Add logging

src/Makefile

@@ -3,12 +3,12 @@ CCPREFIX = i686-elf-
 AS = $(CCPREFIX)as
 CC = $(CCPREFIX)gcc
 
-OBJS = boot.s.o main.c.o
+OBJS = boot.s.o main.c.o logger.c.o console.c.o
 
 all: kernel
 
 clean:
-	rm kernel $(OBJS)
+	rm -f kernel $(OBJS)
 
 kernel: $(OBJS)
 	$(CC) -T linker.ld -o $@ -ffreestanding -nostdlib -O2 -lgcc $(OBJS)

src/console.c

@@ -0,0 +1,87 @@
+#include "console.h"
+
+#include "util.h"
+
+#include <stdbool.h>
+
+static const size_t VGA_WIDTH  = 80;
+static const size_t VGA_HEIGHT = 25;
+
+static size_t console_row;
+static size_t console_column;
+static uint8_t console_color;
+static uint16_t* console_buffer;
+
+static uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg);
+static uint16_t vga_entry(unsigned char uc, uint8_t color);
+static void console_putentryat(char c, uint8_t color, size_t x, size_t y);
+
+void console_initialize() {
+    console_row = 0;
+    console_column = 0;
+    console_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+    console_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;
+            console_buffer[index] = vga_entry(' ', console_color);
+        }
+    }
+}
+
+void console_print(const char *const s)
+{
+    console_write(s, strlen(s));
+}
+
+void console_putc(const char c) {
+    if (c == '\n') {
+        console_column = 0;
+
+        if (++console_row == VGA_HEIGHT) {
+            console_row = 0;
+        }
+
+        return;
+    }
+
+    console_putentryat(c, console_color, console_column, console_row);
+
+    if (++console_column == VGA_WIDTH) {
+        console_column = 0;
+
+        if (++console_row == VGA_HEIGHT) {
+            console_row = 0;
+        }
+    }
+}
+
+void console_puts(const char *const s)
+{
+    console_print(s);
+    console_putc('\n');
+}
+
+void console_setcolor(const uint8_t color) {
+    console_color = color;
+}
+
+void console_write(const char *const data, const size_t size) {
+    for (size_t i = 0; i < size; i++) {
+        console_putc(data[i]);
+    }
+}
+
+uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) {
+    return fg | bg << 4;
+}
+
+uint16_t vga_entry(unsigned char uc, uint8_t color) {
+    return (uint16_t) uc | (uint16_t) color << 8;
+}
+
+void console_putentryat(char c, uint8_t color, size_t x, size_t y) {
+    const size_t index = y * VGA_WIDTH + x;
+    console_buffer[index] = vga_entry(c, color);
+}

src/console.h

@@ -0,0 +1,35 @@
+#ifndef TAILIX_KERNEL_INCLUDED_CONSOLE
+#define TAILIX_KERNEL_INCLUDED_CONSOLE 1
+
+#include <stdint.h>
+#include <stddef.h>
+
+// 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,
+};
+
+void console_initialize();
+
+void console_print(const char *s);
+void console_putc(char c);
+void console_puts(const char *s);
+void console_setcolor(uint8_t color);
+void console_write(const char *data, size_t size);
+
+#endif

src/logger.c

@@ -0,0 +1,59 @@
+#include "logger.h"
+
+#include "console.h"
+
+void logger_initialize()
+{
+    console_initialize();
+}
+
+void logger_info(const char *const s)
+{
+    console_setcolor(VGA_COLOR_LIGHT_GREY);
+    console_putc('[');
+
+    console_setcolor(VGA_COLOR_CYAN);
+    console_print("INFO");
+
+    console_setcolor(VGA_COLOR_LIGHT_GREY);
+    console_putc(']');
+
+    console_putc(' ');
+
+    console_setcolor(VGA_COLOR_WHITE);
+    console_puts(s);
+}
+
+void logger_warn(const char *const s)
+{
+    console_setcolor(VGA_COLOR_LIGHT_GREY);
+    console_putc('[');
+
+    console_setcolor(VGA_COLOR_MAGENTA);
+    console_print("WARN");
+
+    console_setcolor(VGA_COLOR_LIGHT_GREY);
+    console_putc(']');
+
+    console_putc(' ');
+
+    console_setcolor(VGA_COLOR_WHITE);
+    console_puts(s);
+}
+
+void logger_fail(const char *const s)
+{
+    console_setcolor(VGA_COLOR_LIGHT_GREY);
+    console_putc('[');
+
+    console_setcolor(VGA_COLOR_RED);
+    console_print("FAIL");
+
+    console_setcolor(VGA_COLOR_LIGHT_GREY);
+    console_putc(']');
+
+    console_putc(' ');
+
+    console_setcolor(VGA_COLOR_WHITE);
+    console_puts(s);
+}

src/logger.h

@@ -0,0 +1,9 @@
+#ifndef TAILIX_KERNEL_INCLUDED_LOGGER
+#define TAILIX_KERNEL_INCLUDED_LOGGER 1
+
+void logger_initialize();
+void logger_info(const char *s);
+void logger_warn(const char *s);
+void logger_fail(const char *s);
+
+#endif

src/main.c

@@ -1,3 +1,9 @@
+#include "logger.h"
+
 void main()
 {
+    logger_initialize();
+    logger_info("Kernel initialization started.");
+    logger_warn("Nothing to do.");
+    logger_fail("Halt.");
 }

src/util.h

@@ -0,0 +1,20 @@
+#ifndef TAILIX_KERNEL_INCLUDED_UTIL
+#define TAILIX_KERNEL_INCLUDED_UTIL 1
+
+#include <stdint.h>
+#include <stddef.h>
+
+static inline size_t strlen(const char *s);
+
+size_t strlen(const char *const s)
+{
+    size_t len = 0;
+
+    while (s[len]) {
+        len++;
+    }
+
+    return len;
+}
+
+#endif