Operating Systems II -- NetBSD kernel source code tour

General remarks on code

Many structures are open coded in header files.
To avoid mistakes and to help read the code, fields are prefixed with a couple of letters reminding the name of the structure. See sys/exec.h

Exercise: try to see where and when typedef's were introduced in the kernel source. Are typedefs useful in any context?

See sys/queue.h. It somehow forces the use of struct's.
Inheritance. See sockets API (struct sockaddr_*) and struct device in struct xxx_softc. Not much used but we see it in preparation for the study of the VFS.
The bus_space framework. Hides the differences between IO vs Memory mapped registers, allows the same device driver to talk to devices which are mapped with other endianness or with a different stride in registers addresses. See sys/bus_proto.h and dev/ic/. Where is the implementation of bus_space?
Remarks based on previous lecture:
- see struct proc and struct lwp: NetBSD has the two concepts of process and (kernel) thread
- difference between busses which can enumerate the devices present on the bus and busses which can't. See autoconf(9) and config_search*() vs config_found*()
Notice that network devices are handled differently than other devices: they are not open()ed.

Remark: most header files are in sys/

See uvm/

See kern/kern_lwp.c and kern/sched_*.c

kern/subr_*.c, see pools

compat/

How to configure and build a kernel.

New: fine-grain control over authorizations (or: root is too simplistic)