From: Duje Mihanović <duje.mihanovic@skole.hr>
Date: Tue, 7 Sep 2021 20:05:14 +0000 (+0200)
Subject: Add linker script and partial VGA driver
X-Git-Tag: 0.1.0~24
X-Git-Url: http://git.dujemihanovic.xyz/%22http:/www.sics.se/static/%7B%7B%20%24.Site.BaseURL%20%7D%7Dposts/%7B%7B%20.RelPermalink%20%7D%7D?a=commitdiff_plain;h=3d58037b465f917b19b0f786c334ed70e1065857;p=nameless-os.git

Add linker script and partial VGA driver
---

diff --git a/Makefile b/Makefile
index 7001c99..c895701 100644
--- 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 de5887d..6181a73 100644
--- 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
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
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 e04b875..c0ecb80 100644
--- 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
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) }
+}