are offline. Note that the
-	; processor isnot fully initialized yet: Features such as floating
-	; point instructions and instruction set extensions are not initialized
-	; yet. The GDT should be loaded here. Paging should be enabled here.
-	; C++ features such as global constructors and exceptions will require
-	; runtime support to work as well.
- 
-	; Enter the high-level kernel. The ABI requires the stack is 16-byte
-	; aligned at the time of the call instruction (which afterwards pushes
-	; the return pointer of size 4 bytes). The stack was originally 16-byte
-	; aligned above and we've since pushed a multiple of 16 bytes to the
-	; stack since (pushed 0 bytes so far) and the alignment is thus
-	; preserved and the call is well defined.
-        ; note, that if you are building on Windows, C functions may have "_" prefix in assembly: _kernel_main
-	extern kernel_main
-	call kernel_main
- 
-	; If the system has nothing more to do, put the computer into an
-	; infinite loop. To do that:
-	; 1) Disable interrupts with cli (clear interrupt enable in eflags).
-	;    They are already disabled by the bootloader, so this is not needed.
-	;    Mind that you might later enable interrupts and return from
-	;    kernel_main (which is sort of nonsensical to do).
-	; 2) Wait for the next interrupt to arrive with hlt (halt instruction).
-	;    Since they are disabled, this will lock up the computer.
-	; 3) Jump to the hlt instruction if it ever wakes up due to a
-	;    non-maskable interrupt occurring or due to system management mode.
-	cli
-.hang:	hlt
-	jmp .hang
-.end: 
diff --git a/src/boot.s b/src/boot.s
index a043012..385ee70 100644
--- a/src/boot.s
+++ b/src/boot.s
@@ -1,110 +1,32 @@
-/* Declare constants for the multiboot header. */
-.set ALIGN,    1<<0             /* align loaded modules on page boundaries */
-.set MEMINFO,  1<<1             /* provide memory map */
-.set FLAGS,    ALIGN | MEMINFO  /* this is the Multiboot 'flag' field */
-.set MAGIC,    0x1BADB002       /* 'magic number' lets bootloader find the header */
-.set CHECKSUM, -(MAGIC + FLAGS) /* checksum of above, to prove we are multiboot */
+.set ALIGN,    1<<0
+.set MEMINFO,  1<<1
+.set FLAGS,    ALIGN | MEMINFO
+.set MAGIC,    0x1BADB002
+.set CHECKSUM, -(MAGIC + FLAGS)
  
-/* 
-Declare a multiboot header that marks the program as a kernel. These are magic
-values that are documented in the multiboot standard. The bootloader will
-search for this signature in the first 8 KiB of the kernel file, aligned at a
-32-bit boundary. The signature is in its own section so the header can be
-forced to be within the first 8 KiB of the kernel file.
-*/
 .section .multiboot
 .align 4
 .long MAGIC
 .long FLAGS
 .long CHECKSUM
  
-/*
-The multiboot standard does not define the value of the stack pointer register
-(esp) and it is up to the kernel to provide a stack. This allocates room for a
-small stack by creating a symbol at the bottom of it, then allocating 16384
-bytes for it, and finally creating a symbol at the top. The stack grows
-downwards on x86. The stack is in its own section so it can be marked nobits,
-which means the kernel file is smaller because it does not contain an
-uninitialized stack. The stack on x86 must be 16-byte aligned according to the
-System V ABI standard and de-facto extensions. The compiler will assume the
-stack is properly aligned and failure to align the stack will result in
-undefined behavior.
-*/
 .section .bss
 .align 16
 stack_bottom:
 .skip 16384 # 16 KiB
 stack_top:
- 
-/*
-The linker script specifies _start as the entry point to the kernel and the
-bootloader will jump to this position once the kernel has been loaded. It
-doesn't make sense to return from this function as the bootloader is gone.
-*/
+
 .section .text
 .global _start
 .type _start, @function
 _start:
-	/*
-	The bootloader has loaded us into 32-bit protected mode on a x86
-	machine. Interrupts are disabled. Paging is disabled. The processor
-	state is as defined in the multiboot standard. The kernel has full
-	control of the CPU. The kernel can only make use of hardware features
-	and any code it provides as part of itself. There's no printf
-	function, unless the kernel provides its own <stdio.h> header and a
-	printf implementation. There are no security restrictions, no
-	safeguards, no debugging mechanisms, only what the kernel provides
-	itself. It has absolute and complete power over the
-	machine.
-	*/
- 
-	/*
-	To set up a stack, we set the esp register to point to the top of the
-	stack (as it grows downwards on x86 systems). This is necessarily done
-	in assembly as languages such as C cannot function without a stack.
-	*/
 	mov $stack_top, %esp
  
-	/*
-	This is a good place to initialize crucial processor state before the
-	high-level kernel is entered. It's best to minimize the early
-	environment where crucial features are offline. Note that the
-	processor is not fully initialized yet: Features such as floating
-	point instuctions and instruction set extensions are not initialized
-	yet. The GDT should be loaded here. Paging should be enabled here.
-	C++ features such as global constructors and exceptions will require
-	runtime support to work as well.
-	*/
- 
-	/*
-	Enter the high-level kernel. The ABI requires the stack is 16-byte
-	aligned at the time of the call instruction (which afterwards pushes
-	the return pointer of size 4 bytes). The stack was originally 16-byte
-	aligned above and we've pushed a multiple of 16 bytes to the
-	stack since (pushed 0 bytes so far), so the alignment has thus been
-	preserved and the call is well defined.
-	*/
 	call _init
 	call kernel_main
  
-	/*
-	If the system has nothing more to do, put the computer into an
-	infinite loop. To do that:
-	1) Disable interrupts with cli (clear interrupt enable in eflags).
-	   They are already disabled by the bootloader, so this is not needed.
-	   Mind that you might later enable interrupts and return from
-	   kernel_main (which is sort of nonsensical to do).
-	2) Wait for the next interrupt to arrive with hlt (halt instruction).
-	   Since they are disabled, this will lock up the computer.
-	3) Jump to the hlt instruction if it ever wakes up due to a
-	   non-maskable interrupt occurring or due to system management mode.
-	*/
 	cli
 1:	hlt
 	jmp 1b
  
-/*
-Set the size of the _start symbol to the current location '.' minus its start.
-This is useful when debugging or when you implement call tracing.
-*/
 .size _start, . - _start
diff --git a/src/grub.cfg b/src/grub.cfg
index b2f8404..fea5f54 100644
--- a/src/grub.cfg
+++ b/src/grub.cfg
@@ -1,3 +1,6 @@
+set timeout=0
+set default=0
+
 menuentry "myos" {
-	multiboot /boot/myos.bin
+    multiboot /boot/myos.bin
 }
diff --git a/src/kernel.c b/src/kernel.c
index 2c71ba4..90f34bd 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -1,37 +1,11 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
- 
-/* Check if the compiler thinks you are targeting the wrong operating system. */
-#if defined(__linux__)
-#error "You are not using a cross-compiler, you will most certainly run into trouble"
-#endif
- 
-/* This tutorial will only work for the 32-bit ix86 targets. */
-#if !defined(__i386__)
-#error "This tutorial needs to be compiled with a ix86-elf compiler"
-#endif
- 
-/* Hardware text mode color constants. */
-enum vga_color {
-    VGA_COLOR_BLACK = 0,
-    VGA_COLOR_BLUE = 1,
-    VGA_COLOR_GREEN = 2,
-    VGA_COLOR_CYAN = 3,
-    VGA_COLOR_RED = 4,
-    VGA_COLOR_MAGENTA = 5,
-    VGA_COLOR_BROWN = 6,
-    VGA_COLOR_LIGHT_GREY = 7,
-    VGA_COLOR_DARK_GREY = 8,
-    VGA_COLOR_LIGHT_BLUE = 9,
-    VGA_COLOR_LIGHT_GREEN = 10,
-    VGA_COLOR_LIGHT_CYAN = 11,
-    VGA_COLOR_LIGHT_RED = 12,
-    VGA_COLOR_LIGHT_MAGENTA = 13,
-    VGA_COLOR_LIGHT_BROWN = 14,
-    VGA_COLOR_WHITE = 15,
-};
- 
+#include"vga.h"
+
+static const size_t VGA_WIDTH = 80;
+static const size_t VGA_HEIGHT = 25;
+
 static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) 
 {
     return fg | bg << 4;
@@ -42,16 +16,6 @@ static inline uint16_t vga_entry(unsigned char uc, uint8_t color)
     return (uint16_t) uc | (uint16_t) color << 8;
 }
  
-size_t strlen(const char* str) 
-{
-    size_t len = 0;
-    while (str[len]) len++;
-    return len;
-}
- 
-static const size_t VGA_WIDTH = 80;
-static const size_t VGA_HEIGHT = 25;
- 
 size_t terminal_row;
 size_t terminal_column;
 uint8_t terminal_color;
@@ -63,19 +27,16 @@ void terminal_initialize(void)
     terminal_column = 0;
     terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
     terminal_buffer = (uint16_t*) 0xB8000;
-    for (size_t y = 0; y < VGA_HEIGHT; y++) {
-	for (size_t x = 0; x < VGA_WIDTH; x++) {
+    for (size_t y = 0; y < VGA_HEIGHT; y++)
+    {
+	for (size_t x = 0; x < VGA_WIDTH; x++)
+	{
 	    const size_t index = y * VGA_WIDTH + x;
 	    terminal_buffer[index] = vga_entry(' ', terminal_color);
 	}
     }
 }
  
-void terminal_setcoor(uint8_t color) 
-{
-    terminal_color = color;
-}
- 
 void terminal_putentryat(char c, uint8_t color, size_t x, size_t y) 
 {
     const size_t index = y * VGA_WIDTH + x;
@@ -84,11 +45,8 @@ void terminal_putentryat(char c, uint8_t color, size_t x, size_t y)
 
 void movescreen()
 {
-    if (terminal_row == VGA_HEIGHT)
-    {
-	terminal_row--;
-	for(size_t i=0;i<VGA_HEIGHT;i++) for(size_t j=0;j<VGA_WIDTH;j++) terminal_buffer[i*VGA_WIDTH+j]=terminal_buffer[(i+1)*VGA_WIDTH+j];
-    }
+    terminal_row--;
+    for(size_t i=0;i<VGA_HEIGHT;i++) for(size_t j=0;j<VGA_WIDTH;j++) terminal_buffer[i*VGA_WIDTH+j]=terminal_buffer[(i+1)*VGA_WIDTH+j];
 }
  
 void terminal_putchar(char c) 
@@ -102,30 +60,18 @@ void terminal_putchar(char c)
     if (terminal_row == VGA_HEIGHT) movescreen();
 }
  
-void terminal_write(const char* data, size_t size) 
-{
-    for (size_t i = 0; i < size; i++) terminal_putchar(data[i]);
-}
- 
 void terminal_writestring(const char* data) 
 {
-    terminal_write(data, strlen(data));
+    for(int i=0;data[i]!='\0';i++) terminal_putchar(data[i]);
 }
 
-char *rec;
-__attribute__ ((constructor)) void foo(void)
-{
-    rec="aleksa";
-}
- 
 void kernel_main(void) 
 {
     terminal_initialize();
 
-    for(size_t i=0;i<50;i++)
-    {
-	for(size_t j=0;j<i;j++) terminal_writestring("#");
-	terminal_writestring("Hello, kernel World!\n");
-    }
-    terminal_writestring(rec);
+   for(size_t i=0;i<50;i++)
+   {
+       for(size_t j=0;j<i;j++) terminal_writestring("#");
+       terminal_writestring("Hello, kernel World!\n");
+   }
 }
diff --git a/src/vga.h b/src/vga.h
new file mode 100644
index 0000000..8f81c21
--- /dev/null
+++ b/src/vga.h
@@ -0,0 +1,23 @@
+#ifndef VGA
+#define VGA
+
+enum vga_color {
+    VGA_COLOR_BLACK = 0,
+    VGA_COLOR_BLUE = 1,
+    VGA_COLOR_GREEN = 2,
+    VGA_COLOR_CYAN = 3,
+    VGA_COLOR_RED = 4,
+    VGA_COLOR_MAGENTA = 5,
+    VGA_COLOR_BROWN = 6,
+    VGA_COLOR_LIGHT_GREY = 7,
+    VGA_COLOR_DARK_GREY = 8,
+    VGA_COLOR_LIGHT_BLUE = 9,
+    VGA_COLOR_LIGHT_GREEN = 10,
+    VGA_COLOR_LIGHT_CYAN = 11,
+    VGA_COLOR_LIGHT_RED = 12,
+    VGA_COLOR_LIGHT_MAGENTA = 13,
+    VGA_COLOR_LIGHT_BROWN = 14,
+    VGA_COLOR_WHITE = 15,
+};
+
+#endif