#!/usr/bin/env python3 # SPDX-License-Identifier: GPL-2.0 # # Copyright (c) 2025 Intel Corporation # # Test for indirect target selection (ITS) mitigation. # # Test if indirect CALL/JMP are correctly patched by evaluating # the vmlinux .retpoline_sites in /proc/kcore. # Install dependencies # add-apt-repository ppa:michel-slm/kernel-utils # apt update # apt install -y python3-drgn python3-pyelftools python3-capstone # # Best to copy the vmlinux at a standard location: # mkdir -p /usr/lib/debug/lib/modules/$(uname -r) # cp $VMLINUX /usr/lib/debug/lib/modules/$(uname -r)/vmlinux # # Usage: ./its_indirect_alignment.py [vmlinux] import os, sys, argparse from pathlib import Path this_dir = os.path.dirname(os.path.realpath(__file__)) sys.path.insert(0, this_dir + '/../../kselftest') import ksft import common as c bug = "indirect_target_selection" mitigation = c.get_sysfs(bug) if not mitigation or "Aligned branch/return thunks" not in mitigation: ksft.test_result_skip("Skipping its_indirect_alignment.py: Aligned branch/return thunks not enabled") ksft.finished() if c.sysfs_has("spectre_v2", "Retpolines"): ksft.test_result_skip("Skipping its_indirect_alignment.py: Retpolines deployed") ksft.finished() c.check_dependencies_or_skip(['drgn', 'elftools', 'capstone'], script_name="its_indirect_alignment.py") from elftools.elf.elffile import ELFFile from drgn.helpers.common.memory import identify_address cap = c.init_capstone() if len(os.sys.argv) > 1: arg_vmlinux = os.sys.argv[1] if not os.path.exists(arg_vmlinux): ksft.test_result_fail(f"its_indirect_alignment.py: vmlinux not found at argument path: {arg_vmlinux}") ksft.exit_fail() os.makedirs(f"/usr/lib/debug/lib/modules/{os.uname().release}", exist_ok=True) os.system(f'cp {arg_vmlinux} /usr/lib/debug/lib/modules/$(uname -r)/vmlinux') vmlinux = f"/usr/lib/debug/lib/modules/{os.uname().release}/vmlinux" if not os.path.exists(vmlinux): ksft.test_result_fail(f"its_indirect_alignment.py: vmlinux not found at {vmlinux}") ksft.exit_fail() ksft.print_msg(f"Using vmlinux: {vmlinux}") retpolines_start_vmlinux, retpolines_sec_offset, size = c.get_section_info(vmlinux, '.retpoline_sites') ksft.print_msg(f"vmlinux: Section .retpoline_sites (0x{retpolines_start_vmlinux:x}) found at 0x{retpolines_sec_offset:x} with size 0x{size:x}") sites_offset = c.get_patch_sites(vmlinux, retpolines_sec_offset, size) total_retpoline_tests = len(sites_offset) ksft.print_msg(f"Found {total_retpoline_tests} retpoline sites") prog = c.get_runtime_kernel() retpolines_start_kcore = prog.symbol('__retpoline_sites').address ksft.print_msg(f'kcore: __retpoline_sites: 0x{retpolines_start_kcore:x}') x86_indirect_its_thunk_r15 = prog.symbol('__x86_indirect_its_thunk_r15').address ksft.print_msg(f'kcore: __x86_indirect_its_thunk_r15: 0x{x86_indirect_its_thunk_r15:x}') tests_passed = 0 tests_failed = 0 tests_unknown = 0 with open(vmlinux, 'rb') as f: elffile = ELFFile(f) text_section = elffile.get_section_by_name('.text') for i in range(0, len(sites_offset)): site = retpolines_start_kcore + sites_offset[i] vmlinux_site = retpolines_start_vmlinux + sites_offset[i] passed = unknown = failed = False try: vmlinux_insn = c.get_instruction_from_vmlinux(elffile, text_section, text_section['sh_addr'], vmlinux_site) kcore_insn = list(cap.disasm(prog.read(site, 16), site))[0] operand = kcore_insn.op_str insn_end = site + kcore_insn.size - 1 # TODO handle Jcc.32 __x86_indirect_thunk_\reg safe_site = insn_end & 0x20 site_status = "" if safe_site else "(unsafe)" ksft.print_msg(f"\nSite {i}: {identify_address(prog, site)} <0x{site:x}> {site_status}") ksft.print_msg(f"\tvmlinux: 0x{vmlinux_insn.address:x}:\t{vmlinux_insn.mnemonic}\t{vmlinux_insn.op_str}") ksft.print_msg(f"\tkcore: 0x{kcore_insn.address:x}:\t{kcore_insn.mnemonic}\t{kcore_insn.op_str}") if (site & 0x20) ^ (insn_end & 0x20): ksft.print_msg(f"\tSite at safe/unsafe boundary: {str(kcore_insn.bytes)} {kcore_insn.mnemonic} {operand}") if safe_site: tests_passed += 1 passed = True ksft.print_msg(f"\tPASSED: At safe address") continue if operand.startswith('0xffffffff'): thunk = int(operand, 16) if thunk > x86_indirect_its_thunk_r15: insn_at_thunk = list(cap.disasm(prog.read(thunk, 16), thunk))[0] operand += ' -> ' + insn_at_thunk.mnemonic + ' ' + insn_at_thunk.op_str + ' ' if 'jmp' in insn_at_thunk.mnemonic and thunk & 0x20: ksft.print_msg(f"\tPASSED: Found {operand} at safe address") passed = True if not passed: if kcore_insn.operands[0].type == capstone.CS_OP_IMM: operand += ' <' + prog.symbol(int(operand, 16)) + '>' if '__x86_indirect_its_thunk_' in operand: ksft.print_msg(f"\tPASSED: Found {operand}") else: ksft.print_msg(f"\tPASSED: Found direct branch: {kcore_insn}, ITS thunk not required.") passed = True else: unknown = True if passed: tests_passed += 1 elif unknown: ksft.print_msg(f"UNKNOWN: unexpected operand: {kcore_insn}") tests_unknown += 1 else: ksft.print_msg(f'\t************* FAILED *************') ksft.print_msg(f"\tFound {kcore_insn.bytes} {kcore_insn.mnemonic} {operand}") ksft.print_msg(f'\t**********************************') tests_failed += 1 except Exception as e: ksft.print_msg(f"UNKNOWN: An unexpected error occurred: {e}") tests_unknown += 1 ksft.print_msg(f"\n\nSummary:") ksft.print_msg(f"PASS: \t{tests_passed} \t/ {total_retpoline_tests}") ksft.print_msg(f"FAIL: \t{tests_failed} \t/ {total_retpoline_tests}") ksft.print_msg(f"UNKNOWN: \t{tests_unknown} \t/ {total_retpoline_tests}") if tests_failed == 0: ksft.test_result_pass("All ITS return thunk sites passed") else: ksft.test_result_fail(f"{tests_failed} ITS return thunk sites failed") ksft.finished()