elflib/dist/writer.js

ELF file reader and writer

import { RPL } from './rplsections.js';
import * as ELF from './types/index.js';
/** @deprecated Write a buffer of data to a larger buffer from an offset */
export function writeBufferToBuffer(buf, data, offset) {
    if ((offset + data.byteLength) > buf.byteLength)
        throw new Error('Cannot write outside destination buffer size.');
    if (offset < 0)
        throw new Error('Offset must be greater than zero.');
    for (let i = 0; i < data.byteLength; i++)
        buf.writeUInt8(data[i], offset + i);
    return buf;
}
// TODO: Unhardcode this from ELF32 Big Endian + Segments support
export async function packElf(elf) {
    if (elf.header.class !== ELF.Class.ELF32 || elf.header.endian !== ELF.Endian.Big)
        throw new Error('Only ELF32 Big Endian packing is currently supported.');
    if (elf.header.programHeadersEntryCount !== 0 || /*elf.segments.length !== 0 ||*/ elf.header.programHeadersOffset !== 0)
        console.warn('ELF Segment and program headers packing is not currently supported. Remaining ELF data will still attempt to be packed.');
    let output = Buffer.alloc(elf.header.sectionHeadersOffset + (elf.sections.length * elf.header.sectionHeadersEntrySize));
    packELFHeader(elf).copy(Uint8Array.from(output), 0);
    elf.updateSectionHeaders();
    packELFSectionHeaders(elf).copy(Uint8Array.from(output), elf.header.sectionHeadersOffset);
    const sections = elf.sections.filter(section => section.offset !== 0).sort((a, b) => a.offset - b.offset);
    for (let i = 0; i < sections.length; i++) {
        const section = sections[i];
        output = Buffer.concat([Uint8Array.from(output), Uint8Array.from(Buffer.alloc(section.offset - Uint8Array.from(output).byteLength + section.size))]);
        if (section.type === ELF.SectionType.RPLCrcs) {
            (await RPL.packCrcSection(section, elf)).copy(Uint8Array.from(output), section.offset);
            continue;
        }
        if (RPL.isFileInfoSection(section)) {
            RPL.packFileInfoSection(section).copy(Uint8Array.from(output), section.offset);
            continue;
        }
        Buffer.from(section.data).copy(Uint8Array.from(output), section.offset);
    }
    const align = (output.byteLength + 15 & -16) - output.byteLength;
    if (align !== 0)
        return Buffer.concat([Uint8Array.from(output), Uint8Array.from(Buffer.alloc(align))]);
    return output;
}
/** Pack the header of an ELF file to binary. */
function packELFHeader(elf) {
    const header = Buffer.alloc(elf.header.headerSize);
    let ix = 0;
    header.write('\x7FELF', ix);
    ix += 4;
    header.writeUInt8(elf.header.class, ix);
    ix += 1;
    header.writeUInt8(elf.header.endian, ix);
    ix += 1;
    header.writeUInt8(elf.header.version, ix);
    ix += 1;
    header.writeUInt8(elf.header.abi, ix);
    ix += 1;
    header.writeUInt8(elf.header.abiVersion, ix);
    ix += 1;
    header.write('\0'.repeat(7), ix);
    ix += 7; // Padding
    header.writeUInt16BE(elf.header.type, ix);
    ix += 2;
    header.writeUInt16BE(elf.header.isa, ix);
    ix += 2;
    header.writeUInt32BE(elf.header.isaVersion, ix);
    ix += 4;
    header.writeUInt32BE(Number(elf.header.entryPoint), ix);
    ix += 4;
    header.writeUInt32BE(elf.header.programHeadersOffset, ix);
    ix += 4;
    header.writeUInt32BE(elf.header.sectionHeadersOffset, ix);
    ix += 4;
    header.writeUInt32BE(elf.header.flags, ix);
    ix += 4;
    header.writeUInt16BE(elf.header.headerSize, ix);
    ix += 2;
    header.writeUInt16BE(elf.header.programHeadersEntrySize, ix);
    ix += 2;
    header.writeUInt16BE(elf.header.programHeadersEntryCount, ix);
    ix += 2;
    header.writeUInt16BE(elf.header.sectionHeadersEntrySize, ix);
    ix += 2;
    header.writeUInt16BE(elf.sections.length, ix);
    ix += 2;
    header.writeUInt16BE(elf.header.shstrIndex, ix);
    ix += 2;
    return header;
}
/** Pack the section header table of an ELF file to binary. */
export function packELFSectionHeaders(elf) {
    const sectionHeaders = Buffer.alloc(elf.sections.length * elf.header.sectionHeadersEntrySize);
    let ix = 0;
    elf.sections.forEach((section) => {
        if (section.type === ELF.SectionType.RPLCrcs)
            section.size = elf.sections.length * section.entSize;
        sectionHeaders.writeUInt32BE(section.nameOffset, ix);
        ix += 4;
        sectionHeaders.writeUInt32BE(section.type, ix);
        ix += 4;
        sectionHeaders.writeUInt32BE(section.flags, ix);
        ix += 4;
        sectionHeaders.writeUInt32BE(Number(section.addr), ix);
        ix += 4;
        sectionHeaders.writeUInt32BE(section.offset, ix);
        ix += 4;
        sectionHeaders.writeUInt32BE(section.size, ix);
        ix += 4;
        sectionHeaders.writeUInt32BE(section.link, ix);
        ix += 4;
        sectionHeaders.writeUInt32BE(section.info, ix);
        ix += 4;
        sectionHeaders.writeUInt32BE(section.addrAlign, ix);
        ix += 4;
        sectionHeaders.writeUInt32BE(section.entSize, ix);
        ix += 4;
    });
    return sectionHeaders;
}