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format ELF

MULTIBOOT_MEMORY_INFO			equ		1 shl 1
MULTIBOOT_BOOTLOADER_MAGIC		equ		0x1BADB002
MULTIBOOT_HEADER_FLAGS			equ		MULTIBOOT_MEMORY_INFO
MULTIBOOT_CHECKSUM				equ		-(MULTIBOOT_BOOTLOADER_MAGIC + MULTIBOOT_HEADER_FLAGS)

section '.loader' executable writeable

public _start
public _stbss
public _endbss

extrn _loader

align 4
	dd	MULTIBOOT_BOOTLOADER_MAGIC
	dd	MULTIBOOT_HEADER_FLAGS
	dd	MULTIBOOT_CHECKSUM
	
_start:
	mov		esp, _endbss
	sub		esp, 0xC0000000 - 0x101000
	push	ebx
	call	_loader

section '.bss' writeable
_stbss:
	rb	8192
_endbss:

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#include <x86_32/paging.h>
#include <x86_32/multiboot.h>

#define PHYS(x)		((x) - 0xC0000000 + 0x101000)
#define LD(x)		((unsigned long)&x)

void loader(multiboot_info_t*) __attribute__((section(".loader")));
extern char sttext;	/* start of text section(virtual) */
extern char endtext;
extern char stdata;	/* start of data section(virtual) */
extern char enddata;
extern char stbss;
extern char endbss;
extern char end;		/* end of kernel(virtual) */

#define TEXT_START	LD(sttext)
#define	DATA_START	LD(stdata)
#define	BSS_START	LD(stbss)
#define TEXT_END	LD(endtext)
#define	DATA_END	LD(enddata)
#define	BSS_END		LD(endbss)
#define	TEXT_SIZE	(TEXT_END-TEXT_START)
#define	DATA_SIZE	(DATA_END-DATA_START)
#define	STACK_SIZE	(BSS_END-BSS_START)
#define	END			LD(end)

void archmain();

void
loader(multiboot_info_t *mbi) {
	unsigned long	*page_directory		= (unsigned long*)PHYS(PAGE_ALIGN(END));
	unsigned long   *page_table0		= page_directory + PAGE_SIZE; /* 1st MB and loader */
	unsigned long	*page_table1		= page_table0 + PAGE_SIZE; /* for main kernel */
	int				i;
	
	/* clearing page directory and pagetables */
	for(i = 0; i < 1024; i++)
		page_directory[i] = 
		page_table0[i] =
		page_table1[i] = 0;
	
	/* Creating page table for 1st MB and loader */
	page_directory[0] = (unsigned long)page_table0	| PDE_PRESENT
													| PDE_WRITEABLE;
	/* Creating page table for kernel */
	page_directory[PDE_ENTRY(TEXT_START)] =	(unsigned long)page_table1	| PDE_PRESENT
																		| PDE_WRITEABLE;	
	/* mapping 1st MiB */
	for(i = 0; i < 256; i++)
		page_table0[i] = (i*PAGE_SIZE)	| PTE_PRESENT
										| PTE_WRITEABLE;
	/* mapping loader */
	page_table0[256] = (1024*1024) | PTE_PRESENT;
	/* mapping '.bss' */
	for(i = 0; i < STACK_SIZE/PAGE_SIZE; i++) {
		/* mapping 1:1, for loader */
		page_table0[PTE_ENTRY(PHYS(BSS_START))+i] = PHYS(BSS_START+i*PAGE_SIZE) | PTE_PRESENT
																				| PTE_WRITEABLE;
		/* mapping to kernel */
		page_table1[PTE_ENTRY(BSS_START)+i]= PHYS(BSS_START+i*PAGE_SIZE)| PTE_PRESENT
																		| PTE_WRITEABLE;
	}
	/* mapping '.text' */
	for(i = 0; i < PAGE_ALIGN(TEXT_SIZE)/PAGE_SIZE; i++) {
		page_table1[PTE_ENTRY(TEXT_START)+i] = PHYS(TEXT_START+i*PAGE_SIZE)| PTE_PRESENT;
	}
	/* mapping '.data' */
	for(i = 0; i < PAGE_ALIGN(DATA_SIZE)/PAGE_SIZE; i++) {
		page_table1[PTE_ENTRY(DATA_START)+i] = PHYS(DATA_START+i*PAGE_SIZE)	| PTE_PRESENT
																			| PTE_WRITEABLE;
	}
	/* enable paging */
	__asm volatile(	"add	$(0xC0000000 - 0x101000), %%esp\n" /* set stack to kernel adresses */
					"movl	%0, %%eax\n"
					"movl	%%eax, %%cr3\n"
					"movl	%%cr0, %%eax\n"
					"orl	$0x80000000, %%eax\n"
					"movl	%%eax, %%cr0"::"m"(page_directory));

	archmain();
	for(;;);
}

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#ifndef X86_32_PAGING_H
#define X86_32_PAGIND_H

#define	PAGE_SHIFT		(12)
#define PAGE_SIZE		(1UL << PAGE_SHIFT)

#define PAGE_BASE(x)	((x) & ~(PAGE_SIZE - 1))
#define PAGE_ALIGN(x)	(((x) + PAGE_SIZE) & ~(PAGE_SIZE - 1))
/* Page directory entry */
#define	PDE_ENTRY(x)		((x) >> 22)
#define PDE_PRESENT			(1UL << 0)
#define	PDE_WRITEABLE		(1UL << 1)
#define	PDE_USERACCESS		(1UL << 2)
#define PDE_WRITETHROUGH	(1UL << 3)
#define	PDE_CACHEDISABLE	(1UL << 4)
#define PDE_ACCESSED		(1UL << 5)
/* Page table entry */
#define	PTE_ENTRY(x)		(((x) >> 12) & 0x3ff)
#define PTE_PRESENT			(1UL << 0)
#define	PTE_WRITEABLE		(1UL << 1)
#define	PTE_USERACCESS		(1UL << 2)
#define PTE_WRITETHROUGH	(1UL << 3)
#define	PTE_CACHEDISABLE	(1UL << 4)
#define PTE_ACCESSED		(1UL << 5)
#define PTE_DIRTY			(1UL << 6)

#endif /* X86_32_PAGING_H */

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static int i = 1;
void
archmain() {
	for(;;); /* (;,;)-=<fhtagn!> */
}

Code: Select all

OUTPUT_FORMAT("elf32-i386")
ENTRY(_start)
SECTIONS
{
	. = 0x00100000;
	.loader :
	{
		*(.loader)
	}
	. = 0xC0000000;
	.text ALIGN(0x1000) : AT(ADDR(.text) - 0xBFF00000 + 0x1000)
	{
		_sttext = .;
		*(.text)
		*(.rodata*)
		_endtext = .;
	}
	.data ALIGN(0x1000) : AT(ADDR(.data) - 0xBFF00000 + 0x1000)
	{
		_stdata = .;
		*(.data)
		_enddata = .;
	}
	.bss ALIGN(0x1000) : AT(ADDR(.bss) - 0xBFF00000 + 0x1000)
	{
		*(.bss)
		*(COMMON)
	}
	_end = .;
}