UF2 files with address gaps are not flashed correctly

[timokroeger]

The rp2040 bootrom uses the uf2 block number to determine when to erase a flash page:
https://github.com/raspberrypi/pico-bootrom/blob/c09c7f08550e8a36fc38dc74f8873b9576de99eb/bootrom/virtual_disk.c#L205

When there is a gap in target addresses between two uf2 blocks this logic does not work out.
As a workaround align all uf2 blocks to page erase boundary, so that the bootrom always removes the correct flash page.

[timokroeger]

From the datasheet Section 2.8.4.2. UF2 Format Details:
"Note that flash is erased a 4K sector at a time, so writing to only a subset of a 4K flash sector will leave the rest of that
flash sector undefined. Beyond that there is no requirement that a binary be contiguous."

I guess this also needs an update.

[kilograham]

can you please attach a UF2 with some holes? I want to test a slight fix change

[timokroeger]

Sure: holes.zip

The hole comes from RO data with huge alignment:

const uint8_t some_data[128] __attribute__((aligned(32 * 1024)));

[kilograham]

ha i should have said holey ELF...
also, what compiler/version are you using? I've never seen GCC leave an actual hole.

[timokroeger]

elf_with_holes.zip

I‘m using a recent version of GCC on windows:

> arm-none-eabi-gcc -v
Using built-in specs.
COLLECT_GCC=C:\Coding\gcc-arm-none-eabi-10.3-2021.10\bin\arm-none-eabi-gcc.exe
COLLECT_LTO_WRAPPER=c:/coding/gcc-arm-none-eabi-10.3-2021.10/bin/../lib/gcc/arm-none-eabi/10.3.1/lto-wrapper.exe
Target: arm-none-eabi
Configured with: /mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/src/gcc/configure --build=x86_64-linux-gnu --host=i686-w64-mingw32 --target=arm-none-eabi --prefix=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-mingw --libexecdir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-mingw/lib --infodir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-mingw/share/doc/gcc-arm-none-eabi/info --mandir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-mingw/share/doc/gcc-arm-none-eabi/man --htmldir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-mingw/share/doc/gcc-arm-none-eabi/html --pdfdir=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-mingw/share/doc/gcc-arm-none-eabi/pdf --enable-languages=c,c++ --enable-mingw-wildcard --disable-decimal-float --disable-libffi --disable-libgomp --disable-libmudflap --disable-libquadmath --disable-libssp --disable-libstdcxx-pch --disable-nls --disable-shared --disable-threads --disable-tls --with-gnu-as --with-gnu-ld --with-headers=yes --with-newlib --with-python-dir=share/gcc-arm-none-eabi --with-sysroot=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/install-mingw/arm-none-eabi --with-libiconv-prefix=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-mingw/host-libs/usr --with-gmp=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-mingw/host-libs/usr --with-mpfr=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-mingw/host-libs/usr --with-mpc=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-mingw/host-libs/usr --with-isl=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-mingw/host-libs/usr --with-libelf=/mnt/workspace/workspace/GCC-10-pipeline/jenkins-GCC-10-pipeline-338_20211018_1634516203/build-mingw/host-libs/usr --with-host-libstdcxx='-static-libgcc -Wl,-Bstatic,-lstdc++,-Bdynamic -lm' --with-pkgversion='GNU Arm Embedded Toolchain 10.3-2021.10' --with-multilib-list=rmprofile,aprofile
Thread model: single
Supported LTO compression algorithms: zlib
gcc version 10.3.1 20210824 (release) (GNU Arm Embedded Toolchain 10.3-2021.10)

[kilograham]

fixed by #800

[kilograham]

merged into develop