Download
1 / 20
200 likes | 293 Vues
Learn about address space, services, drivers, and the role they play in processes. Explore executable code, global data, heap, stack, services, and drivers in the context of an operating system. Understand the significance of different components of a process and how they interact within the system.
E N D
Lecture 10: Processes II-C • Address Space • Services • Drivers
Address Space • Process is given: • Executable Code • Global Data • Heap • Stack • This is referred to as the process’ “address space”
Executable Code • Contains our binary code • Is typically static in content • Self-modifiable code is dangerous! • Also has fixed size
Global Data • Contains both initialized and uninitialized data • inti = 42; • char c; • Has fixed size
Heap • Grows/shrinks as needed • New/delete (C++) • Malloc/free (C)
Stack • Grows/shrinks as needed • Stores “history” of function calls
Services • There are tasks that need to run in the background: • HTTP server software • Remote desktop software • Print servers • Anti-virus software • Windows services • Linux daemons
Services • Usually intended to run for the “duration of the boot” • Usually run with elevated privileges • Required due to the nature of what they do
Services • They are essentially just programs • Require… • …CPU time • …memory • …IO ports (sometimes)
Services • Typically 100+ services running at a time • How do we have resources to do any of “our” stuff? • Minimize the resources • Most services are just infinite loop • Listen for input, then react • Sleep in the middle
Services • How do we identify them? • Windows • Services tool • Linux • Usually end in a ‘d’ • E.g., httpd is the HTTP daemon • When do they start? • Some on start-up • Some “on-demand”
“init” process • It’s the first process • Process ID is 1 • Handles all of the start-up tasks • Makes use of other scripts to accomplish this • Stays around while OS is alive and kicking • Handles the shutdown
“init” process • Checks integrity of file systems • Check for devices and enable them • Allow terminal/GUI login • Generally, make sure things behave • Shut down the OS • Ask processes to stop • Kill all who ignore
“init” process • This is “extreme hand waving” • Check PIDs of “latest” process once you login • In Windows, I was in the 5,000s
Drivers • They’re kinda processes • They’re kinda not • Invoking ps will not show them • They listen for IO to/from devices • Upon getting IO, they act upon it • There’s a lot of information here • We’re going to avoid going too far* into the weeds *This is subjective
