selftest/x86/bugs: Add selftests for ITS

Below are the tests added for Indirect Target Selection (ITS):

- its_sysfs.py - Check if sysfs reflects the correct mitigation status for
  the mitigation selected via the kernel cmdline.

- its_permutations.py - tests mitigation selection with cmdline
  permutations with other bugs like spectre_v2 and retbleed.

- its_indirect_alignment.py - verifies that for addresses in
  .retpoline_sites section that belong to lower half of cacheline are
  patched to ITS-safe thunk. Typical output looks like below:

  Site 49: function symbol: __x64_sys_restart_syscall+0x1f <0xffffffffbb1509af>
  #     vmlinux: 0xffffffff813509af:    jmp     0xffffffff81f5a8e0
  #     kcore:   0xffffffffbb1509af:    jmpq    *%rax
  #     ITS thunk NOT expected for site 49
  #     PASSED: Found *%rax
  #
  Site 50: function symbol: __resched_curr+0xb0 <0xffffffffbb181910>
  #     vmlinux: 0xffffffff81381910:    jmp     0xffffffff81f5a8e0
  #     kcore:   0xffffffffbb181910:    jmp     0xffffffffc02000fc
  #     ITS thunk expected for site 50
  #     PASSED: Found 0xffffffffc02000fc -> jmpq *%rax <scattered-thunk?>

- its_ret_alignment.py - verifies that for addresses in .return_sites
  section that belong to lower half of cacheline are patched to
  its_return_thunk. Typical output looks like below:

  Site 97: function symbol: collect_event+0x48 <0xffffffffbb007f18>
  #     vmlinux: 0xffffffff81207f18:    jmp     0xffffffff81f5b500
  #     kcore:   0xffffffffbb007f18:    jmp     0xffffffffbbd5b560
  #     PASSED: Found jmp 0xffffffffbbd5b560 <its_return_thunk>
  #
  Site 98: function symbol: collect_event+0xa4 <0xffffffffbb007f74>
  #     vmlinux: 0xffffffff81207f74:    jmp     0xffffffff81f5b500
  #     kcore:   0xffffffffbb007f74:    retq
  #     PASSED: Found retq

Some of these tests have dependency on tools like virtme-ng[1] and drgn[2].
When the dependencies are not met, the test will be skipped.

[1] https://github.com/arighi/virtme-ng
[2] https://github.com/osandov/drgn

Co-developed-by: Tao Zhang <tao1.zhang@linux.intel.com>
Signed-off-by: Tao Zhang <tao1.zhang@linux.intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/tools/testing/selftests/x86/bugs/its_sysfs.py b/tools/testing/selftests/x86/bugs/its_sysfs.py
new file mode 100755
index 000000000000..7bca81f2f606
--- /dev/null
+++ b/tools/testing/selftests/x86/bugs/its_sysfs.py
@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (c) 2025 Intel Corporation
+#
+# Test for Indirect Target Selection(ITS) mitigation sysfs status.
+
+import sys, os, re
+this_dir = os.path.dirname(os.path.realpath(__file__))
+sys.path.insert(0, this_dir + '/../../kselftest')
+import ksft
+
+from common import *
+
+bug = "indirect_target_selection"
+mitigation = get_sysfs(bug)
+
+ITS_MITIGATION_ALIGNED_THUNKS	= "Mitigation: Aligned branch/return thunks"
+ITS_MITIGATION_RETPOLINE_STUFF	= "Mitigation: Retpolines, Stuffing RSB"
+ITS_MITIGATION_VMEXIT_ONLY		= "Mitigation: Vulnerable, KVM: Not affected"
+ITS_MITIGATION_VULNERABLE       = "Vulnerable"
+
+def check_mitigation():
+    if mitigation == ITS_MITIGATION_ALIGNED_THUNKS:
+        if cmdline_has(f'{bug}=stuff') and sysfs_has("spectre_v2", "Retpolines"):
+            bug_check_fail(bug, ITS_MITIGATION_ALIGNED_THUNKS, ITS_MITIGATION_RETPOLINE_STUFF)
+            return
+        if cmdline_has(f'{bug}=vmexit') and cpuinfo_has('its_native_only'):
+            bug_check_fail(bug, ITS_MITIGATION_ALIGNED_THUNKS, ITS_MITIGATION_VMEXIT_ONLY)
+            return
+        bug_check_pass(bug, ITS_MITIGATION_ALIGNED_THUNKS)
+        return
+
+    if mitigation == ITS_MITIGATION_RETPOLINE_STUFF:
+        if cmdline_has(f'{bug}=stuff') and sysfs_has("spectre_v2", "Retpolines"):
+            bug_check_pass(bug, ITS_MITIGATION_RETPOLINE_STUFF)
+            return
+        if sysfs_has('retbleed', 'Stuffing'):
+            bug_check_pass(bug, ITS_MITIGATION_RETPOLINE_STUFF)
+            return
+        bug_check_fail(bug, ITS_MITIGATION_RETPOLINE_STUFF, ITS_MITIGATION_ALIGNED_THUNKS)
+
+    if mitigation == ITS_MITIGATION_VMEXIT_ONLY:
+        if cmdline_has(f'{bug}=vmexit') and cpuinfo_has('its_native_only'):
+            bug_check_pass(bug, ITS_MITIGATION_VMEXIT_ONLY)
+            return
+        bug_check_fail(bug, ITS_MITIGATION_VMEXIT_ONLY, ITS_MITIGATION_ALIGNED_THUNKS)
+
+    if mitigation == ITS_MITIGATION_VULNERABLE:
+        if sysfs_has("spectre_v2", "Vulnerable"):
+            bug_check_pass(bug, ITS_MITIGATION_VULNERABLE)
+        else:
+            bug_check_fail(bug, "Mitigation", ITS_MITIGATION_VULNERABLE)
+
+    bug_status_unknown(bug, mitigation)
+    return
+
+ksft.print_header()
+ksft.set_plan(1)
+ksft.print_msg(f'{bug}: {mitigation} ...')
+
+if not basic_checks_sufficient(bug, mitigation):
+    check_mitigation()
+
+ksft.finished()