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=-14.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 E8DBBCA9EA9 for ; Fri, 18 Oct 2019 16:43:51 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 122E421835 for ; Fri, 18 Oct 2019 16:43:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="a4KqHH64" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 122E421835 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17039-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 11540 invoked by uid 550); 18 Oct 2019 16:43:44 -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 11516 invoked from network); 18 Oct 2019 16:43:43 -0000 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=itPDN3uOMullCrqvdWp4VHOtEiVy99lUJjyxqObTixM=; b=a4KqHH64Syi3Jkb+d0eVgCpN+31SnDYFhDKhObeeBYgIxsVpB28MK9tNghzsFxuX+N VbAKU58UasFmej23pHOk0QrDLH7oKDm4M3dk3bgCtTUWOgQmltwfMriaPvVLpxp3C0pC kYoPXPqJx0ajXSrYjPEgK8592+nVdo/5DSLpSz/Itc5Br1qMc82P+2UjLLk4LyZ199qw YdBPa6JePJa0Fd7+ocz3Fs2qom1i2u3DIw3HjxianaEOsPf5x+/L3CFK6vBNgDV9SqT3 pgNBOC5FZlvErDViSZm4W/P+hr6vWNgjySr+vmQ1yyL5jifp07AxbcGC3bkxHitLbGMK lX4A== 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=itPDN3uOMullCrqvdWp4VHOtEiVy99lUJjyxqObTixM=; b=qeKTIFDs2BmlKXy0Bw6YA50i0cJi/uSECQL3et2fOpfuG5PwAiwW1L/sK0V17hX9p+ IIIoOqs1FMrwy6OjaB5PQVy8rJP8cdEST09vp70UKCwzN4UjeThvHOiig51Gkh3f8oUs 2v/autCa8BO9rEtWUvOtGViD/wY6WZNvK4M5lBNexQ+2qWX4rQ5oxNSQkfnn+R5dBf/S B7sUVN5jCRBm45wQtwWJXpckJkVdca2H4ZeZ35heHjhzIvimqgw15oSjJ+1HH2VixCRs 20pgnG1oqoc09rLdV8P7GEGsQbR5nVuZuhumceuVeYwmsmYuSjvM9AzT6nc5Au8vDjD8 E2zA== X-Gm-Message-State: APjAAAUP5CwTuhToF3Xzl5UbiHV2wv923KJFwFdACEHfW3b9e8+PNoY3 ospZ+SEoWCMHUaiptjOLCheUtN0oMqpbMmN1m/I8yw== X-Google-Smtp-Source: APXvYqxjABHlLirt3mzHAGsgLEpxUZMPZex/FsD7C0vJFW62s876ojGzoWlX6A4J5FwacSy764TFAtK8KXx4Wiz+QQw= X-Received: by 2002:a17:902:9b83:: with SMTP id y3mr10710877plp.179.1571417011191; Fri, 18 Oct 2019 09:43:31 -0700 (PDT) MIME-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191018161033.261971-2-samitolvanen@google.com> In-Reply-To: <20191018161033.261971-2-samitolvanen@google.com> From: Nick Desaulniers Date: Fri, 18 Oct 2019 09:43:20 -0700 Message-ID: Subject: Re: [PATCH 01/18] arm64: mm: don't use x18 in idmap_kpti_install_ng_mappings To: Sami Tolvanen Cc: Will Deacon , Catalin Marinas , Steven Rostedt , Ard Biesheuvel , Dave Martin , Kees Cook , Laura Abbott , Mark Rutland , clang-built-linux , kernel-hardening@lists.openwall.com, Linux ARM , LKML Content-Type: text/plain; charset="UTF-8" On Fri, Oct 18, 2019 at 9:10 AM Sami Tolvanen 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 TIL about .req/.unreq. Seems like a nice way of marking "variable" lifetime. Technically, only `pte` needed to be moved to reuse {w|x}16, but moving most the unreqs together is nicer than splitting them apart. The usage all looks correct to me. Reviewed-by: Nick Desaulniers > --- > 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 > -- > 2.23.0.866.gb869b98d4c-goog > -- Thanks, ~Nick Desaulniers