OSAn old university project to create an x86 os
-=-=-= ELEC4710 - Realtime Systems =-=-=- -=-=-= README.TXT =-=-=- By Colin Goudie ( 9805806 )
This operating system should be compiled on a GNU Operating System using GCC, and the Gnu Assembler, using gmake.
Notes on the example
user.c contains the code that can be used to varify certain features of this kernel.
We have 2 Normal priority threads (test_function and test_function2) started from kernel.c. These ensure both semaphores and our timer is working by attempting to enter the critical section defined between sema_wait(sema) and sema_signal(sema). Both these threads use the same semaphore so effectly they block each other each time. When entering the critical sections they sleep for a few hundred milliseconds.
Before test_function2 actually starts it also starts a higher priority thread. This thread continually loops printing out its current loop count. When it passed 15,000 iterations the thread dies.
The important thing here to note is that the scheduler avoids starvation of the lower priority threads by not allowing the high priority task to hog the CPU all the time.
test_function also starts a realtime thread that executions for 500 iterations before dying. This demonstrates the dynamic memory (i.e. thread creation and destruction) and also that the realtime thread takes preference over all threads with no limit to the amount of time slicing it can receive.
This kernel also supports dynamic memory via the k_malloc and k_free commands. Threads can also die by
Building the Kernel
The kernel.bin file that is created must be added to the /boot/ directory of a grub image file or floppy disk that has grub installed on it. This is easily accomplished by following the commands below.
Get the grub_disk.img file from http://www.pro-pos.org/downloads/grub_disk.zip
Place the grub_disk.img file into a directory (/home/user/os)
Set it up for mounting (run command below from /home/user/os
$ losetup /dev/loop0 grub_disk.img
Then you can simply compile this OS with
This creates a file called kernel.bin Then run the prep script
You now have grub_disk.img that contains the bootable OS.
Run BOCH’S i386 emulator or ‘dd’ the img to a floppy disk.
You can also copy the grub_disk.img file to a floppy on windows by using a program such as floppy_image.exe