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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 21A57CA9EA0 for ; Fri, 25 Oct 2019 09:24:50 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 6F14B2070B for ; Fri, 25 Oct 2019 09:24:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6F14B2070B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17104-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 28176 invoked by uid 550); 25 Oct 2019 09:24:41 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 28156 invoked from network); 25 Oct 2019 09:24:41 -0000 Date: Fri, 25 Oct 2019 10:24:22 +0100 From: Mark Rutland To: samitolvanen@google.com Cc: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Dave Martin , Kees Cook , Laura Abbott , Nick Desaulniers , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 01/17] arm64: mm: don't use x18 in idmap_kpti_install_ng_mappings Message-ID: <20191025092421.GA40270@lakrids.cambridge.arm.com> References: <20191018161033.261971-1-samitolvanen@google.com> <20191024225132.13410-1-samitolvanen@google.com> <20191024225132.13410-2-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191024225132.13410-2-samitolvanen@google.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) On Thu, Oct 24, 2019 at 03:51:16PM -0700, samitolvanen@google.com wrote: > idmap_kpti_install_ng_mappings uses x18 as a temporary register, which > will result in a conflict when x18 is reserved. Use x16 and x17 instead > where needed. > > Signed-off-by: Sami Tolvanen > Reviewed-by: Nick Desaulniers AFAICT the new register assignment is sound, so FWIW: Reviewed-by: Mark Rutland I was going to suggest adding menmonics for the remamining raw register names, but after having a go locally I think it's cleaner as-is given the registers are used in different widths for multiple purposes. Thanks, Mark. > --- > arch/arm64/mm/proc.S | 63 ++++++++++++++++++++++---------------------- > 1 file changed, 32 insertions(+), 31 deletions(-) > > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S > index a1e0592d1fbc..fdabf40a83c8 100644 > --- a/arch/arm64/mm/proc.S > +++ b/arch/arm64/mm/proc.S > @@ -250,15 +250,15 @@ ENTRY(idmap_kpti_install_ng_mappings) > /* We're the boot CPU. Wait for the others to catch up */ > sevl > 1: wfe > - ldaxr w18, [flag_ptr] > - eor w18, w18, num_cpus > - cbnz w18, 1b > + ldaxr w17, [flag_ptr] > + eor w17, w17, num_cpus > + cbnz w17, 1b > > /* We need to walk swapper, so turn off the MMU. */ > pre_disable_mmu_workaround > - mrs x18, sctlr_el1 > - bic x18, x18, #SCTLR_ELx_M > - msr sctlr_el1, x18 > + mrs x17, sctlr_el1 > + bic x17, x17, #SCTLR_ELx_M > + msr sctlr_el1, x17 > isb > > /* Everybody is enjoying the idmap, so we can rewrite swapper. */ > @@ -281,9 +281,9 @@ skip_pgd: > isb > > /* We're done: fire up the MMU again */ > - mrs x18, sctlr_el1 > - orr x18, x18, #SCTLR_ELx_M > - msr sctlr_el1, x18 > + mrs x17, sctlr_el1 > + orr x17, x17, #SCTLR_ELx_M > + msr sctlr_el1, x17 > isb > > /* > @@ -353,46 +353,47 @@ skip_pte: > b.ne do_pte > b next_pmd > > + .unreq cpu > + .unreq num_cpus > + .unreq swapper_pa > + .unreq cur_pgdp > + .unreq end_pgdp > + .unreq pgd > + .unreq cur_pudp > + .unreq end_pudp > + .unreq pud > + .unreq cur_pmdp > + .unreq end_pmdp > + .unreq pmd > + .unreq cur_ptep > + .unreq end_ptep > + .unreq pte > + > /* Secondary CPUs end up here */ > __idmap_kpti_secondary: > /* Uninstall swapper before surgery begins */ > - __idmap_cpu_set_reserved_ttbr1 x18, x17 > + __idmap_cpu_set_reserved_ttbr1 x16, x17 > > /* Increment the flag to let the boot CPU we're ready */ > -1: ldxr w18, [flag_ptr] > - add w18, w18, #1 > - stxr w17, w18, [flag_ptr] > +1: ldxr w16, [flag_ptr] > + add w16, w16, #1 > + stxr w17, w16, [flag_ptr] > cbnz w17, 1b > > /* Wait for the boot CPU to finish messing around with swapper */ > sevl > 1: wfe > - ldxr w18, [flag_ptr] > - cbnz w18, 1b > + ldxr w16, [flag_ptr] > + cbnz w16, 1b > > /* All done, act like nothing happened */ > - offset_ttbr1 swapper_ttb, x18 > + offset_ttbr1 swapper_ttb, x16 > msr ttbr1_el1, swapper_ttb > isb > ret > > - .unreq cpu > - .unreq num_cpus > - .unreq swapper_pa > .unreq swapper_ttb > .unreq flag_ptr > - .unreq cur_pgdp > - .unreq end_pgdp > - .unreq pgd > - .unreq cur_pudp > - .unreq end_pudp > - .unreq pud > - .unreq cur_pmdp > - .unreq end_pmdp > - .unreq pmd > - .unreq cur_ptep > - .unreq end_ptep > - .unreq pte > ENDPROC(idmap_kpti_install_ng_mappings) > .popsection > #endif > -- > 2.24.0.rc0.303.g954a862665-goog >