How to write self-modifying code in x86 assembly

Question

I\'m looking at writing a JIT compiler for a hobby virtual machine I\'ve been working on recently. I know a bit of assembly, (I\'m mainly a C programmer. I can read most ass

Answer 1

Since you're writing a JIT compiler, you probably don't want self-modifying code, you want to generate executable code at runtime. These are two different things. Self-modifying code is code that is modified after it has already started running. Self-modifying code has a large performance penalty on modern processors, and therefore would be undesirable for a JIT compiler.

Generating executable code at runtime should be a simple matter of mmap()ing some memory with PROT_EXEC and PROT_WRITE permissions. You could also call mprotect() on some memory you allocated yourself, as dwelch did above.