11 files changed, 295 insertions, 0 deletions
diff --git a/kernel/Makefile b/kernel/Makefile
new file mode 100644
index 0000000..0f3ac41
--- /dev/null
+++ b/kernel/Makefile
@@ -0,0 +1,33 @@
+TARGET = kernel
+
+SRCS = $(wildcard *.c)
+ASMS = $(wildcard *.s)
+OBJS = $(SRCS:.c=.o) $(ASMS:.s=.o)
+
+CFLAGS = -m32 -I../include -ffreestanding -nostdinc -nostdlib -fno-stack-protector -gstabs+
+LDFLAGS = -m elf_i386 -Tlink.ld
+ASMFLAGS = -f elf32
+
+CC = gcc $(CFLAGS)
+LD = ld $(LDFLAGS)
+ASM = nasm $(ASMFLAGS)
+
+all: build
+
+build: $(TARGET)
+
+.s.o:
+	$(ASM) -o $*.o $^
+
+.c.o:
+	$(CC) -c -o $*.o $^
+
+$(TARGET): $(OBJS)
+	$(LD) -o $(TARGET) $(OBJS)
+
+clean:
+	rm -f $(OBJS)
+	rm -f $(TARGET)
+
+run: $(TARGET)
+	qemu-system-x86_64 -s -kernel $(TARGET)
diff --git a/kernel/boot.o b/kernel/boot.o
new file mode 100644
index 0000000..41427be
--- /dev/null
+++ b/kernel/boot.o
diff --git a/kernel/boot.s b/kernel/boot.s
new file mode 100644
index 0000000..be68109
--- /dev/null
+++ b/kernel/boot.s
@@ -0,0 +1,127 @@
+global kboot
+extern kmain
+
+; Multiboot header
+section .mboothdr
+mboot_hdr:
+  align 4
+  dd 0x1BADB002
+  dd 0x00
+  dd - (0x1BADB002 + 0x00)
+
+section .text
+
+kboot:
+  cli
+  call flush_gdt
+  call flush_idt
+  call kmain
+  cli
+  hlt
+
+gdt:
+  ; null descriptor
+  dq 0
+  ; kernel code segment
+  dw 0xFFFF ; limit (bits 0-15)
+  dw 0x0000 ; base (bits 0-15)
+  db 0x00   ; base (bits 16-23)
+  db 0x9A   ; access byte
+  db 0xCF   ; flags / limit (bits 16-19)
+  db 0x00   ; base (bits 24-31)
+  ; kernel data segment
+  dw 0xFFFF
+  dw 0x0000
+  db 0x00
+  db 0x92
+  db 0xCF
+  db 0x00
+  ; userspace code segment
+  dw 0xFFFF
+  dw 0x0000
+  db 0x00
+  db 0xFA
+  db 0xCF
+  db 0x00
+  ; userspace data segment
+  dw 0xFFFF
+  dw 0x0000
+  db 0x00
+  db 0xF2
+  db 0xCF
+  db 0x00
+
+gdtp:
+  dw ($-gdt-1)
+  dd gdt
+
+flush_gdt:
+  push ebp
+  mov ebp, esp
+  lgdt [gdtp]
+  mov ax, 0x10
+  mov ds, ax
+  mov es, ax
+  mov fs, ax
+  mov gs, ax
+  mov ss, ax
+  jmp 0x08:.end
+.end:
+  pop ebp
+  ret
+
+idt:
+  times (256*8) db 0
+
+idtp:
+  dw ($-idt-1)
+  dd idt
+
+int_handler:
+  iret
+
+flush_idt:
+  push ebp
+  mov ebp, esp
+  mov ecx, 256
+  mov edx, idt
+.loop:
+  mov eax, int_handler
+  mov [edx], ax
+  mov word [edx+2], 0x08
+  mov byte [edx+4], 0
+  mov byte [edx+5], 0x8E
+  shr eax, 16
+  mov [edx+6], ax
+  add edx, 8
+  dec ecx
+  jz .end
+  jmp .loop
+.end:
+  lidt [idtp]
+  call pic_init
+  sti
+  pop ebp
+  ret
+
+pic_init:
+  push ebp
+  mov ebp, esp
+  mov al, 0x11
+  out 0x20, al
+  out 0xA0, al
+  mov al, 0x20
+  out 0x21, al
+  out 0xA1, al
+  mov al, 0x04
+  out 0x21, al
+  mov al, 0x02
+  out 0xA1, al
+  mov al, 0x01
+  out 0x21, al
+  out 0xA1, al
+  mov al, 0xFF
+  out 0x21, al
+  out 0xA1, al
+  pop ebp
+  ret
diff --git a/kernel/con.c b/kernel/con.c
new file mode 100644
index 0000000..b3d2b9d
--- /dev/null
+++ b/kernel/con.c
@@ -0,0 +1,96 @@
+/*
+ * con.c
+ *
+ * Basic VGA text console
+ */
+
+#include <asm/io.h>
+#include <kernel/vsprintf.h>
+#include <stdarg.h>
+#include <stdint.h>
+
+#define COLS 80
+#define ROWS 25
+
+static uint8_t *vram = (uint8_t*) 0xB8000;
+static int pos;
+
+static inline void cursorpos(int pos) {
+	outb(0x3D4, 0x0E);
+	outb(0x3D5, (uint8_t) ((pos >> 9) & 0xFF));
+  outb(0x3D4, 0x0F);
+	outb(0x3D5, (uint8_t) ((pos >> 1) & 0xFF));
+}
+
+/* scrolls the console up one line */
+static void scroll_up(void) {
+  int n = (COLS * (ROWS - 1)) << 1;
+  uint8_t *p = vram;
+
+  while(n--) {
+    *p = p[COLS << 1];
+    p++;
+  }
+
+  p = (uint8_t*) (vram + (COLS * (ROWS - 1) << 1));
+  n = COLS;
+  while(n--) {
+    *p = ' ';
+    p += 2;
+  }
+
+  pos -= COLS << 1;
+  cursorpos(pos);
+}
+
+/* must be called before any console output */
+void con_init(void) {
+  int n = COLS * ROWS;
+  uint8_t *p = vram;
+
+  while(n--) {
+    *(p++) = 0x20;
+    *(p++) = 0x07;
+  }
+
+  pos = 0;
+  cursorpos(0);
+}
+
+/* write a zero-terminated string to console */
+void con_print(char *s) {
+  uint8_t *p = &vram[pos];
+
+  while(*s) {
+    if(*s == '\n') {
+      pos = (int) (p - vram);
+      pos = ((pos / (COLS << 1)) + 1) * (COLS << 1);
+      p = &vram[pos];
+      s++;
+    } else {
+      *p = *(s++);
+      p += 2;
+    }
+
+    pos = (int) (p - vram);
+
+    if(pos >= (COLS * ROWS) << 1)
+      scroll_up();
+  }
+
+  /* update the cursor position */
+  cursorpos(pos);
+}
+
+int printf(char *fmt, ...) {
+  int ret;
+  char buf[1024];
+  va_list ap;
+
+  va_start(ap, fmt);
+  ret = vsprintf(buf, fmt, ap);
+  va_end(ap);
+
+  con_print(buf);
+  return ret;
+}
diff --git a/kernel/con.o b/kernel/con.o
new file mode 100644
index 0000000..49168c9
--- /dev/null
+++ b/kernel/con.o
diff --git a/kernel/kernel b/kernel/kernel
new file mode 100755
index 0000000..664108b
--- /dev/null
+++ b/kernel/kernel
diff --git a/kernel/kmain.c b/kernel/kmain.c
new file mode 100644
index 0000000..2dc9e76
--- /dev/null
+++ b/kernel/kmain.c
@@ -0,0 +1,10 @@
+#include <kernel/con.h>
+
+extern int printf(char *fmt, ...);
+
+void kmain(void) {
+  con_init();
+
+  printf("Kernel booting...\n");
+  printf("Kernel booted!\n");
+}
diff --git a/kernel/kmain.o b/kernel/kmain.o
new file mode 100644
index 0000000..9a3a76d
--- /dev/null
+++ b/kernel/kmain.o
diff --git a/kernel/link.ld b/kernel/link.ld
new file mode 100644
index 0000000..67ae357
--- /dev/null
+++ b/kernel/link.ld
@@ -0,0 +1,11 @@
+OUTPUT_FORMAT(elf32-i386)
+/* OUTPUT_FORMAT(binary) */
+ENTRY(kboot)
+SECTIONS
+{
+  . = 0x100000;
+  .mboothdr : { *(.mboothdr) }
+  .text : { *(.text) }
+  .data : { *(.data) }
+  .bss : { *(.bss) }
+}
diff --git a/kernel/vsprintf.c b/kernel/vsprintf.c
new file mode 100644
index 0000000..f3feb43
--- /dev/null
+++ b/kernel/vsprintf.c
@@ -0,0 +1,18 @@
+#include <stdarg.h>
+
+int vsprintf(char *str, char *fmt, va_list ap) {
+  char *start = str;
+
+  while(*fmt) {
+    if(*fmt != '%') {
+      *str++ = *fmt++;
+      continue;
+    }
+
+    fmt++;
+  }
+
+  *str = 0;
+
+  return (str - start);
+}
diff --git a/kernel/vsprintf.o b/kernel/vsprintf.o
new file mode 100644
index 0000000..b5359fe
--- /dev/null
+++ b/kernel/vsprintf.o