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 X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 64168C43381 for ; Thu, 18 Mar 2021 17:51:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 36C8564F57 for ; Thu, 18 Mar 2021 17:51:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232316AbhCRRu0 (ORCPT ); Thu, 18 Mar 2021 13:50:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42134 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232298AbhCRRuE (ORCPT ); Thu, 18 Mar 2021 13:50:04 -0400 Received: from mail-lf1-x12a.google.com (mail-lf1-x12a.google.com [IPv6:2a00:1450:4864:20::12a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F3BE2C061762 for ; Thu, 18 Mar 2021 10:50:03 -0700 (PDT) Received: by mail-lf1-x12a.google.com with SMTP id j11so5924223lfg.12 for ; Thu, 18 Mar 2021 10:50:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=rnxu0Htej1H516ep79Wgi7n3VX+5maU9JLJNzsCgiUM=; b=Ni7pji1XH63Bsx+pQeydcoFnVFUKTo4EK8YEo+eRY0n8Z2OlAnJtkVrPBHxbEsi1+R +o0D2M9JZb3tGqGl8p3T5U+v1MyYLTUUMRcgkL4iuhrlTfi3bi87ds7MxG2e3n0KlK6i 3dJiohcmgFoCgox4RNZsf0OK7goEnUFKbgGqAAdLekm/+D9U6DNU7jqJvakwMwfDAFa4 v8f//XFUMtHrMKaTRuIfAgjuRPu2++XBnBmKfeuHtrLLgiyJIOsF+rgRl3qxfjWKRupz HuO8O/BYYDPWXJdD72MiPYs06QEHnux8aIOk5Nz61Niw4ufVgh0Hi+g9U0GNCsttzUhd wMtw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=rnxu0Htej1H516ep79Wgi7n3VX+5maU9JLJNzsCgiUM=; b=iWqr491puSMWHvHTBsQdS1BvYCoTrybj6H3XNltUYbXqyiIQ0qTzUNgyZg113PeACs a5nRqp3sBmXv+i0G53poyWj8ZT8NQsxv8JhN28pO9ddEv7FhPbD1Vv2krcHCIFEp5eJr g7pIjgiM70zOzT71B4jZ4AW1yLJOCAHip29gRKf/UGjoaHsro5Wgmx7UOSilnCclgPwc jQPC57psVY/U5eoGMlx36wyUfI/FoA5t0lc15BAtmPSwaab0m0pjqQqOVV50WXE8sOUW Nvq/Q9KwO5r5DBWDOBwDL7HogmlLULSkjRMV4IMLKqL19JmC65jZtKB8T9YHVPQWB0JM oyJw== X-Gm-Message-State: AOAM5308Cu5O05Uu8RMLLVFqrBvEvVAAU0FZS0ZQku4Nrt9UPOwmWlVh ynJtcn//DjiHVVFnvvO2T//btQPMB386WLZ6kmZEuw== X-Google-Smtp-Source: ABdhPJwKRBRM7MAUZwFeZ179486WWfFrS/ksEmFI/VqMTZ8H+kaaJb/iKuGQiKzYL2s45rV0vHLFMREgPO6HFTWGKDo= X-Received: by 2002:a05:6512:985:: with SMTP id w5mr5887489lft.122.1616089801932; Thu, 18 Mar 2021 10:50:01 -0700 (PDT) MIME-Version: 1.0 References: <20210318171111.706303-1-samitolvanen@google.com> <20210318171111.706303-3-samitolvanen@google.com> In-Reply-To: <20210318171111.706303-3-samitolvanen@google.com> From: Nick Desaulniers Date: Thu, 18 Mar 2021 10:49:50 -0700 Message-ID: Subject: Re: [PATCH v2 02/17] cfi: add __cficanonical To: Sami Tolvanen Cc: Kees Cook , Nathan Chancellor , Masahiro Yamada , Will Deacon , Jessica Yu , Arnd Bergmann , Tejun Heo , "Paul E. McKenney" , Christoph Hellwig , bpf , linux-hardening@vger.kernel.org, linux-arch , Linux ARM , Linux Kbuild mailing list , PCI , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Mar 18, 2021 at 10:11 AM Sami Tolvanen wrote: > > With CONFIG_CFI_CLANG, the compiler replaces a function address taken > in C code with the address of a local jump table entry, which passes > runtime indirect call checks. However, the compiler won't replace > addresses taken in assembly code, which will result in a CFI failure > if we later jump to such an address in instrumented C code. The code > generated for the non-canonical jump table looks this: > > : /* In C, &noncanonical points here */ > jmp noncanonical > ... > : /* function body */ > ... > > This change adds the __cficanonical attribute, which tells the > compiler to use a canonical jump table for the function instead. This > means the compiler will rename the actual function to .cfi > and points the original symbol to the jump table entry instead: > > : /* jump table entry */ > jmp canonical.cfi > ... > : /* function body */ > ... > > As a result, the address taken in assembly, or other non-instrumented > code always points to the jump table and therefore, can be used for > indirect calls in instrumented code without tripping CFI checks. > > Signed-off-by: Sami Tolvanen > Reviewed-by: Kees Cook > Acked-by: Bjorn Helgaas # pci.h Irrelevant to this series, but I checked when the FN attr was first available in clang; clang-10. (That's the minimum supported version of clang for the kernel, and this series depends on LTO which depends on clang-12, so no additional guards are necessary). Reviewed-by: Nick Desaulniers > --- > include/linux/compiler-clang.h | 1 + > include/linux/compiler_types.h | 4 ++++ > include/linux/init.h | 4 ++-- > include/linux/pci.h | 4 ++-- > 4 files changed, 9 insertions(+), 4 deletions(-) > > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h > index 6de9d0c9377e..adbe76b203e2 100644 > --- a/include/linux/compiler-clang.h > +++ b/include/linux/compiler-clang.h > @@ -63,3 +63,4 @@ > #endif > > #define __nocfi __attribute__((__no_sanitize__("cfi"))) > +#define __cficanonical __attribute__((__cfi_canonical_jump_table__)) > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > index 796935a37e37..d29bda7f6ebd 100644 > --- a/include/linux/compiler_types.h > +++ b/include/linux/compiler_types.h > @@ -246,6 +246,10 @@ struct ftrace_likely_data { > # define __nocfi > #endif > > +#ifndef __cficanonical > +# define __cficanonical > +#endif > + > #ifndef asm_volatile_goto > #define asm_volatile_goto(x...) asm goto(x) > #endif > diff --git a/include/linux/init.h b/include/linux/init.h > index b3ea15348fbd..045ad1650ed1 100644 > --- a/include/linux/init.h > +++ b/include/linux/init.h > @@ -220,8 +220,8 @@ extern bool initcall_debug; > __initcall_name(initstub, __iid, id) > > #define __define_initcall_stub(__stub, fn) \ > - int __init __stub(void); \ > - int __init __stub(void) \ > + int __init __cficanonical __stub(void); \ > + int __init __cficanonical __stub(void) \ > { \ > return fn(); \ > } \ > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 86c799c97b77..39684b72db91 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -1944,8 +1944,8 @@ enum pci_fixup_pass { > #ifdef CONFIG_LTO_CLANG > #define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \ > class_shift, hook, stub) \ > - void stub(struct pci_dev *dev); \ > - void stub(struct pci_dev *dev) \ > + void __cficanonical stub(struct pci_dev *dev); \ > + void __cficanonical stub(struct pci_dev *dev) \ > { \ > hook(dev); \ > } \ > -- > 2.31.0.291.g576ba9dcdaf-goog > -- Thanks, ~Nick Desaulniers