The Linux Kernel/System

System means general functions used to support and manage other kernel functionality. Synonym: infrastructure.

Booting and Halting

Booting

• Article about booting of the kernel
• wikipedia:Booting
• http://tldp.org/HOWTO/Linux-i386-Boot-Code-HOWTO/
• http://www.tldp.org/LDP/lki/lki-1.html
• http://www.tldp.org/HOWTO/KernelAnalysis-HOWTO-4.html

cat /proc/cmdline
arch/i386/boot/bootsect.S
arch/i386/kernel/head.S: calls start_kernel
In init/main.c:
start_kernel, rest_init, init, run_init_process

Halting and rebooting

• Softdog Driver
• wikipedia:Shutdown
• "Linux for PowerPC Embedded Systems HOWTO: Boot Sequence" by Boas Betzler
• "Embedded Linux Howto" by Sebastien Huet
• "Migrating from x86 to PowerPC, Part 2: Anatomy of the Linux boot process" by Lewin Edwards
• "Inside the Linux boot process" by M. Tim Jones
• "Reducing OS Boot Times for In-Car Computer Applications" by Damien Stolarz

sys_reboot calls machine_restart or machine_halt or machine_power_off

Userspace communication

syscall, /proc, /dev, /sys

linux/proc_fs.h
create_proc_entry etc

• ULK3 Chapter 10. System Calls
• ULK3 Chapter 11. Signals

Devices

ls /dev
cat /proc/devices

Char devices

• drivers/char
• drivers/char/keyboard.c

• register_chrdev

• LDD3:Char Drivers
• LDD3:Advanced Char Driver Operations
• LDD3:TTY Drivers
• LDD1:#3
• LDD1:#5

Chapter 13. I/O Architecture and Device Drivers

DMA

• Documentation/DMA-mapping.txt
• DMA-able memory: pci_alloc_consistent __get_free_page kmalloc kmem_cache_alloc
• pci_pool
• LDD3:Memory Mapping and DMA
• http://www.xml.com/ldd/chapter/book/ch13.html mmap and DMA

SAC Single Address Cycle

Modules

• Article about modules

lsmod
cat /proc/modules

• kernel/kmod.c
• LDD3: Building and Running Modules
• http://www.xml.com/ldd/chapter/book/ch02.html
• http://www.tldp.org/LDP/tlk/modules/modules.html
• http://www.tldp.org/LDP/lkmpg/2.6/html/ The Linux Kernel Module Programming Guide

I/O ports and registers

Modern functions for port I/O:

ioport_map

ioread8 iowrite8

ioread16 iowrite16

ioread32 iowrite32

#include <linux/ioport.h>

Functions for memory mapped registers:

ioremap

readb writeb

readw writew

readl writel

The {in,out}[bwl] macros are for emulating x86-style PCI/ISA IO space:

inb outb

inw outw

inl outl

• LDD3:Communicating with Hardware
• ULK3 Chapter 13. I/O Architecture and Device Drivers

Hardware Device Drivers

Hardware Device Drivers are different from char and block devices.

or just Device Drivers

Keywords: kobjects, sysfs, buses, devices, drivers, classes, firmware, hotplug

• LDD3:The Linux Device Model

• http://www.tldp.org/LDP/tlk/dd/drivers.html
• http://www.xml.com/ldd/chapter/book/
• http://examples.oreilly.com/linuxdrive2/

• drivers/
• drivers/video
  • register_framebuffer
• drivers/net
• drivers/pci
• etc...

Busses: input, PCI, USB

Input bus: keyboard and mouse

cat /proc/bus/input/devices

PCI bus

pci_register_driver

lspci
cat /proc/pci
cat /proc/bus/pci/devices

• #include <linux/pci.h>
• Documentation/pci.txt

• LDD3:PCI Drivers
• http://www.tldp.org/LDP/tlk/dd/pci.html

USB bus

lsusb
cat /proc/bus/usb/devices

• Documentation/usb
• LDD3:USB Drivers

Building and Updating

• Updating

Debugging

• printk
• dump_stack
• show_registers
• dmesg --console-level <level>
• gdb /usr/src/linux/vmlinux /proc/kcore
• Magic SysRq key

• SysRq from linux doc

• git bisect ...

• LDD3:Debugging Techniques
• http://www.xml.com/ldd/chapter/book/ch04.html

oops

• http://lxr.linux.no/source/Documentation/oops-tracing.txt
• http://www.urbanmyth.org/linux/oops/ Good presentation
• http://www.mulix.org/lectures/kernel_oopsing/kernel_oopsing.pdf

printk

linux/arch/i386/kernel/traps.c
[1]

KDB (Built-in Kernel Debugger) Local debugging.

• http://www-106.ibm.com/developerworks/linux/library/l-kdbug/?ca=dgr-wikiaKDB
• http://oss.sgi.com/projects/kdb/
• ftp://oss.sgi.com/www/projects/kdb/download/

Other

• http://user-mode-linux.sourceforge.net/
• CONFIG_MAGIC_SYSRQ, handle_sysrq
  • http://lxr.linux.no/source/drivers/char/sysrq.c
  • http://lxr.linux.no/ident?i=proc_sysrq_trigger_operations
• http://lkcd.sourceforge.net/ Linux Kernel Crash Dump

KGDB Remote GDB debugging.

# gdb -q vmlinux
(gdb) target remote /dev/ttyS0