Arm结构下 kernel是如何编译出zImage的。

make -f scripts/Makefile.build obj=arch/arm/boot MACHINE=arch/arm/mach-s3c6400/ arch/arm/boot/zImage

先是将vmlinux的某些段去掉了，生成了Image，比如.comment。

arm-linux-objcopy -O binary -R .note -R .note.gnu.build-id -R .comment -S vmlinux arch/arm/boot/Image
Kernel: arch/arm/boot/Image is ready

然后用gzip压缩Image，成为piggy.gz。

gzip -f -9 < arch/arm/boot/compressed/../Image > arch/arm/boot/compressed/piggy.gz
GZIP arch/arm/boot/compressed/piggy.gz

这个生成piggy.o这么长？先是从piggy.S编译出来一个piggy.o。

arm-linux-gcc -Wp,-MD,arch/arm/boot/compressed/.piggy.o.d -nostdinc -isystem

/home/wyang2/test/usr/local/arm/4.4.1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/include -D__KERNEL__-Iinclude-I/home/wyang2/test/linux-2.6.28.6/arch/arm/include -include include/linux/autoconf.h -mlittle-endian

-Iarch/arm/mach-s3c6400/include-Iarch/arm/mach-s3c6410/include-Iarch/arm/plat-s3c64xx/include

-Iarch/arm/plat-s3c/include -D__ASSEMBLY__ -mabi=aapcs-linux -mno-thumb-interwork -D__LINUX_ARM_ARCH__=6 -march=armv6k -mtune=arm1136j-s -msoft-float -gdwarf-2 -Wa,-march=all -c -o arch/arm/boot/compressed/piggy.o arch/arm/boot/compressed/piggy.S

AS arch/arm/boot/compressed/piggy.o

话说我一直没找到piggy.o和piggy.gz的关系，原来在piggy.S文件里面。它把整个piggy.gz包含进去了，嚣张啊。

.section .piggydata,#alloc

.globl input_data

input_data:

.incbin "arch/arm/boot/compressed/piggy.gz"

.globl input_data_end

input_data_end:
下面是编译head.o， 没有看出有什么特别的地方
arm-linux-gcc -Wp,-MD,arch/arm/boot/compressed/.head.o.d -nostdinc -isystem

/home/wyang2/test/usr/local/arm/4.4.1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/include -D__KERNEL__
-Iinclude -I/home/wyang2/test/linux-2.6.28.6/arch/arm/include -include include/linux/autoconf.h
-mlittle-endian -Iarch/arm/mach-s3c6400/include -Iarch/arm/mach-s3c6410/include -Iarch/arm/plat-s3c64xx/include
-Iarch/arm/plat-s3c/include -D__ASSEMBLY__ -mabi=aapcs-linux -mno-thumb-interwork
-D__LINUX_ARM_ARCH__=6 -march=armv6k -mtune=arm1136j-s -msoft-float -gdwarf-2 -Wa,-march=all
-c -o arch/arm/boot/compressed/head.o arch/arm/boot/compressed/head.S
AS arch/arm/boot/compressed/head.o

下面是编译misc.o这个老长了
arm-linux-gcc -Wp,-MD,arch/arm/boot/compressed/.misc.o.d -nostdinc -isystem

/home/wyang2/test/usr/local/arm/4.4.1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/include

-D__KERNEL__ -Iinclude -I/home/wyang2/test/linux-2.6.28.6/arch/arm/include

-include include/linux/autoconf.h -mlittle-endian -Iarch/arm/mach-s3c6400/include

-Iarch/arm/mach-s3c6410/include -Iarch/arm/plat-s3c64xx/include -Iarch/arm/plat-s3c/include

-Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common

-Werror-implicit-function-declaration -Os -marm -fno-omit-frame-pointer -mapcs -mno-sched-prolog
-mabi=aapcs-linux -mno-thumb-interwork -D__LINUX_ARM_ARCH__=6 -march=armv6k -mtune=arm1136j-s
-msoft-float -Uarm -Wframe-larger-than=1024 -fno-stack-protector -fno-omit-frame-pointer

-fno-optimize-sibling-calls -g -Wdeclaration-after-statement -Wno-pointer-sign -fpic -fno-builtin -Dstatic=

-D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(misc)" -D"KBUILD_MODNAME=KBUILD_STR(misc)"

-c -o arch/arm/boot/compressed/misc.o arch/arm/boot/compressed/misc.c
;

CC arch/arm/boot/compressed/misc.o

根据head.o piggy.o misc.o 编译成compressed/vmlinux

arm-linux-ld -EL --defsym zreladdr=0x50008000 --defsym params_phys=0x50000100 -p --no-undefined -X /usr/local/arm/4.4.1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/libgcc.a -T arch/arm/boot/compressed/vmlinux.ldsarch/arm/boot/compressed/head.oarch/arm/boot/compressed/piggy.oarch/arm/boot/compressed/misc.o-o arch/arm/boot/compressed/vmlinux
LD arch/arm/boot/compressed/vmlinux