How to Find the Memory Address of a Symbol in an ELF File

Here’s a handy tip that came up during some work with SEGGER RTT (Real Time Transfer).

When initializing an RTT session, you need to provide the memory address of the RTT static control block variable. While it’s possible to dig through your generated .map file, there's a faster way:

arm-none-eabi-nm blink.elf | grep _SEGGER_RTT
20000000 B _SEGGER_RTT

By piping the output of arm-none-eabi-nm (which lists all symbols in your .elf file) to grep, you can quickly isolate and retrieve the memory address of your desired symbol.

Note: For Windows users, grep is typically a Linux command. However, you can easily use this trick with tools like WSL (Windows Subsystem for Linux), Cmder, or Git Bash.

arm-none-eabi-nm firmware.elf | grep foo
1000033c T foo

This technique isn't limited to variable addresses, it's equally useful for finding function or constant data addresses. Variable symbols are typically stored in volatile RAM, while function code and constant data usually reside in non-volatile ROM or Flash memory, reflecting their runtime mutability or immutability.