5e47c478b0
Impact: obsolete feature removal The zImage kernel format has been functionally unused for a very long time. It is just barely possible to build a modern kernel that still fits within the zImage size limit, but it is highly unlikely that anyone ever uses it. Furthermore, although it is still supported by most bootloaders, it has been at best poorly tested (or not tested at all); some bootloaders are even known to not support zImage at all and not having even noticed. Also remove some really obsolete constants that no longer have any meaning. LKML-Reference: <49B703D4.1000008@zytor.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
304 lines
7.6 KiB
ArmAsm
304 lines
7.6 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 "offsets.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 0x0209 # 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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pad1: .word 0
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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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pad2: .byte 0
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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 input_data
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payload_length: .long input_data_end-input_data
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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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# End of setup header #####################################################
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.section ".inittext", "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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