Embedded Systems · Cluster
Firmware Updates
Bootloaders, A/B images, and rollback.
- 01 What a Bootloader Must Establish Before Jumping to an Application The register values, memory layout, and validation a bootloader owes an application image, and why the transfer has to be a tail branch rather than an ordinary call.
- 02 Image Headers and Integrity Validation Before Execution How a bootloader decides an image is complete and well-formed, which fields belong in the header, and why a checksum over the wrong range is worse than none.
- 03 Dual-Bank Slots and How a Bootloader Picks One Why two firmware slots turn an in-place overwrite into a recoverable operation, how the boot decision is made from metadata, and what the doubling of flash costs.
- 04 Erase Granularity, Write Ordering, and Power Loss During a Flash Write Why a firmware update cannot be made atomic at the byte level, how sector granularity dictates the update algorithm, and what a partially erased sector actually contains.
- 05 Chunked Transfer and Retransmission in Firmware Delivery How an image crosses a slow or unreliable link in numbered chunks, why the window size is bounded by the receiver buffer, and where the retry logic belongs.
- 06 Trial Boot, Confirmation, and Automatic Rollback How a new image is allowed to run under supervision, what counts as proof that it works, and why the confirmation step has to come from the application rather than the bootloader.
- 07 Boot Metadata Persistence and the Commit Record The record format that survives an interrupted write, how many copies are enough, and why the sequence number rather than the timestamp decides which copy wins.
- 08 Signature Verification and Where the Root Key Lives How a constrained bootloader verifies an image signature, which algorithms fit in its budget, and why storing the public key in flash defeats the purpose.
- 09 Anti-Rollback Counters and Version Monotonicity Why a validly signed older image is still a downgrade attack, how a monotonic counter is kept without a battery, and what the counter costs in flash endurance.
- 10 Delta Updates: Applying a Patch to an Image Already in Flash How a difference between two firmware builds is expressed as copy and insert operations, why block alignment decides the patch size, and where the reconstructed image goes.