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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F0E5CC433F5 for ; Fri, 26 Nov 2021 10:12:37 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.232494.403104 (Exim 4.92) (envelope-from ) id 1mqYDL-0006t8-4e; Fri, 26 Nov 2021 10:12:19 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 232494.403104; Fri, 26 Nov 2021 10:12:19 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mqYDL-0006t1-1W; Fri, 26 Nov 2021 10:12:19 +0000 Received: by outflank-mailman (input) for mailman id 232494; Fri, 26 Nov 2021 10:12:17 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mqYDJ-0006st-Ed for xen-devel@lists.xenproject.org; Fri, 26 Nov 2021 10:12:17 +0000 Received: from mail-pf1-x433.google.com (mail-pf1-x433.google.com [2607:f8b0:4864:20::433]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 537236c1-4ea1-11ec-9787-a32c541c8605; Fri, 26 Nov 2021 11:12:16 +0100 (CET) Received: by mail-pf1-x433.google.com with SMTP id o4so8443995pfp.13 for ; Fri, 26 Nov 2021 02:12:15 -0800 (PST) Received: from localhost ([47.251.3.230]) by smtp.gmail.com with ESMTPSA id j2sm3870184pgl.73.2021.11.26.02.12.12 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Nov 2021 02:12:12 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 537236c1-4ea1-11ec-9787-a32c541c8605 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=o/JsKbfMes+8HN/WC8BxQrxJb7eO4f1vtnbbvoObfIw=; b=qAEXRhJCQualuXUI/E9TTZKF+vyX2KzxEvmGfinCNMQN3bZc4v5qw3+auBqPTn+kKu M+3yBhQ9LskJvs7Q/3TRBzenI80zV6/EYs6sk1uLx9XviHrar+L9NvzCIJqtwm2S2GrH lWvF7UeRX4zY/2QoY7wT0yR/2sl3S08YxRA7654v7s6infsNz74W//YjCQgEHUuKhMrZ 2m17i10/Sx8RwyaFqN4DhtC4TweDXrlOyLXpYhFpPgupCUjLoWkzYGJm9z6TddPtex55 j44Gtoy91BW19/Bq4WUmCnpxueDztG3aTN7yG1DtiCT6i5jKAXHRemC2Bl7j2sJDrjrW rJJA== 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=o/JsKbfMes+8HN/WC8BxQrxJb7eO4f1vtnbbvoObfIw=; b=GyTPZhpanqKNrBII7bQJJFoNMKVV1n97nb+5yovNz1v/DvWwWaIoolSYpTH4/wqKsq jT54nFkZaoUiW3kbJQdB4cCgn8K7iYFyWW4nYXMg6KNFH3iwT1+xWAbX4rzHQuHfRo7r gclZPDi5IsxCHF10Bs9r5H+A9oVzH2c+5L7XGl0bf7ZxwO9Vq1bJHJ65rPU+ZZl2RHJB H34ABqhu4TyjTp7qVSAfaj2oFnaKpNxyFez68+8GxQWpZxmeZoRZ5tRUr9KcWDLLrCnX V2O9qFVAdmlmhE2aBQiLlb5SzgVr78Dim611IYsw703enOAs64UUBcgtJtaiC+k1rE0T L47w== X-Gm-Message-State: AOAM533hFivJfrNM6OHWQubZJJG6jX2QrJT2zSSJj71LhFUOe3askukU A+a/YEqgHJ3+Z2RNtNAmcmk= X-Google-Smtp-Source: ABdhPJwQkD5yFxnX+taigMIodM5mVwgcHezaHYIaCCLRC2t7bnJOlp6G7/Oyuib5tURhRHES5mL3XQ== X-Received: by 2002:a05:6a00:1412:b0:4a7:ec46:29d1 with SMTP id l18-20020a056a00141200b004a7ec4629d1mr12919164pfu.16.1637921533272; Fri, 26 Nov 2021 02:12:13 -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 V6 03/49] x86/xen: Add xenpv_restore_regs_and_return_to_usermode() Date: Fri, 26 Nov 2021 18:11:23 +0800 Message-Id: <20211126101209.8613-4-jiangshanlai@gmail.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20211126101209.8613-1-jiangshanlai@gmail.com> References: <20211126101209.8613-1-jiangshanlai@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 4967edded48d..68e697acefac 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