perf(native): query retained export table facts (#6907)

* perf(native): query retained export table facts

* docs(perf): record native export task comparisons

* fix(native): preserve omitted export projection fields

* docs(perf): refresh final export view qualification

* test(native): verify sparse export view digests

experiments/analysis-efficiency/native-export-oracle.py

@@ -0,0 +1,48 @@
+"""Independent readelf symbol facts and directly mapped ELF64 version indices."""
+import hashlib
+import json
+from pathlib import Path
+import re
+import struct
+import subprocess
+import sys
+
+path = Path(sys.argv[1]).resolve()
+selected_names = sys.argv[2:]
+source = path.read_bytes()
+assert source[:6] == b'\x7fELF\x02\x01', 'This experiment oracle only covers ELF64 little-endian'
+section_offset = struct.unpack_from('<Q', source, 40)[0]
+section_width, section_count = struct.unpack_from('<HH', source, 58)
+assert section_width == 64 and section_count > 0
+sections = [struct.unpack_from('<IIQQQQIIQQ', source, section_offset + i * section_width) for i in range(section_count)]
+dynsym_index = next(i for i, row in enumerate(sections) if row[1] == 11)
+version_section = next(row for row in sections if row[1] == 0x6fffffff and row[6] == dynsym_index)
+text = subprocess.check_output(['readelf', '--dyn-syms', '--wide', str(path)], text=True)
+pattern = re.compile(r'^\s*(\d+):\s+([0-9a-f]+)\s+(\d+)\s+(\w+)\s+(\w+)\s+(\w+)\s+(\S+)\s+(\S+)')
+rows = []
+for line in text.splitlines():
+    match = pattern.match(line)
+    if not match:
+        continue
+    ordinal, value, size, kind, binding, visibility, section, display = match.groups()
+    ordinal = int(ordinal)
+    if binding not in ['GLOBAL', 'WEAK', 'UNIQUE'] or section == 'UND' or visibility not in ['DEFAULT', 'PROTECTED']:
+        continue
+    version_word = struct.unpack_from('<H', source, version_section[4] + ordinal * 2)[0]
+    if (version_word & 0x7fff) == 0:
+        continue
+    name, _, version_name = display.partition('@@' if '@@' in display else '@')
+    version = None if (version_word & 0x7fff) < 2 else {
+        'index': version_word & 0x7fff, 'name': version_name or None,
+        'name_bytes_base64': None, 'name_utf8_decodable': True if version_name else None,
+        'hidden': bool(version_word & 0x8000),
+    }
+    rows.append({'source_index': len(rows), 'name': name, 'name_bytes_base64': None, 'name_utf8_decodable': True,
+                 'value': hex(int(value, 16)), 'size': size, 'binding': binding.lower(),
+                 'type': {'FUNC': 'function', 'IFUNC': 'ifunc', 'OBJECT': 'object', 'TLS': 'tls'}.get(kind, 'other'),
+                 'version': version})
+selected = [row for row in rows if row['name'] in selected_names]
+assert set(row['name'] for row in selected) == set(selected_names)
+print(json.dumps({'artifact': {'path': str(path), 'sha256': hashlib.sha256(source).hexdigest(), 'bytes': len(source)},
+                  'oracle': subprocess.check_output(['readelf', '--version'], text=True).splitlines()[0],
+                  'names': selected_names, 'export_count': len(rows), 'rows': selected}, indent=2))