Demo: The Five Operations

Allocate a kilobyte, write 0xc3 (ret) into it, read it back, jump to it, free it.

Run

make
./basic
gdb -batch -ex run -ex bt -ex 'info proc mappings' ./basic

Ask

• Which of the five steps failed? Say it before scrolling up.
• The address was just written to, so it exists. What is wrong with the access?
• Why would you want memory you can write to be impossible to run?