README.md

@@ -68,7 +68,7 @@ gdb kernel.elf
 
 ## Documentation
 
-Two other documents are available to help you understand the project better. One is the User's Manual, labelled [USERS.md](USERS.md), and the other one is the Developer's Manual, labelled [DEVELOPERS.md](DEVELOPERS.md). They are full of useful resources around Blank OS. You'll learn how to use the system and how to contribute to it.
+Two other documents are available to help you understand the project better. One is the User's Manual, labelled [USERS.md](docs/USERS.md), and the other one is the Developer's Manual, labelled [DEVELOPERS.md](docs/DEVELOPERS.md). They are full of useful resources around Blank OS. You'll learn how to use the system and how to contribute to it.
 
 ### Resources
 

link.ld

@@ -27,4 +27,6 @@ SECTIONS {
     *(COMMON)
     *(.bss)
   }
+
+  end = .; _end = .; __end = .;
 }

src/kernel/kheap.c

@@ -0,0 +1,42 @@
+#include "kheap.h"
+
+#include "../libc/stdint.h"
+
+extern uint32_t end;
+uint32_t placement_address = (uint32_t)&end;
+
+uint32_t kmalloc_int(uint32_t sz, int align, uint32_t *phys)
+{
+	if (align == 1 && (placement_address & 0x00000FFF))
+	{
+		placement_address &= 0xFFFFF000;
+		placement_address += 0x1000;
+	}
+	if (phys)
+	{
+		*phys = placement_address;
+	}
+	uint32_t tmp = placement_address;
+	placement_address += sz;
+	return tmp;
+}
+
+uint32_t kmalloc_a(uint32_t sz)
+{
+	return kmalloc_int(sz, 1, 0);
+}
+
+uint32_t kmalloc_p(uint32_t sz, uint32_t *phys)
+{
+	return kmalloc_int(sz, 0, phys);
+}
+
+uint32_t kmalloc_ap(uint32_t sz, uint32_t *phys)
+{
+	return kmalloc_int(sz, 1, phys);
+}
+
+uint32_t kmalloc(uint32_t sz)
+{
+	return kmalloc_int(sz, 0, 0);
+}

src/kernel/kheap.h

@@ -0,0 +1,11 @@
+#ifndef KHEAP_H
+#define KHEAP_H
+
+#include "../libc/stdint.h"
+
+uint32_t kmalloc_a(uint32_t sz);
+uint32_t kmalloc_p(uint32_t sz, uint32_t *phys);
+uint32_t kmalloc_ap(uint32_t sz, uint32_t *phys);
+uint32_t kmalloc(uint32_t sz);
+
+#endif

src/kernel/kmain.c

@@ -3,7 +3,7 @@
 #include "gdt.h"
 #include "idt.h"
 #include "system.h"
-//#include <stdarg.h>
+#include "paging.h"
 
 char* ascii_title =
 "\n"
@@ -36,6 +36,12 @@ void kmain(unsigned int multiboot_info_address)
   colorputs(ascii_title, 10);
   colorputs("   by @xamidev - star the repo for a cookie!\n\n", 14);
 
+  init_paging();
+  printf("Hello, paging world!\n");
+
+  uint32_t *ptr = (uint32_t*)0xA0000000;
+  uint32_t do_page_fault = *ptr;
+
   timer_install();
   serial_printf(2, "%d\tinitialized timer handler", global_ticks); 
   keyboard_install(); 

src/kernel/paging.c

@@ -0,0 +1,150 @@
+#include "../libc/stdint.h"
+#include "paging.h"
+#include "../libc/stdio.h"
+#include "system.h"
+#include "kheap.h"
+
+
+uint32_t *frames;
+uint32_t nframes;
+
+extern uint32_t placement_address;
+
+#define INDEX_FROM_BIT(a) (a/(8*4))
+#define OFFSET_FROM_BIT(a) (a%(8*4))
+
+static void set_frame(uint32_t frame_addr)
+{
+	uint32_t frame = frame_addr/0x1000;
+	uint32_t idx = INDEX_FROM_BIT(frame);
+	uint32_t off = OFFSET_FROM_BIT(frame);
+	frames[idx] |= (0x1 << off);
+}
+
+static void clear_frame(uint32_t frame_addr)
+{
+	uint32_t frame = frame_addr/0x1000;
+	uint32_t idx = INDEX_FROM_BIT(frame);
+	uint32_t off = OFFSET_FROM_BIT(frame);
+	frames[idx] &= ~(0x1 << off);
+}
+
+/*
+static uint32_t test_frame(uint32_t frame_addr)
+{
+   	uint32_t frame = frame_addr/0x1000;
+   	uint32_t idx = INDEX_FROM_BIT(frame);
+   	uint32_t off = OFFSET_FROM_BIT(frame);
+   	return (frames[idx] & (0x1 << off));
+}
+*/
+
+static uint32_t first_frame()
+{
+	uint32_t i, j;
+	for (i=0; i<INDEX_FROM_BIT(nframes); i++)
+	{
+		if (frames[i] != 0xFFFFFFFF)
+		{
+			for (j=0; j<32; j++)
+			{
+				uint32_t toTest = 0x1 << j;
+				if (!(frames[i]&toTest))
+				{
+					return i*4*8+j;
+				}
+			}
+		}
+	}
+	return 0;
+}
+
+void alloc_frame(page_t *page, int is_kernel, int is_writeable)
+{
+	if (page->frame != 0)
+	{
+		return;
+	} else {
+		uint32_t idx = first_frame();
+		if (idx == (uint32_t)-1)
+		{
+			panic();
+		}
+		set_frame(idx*0x1000);
+		page->present = 1;
+		page->rw = (is_writeable)?1:0;
+		page->user = (is_kernel)?0:1;
+		page->frame = idx;
+	}
+}
+
+void free_frame(page_t *page)
+{
+	uint32_t frame;
+	if (!(frame=page->frame))
+	{
+		return;
+	} else {
+		clear_frame(frame);
+		page->frame = 0x0;
+	}
+}
+
+void init_paging()
+{
+	uint32_t mem_end_page = 0x10000000;
+	nframes = mem_end_page / 0x1000;
+	frames = (uint32_t*)kmalloc(INDEX_FROM_BIT(nframes));
+	memset(frames, 0, INDEX_FROM_BIT(nframes));
+
+	page_directory_t* kernel_directory = (page_directory_t*)kmalloc_a(sizeof(page_directory_t));
+	memset(kernel_directory, 0, sizeof(page_directory_t));
+	//page_directory_t* current_directory = kernel_directory;
+
+	unsigned int i = 0;
+	while (i < placement_address)
+	{
+		alloc_frame(get_page(i, 1, kernel_directory), 0, 0);
+		i += 0x1000;
+	}
+
+	irq_install_handler(14, page_fault);
+
+	switch_page_directory(kernel_directory);	
+}
+
+void switch_page_directory(page_directory_t *dir)
+{
+	//page_directory_t* current_directory = dir;
+	asm volatile("mov %0, %%cr3":: "r"(&dir->tablesPhysical));
+	uint32_t cr0;
+	asm volatile("mov %%cr0, %0": "=r"(cr0));
+	cr0 |= 0x80000000;
+	asm volatile("mov %0, %%cr0":: "r"(cr0));
+}
+
+page_t *get_page(uint32_t address, int make, page_directory_t *dir)
+{
+	address /= 0x1000;
+	uint32_t table_idx = address / 1024;
+	if (dir->tables[table_idx])
+	{
+		return &dir->tables[table_idx]->pages[address%1024];
+	} else if (make)
+	{
+		uint32_t tmp;
+		dir->tables[table_idx] = (page_table_t*)kmalloc_ap(sizeof(page_table_t), &tmp);
+		memset(dir->tables[table_idx], 0, 0x1000);
+		dir->tablesPhysical[table_idx] = tmp | 0x7;
+		return &dir->tables[table_idx]->pages[address%1024];
+	} else {
+		return 0;
+	}
+	return 0;
+}
+
+void page_fault()
+{
+	puts("Page fault");
+	panic();
+}

src/kernel/paging.h

@@ -0,0 +1,34 @@
+#ifndef PAGING_H
+#define PAGING_H
+
+#include "system.h"
+#include "../libc/stdint.h"
+typedef struct
+{
+	uint32_t present	: 1;
+	uint32_t rw		: 1;
+	uint32_t user		: 1;
+	uint32_t accessed	: 1;
+	uint32_t dirty		: 1;
+	uint32_t unused		: 7;
+	uint32_t frame		: 20;
+} page_t;
+
+typedef struct
+{
+	page_t pages[1024];
+} page_table_t;
+
+typedef struct
+{
+	page_table_t *tables[1024];
+	uint32_t tablesPhysical[1024];
+	uint32_t physicalAsddr;
+} page_directory_t;
+
+void init_paging();
+void switch_page_directory(page_directory_t *new);
+page_t *get_page(uint32_t address, int make, page_directory_t *dir);
+void page_fault();
+
+#endif

src/kernel/system.c

@@ -1,4 +1,5 @@
 #include "system.h"
+#include "../libc/stdint.h"
 
 void *memset(void *dest, char val, size_t count)
 {
@@ -6,3 +7,8 @@ void *memset(void *dest, char val, size_t count)
 	for(; count != 0; count--) *temp++ = val;
 	return dest;
 }
+
+void panic()
+{
+	for (;;);	
+}

src/kernel/system.h

@@ -1,6 +1,8 @@
 #ifndef SYSTEM_H
 #define SYSTEM_H
 
+#include "../libc/stdint.h"
+
 typedef int size_t;
 
 void *memset(void *dest, char val, size_t count);
@@ -13,6 +15,7 @@ struct regs
 	unsigned int eip, cs, eflags, useresp, ss;
 };
 
+void panic();
 void isr_install();
 void irq_install();
 void irq_install_handler(int irq, void (*handler)(struct regs *r));