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Secure boot for 32-bit Microcontrollers!
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DRAM overflow of `.bss.sector_buffers` when slot partition is bigger then 4MB on esp32s3 (N16R8) with Zephyr #2094

Open FacepalmMute opened 5 days ago

FacepalmMute commented 5 days ago

After adjusting my flash map, I noticed the following error:

/usr/local/zephyr-sdk-0.16.8/xtensa-espressif_esp32s3_zephyr-elf/bin/../lib/gcc/xtensa-espressif_esp32s3_zephyr-elf/12.2.0/../../../../xtensa-espressif_esp32s3_zephyr-elf/bin/ld.bfd: zephyr/zephyr_pre0.elf section '.bss' will not fit in region 'dram_seg'
/usr/local/zephyr-sdk-0.16.8/xtensa-espressif_esp32s3_zephyr-elf/bin/../lib/gcc/xtensa-espressif_esp32s3_zephyr-elf/12.2.0/../../../../xtensa-espressif_esp32s3_zephyr-elf/bin/ld.bfd: DRAM segment data does not fit.
/usr/local/zephyr-sdk-0.16.8/xtensa-espressif_esp32s3_zephyr-elf/bin/../lib/gcc/xtensa-espressif_esp32s3_zephyr-elf/12.2.0/../../../../xtensa-espressif_esp32s3_zephyr-elf/bin/ld.bfd: region `dram_seg' overflowed by 7152 bytes

This error occurs whenever either of the two slot partitions is assigned more than 4MB. In the case above, it was assigned 6MB.

A comparison of the ´zephyr_pre0.map´ from both compilations shows that sector_buffers requires more DRAM:


.bss.sector_buffers
                0x000000003fcc5c8c     0x4000 app/libapp.a(loader.c.obj)

 .bss.sector_buffers
                0x000000003fcc5c8c     0x6000 app/libapp.a(loader.c.obj)

As a workaround, I increased ´BOOTLOADER_DRAM_SEG_LEN´ in ´zephyr/soc/espressif/esp32s3/memory.h´ by 0x2000. The error no longer occurs, but I am not sure about the side effects in regards to secure boot and other security features.

almir-okato commented 2 days ago

This is related to the MCUboot Zephyr port for Espressif chips, @marekmatej could you help take a look at this?