Operating System 2022-1

Project in SNU ECE Introduction to OS (430.318) lecture, at 2022 spring.

Based on eOS(Educational Operating System) skeleton code, I implemented some functionalities introduced below.

All the codes are written in C, partially Inline Assembly.

Environments

• Ubuntu 16.04.6 LTS 32bit

Build

$ git clone https://github.com/ckswjd99/SNUOS-2022-1
$ cd SNUOS-2022-1
$ cd src
$ make prepare
$ make all
$ ./eos

Usage

• Put user codes inside src/user/work.c, each tasks as a function.
• You must provide stack and TCB for each tasks.
• Create task and manage scheduling inside function eos_user_main.
• User can use every OS functions with prefix eos_.
• Functions with prefix _os_ is only for OS operations, not for users.

Example 1, Example 2, Example 3

Functionalities

Interrupt

• eos_disable_interrupt: Disable whole interrupts.
• eos_enable_interrupt: Enable whole interrupts.

More info about mechanism

Context Switch

Inside src/hal/linux/context.c,

• _os_create_context: Create a context.
• _os_save_context, _os_restore_context: Save and restore a context.

Inside src/core/task.c,

• eos_create_task: Create task.
• eos_schedule: Yeild CPU and schedule another task.

More info about implementation

Periodic Scheduling

Inside src/core/task.c,

• eos_set_period: Set period of a task to wake up and execute.
• eos_sleep: For an amount of time, put task into waiting queue. When time's up, timer raises interrupt and put task into ready queue.
• _os_wakeup_sleeping_task: Put task which is inside waiting queue, into ready queue.

Inside src/core/timer.c,

• eos_set_alarm: When time's up, run handler callback function.
• eos_trigger_counter: Increase counter value of counter struct, then check alarms if it's expired.

More info about implementation

Semaphore

Inside src/core/sync.c,

• eos_init_semaphore: Initialize semaphore.
• eos_acquire_semaphore: Try to acquire a semaphore. Set its waiting type according to timeout parameter.
• eos_release_semaphore: Release a semaphore.

More info about implementation

Message Queue

Inside src/core/comm.c,

• eos_init_mqueue: Initialize message queue.
• eos_send_message: Send a message to the message queue.
• eos_receive_message: Receive a message from the message queue.

More info about implementation