Embedded GNU/Linux Kernel Internals and Device Drivers Training Course

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).