From c1e6d245b100428cf7682d7df25e77769f2e8cef Mon Sep 17 00:00:00 2001
From: Fergal Moran <fergal.moran@gmail.com>
Date: Mon, 8 Jun 2020 12:35:51 +0100
Subject: [PATCH] Multi-line support in printf

---
 Makefile       |  7 +++++--
 src/gdt.cpp    |  6 +++---
 src/kernel.cpp | 34 +++++++++++++++++++++++++++++++---
 3 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/Makefile b/Makefile
index 8a80308..2776d87 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ GPPPARAMS = -m32 -fno-use-cxa-atexit -nostdlib -fno-builtin -fno-rtti -fno-excep
 ASPARAMS = --32
 LDPARAMS = -melf_i386
 
-objs = loader.o gdt.o kernel.o
+objs = loader.o gdt.o port.o kernel.o
 
 %.o: src/%.cpp
 	g++ $(GPPPARAMS) -o $@ -c $<
@@ -30,6 +30,9 @@ ferglos.iso: ferglos.bin
 
 run: ferglos.iso
 	/usr/lib/virtualbox/VirtualBoxVM --startvm ferglos
+	
+run-qemu: ferglos.iso
+	qemu-system-i386 -boot d -cdrom ferglos.iso -m 512
 
 clean:
-	rm -rfv iso *.o *.bin
+	rm -rfv $(objects) iso *.o *.bin
diff --git a/src/gdt.cpp b/src/gdt.cpp
index b06efc4..40213b3 100644
--- a/src/gdt.cpp
+++ b/src/gdt.cpp
@@ -16,9 +16,9 @@ GlobalDescriptorTable::GlobalDescriptorTable() : nullSegmentSelector(0, 0, 0),
     i[1] = (uint32_t)this;
     i[0] = sizeof(GlobalDescriptorTable) << 16;
 
-    asm volatile("lgdt (%0)"
-                 :
-                 : "p"(((uint8_t *)i) + 2));
+    __asm__ volatile("lgdt (%0)"
+                     :
+                     : "p"(((uint8_t *)i) + 2));
 }
 GlobalDescriptorTable::~GlobalDescriptorTable() {
 }
diff --git a/src/kernel.cpp b/src/kernel.cpp
index a2e0c44..ab78512 100644
--- a/src/kernel.cpp
+++ b/src/kernel.cpp
@@ -11,9 +11,34 @@
 
 void printf(char* str) {
     static uint16_t* VideoMemory = (uint16_t*)0xb8000;
+    static uint8_t x = 0, y = 0;
 
-    for (int i = 0; str[i] != '\0'; ++i)
-        VideoMemory[i] = (VideoMemory[i] & 0xFF00) | str[i];
+    for (int i = 0; str[i] != '\0'; ++i) {
+        switch (str[i]) {
+            case '\n':
+                y++;
+                x = 0;
+                break;
+            default:
+                VideoMemory[80 * y + x] = (VideoMemory[80 * y + x] & 0xFF00) | str[i];
+                x++;
+                break;
+        }
+
+        //line feed after 80 chars (terminal width)
+        if (x >= 80) {
+            y++;
+            x = 0;
+        }
+        //we've reached max screen rows
+        if (y > 25) {
+            for (y = 0; y < 25; y++) {
+                for (x - 0; x < 80; x++) {
+                    VideoMemory[80 * y + x] = (VideoMemory[80 * y + x] & 0xFF00) | ' ';
+                }
+            }
+        }
+    }
 }
 
 typedef void (*constructor)();
@@ -25,7 +50,10 @@ extern "C" void call_constructors() {
 }
 
 extern "C" void ferglos_Main(const void* multiboot_structure, uint32_t /*mb_mag*/) {
-    printf("Welcome to FerglOS v0.0.1!");
+    printf("Welcome to FerglOS v0.0.2!\n");
+    printf("Hitler blinks.");
+
+    GlobalDescriptorTable gdt;
     while (1)
         ;
 }
\ No newline at end of file