44076c9822
Move the emission of the checks performed on the authenticated LR value during tail calls to AArch64AsmPrinter class, so that different checker sequences can be reused by pseudo instructions expanded there. This adds one more option to AuthCheckMethod enumeration, the generic XPAC variant which is not restricted to checking the LR register.
111 lines
3.7 KiB
C++
111 lines
3.7 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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/// on_fail:
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/// brk <code>
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/// on_success:
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/// <more instructions>
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///
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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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/// tbz Xtmp, #62, on_success
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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.eq on_success
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/// ```
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XPACHint,
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/// Similar to XPACHint but using Armv8.3-only XPAC instruction, thus
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/// not restricted to LR:
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/// ```
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/// mov Xtmp, Xn
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/// xpac(i|d) Xn
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/// cmp Xtmp, Xn
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/// b.eq on_success
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/// ```
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XPAC,
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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( \
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AArch64PAuth::AuthCheckMethod::HighBitsNoTBI, "high-bits-notbi", \
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"Compare bits 62 and 61 of address (TBI should be disabled)"), \
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clEnumValN(AArch64PAuth::AuthCheckMethod::XPAC, "xpac", \
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"Compare with the result of XPAC (requires Armv8.3-a)")
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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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/// 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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