refactor(elf): carry parsed header facts into native consumers

src/native/elf/KernelModuleParser.ts

@@ -92,15 +92,13 @@ const baseLimitations = (): Limitations => [
 ];
 
 const headerFacts = (
-  bytes: Buffer,
-  image: BinaryContainer,
+  image: Extract<BinaryContainer, { format: "elf" }>,
 ): Pick<Report, "format" | "byte_order" | "machine" | "type" | "type_name"> => {
-  const little = image.byte_order === "little";
-  const type = little ? bytes.readUInt16LE(16) : bytes.readUInt16BE(16);
+  const { type } = image.elf;
   return {
     format: image.bits === 64 ? "elf64" : "elf32",
     byte_order: image.byte_order,
-    machine: image.format === "elf" ? image.elf.machine : null,
+    machine: image.elf.machine,
     type,
     type_name: elfObjectTypeName(type),
   };
@@ -514,7 +512,7 @@ export const parseKernelModule = (
   if (compression !== null)
     return unsupportedCompression(artifact, compression);
   const image = readElfImage(bytes);
-  const facts = headerFacts(bytes, image);
+  const facts = headerFacts(image);
   if (facts.type !== 1) return notApplicable(artifact, facts);
   const sections = image.sections.filter(
     (section): section is ElfSection => section.format === "elf",

src/native/metadata/BinaryContainer.ts

@@ -142,6 +142,7 @@ export type BinaryContainer = BinaryContainerFacts &
         readonly format: "elf";
         readonly elf: {
           readonly machine: number;
+          readonly type: number;
           readonly dynamicSegments: readonly ElfDynamicSegment[];
         };
       }

src/native/metadata/ElfImage.ts

@@ -13,7 +13,9 @@ import { elfArchitecture } from "../../domain/elfFixedHeader.js";
 import { readElfDirectoryFromBuffer } from "./NativeSectionDirectory.js";
 
 /** Read ELF sections and file-backed program mappings without interpreting language metadata. */
-export const readElfImage = (bytes: Buffer): BinaryContainer => {
+export const readElfImage = (
+  bytes: Buffer,
+): Extract<BinaryContainer, { format: "elf" }> => {
   const directory = readElfDirectoryFromBuffer(bytes);
   const { bits } = directory;
   const reader = new BinaryReader(bytes, directory.little);
@@ -86,7 +88,11 @@ export const readElfImage = (bytes: Buffer): BinaryContainer => {
   }
   return {
     format: "elf",
-    elf: { machine: directory.machine, dynamicSegments },
+    elf: {
+      machine: directory.machine,
+      type: directory.elf_type,
+      dynamicSegments,
+    },
     architecture: architectureForElfMachine(directory.machine),
     bits,
     byte_order: reader.little ? "little" : "big",

src/native/metadata/NativeSectionDirectory.ts

@@ -52,6 +52,11 @@ export interface NativeSectionDirectory {
   readonly programs: readonly ElfProgramDeclaration[];
   readonly sections: readonly NativeSection[];
 }
+type ElfSectionDirectory = NativeSectionDirectory & {
+  readonly format: "elf";
+  readonly elf_type: number;
+};
+
 const STRUCTURE_BYTES = 16 * 1024 * 1024;
 const reject = (message: string): never => {
   throw new BinaryFormatFailure("malformed", message);
@@ -85,7 +90,7 @@ const request = (
 /** One ELF interpretation for in-memory images and bounded descriptor-backed inspections. */
 export function* readElfSectionDirectory(
   fileSize: number,
-): Generator<NativeReadRequest, NativeSectionDirectory, Buffer> {
+): Generator<NativeReadRequest, ElfSectionDirectory, Buffer> {
   const prefix = yield request(fileSize, 0n, 16n);
   const headerSize = prefix[4] === 1 ? 52 : 64;
   const bytes = yield request(fileSize, 0n, BigInt(headerSize));
@@ -95,7 +100,6 @@ export function* readElfSectionDirectory(
   const { elfClass: bits, byteOrder, machine } = header;
   const little = byteOrder === "little";
   const wide = bits === 64;
-  const r = new BinaryReader(bytes, little);
   const {
     offset: program_offset,
     width: program_width,
@@ -247,10 +251,11 @@ export function* readElfSectionDirectory(
   return {
     format: "elf",
     elf_os_abi: header.osAbi,
+    elf_type: header.type,
     bits,
     little,
     machine,
-    flags: r.u32(wide ? 48 : 36),
+    flags: header.flags,
     ...(section_names_limitation === undefined
       ? {}
       : { section_names_limitation }),
@@ -348,7 +353,7 @@ export function* readPeSectionDirectory(
 /** Borrow ELF bytes; file drivers satisfy the identical requests without loading payloads. */
 export const readElfDirectoryFromBuffer = (
   bytes: Buffer,
-): NativeSectionDirectory => {
+): ElfSectionDirectory => {
   const steps = readElfSectionDirectory(bytes.length);
   let next = steps.next();
   while (!next.done) {