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diff --git a/gpxe/src/arch/i386/prefix/bImageprefix.S b/gpxe/src/arch/i386/prefix/bImageprefix.S
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-/*
- Copyright (C) 2000, Entity Cyber, Inc.
-
- Authors: Gary Byers (gb@thinguin.org)
- Marty Connor (mdc@thinguin.org)
- Eric Biederman (ebiederman@lnxi.com)
-
- This code also derives a lot from arch/i386/boot/setup.S in
- the linux kernel.
-
- This software may be used and distributed according to the terms
- of the GNU Public License (GPL), incorporated herein by reference.
-
- Description:
-
- This is just a little bit of code and data that can get prepended
- to an Etherboot ROM image in order to allow LILO to load the
- result as if it were a Linux kernel image.
-
- A real Linux kernel image consists of a one-sector boot loader
- (to load the image from a floppy disk), followed a few sectors
- of setup code, followed by the kernel code itself. There's
- a table in the first sector (starting at offset 497) that indicates
- how many sectors of setup code follow the first sector and which
- contains some other parameters that aren't interesting in this
- case.
-
- When LILO loads the sectors that comprise a kernel image, it doesn't
- execute the code in the first sector (since that code would try to
- load the image from a floppy disk.) The code in the first sector
- below doesn't expect to get executed (and prints an error message
- if it ever -is- executed.) LILO's only interested in knowing the
- number of setup sectors advertised in the table (at offset 497 in
- the first sector.)
-
- Etherboot doesn't require much in the way of setup code.
- Historically, the Linux kernel required at least 4 sectors of
- setup code. Current versions of LILO look at the byte at
- offset 497 in the first sector to indicate how many sectors
- of setup code are contained in the image.
-
- The setup code that is present here does a lot of things
- exactly the way the linux kernel does them instead of in
- ways more typical of etherboot. Generally this is so
- the code can be strongly compatible with the linux kernel.
- In addition the general etherboot technique of enabling the a20
- after we switch into protected mode does not work if etherboot
- is being loaded at 1MB.
-*/
-
- .equ CR0_PE,1
-
-#ifdef GAS291
-#define DATA32 data32;
-#define ADDR32 addr32;
-#define LJMPI(x) ljmp x
-#else
-#define DATA32 data32
-#define ADDR32 addr32
-/* newer GAS295 require #define LJMPI(x) ljmp *x */
-#define LJMPI(x) ljmp x
-#endif
-
-/* Simple and small GDT entries for booting only */
-#define GDT_ENTRY_BOOT_CS 2
-#define GDT_ENTRY_BOOT_DS (GDT_ENTRY_BOOT_CS + 1)
-#define __BOOT_CS (GDT_ENTRY_BOOT_CS * 8)
-#define __BOOT_DS (GDT_ENTRY_BOOT_DS * 8)
-
-
-#define SETUPSECS 4 /* Minimal nr of setup-sectors */
-#define PREFIXSIZE ((SETUPSECS+1)*512)
-#define PREFIXPGH (PREFIXSIZE / 16 )
-#define BOOTSEG 0x07C0 /* original address of boot-sector */
-#define INITSEG 0x9000 /* we move boot here - out of the way */
-#define SETUPSEG 0x9020 /* setup starts here */
-#define SYSSEG 0x1000 /* system loaded at 0x10000 (65536). */
-
-#define DELTA_INITSEG (SETUPSEG - INITSEG) /* 0x0020 */
-
-/* Signature words to ensure LILO loaded us right */
-#define SIG1 0xAA55
-#define SIG2 0x5A5A
-
- .text
- .code16
- .arch i386
- .org 0
- .section ".prefix", "ax", @progbits
-_prefix:
-
-/*
- This is a minimal boot sector. If anyone tries to execute it (e.g., if
- a .lkrn file is dd'ed to a floppy), print an error message.
-*/
-
-bootsector:
- jmp $BOOTSEG, $go - _prefix /* reload cs:ip to match relocation addr */
-go:
- movw $0x2000, %di /* 0x2000 is arbitrary value >= length
- of bootsect + room for stack */
-
- movw $BOOTSEG, %ax
- movw %ax,%ds
- movw %ax,%es
-
- cli
- movw %ax, %ss /* put stack at BOOTSEG:0x2000. */
- movw %di,%sp
- sti
-
- movw $why_end-why, %cx
- movw $why - _prefix, %si
-
- movw $0x0007, %bx /* page 0, attribute 7 (normal) */
- movb $0x0e, %ah /* write char, tty mode */
-prloop:
- lodsb
- int $0x10
- loop prloop
-freeze: jmp freeze
-
-why: .ascii "This image cannot be loaded from a floppy disk.\r\n"
-why_end:
-
-
- .org 497
-setup_sects:
- .byte SETUPSECS
-root_flags:
- .word 0
-syssize:
- .word _verbatim_size_pgh - PREFIXPGH
-swap_dev:
- .word 0
-ram_size:
- .word 0
-vid_mode:
- .word 0
-root_dev:
- .word 0
-boot_flag:
- .word 0xAA55
-
-/*
- We're now at the beginning of the second sector of the image -
- where the setup code goes.
-
- We don't need to do too much setup for Etherboot.
-
- This code gets loaded at SETUPSEG:0. It wants to start
- executing the Etherboot image that's loaded at SYSSEG:0 and
- whose entry point is SYSSEG:0.
-*/
-setup_code:
- jmp trampoline
-# This is the setup header, and it must start at %cs:2 (old 0x9020:2)
-
- .ascii "HdrS" # header signature
- .word 0x0203 # header version number (>= 0x0105)
- # or else old loadlin-1.5 will fail)
-realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
-start_sys_seg: .word SYSSEG # low load segment (obsolete)
- .word kernel_version - setup_code
- # 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
- .byte LOADED_HIGH
-
-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.
- .long 0x100000 # 0x100000 = default for big kernel
-
-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 0 # (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 0 # (Header version 0x0203 or later)
- # The highest safe address for
- # the contents of an initrd
-
-trampoline: call start_of_setup
-trampoline_end:
- .space 1024
-# End of setup header #####################################################
-
-start_of_setup:
-# Set %ds = %cs, we know that SETUPSEG = %cs at this point
- movw %cs, %ax # aka SETUPSEG
- movw %ax, %ds
-# Check signature at end of setup
- cmpw $SIG1, (setup_sig1 - setup_code)
- jne bad_sig
-
- cmpw $SIG2, (setup_sig2 - setup_code)
- jne bad_sig
-
- jmp good_sig1
-
-# Routine to print asciiz string at ds:si
-prtstr:
- lodsb
- andb %al, %al
- jz fin
-
- call prtchr
- jmp prtstr
-
-fin: ret
-
-# Part of above routine, this one just prints ascii al
-prtchr: pushw %ax
- pushw %cx
- movw $7,%bx
- movw $0x01, %cx
- movb $0x0e, %ah
- int $0x10
- popw %cx
- popw %ax
- ret
-
-no_sig_mess: .string "No setup signature found ..."
-
-good_sig1:
- jmp good_sig
-
-# We now have to find the rest of the setup code/data
-bad_sig:
- movw %cs, %ax # SETUPSEG
- subw $DELTA_INITSEG, %ax # INITSEG
- movw %ax, %ds
- xorb %bh, %bh
- movb (497), %bl # get setup sect from bootsect
- subw $4, %bx # LILO loads 4 sectors of setup
- shlw $8, %bx # convert to words (1sect=2^8 words)
- movw %bx, %cx
- shrw $3, %bx # convert to segment
- addw $SYSSEG, %bx
- movw %bx, %cs:(start_sys_seg - setup_code)
-# Move rest of setup code/data to here
- movw $2048, %di # four sectors loaded by LILO
- subw %si, %si
- pushw %cs
- popw %es
- movw $SYSSEG, %ax
- movw %ax, %ds
- rep
- movsw
- movw %cs, %ax # aka SETUPSEG
- movw %ax, %ds
- cmpw $SIG1, (setup_sig1 - setup_code)
- jne no_sig
-
- cmpw $SIG2, (setup_sig2 - setup_code)
- jne no_sig
-
- jmp good_sig
-
-no_sig:
- lea (no_sig_mess - setup_code), %si
- call prtstr
-
-no_sig_loop:
- hlt
- jmp no_sig_loop
-
-good_sig:
- cmpw $0, %cs:(realmode_swtch - setup_code)
- jz rmodeswtch_normal
-
- lcall *%cs:(realmode_swtch - setup_code)
- jmp rmodeswtch_end
-
-rmodeswtch_normal:
- pushw %cs
- call default_switch
-
-rmodeswtch_end:
-# we get the code32 start address and modify the below 'jmpi'
-# (loader may have changed it)
- movl %cs:(code32_start - setup_code), %eax
- movl %eax, %cs:(code32 - setup_code)
-
-# then we load the segment descriptors
- movw %cs, %ax # aka SETUPSEG
- movw %ax, %ds
-
-#
-# Enable A20. This is at the very best an annoying procedure.
-# A20 code ported from SYSLINUX 1.52-1.63 by H. Peter Anvin.
-#
-
-A20_TEST_LOOPS = 32 # Iterations per wait
-A20_ENABLE_LOOPS = 255 # Total loops to try
-
-a20_try_loop:
-
- # First, see if we are on a system with no A20 gate.
-a20_none:
- call a20_test
- jnz a20_done
-
- # Next, try the BIOS (INT 0x15, AX=0x2401)
-a20_bios:
- movw $0x2401, %ax
- pushfl # Be paranoid about flags
- int $0x15
- popfl
-
- call a20_test
- jnz a20_done
-
- # Try enabling A20 through the keyboard controller
-a20_kbc:
- call empty_8042
-
- call a20_test # Just in case the BIOS worked
- jnz a20_done # but had a delayed reaction.
-
- movb $0xD1, %al # command write
- outb %al, $0x64
- call empty_8042
-
- movb $0xDF, %al # A20 on
- outb %al, $0x60
- call empty_8042
-
- # Wait until a20 really *is* enabled; it can take a fair amount of
- # time on certain systems; Toshiba Tecras are known to have this
- # problem.
-a20_kbc_wait:
- xorw %cx, %cx
-a20_kbc_wait_loop:
- call a20_test
- jnz a20_done
- loop a20_kbc_wait_loop
-
- # Final attempt: use "configuration port A"
-a20_fast:
- inb $0x92, %al # Configuration Port A
- orb $0x02, %al # "fast A20" version
- andb $0xFE, %al # don't accidentally reset
- outb %al, $0x92
-
- # Wait for configuration port A to take effect
-a20_fast_wait:
- xorw %cx, %cx
-a20_fast_wait_loop:
- call a20_test
- jnz a20_done
- loop a20_fast_wait_loop
-
- # A20 is still not responding. Try frobbing it again.
- #
- decb (a20_tries - setup_code)
- jnz a20_try_loop
-
- movw $(a20_err_msg - setup_code), %si
- call prtstr
-
-a20_die:
- hlt
- jmp a20_die
-
-a20_tries:
- .byte A20_ENABLE_LOOPS
-
-a20_err_msg:
- .ascii "linux: fatal error: A20 gate not responding!"
- .byte 13, 10, 0
-
- # If we get here, all is good
-a20_done:
- # Leave the idt alone
-
- # set up gdt
- xorl %eax, %eax # Compute gdt_base
- movw %ds, %ax # (Convert %ds:gdt to a linear ptr)
- shll $4, %eax
- addl $(bImage_gdt - setup_code), %eax
- movl %eax, (bImage_gdt_48+2 - setup_code)
- DATA32 lgdt %ds:(bImage_gdt_48 - setup_code) # load gdt with whatever is
- # appropriate
-
- # Switch to protected mode
- movl %cr0, %eax
- orb $CR0_PE, %al
- movl %eax, %cr0
-
- DATA32 ljmp *%ds:(code32 - setup_code)
-code32:
- .long 0x100000
- .word __BOOT_CS, 0
-
-# Here's a bunch of information about your current kernel..
-kernel_version: .ascii "Etherboot "
- .ascii VERSION
- .byte 0
-
-# This is the default real mode switch routine.
-# to be called just before protected mode transition
-default_switch:
- cli # no interrupts allowed !
- movb $0x80, %al # disable NMI for bootup
- # sequence
- outb %al, $0x70
- lret
-
-# This routine tests whether or not A20 is enabled. If so, it
-# exits with zf = 0.
-#
-# The memory address used, 0x200, is the int $0x80 vector, which
-# should be safe.
-
-A20_TEST_ADDR = 4*0x80
-
-a20_test:
- pushw %cx
- pushw %ax
- xorw %cx, %cx
- movw %cx, %fs # Low memory
- decw %cx
- movw %cx, %gs # High memory area
- movw $A20_TEST_LOOPS, %cx
- movw %fs:(A20_TEST_ADDR), %ax
- pushw %ax
-a20_test_wait:
- incw %ax
- movw %ax, %fs:(A20_TEST_ADDR)
- call delay # Serialize and make delay constant
- cmpw %gs:(A20_TEST_ADDR+0x10), %ax
- loope a20_test_wait
-
- popw %fs:(A20_TEST_ADDR)
- popw %ax
- popw %cx
- ret
-
-
-# This routine checks that the keyboard command queue is empty
-# (after emptying the output buffers)
-#
-# Some machines have delusions that the keyboard buffer is always full
-# with no keyboard attached...
-#
-# If there is no keyboard controller, we will usually get 0xff
-# to all the reads. With each IO taking a microsecond and
-# a timeout of 100,000 iterations, this can take about half a
-# second ("delay" == outb to port 0x80). That should be ok,
-# and should also be plenty of time for a real keyboard controller
-# to empty.
-#
-
-empty_8042:
- pushl %ecx
- movl $100000, %ecx
-
-empty_8042_loop:
- decl %ecx
- jz empty_8042_end_loop
-
- call delay
-
- inb $0x64, %al # 8042 status port
- testb $1, %al # output buffer?
- jz no_output
-
- call delay
- inb $0x60, %al # read it
- jmp empty_8042_loop
-
-no_output:
- testb $2, %al # is input buffer full?
- jnz empty_8042_loop # yes - loop
-empty_8042_end_loop:
- popl %ecx
-
-
-# Delay is needed after doing I/O
-delay:
- outb %al,$0x80
- ret
-
-# Descriptor tables
-#
-# NOTE: The intel manual says gdt should be sixteen bytes aligned for
-# efficiency reasons. However, there are machines which are known not
-# to boot with misaligned GDTs, so alter this at your peril! If you alter
-# GDT_ENTRY_BOOT_CS (in asm/segment.h) remember to leave at least two
-# empty GDT entries (one for NULL and one reserved).
-#
-# NOTE: On some CPUs, the GDT must be 8 byte aligned. This is
-# true for the Voyager Quad CPU card which will not boot without
-# This directive. 16 byte aligment is recommended by intel.
-#
- .balign 16
-bImage_gdt:
- .fill GDT_ENTRY_BOOT_CS,8,0
-
- .word 0xFFFF # 4Gb - (0x100000*0x1000 = 4Gb)
- .word 0 # base address = 0
- .word 0x9A00 # code read/exec
- .word 0x00CF # granularity = 4096, 386
- # (+5th nibble of limit)
-
- .word 0xFFFF # 4Gb - (0x100000*0x1000 = 4Gb)
- .word 0 # base address = 0
- .word 0x9200 # data read/write
- .word 0x00CF # granularity = 4096, 386
- # (+5th nibble of limit)
-bImage_gdt_end:
- .balign 4
-
- .word 0 # alignment byte
-bImage_idt_48:
- .word 0 # idt limit = 0
- .long 0 # idt base = 0L
-
- .word 0 # alignment byte
-bImage_gdt_48:
- .word bImage_gdt_end - bImage_gdt - 1 # gdt limit
- .long bImage_gdt_48 - setup_code # gdt base (filled in later)
-
- .section ".text16", "ax", @progbits
-prefix_exit:
- int $0x19 /* should try to boot machine */
-prefix_exit_end:
- .previous
-
-
- .org (PREFIXSIZE - 4)
-# Setup signature -- must be last
-setup_sig1: .word SIG1
-setup_sig2: .word SIG2
- /* Etherboot expects to be contiguous in memory once loaded.
- * The linux bImage protocol does not do this, but since we
- * don't need any information that's left in the prefix, it
- * doesn't matter: we just have to ensure that we make it to _start
- *
- * protected_start will live at 0x100000 and it will be the
- * the first code called as we enter protected mode.
- */
- .code32
-protected_start:
- /* Load segment registers */
- movw $__BOOT_DS, %ax
- movw %ax, %ss
- movw %ax, %ds
- movw %ax, %es
- movw %ax, %fs
- movw %ax, %gs
-
- /* Use the internal etherboot stack */
- movl $(_prefix_stack_end - protected_start + 0x100000), %esp
-
- pushl $0 /* No parameters to preserve for exit path */
- pushl $0 /* Use prefix exit path mechanism */
-
- jmp _start
-/*
- That's about it.
-*/