Cleanup and documentation

kernel/Makefile

@@ -2,8 +2,8 @@
 SOURCES_S := boot.s boot64.s
 OBJECTS_S := $(patsubst %.s, $(BUILD_DIR)/kernel/%.o, $(SOURCES_S))
 
-SOURCES_C := kernel.c
-HEADERS_C := multiboot.h psf.h
+SOURCES_C := kernel.c kprintf.c console.c
+HEADERS_C := multiboot.h psf.h kprintf.h console.h
 OBJECTS_C := $(patsubst %.c, $(BUILD_DIR)/kernel/%.o, $(SOURCES_C))
 
 LINKER_LD := linker.ld

kernel/boot.s

@@ -92,8 +92,6 @@ page_table_l3:
 .skip 4096
 page_table_l2:
 .skip 4096
-page_table_l3_framebuffer:
-.skip 4096
 page_table_l2_framebuffer:
 .skip 4096
 stack_bottom:
@@ -106,11 +104,6 @@ gdt64:
 .quad GDT_ZERO_ENTRY
 .set gdt64_code_segment, . - gdt64
 .quad GDT_FLAGS
-/*
-gdt64_data_entry:
-.set gdt64_data_segment, gdt64_data_entry - gdt64
-.quad (1<<44) | (1<<46) | (1<<41)
-*/
 gdt64_pointer:
 .word . - gdt64 - 1
 .quad gdt64

kernel/boot64.s

@@ -12,7 +12,6 @@ long_mode_start:
   movw %ax, %gs
 
   /* We should keep the pointer to mb, debug needed */
-  push %rbx /* Multiboot struct pointer */
   mov %rbx, %rdi
   call kernel_main
   hlt

kernel/console.c

@@ -0,0 +1,140 @@
+#include "console.h"
+#include "psf.h"
+#include <stdint.h>
+
+/* graphics framebuffer */
+char *fb;
+/* number of bytes in each line */
+int scanline;
+
+uint32_t console_y;
+uint32_t console_x;
+
+uint32_t console_rows;
+uint32_t console_cols;
+
+multiboot_info_t *mbi;
+
+psf_font_t *font;
+
+/*
+ * We write a character on the screen using the psf font.
+ * This function is not meant for external usage as it does not
+ * handle line breaking, scrolling, and special characters such
+ * as linefeed.
+ */
+void putchar (uint16_t c, int32_t cx, int32_t cy, uint32_t fg, uint32_t bg)
+{
+  uint32_t bytesperline = (font->width + 7) / 8;
+
+  unsigned char *glyph = (unsigned char *)font + font->headersize +
+    (c > 0 && c < font->numglyphs ? c : 0) * font->bytesperglyph;
+
+  uint32_t offs = (cy * font->height * scanline) + (cx * (font->width) * sizeof (PIXEL));
+
+  uint32_t x, y, line, mask;
+  for (y = 0; y < font->height; y++) {
+    line = offs;
+    mask = 1 << (font->width -1);
+    for (x = 0; x < font->width; x++) {
+      *((PIXEL *)(fb+line)) = *((uint32_t *)glyph) & mask ? fg : bg;
+      mask >>= 1;
+      line += sizeof (PIXEL);
+    }
+    glyph += bytesperline;
+    offs += scanline;
+  }
+
+}
+
+void set_pixel(uint64_t x, uint64_t y, PIXEL color)
+{
+  uint32_t pos = (y * sizeof (PIXEL) * mbi->framebuffer_width) + (x * sizeof (PIXEL));
+  *((PIXEL *)(fb+pos)) = color;
+}
+
+PIXEL get_pixel(uint64_t x, uint64_t y)
+{
+  uint32_t pos = (y * sizeof (PIXEL) * mbi->framebuffer_width) + (x * sizeof (PIXEL));
+  return *((PIXEL *)(fb+pos));
+}
+
+/*
+ * Move all characters one row above.
+ */
+void console_scroll()
+{
+  const uint32_t width = mbi->framebuffer_width;
+  const uint32_t font_height = font->height;
+
+  /* Move each row to the previous one */
+  for (uint32_t row = 1; row < console_rows; row++) {
+    for (uint32_t y = 0; y < font_height; y++ ) {
+      for (uint32_t x = 0; x < width; x++ ) {
+        PIXEL p = get_pixel(x, (row * font_height) + y);
+        set_pixel(x, ((row - 1) * font_height) + y, p);
+      }
+    }
+  }
+
+  /* Reset bottom row*/
+  for (uint32_t y = 0; y < font_height; y++ ) {
+    for (uint32_t x = 0; x < width; x++ ) {
+      set_pixel(x, ((console_rows - 1) * font_height) + y, CONSOLE_BG);
+    }
+  }
+}
+
+/*
+ * Write a single character the console.
+ * The console is a share resource, a syncing mechanism must be used.
+ * The console scrolling and line wrapping is handled.
+ */
+void console_puts(uint16_t ch)
+{
+  if (ch == '\n') {
+    console_x = 0;
+    console_y++;
+    return;
+  }
+
+  if (console_x >= console_cols) {
+    console_x = 0;
+    console_y++;
+  }
+
+  if (console_y >= console_rows)
+    console_scroll();
+
+  putchar((uint16_t) ch, console_x, console_y, CONSOLE_FG, CONSOLE_BG);
+  console_x++;
+}
+
+/*
+ * Write a character array to the console.
+ * The console is a share resource, a syncing mechanism must be used.
+ */
+void console_write(char *str)
+{
+  for (int idx = 0; str[idx] != '\0'; idx++ ) {
+    console_puts(str[idx]);
+  }
+}
+
+/*
+ * Initialize the console.
+ */
+void console_init(multiboot_info_t *multiboot_struct)
+{
+  mbi = multiboot_struct;
+  fb = (char *)mbi->framebuffer_addr;
+  scanline = mbi->framebuffer_pitch;
+
+  font = (psf_font_t *)&consolefonts_binary__start;
+
+  console_rows = mbi->framebuffer_height / font->height;
+  console_cols = mbi->framebuffer_width / font->width;
+
+  console_x = 0;
+  console_y = 0;
+}

kernel/console.h

@@ -0,0 +1,17 @@
+#include "multiboot.h"
+
+#ifndef CONSOLE_HEADER
+#define CONSOLE_HEADER 1
+
+#define PIXEL uint32_t
+
+#define CONSOLE_BG 0
+#define CONSOLE_FG 0xFFFFFFFF
+
+void console_init(multiboot_info_t *mbi);
+
+void console_write(char *str);
+
+void console_puts(uint16_t ch);
+
+#endif

kernel/kernel.c

@@ -1,7 +1,6 @@
 #include "multiboot.h"
-#include "psf.h"
-#include <stdint.h>
-#include <stdarg.h>
+#include "console.h"
+#include "kprintf.h"
 
 #if defined (__linux__)
 #error "You are not using a cross-compiler, you will most certainly run into trouble"
@@ -11,172 +10,8 @@
 #error "The kernel needs to be compiled with a x86_64-elf compiler"
 #endif
 
-/* graphics framebuffer */
-char *fb;
-/* number of bytes in each line */
-int scanline;
-/* extern the symbols in the psf object */
-extern char consolefonts_binary__start;
-extern char consolefonts_binary__end;
-
-multiboot_info_t *mbi;
-uint32_t console_y;
-uint32_t console_x;
-
-uint32_t console_max_y;
-uint32_t console_max_x;
-
-#define PIXEL uint32_t
-
-#define CONSOLE_BG 0
-#define CONSOLE_FG 0xFFFFFFFF
-
-void putchar (uint16_t c, int32_t cx, int32_t cy, uint32_t fg, uint32_t bg)
+void kernel_main (multiboot_info_t *multiboot_struct_addr)
 {
-  psf_font_t *font = (psf_font_t *)&consolefonts_binary__start;
-  uint32_t bytesperline = (font->width + 7) / 8;
-
-  unsigned char *glyph = (unsigned char *)&consolefonts_binary__start + font->headersize +
-    (c > 0 && c < font->numglyphs ? c : 0) * font->bytesperglyph;
-
-  uint32_t offs = (cy * font->height * scanline) + (cx * (font->width) * sizeof (PIXEL));
-
-  uint32_t x, y, line, mask;
-  for (y = 0; y < font->height; y++) {
-    line = offs;
-    mask = 1 << (font->width -1);
-    for (x = 0; x < font->width; x++) {
-      *((PIXEL *)(fb+line)) = *((uint32_t *)glyph) & mask ? fg : bg;
-      mask >>= 1;
-      line += sizeof (PIXEL);
-    }
-    glyph += bytesperline;
-    offs += scanline;
-  }
-
-}
-
-void console_push()
-{
-  // TODO: implement console pushing
-}
-
-void console_puts(uint16_t ch)
-{
-  if (ch == '\n') {
-    console_x = 0;
-    console_y++;
-    return;
-  }
-
-  if (console_x >= console_max_x) {
-    console_x = 0;
-    console_y++;
-  }
-
-  if (console_y > console_max_y)
-    console_push();
-
-  putchar((uint16_t) ch, console_x, console_y, CONSOLE_FG, CONSOLE_BG);
-  console_x++;
-}
-
-void console_write(char *str)
-{
-  for (int idx = 0; str[idx] != '\0'; idx++ ) {
-    console_puts(str[idx]);
-  }
-}
-
-void console_init(multiboot_info_t *mbi)
-{
-  psf_font_t *font = (psf_font_t *)&consolefonts_binary__start;
-
-  console_max_y = mbi->framebuffer_height / font->height - 1;
-  console_max_x = mbi->framebuffer_width / font->width - 1;
-
-  console_x = 0;
-  console_y = 0;
-}
-
-void convert(int num, int base, char *buf, int bufsize)
-{
-  int idx = 0;
-  buf[idx] = '\0';
-
-  do {
-    /* Avoid buffer overrun */
-    if (idx == bufsize - 1)
-      break;
-
-    int remainder = num % base;
-
-    if (remainder > 9)
-      buf[idx] = remainder - 10 + 'A';
-    else
-      buf[idx] = remainder + '0';
-
-    num /= base;
-    idx++;
-  } while(num != 0);
-
-  buf[idx] = '\0';
-
-  for (int i = 0; i < idx / 2; i++) {
-    int tmp = buf[i];
-    buf[i] = buf[idx-1-i];
-    buf[idx-1-i] = tmp;
-  }
-}
-
-void kprintf(char *format, ...)
-{
-  va_list arg;
-  va_start(arg, format);
-
-  char buffer[50];
-  int i;
-
-  for (int idx = 0; format[idx] != '\0'; idx++) {
-    while (format[idx] != '%') {
-
-      /* Never overrun the buffer */
-      if (format[idx] == '\0')
-        return;
-
-      console_puts(format[idx]);
-      idx++;
-    }
-    idx++;
-    switch (format[idx]) {
-      case 'd':
-        i = va_arg(arg, int);
-        if (i < 0) {
-          i = -i;
-          console_puts('-');
-        }
-
-        convert(i, 10, buffer, 50);
-        console_write(buffer);
-        break;
-      case 'X':
-        i = va_arg(arg, int);
-
-        convert(i, 16, buffer, 50);
-        console_write(buffer);
-        break;
-    }
-  }
-
-  va_end(arg);
-}
-
-void kernel_main (uint32_t multiboot_struct_addr)
-{
-  mbi = (multiboot_info_t *)multiboot_struct_addr;
-  fb = (char *)mbi->framebuffer_addr;
-  scanline = mbi->framebuffer_pitch;
-
-  console_init(mbi);
-  kprintf("Console width is %d\n", mbi->framebuffer_width);
+  console_init(multiboot_struct_addr);
+  kprintf("Hello World");
 }

kernel/kprintf.c

@@ -0,0 +1,82 @@
+#include "console.h"
+#include "kprintf.h"
+#include <stdarg.h>
+#include <stdint.h>
+
+/*
+ * Converts a decimal number to a different base.
+ */
+void convert(uint64_t num, int base, char *buf, int bufsize)
+{
+  int idx = 0;
+  buf[idx] = '\0';
+
+  do {
+    /* Avoid buffer overrun */
+    if (idx == bufsize - 1)
+      break;
+
+    int remainder = num % base;
+
+    if (remainder > 9)
+      buf[idx] = remainder - 10 + 'A';
+    else
+      buf[idx] = remainder + '0';
+
+    num /= base;
+    idx++;
+  } while(num != 0);
+
+  buf[idx] = '\0';
+
+  for (int i = 0; i < idx / 2; i++) {
+    int tmp = buf[i];
+    buf[i] = buf[idx-1-i];
+    buf[idx-1-i] = tmp;
+  }
+}
+
+/*
+ * Print formatted string.
+ */
+void kprintf(char *format, ...)
+{
+  va_list arg;
+  va_start(arg, format);
+
+  char buffer[50];
+  long i;
+
+  for (int idx = 0; format[idx] != '\0'; idx++) {
+    while (format[idx] != '%') {
+
+      /* Never overrun the buffer */
+      if (format[idx] == '\0')
+        return;
+
+      console_puts(format[idx]);
+      idx++;
+    }
+    idx++;
+    switch (format[idx]) {
+      case 'd':
+        i = va_arg(arg, long);
+        if (i < 0) {
+          i = -i;
+          console_puts('-');
+        }
+
+        convert(i, 10, buffer, 50);
+        console_write(buffer);
+        break;
+      case 'X':
+        i = va_arg(arg, long);
+
+        convert(i, 16, buffer, 50);
+        console_write(buffer);
+        break;
+    }
+  }
+
+  va_end(arg);
+}

kernel/kprintf.h

@@ -0,0 +1,6 @@
+#ifndef KPRINTF_HEADER
+#define KPRINTF_HEADER 1
+
+void kprintf(char *format, ...);
+
+#endif

kernel/psf.h

@@ -5,6 +5,10 @@
 
 #define PSF_FONT_MAGIC 0x864ab572
 
+/* extern the symbols in the psf object */
+extern char consolefonts_binary__start;
+extern char consolefonts_binary__end;
+
 struct psf_font {
   uint32_t magic;         /* magic bytes to identify psf */
   uint32_t version;       /* zero */