Tips
- C code
- MODULE_LICENSE("Dual BSD/GPL"); is must for all drivers
- Hook functions for insmod and rmmod
- module_init(function_name): called by system for insmod
- module_exit(function_name): called by system for rmmod
- EXPORT_SYMBOL macro helps to export functions
- Makefile
- CFILES := main.c sub.c # multiple files included
- obj-m # indicate this module is in the kernel domain
- hello-objs := $(CFILES:.c=.o) # no redundant blanks
- V=1 # shows detailed compile process
- Concept of context
- for driver, we have "Process context" and "Interrupt context"
- Process context, aka user context, is triggered from user space process
- Interrupt context, is trigger by HW interrupt
- Methods
- readelf -s hello.ko # display the symbol table; man readelf for more options
- file hello.ko
