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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 0F586C43470 for ; Tue, 6 Apr 2021 11:54:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BBD37613B3 for ; Tue, 6 Apr 2021 11:54:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343560AbhDFLyT (ORCPT ); Tue, 6 Apr 2021 07:54:19 -0400 Received: from foss.arm.com ([217.140.110.172]:41848 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343558AbhDFLyN (ORCPT ); Tue, 6 Apr 2021 07:54:13 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ACB70113E; Tue, 6 Apr 2021 04:54:05 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9F9E23F73D; Tue, 6 Apr 2021 04:54:00 -0700 (PDT) Date: Tue, 6 Apr 2021 12:53:57 +0100 From: Mark Rutland To: Sami Tolvanen , Ard Biesheuvel Cc: Kees Cook , Nathan Chancellor , Nick Desaulniers , Masahiro Yamada , Will Deacon , Jessica Yu , Arnd Bergmann , Tejun Heo , "Paul E. McKenney" , Christoph Hellwig , Peter Zijlstra , Sedat Dilek , Catalin Marinas , bpf@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, ardb@kernel.org Subject: Re: [PATCH v5 14/18] arm64: add __nocfi to functions that jump to a physical address Message-ID: <20210406115357.GE96480@C02TD0UTHF1T.local> References: <20210401233216.2540591-1-samitolvanen@google.com> <20210401233216.2540591-15-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210401233216.2540591-15-samitolvanen@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [adding Ard for EFI runtime services bits] On Thu, Apr 01, 2021 at 04:32:12PM -0700, Sami Tolvanen wrote: > Disable CFI checking for functions that switch to linear mapping and > make an indirect call to a physical address, since the compiler only > understands virtual addresses and the CFI check for such indirect calls > would always fail. What does physical vs virtual have to do with this? Does the address actually matter, or is this just a general thing that when calling an assembly function we won't have a trampoline that the caller expects? I wonder if we need to do something with asmlinkage here, perhaps? I didn't spot anything in the seriues handling EFI runtime services calls, and I strongly suspect we need to do something for those, unless they're handled implicitly by something else. > Signed-off-by: Sami Tolvanen > Reviewed-by: Kees Cook > --- > arch/arm64/include/asm/mmu_context.h | 2 +- > arch/arm64/kernel/cpu-reset.h | 8 ++++---- > arch/arm64/kernel/cpufeature.c | 2 +- > 3 files changed, 6 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h > index 386b96400a57..d3cef9133539 100644 > --- a/arch/arm64/include/asm/mmu_context.h > +++ b/arch/arm64/include/asm/mmu_context.h > @@ -119,7 +119,7 @@ static inline void cpu_install_idmap(void) > * Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD, > * avoiding the possibility of conflicting TLB entries being allocated. > */ > -static inline void cpu_replace_ttbr1(pgd_t *pgdp) > +static inline void __nocfi cpu_replace_ttbr1(pgd_t *pgdp) Given these are inlines, what's the effect when these are inlined into a function that would normally use CFI? Does CFI get supressed for the whole function, or just the bit that got inlined? Is there an attribute that we could place on a function pointer to tell the compiler to not check calls via that pointer? If that existed we'd be able to scope this much more tightly. Thanks, Mark. > { > typedef void (ttbr_replace_func)(phys_addr_t); > extern ttbr_replace_func idmap_cpu_replace_ttbr1; > diff --git a/arch/arm64/kernel/cpu-reset.h b/arch/arm64/kernel/cpu-reset.h > index f3adc574f969..9a7b1262ef17 100644 > --- a/arch/arm64/kernel/cpu-reset.h > +++ b/arch/arm64/kernel/cpu-reset.h > @@ -13,10 +13,10 @@ > void __cpu_soft_restart(unsigned long el2_switch, unsigned long entry, > unsigned long arg0, unsigned long arg1, unsigned long arg2); > > -static inline void __noreturn cpu_soft_restart(unsigned long entry, > - unsigned long arg0, > - unsigned long arg1, > - unsigned long arg2) > +static inline void __noreturn __nocfi cpu_soft_restart(unsigned long entry, > + unsigned long arg0, > + unsigned long arg1, > + unsigned long arg2) > { > typeof(__cpu_soft_restart) *restart; > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 0b2e0d7b13ec..c2f94a5206e0 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -1445,7 +1445,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > } > > #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 > -static void > +static void __nocfi > kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused) > { > typedef void (kpti_remap_fn)(int, int, phys_addr_t); > -- > 2.31.0.208.g409f899ff0-goog >