Preliminary Study on Linux Kernel Configuration and Compilation

Kernel configuration issues

When configuring the Linux kernel, we need to think about several questions:
(1) Configure which directories need to be compiled
(2) Configure which files need to be compiled
(3) When compiling, which directory is the file,
such as <mach/hardware.h>

Solution:
Makefile make

• The Makefile
  under the main directory Makefile arch is related
  to other files through include
• Makefile of each subdirectory
  obj-y: compile into the kernel
  obj-: not compile into
  obj-m: compile as a module

$(hdr-arch)
-I$(srctree)/arch/$(SRCARCH)/Makefile


SRCARCH=arm
hrd-arch   arm

How to configure the kernel

Configuration steps:
(1) Configuration warehouse selection
(2) Cross-compiler modification
(3) System structure selection
(4) Addition, deletion and modification check ( make menuconfig )

details:

1. SUBARCH is X86 by default, and the default configuration of the kernel is
   changed to the word arm according to the X86 ARCH variable.
   Cross compiling
   CROSS_COMPILE
2. Which files are compiled?
   CONFIG_xxx
   configuration sheet: linux-3.0.8/arch/arm/configs
   export the configuration sheet to the main directory export------> .config
   defconfig
3. Modify defconfig to apply to the board

Implementation

details as follows,

1. Modify the Makefile in the main directory (linux-3.0.8) to the following line 195 or so

ARCH            ?= arm
CROSS_COMPILE   ?= arm-linux-

2. Copy the corresponding defconfig

cp arch/arm/configs/s3c6400_defconfig .config

3. Then execute make menuconfig to add, delete, modify and check

After the configuration is complete, execute make uImage

If this error occurs---------------------------
Can't use'defined(@array)' (Maybe you should just omit the defined ()?) at kernel/timeconst.pl line 373.
---------------------->

solution:

• In fact, the error message prompt has clearly told you that you should omit defined().
  Here, we open kernel/timeconst.pl
  @val = @{ KaTeX parse error: Expected'}', got'EOF' at end of input : canned_values{ hz}}; if (defined(@val)) { @val = compute_values( KaTeX parse error: Expected'EOF', got'}' at position 7: hz); }̲ output( hz, @val) ; Change if (defined(@val)) to if (@val) and compile again to pass. I checked the updates and found that one of them was that the Perl version was upgraded to v5.22.1. Then I checked the official Perl documentation and found that the official website had a bug and the version removed the defined (@array). You can directly use the array to determine non-empty.
  
  
  
  

Three image relationships

vmlinux: OS elf file (elf file executable by the operating system)

Image (larger) ---------> zImage (decompressed, but it does not meet the boot rules of uboot, so uImage supporting booting is produced) ---------> uImage

Kconfig syntax

Kconfig in the home directory

• ---------> source "arch/$SRCARCH/Kconfig"
  means to include arch/arm/Kconfig
  source : include
• Menu and endmuenu syntax: The displayed menu can be added as follows:
  
• config syntax :
  
  after the
  configuration fiber information is executed, CONFIG_ABC=y appears in .config. The effect in Makefile is: obj-$(CONFIG_ABC) += XX.c
  bool: information
  tristate: tristate (compiled into the kernel, not Compile into the kernel, add to the kernel as a module)

Add led driver to the kernel

1. Create a myled folder in the driver/char/ directory, and then copy the driver led.c file to this directory:

mkdir myled
cp led.c   /home/zhangbin/mini6410/linux-2.6.38/driver/char/myled/ 

2. Create Makefile in the myled directory creation directory (format can refer to Makefile in other directories)
   
3. Then modify the Makefile of the parent directory (driver/char directory) as follows (line 81) obj-y += directory name/
   
4. Create Kconfig in the myled directory. The content is as follows
   
5. Modify the Kconfig of the upper-level directory to include the Kconfig
   source in the myled directory and
   
   finally execute make menuconfig for configuration