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=-17.4 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_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham 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 BF41ECA9ECB for ; Thu, 31 Oct 2019 16:46:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7C1C6222D0 for ; Thu, 31 Oct 2019 16:46:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="VeV07+y/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728873AbfJaQqy (ORCPT ); Thu, 31 Oct 2019 12:46:54 -0400 Received: from mail-pf1-f201.google.com ([209.85.210.201]:46066 "EHLO mail-pf1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728854AbfJaQqw (ORCPT ); Thu, 31 Oct 2019 12:46:52 -0400 Received: by mail-pf1-f201.google.com with SMTP id a14so4999775pfr.12 for ; Thu, 31 Oct 2019 09:46:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=FBkL0U7+mf5tcaSnPbZxQ7YN9ZSyYOV+Z9+Nl88/ERI=; b=VeV07+y/vZQMBPIGrWmEcN17NfUoL03xMkxy1CCe4nlsSpjdC/P/A7pU1PaSQAoaC4 yhQxR7V5Sze8M+kndBe6LqPB2aAkSx435gMvCe5Xr+ZmLLya44v9PAdlRVnM1C+6wl+V S1wNwAHn7FYnyQVpaOZ07mIDdFzL9vScqpX65tU2wxXwD52a54e9I+3cEH64o/Xmc3+r xr3Jgbe/jKwXa/SmooBBrjDK/CP2axgvDd8BrIAAVZXVKYEewhczgFi97fa/8ggAWFSs i4iLoSFfavLDhRxy2EtVhvkwWNU5Zc/SvzvXnZ4t1GlXrCZoOIf8AsyK/9x2BQE7Cb/J EKDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=FBkL0U7+mf5tcaSnPbZxQ7YN9ZSyYOV+Z9+Nl88/ERI=; b=hrWcajLOlBkZpgm4l9IpB9hDe7LmaPMkjBW/8UwfJ38e2kjeTiGbR4oPejY5TUhpr/ gCAZk4MItSKq2X1SE3KLiNGIFpDUrbmvMIqPW0swzeoSaPgT2psY05ZgBEvgKHJRLAuH fP+NiU88fm1Z/7NGkWeQMoMv4Q/WHifXK5G2yOo9GQPgJ8DX/yZEQ+bvKzl0X+mgN1fw u82VNqCRR6JHJfwnUAv351/SNR42wRrJDEUf+Bu3mOZLG2N21liY+8wPBs2D7dR0q92i d9OFPyzttdT3bnXoUcJf732fDgL6tFESGxpPlztaStZXU5hgnEtdbGdAM9H/YRiMqKVj nASg== X-Gm-Message-State: APjAAAUdfOW/+T77kYS0nx0TafZOcLoW1TpLHnYzxGCl8+kq51nv0kvm C7KMjTvPsL7A/i7MvkzIOay7eO/UHO2+4i98niA= X-Google-Smtp-Source: APXvYqwvSAzK7+rkcq2jVtKJglETlc7GpzZ/DLe6JRtqcrszDVQGnwVjheehlI36t6UkuGM2430j8oW3UHk8cjBajIM= X-Received: by 2002:a63:cf18:: with SMTP id j24mr8035896pgg.406.1572540411406; Thu, 31 Oct 2019 09:46:51 -0700 (PDT) Date: Thu, 31 Oct 2019 09:46:23 -0700 In-Reply-To: <20191031164637.48901-1-samitolvanen@google.com> Message-Id: <20191031164637.48901-4-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191031164637.48901-1-samitolvanen@google.com> X-Mailer: git-send-email 2.24.0.rc0.303.g954a862665-goog Subject: [PATCH v3 03/17] arm64: kvm: stop treating register x18 as caller save From: samitolvanen@google.com To: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel Cc: Dave Martin , Kees Cook , Laura Abbott , Mark Rutland , 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, Sami Tolvanen Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In preparation of reserving x18, 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/ Co-developed-by: Ard Biesheuvel [ updated commit message, switched from x18 to x29 for the guest context ] Signed-off-by: Sami Tolvanen --- arch/arm64/kvm/hyp/entry.S | 41 +++++++++++++++++++------------------- 1 file changed, 20 insertions(+), 21 deletions(-) diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index e5cc8d66bf53..c3c2d842c609 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)] @@ -32,6 +33,8 @@ .endm .macro restore_callee_saved_regs ctxt + // We assume \ctxt is not x18-x28 + ldr x18, [\ctxt, #CPU_XREG_OFFSET(18)] ldp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)] ldp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)] ldp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)] @@ -48,7 +51,7 @@ ENTRY(__guest_enter) // x0: vcpu // x1: host context // x2-x17: clobbered by macros - // x18: guest context + // x29: guest context // Store the host regs save_callee_saved_regs x1 @@ -67,31 +70,28 @@ alternative_else_nop_endif ret 1: - add x18, x0, #VCPU_CONTEXT + add x29, x0, #VCPU_CONTEXT // Macro ptrauth_switch_to_guest format: // ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3) // The below macro to restore guest keys is not implemented in C code // as it may cause Pointer Authentication key signing mismatch errors // when this feature is enabled for kernel code. - ptrauth_switch_to_guest x18, x0, x1, x2 + ptrauth_switch_to_guest x29, x0, x1, x2 // Restore guest regs x0-x17 - ldp x0, x1, [x18, #CPU_XREG_OFFSET(0)] - ldp x2, x3, [x18, #CPU_XREG_OFFSET(2)] - ldp x4, x5, [x18, #CPU_XREG_OFFSET(4)] - ldp x6, x7, [x18, #CPU_XREG_OFFSET(6)] - ldp x8, x9, [x18, #CPU_XREG_OFFSET(8)] - ldp x10, x11, [x18, #CPU_XREG_OFFSET(10)] - ldp x12, x13, [x18, #CPU_XREG_OFFSET(12)] - ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)] - ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)] - - // Restore guest regs x19-x29, lr - restore_callee_saved_regs x18 - - // Restore guest reg x18 - ldr x18, [x18, #CPU_XREG_OFFSET(18)] + ldp x0, x1, [x29, #CPU_XREG_OFFSET(0)] + ldp x2, x3, [x29, #CPU_XREG_OFFSET(2)] + ldp x4, x5, [x29, #CPU_XREG_OFFSET(4)] + ldp x6, x7, [x29, #CPU_XREG_OFFSET(6)] + ldp x8, x9, [x29, #CPU_XREG_OFFSET(8)] + ldp x10, x11, [x29, #CPU_XREG_OFFSET(10)] + ldp x12, x13, [x29, #CPU_XREG_OFFSET(12)] + ldp x14, x15, [x29, #CPU_XREG_OFFSET(14)] + ldp x16, x17, [x29, #CPU_XREG_OFFSET(16)] + + // Restore guest regs x18-x29, lr + restore_callee_saved_regs x29 // Do not touch any register after this! eret @@ -114,7 +114,7 @@ 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 +123,8 @@ 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 -- 2.24.0.rc0.303.g954a862665-goog 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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_ADSP_CUSTOM_MED,DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 2B8A7CA9ECB for ; 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Thu, 31 Oct 2019 09:46:51 -0700 (PDT) Date: Thu, 31 Oct 2019 09:46:23 -0700 In-Reply-To: <20191031164637.48901-1-samitolvanen@google.com> Message-Id: <20191031164637.48901-4-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191031164637.48901-1-samitolvanen@google.com> X-Mailer: git-send-email 2.24.0.rc0.303.g954a862665-goog Subject: [PATCH v3 03/17] arm64: kvm: stop treating register x18 as caller save From: samitolvanen@google.com To: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191031_094653_627778_045D0F20 X-CRM114-Status: GOOD ( 10.90 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Kees Cook , Jann Horn , Masahiro Yamada , kernel-hardening@lists.openwall.com, Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , clang-built-linux@googlegroups.com, Sami Tolvanen , Laura Abbott , Dave Martin , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org In preparation of reserving x18, 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/ Co-developed-by: Ard Biesheuvel [ updated commit message, switched from x18 to x29 for the guest context ] Signed-off-by: Sami Tolvanen --- arch/arm64/kvm/hyp/entry.S | 41 +++++++++++++++++++------------------- 1 file changed, 20 insertions(+), 21 deletions(-) diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index e5cc8d66bf53..c3c2d842c609 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)] @@ -32,6 +33,8 @@ .endm .macro restore_callee_saved_regs ctxt + // We assume \ctxt is not x18-x28 + ldr x18, [\ctxt, #CPU_XREG_OFFSET(18)] ldp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)] ldp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)] ldp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)] @@ -48,7 +51,7 @@ ENTRY(__guest_enter) // x0: vcpu // x1: host context // x2-x17: clobbered by macros - // x18: guest context + // x29: guest context // Store the host regs save_callee_saved_regs x1 @@ -67,31 +70,28 @@ alternative_else_nop_endif ret 1: - add x18, x0, #VCPU_CONTEXT + add x29, x0, #VCPU_CONTEXT // Macro ptrauth_switch_to_guest format: // ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3) // The below macro to restore guest keys is not implemented in C code // as it may cause Pointer Authentication key signing mismatch errors // when this feature is enabled for kernel code. - ptrauth_switch_to_guest x18, x0, x1, x2 + ptrauth_switch_to_guest x29, x0, x1, x2 // Restore guest regs x0-x17 - ldp x0, x1, [x18, #CPU_XREG_OFFSET(0)] - ldp x2, x3, [x18, #CPU_XREG_OFFSET(2)] - ldp x4, x5, [x18, #CPU_XREG_OFFSET(4)] - ldp x6, x7, [x18, #CPU_XREG_OFFSET(6)] - ldp x8, x9, [x18, #CPU_XREG_OFFSET(8)] - ldp x10, x11, [x18, #CPU_XREG_OFFSET(10)] - ldp x12, x13, [x18, #CPU_XREG_OFFSET(12)] - ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)] - ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)] - - // Restore guest regs x19-x29, lr - restore_callee_saved_regs x18 - - // Restore guest reg x18 - ldr x18, [x18, #CPU_XREG_OFFSET(18)] + ldp x0, x1, [x29, #CPU_XREG_OFFSET(0)] + ldp x2, x3, [x29, #CPU_XREG_OFFSET(2)] + ldp x4, x5, [x29, #CPU_XREG_OFFSET(4)] + ldp x6, x7, [x29, #CPU_XREG_OFFSET(6)] + ldp x8, x9, [x29, #CPU_XREG_OFFSET(8)] + ldp x10, x11, [x29, #CPU_XREG_OFFSET(10)] + ldp x12, x13, [x29, #CPU_XREG_OFFSET(12)] + ldp x14, x15, [x29, #CPU_XREG_OFFSET(14)] + ldp x16, x17, [x29, #CPU_XREG_OFFSET(16)] + + // Restore guest regs x18-x29, lr + restore_callee_saved_regs x29 // Do not touch any register after this! eret @@ -114,7 +114,7 @@ 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 +123,8 @@ 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 -- 2.24.0.rc0.303.g954a862665-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel 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=-17.4 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_AGENT_GIT,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 B1664CA9ECB for ; Thu, 31 Oct 2019 16:59:26 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id CB1072086D for ; Thu, 31 Oct 2019 16:59:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="VeV07+y/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CB1072086D 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-17188-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 27654 invoked by uid 550); 31 Oct 2019 16:59:00 -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 13622 invoked from network); 31 Oct 2019 16:47:03 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=FBkL0U7+mf5tcaSnPbZxQ7YN9ZSyYOV+Z9+Nl88/ERI=; b=VeV07+y/vZQMBPIGrWmEcN17NfUoL03xMkxy1CCe4nlsSpjdC/P/A7pU1PaSQAoaC4 yhQxR7V5Sze8M+kndBe6LqPB2aAkSx435gMvCe5Xr+ZmLLya44v9PAdlRVnM1C+6wl+V S1wNwAHn7FYnyQVpaOZ07mIDdFzL9vScqpX65tU2wxXwD52a54e9I+3cEH64o/Xmc3+r xr3Jgbe/jKwXa/SmooBBrjDK/CP2axgvDd8BrIAAVZXVKYEewhczgFi97fa/8ggAWFSs i4iLoSFfavLDhRxy2EtVhvkwWNU5Zc/SvzvXnZ4t1GlXrCZoOIf8AsyK/9x2BQE7Cb/J EKDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=FBkL0U7+mf5tcaSnPbZxQ7YN9ZSyYOV+Z9+Nl88/ERI=; b=cVEdL7+yuihT0MT37uLYu18t7YzEegcfNdDKFNbcve/oz3Emn8KJtgx5avvRi+4Vql YoPZyRKP8xQ1GtstScAJI4VgqzvNTtta3Qbhnb8RwN4rIgsj8xna9L+Mik09r6v0RBxJ QqbLnGU4ejGrYP+8R5MTF/pH9PhJcSYbFNb0ehSJuvX9R1duuhNd6nLaiBREvCEYMRBW lA/l/QrVbPXjcT3GV0gmSxeswhrS/HtmITOWorjj/sqweeBNRQp0+N78MfHXoNRpzUe2 K3RMA1bDOwDOAp08ytq/0vPzbY5dOcbZRBX7hTOJAJuX+nhsOePPCfdChfSp/FMskfjR hD/Q== X-Gm-Message-State: APjAAAVxDR8X6uNXAUSZnxtC8mH/UyoSmW/FAp7rVaaHmXNSjRMaKFc+ UweArBq+SyMd+Cz6uw+AMUNxJAMWFyUe4kqqvys= X-Google-Smtp-Source: APXvYqwvSAzK7+rkcq2jVtKJglETlc7GpzZ/DLe6JRtqcrszDVQGnwVjheehlI36t6UkuGM2430j8oW3UHk8cjBajIM= X-Received: by 2002:a63:cf18:: with SMTP id j24mr8035896pgg.406.1572540411406; Thu, 31 Oct 2019 09:46:51 -0700 (PDT) Date: Thu, 31 Oct 2019 09:46:23 -0700 In-Reply-To: <20191031164637.48901-1-samitolvanen@google.com> Message-Id: <20191031164637.48901-4-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191031164637.48901-1-samitolvanen@google.com> X-Mailer: git-send-email 2.24.0.rc0.303.g954a862665-goog Subject: [PATCH v3 03/17] arm64: kvm: stop treating register x18 as caller save From: samitolvanen@google.com To: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel Cc: Dave Martin , Kees Cook , Laura Abbott , Mark Rutland , 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, Sami Tolvanen Content-Type: text/plain; charset="UTF-8" In preparation of reserving x18, 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/ Co-developed-by: Ard Biesheuvel [ updated commit message, switched from x18 to x29 for the guest context ] Signed-off-by: Sami Tolvanen --- arch/arm64/kvm/hyp/entry.S | 41 +++++++++++++++++++------------------- 1 file changed, 20 insertions(+), 21 deletions(-) diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index e5cc8d66bf53..c3c2d842c609 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)] @@ -32,6 +33,8 @@ .endm .macro restore_callee_saved_regs ctxt + // We assume \ctxt is not x18-x28 + ldr x18, [\ctxt, #CPU_XREG_OFFSET(18)] ldp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)] ldp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)] ldp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)] @@ -48,7 +51,7 @@ ENTRY(__guest_enter) // x0: vcpu // x1: host context // x2-x17: clobbered by macros - // x18: guest context + // x29: guest context // Store the host regs save_callee_saved_regs x1 @@ -67,31 +70,28 @@ alternative_else_nop_endif ret 1: - add x18, x0, #VCPU_CONTEXT + add x29, x0, #VCPU_CONTEXT // Macro ptrauth_switch_to_guest format: // ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3) // The below macro to restore guest keys is not implemented in C code // as it may cause Pointer Authentication key signing mismatch errors // when this feature is enabled for kernel code. - ptrauth_switch_to_guest x18, x0, x1, x2 + ptrauth_switch_to_guest x29, x0, x1, x2 // Restore guest regs x0-x17 - ldp x0, x1, [x18, #CPU_XREG_OFFSET(0)] - ldp x2, x3, [x18, #CPU_XREG_OFFSET(2)] - ldp x4, x5, [x18, #CPU_XREG_OFFSET(4)] - ldp x6, x7, [x18, #CPU_XREG_OFFSET(6)] - ldp x8, x9, [x18, #CPU_XREG_OFFSET(8)] - ldp x10, x11, [x18, #CPU_XREG_OFFSET(10)] - ldp x12, x13, [x18, #CPU_XREG_OFFSET(12)] - ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)] - ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)] - - // Restore guest regs x19-x29, lr - restore_callee_saved_regs x18 - - // Restore guest reg x18 - ldr x18, [x18, #CPU_XREG_OFFSET(18)] + ldp x0, x1, [x29, #CPU_XREG_OFFSET(0)] + ldp x2, x3, [x29, #CPU_XREG_OFFSET(2)] + ldp x4, x5, [x29, #CPU_XREG_OFFSET(4)] + ldp x6, x7, [x29, #CPU_XREG_OFFSET(6)] + ldp x8, x9, [x29, #CPU_XREG_OFFSET(8)] + ldp x10, x11, [x29, #CPU_XREG_OFFSET(10)] + ldp x12, x13, [x29, #CPU_XREG_OFFSET(12)] + ldp x14, x15, [x29, #CPU_XREG_OFFSET(14)] + ldp x16, x17, [x29, #CPU_XREG_OFFSET(16)] + + // Restore guest regs x18-x29, lr + restore_callee_saved_regs x29 // Do not touch any register after this! eret @@ -114,7 +114,7 @@ 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 +123,8 @@ 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 -- 2.24.0.rc0.303.g954a862665-goog