From da4cc8b645cd80969ce1c5b3123032b23127a904 Mon Sep 17 00:00:00 2001
From: "L. Bradley LaBoon" <me@bradleylaboon.com>
Date: Fri, 6 Dec 2013 13:47:22 -0500
Subject: [PATCH] Separated functionality into separate files. Added initial
 (untested) support for ARM.

---
 Makefile                             |  34 ++++++
 arch/arm-none-eabi/boot.s            |  33 ++++++
 arch/arm-none-eabi/linker.ld         |  42 +++++++
 {boot => arch/i586-elf}/boot.s       |   0
 linker.ld => arch/i586-elf/linker.ld |   0
 driver/video/vga.c                   |  91 +++++++++++++++
 include/brados/string.h              |   8 ++
 include/video/vga.h                  |  64 +++++++++++
 kernel/brados.c                      | 160 ++++-----------------------
 lib/string.c                         |  12 ++
 10 files changed, 308 insertions(+), 136 deletions(-)
 create mode 100644 Makefile
 create mode 100644 arch/arm-none-eabi/boot.s
 create mode 100644 arch/arm-none-eabi/linker.ld
 rename {boot => arch/i586-elf}/boot.s (100%)
 rename linker.ld => arch/i586-elf/linker.ld (100%)
 create mode 100644 driver/video/vga.c
 create mode 100644 include/brados/string.h
 create mode 100644 include/video/vga.h
 create mode 100644 lib/string.c

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..f6d0d8c
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,34 @@
+# Build environment
+PREFIX	?= /home/brad/brados/brados-gcc
+ARCH	?= i586-elf
+GNU	?= $(PREFIX)/$(ARCH)/bin/$(ARCH)
+
+# Source files
+SOURCES_ASM	:= arch/$(ARCH)/boot.s
+SOURCES_C	:= driver/video/vga.c kernel/brados.c lib/string.c
+
+# Object files
+OBJS	:= $(patsubst %.s,%.o,$(SOURCES_ASM))
+OBJS	+= $(patsubst %.c,%.o,$(SOURCES_C))
+
+# Build flags
+CFLAGS = -std=gnu99 -ffreestanding -Iinclude/ -O2 -Wall -Wextra
+LDFLAGS = -ffreestanding -O2 -nostdlib -lgcc
+
+# Build rules
+all: brados.bin
+.PHONY: all clean
+
+brados.bin: $(OBJS) arch/$(ARCH)/linker.ld
+	$(GNU)-gcc -T arch/$(ARCH)/linker.ld -o $@ $(LDFLAGS) $(OBJS)
+
+clean:
+	rm -f $(OBJS) brados.bin
+
+# C
+%.o: %.c Makefile
+	$(GNU)-gcc -c $< -o $@ $(CFLAGS)
+
+# Assembly
+%.o: %.s Makefile
+	$(GNU)-as $< -o $@
diff --git a/arch/arm-none-eabi/boot.s b/arch/arm-none-eabi/boot.s
new file mode 100644
index 0000000..27438f4
--- /dev/null
+++ b/arch/arm-none-eabi/boot.s
@@ -0,0 +1,33 @@
+.section ".text.boot"
+
+.globl Start
+Start:
+	// Setup the stack
+	mov	sp, #0x8000
+	
+	// Clear out bss
+	ldr	r4, =_bss_start
+	ldr	r9, =_bss_end
+	mov	r5, #0
+	mov	r6, #0
+	mov	r7, #0
+	mov	r8, #0
+	b	2f
+
+1:
+	// Store multiple at r4
+	stmia	r4!, {r5-r8}
+
+2:
+	// If we are still below bss_end, loop
+	cmp	r4, r9
+	blo	1b
+	
+	// Call brados_main
+	ldr	r3, =brados_main
+	blx	r3
+
+halt:
+	// Halt
+	wfe
+	b	halt
diff --git a/arch/arm-none-eabi/linker.ld b/arch/arm-none-eabi/linker.ld
new file mode 100644
index 0000000..af831ea
--- /dev/null
+++ b/arch/arm-none-eabi/linker.ld
@@ -0,0 +1,42 @@
+ENTRY(Start)
+
+SECTIONS
+{
+	/* Starts at LOADER_ADDR */
+	. = 0x8000
+	_start = .;
+	_text_start = .;
+	.text:
+	{
+		KEEP(*(.text.boot))
+		*(.text)
+	}
+	. = ALIGN(4096);
+	_text_end = .;
+	
+	_rodata_start = .;
+	.rodata:
+	{
+		*(.rodata)
+	}
+	. = ALIGN(4096)
+	_rodata_end = .;
+	
+	_data_start = .;
+	.data:
+	{
+		*(.data)
+	}
+	. = ALIGN(4096);
+	_data_end = .;
+	
+	_bss_start = .;
+	.bss:
+	{
+		bss = .;
+		*(.bss)
+	}
+	. = ALIGN(4096)
+	_bss_end = .;
+	_end = .;
+}
diff --git a/boot/boot.s b/arch/i586-elf/boot.s
similarity index 100%
rename from boot/boot.s
rename to arch/i586-elf/boot.s
diff --git a/linker.ld b/arch/i586-elf/linker.ld
similarity index 100%
rename from linker.ld
rename to arch/i586-elf/linker.ld
diff --git a/driver/video/vga.c b/driver/video/vga.c
new file mode 100644
index 0000000..832c450
--- /dev/null
+++ b/driver/video/vga.c
@@ -0,0 +1,91 @@
+#include <stddef.h>
+#include <stdint.h>
+
+#include <brados/string.h>
+#include <video/vga.h>
+
+// Create a VGA color
+uint8_t make_color(enum vga_color fg, enum vga_color bg)
+{
+	return fg | bg << 4;
+}
+
+// Create a VGA character
+uint16_t make_vgaEntry(char c, uint8_t color)
+{
+	uint16_t c16 = c;
+	uint16_t color16 = color;
+	return c16 | color16 << 8;
+}
+
+// Initialize a VGA term
+void term_init(struct vgastate *state)
+{
+	state->term_row = state->term_col = 0;
+	state->term_color = make_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+	state->term_buf = (uint16_t *) VGA_BUF;
+	
+	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;
+			state->term_buf[index] = make_vgaEntry(' ', state->term_color);
+		}
+	}
+}
+
+// Write a character to a VGA term
+void term_putChar(struct vgastate *state, char c)
+{
+	if (c == '\n')
+		state->term_col = VGA_WIDTH - 1;
+	else
+		term_putEntryAt(state, c, state->term_color, state->term_col, state->term_row);
+	
+	if (++state->term_col == VGA_WIDTH) {
+		state->term_col = 0;
+		if (++state->term_row == VGA_HEIGHT) {
+			state->term_row--;
+			term_scroll(state);
+		}
+	}
+}
+
+// Place a character in a VGA term's buffer
+void term_putEntryAt(struct vgastate *state, char c, uint8_t color, size_t x, size_t y)
+{
+	const size_t index = y * VGA_WIDTH + x;
+	state->term_buf[index] = make_vgaEntry(c, color);
+}
+
+// Scroll the term down 1 line
+void term_scroll(struct vgastate *state)
+{
+	// Move each row up
+	for (size_t y = 1; y < VGA_HEIGHT; y++) {
+		for (size_t x = 0; x < VGA_WIDTH; x++) {
+			const size_t index = y * VGA_WIDTH + x;
+			const size_t indexBelow = (y - 1) * VGA_WIDTH + x;
+			state->term_buf[indexBelow] = state->term_buf[index];
+		}
+	}
+	
+	// Clear the last line
+	for (size_t x = 0; x < VGA_WIDTH; x++) {
+		const size_t index = (VGA_HEIGHT - 1) * VGA_WIDTH + x;
+		state->term_buf[index] = ' ';
+	}
+}
+
+// Set VGA term color
+void term_setColor(struct vgastate *state, uint8_t color)
+{
+	state->term_color = color;
+}
+
+// Write a string to a VGA term
+void term_writeStr(struct vgastate *state, const char *data)
+{
+	size_t dataLen = strlen(data);
+	for (size_t i = 0; i < dataLen; i++)
+		term_putChar(state, data[i]);
+}
diff --git a/include/brados/string.h b/include/brados/string.h
new file mode 100644
index 0000000..7d33d5d
--- /dev/null
+++ b/include/brados/string.h
@@ -0,0 +1,8 @@
+#ifndef __brados_string_h__
+#define __brados_string_h__
+
+#include <stddef.h>
+
+size_t strlen(const char *str);
+
+#endif
diff --git a/include/video/vga.h b/include/video/vga.h
new file mode 100644
index 0000000..c098420
--- /dev/null
+++ b/include/video/vga.h
@@ -0,0 +1,64 @@
+#ifndef __brados_video_vga_h__
+#define __brados_video_vga_h__
+
+#include <stddef.h>
+#include <stdint.h>
+
+#define VGA_BUF 0xB8000
+
+#define VGA_WIDTH	80
+#define VGA_HEIGHT	24
+
+// VGA State
+struct vgastate {
+	size_t term_row, term_col;
+	uint8_t term_color;
+	uint16_t *term_buf;
+};
+
+// 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
+};
+
+// Create a VGA color
+uint8_t make_color(enum vga_color fg, enum vga_color bg);
+
+// Create a VGA character
+uint16_t make_vgaEntry(char c, uint8_t color);
+
+// Initialize a VGA term
+void term_init(struct vgastate *state);
+
+// Write a character to a VGA term
+void term_putChar(struct vgastate *state, char c);
+
+// Place a character in a VGA term's buffer
+void term_putEntryAt(struct vgastate *state, char c, uint8_t color, size_t x, size_t y);
+
+// Scroll the term down 1 line
+void term_scroll(struct vgastate *state);
+
+// Set VGA term color
+void term_setColor(struct vgastate *state, uint8_t color);
+
+// Write a string to a VGA term
+void term_writeStr(struct vgastate *state, const char *data);
+
+#endif
diff --git a/kernel/brados.c b/kernel/brados.c
index 965bab6..fae4da5 100644
--- a/kernel/brados.c
+++ b/kernel/brados.c
@@ -1,156 +1,44 @@
 #include <stddef.h>
-#include <stdint.h>
+
+#include <brados/string.h>
+#include <video/vga.h>
 
 // Make sure we are using the right compiler
 #if defined(__linux__)
 #error "You are using the wrong compiler."
 #endif
 
-// Color constants
-enum vga_color
+// Test various VGA functionality
+void vgaTests(struct vgastate *term)
 {
-	COLOR_BLACK = 0,
-	COLOR_BLUE = 1,
-	COLOR_GREEN = 2,
-	COLOR_CYAN = 3,
-	COLOR_RED = 4,
-	COLOR_MAGENTA = 5,
-	COLOR_BROWN = 6,
-	COLOR_LIGHT_GREY = 7,
-	COLOR_DARK_GREY = 8,
-	COLOR_LIGHT_BLUE = 9,
-	COLOR_LIGHT_GREEN = 10,
-	COLOR_LIGHT_CYAN = 11,
-	COLOR_LIGHT_RED = 12,
-	COLOR_LIGHT_MAGENTA = 13,
-	COLOR_LIGHT_BROWN = 14,
-	COLOR_WHITE = 15
-};
-
-// Create a VGA color
-uint8_t make_color(enum vga_color fg, enum vga_color bg)
-{
-	return fg | bg << 4;
-}
-
-// Create a VGA character
-uint16_t make_vgaEntry(char c, uint8_t color)
-{
-	uint16_t c16 = c;
-	uint16_t color16 = color;
-	return c16 | color16 << 8;
-}
-
-// Calculate the length of a string
-size_t strlen(const char *str)
-{
-	size_t len = 0;
-	while (str[len] != 0)
-		len++;
-	return len;
-}
-
-static const size_t VGA_WIDTH = 80;
-static const size_t VGA_HEIGHT = 24;
-
-size_t term_row, term_col;
-uint8_t term_color;
-uint16_t *term_buf;
-
-// Initialize the terminal
-void term_init()
-{
-	term_row = term_col = 0;
-	term_color = make_color(COLOR_LIGHT_GREY, COLOR_BLACK);
-	term_buf = (uint16_t *) 0xB8000;
+	// Test line wrapping
+	term_writeStr(term, "Welcome to the desert of the real. I thought what I'd do was I'd pretend I was one of those deaf mutes.\n\n");
 	
-	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;
-			term_buf[index] = make_vgaEntry(' ', term_color);
-		}
-	}
-}
-
-// Set the terminal color
-void term_setColor(uint8_t color)
-{
-	term_color = color;
-}
-
-// Place a character in the buffer
-void term_putEntryAt(char c, uint8_t color, size_t x, size_t y)
-{
-	const size_t index = y * VGA_WIDTH + x;
-	term_buf[index] = make_vgaEntry(c, color);
-}
-
-// Scroll down 1 line
-void term_scroll()
-{
-	for (size_t y = 1; y < VGA_HEIGHT; y++) {
-		for (size_t x = 0; x < VGA_WIDTH; x++) {
-			const size_t index = y * VGA_WIDTH + x;
-			const size_t indexBelow = (y - 1) * VGA_WIDTH + x;
-			term_buf[indexBelow] = term_buf[index];
-		}
-	}
+	// Test colors
+	term_setColor(term, make_color(VGA_COLOR_BLACK, VGA_COLOR_WHITE));
+	term_writeStr(term, "This text should be inverse.\n");
+	term_setColor(term, make_color(VGA_COLOR_LIGHT_BLUE, VGA_COLOR_GREEN));
+	term_writeStr(term, "This text should be colorful.\n\n");
 	
-	for (size_t x = 0; x < VGA_WIDTH; x++) {
-		const size_t index = (VGA_HEIGHT - 1) * VGA_WIDTH + x;
-		term_buf[index] = ' ';
+	// Test scrolling
+	term_setColor(term, make_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK));
+	for (size_t i = 0; i < 20; i++) {
+		term_writeStr(term, "Printing some lines.\n");
+		for (volatile size_t j = 0; j < 100000000; j++);
 	}
 }
 
-// Write a character to the terminal
-void term_putChar(char c)
-{
-	if (c == '\n')
-		term_col = VGA_WIDTH - 1;
-	else
-		term_putEntryAt(c, term_color, term_col, term_row);
-	
-	if (++term_col == VGA_WIDTH) {
-		term_col = 0;
-		if (++term_row == VGA_HEIGHT) {
-			term_row--;
-			term_scroll();
-		}
-	}
-}
-
-// Write a string to the terminal
-void term_writeStr(const char *data)
-{
-	size_t dataLen = strlen(data);
-	for (size_t i = 0; i < dataLen; i++)
-		term_putChar(data[i]);
-}
-
 // Main kernel function
 void brados_main()
 {
-	term_init();
+	struct vgastate term;
+	term_init(&term);
 	
-	// Test printing and newlines
-	term_writeStr("Welcome to BRaDOS!\n");
-	term_writeStr("written by L. Bradley LaBoon\n\n");
+	// Welcome message
+	term_writeStr(&term, "Welcome to BRaDOS!\n");
+	term_writeStr(&term, "written by L. Bradley LaBoon\n\n");
 	
-	// Test line wrapping
-	term_writeStr("The Laughing Man always says: 'I thought what I'd do was I'd pretend I was one of those deaf mutes.'\n\n");
+	vgaTests(&term);
 	
-	// Test colors
-	term_setColor(make_color(COLOR_BLACK, COLOR_WHITE));
-	term_writeStr("This text should be inverse.\n");
-	term_setColor(make_color(COLOR_LIGHT_BLUE, COLOR_GREEN));
-	term_writeStr("This text should be colorful.\n\n");
-	
-	// Test scrolling
-	term_setColor(make_color(COLOR_LIGHT_GREY, COLOR_BLACK));
-	for (size_t i = 0; i < 20; i++) {
-		term_writeStr("Printing some lines.\n");
-		for (size_t j = 0; j < 100000000; j++);
-	}
-	
-	term_writeStr("Done.");
+	term_writeStr(&term, "Done.");
 }
diff --git a/lib/string.c b/lib/string.c
new file mode 100644
index 0000000..6bee2d4
--- /dev/null
+++ b/lib/string.c
@@ -0,0 +1,12 @@
+#include <stddef.h>
+
+#include <brados/string.h>
+
+// Find the length of a string
+size_t strlen(const char *str)
+{
+	size_t len = 0;
+	while (str[len] != 0)
+		len++;
+	return len;
+}