Some C code i write to study systems programming (while reading The Linux Programming Interface)
Learn Linux C programming by exercises
Linux kernel source tree
MCC Universal Library for Linux
Linux-evocation is a conversion of the historic 0.99.12 linux kernel so that it compiles under gcc 5, cross compiles under MacOS and runs with qemu.
A C library for peripheral I/O (GPIO, LED, PWM, SPI, I2C, MMIO, Serial) in Linux.