From d5cf6a9696f6f86bec5652f94ba7485aae4ca1bc Mon Sep 17 00:00:00 2001
From: James Barnett <noreply@jamesbarnett.xyz>
Date: Tue, 28 Aug 2018 16:21:37 +0100
Subject: Add print_ln function

---
 kernel/io/text_mode_diplay.h  |  3 +++
 kernel/io/text_mode_display.c | 34 ++++++++++++++++++++++++++++++++++
 kernel/kernel-bootstrap.asm   | 22 ++++++++++++++++++++++
 kernel/kernel.c               | 15 +++++++++++++++
 4 files changed, 74 insertions(+)
 create mode 100644 kernel/io/text_mode_diplay.h
 create mode 100644 kernel/io/text_mode_display.c
 create mode 100644 kernel/kernel-bootstrap.asm
 create mode 100644 kernel/kernel.c

(limited to 'kernel')

diff --git a/kernel/io/text_mode_diplay.h b/kernel/io/text_mode_diplay.h
new file mode 100644
index 0000000..d2d1180
--- /dev/null
+++ b/kernel/io/text_mode_diplay.h
@@ -0,0 +1,3 @@
+void clear_screen();
+void print(char *msg);
+void print_ln(char *msg);
\ No newline at end of file
diff --git a/kernel/io/text_mode_display.c b/kernel/io/text_mode_display.c
new file mode 100644
index 0000000..514ba9f
--- /dev/null
+++ b/kernel/io/text_mode_display.c
@@ -0,0 +1,34 @@
+#define COLS 80
+#define ROWS 25
+#define FRAME_SIZE (ROWS * COLS * 2) // 2 bytes per char
+
+char *video_ram = (char *)0xB8000;
+int cursor_pos = 0;
+
+void clear_screen()
+{
+  for (int i = 0; i < FRAME_SIZE; i = i + 2)
+  {
+    video_ram[i] = ' ';
+    video_ram[i + 1] = 0x07;
+  };
+  cursor_pos = 0;
+}
+
+void print(char *msg)
+{
+  int j = 0;
+  while (msg[j] != '\0')
+  {
+    video_ram[cursor_pos++] = msg[j];
+    video_ram[cursor_pos++] = 0x07;
+    ++j;
+  }
+}
+
+void print_ln(char *msg)
+{
+  print(msg);
+  int current_line = cursor_pos / COLS;
+  cursor_pos = (current_line + 1) * (COLS*2);
+}
diff --git a/kernel/kernel-bootstrap.asm b/kernel/kernel-bootstrap.asm
new file mode 100644
index 0000000..9e3b10e
--- /dev/null
+++ b/kernel/kernel-bootstrap.asm
@@ -0,0 +1,22 @@
+bits 32                   ; nasm 32-bit mode
+section .text
+
+                          ; multiboot header
+align 4
+dd 0x1BADB002
+dd 0x00
+dd - (0x1BADB002 + 0x00)  ; checksum
+
+global start
+extern kernel_entrypoint
+
+                          ; call kernel and halt
+start:
+  cli                     ; disable interrups
+  mov esp, stack_space
+  call kernel_entrypoint
+  hlt
+
+section .bss
+resb 8192
+stack_space:
\ No newline at end of file
diff --git a/kernel/kernel.c b/kernel/kernel.c
new file mode 100644
index 0000000..e872fa5
--- /dev/null
+++ b/kernel/kernel.c
@@ -0,0 +1,15 @@
+#include "./io/text_mode_diplay.h"
+
+void run_kern()
+{
+  clear_screen();
+
+  print_ln("I am a kernel!");
+  print("I am on a new line");
+  print(" - I am not");
+}
+
+void kernel_entrypoint()
+{
+  run_kern();
+}
-- 
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