Crate os_image_lens 

os_image_lens is a dependency-free, no_std-first crate that parses ELF64 images and produces a deterministic load plan suitable for bootloaders and kernels.

The core goal is to make a very common OS-development task boring and correct:

• Validate an ELF64 image from a byte slice.
• Enumerate PT_LOAD segments.
• Compute file ranges to copy and the in-memory ranges to zero.
• Derive a stable “what to map/copy/zero” plan without allocation.

This crate is intentionally strict and small:

• Rust edition: 2024
• External dependencies: none
• Unsafe in this crate: none

What this crate is

• A pure parser and planner for ELF64 binaries (typically kernel images).
• A way to keep bootloader and kernel loader code short, explicit, and testable.
• A crate that works in no_std environments by default.

What this crate is not

• It is not an ELF relocator or dynamic loader.
• It is not a filesystem, block device, or network fetcher.
• It does not allocate; if you want owned collections, build them outside this crate.

Minimal example

use os_image_lens::{Elf64, LoadSegmentKind};

let elf = Elf64::parse(bytes)?;

for seg in elf.load_segments() {
    let seg = seg?;
    match seg.kind() {
        LoadSegmentKind::CopyFromFile { file_range } => {
            let _to_copy = &bytes[file_range.start..file_range.end];
        }
        LoadSegmentKind::ZeroFill => {
            // memsz > filesz: you must zero the tail in memory.
        }
    }
}

Structs

Elf64

A parsed ELF64 image.

Elf64Header

Parsed, validated ELF64 file header.

ElfProgramHeader

A parsed ELF64 program header entry.

Error

A compact, allocation-free error used by all fallible APIs in this crate.

LoadSegment

A fully validated load segment derived from an ELF PT_LOAD program header.

SegmentPermissions

Permissions for a memory segment derived from ELF p_flags.

Enums

ElfDataEncoding

ELF data encoding (endianness) as reported by e_ident[EI_DATA].

ElfMachine

ELF machine type (e_machine).

ElfOsAbi

ELF OS ABI byte (e_ident[EI_OSABI]).

ElfType

ELF file type (e_type).

ErrorKind

Machine-matchable categories of parsing/planning errors.

LoadSegmentKind

A single copy/zero step a loader must perform for a PT_LOAD segment.