More informative README

intro/README.md

@@ -0,0 +1,51 @@
+# Overview
+
+Type "make" to build programs.
+
+See 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](stackoverflow.com/questions/23897963/documented-way-to-disable-aslr-on-os-x)
+
+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-permament) effect on the
+  whole system, which is something you probably don't want. I use this
+  one only inside VMs.
+
+
+