Implement a Simple Program Loader

OS Loaders Map Programs into Memory

The kernel's loader (ELF interpreter ld-linux-x86-64.so.2, Windows PE loader) reads the executable header, maps segments into virtual memory, sets permissions (RX for code, RW for data), and jumps to the entry point.

Load Process

Parse ELF PT_LOAD segments. mmap each at preferred or ASLR-randomized address. Zero BSS. Apply relocations for PIE. Transfer control to _start, which calls __libc_start_main then main.

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• ASLR randomizes base addresses per run
• Stack and heap grow after mapped segments
• Interpreter itself is loaded for dynamic binaries
• execve is the syscall that starts loading

Connecting to real compilers

Production compilers embed this step inside a longer pipeline. GCC flows through cpp, cc1, assembly, and ld; Clang uses the driver, Sema, LLVM IR passes, and a target backend. LLVM bitcode, JVM bytecode, and WASM are other familiar IRs at the same layer. The exercise isolates one pass so you can test it alone before chaining it to the next stage.

Why for this exercise

You will implement a simple program loader that maps segments and jumps to entry. This exercise requires parsing load headers, simulating memory mapping, and transferring control to the program start address.