Courses/Computer Science/CPSC 457.W2012/Lecture Notes/Creation

Process Creation

In this session, we will continue our examination of how processes come to be. We will start by considering what a process is (see task_struct). We will also briefly trace our understanding of control flow involving invoking parts of the system call interface.

We will also have a multi-perspective look at the routines

• execve
• fork / clone / vfork

involved in process creation. We will glance over the source code of the kernel's routines for creating (or cloning) a process and loading an executable (i.e., ELF) image into a process address space. They lead to a chain of procedures in the OS that is a bit deeper and more complex than the system call interface might otherwise imply.

Notes

• slides from today (augmented deck from last time)
• wiki and piazza announcement
• NSERC USRA 2012 announcement
• Recall: Outcomes listed on Course Intro page (how are we doing with that list of skills?)
• HW1 released (due Sat 28 Jan)
• Virtual Machines (needed for HW2, 4, 5)
  • Amazon EC2 free micro instances
  • VMWare Player free samples
  • BackTrack
  • other "bootable" CDROM or ISO image (Fedora, Ubuntu,...)
  • other...
• finish up shellcode example for execve(2)
  • how to invoke execve with an argument of /bin/bash
  • http://www.shell-storm.org/shellcode/files/shellcode-606.php
• examine fork(2)
  • man 2 fork
  • do_fork routine: http://lxr.linux.no/#linux+v2.6.27.41/kernel/fork.c#L1314
  • copy_process routine: http://lxr.linux.no/#linux+v2.6.27.41/kernel/fork.c#L887

Readings

• MOS: Section 2.1: Processes (this should be partly review of what we've talked about in class)
• MOS: Section 3.2.1: The Notion of an Address Space
• MOS: Section 3.7 (all except 3.7.2) (this should review some of what we touched on in the previous class and lay some groundwork for talking about memory management)
• MOS: Section 10.2.5 (Linux kernel structure)
• MOS: Section 10.3.1 (about processes in Linux) should reinforce some class discussion

Reminder: Tomorrow is the last day to drop a class.