Embed Size (px)
Citation preview
CSCI-3753: Operating SystemsSpring 2019
Anh NguyenDepartment of Computer Science University of Colorado Boulder
PA 2 – Questions & Answers
2CSCI 3753 Spring 2019
LKM – Quick Recap
•What are two main functions required in a LKM code?
•How to compile the LKM code?
•How to load the module into the kernel?
•How to unload the module from the kernel?
3CSCI 3753 Spring 2019
PA2 – Character Device File
4CSCI 3753 Spring 2019
Programs
Kernel
User Space
Physical Device
Device File (/dev/<name>)
Open, Read, Write, Close, Seek
File Operations
mknod –m <permission> <device_file_location><type of driver><major number><minor number>
For example,
sudo mknod –m 777
/dev/simple_character_device
c
240
0
<major>:<minor>
Device Driver
<minor><name>
/dev directory
• Device Type
• Permissions
• Owner
• Group
•Major Device Number
•Minor Device Number
• Timestamp
• Device Name
5CSCI 3753 Spring 2019
Documentation/admin-guide/devices.txt
PA2 – Requirements
1. Dynamically allocate kernel buffer to store the data written by the user • kmalloc() • Allocate memory for objects smaller than page size in the
kernel at initialization time • kfree()• Free memory previously allocated using kmalloc() before
exiting
2. Offset pointer in read/write function
3. NO over seeking/reading/writing in buffer
6CSCI 3753 Spring 2019
PA2 – Updates
•asm/uaccess.h à linux/uaccess.h
• file_operations structure à start from line 1695 in file/lib/modules/4.15.0-33-generic/build/include/linux/fs.h
• For seek operation, there is no pointer returned.loff_t (*llseek) (struct file *, loff_t, int)
change toloff_t abc_llseek (struct file *, loff_t, int)
7CSCI 3753 Spring 2019
Week 4: Processes vs Threads
8CSCI 3753 Spring 2019
Processes
•Are the programs that are running on your machine•Are managed by the kernel•Have an ID associated with it called the process ID
(PID)•ps command• PID: Process ID• TTY: Controlling terminal associated with the process• STAT: Process status code• TIME: Total CPU usage time• CMD: Name of executable/command
9CSCI 3753 Spring 2019
/proc directory
•Contain virtual files and numbered directories corresponding to each running process•Directory names = process ids•When a process ends, its directory in /proc disappears
automatically.•Files in a numbered directory• cmdline• cwd• environ• fd•maps, statm, mem; stat, status
10CSCI 3753 Spring 2019
/proc directory
• Some typical virtual files that provide • Hardware information:• /proc/cpuinfo: identifies the type of processor used by your
system• /proc/iomem: shows you the current map of the system's
memory for each physical device • /proc/meminfo• /proc/interrupts
• File-related info:• /proc/filesystems: displays a list of the file system types currently
supported by the kernel • /proc/partitions
• Kernel configuration parameters:• /proc/cmdline: shows the parameters passed to the kernel at the
time it is started• /proc/sys
11CSCI 3753 Spring 2019
top command
•Display a list of processes with their resource usage.
12CSCI 3753 Spring 2019
Program vs Application vs Process vs Thread
13CSCI 3753 Spring 2019
•Program: a passive entity
•Application: a program loaded into the memory
•Process: a program actively executing from main memory within its own address space
•Thread: a logical flow or unit of execution that runs within the context of a process• Race condition à Thread-safe, reentrant
Process State
•New: The process is being created. •Running: Instructions are being executed. •Waiting: The process is waiting for some event to
occur (such as an I/O completion or reception of a signal). •Ready: The process is waiting to be assigned to a
processor.•Terminated: The process has finished execution.
14CSCI 3753 Spring 2019
IPC Mechanisms
•Signals / Interrupts•Notifying that an event has occurred
•Message Passing• Pipes• Sockets
•Remote Procedure Calls
•Shared Memory• Race conditions• Synchronization
15CSCI 3753 Spring 2019
Week 4 – Checklist
q Discuss PA2q Discuss processes vs threadsq Read more about IPC
17CSCI 3753 Spring 2019
