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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2DC8C433EF for ; Wed, 10 Nov 2021 11:58:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8D446115A for ; Wed, 10 Nov 2021 11:58:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231547AbhKJMAz (ORCPT ); Wed, 10 Nov 2021 07:00:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231584AbhKJMAl (ORCPT ); Wed, 10 Nov 2021 07:00:41 -0500 Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C933C06127A for ; Wed, 10 Nov 2021 03:57:54 -0800 (PST) Received: by mail-pj1-x102e.google.com with SMTP id n15-20020a17090a160f00b001a75089daa3so1652177pja.1 for ; Wed, 10 Nov 2021 03:57:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=7gp55vNbAiMPJFZt1vvuRfVDBF8kbd0dyE3oVrC7LSs=; b=ErpuCwTPM/lAhllg01n0htQnpfjyhCsJ4Z/ygE8rrUDFG89OS/Z6ULi/yfQ5l83SYR ekv8ETDGrJjZzC7nCGROQepEj6colRUgxdsfFTqNnkgR2ZPDVBxL8xh66fuzKX5cShvN ZaHy/eUh/VJNLkeeKO+mQ2K9mzWExjacm4qxtX59L+qgue1LMg1KIK6KA3p/wAFPIAjo L+7YzOnJ8Y/+2UXpv9hojsf/YYi7itNaVK39H/vDlTSF+FglB5DD50JUhlAFjr+G/pJE oGOvcr+x1h6OkctFppsKXnxnul6dmzYcVWEIg/qoyiUIGtCUtr/UqqcE16vL2uzGDSVW 19Cw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=7gp55vNbAiMPJFZt1vvuRfVDBF8kbd0dyE3oVrC7LSs=; b=l9O9fU2OMchuiiPhR5X8Q+vSHlBVA8YfsF8yWM0xrAVsd9fTEiusYuLLm5ggnZxdFn 8RVseoeNeXgecaWjMp9pFg+wEXnm/r5nLpRGEHD8GCRtaU1mHttplTgzc1pDFeds8ctb 93UKW2kFtOW+/EdL6R7m7Q/vawgj5OpAidye4mZ6poQ+wB7dccg9Q/FklQoKWo+8Nz9x XMxE7jtcGYnRkIh35r0reJHvN6heJ2Ru+mp0RAZ2bvEMlUz5ISFTtQvMHo2ZzFyybbjb /2F4eZuDlQQzGUXHmNgVm5M19mwypfGbHbS594wSW9tnccu0xgPak3KouQyZ9O8IHmJF RRTA== X-Gm-Message-State: AOAM530Wh/aE6htRSjg6FDYm73tyueVppiDyt4PLNb+fDk464GldSnwe PnEu5g9yLaNxK8W8pD25CioSkkZTkc8= X-Google-Smtp-Source: ABdhPJw4orw2dz/h+6dMeylsEPNNBFO9JalnXgfoeA7xVTZjRqfO80WskbTNDh4CQU7WOIh36roALQ== X-Received: by 2002:a17:902:d28a:b0:142:61ce:ae4c with SMTP id t10-20020a170902d28a00b0014261ceae4cmr15090581plc.35.1636545473614; Wed, 10 Nov 2021 03:57:53 -0800 (PST) Received: from localhost ([198.11.178.15]) by smtp.gmail.com with ESMTPSA id pj12sm5597014pjb.51.2021.11.10.03.57.52 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Nov 2021 03:57:53 -0800 (PST) From: Lai Jiangshan To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, Lai Jiangshan , Jan Beulich , Thomas Gleixner , Juergen Gross , Peter Anvin , xen-devel@lists.xenproject.org, Andy Lutomirski , Ingo Molnar , Borislav Petkov , Dave Hansen , Boris Ostrovsky , Stefano Stabellini Subject: [PATCH V5 04/50] x86/xen: Add xenpv_restore_regs_and_return_to_usermode() Date: Wed, 10 Nov 2021 19:56:50 +0800 Message-Id: <20211110115736.3776-5-jiangshanlai@gmail.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20211110115736.3776-1-jiangshanlai@gmail.com> References: <20211110115736.3776-1-jiangshanlai@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan While in the native case, PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is the trampoline stack. But XEN pv doesn't use trampoline stack, so PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is also the kernel stack. Hence source and destination stacks are identical in that case, which means reusing swapgs_restore_regs_and_return_to_usermode() in XEN pv would cause %rsp to move up to the top of the kernel stack and leave the IRET frame below %rsp, which is dangerous to be corrupted if #NMI / #MC hit as either of these events occurring in the middle of the stack pushing would clobber data on the (original) stack. And, when XEN pv, swapgs_restore_regs_and_return_to_usermode() pushing the IRET frame on to the original address is useless and error-prone when there is any future attempt to modify the code. Fixes: 7f2590a110b8 ("x86/entry/64: Use a per-CPU trampoline stack for IDT entries") Cc: Jan Beulich Cc: Thomas Gleixner Cc: Juergen Gross Cc: Peter Anvin Cc: xen-devel@lists.xenproject.org> Reviewed-by: Boris Ostrovsky Signed-off-by: Lai Jiangshan --- arch/x86/entry/entry_64.S | 4 ++++ arch/x86/xen/xen-asm.S | 20 ++++++++++++++++++++ 2 files changed, 24 insertions(+) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 6189a0dc83ab..ebcc17e1d7f1 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -574,6 +574,10 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL) ud2 1: #endif +#ifdef CONFIG_XEN_PV + ALTERNATIVE "", "jmp xenpv_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV +#endif + POP_REGS pop_rdi=0 /* diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S index 220dd9678494..444d824775f6 100644 --- a/arch/x86/xen/xen-asm.S +++ b/arch/x86/xen/xen-asm.S @@ -20,6 +20,7 @@ #include #include +#include <../entry/calling.h> .pushsection .noinstr.text, "ax" /* @@ -192,6 +193,25 @@ SYM_CODE_START(xen_iret) jmp hypercall_iret SYM_CODE_END(xen_iret) +/* + * XEN pv doesn't use trampoline stack, PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is + * also the kernel stack. Reusing swapgs_restore_regs_and_return_to_usermode() + * in XEN pv would cause %rsp to move up to the top of the kernel stack and + * leave the IRET frame below %rsp, which is dangerous to be corrupted if #NMI + * interrupts. And swapgs_restore_regs_and_return_to_usermode() pushing the IRET + * frame at the same address is useless. + */ +SYM_CODE_START(xenpv_restore_regs_and_return_to_usermode) + UNWIND_HINT_REGS + POP_REGS + + /* stackleak_erase() can work safely on the kernel stack. */ + STACKLEAK_ERASE_NOCLOBBER + + addq $8, %rsp /* skip regs->orig_ax */ + jmp xen_iret +SYM_CODE_END(xenpv_restore_regs_and_return_to_usermode) + /* * Xen handles syscall callbacks much like ordinary exceptions, which * means we have: -- 2.19.1.6.gb485710b