From 89f7f1b114c1bbea3ad62808bf3653e1d2337d1f Mon Sep 17 00:00:00 2001
From: Aleksa Vučković <aleksav013@gmail.com>
Date: Wed, 27 Oct 2021 11:44:12 +0200
Subject: Added paging

---
 Makefile            |  23 +++---
 src/as/Makefile     |   2 +-
 src/as/paging.s     |  21 ++++++
 src/c/Makefile      |   2 +-
 src/c/irq.c         | 204 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/c/irq_handler.c | 204 ----------------------------------------------------
 src/c/kernel.c      |   2 +
 src/c/paging.c      |  51 +++++++++++++
 src/c/tty.c         |   5 +-
 9 files changed, 295 insertions(+), 219 deletions(-)
 create mode 100644 src/as/paging.s
 create mode 100644 src/c/irq.c
 delete mode 100644 src/c/irq_handler.c
 create mode 100644 src/c/paging.c

diff --git a/Makefile b/Makefile
index dd02b46..e99a6a6 100644
--- a/Makefile
+++ b/Makefile
@@ -10,10 +10,12 @@ CP=cp
 QEMU=qemu-system-x86_64
 
 SOURCE_DIR=src
+BUILD_DIR=${CURDIR}/build
+ISO_DIR=isodir
 AS_SOURCE_DIR=$(SOURCE_DIR)/as
 C_SOURCE_DIR=$(SOURCE_DIR)/c
-export BUILD_DIR=${CURDIR}/build
-ISO_DIR=isodir
+export AS_OBJECT_DIR=$(BUILD_DIR)/as
+export C_OBJECT_DIR=$(BUILD_DIR)/c
 
 TARGET=myos
 BINARY=$(BUILD_DIR)/$(TARGET).bin
@@ -21,19 +23,19 @@ ISO=$(TARGET).iso
 
 CRTI_SOURCE=crti.s
 CRTN_SOURCE=crtn.s
-AS_SOURCE=boot.s irq.s
-C_SOURCES=gdt.c heap.c idt.c kernel.c keyboard.c keymap.c stdio.c string.c tty.c vga.c irq_handler.c stack_protector.c timer.c
+AS_SOURCE=boot.s irq.s paging.s
+C_SOURCES=gdt.c heap.c idt.c kernel.c keyboard.c keymap.c stdio.c string.c tty.c vga.c irq.c stack_protector.c timer.c paging.c
 
 C_SOURCE_FILES=$(patsubst %,$(C_SOURCE_DIR)/%,$(C_SOURCES))
-export C_OBJECTS=$(patsubst %,$(BUILD_DIR)/%,$(C_SOURCES:c=o))
+export C_OBJECTS=$(patsubst %,$(C_OBJECT_DIR)/%,$(C_SOURCES:c=o))
 
-AS_OBJECT=$(patsubst %,$(BUILD_DIR)/%,$(AS_SOURCE:s=o))
-CRTI_OBJECT=$(patsubst %,$(BUILD_DIR)/%,$(CRTI_SOURCE:s=o))
-CRTN_OBJECT=$(patsubst %,$(BUILD_DIR)/%,$(CRTN_SOURCE:s=o))
+AS_OBJECT=$(patsubst %,$(AS_OBJECT_DIR)/%,$(AS_SOURCE:s=o))
+CRTI_OBJECT=$(patsubst %,$(AS_OBJECT_DIR)/%,$(CRTI_SOURCE:s=o))
+CRTN_OBJECT=$(patsubst %,$(AS_OBJECT_DIR)/%,$(CRTN_SOURCE:s=o))
 
 AS_SOURCES=$(AS_SOURCE) $(CRTI_SOURCE) $(CRTN_SOURCE)
 AS_SOURCE_FILES=$(patsubst %,$(AS_SOURCE_DIR)/%,$(AS_SOURCES))
-export AS_OBJECTS=$(patsubst %,$(BUILD_DIR)/%,$(AS_SOURCES:s=o))
+export AS_OBJECTS=$(patsubst %,$(AS_OBJECT_DIR)/%,$(AS_SOURCES:s=o))
 
 CRTBEGIN_OBJ=$(shell $(CC) -print-file-name=crtbegin.o)
 CRTEND_OBJ=$(shell $(CC) -print-file-name=crtend.o)
@@ -48,7 +50,8 @@ $(BINARY): $(OBJ)
 	$(CC) -T $(SOURCE_DIR)/linker.ld -o $(BINARY) $(CFLAGS) -nostdlib -lgcc $(OBJ)
 
 compile: $(AS_SOURCE_FILES) $(C_SOURCE_FILES)
-	$(MKDIR) $(BUILD_DIR)
+	$(MKDIR) $(AS_OBJECT_DIR)
+	$(MKDIR) $(C_OBJECT_DIR)
 	$(MAKE) --directory $(AS_SOURCE_DIR)
 	$(MAKE) --directory $(C_SOURCE_DIR)
 	$(MAKE) $(BINARY)
diff --git a/src/as/Makefile b/src/as/Makefile
index e2c476d..bd5664b 100644
--- a/src/as/Makefile
+++ b/src/as/Makefile
@@ -1,5 +1,5 @@
 .PHONY: all
 all: $(AS_OBJECTS)
 
-$(BUILD_DIR)/%.o: %.s
+$(AS_OBJECT_DIR)/%.o: %.s
 	$(AS) $< -o $@
diff --git a/src/as/paging.s b/src/as/paging.s
new file mode 100644
index 0000000..2dd52d3
--- /dev/null
+++ b/src/as/paging.s
@@ -0,0 +1,21 @@
+.globl loadPageDirectory
+loadPageDirectory:
+    push %ebp
+    mov %esp, %ebp
+    mov 8(%esp), %eax
+    mov %eax, %cr3
+    mov %ebp, %esp
+    pop %ebp
+    ret
+
+.text
+.globl enablePaging
+enablePaging:
+    push %ebp
+    mov %esp, %ebp
+    mov %cr0, %eax
+    or $0x80000000, %eax
+    mov %eax, %cr0
+    mov %ebp, %esp
+    pop %ebp
+    ret
diff --git a/src/c/Makefile b/src/c/Makefile
index 7c5d1af..9625009 100644
--- a/src/c/Makefile
+++ b/src/c/Makefile
@@ -1,5 +1,5 @@
 .PHONY: all
 all: $(C_OBJECTS)
 
-$(BUILD_DIR)/%.o: %.c
+$(C_OBJECT_DIR)/%.o: %.c
 	$(CC) -c $< -o $@ -std=gnu99 $(CFLAGS)
diff --git a/src/c/irq.c b/src/c/irq.c
new file mode 100644
index 0000000..6b80a52
--- /dev/null
+++ b/src/c/irq.c
@@ -0,0 +1,204 @@
+#include"../include/stdio.h"
+#include"../include/asm.h"
+
+#define INTERRUPT_GATE_32 0x8e
+
+#define KERNEL_CODE 0x08
+#define KERNEL_DATA 0x10
+
+#define PIC1_COMMAND_PORT 0x20
+#define PIC1_DATA_PORT 0x21
+#define PIC2_COMMAND_PORT 0xA0
+#define PIC2_DATA_PORT 0xA1
+
+void irq0_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 0.\n");
+}
+
+void irq1_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 1.\n");
+}
+
+void irq2_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 2.\n");
+}
+
+void irq3_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 3.\n");
+}
+
+void irq4_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 4.\n");
+}
+
+void irq5_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 5.\n");
+}
+
+void irq6_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 6.\n");
+}
+
+void irq7_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 7.\n");
+}
+
+void irq8_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 8.\n");
+}
+
+void irq9_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 9.\n");
+}
+
+void irq10_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 10.\n");
+}
+
+void irq11_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 11.\n");
+}
+
+void irq12_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 12.\n");
+}
+
+void irq13_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 13.\n");
+}
+
+void irq14_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 14.\n");
+}
+
+void irq15_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 15.\n");
+}
+
+void irq16_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 16.\n");
+}
+
+void irq17_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 17.\n");
+}
+
+void irq18_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 18.\n");
+}
+
+void irq19_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 19.\n");
+}
+
+void irq20_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 20.\n");
+}
+
+void irq21_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 21.\n");
+}
+
+void irq22_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 22.\n");
+}
+
+void irq23_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 23.\n");
+}
+
+void irq24_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 24.\n");
+}
+
+void irq25_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 25.\n");
+}
+
+void irq26_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 26.\n");
+}
+
+void irq27_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 27.\n");
+}
+
+void irq28_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 28.\n");
+}
+
+void irq29_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 29.\n");
+}
+
+void irq30_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 30.\n");
+}
+
+void irq31_handler()
+{
+    ioport_out(PIC1_COMMAND_PORT, 0x20);
+    printf("Interrupt 31.\n");
+}
diff --git a/src/c/irq_handler.c b/src/c/irq_handler.c
deleted file mode 100644
index 6b80a52..0000000
--- a/src/c/irq_handler.c
+++ /dev/null
@@ -1,204 +0,0 @@
-#include"../include/stdio.h"
-#include"../include/asm.h"
-
-#define INTERRUPT_GATE_32 0x8e
-
-#define KERNEL_CODE 0x08
-#define KERNEL_DATA 0x10
-
-#define PIC1_COMMAND_PORT 0x20
-#define PIC1_DATA_PORT 0x21
-#define PIC2_COMMAND_PORT 0xA0
-#define PIC2_DATA_PORT 0xA1
-
-void irq0_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 0.\n");
-}
-
-void irq1_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 1.\n");
-}
-
-void irq2_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 2.\n");
-}
-
-void irq3_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 3.\n");
-}
-
-void irq4_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 4.\n");
-}
-
-void irq5_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 5.\n");
-}
-
-void irq6_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 6.\n");
-}
-
-void irq7_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 7.\n");
-}
-
-void irq8_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 8.\n");
-}
-
-void irq9_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 9.\n");
-}
-
-void irq10_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 10.\n");
-}
-
-void irq11_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 11.\n");
-}
-
-void irq12_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 12.\n");
-}
-
-void irq13_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 13.\n");
-}
-
-void irq14_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 14.\n");
-}
-
-void irq15_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 15.\n");
-}
-
-void irq16_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 16.\n");
-}
-
-void irq17_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 17.\n");
-}
-
-void irq18_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 18.\n");
-}
-
-void irq19_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 19.\n");
-}
-
-void irq20_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 20.\n");
-}
-
-void irq21_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 21.\n");
-}
-
-void irq22_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 22.\n");
-}
-
-void irq23_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 23.\n");
-}
-
-void irq24_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 24.\n");
-}
-
-void irq25_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 25.\n");
-}
-
-void irq26_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 26.\n");
-}
-
-void irq27_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 27.\n");
-}
-
-void irq28_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 28.\n");
-}
-
-void irq29_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 29.\n");
-}
-
-void irq30_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 30.\n");
-}
-
-void irq31_handler()
-{
-    ioport_out(PIC1_COMMAND_PORT, 0x20);
-    printf("Interrupt 31.\n");
-}
diff --git a/src/c/kernel.c b/src/c/kernel.c
index 62f444c..48dbccb 100644
--- a/src/c/kernel.c
+++ b/src/c/kernel.c
@@ -5,10 +5,12 @@ void init_idt_table(void);
 void init_keyboard(void);
 void init_timer(uint32_t frequency);
 void prompt(void);
+void set_paging();
 
 void kernel_main(void)
 {
     terminal_initialize();
+    set_paging();
     init_idt_table();
     init_keyboard();
     init_timer(50);
diff --git a/src/c/paging.c b/src/c/paging.c
new file mode 100644
index 0000000..b256b74
--- /dev/null
+++ b/src/c/paging.c
@@ -0,0 +1,51 @@
+#include"../include/types.h"
+
+extern void loadPageDirectory(uint32_t*);
+extern void enablePaging();
+
+uint32_t page_directory[1024] __attribute__((aligned(4096)));
+
+void set_pd()
+{
+    //set each entry to not present
+    for(size_t i=0;i<1024;i++)
+    {
+	// This sets the following flags to the pages:
+	//   Supervisor: Only kernel-mode can access them
+	//   Write Enabled: It can be both read from and written to
+	//   Not Present: The page table is not present
+	page_directory[i] = 0x00000002;
+    }
+}
+
+uint32_t first_page_table[1024] __attribute__((aligned(4096)));
+
+void set_pt()
+{
+    // holds the physical address where we want to start mapping these pages to.
+    // in this case, we want to map these pages to the very beginning of memory.
+    unsigned int i;
+     
+    //we will fill all 1024 entries in the table, mapping 4 megabytes
+    for(i = 0; i < 1024; i++)
+    {
+	// As the address is page aligned, it will always leave 12 bits zeroed.
+	// Those bits are used by the attributes ;)
+	first_page_table[i] = (i * 0x1000) | 3; // attributes: supervisor level, read/write, present.
+    }
+}
+
+void put_pt()
+{
+    // attributes: supervisor level, read/write, present
+    page_directory[0] = ((uint32_t)first_page_table) | 3;
+}
+
+void set_paging()
+{
+    set_pd();
+    set_pt();
+    put_pt();
+    loadPageDirectory(page_directory);
+    enablePaging();
+}
diff --git a/src/c/tty.c b/src/c/tty.c
index 116a15e..c473fa1 100644
--- a/src/c/tty.c
+++ b/src/c/tty.c
@@ -110,9 +110,8 @@ void neofetch()
 
     for(size_t i=0;i<16;i++)
     {
-	if(i==0) set_color(i,VGA_COLOR_WHITE);
-	else set_color(i,VGA_COLOR_BLACK);
-	printf("@%d ",i);
+	set_color(0,i);
+	printf("  ",i);
     }
     printf("\n");
 
-- 
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