$(obj)/Image: vmlinux FORCE
  $(call if_changed,objcopy)

quiet_cmd_objcopy = OBJCOPY $@
cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@

$(obj)/Image: vmlinux FORCE
  $(warning "OBJCOPYFLAGS: $(OBJCOPYFLAGS)")
  $(warning "OBJCOPYFLAGS_$(@F): $(OBJCOPYFLAGS_$(@F))")
  $(call if_changed,objcopy)

LD      vmlinux
SORTEX  vmlinux
SYSMAP  System.map
arch/arm/boot/Makefile:61: "OBJCOPYFLAGS: -O binary -R .comment -S"
arch/arm/boot/Makefile:61: "OBJCOPYFLAGS_Image: "
OBJCOPY arch/arm/boot/Image
Building modules, stage 2.
MODPOST 6 modules
Kernel: arch/arm/boot/Image is ready

-O binary 表示生成二进制文件

-R .comment 表示移除 .comment section

-S 表示移除所有的标志以及重定位信息

$(obj)/piggy_data: $(obj)/../Image FORCE
  $(call if_changed,$(compress-y))

compress-$(CONFIG_KERNEL_GZIP) = gzip
compress-$(CONFIG_KERNEL_LZO)  = lzo
compress-$(CONFIG_KERNEL_LZMA) = lzma
compress-$(CONFIG_KERNEL_XZ)   = xzkern
compress-$(CONFIG_KERNEL_LZ4)  = lz4

$(obj)/piggy_data: $(obj)/../Image FORCE
  $(wraning "compress-y: $(compress-y)")
  $(call if_changed,$(compress-y))

CALL    scripts/checksyscalls.sh
CHK     include/generated/compile.h
Kernel: arch/arm/boot/Image is ready
Building modules, stage 2.
MODPOST 6 modules
arch/arm/boot/compressed/Makefile:192: "compress-y: gzip"
Kernel: arch/arm/boot/zImage is ready

quiet_cmd_gzip = GZIP    $@
      cmd_gzip = cat $(filter-out FORCE,$^) | gzip -n -f -9 > $@

-n 压缩文件时，不保存原来文件名称以及时间戳

-f 强制压缩文件。不理会文件名称或硬链接是否存在以及文件是否为符号链接

-9 用 9 调整压缩的速度，-1 或 --fast 表示最快压缩方法 (低压缩比), -9 或者 --best 表示最慢的压缩方法 (高压缩比)

$(obj)/piggy.o: $(obj)/piggy_data

/* SPDX-License-Identifier: GPL-2.0 */
        .section .piggydata,#alloc
        .globl  input_data
input_data:
        .incbin "arch/arm/boot/compressed/piggy_data"
        .globl  input_data_end
input_data_end:

$(obj)/vmlinux: $(obj)/vmlinux.lds $(obj)/$(HEAD) $(obj)/piggy.o \
                $(addprefix $(obj)/, $(OBJS)) $(lib1funcs) $(ashldi3) \
                $(bswapsdi2) $(efi-obj-y) FORCE
        @$(check_for_multiple_zreladdr)
        $(call if_changed,ld)
        @$(check_for_bad_syms)

(vmlinux)
+---------+
|         |
|         |
|         |
| piggy.o |
|         |
|         |
|         |
+---------+
| misc.o  |
+---------+
| big_    |
| endian.o|
+---------+
| head-   |
| xscal.o |
+---------+
|  head.o |
+---------+

/*
 *  Copyright (C) 2000 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#ifdef CONFIG_CPU_ENDIAN_BE8
#define ZIMAGE_MAGIC(x) ( (((x) >> 24) & 0x000000ff) | \
                          (((x) >>  8) & 0x0000ff00) | \
                          (((x) <<  8) & 0x00ff0000) | \
                          (((x) << 24) & 0xff000000) )
#else
#define ZIMAGE_MAGIC(x) (x)
#endif

OUTPUT_ARCH(arm)
ENTRY(_start)

/DISCARD/ : {
  *(.ARM.exidx*)
  *(.ARM.extab*)
  /*
   * Discard any r/w data - this produces a link error if we have any,
   * which is required for PIC decompression.  Local data generates
   * GOTOFF relocations, which prevents it being relocated independently
   * of the text/got segments.
   */
  *(.data)
}

. = TEXT_START;
_text = .;

.text : {
  _start = .;
  *(.start)
  *(.text)
  *(.text.*)
  *(.fixup)
  *(.gnu.warning)
  *(.glue_7t)
  *(.glue_7)
}

.table : ALIGN(4) {
  _table_start = .;
  LONG(ZIMAGE_MAGIC(2))
  LONG(ZIMAGE_MAGIC(0x5a534c4b))
  LONG(ZIMAGE_MAGIC(__piggy_size_addr - _start))
  LONG(ZIMAGE_MAGIC(_kernel_bss_size))
  LONG(0)
  _table_end = .;
}

.rodata : {
  *(.rodata)
  *(.rodata.*)
  *(.data.rel.ro)
}

.piggydata : {
  *(.piggydata)
  __piggy_size_addr = . - 4;
}

.got.plt              : { *(.got.plt) }
_got_start = .;
.got                  : { *(.got) }
_got_end = .;

/* ensure the zImage file size is always a multiple of 64 bits */
/* (without a dummy byte, ld just ignores the empty section) */
.pad                  : { BYTE(0); . = ALIGN(8); }

#ifdef CONFIG_EFI_STUB
.data : ALIGN(4096) {
  __pecoff_data_start = .;
  /*
   * The EFI stub always executes from RAM, and runs strictly before the
   * decompressor, so we can make an exception for its r/w data, and keep it
   */
  *(.data.efistub)
  __pecoff_data_end = .;

  /*
   * PE/COFF mandates a file size which is a multiple of 512 bytes if the
   * section size equals or exceeds 4 KB
   */
  . = ALIGN(512);
}
__pecoff_data_rawsize = . - ADDR(.data);
#endif

_edata = .;

/*
 * The image_end section appears after any additional loadable sections
 * that the linker may decide to insert in the binary image.  Having
 * this symbol allows further debug in the near future.
 */
.image_end (NOLOAD) : {
  /*
   * EFI requires that the image is aligned to 512 bytes, and appended
   * DTB requires that we know where the end of the image is.  Ensure
   * that both are satisfied by ensuring that there are no additional
   * sections emitted into the decompressor image.
   */
  _edata_real = .;
}

_magic_sig = ZIMAGE_MAGIC(0x016f2818);
_magic_start = ZIMAGE_MAGIC(_start);
_magic_end = ZIMAGE_MAGIC(_edata);
_magic_table = ZIMAGE_MAGIC(_table_start - _start);

. = BSS_START;
__bss_start = .;
.bss                  : { *(.bss) }
_end = .;

#
# We now have a PIC decompressor implementation.  Decompressors running
# from RAM should not define ZTEXTADDR.  Decompressors running directly
# from ROM or Flash must define ZTEXTADDR (preferably via the config)
# FIXME: Previous assignment to ztextaddr-y is lost here. See SHARK
ifeq ($(CONFIG_ZBOOT_ROM),y)
ZTEXTADDR       := $(CONFIG_ZBOOT_ROM_TEXT)
ZBSSADDR        := $(CONFIG_ZBOOT_ROM_BSS)
else
ZTEXTADDR       := 0
ZBSSADDR        := ALIGN(8)
endif

CPPFLAGS_vmlinux.lds := -DTEXT_START="$(ZTEXTADDR)" -DBSS_START="$(ZBSSADDR)"

. = ALIGN(8);         /* the stack must be 64-bit aligned */
.stack                : { *(.stack) }

PROVIDE(__pecoff_data_size = ALIGN(512) - ADDR(.data));
PROVIDE(__pecoff_end = ALIGN(512));

.stab 0               : { *(.stab) }
.stabstr 0            : { *(.stabstr) }
.stab.excl 0          : { *(.stab.excl) }
.stab.exclstr 0       : { *(.stab.exclstr) }
.stab.index 0         : { *(.stab.index) }
.stab.indexstr 0      : { *(.stab.indexstr) }
.comment 0            : { *(.comment) }
ASSERT(_edata_real == _edata, "error: zImage file size is incorrect");

vmlinux:     file format elf32-little
vmlinux
architecture: UNKNOWN!, flags 0x00000112:
EXEC_P, HAS_SYMS, D_PAGED
start address 0x00000000

Program Header:
    LOAD off    0x00010000 vaddr 0x00000000 paddr 0x00000000 align 2**16
         filesz 0x0043cf70 memsz 0x0043df88 flags rwx
   STACK off    0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**4
         filesz 0x00000000 memsz 0x00000000 flags rwx

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00003ae0  00000000  00000000  00010000  2**5
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .table        00000014  00003ae0  00003ae0  00013ae0  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  2 .rodata       00000ce4  00003af4  00003af4  00013af4  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .piggydata    0043875c  000047d8  000047d8  000147d8  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .got.plt      0000000c  0043cf34  0043cf34  0044cf34  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  5 .got          00000028  0043cf40  0043cf40  0044cf40  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  6 .pad          00000008  0043cf68  0043cf68  0044cf68  2**0
                  CONTENTS, ALLOC, LOAD, DATA
  7 .bss          00000018  0043cf70  0043cf70  0044cf70  2**2
                  ALLOC
  8 .stack        00001000  0043cf88  0043cf88  0044cf70  2**0
                  ALLOC
  9 .comment      00000074  00000000  00000000  0044cf70  2**0
                  CONTENTS, READONLY
 10 .ARM.attributes 0000002d  00000000  00000000  0044cfe4  2**0
                  CONTENTS, READONLY

$(obj)/zImage:  $(obj)/compressed/vmlinux FORCE
        $(call if_changed,objcopy)

mkimage -A arm -O linux -T kernel -C none -a 60008000 -e 60008000 -n linux-5.0 -d zImage uImage