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102 lines
3.7 KiB
TypeScript
102 lines
3.7 KiB
TypeScript
import { readElfAttributeUleb } from "../domain/elfAttributeUleb.js";
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import type { MipsGnuAttributes } from "../domain/binaryTargetTypes.js";
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import { err, ok, type Result } from "../domain/result.js";
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/** Bound the section read before its declared size can drive allocation. */
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export const MIPS_GNU_ATTRIBUTES_MAX_BYTES = 4096;
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const FORMAT_VERSION = 0x41;
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const TAG_FILE = 1;
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const TAG_GNU_MIPS_ABI_FP = 4;
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const TAG_GNU_MIPS_ABI_MSA = 8;
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/**
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* Read only GNU file-scope MIPS ABI attributes REA understands. Unknown
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* vendors, scopes and tags fail closed; their declarations are not skipped.
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*/
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export const parseMipsGnuAttributes = (
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bytes: Buffer,
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littleEndian: boolean,
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): Result<MipsGnuAttributes, string> => {
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if (bytes.length === 0 || bytes[0] !== FORMAT_VERSION)
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return err("unsupported MIPS GNU attribute section format version");
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const readU32 = (offset: number): number =>
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littleEndian ? bytes.readUInt32LE(offset) : bytes.readUInt32BE(offset);
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let fpAbi: number | null = null;
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let msa: number | null = null;
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let vendorSeen = false;
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let position = 1;
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while (position < bytes.length) {
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if (bytes.length - position < 4)
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return err("truncated MIPS GNU attribute subsection length");
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const length = readU32(position);
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if (length < 4 || length > bytes.length - position)
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return err(
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"MIPS GNU attribute subsection length does not fit the section",
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);
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const end = position + length;
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const vendorEnd = bytes.indexOf(0, position + 4);
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if (vendorEnd < 0 || vendorEnd >= end)
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return err("unterminated MIPS GNU attribute vendor name");
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if (bytes.toString("latin1", position + 4, vendorEnd) !== "gnu")
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return err(
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"MIPS ELF declares non-GNU vendor attributes that REA does not inspect",
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);
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if (vendorSeen)
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return err("duplicate MIPS GNU attribute vendor subsections");
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vendorSeen = true;
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let cursor = vendorEnd + 1;
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while (cursor < end) {
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const scopeStart = cursor;
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const scope = readElfAttributeUleb(bytes, cursor, end);
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if (scope === undefined)
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return err("malformed MIPS GNU attribute scope tag");
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if (scope.value !== TAG_FILE)
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return err(
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"MIPS GNU attributes scoped to sections or symbols are not inspected by REA",
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);
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if (end - scope.next < 4)
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return err("truncated MIPS GNU attribute scope length");
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const scopeLength = readU32(scope.next);
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if (
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scopeLength < scope.next + 4 - scopeStart ||
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scopeLength > end - scopeStart
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)
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return err(
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"MIPS GNU attribute scope length does not fit its subsection",
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);
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const scopeEnd = scopeStart + scopeLength;
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cursor = scope.next + 4;
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while (cursor < scopeEnd) {
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const tag = readElfAttributeUleb(bytes, cursor, scopeEnd);
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if (tag === undefined) return err("malformed MIPS GNU attribute tag");
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if (
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tag.value !== TAG_GNU_MIPS_ABI_FP &&
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tag.value !== TAG_GNU_MIPS_ABI_MSA
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)
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return err(
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`MIPS ELF declares GNU attribute tag ${tag.value}, which REA does not inspect`,
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);
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const value = readElfAttributeUleb(bytes, tag.next, scopeEnd);
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if (value === undefined)
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return err("malformed MIPS GNU attribute value");
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if (tag.value === TAG_GNU_MIPS_ABI_FP) {
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if (fpAbi !== null)
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return err("duplicate MIPS GNU floating-point ABI attributes");
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fpAbi = value.value;
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} else {
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if (msa !== null) return err("duplicate MIPS GNU MSA ABI attributes");
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msa = value.value;
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}
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cursor = value.next;
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}
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cursor = scopeEnd;
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}
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position = end;
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}
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return ok({ fpAbi, msa });
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};
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