Operating Systems 2014F: Tutorial 4 - Revision history

Soma at 14:37, 26 September 2014

2014-09-26T14:37:30Z

← Older revision		Revision as of 14:37, 26 September 2014
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	# 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>?
	# See what system calls prog-static produces by running <tt>strace -o static.log ./prog-static</tt>. Do the same for <tt>prog-dyn</tt>. Which version generates more system calls?		# 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.		# 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?		# Run the command <tt>gcc -c -O2 prog.c</tt> to produce an object file. What file was produced? What symbols does it define?

Soma at 14:35, 26 September 2014

2014-09-26T14:35:34Z

← Older revision		Revision as of 14:35, 26 September 2014
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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 hello.c, syscall-hello.c, and csimpleshell.c (from Tutorial 3) do the following (substituting the appropriate source file for prog.c):		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?		# 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 "In this tutorial you will be learning how address spaces and segments are present on modern Linux systems. For hello.c, syscall-hello.c, and csimpleshell.c (from Tutorial 3) ..."

2014-09-26T14:32:57Z

Created page with "In this tutorial you will be learning how address spaces and segments are present on modern Linux systems. For hello.c, syscall-hello.c, and csimpleshell.c (from Tutorial 3) ..."

New page

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

For hello.c, syscall-hello.c, and csimpleshell.c (from Tutorial 3) 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 static.log ./prog-static</tt>. Do the same for <tt>prog-dyn</tt>. Which version generates more system calls?
# 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>