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