mirror of https://github.com/wolfSSL/wolfBoot.git
68 lines
2.7 KiB
Markdown
68 lines
2.7 KiB
Markdown
# Flash partitions
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## Flash memory partitions
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To integrate wolfBoot you need to partition the flash into
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separate areas (slots), according to the geometry of the flash memory.
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Images boundaries **must** be aligned to physical sectors, because the
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bootloader erases all the flash sectors before storing a firmware image.
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The flash memory of the target is partitioned into the following areas:
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- Bootloader partition, at the beginning of the flash
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- Primary slot (boot partition) starting at address `FLASH_AREA_IMAGE_0_OFFSET`
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- Secondary slot (upgrade partition) starting at address `FLASH_AREA_IMAGE_1_OFFSET`
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- Scratch space (swap partition) starting at address `FLASH_AREA_IMAGE_SCRATCH_OFFSET`
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A proper partitioning configuration must be set up for the specific use, by setting
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the values for offsets and sizes in [include/target.h](../include/target.h).
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### Bootloader partition
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This partition is usually very small, and only contains the bootloader code and data.
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Public keys pre-authorized during factory image creations are automatically stored
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as part of the firmware image.
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### Primary slot (boot partition)
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This is the only partition from where it is possible to chain-load and execute a
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firmware image. The firmware image must be linked so that its entry-point is at address
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`FLASH_AREA_IMAGE_0_OFFSET + 256`.
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### Secondary slot (upgrade partition)
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The running firmware is responsible of transferring a new firmware image through a secure channel,
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and store it in the secondary slot. If an upgrade is initiated, the bootloader will replace or swap
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the firmware in the boot partition at the next reboot.
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## Example 512KB partitioning on STM32-F407
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The example firmware provided in the `test-app` is configured to boot from the primary partition
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starting at address 0x20000. The flash layout is provided by the default example using the following
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configuration in `target.h`:
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```C
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#define FLASH_AREA_IMAGE_0_OFFSET 0x20000
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#define FLASH_AREA_IMAGE_0_SIZE 0x20000
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#define FLASH_AREA_IMAGE_1_OFFSET 0x40000
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#define FLASH_AREA_IMAGE_1_SIZE 0x20000
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#define FLASH_AREA_IMAGE_SCRATCH_OFFSET 0x60000
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#define FLASH_AREA_IMAGE_SCRATCH_SIZE 0x20000
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```
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which results in the following partition configuration:
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This configuration demonstrates one of the possible layouts, with the slots
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aligned to the beginning of the physical sector on the flash.
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The entry point for all the runnable firmware images on this target will be `0x20100`,
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256 Bytes after the beginning of the first flash partition. This is due to the presence
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of the firmware image header at the beginning of the partition, as explained more in details
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in [Firmware image](firmware_image.md)
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