Overview

Code from OSTEP chapter Introduction.

To compile, just type:

prompt> make

See the highly primitive Makefile for details.

Then, run them! Examples:

prompt> ./cpu A

prompt> ./mem 1

prompt> ./threads 10000

prompt> ./io

Details

One issue with mem.c is that address space randomization is usually on by default. To turn it off:

macOS

From stackoverflow

Just compile/link as follows: gcc -o mem mem.c -Wall -Wl,-no_pie

Linux

From Giovanni Lagorio:

Under Linux you can disable ASLR, without using a debugger, in (at least) two ways:

• Use the command setarch to run a process with ASLR disabled; I typically run bash, with which I can execute examples, like this: setarch $(uname --machine) --addr-no-randomize /bin/bash
• Writing 0 into /proc/sys/kernel/randomize_va_space; you need to be root to do this and this change has (a non-permanent) effect on the whole system, which is something you probably don't want. I use this one only inside VMs.

FAQ

volatile int counter = 0

• Volatile used to indicate to the compiler that a variable's value may change unexpectedly.
• i.e, the compiler can't assume that the value of the variable won't change if it is not written to.
• Volatile is needed to make sure that compiler doesn't do any optimisations such as storing the value of counter in any temporary variables.
• But still, we are trying to access the value of the counter in the critical section without a lock.
• So a race condition can still occur due to our own fault of writing the incorrect programme.