1//===-- AArch64PointerAuth.h -- Harden code using PAuth ---------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef LLVM_LIB_TARGET_AARCH64_AARCH64POINTERAUTH_H
10#define LLVM_LIB_TARGET_AARCH64_AARCH64POINTERAUTH_H
11
12#include "Utils/AArch64BaseInfo.h"
13
14namespace llvm {
15namespace AArch64PAuth {
16
17/// PAuth key to be used with function pointers in .init_array and .fini_array.
18constexpr AArch64PACKey::ID InitFiniKey = AArch64PACKey::IA;
19
20/// Constant discriminator to be used with function pointers in .init_array and
21/// .fini_array. The value is ptrauth_string_discriminator("init_fini")
22constexpr unsigned InitFiniPointerConstantDiscriminator = 0xD9D4;
23
24/// Variants of check performed on an authenticated pointer.
25///
26/// In cases such as authenticating the LR value when performing a tail call
27/// or when re-signing a signed pointer with a different signing schema,
28/// a failed authentication may not generate an exception on its own and may
29/// create an authentication or signing oracle if not checked explicitly.
30///
31/// A number of check methods modify control flow in a similar way by
32/// rewriting the code
33///
34/// ```
35/// <authenticate LR>
36/// <more instructions>
37/// ```
38///
39/// as follows:
40///
41/// ```
42/// <authenticate LR>
43/// <method-specific checker>
44/// on_fail:
45/// brk <code>
46/// on_success:
47/// <more instructions>
48///
49/// ```
50enum class AuthCheckMethod {
51 /// Do not check the value at all
52 None,
53
54 /// Perform a load to a temporary register
55 DummyLoad,
56
57 /// Check by comparing bits 62 and 61 of the authenticated address.
58 ///
59 /// This method modifies control flow and inserts the following checker:
60 ///
61 /// ```
62 /// eor Xtmp, Xn, Xn, lsl #1
63 /// tbz Xtmp, #62, on_success
64 /// ```
65 HighBitsNoTBI,
66
67 /// Check by comparing the authenticated value with an XPAC-ed one without
68 /// using PAuth instructions not encoded as HINT. Can only be applied to LR.
69 ///
70 /// This method modifies control flow and inserts the following checker:
71 ///
72 /// ```
73 /// mov Xtmp, LR
74 /// xpaclri ; encoded as "hint #7"
75 /// ; Note: at this point, the LR register contains the address as if
76 /// ; the authentication succeeded and the temporary register contains the
77 /// ; *real* result of authentication.
78 /// cmp Xtmp, LR
79 /// b.eq on_success
80 /// ```
81 XPACHint,
82
83 /// Similar to XPACHint but using Armv8.3-only XPAC instruction, thus
84 /// not restricted to LR:
85 /// ```
86 /// mov Xtmp, Xn
87 /// xpac(i|d) Xn
88 /// cmp Xtmp, Xn
89 /// b.eq on_success
90 /// ```
91 XPAC,
92};
93
94#define AUTH_CHECK_METHOD_CL_VALUES_COMMON \
95 clEnumValN(AArch64PAuth::AuthCheckMethod::None, "none", \
96 "Do not check authenticated address"), \
97 clEnumValN(AArch64PAuth::AuthCheckMethod::DummyLoad, "load", \
98 "Perform dummy load from authenticated address"), \
99 clEnumValN( \
100 AArch64PAuth::AuthCheckMethod::HighBitsNoTBI, "high-bits-notbi", \
101 "Compare bits 62 and 61 of address (TBI should be disabled)"), \
102 clEnumValN(AArch64PAuth::AuthCheckMethod::XPAC, "xpac", \
103 "Compare with the result of XPAC (requires Armv8.3-a)")
104
105#define AUTH_CHECK_METHOD_CL_VALUES_LR \
106 AUTH_CHECK_METHOD_CL_VALUES_COMMON, \
107 clEnumValN(AArch64PAuth::AuthCheckMethod::XPACHint, "xpac-hint", \
108 "Compare with the result of XPACLRI")
109
110/// Returns the number of bytes added by checkAuthenticatedRegister.
111unsigned getCheckerSizeInBytes(AuthCheckMethod Method);
112
113} // end namespace AArch64PAuth
114} // end namespace llvm
115
116#endif
117