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#!/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 + ' <dynamic-thunk?>'
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()
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