diff options
Diffstat (limited to 'arch/x86/boot/header.S')
| -rw-r--r-- | arch/x86/boot/header.S | 283 |
1 files changed, 283 insertions, 0 deletions
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S new file mode 100644 index 00000000000..f3140e596d4 --- /dev/null +++ b/arch/x86/boot/header.S @@ -0,0 +1,283 @@ +/* + * header.S + * + * Copyright (C) 1991, 1992 Linus Torvalds + * + * Based on bootsect.S and setup.S + * modified by more people than can be counted + * + * Rewritten as a common file by H. Peter Anvin (Apr 2007) + * + * BIG FAT NOTE: We're in real mode using 64k segments. Therefore segment + * addresses must be multiplied by 16 to obtain their respective linear + * addresses. To avoid confusion, linear addresses are written using leading + * hex while segment addresses are written as segment:offset. + * + */ + +#include <asm/segment.h> +#include <linux/utsrelease.h> +#include <asm/boot.h> +#include <asm/e820.h> +#include <asm/page.h> +#include <asm/setup.h> +#include "boot.h" + +SETUPSECTS = 4 /* default nr of setup-sectors */ +BOOTSEG = 0x07C0 /* original address of boot-sector */ +SYSSEG = DEF_SYSSEG /* system loaded at 0x10000 (65536) */ +SYSSIZE = DEF_SYSSIZE /* system size: # of 16-byte clicks */ + /* to be loaded */ +ROOT_DEV = 0 /* ROOT_DEV is now written by "build" */ +SWAP_DEV = 0 /* SWAP_DEV is now written by "build" */ + +#ifndef SVGA_MODE +#define SVGA_MODE ASK_VGA +#endif + +#ifndef RAMDISK +#define RAMDISK 0 +#endif + +#ifndef ROOT_RDONLY +#define ROOT_RDONLY 1 +#endif + + .code16 + .section ".bstext", "ax" + + .global bootsect_start +bootsect_start: + + # Normalize the start address + ljmp $BOOTSEG, $start2 + +start2: + movw %cs, %ax + movw %ax, %ds + movw %ax, %es + movw %ax, %ss + xorw %sp, %sp + sti + cld + + movw $bugger_off_msg, %si + +msg_loop: + lodsb + andb %al, %al + jz bs_die + movb $0xe, %ah + movw $7, %bx + int $0x10 + jmp msg_loop + +bs_die: + # Allow the user to press a key, then reboot + xorw %ax, %ax + int $0x16 + int $0x19 + + # int 0x19 should never return. In case it does anyway, + # invoke the BIOS reset code... + ljmp $0xf000,$0xfff0 + + .section ".bsdata", "a" +bugger_off_msg: + .ascii "Direct booting from floppy is no longer supported.\r\n" + .ascii "Please use a boot loader program instead.\r\n" + .ascii "\n" + .ascii "Remove disk and press any key to reboot . . .\r\n" + .byte 0 + + + # Kernel attributes; used by setup. This is part 1 of the + # header, from the old boot sector. + + .section ".header", "a" + .globl hdr +hdr: +setup_sects: .byte SETUPSECTS +root_flags: .word ROOT_RDONLY +syssize: .long SYSSIZE +ram_size: .word RAMDISK +vid_mode: .word SVGA_MODE +root_dev: .word ROOT_DEV +boot_flag: .word 0xAA55 + + # offset 512, entry point + + .globl _start +_start: + # Explicitly enter this as bytes, or the assembler + # tries to generate a 3-byte jump here, which causes + # everything else to push off to the wrong offset. + .byte 0xeb # short (2-byte) jump + .byte start_of_setup-1f +1: + + # Part 2 of the header, from the old setup.S + + .ascii "HdrS" # header signature + .word 0x0206 # header version number (>= 0x0105) + # or else old loadlin-1.5 will fail) + .globl realmode_swtch +realmode_swtch: .word 0, 0 # default_switch, SETUPSEG +start_sys_seg: .word SYSSEG + .word kernel_version-512 # pointing to kernel version string + # above section of header is compatible + # with loadlin-1.5 (header v1.5). Don't + # change it. + +type_of_loader: .byte 0 # = 0, old one (LILO, Loadlin, + # Bootlin, SYSLX, bootsect...) + # See Documentation/i386/boot.txt for + # assigned ids + +# flags, unused bits must be zero (RFU) bit within loadflags +loadflags: +LOADED_HIGH = 1 # If set, the kernel is loaded high +CAN_USE_HEAP = 0x80 # If set, the loader also has set + # heap_end_ptr to tell how much + # space behind setup.S can be used for + # heap purposes. + # Only the loader knows what is free +#ifndef __BIG_KERNEL__ + .byte 0 +#else + .byte LOADED_HIGH +#endif + +setup_move_size: .word 0x8000 # size to move, when setup is not + # loaded at 0x90000. We will move setup + # to 0x90000 then just before jumping + # into the kernel. However, only the + # loader knows how much data behind + # us also needs to be loaded. + +code32_start: # here loaders can put a different + # start address for 32-bit code. +#ifndef __BIG_KERNEL__ + .long 0x1000 # 0x1000 = default for zImage +#else + .long 0x100000 # 0x100000 = default for big kernel +#endif + +ramdisk_image: .long 0 # address of loaded ramdisk image + # Here the loader puts the 32-bit + # address where it loaded the image. + # This only will be read by the kernel. + +ramdisk_size: .long 0 # its size in bytes + +bootsect_kludge: + .long 0 # obsolete + +heap_end_ptr: .word _end+1024 # (Header version 0x0201 or later) + # space from here (exclusive) down to + # end of setup code can be used by setup + # for local heap purposes. + +pad1: .word 0 +cmd_line_ptr: .long 0 # (Header version 0x0202 or later) + # If nonzero, a 32-bit pointer + # to the kernel command line. + # The command line should be + # located between the start of + # setup and the end of low + # memory (0xa0000), or it may + # get overwritten before it + # gets read. If this field is + # used, there is no longer + # anything magical about the + # 0x90000 segment; the setup + # can be located anywhere in + # low memory 0x10000 or higher. + +ramdisk_max: .long (-__PAGE_OFFSET-(512 << 20)-1) & 0x7fffffff + # (Header version 0x0203 or later) + # The highest safe address for + # the contents of an initrd + +kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment + #required for protected mode + #kernel +#ifdef CONFIG_RELOCATABLE +relocatable_kernel: .byte 1 +#else +relocatable_kernel: .byte 0 +#endif +pad2: .byte 0 +pad3: .word 0 + +cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line, + #added with boot protocol + #version 2.06 + +# End of setup header ##################################################### + + .section ".inittext", "ax" +start_of_setup: +#ifdef SAFE_RESET_DISK_CONTROLLER +# Reset the disk controller. + movw $0x0000, %ax # Reset disk controller + movb $0x80, %dl # All disks + int $0x13 +#endif + +# We will have entered with %cs = %ds+0x20, normalize %cs so +# it is on par with the other segments. + pushw %ds + pushw $setup2 + lretw + +setup2: +# Force %es = %ds + movw %ds, %ax + movw %ax, %es + cld + +# Stack paranoia: align the stack and make sure it is good +# for both 16- and 32-bit references. In particular, if we +# were meant to have been using the full 16-bit segment, the +# caller might have set %sp to zero, which breaks %esp-based +# references. + andw $~3, %sp # dword align (might as well...) + jnz 1f + movw $0xfffc, %sp # Make sure we're not zero +1: movzwl %sp, %esp # Clear upper half of %esp + sti + +# Check signature at end of setup + cmpl $0x5a5aaa55, setup_sig + jne setup_bad + +# Zero the bss + movw $__bss_start, %di + movw $_end+3, %cx + xorl %eax, %eax + subw %di, %cx + shrw $2, %cx + rep; stosl + +# Jump to C code (should not return) + calll main + +# Setup corrupt somehow... +setup_bad: + movl $setup_corrupt, %eax + calll puts + # Fall through... + + .globl die + .type die, @function +die: + hlt + jmp die + + .size die, .-die + + .section ".initdata", "a" +setup_corrupt: + .byte 7 + .string "No setup signature found...\n" |