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+/*
+ * 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"