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u-boot镜像的解析

$ file u-bootu-boot: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, not stripped$ file u-boot.bin u-boot.bin: data$ file u-boot.img u-boot.img: u-boot legacy uImage, U-Boot 2021.01-15955-g9f70b17-di\276, Firmware/ARM, Firmware Image (Not compressed), 253568 bytes, Thu Apr  1 07:37:20 2021, Load Address: 0x5FB00000, Entry Point: 0x5FB00000, Header CRC: 0xEDBFD035, Data CRC: 0xB02CAAA8

$ arm-linux-gnueabi-readelf -S   output/u-boot There are 28 section headers, starting at offset 0x1ec6a4:Section Headers:  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al  [ 0]                   NULL            00000000 000000 000000 00      0   0  0  [ 1] .text             PROGBITS        5fb00000 010000 0006f4 00  AX  0   0 32  [ 2] .text_rest        PROGBITS        5fb00700 010700 029284 00  AX  0   0 32  [ 3] .rodata           PROGBITS        5fb29984 039984 009688 00   A  0   0  4  [ 4] .hash             HASH            5fb3300c 04300c 000018 04   A 12   0  4  [ 5] .data             PROGBITS        5fb33024 043024 0025c8 00  WA  0   0  4  [ 6] .got.plt          PROGBITS        5fb355ec 0455ec 00000c 04  WA  0   0  4  [ 7] .u_boot_list      PROGBITS        5fb355f8 0455f8 000aa0 00  WA  0   0  4  [ 8] .rel.dyn          REL             5fb36098 046098 006f80 08   A 12   0  4  [ 9] .bss_start        PROGBITS        5fb36098 04d0d4 000000 00   W  0   0  1  [10] .bss              NOBITS          5fb36098 000000 0058e8 00  WA  0   0  4  [11] .bss_end          PROGBITS        5fb3b980 04d0d4 000000 00   W  0   0  1  [12] .dynsym           DYNSYM          5fb3d018 04d018 000030 10   A 13   3  4  [13] .dynstr           STRTAB          5fb3d048 04d048 000001 00   A  0   0  1  [14] .dynamic          DYNAMIC         5fb3d04c 04d04c 000088 08  WA 13   0  4  [15] .ARM.attributes   ARM_ATTRIBUTES  00000000 04d0d4 000026 00      0   0  1  [16] .comment          PROGBITS        00000000 04d0fa 000074 01  MS  0   0  1  [17] .debug_line       PROGBITS        00000000 04d16e 0229c0 00      0   0  1  [18] .debug_info       PROGBITS        00000000 06fb2e 0bb388 00      0   0  1  [19] .debug_abbrev     PROGBITS        00000000 12aeb6 01da4e 00      0   0  1  [20] .debug_aranges    PROGBITS        00000000 148908 003f58 00      0   0  8  [21] .debug_frame      PROGBITS        00000000 14c860 00b448 00      0   0  4  [22] .debug_str        PROGBITS        00000000 157ca8 012228 01  MS  0   0  1  [23] .debug_loc        PROGBITS        00000000 169ed0 062a0a 00      0   0  1  [24] .debug_ranges     PROGBITS        00000000 1cc8e0 008990 00      0   0  8  [25] .symtab           SYMTAB          00000000 1d5270 010e90 10     26 3489  4  [26] .strtab           STRTAB          00000000 1e6100 006494 00      0   0  1  [27] .shstrtab         STRTAB          00000000 1ec594 000110 00      0   0  1Key to Flags:  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),  L (link order), O (extra OS processing required), G (group), T (TLS),  C (compressed), x (unknown), o (OS specific), E (exclude),  y (purecode), p (processor specific)

• 文件数据的解析

vim u-boot 和 u-boot.bin 之后 :%!xxd 查看二进制文件然后 发现 u-boot.bin 00000000位置的32bit数据 在u-boot 的 00010000 位置所以如果直接烧写 u-boot 是不可以的u-boot.bin 00000000 位置 的 32bit 数据 是 b reset 的 二进制码但是 u-boot 的 00000 位置 是 elf 格式的格式相关码所以 烧写的话不能烧写 u-bootu-boot是个 elf 文件,这个elf 文件什么时候用 // ELF 是一个 标准,请查看相关标准文档	1. 生成 .bin 用	2. 生成 .dis 用	3. 生成 .srec 用	4. gdb debug 用u-boot.img  是 在 u-boot.bin 前加了一些字节, 供 spl 解析一般的spl加载u-boot 流程中需要用u-boot.img 在ok6410a 的u-boot-2021.01 中,烧写的 是 u-boot.bin 文件,是因为 不是用的标准的 spl加载u-boot流程为什么linux发行版下面命令A都是 elf 格式,且可以执行因为linux发行版中有解析 elf 格式的代码,这些代码能找到命令A的入口

参考资料

• 链接脚本

$ cat output/u-boot.lds OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")OUTPUT_ARCH(arm)ENTRY(_start)SECTIONS{
    . = 0x00000000; . = ALIGN(4); .text : {
     *(.__image_copy_start)  *(.vectors)  arch/arm/cpu/arm1176/start.o (.text*)  board/samsung/ok6410a/lowlevel_init.o (.text*)  board/samsung/ok6410a/bl2_mmc_copy.o (.text*) } .__efi_runtime_start : {
     *(.__efi_runtime_start) } .efi_runtime : {
     *(.text.efi_runtime*)  *(.rodata.efi_runtime*)  *(.data.efi_runtime*) } .__efi_runtime_stop : {
     *(.__efi_runtime_stop) } .text_rest : {
     *(.text*) } . = ALIGN(4); .rodata : {
    *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*))) } . = ALIGN(4); .data : {
     *(.data*) } . = ALIGN(4); . = .; . = ALIGN(4); .u_boot_list : {
     KEEP(*(SORT(.u_boot_list*))); } . = ALIGN(4); .efi_runtime : {
                   __efi_runtime_start = .;  *(efi_runtime_text)  *(efi_runtime_data)                __efi_runtime_stop = .; } .efi_runtime_rel_start : {
     *(.__efi_runtime_rel_start) } .efi_runtime_rel : {
     *(.rel*.efi_runtime)  *(.rel*.efi_runtime.*) } .efi_runtime_rel_stop : {
     *(.__efi_runtime_rel_stop) } . = ALIGN(4); .image_copy_end : {
     *(.__image_copy_end) } .rel_dyn_start : {
     *(.__rel_dyn_start) } .rel.dyn : {
     *(.rel*) } .rel_dyn_end : {
     *(.__rel_dyn_end) } .end : {
     *(.__end) } _image_binary_end = .; . = ALIGN(4096); .mmutable : {
     *(.mmutable) } .bss_start __rel_dyn_start (OVERLAY) : {
     KEEP(*(.__bss_start));  __bss_base = .; } .bss __bss_base (OVERLAY) : {
     *(.bss*)   . = ALIGN(4);   __bss_limit = .; } .bss_end __bss_limit (OVERLAY) : {
     KEEP(*(.__bss_end)); } .dynsym _image_binary_end : {
    *(.dynsym) } .dynbss : {
    *(.dynbss) } .dynstr : {
    *(.dynstr*) } .dynamic : {
    *(.dynamic*) } .plt : {
    *(.plt*) } .interp : {
    *(.interp*) } .gnu.hash : {
    *(.gnu.hash) } .gnu : {
    *(.gnu*) } .ARM.exidx : {
    *(.ARM.exidx*) } .gnu.linkonce.armexidx : {
    *(.gnu.linkonce.armexidx.*) }}

• u-boot 的生成过程

arm-linux-gnueabi-ld.bfd  -pie  --gc-sections -Bstatic  --no-dynamic-linker -Ttext 0x5FB00000 -o u-boot -T u-boot.lds arch/arm/cpu/arm1176/start.o --start-group  arch/arm/cpu/built-in.o  arch/arm/cpu/arm1176/built-in.o  arch/arm/lib/built-in.o  arch/arm/mach-s3c64xx/built-in.o  board/samsung/common/built-in.o  board/samsung/ok6410a/built-in.o  cmd/built-in.o  common/built-in.o  disk/built-in.o  drivers/built-in.o  drivers/dma/built-in.o  drivers/gpio/built-in.o  drivers/i2c/built-in.o  drivers/net/built-in.o  drivers/net/phy/built-in.o  drivers/power/built-in.o  drivers/power/battery/built-in.o  drivers/power/domain/built-in.o  drivers/power/fuel_gauge/built-in.o  drivers/power/mfd/built-in.o  drivers/power/pmic/built-in.o  drivers/power/regulator/built-in.o  drivers/serial/built-in.o  drivers/spi/built-in.o  drivers/usb/cdns3/built-in.o  drivers/usb/common/built-in.o  drivers/usb/dwc3/built-in.o  drivers/usb/emul/built-in.o  drivers/usb/eth/built-in.o  drivers/usb/host/built-in.o  drivers/usb/mtu3/built-in.o  drivers/usb/musb-new/built-in.o  drivers/usb/musb/built-in.o  drivers/usb/phy/built-in.o  drivers/usb/ulpi/built-in.o  env/built-in.o  fs/built-in.o  lib/built-in.o  net/built-in.o --end-group arch/arm/lib/eabi_compat.o  arch/arm/lib/lib.a -Map u-boot.map

• u-boot.bin的生成过程

arm-linux-gnueabi-objcopy --gap-fill=0xff  -j .text -j .secure_text -j .secure_data -j .rodata -j .hash -j .data -j .got -j .got.plt -j .u_boot_list -j .rel.dyn -j .binman_sym_table -j .text_rest -j .dtb.init.rodata  -O binary   u-boot u-boot-nodtb.bincat u-boot-nodtb.bin dts/dt.dtb > u-boot.bin

• u-boot.img的生成过程

./tools/mkimage -A arm -T firmware -C none -O u-boot -a 0x5FB00000 -e 0x5FB00000 -n "U-Boot 2021.01""-15955-g9f70b17-dirty for ok6410a board" -d u-boot.bin u-boot.img

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