| //===-- AArch64PointerAuth.h -- Harden code using PAuth ---------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_LIB_TARGET_AARCH64_AARCH64POINTERAUTH_H |
| #define LLVM_LIB_TARGET_AARCH64_AARCH64POINTERAUTH_H |
| |
| #include "llvm/CodeGen/MachineBasicBlock.h" |
| #include "llvm/CodeGen/Register.h" |
| |
| namespace llvm { |
| namespace AArch64PAuth { |
| |
| /// Variants of check performed on an authenticated pointer. |
| /// |
| /// In cases such as authenticating the LR value when performing a tail call |
| /// or when re-signing a signed pointer with a different signing schema, |
| /// a failed authentication may not generate an exception on its own and may |
| /// create an authentication or signing oracle if not checked explicitly. |
| /// |
| /// A number of check methods modify control flow in a similar way by |
| /// rewriting the code |
| /// |
| /// ``` |
| /// <authenticate LR> |
| /// <more instructions> |
| /// ``` |
| /// |
| /// as follows: |
| /// |
| /// ``` |
| /// <authenticate LR> |
| /// <method-specific checker> |
| /// ret_block: |
| /// <more instructions> |
| /// ... |
| /// |
| /// break_block: |
| /// brk <code> |
| /// ``` |
| enum class AuthCheckMethod { |
| /// Do not check the value at all |
| None, |
| /// Perform a load to a temporary register |
| DummyLoad, |
| /// Check by comparing bits 62 and 61 of the authenticated address. |
| /// |
| /// This method modifies control flow and inserts the following checker: |
| /// |
| /// ``` |
| /// eor Xtmp, Xn, Xn, lsl #1 |
| /// tbnz Xtmp, #62, break_block |
| /// ``` |
| HighBitsNoTBI, |
| /// Check by comparing the authenticated value with an XPAC-ed one without |
| /// using PAuth instructions not encoded as HINT. Can only be applied to LR. |
| /// |
| /// This method modifies control flow and inserts the following checker: |
| /// |
| /// ``` |
| /// mov Xtmp, LR |
| /// xpaclri ; encoded as "hint #7" |
| /// ; Note: at this point, the LR register contains the address as if |
| /// ; the authentication succeeded and the temporary register contains the |
| /// ; *real* result of authentication. |
| /// cmp Xtmp, LR |
| /// b.ne break_block |
| /// ``` |
| XPACHint, |
| }; |
| |
| #define AUTH_CHECK_METHOD_CL_VALUES_COMMON \ |
| clEnumValN(AArch64PAuth::AuthCheckMethod::None, "none", \ |
| "Do not check authenticated address"), \ |
| clEnumValN(AArch64PAuth::AuthCheckMethod::DummyLoad, "load", \ |
| "Perform dummy load from authenticated address"), \ |
| clEnumValN(AArch64PAuth::AuthCheckMethod::HighBitsNoTBI, \ |
| "high-bits-notbi", \ |
| "Compare bits 62 and 61 of address (TBI should be disabled)") |
| |
| #define AUTH_CHECK_METHOD_CL_VALUES_LR \ |
| AUTH_CHECK_METHOD_CL_VALUES_COMMON, \ |
| clEnumValN(AArch64PAuth::AuthCheckMethod::XPACHint, "xpac-hint", \ |
| "Compare with the result of XPACLRI") |
| |
| /// Explicitly checks that pointer authentication succeeded. |
| /// |
| /// Assuming AuthenticatedReg contains a value returned by one of the AUT* |
| /// instructions, check the value using Method just before the instruction |
| /// pointed to by MBBI. If the check succeeds, execution proceeds to the |
| /// instruction pointed to by MBBI, otherwise a CPU exception is generated. |
| /// |
| /// Some of the methods may need to know if the pointer was authenticated |
| /// using an I-key or D-key and which register can be used as temporary. |
| /// If an explicit BRK instruction is used to generate an exception, BrkImm |
| /// specifies its immediate operand. |
| /// |
| /// \returns The machine basic block containing the code that is executed |
| /// after the check succeeds. |
| MachineBasicBlock &checkAuthenticatedRegister(MachineBasicBlock::iterator MBBI, |
| AuthCheckMethod Method, |
| Register AuthenticatedReg, |
| Register TmpReg, bool UseIKey, |
| unsigned BrkImm); |
| |
| /// Returns the number of bytes added by checkAuthenticatedRegister. |
| unsigned getCheckerSizeInBytes(AuthCheckMethod Method); |
| |
| } // end namespace AArch64PAuth |
| } // end namespace llvm |
| |
| #endif |