Operating Systems 2026F: Tutorial 2 - Revision history

Soma: /* Setting up and connecting a VM */

2026-09-24T21:14:40Z

Setting up and connecting a VM

← Older revision		Revision as of 21:14, 24 September 2026
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	===Setting up and connecting a VM===		===Setting up and connecting a VM===

	Create a VM on the SCS openstack cluster as shown in ~~lecture~~. Make sure do the following:		Create a VM on the SCS openstack cluster as shown in the SCS documentation. Make sure do the following:
	* Choose the COMP3000-F26.2026-* instance snapshot image ONLY (others won't have the right software for later tutorials), use the latest one.		* Choose the COMP3000-F26.2026-* instance snapshot image ONLY (others won't have the right software for later tutorials), use the latest one.
	* Add the ping-ssh-egress security group, and		* Add the ping-ssh-egress security group, and

Soma at 16:18, 21 September 2026

2026-09-21T16:18:34Z

← Older revision		Revision as of 16:18, 21 September 2026
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	~~'''This tutorial is not yet finalized.'''~~

	In this tutorial we're going to look at how processes work at a low level: how they make system calls & library calls, how C and assembly compare, and and how memory is laid out.		In this tutorial we're going to look at how processes work at a low level: how they make system calls & library calls, how C and assembly compare, and and how memory is laid out.

Soma: /* Setting up and connecting a VM */

2026-09-21T14:25:37Z

Setting up and connecting a VM

← Older revision		Revision as of 14:25, 21 September 2026
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	Create a VM on the SCS openstack cluster as shown in lecture. Make sure do the following:		Create a VM on the SCS openstack cluster as shown in lecture. Make sure do the following:
	* Choose the ~~comp3000~~-~~2026f~~-* snapshot image ONLY (others won't have the right software for later tutorials), use the latest one.		* Choose the COMP3000-F26.2026-* instance snapshot image ONLY (others won't have the right software for later tutorials), use the latest one.
	* Add the ping-ssh-egress security group, and		* Add the ping-ssh-egress security group, and
	* Associating a floating IP address.		* Associating a floating IP address.

Soma at 15:02, 20 September 2026

2026-09-20T15:02:38Z

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	<ol>		<ol>
			<li>Join the class Team if you haven't already. Link is in brightspace.</li>
	<li>How does the environment of the Openstack VM compare to the LinuxOnTab one from Tutorial 1? Specifically, how do the following compare?</li>		<li>How does the environment of the Openstack VM compare to the LinuxOnTab one from Tutorial 1? Specifically, how do the following compare?</li>
	<ol style="list-style-type:lower-alpha">		<ol style="list-style-type:lower-alpha">

Soma at 19:26, 19 September 2026

2026-09-19T19:26:52Z

← Older revision		Revision as of 19:26, 19 September 2026
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	'''This tutorial is ~~still in development~~.'''		'''This tutorial is not yet finalized.'''

	In this tutorial we're going to look at how processes work at a low level: how they make system calls & library calls, how C and assembly compare, and and how memory is laid out.		In this tutorial we're going to look at how processes work at a low level: how they make system calls & library calls, how C and assembly compare, and and how memory is laid out.

Soma: /* Tasks */

2026-09-19T19:26:15Z

Tasks

← Older revision		Revision as of 19:26, 19 September 2026
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	<li>Compile and run [http://people.scs.carleton.ca/~soma/os-2019w/code/csimpleshell.c <tt>csimpleshell.c</tt>]. How does its functionality compare to that of bash? List at least 3 differences.</li>		<li>Compile and run [http://people.scs.carleton.ca/~soma/os-2019w/code/csimpleshell.c <tt>csimpleshell.c</tt>]. How does its functionality compare to that of bash? List at least 3 differences.</li>
	</ol>		</ol>


	===B: Function calls, library calls, and system calls===		===B: Function calls, library calls, and system calls===
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	# Change each malloc call to allocate more than 128K. What happens to the values of sbrk? Why? (Hint: use strace)		# Change each malloc call to allocate more than 128K. What happens to the values of sbrk? Why? (Hint: use strace)
	# Add more code and data to the program, and add more printf's to see where things are. Are things where you expect them to be?		# Add more code and data to the program, and add more printf's to see where things are. Are things where you expect them to be?


	==Code==		==Code==

Soma: /* C: Comparing C and assembly */

2026-09-19T19:23:22Z

C: Comparing C and assembly

← Older revision		Revision as of 19:23, 19 September 2026
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	* If a register is in parentheses, then it is being used as a "pointer" (it contains an address, so the CPU goes to that address and interacts with the memory there). If there is a number before the parentheses, it is an offset to the register's value.		* If a register is in parentheses, then it is being used as a "pointer" (it contains an address, so the CPU goes to that address and interacts with the memory there). If there is a number before the parentheses, it is an offset to the register's value.

	Resources on x86-64 assembly language:		Resources on x86-64 assembly language (only needed if you want to learn more):
	* [https://www.cs.cmu.edu/~fp/courses/15213-s07/misc/asm64-handout.pdf CMU introduction to x86-64]		* [https://www.cs.cmu.edu/~fp/courses/15213-s07/misc/asm64-handout.pdf CMU introduction to x86-64]
	* [https://en.wikibooks.org/wiki/X86_Assembly/GAS_Syntax AT&T/GNU Assembler syntax]		* [https://en.wikibooks.org/wiki/X86_Assembly/GAS_Syntax AT&T/GNU Assembler syntax]

Soma: /* C: Comparing C and assembly */

2026-09-19T19:22:14Z

C: Comparing C and assembly

← Older revision		Revision as of 19:22, 19 September 2026
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	* [https://en.wikibooks.org/wiki/X86_Assembly/GAS_Syntax AT&T/GNU Assembler syntax]		* [https://en.wikibooks.org/wiki/X86_Assembly/GAS_Syntax AT&T/GNU Assembler syntax]
	* [https://en.wikipedia.org/wiki/X86_calling_conventions#System_V_AMD64_ABI the Wikipedia article on calling conventions]		* [https://en.wikipedia.org/wiki/X86_calling_conventions#System_V_AMD64_ABI the Wikipedia article on calling conventions]


	# Using the <tt>nm</tt> command, see what symbols are defined in prog-static and prog-dyn. Which defines more symbols?		# Using the <tt>nm</tt> command, see what symbols are defined in prog-static and prog-dyn. Which defines more symbols?

Soma: /* C: Comparing C and assembly */

2026-09-19T19:22:02Z

C: Comparing C and assembly

← Older revision		Revision as of 19:22, 19 September 2026
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	Resources on x86-64 assembly language:		Resources on x86-64 assembly language:
	* [https://~~cs61~~.~~seas~~.~~harvard~~.edu/~~site~~/~~2018~~/~~Asm1~~/ ~~Eddie Kohler's assembly language basics (2018)~~] ~~(also see other notes from this class)~~		* [https://www.cs.cmu.edu/~fp/courses/15213-s07/misc/asm64-handout.pdf CMU introduction to x86-64]
	* [https://en.wikibooks.org/wiki/X86_Assembly/GAS_Syntax AT&T/GNU Assembler syntax]		* [https://en.wikibooks.org/wiki/X86_Assembly/GAS_Syntax AT&T/GNU Assembler syntax]
	* [https://en.wikipedia.org/wiki/X86_calling_conventions#System_V_AMD64_ABI the Wikipedia article on calling conventions]		* [https://en.wikipedia.org/wiki/X86_calling_conventions#System_V_AMD64_ABI the Wikipedia article on calling conventions]

Soma: /* B: Function calls, library calls, and system calls */

2026-09-19T19:20:43Z

B: Function calls, library calls, and system calls

← Older revision		Revision as of 19:20, 19 September 2026
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	# See what library calls prog-static produces by running <tt>ltrace -x '*' -o library-static.log ./prog-static</tt>. Do the same for <tt>prog-dyn</tt>. Which version generates more library calls? (Note: you will have to run <tt>sudo apt install ltrace</tt> to enable the command.)		# See what library calls prog-static produces by running <tt>ltrace -x '*' -o library-static.log ./prog-static</tt>. Do the same for <tt>prog-dyn</tt>. Which version generates more library calls? (Note: you will have to run <tt>sudo apt install ltrace</tt> to enable the command.)
	# Compile the program dynamically but with "lazy" linking: <tt>gcc -O2 -z lazy prog.c -o prog-dynlazy</tt>. Run <tt>ltrace -o library-lazy.log ./prog-dynlazy</tt>. How does the output of this compare to that of the previous ltrace?		# Compile the program dynamically but with "lazy" linking: <tt>gcc -O2 -z lazy prog.c -o prog-dynlazy</tt>. Run <tt>ltrace -o library-lazy.log ./prog-dynlazy</tt>. How does the output of this compare to that of the previous ltrace?
	# Use the command <tt>ls -l</tt> to see the metadata associated with prog.c and prog-dyn, and prog-static. Who owns these files? What group are they in? Do you notice any pattern with the permissions (rwx) associated with each file?
	# (optional) Look up the documentation for each of the system calls made by the static versions of the programs. You may need to append a 2 or 3 to the manpage invocation, e.g. "man 2 write" gets you the write system call documentation.		# (optional) Look up the documentation for each of the system calls made by the static versions of the programs. You may need to append a 2 or 3 to the manpage invocation, e.g. "man 2 write" gets you the write system call documentation.