Kernel Development Learning Pipeline

A5 - Building Character 💪

It’t time to write your first driver!

Outcomes:

• Get familiar with which system calls can be performed on a character device file.
• Get familiar with how the behavior of a character device is specified by its file_operations in the driver.
• Get familiar with how userspace code can invoke kernel code.

Procedure:

• You will be assigned a random sequence of operations.
• Add the ioctl and llseek syscalls to your copy of the driver provided in the assignment repo.
  • Your implementations should be based on the implementations of the read and write operations.
• Write a userspace program to interact with the character driver from class.
  • The userspace program will call the syscalls available through the driver in order of the sequence assigned to you. The userspace program should produce a matching output to what is assigned to you.
  • Your program should check for system call errors.

What to submit:

• A patch which adds a directory named firstname_lastname/ to the assignment repo containing a copy of the provided driver and Makefile.
• The second patch should add the ioctl and llseek operations to the existing driver.
• The third patch should add your userspace program that implements the assignment and should add to the existing Makefile.
  • Make sure to have compiler warnings enabled (at least -Wall but ideally -Wextra and -Wpedantic too, or even -Weverything if you use clang) and that your code doesn’t have any warnings or errors.
• The fourth patch should add a file containing the dmesg log from the driver upon a successful run of your program.
• Don’t forget the cover letter.

Submission Guidelines