Operating Systems 2015F: Tutorial 1 - Revision history

Soma at 14:42, 18 September 2015

2015-09-18T14:42:11Z

← Older revision		Revision as of 14:42, 18 September 2015
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	~~'''This tutorial is not yet finalized.'''~~

	In this tutorial you will be learning about 1) the difference between system calls, function calls, and library calls and 2) how processes are created.		In this tutorial you will be learning about 1) the difference between system calls, function calls, and library calls and 2) how processes are created.

Soma at 14:40, 18 September 2015

2015-09-18T14:40:43Z

@@ Line 1: / Line 1: @@
 '''This tutorial is not yet finalized.'''
-In this tutorial you will be learning how address spaces and segments are present on modern Linux systems.
+In this tutorial you will be learning about 1) the difference between system calls, function calls, and library calls and 2) how processes are created.
-For [http://homeostasis.scs.carleton.ca/~soma/os-2015f/code/hello.c hello.c], [http://homeostasis.scs.carleton.ca/~soma/os-2015f/code/syscall-hello.c syscall-hello.c], and [http://homeostasis.scs.carleton.ca/~soma/os-2014f/code/csimpleshell.c csimpleshell.c] do the following (substituting the appropriate source file for prog.c):
+==Function calls, library calls, and system calls==
 # Compile the program prog.c using <tt>gcc -O2 prog.c -o prog-dyn</tt> and run prog-dyn.  What does it do?
 # Statically compile and optimize prog.c by running <tt>gcc -O2 -static prog.c -o prog-static</tt>.  How does the size compare with <tt>prog</tt>?
@@ Line 19: / Line 21: @@
 # Examine the contents of object file, dynamically linked executable, and the statically linked executable using <tt>objdump -s</tt>
 # Re-run all of the previous gcc commands adding the "-v" flag.  What is all of that output?
-# (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 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.
@@ Line 50: / Line 63: @@
          return (int) result;
+}
 </source>

Soma at 14:32, 18 September 2015

2015-09-18T14:32:43Z

← Older revision		Revision as of 14:32, 18 September 2015
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	In this tutorial you will be learning how address spaces and segments are present on modern Linux systems.		In this tutorial you will be learning how address spaces and segments are present on modern Linux systems.

	For [http://homeostasis.scs.carleton.ca/~soma/os-~~2014f~~/code/hello.c hello.c], [http://homeostasis.scs.carleton.ca/~soma/os-~~2014f~~/code/syscall-hello.c syscall-hello.c], and [http://homeostasis.scs.carleton.ca/~soma/os-2014f/code/csimpleshell.c csimpleshell.c] ~~(from [[Operating Systems 2014F: Tutorial 2\|Tutorial 2]])~~ do the following (substituting the appropriate source file for prog.c):		For [http://homeostasis.scs.carleton.ca/~soma/os-2015f/code/hello.c hello.c], [http://homeostasis.scs.carleton.ca/~soma/os-2015f/code/syscall-hello.c syscall-hello.c], and [http://homeostasis.scs.carleton.ca/~soma/os-2014f/code/csimpleshell.c csimpleshell.c] do the following (substituting the appropriate source file for prog.c):
	# Compile the program prog.c using <tt>gcc -O2 prog.c -o prog-dyn</tt> and run prog-dyn. What does it do?		# Compile the program prog.c using <tt>gcc -O2 prog.c -o prog-dyn</tt> and run prog-dyn. What does it do?
	# Statically compile and optimize prog.c by running <tt>gcc -O2 -static prog.c -o prog-static</tt>. How does the size compare with <tt>prog</tt>?		# Statically compile and optimize prog.c by running <tt>gcc -O2 -static prog.c -o prog-static</tt>. How does the size compare with <tt>prog</tt>?

Soma: Created page with "'''This tutorial is not yet finalized.''' In this tutorial you will be learning how address spaces and segments are present on modern Linux systems. For [http://homeostasis...."

2015-09-18T14:32:12Z

Created page with "'''This tutorial is not yet finalized.''' In this tutorial you will be learning how address spaces and segments are present on modern Linux systems. For [http://homeostasis...."

New page

'''This tutorial is not yet finalized.'''

In this tutorial you will be learning how address spaces and segments are present on modern Linux systems.

For [http://homeostasis.scs.carleton.ca/~soma/os-2014f/code/hello.c hello.c], [http://homeostasis.scs.carleton.ca/~soma/os-2014f/code/syscall-hello.c syscall-hello.c], and [http://homeostasis.scs.carleton.ca/~soma/os-2014f/code/csimpleshell.c csimpleshell.c] (from [[Operating Systems 2014F: Tutorial 2|Tutorial 2]]) do the following (substituting the appropriate source file for prog.c):
# Compile the program prog.c using <tt>gcc -O2 prog.c -o prog-dyn</tt> and run prog-dyn. What does it do?
# Statically compile and optimize prog.c by running <tt>gcc -O2 -static prog.c -o prog-static</tt>. How does the size compare with <tt>prog</tt>?
# See what system calls prog-static produces by running <tt>strace -o syscalls-static.log ./prog-static</tt>. Do the same for <tt>prog-dyn</tt>. Which version generates more system calls?
# See what library calls prog-static produces by running <tt>ltrace -o library-static.log ./prog-static</tt>. Do the same for <tt>prog-dyn</tt>. Which version generates more library calls? (If ltrace isn't installed, run <tt>sudo apt-get install ltrace</tt>)
# Using the <tt>nm</tt> command, see what symbols are defined in prog-static and prog-dyn.
# Run the command <tt>gcc -c -O2 prog.c</tt> to produce an object file. What file was produced? What symbols does it define?
# Look at the assembly code of the program by running <tt>gcc -S -O2 prog.c</tt>. What file was produced? Identify the following:
#* A function call
#* A system call (if any)
#* A global/static variable (if any)
#* A local variable
# Disassemble the object file using <tt>objdump -d</tt>. How does this disassembly compare with the output from gcc -S?
# Examine the headers of object file, dynamically linked executable, and the statically linked executable using <tt>objdump -h</tt>
# Examine the contents of object file, dynamically linked executable, and the statically linked executable using <tt>objdump -s</tt>
# Re-run all of the previous gcc commands adding the "-v" flag. What is all of that output?
# (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 to the manpage invocation, e.g. "man 2 write" gets you the write system call documentation.

==Code==

===hello.c===
<source lang="c">
#include <stdio.h>

int main(int argc, char *argv[]) {

printf("Hello world!\n");

return 0;
}
</source>

===syscall-hello.c===
<source lang="c">
#include <unistd.h>
#include <sys/syscall.h>

char *buf = "Hello world!\n";

int main(int argc, char *argv) {
size_t result;

/* "man 2 write" to see arguments to write syscall */
result = syscall(SYS_write, 1, buf, 13);

return (int) result;
}
</source>