Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*
 *      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   0x0207          # 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+STACK_SIZE-512
                                        # (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

hardware_subarch:       .long 0                 # subarchitecture, added with 2.07
                                                # default to 0 for normal x86 PC

hardware_subarch_data:  .quad 0

# 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

# Force %es = %ds
        movw    %ds, %ax
        movw    %ax, %es
        cld

# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
# which happened to work by accident for the old code.  Recalculate the stack
# pointer if %ss is invalid.  Otherwise leave it alone, LOADLIN sets up the
# stack behind its own code, so we can't blindly put it directly past the heap.

        movw    %ss, %dx
        cmpw    %ax, %dx        # %ds == %ss?
        movw    %sp, %dx
        je      2f              # -> assume %sp is reasonably set

        # Invalid %ss, make up a new stack
        movw    $_end, %dx
        testb   $CAN_USE_HEAP, loadflags
        jz      1f
        movw    heap_end_ptr, %dx
1:      addw    $STACK_SIZE, %dx
        jnc     2f
        xorw    %dx, %dx        # Prevent wraparound

2:      # Now %dx should point to the end of our stack space
        andw    $~3, %dx        # dword align (might as well...)
        jnz     3f
        movw    $0xfffc, %dx    # Make sure we're not zero
3:      movw    %ax, %ss
        movzwl  %dx, %esp       # Clear upper half of %esp
        sti                     # Now we should have a working stack

# We will have entered with %cs = %ds+0x20, normalize %cs so
# it is on par with the other segments.
        pushw   %ds
        pushw   $6f
        lretw
6:

# 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"