Add linker script and partial VGA driver

diff --git a/Makefile b/Makefile
index 7001c99b6359d03cd4b26c934e903e2b0079e473..c895701d2b911f6517b90be5d4b4fd8cbea6cfcb 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -2,6 +2,8 @@ AS = yasm
 LD = i686-elf-ld
 CC = i686-elf-gcc
 
+KERNEL_OBJ = kernel/entry.o kernel/arch/x86/tty/tty.o kernel/kernel.o
+
 all: boot.img
 
 boot.img: boot kernel/kernel.bin
@@ -11,16 +13,19 @@ boot.img: boot kernel/kernel.bin
 boot: boot.s
        $(AS) -f bin boot.s -o $@
 
-kernel/kernel.bin: kernel/entry.o kernel/kernel.o
-       $(LD) -o $@ -Ttext 0x1000 kernel/entry.o kernel/kernel.o --oformat=binary
+kernel/kernel.bin: ${KERNEL_OBJ}
+       $(LD) -o $@ -T kernel/linker.ld ${KERNEL_OBJ} --oformat=binary
 
 kernel/entry.o: kernel/entry.s
        $(AS) -f elf kernel/entry.s -o $@
 
+kernel/arch/x86/tty/tty.o: kernel/arch/x86/tty/tty.c
+       $(CC) -o $@ -ffreestanding -c kernel/arch/x86/tty/tty.c
+
 kernel/kernel.o: kernel/kernel.c
-       $(CC) -o $@ -ffreestanding -c kernel/kernel.c
+       $(CC) -o $@ -Iinclude/arch/x86 -ffreestanding -c kernel/kernel.c
 
 clean:
-       rm boot kernel/kernel.bin kernel/entry.o kernel/kernel.o boot.img
+       rm boot kernel/kernel.bin ${KERNEL_OBJ} boot.img
 
 .PHONY: all clean

diff --git a/boot.s b/boot.s
index de5887dddc3101695a5ddcdc7e5deeca7f1d3796..6181a73528610dcaf7c18ea6beb51dbf03865ffe 100644 (file)
--- a/boot.s
+++ b/boot.s
@@ -97,7 +97,7 @@ pmprint
 
 .loop
        mov al, [ebx] ; read next char and put it in al
-       mov ah, 0Fh ; puts the VGA text mode color white on black into ah
+       mov ah, 00000111b ; puts the VGA text mode color white on black into ah
 
        cmp al, 0 ; if the next character is null, we reached end of string
        je .done ; so return the instruction

diff --git a/include/arch/x86/tty.h b/include/arch/x86/tty.h
new file mode 100644 (file)
index 0000000..ced66d7
--- /dev/null
+++ b/include/arch/x86/tty.h
@@ -0,0 +1,5 @@
+#ifndef X86_TTY_H
+#define X86_TTY_H
+extern void screen_clear(void);
+extern void kprint(char *string);
+#endif

diff --git a/kernel/arch/x86/tty/tty.c b/kernel/arch/x86/tty/tty.c
new file mode 100644 (file)
index 0000000..6d250c5
--- /dev/null
+++ b/kernel/arch/x86/tty/tty.c
@@ -0,0 +1,49 @@
+#define VGA_WIDTH 80
+#define VGA_HEIGHT 25
+
+char *video_memory = (char *) 0xB8000; /* VGA VRAM starts at 0xB8000 */
+
+static int cursor_x = 0;
+static int cursor_y = 0;
+
+void screen_clear(void)
+{
+       int x, y;
+       for ( y = 0; y < VGA_HEIGHT; y++ ) {
+               for ( x = 0; x < VGA_WIDTH; x++ ) {
+                       video_memory[(y * VGA_WIDTH + x) * 2 + 1] = 0x07;
+                       video_memory[(y * VGA_WIDTH + x) * 2] = ' ';
+               }
+       }
+
+       cursor_x = 0;
+       cursor_y = 0;
+}
+
+void scroll_up(void)
+{
+       int x, y;
+       for ( y = 1; y < VGA_HEIGHT; y++ ) {
+               for ( x = 0; x < VGA_WIDTH; x++ ) {
+                       video_memory[((y - 1) * VGA_WIDTH + x) * 2] = video_memory[(y * VGA_WIDTH + x) * 2];
+               }
+       }
+       for ( x = 0; x < VGA_WIDTH; x++ ) {
+               video_memory[((VGA_HEIGHT - 1) * VGA_WIDTH + x) * 2] = ' ';
+       }
+       cursor_y = VGA_HEIGHT - 1;
+}
+
+void kprint(char *string)
+{
+       char next_char;
+       next_char = *string;
+
+       while ( next_char != 0 ) {
+               if ( next_char == '\n') { cursor_x = 0; cursor_y++; }
+               else { video_memory[(cursor_y * VGA_WIDTH + cursor_x++) * 2] = next_char; }
+               if ( cursor_x >= VGA_WIDTH ) { cursor_x = 0; cursor_y++; }
+               if ( cursor_y >= VGA_HEIGHT ) { scroll_up(); }
+               next_char = *++string;
+       }
+}

diff --git a/kernel/kernel.c b/kernel/kernel.c
index e04b875e2959b5963e7c6f4ba394abba1f5f0be5..c0ecb80f1ef0053e3686b2eaf53054bac433f658 100644 (file)
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -1,5 +1,14 @@
+#include <tty.h>
+
 void _start(void)
 {
-       char *video_memory = (char *) 0xB8000; /* VGA VRAM starts at 0xB8000 */
-       *video_memory = 'A'; /* put an A at the beginning of the VRAM */
+       screen_clear();
+       kprint("Hello there!\n\n\
+                       Hopefully your machine manages to print this text.\n\
+                       If it did, that's great news because I managed to write a partial VGA driver.\n\n\
+                       Right now, the short-term roadmap is as follows:\n\n\
+                           * Enable interrupts using the PIC.\n\
+                               * Write a driver for the Intel 8042 PS/2 controller so the OS can receive keystrokes.\n\
+                               * A working i8042 driver will also aid in enabling A20 Gate, which should be done ASAP so the OS can address odd (as in odd/even number) megabytes.\n\n\
+                       Feel free to mess around with the code, although I doubt it will be very interesting at the moment.\n");
 }

diff --git a/kernel/linker.ld b/kernel/linker.ld
new file mode 100644 (file)
index 0000000..d68e9f2
--- /dev/null
+++ b/kernel/linker.ld
@@ -0,0 +1,11 @@
+ENTRY(_start)
+OUTPUT_FORMAT(binary)
+
+SECTIONS
+{
+       . = 0x1000;
+
+       .text : { *(.text) }
+       .data : { *(.data) }
+       .bss : { *(.bss) }
+}