lotus,azalea: officially reserve the top 4k of flash for SPI_FLAGS #39
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This has been built, tested and deployed to hardware. The device in question still works. 😁 |
Right now, the configuration storage support in lotus/src/flash_storage.c claims overship of the top 0x1000 bytes of flash and stores non-volatile configuration data in it. However, the last 0x20 bytes of flash contain the RW_FWID (RW version) section. In addition, RW_FW is specified as covering the entire top 0x40000 bytes of flash. In short, flash looks roughly like this (not to scale) +----------------------------------+-40000------------~----------------+ | RO_FW | RW_FW | | RO_FRID | RW_FWID | +----------------------------------+------------------~--------^-7FFE0-+ flash_storage can, if it grows large enough, corrupt the RW version ID. If the RW firmware _also_ grows large enough, flash_storage can overwrite part of it (!). +----------------------------------+-40000------------~--+-7F000-------+ | RO_FW | RW_FW |spi flag spi | | RO_FRID | |flag Rp_ WlD | +----------------------------------+------------------~--+-~---^-7FFE0-+ This change moves RW_FWID down to 0x7EFE0 and indicates in the FMAP that the RW section can only occupy the top 0x3F000 bytes of flash. The final layout looks more like this: +----------------------------------+-40000----~----------+-7F000-------+ | RO_FW | RW_FW |spi flag spi | | RO_FRID | RW_FWID |flag spi fla | +----------------------------------+----------~--^-7EFE0-+-------------+ If the RW section grows too large for SPI flags, that will result in a hard build break. That's probably better than runtime corruption of its .text. :)
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kiram9
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Jan 3, 2024
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Right now, the configuration storage support in
lotus/src/flash_storage.c claims overship of the top 0x1000 bytes of flash and stores non-volatile configuration data in it.
However, the last 0x20 bytes of flash contain the RW_FWID (RW version) section. In addition, RW_FW is specified as covering the entire top 0x40000 bytes of flash.
In short, flash looks roughly like this (not to scale)
flash_storage can, if it grows large enough, corrupt the RW version ID. If the RW firmware also grows large enough, flash_storage can overwrite part of it (!).
This change moves RW_FWID down to 0x7EFE0 and indicates in the FMAP that the RW section can only occupy the top 0x3F000 bytes of flash.
The final layout looks more like this:
If the RW section grows too large for SPI flags, it will result in a hard build break.
That's probably much better than runtime corruption of its .text. :)