修改方法同bootsect.s，这里直接贴出修改后的源代码：

;
;    setup.s     (C) 1991 Linus Torvalds
;
; setup.s is responsible for getting the system data from the BIOS,
; and putting them into the appropriate places in system memory.
; both setup.s and system has been loaded by the bootblock.
;
; This code asks the bios for memory/disk/other parameters, and
; puts them in a "safe" place: 0x90000-0x901FF, ie where the
; boot-block used to be. It is then up to the protected mode
; system to read them from there before the area is overwritten
; for buffer-blocks.
;

; NOTE! These had better be the same as in bootsect.s!

INITSEG  equ 0x9000    ; we move boot here - out of the way
SYSSEG   equ 0x1000    ; system loaded at 0x10000 (65536).
SETUPSEG equ 0x9020    ; this is the current segment

start:

; ok, the read went well so we get current cursor position and save it for
; posterity.

    mov ax,INITSEG  ; this is done in bootsect already, but...
    mov ds,ax
    mov ah,0x03 ; read cursor pos
    xor bh,bh
    int 0x10        ; save it in known place, con_init fetches
    mov [0],dx      ; it from 0x90000.

; Get memory size (extended mem, kB)

    mov ah,0x88
    int 0x15
    mov [2],ax

; Get video-card data:

    mov ah,0x0f
    int 0x10
    mov [4],bx      ; bh = display page
    mov [6],ax      ; al = video mode, ah = window width

; check for EGA/VGA and some config parameters

    mov ah,0x12
    mov bl,0x10
    int 0x10
    mov [8],ax
    mov [10],bx
    mov [12],cx

; Get hd0 data

    mov ax,0x0000
    mov ds,ax
    lds si,[4*0x41]
    mov ax,INITSEG
    mov es,ax
    mov di,0x0080
    mov cx,0x10
    rep
    movsb

; Get hd1 data

    mov ax,0x0000
    mov ds,ax
    lds si,[4*0x46]
    mov ax,INITSEG
    mov es,ax
    mov di,0x0090
    mov cx,0x10
    rep
    movsb

; Check that there IS a hd1 :-)

    mov ax,0x01500
    mov dl,0x81
    int 0x13
    jc  no_disk1
    cmp ah,3
    je  is_disk1
no_disk1:
    mov ax,INITSEG
    mov es,ax
    mov di,0x0090
    mov cx,0x10
    mov ax,0x00
    rep
    stosb
is_disk1:

; now we want to move to protected mode ...

    cli         ; no interrupts allowed !

; first we move the system to it's rightful place

    mov ax,0x0000
    cld         ; 'direction'=0, movs moves forward
do_move:
    mov es,ax       ; destination segment
    add ax,0x1000
    cmp ax,0x9000
    jz  end_move
    mov ds,ax       ; source segment
    sub di,di
    sub si,si
    mov     cx,0x8000
    rep
    movsw
    jmp do_move

; then we load the segment descriptors

end_move:
    mov ax,SETUPSEG ; right, forgot this at first. didn't work :-)
    mov ds,ax
    lidt [idt_48]       ; load idt with 0,0
    lgdt [gdt_48]       ; load gdt with whatever appropriate

; that was painless, now we enable A20

    call    empty_8042
    mov al,0xD1     ; command write
    out 0x64,al
    call    empty_8042
    mov al,0xDF     ; A20 on
    out 0x60,al
    call    empty_8042

; well, that went ok, I hope. Now we have to reprogram the interrupts :-(
; we put them right after the intel-reserved hardware interrupts, at
; int 0x20-0x2F. There they won't mess up anything. Sadly IBM really
; messed this up with the original PC, and they haven't been able to
; rectify it afterwards. Thus the bios puts interrupts at 0x08-0x0f,
; which is used for the internal hardware interrupts as well. We just
; have to reprogram the 8259's, and it isn't fun.

    mov al,0x11     ; initialization sequence
    out 0x20,al     ; send it to 8259A-1
    dw  0x00eb,0x00eb       ; jmp $+2, jmp $+2
    out 0xA0,al     ; and to 8259A-2
    dw  0x00eb,0x00eb
    mov al,0x20     ; start of hardware int's (0x20)
    out 0x21,al
    dw  0x00eb,0x00eb
    mov al,0x28     ; start of hardware int's 2 (0x28)
    out 0xA1,al
    dw  0x00eb,0x00eb
    mov al,0x04     ; 8259-1 is master
    out 0x21,al
    dw  0x00eb,0x00eb
    mov al,0x02     ; 8259-2 is slave
    out 0xA1,al
    dw  0x00eb,0x00eb
    mov al,0x01     ; 8086 mode for both
    out 0x21,al
    dw  0x00eb,0x00eb
    out 0xA1,al
    dw  0x00eb,0x00eb
    mov al,0xFF     ; mask off all interrupts for now
    out 0x21,al
    dw  0x00eb,0x00eb
    out 0xA1,al

; well, that certainly wasn't fun :-(. Hopefully it works, and we don't
; need no steenking BIOS anyway (except for the initial loading :-).
; The BIOS-routine wants lots of unnecessary data, and it's less
; "interesting" anyway. This is how REAL programmers do it.
;
; Well, now's the time to actually move into protected mode. To make
; things as simple as possible, we do no register set-up or anything,
; we let the gnu-compiled 32-bit programs do that. We just jump to
; absolute address 0x00000, in 32-bit protected mode.

    mov ax,0x0001   ; protected mode (PE) bit
    lmsw    ax      ; This is it!
    jmp 8:0     ; jmp offset 0 of segment 8 (cs)

; This routine checks that the keyboard command queue is empty
; No timeout is used - if this hangs there is something wrong with
; the machine, and we probably couldn't proceed anyway.
empty_8042:
    dw  0x00eb,0x00eb
    in  al,0x64 ; 8042 status port
    test    al,2        ; is input buffer full?
    jnz empty_8042  ; yes - loop
    ret

gdt:
    dw  0,0,0,0     ; dummy

    dw  0x07FF      ; 8Mb - limit=2047 (2048*4096=8Mb)
    dw  0x0000      ; base address=0
    dw  0x9A00      ; code read/exec
    dw  0x00C0      ; granularity=4096, 386

    dw  0x07FF      ; 8Mb - limit=2047 (2048*4096=8Mb)
    dw  0x0000      ; base address=0
    dw  0x9200      ; data read/write
    dw  0x00C0      ; granularity=4096, 386

idt_48:
    dw  0           ; idt limit=0
    dw  0,0         ; idt base=0L

gdt_48:
    dw  0x800       ; gdt limit=2048, 256 GDT entries
    dw  512+gdt,0x9 ; gdt base = 0X9xxxx

下面对Makefile进行修改：

删除7-8行

AS86    =as86 -0 -a
LD86    =ld86 -0

在源码目录下创建build目录，mkdir build
修改以下内容

boot/setup: boot/setup.s
    $(AS86) -o boot/setup.o boot/setup.s
    $(LD86) -s -o boot/setup boot/setup.o

boot/bootsect:    boot/bootsect.s
    $(AS86) -o boot/bootsect.o boot/bootsect.s
    $(LD86) -s -o boot/bootsect boot/bootsect.o

为

build/bootsect.bin:    boot/bootsect.s
    nasm boot/bootsect.s -o build/bootsect.bin

build/setup.bin: boot/setup.s
    nasm boot/setup.s -o build/setup.bin

删除所有"boot/bootsect"" boot/setup"
修改内容

all:    Image

为

all: build/bootsect.bin build/setup.bin
    dd if=build/bootsect.bin of=bootimage-fd.img bs=512 count=1 conv=notrunc
    dd if=build/setup.bin of=bootimage-fd.img bs=512 seek=1 count=4 conv=notrunc    

clean后追加内容

clean:
    rm -rf build/*
    ...
    ...

修改后Makefile源码：

#
# if you want the ram-disk device, define this to be the
# size in blocks.
#
RAMDISK = #-DRAMDISK=512

AS86    =as86 -0 -a
LD86    =ld86 -0

AS    =gas
LD    =gld
LDFLAGS    =-s -x -M
CC    =gcc $(RAMDISK)
CFLAGS    =-Wall -O -fstrength-reduce -fomit-frame-pointer \
-fcombine-regs -mstring-insns
CPP    =cpp -nostdinc -Iinclude

#
# ROOT_DEV specifies the default root-device when making the image.
# This can be either FLOPPY, /dev/xxxx or empty, in which case the
# default of /dev/hd6 is used by 'build'.
#
ROOT_DEV=/dev/hd6

ARCHIVES=kernel/kernel.o mm/mm.o fs/fs.o
DRIVERS =kernel/blk_drv/blk_drv.a kernel/chr_drv/chr_drv.a
MATH    =kernel/math/math.a
LIBS    =lib/lib.a

.c.s:
    $(CC) $(CFLAGS) \
    -nostdinc -Iinclude -S -o $*.s $<
.s.o:
    $(AS) -c -o $*.o $<
.c.o:
    $(CC) $(CFLAGS) \
    -nostdinc -Iinclude -c -o $*.o $<

all: build/bootsect.bin build/setup.bin
    dd if=build/bootsect.bin of=bootimage-fd.img bs=512 count=1 conv=notrunc
    dd if=build/setup.bin of=bootimage-fd.img bs=512 seek=1 count=4 conv=notrunc    

Image: tools/system tools/build
    tools/build tools/system $(ROOT_DEV) > Image
    sync

disk: Image
    dd bs=8192 if=Image of=/dev/PS0

tools/build: tools/build.c
    $(CC) $(CFLAGS) \
    -o tools/build tools/build.c

boot/head.o: boot/head.s

tools/system:    boot/head.o init/main.o \
        $(ARCHIVES) $(DRIVERS) $(MATH) $(LIBS)
    $(LD) $(LDFLAGS) boot/head.o init/main.o \
    $(ARCHIVES) \
    $(DRIVERS) \
    $(MATH) \
    $(LIBS) \
    -o tools/system > System.map

kernel/math/math.a:
    (cd kernel/math; make)

kernel/blk_drv/blk_drv.a:
    (cd kernel/blk_drv; make)

kernel/chr_drv/chr_drv.a:
    (cd kernel/chr_drv; make)

kernel/kernel.o:
    (cd kernel; make)

mm/mm.o:
    (cd mm; make)

fs/fs.o:
    (cd fs; make)

lib/lib.a:
    (cd lib; make)

build/bootsect.bin:    boot/bootsect.s
    nasm boot/bootsect.s -o build/bootsect.bin

build/setup.bin: boot/setup.s
    nasm boot/setup.s -o build/setup.bin

tmp.s:    boot/bootsect.s tools/system
    (echo -n "SYSSIZE = (";ls -l tools/system | grep system \
        | cut -c25-31 | tr '\012' ' '; echo "+ 15 ) / 16") > tmp.s
    cat boot/bootsect.s >> tmp.s

clean:
    rm -rf build/*
    rm -f Image System.map tmp_make core
    rm -f init/*.o tools/system tools/build boot/*.o
    (cd mm;make clean)
    (cd fs;make clean)
    (cd kernel;make clean)
    (cd lib;make clean)

backup: clean
    (cd .. ; tar cf - linux | compress - > backup.Z)
    sync

dep:
    sed '/\#\#\# Dependencies/q' < Makefile > tmp_make
    (for i in init/*.c;do echo -n "init/";$(CPP) -M $$i;done) >> tmp_make
    cp tmp_make Makefile
    (cd fs; make dep)
    (cd kernel; make dep)
    (cd mm; make dep)

### Dependencies:
init/main.o : init/main.c include/unistd.h include/sys/stat.h \
  include/sys/types.h include/sys/times.h include/sys/utsname.h \
  include/utime.h include/time.h include/linux/tty.h include/termios.h \
  include/linux/sched.h include/linux/head.h include/linux/fs.h \
  include/linux/mm.h include/signal.h include/asm/system.h include/asm/io.h \
  include/stddef.h include/stdarg.h include/fcntl.h