1# Multiboot header, for multiboot boot loaders like GNU Grub. 2# http://www.gnu.org/software/grub/manual/multiboot/multiboot.html 3# 4# Using GRUB 2, you can boot xv6 from a file stored in a 5# Linux file system by copying kernel or kernelmemfs to /boot 6# and then adding this menu entry: 7# 8# menuentry "xv6" { 9# insmod ext2 10# set root='(hd0,msdos1)' 11# set kernel='/boot/kernel' 12# echo "Loading ${kernel}..." 13# multiboot ${kernel} ${kernel} 14# boot 15# } 16 17#include "asm.h" 18#include "memlayout.h" 19#include "mmu.h" 20#include "param.h" 21 22# Multiboot header. Data to direct multiboot loader. 23.p2align 2 24.text 25.globl multiboot_header 26multiboot_header: 27 #define magic 0x1badb002 28 #define flags 0 29 .long magic 30 .long flags 31 .long (-magic-flags) 32 33# By convention, the _start symbol specifies the ELF entry point. 34# Since we haven't set up virtual memory yet, our entry point is 35# the physical address of 'entry'. 36.globl _start 37_start = V2P_WO(entry) 38 39# Entering xv6 on boot processor, with paging off. 40.globl entry 41entry: 42 # Turn on page size extension for 4Mbyte pages 43 movl %cr4, %eax 44 orl $(CR4_PSE), %eax 45 movl %eax, %cr4 46 # Set page directory 47 movl $(V2P_WO(entrypgdir)), %eax 48 movl %eax, %cr3 49 # Turn on paging. 50 movl %cr0, %eax 51 orl $(CR0_PG|CR0_WP), %eax 52 movl %eax, %cr0 53 54 # Set up the stack pointer. 55 movl $(stack + KSTACKSIZE), %esp 56 57 # Jump to main(), and switch to executing at 58 # high addresses. The indirect call is needed because 59 # the assembler produces a PC-relative instruction 60 # for a direct jump. 61 mov $main, %eax 62 jmp *%eax 63 64.comm stack, KSTACKSIZE 65