Tenth Chapter Experience

Through the tenth chapter, the debugging technology of embedded Linux driver development has been learned.

Knowledge Learned:

First, print kernel debug information: PRINTK

the PRINTK function is prototyped as follows:

asmlinkage int PRINTK (const char * fmt, ...)

The PRINTK file is a simple 4 -digit text file with the following default values:6 4 1 7

6: Output the message to the level of the console.

4: The default message log level.

1: Minimum value that can be set for the console log level

7: Default value for console log level.

Second, prevent PRINTK function to reduce Linux drive performance

1. variable-parameter macros

2.do{...} while (O)

Third, the data interaction through the virtual file system

Proc_mkdir

Name: virtual directory names.

Parent: Proc_dir_entry struct pointerto the parent directory of the virtual directory .

Create_proc_enttry

Name: Virtual file names.

Mode: Access permissions for virtual files

Parent: The proc_dir_entry struct pointer to the parent directory of the virtual file .

Create_proc_read_entty

Name: Virtual file names.

Mode: Access permissions for virtual files

Base: proc_dir_entry struct pointerto the parent directory of the virtual file .

Read_proc: A function pointer that handles read actions.

data: Used for the virtual file system.

Remove_proc_entry

Name: The names of the virtual files to be deleted.

Parent: The proc_dir_entry struct pointer to the parent directory of the virtual file .

Four, Debugging Tools

1. debugging the user-space program with gdb

2. remote debugging of user space programs with gdbserver

3. Remote Debug Kernel program with kgdb

Tenth Chapter Experience