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19e277dd19
This change adds optional support for - Armv8.3-A Pointer Authentication (PAuth) and - Armv8.5-A Branch Target Identification (BTI) features to the perl scripts. Both features can be enabled with additional compiler flags. Unless any of these are enabled explicitly there is no code change at all. The extensions are briefly described below. Please read the appropriate chapters of the Arm Architecture Reference Manual for the complete specification. Scope ----- This change only affects generated assembly code. Armv8.3-A Pointer Authentication -------------------------------- Pointer Authentication extension supports the authentication of the contents of registers before they are used for indirect branching or load. PAuth provides a probabilistic method to detect corruption of register values. PAuth signing instructions generate a Pointer Authentication Code (PAC) based on the value of a register, a seed and a key. The generated PAC is inserted into the original value in the register. A PAuth authentication instruction recomputes the PAC, and if it matches the PAC in the register, restores its original value. In case of a mismatch, an architecturally unmapped address is generated instead. With PAuth, mitigation against ROP (Return-oriented Programming) attacks can be implemented. This is achieved by signing the contents of the link-register (LR) before it is pushed to stack. Once LR is popped, it is authenticated. This way a stack corruption which overwrites the LR on the stack is detectable. The PAuth extension adds several new instructions, some of which are not recognized by older hardware. To support a single codebase for both pre Armv8.3-A targets and newer ones, only NOP-space instructions are added by this patch. These instructions are treated as NOPs on hardware which does not support Armv8.3-A. Furthermore, this patch only considers cases where LR is saved to the stack and then restored before branching to its content. There are cases in the code where LR is pushed to stack but it is not used later. We do not address these cases as they are not affected by PAuth. There are two keys available to sign an instruction address: A and B. PACIASP and PACIBSP only differ in the used keys: A and B, respectively. The keys are typically managed by the operating system. To enable generating code for PAuth compile with -mbranch-protection=<mode>: - standard or pac-ret: add PACIASP and AUTIASP, also enables BTI (read below) - pac-ret+b-key: add PACIBSP and AUTIBSP Armv8.5-A Branch Target Identification -------------------------------------- Branch Target Identification features some new instructions which protect the execution of instructions on guarded pages which are not intended branch targets. If Armv8.5-A is supported by the hardware, execution of an instruction changes the value of PSTATE.BTYPE field. If an indirect branch lands on a guarded page the target instruction must be one of the BTI <jc> flavors, or in case of a direct call or jump it can be any other instruction. If the target instruction is not compatible with the value of PSTATE.BTYPE a Branch Target Exception is generated. In short, indirect jumps are compatible with BTI <j> and <jc> while indirect calls are compatible with BTI <c> and <jc>. Please refer to the specification for the details. Armv8.3-A PACIASP and PACIBSP are implicit branch target identification instructions which are equivalent with BTI c or BTI jc depending on system register configuration. BTI is used to mitigate JOP (Jump-oriented Programming) attacks by limiting the set of instructions which can be jumped to. BTI requires active linker support to mark the pages with BTI-enabled code as guarded. For ELF64 files BTI compatibility is recorded in the .note.gnu.property section. For a shared object or static binary it is required that all linked units support BTI. This means that even a single assembly file without the required note section turns-off BTI for the whole binary or shared object. The new BTI instructions are treated as NOPs on hardware which does not support Armv8.5-A or on pages which are not guarded. To insert this new and optional instruction compile with -mbranch-protection=standard (also enables PAuth) or +bti. When targeting a guarded page from a non-guarded page, weaker compatibility restrictions apply to maintain compatibility between legacy and new code. For detailed rules please refer to the Arm ARM. Compiler support ---------------- Compiler support requires understanding '-mbranch-protection=<mode>' and emitting the appropriate feature macros (__ARM_FEATURE_BTI_DEFAULT and __ARM_FEATURE_PAC_DEFAULT). The current state is the following: ------------------------------------------------------- | Compiler | -mbranch-protection | Feature macros | +----------+---------------------+--------------------+ | clang | 9.0.0 | 11.0.0 | +----------+---------------------+--------------------+ | gcc | 9 | expected in 10.1+ | ------------------------------------------------------- Available Platforms ------------------ Arm Fast Model and QEMU support both extensions. https://developer.arm.com/tools-and-software/simulation-models/fast-models https://www.qemu.org/ Implementation Notes -------------------- This change adds BTI landing pads even to assembly functions which are likely to be directly called only. In these cases, landing pads might be superfluous depending on what code the linker generates. Code size and performance impact for these cases would be negligible. Interaction with C code ----------------------- Pointer Authentication is a per-frame protection while Branch Target Identification can be turned on and off only for all code pages of a whole shared object or static binary. Because of these properties if C/C++ code is compiled without any of the above features but assembly files support any of them unconditionally there is no incompatibility between the two. Useful Links ------------ To fully understand the details of both PAuth and BTI it is advised to read the related chapters of the Arm Architecture Reference Manual (Arm ARM): https://developer.arm.com/documentation/ddi0487/latest/ Additional materials: "Providing protection for complex software" https://developer.arm.com/architectures/learn-the-architecture/providing-protection-for-complex-software Arm Compiler Reference Guide Version 6.14: -mbranch-protection https://developer.arm.com/documentation/101754/0614/armclang-Reference/armclang-Command-line-Options/-mbranch-protection?lang=en Arm C Language Extensions (ACLE) https://developer.arm.com/docs/101028/latest Addional Notes -------------- This patch is a copy of the work done by Tamas Petz in boringssl. It contains the changes from the following commits: aarch64: support BTI and pointer authentication in assembly Change-Id: I4335f92e2ccc8e209c7d68a0a79f1acdf3aeb791 URL: https://boringssl-review.googlesource.com/c/boringssl/+/42084 aarch64: Improve conditional compilation Change-Id: I14902a64e5f403c2b6a117bc9f5fb1a4f4611ebf URL: https://boringssl-review.googlesource.com/c/boringssl/+/43524 aarch64: Fix name of gnu property note section Change-Id: I6c432d1c852129e9c273f6469a8b60e3983671ec URL: https://boringssl-review.googlesource.com/c/boringssl/+/44024 Change-Id: I2d95ebc5e4aeb5610d3b226f9754ee80cf74a9af Reviewed-by: Paul Dale <pauli@openssl.org> Reviewed-by: Tomas Mraz <tomas@openssl.org> (Merged from https://github.com/openssl/openssl/pull/16674)
188 lines
6.3 KiB
C
188 lines
6.3 KiB
C
/*
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* Copyright 2011-2021 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the Apache License 2.0 (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#ifndef OSSL_CRYPTO_ARM_ARCH_H
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# define OSSL_CRYPTO_ARM_ARCH_H
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# if !defined(__ARM_ARCH__)
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# if defined(__CC_ARM)
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# define __ARM_ARCH__ __TARGET_ARCH_ARM
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# if defined(__BIG_ENDIAN)
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# define __ARMEB__
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# else
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# define __ARMEL__
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# endif
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# elif defined(__GNUC__)
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# if defined(__aarch64__)
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# define __ARM_ARCH__ 8
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# if __BYTE_ORDER__==__ORDER_BIG_ENDIAN__
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# define __ARMEB__
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# else
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# define __ARMEL__
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# endif
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/*
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* Why doesn't gcc define __ARM_ARCH__? Instead it defines
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* bunch of below macros. See all_architectures[] table in
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* gcc/config/arm/arm.c. On a side note it defines
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* __ARMEL__/__ARMEB__ for little-/big-endian.
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*/
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# elif defined(__ARM_ARCH)
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# define __ARM_ARCH__ __ARM_ARCH
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# elif defined(__ARM_ARCH_8A__)
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# define __ARM_ARCH__ 8
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# elif defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) || \
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defined(__ARM_ARCH_7R__)|| defined(__ARM_ARCH_7M__) || \
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defined(__ARM_ARCH_7EM__)
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# define __ARM_ARCH__ 7
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# elif defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || \
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defined(__ARM_ARCH_6K__)|| defined(__ARM_ARCH_6M__) || \
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defined(__ARM_ARCH_6Z__)|| defined(__ARM_ARCH_6ZK__) || \
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defined(__ARM_ARCH_6T2__)
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# define __ARM_ARCH__ 6
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# elif defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5T__) || \
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defined(__ARM_ARCH_5E__)|| defined(__ARM_ARCH_5TE__) || \
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defined(__ARM_ARCH_5TEJ__)
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# define __ARM_ARCH__ 5
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# elif defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__)
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# define __ARM_ARCH__ 4
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# else
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# error "unsupported ARM architecture"
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# endif
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# endif
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# endif
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# if !defined(__ARM_MAX_ARCH__)
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# define __ARM_MAX_ARCH__ __ARM_ARCH__
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# endif
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# if __ARM_MAX_ARCH__<__ARM_ARCH__
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# error "__ARM_MAX_ARCH__ can't be less than __ARM_ARCH__"
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# elif __ARM_MAX_ARCH__!=__ARM_ARCH__
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# if __ARM_ARCH__<7 && __ARM_MAX_ARCH__>=7 && defined(__ARMEB__)
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# error "can't build universal big-endian binary"
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# endif
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# endif
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# ifndef __ASSEMBLER__
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extern unsigned int OPENSSL_armcap_P;
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extern unsigned int OPENSSL_arm_midr;
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extern unsigned int OPENSSL_armv8_rsa_neonized;
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# endif
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# define ARMV7_NEON (1<<0)
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# define ARMV7_TICK (1<<1)
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# define ARMV8_AES (1<<2)
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# define ARMV8_SHA1 (1<<3)
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# define ARMV8_SHA256 (1<<4)
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# define ARMV8_PMULL (1<<5)
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# define ARMV8_SHA512 (1<<6)
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# define ARMV8_CPUID (1<<7)
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/*
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* MIDR_EL1 system register
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*
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* 63___ _ ___32_31___ _ ___24_23_____20_19_____16_15__ _ __4_3_______0
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* | | | | | | |
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* |RES0 | Implementer | Variant | Arch | PartNum |Revision|
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* |____ _ _____|_____ _ _____|_________|_______ _|____ _ ___|________|
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*
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*/
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# define ARM_CPU_IMP_ARM 0x41
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# define ARM_CPU_PART_CORTEX_A72 0xD08
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# define ARM_CPU_PART_N1 0xD0C
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# define MIDR_PARTNUM_SHIFT 4
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# define MIDR_PARTNUM_MASK (0xfff << MIDR_PARTNUM_SHIFT)
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# define MIDR_PARTNUM(midr) \
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(((midr) & MIDR_PARTNUM_MASK) >> MIDR_PARTNUM_SHIFT)
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# define MIDR_IMPLEMENTER_SHIFT 24
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# define MIDR_IMPLEMENTER_MASK (0xff << MIDR_IMPLEMENTER_SHIFT)
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# define MIDR_IMPLEMENTER(midr) \
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(((midr) & MIDR_IMPLEMENTER_MASK) >> MIDR_IMPLEMENTER_SHIFT)
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# define MIDR_ARCHITECTURE_SHIFT 16
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# define MIDR_ARCHITECTURE_MASK (0xf << MIDR_ARCHITECTURE_SHIFT)
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# define MIDR_ARCHITECTURE(midr) \
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(((midr) & MIDR_ARCHITECTURE_MASK) >> MIDR_ARCHITECTURE_SHIFT)
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# define MIDR_CPU_MODEL_MASK \
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(MIDR_IMPLEMENTER_MASK | \
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MIDR_PARTNUM_MASK | \
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MIDR_ARCHITECTURE_MASK)
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# define MIDR_CPU_MODEL(imp, partnum) \
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(((imp) << MIDR_IMPLEMENTER_SHIFT) | \
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(0xf << MIDR_ARCHITECTURE_SHIFT) | \
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((partnum) << MIDR_PARTNUM_SHIFT))
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# define MIDR_IS_CPU_MODEL(midr, imp, partnum) \
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(((midr) & MIDR_CPU_MODEL_MASK) == MIDR_CPU_MODEL(imp, partnum))
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#if defined(__ASSEMBLER__)
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/*
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* Support macros for
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* - Armv8.3-A Pointer Authentication and
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* - Armv8.5-A Branch Target Identification
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* features which require emitting a .note.gnu.property section with the
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* appropriate architecture-dependent feature bits set.
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* Read more: "ELF for the Arm® 64-bit Architecture"
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*/
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# if defined(__ARM_FEATURE_BTI_DEFAULT) && __ARM_FEATURE_BTI_DEFAULT == 1
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# define GNU_PROPERTY_AARCH64_BTI (1 << 0) /* Has Branch Target Identification */
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# define AARCH64_VALID_CALL_TARGET hint #34 /* BTI 'c' */
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# else
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# define GNU_PROPERTY_AARCH64_BTI 0 /* No Branch Target Identification */
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# define AARCH64_VALID_CALL_TARGET
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# endif
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# if defined(__ARM_FEATURE_PAC_DEFAULT) && \
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(__ARM_FEATURE_PAC_DEFAULT & 1) == 1 /* Signed with A-key */
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# define GNU_PROPERTY_AARCH64_POINTER_AUTH \
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(1 << 1) /* Has Pointer Authentication */
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# define AARCH64_SIGN_LINK_REGISTER hint #25 /* PACIASP */
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# define AARCH64_VALIDATE_LINK_REGISTER hint #29 /* AUTIASP */
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# elif defined(__ARM_FEATURE_PAC_DEFAULT) && \
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(__ARM_FEATURE_PAC_DEFAULT & 2) == 2 /* Signed with B-key */
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# define GNU_PROPERTY_AARCH64_POINTER_AUTH \
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(1 << 1) /* Has Pointer Authentication */
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# define AARCH64_SIGN_LINK_REGISTER hint #27 /* PACIBSP */
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# define AARCH64_VALIDATE_LINK_REGISTER hint #31 /* AUTIBSP */
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# else
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# define GNU_PROPERTY_AARCH64_POINTER_AUTH 0 /* No Pointer Authentication */
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# if GNU_PROPERTY_AARCH64_BTI != 0
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# define AARCH64_SIGN_LINK_REGISTER AARCH64_VALID_CALL_TARGET
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# else
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# define AARCH64_SIGN_LINK_REGISTER
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# endif
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# define AARCH64_VALIDATE_LINK_REGISTER
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# endif
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# if GNU_PROPERTY_AARCH64_POINTER_AUTH != 0 || GNU_PROPERTY_AARCH64_BTI != 0
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.pushsection .note.gnu.property, "a";
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.balign 8;
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.long 4;
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.long 0x10;
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.long 0x5;
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.asciz "GNU";
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.long 0xc0000000; /* GNU_PROPERTY_AARCH64_FEATURE_1_AND */
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.long 4;
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.long (GNU_PROPERTY_AARCH64_POINTER_AUTH | GNU_PROPERTY_AARCH64_BTI);
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.long 0;
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.popsection;
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# endif
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# endif /* defined __ASSEMBLER__ */
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#endif
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