2fc6c35b2f
This way, the bootloader doesn't have to translate the entry point. This also makes xv6 multiboot-compliant and follows the convention used by Linux.
65 lines
1.6 KiB
ArmAsm
65 lines
1.6 KiB
ArmAsm
# Multiboot header, for multiboot boot loaders like GNU Grub.
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# http://www.gnu.org/software/grub/manual/multiboot/multiboot.html
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#
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# Using GRUB 2, you can boot xv6 from a file stored in a
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# Linux file system by copying kernel or kernelmemfs to /boot
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# and then adding this menu entry:
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#
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# menuentry "xv6" {
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# insmod ext2
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# set root='(hd0,msdos1)'
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# set kernel='/boot/kernel'
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# echo "Loading ${kernel}..."
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# multiboot ${kernel} ${kernel}
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# boot
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# }
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#include "asm.h"
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#include "memlayout.h"
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#include "mmu.h"
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#include "param.h"
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# Multiboot header. Data to direct multiboot loader.
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.p2align 2
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.text
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.globl multiboot_header
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multiboot_header:
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#define magic 0x1badb002
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#define flags 0
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.long magic
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.long flags
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.long (-magic-flags)
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# By convention, the _start symbol specifies the ELF entry point.
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# Since we haven't set up virtual memory yet, our entry point is
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# the physical address of 'entry'.
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.globl _start
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_start = V2P_WO(entry)
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# Entering xv6 on boot processor. Machine is mostly set up.
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.globl entry
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entry:
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# Turn on page size extension for 4Mbyte pages
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movl %cr4, %eax
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orl $(CR4_PSE), %eax
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movl %eax, %cr4
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# Set page directory
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movl $(V2P_WO(entrypgdir)), %eax
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movl %eax, %cr3
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# Turn on paging.
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movl %cr0, %eax
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orl $(CR0_PG|CR0_WP), %eax
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movl %eax, %cr0
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# Set up the stack pointer.
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movl $(stack + KSTACKSIZE), %esp
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# Jump to main(), and switch to executing at
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# high addresses. The indirect call is needed because
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# the assembler produces a PC-relative instruction
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# for a direct jump.
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mov $main, %eax
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jmp *%eax
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.comm stack, KSTACKSIZE
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