Uboot学习笔记①---(文件目录结构、README摘要、uImage的64字节头信息)

uboot下载地址ftp://ftp.denx.de/pub/u-boot/

1、查看uboot文件目录结构

Directory Hierarchy:
====================/arch           Architecture specific files/arm         Files generic to ARM architecture/cpu       CPU specific files/arm720t      Files specific to ARM 720 CPUs/arm920t      Files specific to ARM 920 CPUs/at91         Files specific to Atmel AT91RM9200 CPU/imx          Files specific to Freescale MC9328 i.MX CPUs/s3c24x0        Files specific to Samsung S3C24X0 CPUs/lib      Architecture specific library files/x86         Files generic to x86 architecture/cpu       CPU specific files/lib      Architecture specific library files/mips            Files generic to MIPS architecture/cpu      CPU specific files/mips32       Files specific to MIPS32 CPUs/xburst        Files specific to Ingenic XBurst CPUs/lib       Architecture specific library files/powerpc     Files generic to PowerPC architecture/cpu       CPU specific files/74xx_7xx     Files specific to Freescale MPC74xx and 7xx CPUs/mpc5xx     Files specific to Freescale MPC5xx CPUs/mpc5xxx     Files specific to Freescale MPC5xxx CPUs/lib        Architecture specific library files
/api            Machine/arch independent API for external apps
/board          Board dependent files
/common         Misc architecture independent functions
/disk           Code for disk drive partition handling
/doc            Documentation (don't expect too much)
/drivers        Commonly used device drivers
/dts                    Contains Makefile for building internal U-Boot fdt.
/examples       Example code for standalone applications, etc.
/fs             Filesystem code (cramfs, ext2, jffs2, etc.)
/include        Header Files
/lib            Files generic to all architectures/libfdt       Library files to support flattened device trees/lzma            Library files to support LZMA decompression/lzo         Library files to support LZO decompression
/net            Networking code
/post           Power On Self Test
/rtc            Real Time Clock drivers
/tools          Tools to build S-Record or U-Boot images, etc.

uboot层次结构和调用关系

2、查看解压目录中的README文件

Software Configuration:
=======================
Configuration is usually done using C preprocessor defines; the
rationale behind that is to avoid dead code whenever possible.

There are two classes of configuration variables:

# README文件中说明了很多“CONFIG_”和“CONFIG_SYS_”的作用，在看makefile时不懂的话可以查询一下
* Configuration _OPTIONS_:
These are selectable by the user and have names beginning with
"CONFIG_".

* Configuration _SETTINGS_:
These depend on the hardware etc. and should not be meddled with if
you don't know what you're doing; they have names beginning with
"CONFIG_SYS_".

编译uboot

Selection of Processor Architecture and Board Type:
--------------------------------------------------
For all supported boards there are ready-to-use default
configurations available; just type "make <board_name>_config".

Example: For a TQM823L module type:

cd u-boot
make TQM823L_config

For the Cogent platform, you need to specify the CPU type as well;
e.g. "make cogent_mpc8xx_config". And also configure the cogent
directory according to the instructions in cogent/README.

make NAME_config

where "NAME_config" is the name of one of the existing configu-
rations; see boards.cfg for supported names.（NAME_config在uboot根目录中）

Finally, type "make all", and you should get some working U-Boot
images ready for download to / installation on your system:

- "u-boot.bin" is a raw binary image
- "u-boot" is an image in ELF binary format
- "u-boot.srec" is in Motorola S-Record format

#使用命令改变make编译输出uboot.bin的目录 etc.

By default the build is performed locally and the objects are saved
in the source directory. One of the two methods can be used to change
this behavior and build U-Boot to some external directory:
1. Add O= to the make command line invocations:
   make O=/tmp/build distclean
   make O=/tmp/build NAME_config
   make O=/tmp/build all

2. Set environment variable BUILD_DIR to point to the desired location:
   export BUILD_DIR=/tmp/build
   make distclean
   make NAME_config
   make all
Note that the command line "O=" setting overrides the BUILD_DIR environment
variable.

#以下这段话还不知道什么时候用的上，先记录一下

Please be aware that the Makefiles assume you are using GNU make, so
for instance on NetBSD you might need to use "gmake" instead of
native "make".

#uboot命令汇总

Monitor Commands - Overview:
============================
go    - start application at address 'addr'
run    - run commands in an environment variable
bootm    - boot application image from memory
bootp    - boot image via network using BootP/TFTP protocol
bootz   - boot zImage from memory
tftpboot- boot image via network using TFTP protocoland env variables "ipaddr" and "serverip"(and eventually "gatewayip")
tftpput - upload a file via network using TFTP protocol
rarpboot- boot image via network using RARP/TFTP protocol
diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
loads    - load S-Record file over serial line
loadb    - load binary file over serial line (kermit mode)
md    - memory display
mm    - memory modify (auto-incrementing)
nm    - memory modify (constant address)
mw    - memory write (fill)
cp    - memory copy
cmp    - memory compare
crc32    - checksum calculation
i2c    - I2C sub-system
sspi    - SPI utility commands
base    - print or set address offset
printenv- print environment variables
setenv    - set environment variables
saveenv - save environment variables to persistent storage
protect - enable or disable FLASH write protection
erase    - erase FLASH memory
flinfo    - print FLASH memory information
bdinfo    - print Board Info structure
iminfo    - print header information for application image
coninfo - print console devices and informations
ide    - IDE sub-system
loop    - infinite loop on address range
loopw    - infinite write loop on address range
mtest    - simple RAM test
icache    - enable or disable instruction cache
dcache    - enable or disable data cache
reset    - Perform RESET of the CPU
echo    - echo args to console
version - print monitor version
help    - print online help
?    - alias for 'help'

3、uImage的64字节头信息

Image uImage与zImage的区别

这里就解释了uImage比zImage多的64字节是哪些

在include/image.h中的源码为

#define IH_NMLEN        32    /* Image Name Length        *//** Legacy format image header,* all data in network byte order (aka natural aka bigendian).*/
typedef struct image_header {uint32_t    ih_magic;    /* Image Header Magic Number    */uint32_t    ih_hcrc;    /* Image Header CRC Checksum    */uint32_t    ih_time;    /* Image Creation Timestamp    */uint32_t    ih_size;    /* Image Data Size        */uint32_t    ih_load;    /* Data     Load  Address        */uint32_t    ih_ep;        /* Entry Point Address        */uint32_t    ih_dcrc;    /* Image Data CRC Checksum    */uint8_t        ih_os;        /* Operating System        */uint8_t        ih_arch;    /* CPU architecture        */uint8_t        ih_type;    /* Image Type            */uint8_t        ih_comp;    /* Compression Type        */uint8_t        ih_name[IH_NMLEN];    /* Image Name        */
} image_header_t;
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#寄存器使用情况

On ARM, the following registers are used:

R0:   function argument word/integer result
   R1-R3:   function argument word
   R9:   GOT pointer
   R10:   stack limit (used only if stack checking if enabled)
   R11:   argument (frame) pointer
   R12:   temporary workspace
   R13:   stack pointer
   R14:   link register
   R15:   program counter

==> U-Boot will use R8 to hold a pointer to the global data