Embedded GNU/Linux Kernel Internals and Device Drivers ( ldd | 35 hours )

• Basic familiarity with using a GNU/Linux system as an end user
• Basic familiarity with a command line shell
• Basic knowledge of user space / application development
• Intermediate C programming knowledge
• Should have attended Embedded GNU/Linux Systems Architecture before (strongly recommended!) and/or have a good understanding of the topics outlined there

Description

This 5-day training class uses hands-on exercises combined with instruction to illustrate the concepts of GNU/Linux kernel internals and device driver development. It is desinged to bring you quickly up to speed. We describe processes, concepts and commands necessary to write GNU/Linux device drivers through a combination of theory and on-the-job training.

Don't reinvent the wheel, but learn from an experienced trainer and take home a working knowledge and the ability to use it effectively in your own embedded development project.

Who should attend?

People with interest in or tasked with the development or evaluation of developing GNU/Linux device drivers like software engineers, field engineers, (project) managers, hardware engineers.

Introduction

• quick history of GNU/Linux
• licensing
• kernel versioning
• release cycle
• kernel trees
• mainline
• kernel vs. user space
• mechanism vs. policy
• kernel driver alternatives
• RTOS vs. Linux

Memory Management

• Virtual memory vs. physical memory
• memory allocation in kernel
• pages
• zones
• API
• slab

Kernel Patch

• life cycle
• git
• kernel source
• create patch
• check patch
• fix patch
• ship patch
• audited code

Kernel Modules

• get kernel sources
• configure/build/install
• device drivers (statically linked, loaded at runtime)
• init/exit
• licensing
• EXPORT SYMBOL GPL
• out of tree makefile
• module-init-tools
• module in kernel tree
• Kconfig
• parameter passing
• sparse

Char Drivers

• architecture
• user/kernel interface
• I/O subsystem
• VFS
• sysfs (devices, bus, drivers, classes),
• kobject/ktype/kset
• linux kernel driver model
• device files
• char driver
  • initialization
  • registration
  • open, release
  • cdev, cdev add, cdev del,...
  • major/minor numbers
  • udev, udevmonitor, udevadm

Advanced Charachter Driver Operations

• ioctl
• unlocked ioctl
• compat ioctl
• user space API
• kernel space API
• process lifecycle
• sleeping/blocking
• sleeping/waking up
• wait queue
• thundering herd
• poll/select

Kernel Debugging

• bug
• debugging
• debugging the kernel
  • binary search with git
  • debug support from kernel
  • printk syslogd, klogd, loglevels, rate limit, debug levels, debug selective subsystems
  • debugging by querying debugfs
  • oops debugging, asserting oops
  • Magic SysRq Key
  • kgdb/kdb
  • JTAG

Tracing

• gcov
• lcov
• oprofile
• ftrace
  • nop tracer
  • function tracer
  • sched switch tracer
  • function graph tracer
  • dynamic tracer
• trace-cmd/kernelshark
• perf
• LTTng

Interrupts

• interrupts vs. polling
• interrupt
• program sections
• reentrancy
• events
• interrupt handler
• shared interrupt handler
• interrupt flow
• interrupt control

Deferring Work

• top/bottom halves
• softirqs
• tasklets
• work queues
• threaded interrrupts

Concurrency

• critical region/section
• atomic
• race condition
• synchronization
• locking
• locking solutions
• deadlock
• contention
• what to lock?
• what can be used?
  • atomic operations
  • spin locks
  • reader-writer spin locks
  • semaphore
  • binary semaphore
  • mutex
  • reader-writer semaphore
  • completion variables
  • sequential locks
  • disable preemption
  • orderig and barriers

Time

• HZ
• Jiffies
• big/small delays
• kernel timers

Hardware I/O

• I/O Ports
• I/O Memory
• How to deal with side effects accessing registers?

User-Kernel Communication

• put(get)_user()
• copy to(from)_user()
• Kernel I/O
• memory mapping
• procfs
• sysfs
• debugfs
• relayfs
• netlink
• ioctl

Portability

• word size
• opaque types
• signed/unsigned char
• data alignment
• integral promotion
• code reuse
• endianess
• system tick
• page size
• instruction ordering
• SMP/preemption/high memory

Except where otherwise noted content and this course outline are licensed under Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0).