Assembly header and main routine for new x86 setup code
The assembly header and initialization code, and the main() routine. main.c also contains some miscellaneous very short routines. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
H. Peter Anvin
Linus Torvalds
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7052fdd890
commit
626073132b
2 changed files with 444 additions and 0 deletions
283
arch/i386/boot/header.S
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283
arch/i386/boot/header.S
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/*
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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.h>
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#include <asm/setup.h>
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#include "boot.h"
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SETUPSECTS = 4 /* default nr of setup-sectors */
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BOOTSEG = 0x07C0 /* original address of boot-sector */
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SYSSEG = DEF_SYSSEG /* system loaded at 0x10000 (65536) */
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SYSSIZE = DEF_SYSSIZE /* system size: # of 16-byte clicks */
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/* to be loaded */
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ROOT_DEV = 0 /* ROOT_DEV is now written by "build" */
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SWAP_DEV = 0 /* SWAP_DEV is now written by "build" */
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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 SETUPSECTS
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root_flags: .word ROOT_RDONLY
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syssize: .long SYSSIZE
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ram_size: .word RAMDISK
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vid_mode: .word SVGA_MODE
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root_dev: .word ROOT_DEV
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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 0x0206 # 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
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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, old one (LILO, Loadlin,
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# Bootlin, SYSLX, bootsect...)
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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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#ifndef __BIG_KERNEL__
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.byte 0
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#else
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.byte LOADED_HIGH
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#endif
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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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#ifndef __BIG_KERNEL__
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.long 0x1000 # 0x1000 = default for zImage
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#else
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.long 0x100000 # 0x100000 = default for big kernel
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#endif
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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+1024 # (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 (-__PAGE_OFFSET-(512 << 20)-1) & 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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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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# 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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# We will have entired 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 $setup2
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lretw
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setup2:
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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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# Stack paranoia: align the stack and make sure it is good
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# for both 16- and 32-bit references. In particular, if we
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# were meant to have been using the full 16-bit segment, the
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# caller might have set %sp to zero, which breaks %esp-based
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# references.
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andw $~3, %sp # dword align (might as well...)
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jnz 1f
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movw $0xfffc, %sp # Make sure we're not zero
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1: movzwl %sp, %esp # Clear upper half of %esp
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sti
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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, .-due
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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..."
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161
arch/i386/boot/main.c
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161
arch/i386/boot/main.c
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/* -*- linux-c -*- ------------------------------------------------------- *
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright 2007 rPath, Inc. - All Rights Reserved
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*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2.
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*
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* ----------------------------------------------------------------------- */
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/*
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* arch/i386/boot/main.c
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*
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* Main module for the real-mode kernel code
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*/
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#include "boot.h"
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struct boot_params boot_params __attribute__((aligned(16)));
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char *HEAP = _end;
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char *heap_end = _end; /* Default end of heap = no heap */
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/*
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* Copy the header into the boot parameter block. Since this
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* screws up the old-style command line protocol, adjust by
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* filling in the new-style command line pointer instead.
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*/
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#define OLD_CL_MAGIC 0xA33F
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#define OLD_CL_ADDRESS 0x20
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static void copy_boot_params(void)
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{
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struct old_cmdline {
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u16 cl_magic;
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u16 cl_offset;
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};
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const struct old_cmdline * const oldcmd =
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(const struct old_cmdline *)OLD_CL_ADDRESS;
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BUILD_BUG_ON(sizeof boot_params != 4096);
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memcpy(&boot_params.hdr, &hdr, sizeof hdr);
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if (!boot_params.hdr.cmd_line_ptr &&
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oldcmd->cl_magic == OLD_CL_MAGIC) {
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/* Old-style command line protocol. */
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u16 cmdline_seg;
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/* Figure out if the command line falls in the region
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of memory that an old kernel would have copied up
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to 0x90000... */
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if (oldcmd->cl_offset < boot_params.hdr.setup_move_size)
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cmdline_seg = ds();
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else
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cmdline_seg = 0x9000;
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boot_params.hdr.cmd_line_ptr =
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(cmdline_seg << 4) + oldcmd->cl_offset;
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}
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}
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/*
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* Set the keyboard repeat rate to maximum. Unclear why this
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* is done here; this might be possible to kill off as stale code.
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*/
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static void keyboard_set_repeat(void)
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{
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u16 ax = 0x0305;
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u16 bx = 0;
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asm volatile("int $0x16"
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: "+a" (ax), "+b" (bx)
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: : "ecx", "edx", "esi", "edi");
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}
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/*
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* Get Intel SpeedStep IST information.
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*/
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static void query_speedstep_ist(void)
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{
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asm("int $0x15"
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: "=a" (boot_params.speedstep_info[0]),
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"=b" (boot_params.speedstep_info[1]),
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"=c" (boot_params.speedstep_info[2]),
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"=d" (boot_params.speedstep_info[3])
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: "a" (0x0000e980), /* IST Support */
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"d" (0x47534943)); /* Request value */
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}
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/*
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* Tell the BIOS what CPU mode we intend to run in.
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*/
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static void set_bios_mode(void)
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{
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#ifdef CONFIG_X86_64
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u32 eax, ebx;
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eax = 0xec00;
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ebx = 2;
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asm volatile("int $0x15"
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: "+a" (eax), "+b" (ebx)
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: : "ecx", "edx", "esi", "edi");
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#endif
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}
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void main(void)
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{
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/* First, copy the boot header into the "zeropage" */
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copy_boot_params();
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/* End of heap check */
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if (boot_params.hdr.loadflags & CAN_USE_HEAP) {
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heap_end = (char *)(boot_params.hdr.heap_end_ptr
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+0x200-STACK_SIZE);
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} else {
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/* Boot protocol 2.00 only, no heap available */
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puts("WARNING: Ancient bootloader, some functionality "
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"may be limited!\n");
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}
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/* Make sure we have all the proper CPU support */
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if (validate_cpu()) {
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puts("Unable to boot - please use a kernel appropriate "
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"for your CPU.\n");
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die();
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}
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/* Tell the BIOS what CPU mode we intend to run in. */
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set_bios_mode();
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/* Detect memory layout */
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detect_memory();
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/* Set keyboard repeat rate (why?) */
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keyboard_set_repeat();
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/* Set the video mode */
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set_video();
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/* Query MCA information */
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query_mca();
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/* Voyager */
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#ifdef CONFIG_X86_VOYAGER
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query_voyager();
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#endif
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/* Query SpeedStep IST information */
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query_speedstep_ist();
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/* Query APM information */
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#if defined(CONFIG_APM) || defined(CONFIG_APM_MODULE)
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query_apm_bios();
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#endif
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/* Query EDD information */
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#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
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query_edd();
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#endif
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/* Do the last things and invoke protected mode */
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go_to_protected_mode();
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}
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