Execute Instructions From The Heap

Question

Can I allocate a block on the heap, set its bytes to values that correspond to a function call and its parameters, then use the function call and dereference operators to execute that sequence?

Answer 1

So if I read you right you want to dynamically create CPU assembly instructions on the heap and execute them. A bit like self-modifying code. In theory that's possible, but in practice maybe not.

The problem is that the heap is in a data segment, and CPU's/operating systems nowadays have measures to prevent exactly this kind of behavior (it's called the NX bit, or No-eXecute bit for x86 CPUs). If a segement is marked as NX, you can't execute code from it. This was invented to stop computer virusses from using buffer overflows to place exectuable code in data/heap/stack memory and then try the calling program to execute such code.

Note that DLL's and libraries are loaded in the code segment, which of course allows code execution.