Language Selection

English French German Italian Portuguese Spanish

How System Calls Work in Linux?

Filed under
HowTos

Every GNU/Linux programmer here reading this article must have used system calls to code their programs. GNU/Linux programming is incomplete without system calls. System calls are initiated by software interrupts. Before we delve into that, however, let’s define system calls.

A system call is the mechanism used by an application program to request service from the operating system, or more specifically, the operating system kernel.

Modern processors execute instructions in different privilege states. In system, where just two levels are defined (as in i386), these states are known as user mode and supervisor mode. These privilege levels are defined so that an operating system restrict can control the operations performed by the program. Controlling is done for reasons of security and stability. The kernel of the operating system should always run in privilege mode since it needs to do some operations. Such operations include accessing hardware devices, enabling and disabling interrupts, changing privileged processor state, and accessing memory management units.

Now with this setup of an operating system (with two modes of execution (considering only i386 architecture only)), we need a mechanism to transfer control safety from lesser privileged modes to higher privileged modes.

Full Story.

More in Tux Machines

No Ubuntu Back Doors, Windows and Mac Migrations

Today in Linux news Microsoft's market share has dipped below 90% and Mac is disappearing from Linux conventions. Ubuntu founder Mark Shuttleworth said in an interview today that security and encryption are a commitment of Ubuntu's. Jesse Smith reviewed the latest version of Ubuntu and OMG!Ubuntu! shared some glimpses of Ubuntu in the wild. Bryan Lunduke listed 12 "Linux geeks" all users should follow on social media and Sandra Gittlen highlighted six colleges that "immerse students in Open Source." Read more

pfSense 2.3 Open-Source BSD Firewall Gets Patch That Fixes NTP Security Issues

pfSense developer Chris Buechler announced the availability of a small update for the stable pfSense 2.3 open-source firewall platform based on the FreeBSD operating system. Introduced as pfSense 2.3 Update 1, this is a small patch that only fixes the recently discovered security issues in the Network Time Protocol (NTP) packages, upgrading them from version 4.2.8p6 to 4.2.8p7, and it shouldn't be confused with pfSense 2.3.1, which will be released in the coming weeks as the first maintenance build. Read more

Contributing to open source software with Ian Varley of Salesforce

With open source, you're expanding the sphere of people who might potentially care a lot about your code. You find others who have similar problems, and who can leverage your work and maybe even extend it. The knowledge that you've helped someone avoid "rebuilding the wheel" is really gratifying, and it's amplified when those people actually start getting so involved that they give you contributions of code or ideas. The project picks up steam, and you might even get unforeseen help tackling those issues you didn't have bandwidth to tackle yourself. Really, it's the gift that keeps on giving. Read more

IPFire 2.19 Core Update 101 Patches Cross-Site-Scripting Vulnerability in Web UI

The development team behind the IPFire software have announced the general availability of the Core Update 101 of the IPFire 2.19 Linux kernel-based firewall distribution. Read more