BootloaderStacks

BootloaderStacks refers to a design pattern used in bootloaders to manage multiple preallocated stack regions across different boot phases. By dedicating separate stacks to distinct stages of the boot process, bootloaders can achieve deterministic behavior, reduce interference between initialization code and later firmware, and improve security through isolation.

Structure and operation: A typical implementation reserves several statically allocated memory blocks, each sized to the needs of a boot stage and aligned to architectural requirements. Common stacks include an initial stack used during early reset handling, a vector or interrupt stack for early interrupt handling, and a general boot stage stack for initialization tasks. Some designs include a fallback or emergency stack to handle rare failure paths. The boot ROM or startup code initializes these regions, sets the initial stack pointer to the primary stack, and transitions between stages by saving and restoring stack pointers when switching contexts. Linker scripts or memory maps place the stacks at known addresses and guard regions or canaries protect against overflow.

Benefits and trade-offs: BootloaderStacks provide deterministic RAM usage, safer handling of interrupts during the earliest boot, and clearer separation between low-level boot code and later application code. They can simplify debugging by isolating stack frames to specific stages. However, they consume RAM that would otherwise be available to the application, require careful sizing and validation to avoid overflow, and increase complexity of the boot flow.

Applications and related concepts: used in microcontroller bootloaders, secure boot flows, and firmware update schemes; related to stack switching, multiple stacks, and early-boot memory management.