Linux内核编译完成后会生成zImage内核镜像文件。zImage是如何解压的呢？本文将结合关键代码，讲解zImage的解压过程。还是先来看看zImage的组成吧。在内核编译完成后会在arch/arm/boot/下生成zImage。
在arch/arm/boot/Makefile中，如下代码：
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# # arch/arm/boot/Makefile # # This file is included by the global makefile so that you can add your own # architecture-specific flags and dependencies. # # This file is subject to the terms and conditions of the GNU General Public # License. See the file "COPYING" in the main directory of this archive # for more details. # # Copyright (C) 1995-2002 Russell King # MKIMAGE := $(srctree)/scripts/mkuboot.sh ifneq ($(MACHINE),) include $(srctree)/$(MACHINE)/Makefile.boot endif # Note: the following conditions must always be true: # ZRELADDR == virt_to_phys(PAGE_OFFSET + TEXT_OFFSET) # PARAMS_PHYS must be within 4MB of ZRELADDR # INITRD_PHYS must be in RAM ZRELADDR := $(zreladdr-y) PARAMS_PHYS := $(params_phys-y) INITRD_PHYS := $(initrd_phys-y) export ZRELADDR INITRD_PHYS PARAMS_PHYS targets := Image zImage xipImage bootpImage uImage ifeq ($(CONFIG_XIP_KERNEL),y) $(obj)/xipImage: vmlinux FORCE $(call if_changed,objcopy) @echo ' Kernel: $@ is ready (physical address: $(CONFIG_XIP_PHYS_ADDR))' $(obj)/Image $(obj)/zImage: FORCE @echo 'Kernel configured for XIP (CONFIG_XIP_KERNEL=y)' @echo 'Only the xipImage target is available in this case' @false else $(obj)/xipImage: FORCE @echo 'Kernel not configured for XIP (CONFIG_XIP_KERNEL!=y)' @false $(obj)/Image: vmlinux FORCE $(call if_changed,objcopy) @echo ' Kernel: $@ is ready' $(obj)/compressed/vmlinux: $(obj)/Image FORCE $(Q)$(MAKE) $(build)=$(obj)/compressed $@ $(obj)/zImage: $(obj)/compressed/vmlinux FORCE $(call if_changed,objcopy) @echo ' Kernel: $@ is ready' endif quiet_cmd_uimage = UIMAGE $@ cmd_uimage = $(CONFIG_SHELL) $(MKIMAGE) -A arm -O linux -T kernel \ -C none -a $(LOADADDR) -e $(STARTADDR) \ -n 'Linux-$(KERNELRELEASE)' -d {1}lt; $@ ifeq ($(CONFIG_ZBOOT_ROM),y) $(obj)/uImage: LOADADDR=$(CONFIG_ZBOOT_ROM_TEXT) else $(obj)/uImage: LOADADDR=$(ZRELADDR) endif $(obj)/uImage: STARTADDR=$(LOADADDR) $(obj)/uImage: $(obj)/zImage FORCE $(call if_changed,uimage) @echo ' Image $@ is ready' $(obj)/bootp/bootp: $(obj)/zImage initrd FORCE $(Q)$(MAKE) $(build)=$(obj)/bootp $@ @: $(obj)/bootpImage: $(obj)/bootp/bootp FORCE $(call if_changed,objcopy) @echo ' Kernel: $@ is ready' PHONY += initrd FORCE initrd: @test "$(INITRD_PHYS)" != "" || \ (echo This machine does not support INITRD; exit -1) @test "$(INITRD)" != "" || \ (echo You must specify INITRD; exit -1) install: $(obj)/Image $(CONFIG_SHELL) $(srctree)/$(src)/install.sh $(KERNELRELEASE) \ $(obj)/Image System.map "$(INSTALL_PATH)" zinstall: $(obj)/zImage $(CONFIG_SHELL) $(srctree)/$(src)/install.sh $(KERNELRELEASE) \ $(obj)/zImage System.map "$(INSTALL_PATH)" zi: $(CONFIG_SHELL) $(srctree)/$(src)/install.sh $(KERNELRELEASE) \ $(obj)/zImage System.map "$(INSTALL_PATH)" i: $(CONFIG_SHELL) $(srctree)/$(src)/install.sh $(KERNELRELEASE) \ $(obj)/Image System.map "$(INSTALL_PATH)" subdir- := bootp compressed