Operating Systems 2017F: Tutorial 6: Difference between revisions

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In this tutorial you will be running and modifying [http://homeostasis.scs.carleton.ca/~soma/os-2017f/code/lec16/newgetpid.zip newgetpid.c] from [[Operating Systems 2017F Lecture 16|Lecture 16]].
In this tutorial you will be running and modifying [http://homeostasis.scs.carleton.ca/~soma/os-2017f/code/lec16/newgetpid.zip newgetpid.c] from [[Operating Systems 2017F Lecture 16|Lecture 16]].  You will likely want to look at the Linux kernel source, particularly [http://elixir.free-electrons.com/linux/v4.4.88/source/kernel/sys.c kernel/sys.c].
 
==Tasks==
 
# Build and run newgetpid.c as demonstrated in Lecture 16 and as we did in the previous tutorial.
# What type is "current"?  How can you figure this out?
# Modify newgetpid.c so that it creates a device file /dev/describe rather than /dev/newgetpid.
# Make /dev/describe output the calling process's parent ID (ppid), user ID (uid), group ID (gid), effective user ID (euid), and effective group ID (egid).
# '''(Advanced)''' Modify /dev/describe so that if you write a process ID to it, it will output the information on the provided process.  To make this work, you'll need to:
## Find the right task struct following the implementation of the [http://elixir.free-electrons.com/linux/v4.4.88/source/kernel/signal.c#L2855 kill system call], and how it [http://elixir.free-electrons.com/linux/v4.4.88/source/kernel/signal.c#L1388 looks up the pid struct] and then [http://elixir.free-electrons.com/linux/v4.4.88/ident/kill_pid_info kill_pid_info() iterates through the task list].

Revision as of 21:21, 12 November 2017

In this tutorial you will be running and modifying newgetpid.c from Lecture 16. You will likely want to look at the Linux kernel source, particularly kernel/sys.c.

Tasks

  1. Build and run newgetpid.c as demonstrated in Lecture 16 and as we did in the previous tutorial.
  2. What type is "current"? How can you figure this out?
  3. Modify newgetpid.c so that it creates a device file /dev/describe rather than /dev/newgetpid.
  4. Make /dev/describe output the calling process's parent ID (ppid), user ID (uid), group ID (gid), effective user ID (euid), and effective group ID (egid).
  5. (Advanced) Modify /dev/describe so that if you write a process ID to it, it will output the information on the provided process. To make this work, you'll need to:
    1. Find the right task struct following the implementation of the kill system call, and how it looks up the pid struct and then kill_pid_info() iterates through the task list.