Compare non-matching functions against expected output

This makes it possible to catch regressions for non-matching functions,
especially those that only have minor issues.

This also reclassifies some minor non-matchings as major non-matchings
whenever it's really not obvious to see that they are equivalent.

tools/dump_function.py

@@ -0,0 +1,62 @@
+#!/usr/bin/env python3
+
+import argparse
+from elftools.elf.elffile import ELFFile
+import diff_settings
+from pathlib import Path
+from typing import Any, Dict
+import utils
+
+config: Dict[str, Any] = {}
+diff_settings.apply(config, {})
+
+root = Path(__file__).parent.parent
+my_elf = ELFFile((root / config["myimg"]).open("rb"))
+my_symtab = my_elf.get_section_by_name(".symtab")
+if not my_symtab:
+    utils.fail(f'{config["myimg"]} has no symbol table')
+
+
+def get_file_offset(elf, addr: int) -> int:
+    for seg in elf.iter_segments():
+        if seg.header["p_type"] != "PT_LOAD":
+            continue
+        if seg["p_vaddr"] <= addr < seg["p_vaddr"] + seg["p_filesz"]:
+            return addr - seg["p_vaddr"] + seg["p_offset"]
+    assert False
+
+
+def get_symbol_file_offset_and_size(elf, table, name: str) -> (int, int):
+    syms = table.get_symbol_by_name(name)
+    if not syms or len(syms) != 1:
+        raise KeyError(name)
+    return get_file_offset(elf, syms[0]["st_value"]), syms[0]["st_size"]
+
+
+def get_fn_from_my_elf(name: str) -> bytes:
+    offset, size = get_symbol_file_offset_and_size(my_elf, my_symtab, name)
+    my_elf.stream.seek(offset)
+    return my_elf.stream.read(size)
+
+
+def dump_fn(name: str) -> None:
+    expected_dir = root / "expected"
+    try:
+        fn = get_fn_from_my_elf(name)
+        path = expected_dir / f"{name}.bin"
+        path.parent.mkdir(exist_ok=True)
+        path.write_bytes(fn)
+    except KeyError:
+        utils.fail("could not find function")
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("function_name", help="Name of the function to dump")
+    args = parser.parse_args()
+
+    dump_fn(args.function_name)
+
+
+if __name__ == "__main__":
+    main()