Basic vga write functions

currently has bug in pointers contained in bss, unsure why. Build, load, or segments are wrong. leaning towards segments.

1 files changed, 30 insertions, 12 deletions

diff --git a/src/kernel/main.c b/src/kernel/main.c
index f8e6c6a..d7965e2 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -1,17 +1,35 @@
 __asm__(".code16gcc\n");
 
-int func() {
-  __asm__(
-    "mov $0x10,  %%cx \n"
-    "mov $0x0A, %%ah  \n"
-    "mov $0x74, %%al  \n"
-    "int $0x10        \n"
-    "mov $42, %%eax   \n"
-    "ret              \n"
-    : :
-  );
+void vga_graphics_write_at_offset(char, short);
+void vga_graphics_write(char);
+void vga_graphics_write_str(char*);
+
+static short CURSOR_LOC = 0;
+
+void _start() {
+  vga_graphics_write('a');
+  vga_graphics_write('/');
+  vga_graphics_write('b');
+  char foo[] = "hello how are you";
+  vga_graphics_write_str(foo);
+  while(1) { }
+}
+
+void vga_graphics_write_str(char* str) {
+  while(*str) {
+    vga_graphics_write(*str++);
+  }
+}
+
+void vga_graphics_write(char value) {
+  vga_graphics_write_at_offset(value, CURSOR_LOC);
+  CURSOR_LOC += 2;
 }
 
-int _start() {
-  return 1;
+void vga_graphics_write_at_offset(char value, short offset) {
+  __asm__(
+    "mov %0, %%al          \n"
+    "mov %1, %%di          \n"
+    "mov %%al, %%gs:(%%di) \n"
+    : :"r"(value), "r"(offset) : "%ax", "%di");
 }