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=-6.8 required=3.0 tests=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 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 C099FCA9EB5 for ; Mon, 21 Oct 2019 06:19:52 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 112E921479 for ; Mon, 21 Oct 2019 06:19:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="WOzYqE+L" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 112E921479 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17070-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 31761 invoked by uid 550); 21 Oct 2019 06:19:45 -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 30719 invoked from network); 21 Oct 2019 06:19:45 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=iMdLEV+CTaW2gmBLhEBpHxDKc063E21l+ayq5nzIrFw=; b=WOzYqE+LWe+E/HVhSozCNdcMsHavUK6DUIItAaXEkClsKdQaQfB42QALzHNS2WWwYS 7/nd0om4bK/hNaghrCrAxwLmdR73Z4tXnnuwroc0+54D/uEAdDUy0U3x7XFfcuNcacaM G2t2PVl0OEsWAs+ON0q7SJAm80g0Gockqb5V9TwDq9CgrsLxWwFINCmx8t7mDomvn163 au+GtLS99ib8TAWDJ1J+jgd/h16JcLxkcT/O5E+tFPIrOxgasAcAQUkydYejvXgehJGR CJoWn+myZwethBoe0UOOL2ixvKeT7IQpefZS3Izts0s0MnBwR25h089ZPQbW0zpPnsFy R5+g== 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=iMdLEV+CTaW2gmBLhEBpHxDKc063E21l+ayq5nzIrFw=; b=abjldrjuZeHFi3NNdVrmmgwmVAgcDa+eWGVCCUDgQydC/Zqc6VDH/VM5cSSzJjemZj e8o4MzUV6dXFARsEW+I/p7y7DcVmwBEQGd8e4wIpE45QrdOBrnvK0O0Rw9UAw4ArkFlL aQ1hdLY2kEi77cui9zDXTpIX+J8+SysXnowT98/kL26Que3PeAFNuUc1rb569bALsvHp +vWUJ0AVoyi72cEWZO3yoACcRPchIjovcKYz/KDScKlPnk6bTwF0k+ZvGjPh2oXafuJ7 /8M5Bo3s0gqroINenV/qYHlV57ezAIWBCyAkphvNo9GH0+CA4tjrBBsOET/grBtJfmsF gFYA== X-Gm-Message-State: APjAAAUcT7RVLzwrprCb0XOTHkDUHfSAzitZ3tlw08HZeE7hM5em1Xq6 wkuGN9Tl8ECwdZigH4R7NbrIYYrD65D1N/UO01QSeA== X-Google-Smtp-Source: APXvYqwtVZTOqZaaU9Te8Vy1PYbGo0mpgYTxtO/oPglrkIr329wlVgskZ9sxWEpAm2PexwLH+zbd9/RN3RL88+vlV/U= X-Received: by 2002:a1c:64d6:: with SMTP id y205mr1400556wmb.136.1571638773936; Sun, 20 Oct 2019 23:19:33 -0700 (PDT) MIME-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191018161033.261971-4-samitolvanen@google.com> In-Reply-To: <20191018161033.261971-4-samitolvanen@google.com> From: Ard Biesheuvel Date: Mon, 21 Oct 2019 08:19:23 +0200 Message-ID: Subject: Re: [PATCH 03/18] arm64: kvm: stop treating register x18 as caller save To: Sami Tolvanen Cc: Will Deacon , Catalin Marinas , Steven Rostedt , Dave Martin , Kees Cook , Laura Abbott , Mark Rutland , Nick Desaulniers , clang-built-linux , Kernel Hardening , linux-arm-kernel , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" On Fri, 18 Oct 2019 at 18:10, Sami Tolvanen wrote: > > From: Ard Biesheuvel > > In preparation of using x18 as a task struct pointer register when > running in the kernel, stop treating it as caller save in the KVM > guest entry/exit code. Currently, the code assumes there is no need > to preserve it for the host, given that it would have been assumed > clobbered anyway by the function call to __guest_enter(). Instead, > preserve its value and restore it upon return. > > Link: https://patchwork.kernel.org/patch/9836891/ > Signed-off-by: Ard Biesheuvel > Signed-off-by: Sami Tolvanen You might want to update the commit log to drop the reference to the task struct pointer. > --- > arch/arm64/kvm/hyp/entry.S | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S > index e5cc8d66bf53..20bd9a20ea27 100644 > --- a/arch/arm64/kvm/hyp/entry.S > +++ b/arch/arm64/kvm/hyp/entry.S > @@ -23,6 +23,7 @@ > .pushsection .hyp.text, "ax" > > .macro save_callee_saved_regs ctxt > + str x18, [\ctxt, #CPU_XREG_OFFSET(18)] > stp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)] > stp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)] > stp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)] > @@ -38,6 +39,7 @@ > ldp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)] > ldp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)] > ldp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)] > + ldr x18, [\ctxt, #CPU_XREG_OFFSET(18)] > .endm > > /* > @@ -87,12 +89,9 @@ alternative_else_nop_endif > ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)] > ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)] > > - // Restore guest regs x19-x29, lr > + // Restore guest regs x18-x29, lr > restore_callee_saved_regs x18 > > - // Restore guest reg x18 > - ldr x18, [x18, #CPU_XREG_OFFSET(18)] > - > // Do not touch any register after this! > eret > sb > @@ -114,7 +113,7 @@ ENTRY(__guest_exit) > // Retrieve the guest regs x0-x1 from the stack > ldp x2, x3, [sp], #16 // x0, x1 > > - // Store the guest regs x0-x1 and x4-x18 > + // Store the guest regs x0-x1 and x4-x17 > stp x2, x3, [x1, #CPU_XREG_OFFSET(0)] > stp x4, x5, [x1, #CPU_XREG_OFFSET(4)] > stp x6, x7, [x1, #CPU_XREG_OFFSET(6)] > @@ -123,9 +122,8 @@ ENTRY(__guest_exit) > stp x12, x13, [x1, #CPU_XREG_OFFSET(12)] > stp x14, x15, [x1, #CPU_XREG_OFFSET(14)] > stp x16, x17, [x1, #CPU_XREG_OFFSET(16)] > - str x18, [x1, #CPU_XREG_OFFSET(18)] > > - // Store the guest regs x19-x29, lr > + // Store the guest regs x18-x29, lr > save_callee_saved_regs x1 > > get_host_ctxt x2, x3 > -- > 2.23.0.866.gb869b98d4c-goog >