From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6140C433F5 for ; Wed, 13 Oct 2021 17:53:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 93F526113D for ; Wed, 13 Oct 2021 17:53:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236010AbhJMRzO (ORCPT ); Wed, 13 Oct 2021 13:55:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:59206 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229814AbhJMRzN (ORCPT ); Wed, 13 Oct 2021 13:55:13 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2C8CE61139 for ; Wed, 13 Oct 2021 17:53:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1634147590; bh=bg4eQMSYTVjgOi7gDOpvfbv+2tkdNKMHGQe8r5tgt2I=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=Ltz07qEP3MWnq/VS415PtXV7zM+Hdgb6MU7/99qiYS9vKhGE9lDcGxHmx9n/Y4QX1 qW+elox7pXCPJ4xL/iuYgdGkMtJkJJ7zbDY1e7xNdB7UsXlcwLiU44vS7uAWeL6oXn 8bddrBy/TxEcYNmJFTFrjyO/PSr/vQRNtw6WS9ivEOTY7m1rgKioOAguPm/Unryaud A00+0yRQLVTWT2+BT4iCHfB/UYVf5P1ujQCryyvdMkVLrbtj/7BMB40NEyzJScQx8q dQES+nfnGau9/Xzow9LJKh3NK9M2/OPFprBJAmPpfB2KEpS75JCbfkn9mm9HoK6DOr xsk0h+AJ01FZg== Received: by mail-oi1-f174.google.com with SMTP id o204so4840423oih.13 for ; Wed, 13 Oct 2021 10:53:10 -0700 (PDT) X-Gm-Message-State: AOAM530qy3oma85HmPc7sltSRX8sHHz2kYwKcQp/dlRgaNj1uLGyco7A JIzJlsQvdlcbiD5HZ6v70vdz0DvMK71izjrHzaA= X-Google-Smtp-Source: ABdhPJzim2NCcO+mHPgELqoNVBsCPSNa0JcBsYXpMGjp5agu5hAFKcQ0tflxFfNNj3dna+jXZnI4/z8kGnehxQcV/AA= X-Received: by 2002:aca:32c2:: with SMTP id y185mr9282719oiy.47.1634147589469; Wed, 13 Oct 2021 10:53:09 -0700 (PDT) MIME-Version: 1.0 References: <20211013152243.2216899-1-ardb@kernel.org> In-Reply-To: <20211013152243.2216899-1-ardb@kernel.org> From: Ard Biesheuvel Date: Wed, 13 Oct 2021 19:52:57 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 0/9] arm64: use unwind data on GCC for shadow call stack To: Linux ARM Cc: linux-hardening@vger.kernel.org, Mark Rutland , Catalin Marinas , Will Deacon , Kees Cook , Sami Tolvanen , Fangrui Song , Nick Desaulniers , Dan Li Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Wed, 13 Oct 2021 at 17:22, Ard Biesheuvel wrote: > > This series is a proof of concept implementation of using unwind tables > to locate PACIASP/AUTIASP instructions in the code, and patching them > into shadow call stack pushes/pops at boot time if the platform in > question does not support pointer authentication in hardware. This way, > the overhead of the shadow call stack is only imposed if it actually > gives any benefit. It also means that the compiler does not need to > generate the code, so this works with GCC as well. > > In fact, it only works with GCC at the moment, as Clang does not seem to > implement the DW_CFA_negate_ra_state correctly, which is emitted after > each PACIASP or AUTIASP instruction (Clang only does the former). > However, GCC does not appear to get it quite right either, as it emits > the directive in the wrong place in some cases (but in a way that can be > worked around). > > Note that this only implements it for the core kernel. Modules should be > straight-forward, and most of the code can be reused. Also, the > transformation is applied unconditionally, even if the hardware does > implement PAC, but this does not really matter for a PoC. > > One obvious downside is the size of the unwind tables (3 MiB for > defconfig), although there are plenty of use cases where this does not > really matters (and I haven't checked the compressed size). However, > there may be other reasons why we'd want to have access to these unwind > tables (reliable stack traces), so this will need to be discussed before > I intend to take this any further. > > Cc: Kees Cook > Cc: Sami Tolvanen > Cc: Fangrui Song > Cc: Nick Desaulniers > Cc: Dan Li > Apologies - i failed to pass --cc-cover so the cc'ees above have only received this cover letter. The lore thread is here: https://lore.kernel.org/r/20211013152243.2216899-1-ardb@kernel.org/ > Ard Biesheuvel (9): > arm64: assembler: enable PAC for non-leaf assembler routines > arm64: cache: use ALIAS version of linkage macros for local aliases > arm64: crypto: avoid overlapping linkage definitions for AES-CBC > arm64: aes-neonbs: move frame pop to end of function > arm64: chacha-neon: move frame pop forward > arm64: smccc: create proper stack frames for HVC/SMC calls > arm64: assembler: add unwind annotations to frame push/pop macros > arm64: unwind: add asynchronous unwind tables to the kernel proper > arm64: implement dynamic shadow call stack for GCC > > Makefile | 4 +- > arch/Kconfig | 4 +- > arch/arm64/Kconfig | 11 +- > arch/arm64/Makefile | 7 +- > arch/arm64/crypto/aes-modes.S | 4 +- > arch/arm64/crypto/aes-neonbs-core.S | 8 +- > arch/arm64/crypto/chacha-neon-core.S | 9 +- > arch/arm64/include/asm/assembler.h | 32 ++- > arch/arm64/include/asm/linkage.h | 16 +- > arch/arm64/kernel/Makefile | 2 + > arch/arm64/kernel/head.S | 3 + > arch/arm64/kernel/patch-scs.c | 223 ++++++++++++++++++++ > arch/arm64/kernel/smccc-call.S | 40 ++-- > arch/arm64/kernel/vmlinux.lds.S | 20 ++ > arch/arm64/mm/cache.S | 8 +- > drivers/firmware/efi/libstub/Makefile | 1 + > 16 files changed, 347 insertions(+), 45 deletions(-) > create mode 100644 arch/arm64/kernel/patch-scs.c > > -- > 2.30.2 >