linker-scripts

To write a GNU ld linker script for embedded bare-metal targets, you use the MEMORY and SECTIONS commands to define memory regions and place code. Directives like PROVIDE, KEEP, and ALIGN help control symbol placement and section boundaries.

VMA (Virtual Memory Address) is where the section runs at runtime, while LMA (Load Memory Address) is where it is loaded. Managing VMA vs LMA correctly in a linker script is essential for code relocation in embedded systems.

To place a function in fast internal RAM, you define a custom memory region in the linker script and attribute the function to that section. This ensures critical code, like an interrupt handler on an STM32, is placed precisely where needed.

Startup code initializes .bss and .data sections by copying initialized data from flash to RAM and zeroing the .bss section. The linker script defines the section boundaries and symbols needed for this startup initialization process.

You use the KEEP directive in a linker script when you need to prevent the garbage collector from removing seemingly unused sections. This is crucial for retaining specific startup code or interrupt vector tables in embedded bare-metal projects.