NOBITS with sh_offset==0 causes build::elf::Builder::write error

[allvpv]

Hello. AFAIK sh_offset field is completely meaningless in case of SHT_NOBITS section. Sometimes it is equal to 0: I encountered such a binary "in the wild". In this case, however, you cannot write the (valid) binary parsed by the ELF builder: it throws an error.

Probably the simplest possible solution would be to add another conditional (section.sh_type != SHT_NOBITS) around this fragments of code from build/elf.rs:

if section.sh_offset < writer.reserved_len() as u64 { ... }

// The input sh_offset needs to be preserved so that offsets in program
// headers are correct.
writer.reserve_until(section.sh_offset as usize);

if out_section.offset as u64 != section.sh_offset {...}

Let me know what do you think.

[philipc]

Thanks for the report. #645 fixes this similar to how you suggest.

Running on a few more binaries in the wild shows that there's likely other things that need fixing too.