Chickadee OS

This is Chickadee, a teaching operating system built for Harvard’s CS 161 in 2018.

Quickstart: make run

Make targets

Run make NCPU=N run to run with N virtual CPUs (default is 2).

Run make SAN=1 run to run with sanitizers.

Normally Chickadee’s debug log is written to log.txt. Run make LOG=stdio run to redirect the debug log to the standard output, or make LOG=file:FILENAME run to redirect it to FILENAME.

Run make D=1 run to ask QEMU to print verbose information about interrupts and CPU resets to the standard error. This setting will also cause QEMU to quit after encountering a triple fault (normally it will reboot).

Source files

Common files

File	Description
types.h	Type definitions
lib.hh/cc	Chickadee C library
x86-64.h	x86-64 hardware definitions
elf.h	ELF64 structures

Boot loader

File	Description
bootentry.S	Boot loader entry point
boot.cc	Boot loader main code
boot.ld	Boot loader linker script

Kernel libraries

File	Description
k-lock.hh	Kernel spinlock
k-memrange.hh	Memory range type tracker
k-vmiter.hh/cc	Page table iterators
k-apic.hh	Access interrupt controller hardware

Kernel core

File	Description
kernel.hh	Kernel declarations
k-exception.S	Kernel entry points
k-init.cc	Kernel initialization
k-hardware.cc	Hardware access
k-cpu.cc	Kernel cpustate type
k-proc.cc	Kernel proc type
kernel.cc	Kernel exception handlers
k-memviewer.cc	Kernel memory viewer component
kernel.ld	Kernel linker script

Processes

File	Description
p-lib.cc/hh	Process library and system call implementations
p-allocator.cc	Allocator process
process.ld	Process binary linker script

Build files

The main output of the build process is a disk image, chickadeeos.img. QEMU “boots” off this disk image, but the image could conceivably boot on real hardware! The build process also produces other files that can be useful to examine.

File	Description
obj/kernel.asm	Kernel assembly (with addresses)
obj/kernel.sym	Kernel defined symbols
obj/p-allocator.asm, sym	Same for process binaries