https://wiki.osdev.org/Bare_Bones + my Makefile and .gitignore

1 files changed, 114 insertions, 0 deletions

diff --git a/kernel.c b/kernel.c
new file mode 100644
index 0000000..0516f16
--- /dev/null
+++ b/kernel.c
@@ -0,0 +1,114 @@
+#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,
+};
+ 
+static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) 
+{
+	return fg | bg << 4;
+}
+ 
+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;
+uint16_t* terminal_buffer;
+ 
+void terminal_initialize(void) 
+{
+	terminal_row = 0;
+	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++) {
+			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;
+	terminal_buffer[index] = vga_entry(c, color);
+}
+ 
+void terminal_putchar(char c) 
+{
+	terminal_putentryat(c, terminal_color, terminal_column, terminal_row);
+	if (++terminal_column == VGA_WIDTH) {
+		terminal_column = 0;
+		if (++terminal_row == VGA_HEIGHT)
+			terminal_row = 0;
+	}
+}
+ 
+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));
+}
+ 
+void kernel_main(void) 
+{
+	/* Initialize terminal interface */
+	terminal_initialize();
+ 
+	/* Newline support is left as an exercise. */
+	terminal_writestring("Hello, kernel World!\n");
+}