What is the role of the dynamic linker (ld-linux.so) in program execution?
It loads the executable and its shared libraries into memory, then resolves every symbol and relocation before main runs.
* What the dynamic linker builds: code and read-only data map low, writable data and heap above, shared libraries in the middle, and the stack at the top. *
The kernel actually launches the dynamic linker first (its path is recorded in the ELF header); the linker then maps in the program and its .so dependencies and patches everything up so the code can find the functions and data it calls.
The dynamic linker handles:
- Load the executable into memory
- Find required shared libraries (.so files)
- Load shared libraries into the process address space
- Resolve symbols - connect function calls to their implementations
- Perform relocations for position-independent code
Process memory layout after dynamic linking:
| Region | Contents |
|---|---|
| Kernel virtual memory | OS kernel space |
| User stack | Function call frames |
| Memory-mapped region | Shared libraries (.so) |
| Run-time heap | malloc allocations |
| Read/write segment | .data, .bss |
| Read-only segment | .init, .text, .rodata |
Tip: The dynamic linker itself is specified in the ELF header and loaded by the kernel before the program starts.
Go deeper:
ld.so(8) — dynamic linker/loader man page — the authoritative reference for how ld-linux.so finds, loads and binds shared objects.- LWN — How programs get run: ELF binaries — what the kernel does on
execve, and how it hands off to the dynamic linker. 
Dynamic linker (Wikipedia) — load-time linking across ELF, Windows and macOS.