321 lines
8.1 KiB
ArmAsm
321 lines
8.1 KiB
ArmAsm
/*
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* header.S
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* Based on bootsect.S and setup.S
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* modified by more people than can be counted
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*
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* Rewritten as a common file by H. Peter Anvin (Apr 2007)
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*
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* BIG FAT NOTE: We're in real mode using 64k segments. Therefore segment
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* addresses must be multiplied by 16 to obtain their respective linear
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* addresses. To avoid confusion, linear addresses are written using leading
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* hex while segment addresses are written as segment:offset.
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*
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*/
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#include <asm/segment.h>
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#include <linux/utsrelease.h>
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#include <asm/boot.h>
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#include <asm/e820.h>
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#include <asm/page_types.h>
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#include <asm/setup.h>
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#include "boot.h"
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#include "voffset.h"
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#include "zoffset.h"
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BOOTSEG = 0x07C0 /* original address of boot-sector */
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SYSSEG = 0x1000 /* historical load address >> 4 */
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#ifndef SVGA_MODE
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#define SVGA_MODE ASK_VGA
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#endif
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#ifndef RAMDISK
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#define RAMDISK 0
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#endif
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#ifndef ROOT_RDONLY
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#define ROOT_RDONLY 1
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#endif
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.code16
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.section ".bstext", "ax"
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.global bootsect_start
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bootsect_start:
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# Normalize the start address
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ljmp $BOOTSEG, $start2
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start2:
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movw %cs, %ax
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %ss
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xorw %sp, %sp
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sti
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cld
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movw $bugger_off_msg, %si
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msg_loop:
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lodsb
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andb %al, %al
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jz bs_die
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movb $0xe, %ah
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movw $7, %bx
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int $0x10
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jmp msg_loop
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bs_die:
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# Allow the user to press a key, then reboot
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xorw %ax, %ax
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int $0x16
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int $0x19
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# int 0x19 should never return. In case it does anyway,
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# invoke the BIOS reset code...
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ljmp $0xf000,$0xfff0
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.section ".bsdata", "a"
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bugger_off_msg:
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.ascii "Direct booting from floppy is no longer supported.\r\n"
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.ascii "Please use a boot loader program instead.\r\n"
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.ascii "\n"
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.ascii "Remove disk and press any key to reboot . . .\r\n"
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.byte 0
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# Kernel attributes; used by setup. This is part 1 of the
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# header, from the old boot sector.
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.section ".header", "a"
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.globl hdr
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hdr:
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setup_sects: .byte 0 /* Filled in by build.c */
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root_flags: .word ROOT_RDONLY
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syssize: .long 0 /* Filled in by build.c */
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ram_size: .word 0 /* Obsolete */
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vid_mode: .word SVGA_MODE
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root_dev: .word 0 /* Filled in by build.c */
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boot_flag: .word 0xAA55
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# offset 512, entry point
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.globl _start
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_start:
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# Explicitly enter this as bytes, or the assembler
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# tries to generate a 3-byte jump here, which causes
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# everything else to push off to the wrong offset.
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.byte 0xeb # short (2-byte) jump
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.byte start_of_setup-1f
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1:
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# Part 2 of the header, from the old setup.S
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.ascii "HdrS" # header signature
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.word 0x020a # header version number (>= 0x0105)
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# or else old loadlin-1.5 will fail)
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.globl realmode_swtch
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realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
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start_sys_seg: .word SYSSEG # obsolete and meaningless, but just
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# in case something decided to "use" it
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.word kernel_version-512 # pointing to kernel version string
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# above section of header is compatible
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# with loadlin-1.5 (header v1.5). Don't
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# change it.
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type_of_loader: .byte 0 # 0 means ancient bootloader, newer
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# bootloaders know to change this.
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# See Documentation/i386/boot.txt for
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# assigned ids
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# flags, unused bits must be zero (RFU) bit within loadflags
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loadflags:
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LOADED_HIGH = 1 # If set, the kernel is loaded high
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CAN_USE_HEAP = 0x80 # If set, the loader also has set
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# heap_end_ptr to tell how much
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# space behind setup.S can be used for
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# heap purposes.
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# Only the loader knows what is free
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.byte LOADED_HIGH
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setup_move_size: .word 0x8000 # size to move, when setup is not
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# loaded at 0x90000. We will move setup
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# to 0x90000 then just before jumping
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# into the kernel. However, only the
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# loader knows how much data behind
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# us also needs to be loaded.
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code32_start: # here loaders can put a different
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# start address for 32-bit code.
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.long 0x100000 # 0x100000 = default for big kernel
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ramdisk_image: .long 0 # address of loaded ramdisk image
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# Here the loader puts the 32-bit
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# address where it loaded the image.
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# This only will be read by the kernel.
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ramdisk_size: .long 0 # its size in bytes
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bootsect_kludge:
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.long 0 # obsolete
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heap_end_ptr: .word _end+STACK_SIZE-512
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# (Header version 0x0201 or later)
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# space from here (exclusive) down to
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# end of setup code can be used by setup
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# for local heap purposes.
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ext_loader_ver:
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.byte 0 # Extended boot loader version
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ext_loader_type:
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.byte 0 # Extended boot loader type
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cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
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# If nonzero, a 32-bit pointer
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# to the kernel command line.
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# The command line should be
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# located between the start of
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# setup and the end of low
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# memory (0xa0000), or it may
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# get overwritten before it
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# gets read. If this field is
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# used, there is no longer
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# anything magical about the
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# 0x90000 segment; the setup
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# can be located anywhere in
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# low memory 0x10000 or higher.
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ramdisk_max: .long 0x7fffffff
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# (Header version 0x0203 or later)
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# The highest safe address for
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# the contents of an initrd
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# The current kernel allows up to 4 GB,
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# but leave it at 2 GB to avoid
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# possible bootloader bugs.
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kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment
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#required for protected mode
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#kernel
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#ifdef CONFIG_RELOCATABLE
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relocatable_kernel: .byte 1
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#else
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relocatable_kernel: .byte 0
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#endif
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min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment
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pad3: .word 0
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cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line,
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#added with boot protocol
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#version 2.06
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hardware_subarch: .long 0 # subarchitecture, added with 2.07
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# default to 0 for normal x86 PC
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hardware_subarch_data: .quad 0
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payload_offset: .long ZO_input_data
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payload_length: .long ZO_z_input_len
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setup_data: .quad 0 # 64-bit physical pointer to
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# single linked list of
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# struct setup_data
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pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr
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#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset)
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#define VO_INIT_SIZE (VO__end - VO__text)
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#if ZO_INIT_SIZE > VO_INIT_SIZE
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#define INIT_SIZE ZO_INIT_SIZE
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#else
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#define INIT_SIZE VO_INIT_SIZE
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#endif
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init_size: .long INIT_SIZE # kernel initialization size
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# End of setup header #####################################################
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.section ".entrytext", "ax"
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start_of_setup:
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#ifdef SAFE_RESET_DISK_CONTROLLER
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# Reset the disk controller.
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movw $0x0000, %ax # Reset disk controller
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movb $0x80, %dl # All disks
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int $0x13
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#endif
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# Force %es = %ds
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movw %ds, %ax
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movw %ax, %es
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cld
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# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
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# which happened to work by accident for the old code. Recalculate the stack
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# pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the
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# stack behind its own code, so we can't blindly put it directly past the heap.
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movw %ss, %dx
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cmpw %ax, %dx # %ds == %ss?
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movw %sp, %dx
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je 2f # -> assume %sp is reasonably set
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# Invalid %ss, make up a new stack
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movw $_end, %dx
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testb $CAN_USE_HEAP, loadflags
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jz 1f
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movw heap_end_ptr, %dx
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1: addw $STACK_SIZE, %dx
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jnc 2f
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xorw %dx, %dx # Prevent wraparound
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2: # Now %dx should point to the end of our stack space
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andw $~3, %dx # dword align (might as well...)
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jnz 3f
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movw $0xfffc, %dx # Make sure we're not zero
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3: movw %ax, %ss
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movzwl %dx, %esp # Clear upper half of %esp
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sti # Now we should have a working stack
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# We will have entered with %cs = %ds+0x20, normalize %cs so
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# it is on par with the other segments.
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pushw %ds
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pushw $6f
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lretw
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6:
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# Check signature at end of setup
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cmpl $0x5a5aaa55, setup_sig
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jne setup_bad
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# Zero the bss
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movw $__bss_start, %di
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movw $_end+3, %cx
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xorl %eax, %eax
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subw %di, %cx
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shrw $2, %cx
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rep; stosl
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# Jump to C code (should not return)
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calll main
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# Setup corrupt somehow...
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setup_bad:
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movl $setup_corrupt, %eax
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calll puts
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# Fall through...
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.globl die
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.type die, @function
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die:
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hlt
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jmp die
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.size die, .-die
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.section ".initdata", "a"
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setup_corrupt:
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.byte 7
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.string "No setup signature found...\n"
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