The Linux Kernel/Human interfaces
Char devices[edit]
A character device file is one of the most simple, fundamental and oldest concepts derived from UNIX.
This kind of devices is used in many facilities from keyboard input to default interface for a sophisticated new driver.
You can find a list of registered char devices on the beginning the listing of /proc/devices.
Key function cdev_addadds a char device to the system.
Tip: Browse the cross-referencing site to explore nearby API and use cases
The most common API functions:
register_chrdev,
unregister_chrdev
alloc_chrdev_region/
register_chrdev_region,
unregister_chrdev_region
References
- Char devicesin kernel API
- include/linux/cdev.h
- fs/char_dev.c
More info
Administration[edit]
TODO
Security[edit]
Function may_openrejects access of unauthorized users to files.
The most common functions for changing ownership and access rights (modes) to files: man 2 chown/ do_fchownat, man 2 chmod/ do_fchmodat.
TODO:
- man 7 credentials
- man 2 access, man 2 faccessat/ access
- man 2 fcntl/ do_fcntl
- man 2 setuid/ __sys_setuid
- man 2 setgid
- man 2 seteuid
- man 2 setresuid
- man 2 setfsuid
- man 2 seccomp
- man 2 bpf
- man 5 acl
References
Debugging[edit]
User-mode debug interfaces
Kernel-mode debug facilities
Most common functions
More ...
- pr_cont- continues a previous log message in the same line
- Log messages with other levels: pr_info, pr_notice, pr_warn,
References
- dmesg --console-level <level>
- gdb /usr/src/linux/vmlinux /proc/kcore
- Magic SysRq key
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://lkcd.sourceforge.net/ Linux Kernel Crash Dump
KGDB Remote GDB debugging.
# gdb -q vmlinux (gdb) target remote /dev/ttyS0
Subsystems[edit]
TODO
References