scripts: add JS-only script for large cores on Mac

indutny · indutny · commit 1a27c7246106 · 2017-03-01T11:24:58.000-05:00
Fix: #68 PR-URL: #69 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Howard Hellyer <hhellyer@uk.ibm.com>
diff --git a/scripts/macho2segments.js b/scripts/macho2segments.js
@@ -0,0 +1,78 @@
+#!/usr/bin/env node
+'use strict';
+
+const assert = require('assert');
+const fs = require('fs');
+const Buffer = require('buffer').Buffer;
+
+const ALIGN_64 = 8;
+
+const HEADER_SIZE = 4 * 7;
+const BODY_OFF_64 = 4 * 8;
+const MAGIC_LE_32 = 0xfeedface;
+const MAGIC_LE_64 = 0xfeedfacf;
+
+const CMD_HEADER_SIZE = 8;
+const LC_SEGMENT_64 = 0x19;
+const LC_SEGMENT_64_SIZE = 4 * 2 + 16 + 8 * 4 + 4 * 4;
+const VM_PROT_WRITE = 0x2;
+
+if (process.argv.length < 3) {
+  console.error('Usage: %s <core_file>', process.argv[1]);
+  process.exit(1);
+  return;
+}
+
+const fd = fs.openSync(process.argv[2], 'r');
+
+function read(start, end) {
+  const data = Buffer.alloc(end - start);
+  const bytesRead = fs.readSync(fd, data, 0, data.length, start);
+
+  assert.strictEqual(data.length, bytesRead, 'Read less than expected');
+
+  return data;
+}
+
+function pad8(s) {
+  let r = s;
+  while (r.length < 8)
+    r = '0' + r;
+  return r;
+}
+
+function parseUInt64LE(buf, off) {
+  const low = pad8(buf.readUInt32LE(off).toString(16));
+  const high = pad8(buf.readUInt32LE(off + 4).toString(16));
+  return '0x' + high + low;
+}
+
+/* header = { magic, cpu, cpu_sub, filetype, ncmds, sizeofcmds, flags } */
+const header = read(0, HEADER_SIZE);
+assert.strictEqual(header.readUInt32LE(0), MAGIC_LE_64, 'Invalid magic value');
+
+const ncmds = header.readUInt32LE(4 * 4);
+const sizeofcmds = header.readUInt32LE(4 * 5);
+
+for (let off = BODY_OFF_64, i = 0; i < ncmds; i++) {
+  /* cmd = { type, size } */
+  const cmd = read(off, off + CMD_HEADER_SIZE);
+
+  const type = cmd.readUInt32LE(0);
+  const size = cmd.readUInt32LE(4);
+  off += size;
+
+  if (type !== LC_SEGMENT_64)
+    continue;
+
+  assert.strictEqual(size, LC_SEGMENT_64_SIZE, 'Invalid LC_SEGMENT_64 size');
+
+  const body = read(off - size + 4 * 2, off);
+  const vmaddr = parseUInt64LE(body, 16);
+  const vmsize = parseUInt64LE(body, 24);
+  const prot = body.readUInt32LE(48) | body.readUInt32LE(52);
+  if (!(prot & VM_PROT_WRITE))
+    continue;
+
+  console.log(vmaddr + ' ' + vmsize);
+}
