• Johny Mattsson's avatar
    Reworked linker magic to work with IDF 3.3 (#2805) · 51912d55
    Johny Mattsson authored
    With the IDF asserting full control over the linker scripts and insisting on
    the application description being the first entry in the .flash.rodata
    section, or previous method of doing link-time arrays stopped working.
    Why? Because the build patched in a SHA256 digest straight into our arrays.
    
    With the limited language of the gcc linker scripts I could find no other
    way of getting it in cleanly.
    
    The IDF "linker fragments" support can not be made to work for our needs:
      - no support for setting alignment before including objects
      - no support for declaring symbols
      - no support for adding our terminating zeros
      - insists on grouping objects by lib rather than by declared grouping,
        which means we could at most have a single link-time-array using
        the IDF mechanism
      - also does not like underscores in section names, but that's just an
        annoyance
    
    So, the least bad option that I could come up with was to use a project-wide
    makefile snippet to add a target in-between the IDF's generation of the
    esp32.project.ld file, and the linking of our NodeMCU.elf. In this target
    we read in the esp32.project.ld linker script, check whether we have our
    arrays in there, and if not rewrites the linker script.
    
    Oh, and the esp32.project.ld file only came into existence on the IDF 3.3
    branch, so I had to change up the IDF to the latest release/3.3 as well.
    I would've preferred a stable tag, but the v3.3-beta3 had a really nasty
    regression for us (can't add partition entry), so that was a no-go.
    51912d55
add_rodata_ld.sh 548 Bytes