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 0E66FC433F5 for ; Thu, 14 Oct 2021 03:15:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4576610A0 for ; Thu, 14 Oct 2021 03:15:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230026AbhJNDRF (ORCPT ); Wed, 13 Oct 2021 23:17:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230078AbhJNDRB (ORCPT ); Wed, 13 Oct 2021 23:17:01 -0400 Received: from mail-pl1-x634.google.com (mail-pl1-x634.google.com [IPv6:2607:f8b0:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 65439C061570 for ; Wed, 13 Oct 2021 20:14:56 -0700 (PDT) Received: by mail-pl1-x634.google.com with SMTP id x8so3175120plv.8 for ; Wed, 13 Oct 2021 20:14:56 -0700 (PDT) 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=ziZjbhk8BT0M+YtJUf8+KJKDTqKEqXLQXXRoPitasKI=; b=iWuXzaQWCMhU5v19VMpnlWp/Jum8n4MoQtULYxxJagOYZObl+bVS3CEPLl2rzQ6vVN eDVOVVEjcuu9jqTAUCmrq6SYz1tytz37yyjDnRXIhlY/r4QGegWVd7f6unmtKmxOYf9D aO5a+oJU8AlBuBcE3jibd6ItG4Hk4M1Q8gzFXdrGvgI1G+xArTZSVhrxkkG0NXDXhz8P xNwqNW0c9vM7JXMGH1L3OefuH8/opsYc9SYyvnVu+GFGz4Iwbj88Cq3x51w9pDKxQzG5 goZ0hDwJgNPfmrw0Q9lQGZD1ChQ4myvSogoV5jze0Yrp4aJ9jg1fiBhcgXvAsnaNclTN m0Fw== 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=ziZjbhk8BT0M+YtJUf8+KJKDTqKEqXLQXXRoPitasKI=; b=WIwit72o742khE++ZbOOJDiuviH46lW0Im3xVb42VDcxhc6DNE0lBb/SHxAXF6M+Cl UVyKbmjWhNtDW0EqUmtAtTcDPcowzDNC9rh77Fbnai0xh6u7sZBUEt/i9EVYb0hMpsgc bmDCt8u1FKOZv+Hgp8/ACG4XV/Rw8/jQZbkzLIUWNpren9dUbjkHg9CM5QqlHZw/nT+W nEeXXxUlMWerc+L7ZUjPbVt0GTBfK/Equ/o7xS85eZ1oQwTgDbpx9xwvCtYZZOy+8Ind HPusDzIrIwwChJOec9SGk6I4gk4eNfzEMC9omUjzjaEqnff8WYJUm+Lz3azS3OG2ZGXb c3eg== X-Gm-Message-State: AOAM532YfSp5SldLUo9jHzk9ArsNBmpAAJ9GxKHmrxjYJRZgOF7Ahty8 aXUyHcK6+E3RNtbnRwtm5Y/FxpRXjCw= X-Google-Smtp-Source: ABdhPJzpkAN6dWN7KdDgWgpczxPhJkz1xZ6tOUDKx0cpvgpNGxI52fkzkbxcU59sU3BkgbKJoHIyPg== X-Received: by 2002:a17:902:8494:b0:13b:9365:6f12 with SMTP id c20-20020a170902849400b0013b93656f12mr2783213plo.19.1634181295802; Wed, 13 Oct 2021 20:14:55 -0700 (PDT) Received: from localhost ([198.11.178.15]) by smtp.gmail.com with ESMTPSA id k22sm7642008pji.2.2021.10.13.20.14.54 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 13 Oct 2021 20:14:55 -0700 (PDT) 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, Boris Ostrovsky , Andy Lutomirski , Ingo Molnar , Borislav Petkov , Stefano Stabellini Subject: [PATCH V3 04/49] x86/xen: Add xenpv_restore_regs_and_return_to_usermode() Date: Thu, 14 Oct 2021 11:13:27 +0800 Message-Id: <20211014031413.14471-5-jiangshanlai@gmail.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20211014031413.14471-1-jiangshanlai@gmail.com> References: <20211014031413.14471-1-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 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> Cc: Boris Ostrovsky Signed-off-by: Lai Jiangshan --- arch/x86/entry/entry_64.S | 9 ++++++--- arch/x86/entry/entry_64_compat.S | 7 ++++--- arch/x86/xen/xen-asm.S | 27 +++++++++++++++++++++++++++ 3 files changed, 37 insertions(+), 6 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 9d468c8877e2..0dde5a253dda 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -119,7 +119,7 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe, SYM_L_GLOBAL) * In the Xen PV case we must use iret anyway. */ - ALTERNATIVE "", "jmp swapgs_restore_regs_and_return_to_usermode", \ + ALTERNATIVE "", "jmp xenpv_restore_regs_and_return_to_usermode", \ X86_FEATURE_XENPV movq RCX(%rsp), %rcx @@ -286,7 +286,8 @@ SYM_CODE_START(ret_from_fork) UNWIND_HINT_REGS movq %rsp, %rdi call syscall_exit_to_user_mode /* returns with IRQs disabled */ - jmp swapgs_restore_regs_and_return_to_usermode + ALTERNATIVE "jmp swapgs_restore_regs_and_return_to_usermode", \ + "jmp xenpv_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV 1: /* kernel thread */ @@ -566,6 +567,7 @@ __irqentry_text_start: __irqentry_text_end: SYM_CODE_START_LOCAL(common_interrupt_return) +SYM_INNER_LABEL(xenpv_restore_regs_and_return_to_usermode, SYM_L_WEAK) /* placeholder */ SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL) #ifdef CONFIG_DEBUG_ENTRY /* Assert that pt_regs indicates user mode. */ @@ -1055,7 +1057,8 @@ SYM_CODE_START_LOCAL(error_return) DEBUG_ENTRY_ASSERT_IRQS_OFF testb $3, CS(%rsp) jz restore_regs_and_return_to_kernel - jmp swapgs_restore_regs_and_return_to_usermode + ALTERNATIVE "jmp swapgs_restore_regs_and_return_to_usermode", \ + "jmp xenpv_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV SYM_CODE_END(error_return) /* diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 0051cf5c792d..2a4d9532dfd5 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -139,7 +139,7 @@ SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL) call do_SYSENTER_32 /* XEN PV guests always use IRET path */ ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \ - "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV + "jmp xenpv_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV jmp sysret32_from_system_call .Lsysenter_fix_flags: @@ -256,7 +256,7 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_after_hwframe, SYM_L_GLOBAL) call do_fast_syscall_32 /* XEN PV guests always use IRET path */ ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \ - "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV + "jmp xenpv_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV /* Opportunistic SYSRET */ sysret32_from_system_call: @@ -411,5 +411,6 @@ SYM_CODE_START(entry_INT80_compat) movq %rsp, %rdi call do_int80_syscall_32 - jmp swapgs_restore_regs_and_return_to_usermode + ALTERNATIVE "jmp swapgs_restore_regs_and_return_to_usermode", \ + "jmp xenpv_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV SYM_CODE_END(entry_INT80_compat) diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S index 220dd9678494..032be1bab113 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 +193,32 @@ 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 +#ifdef CONFIG_DEBUG_ENTRY + /* Assert that pt_regs indicates user mode. */ + testb $3, CS(%rsp) + jnz 1f + ud2 +1: +#endif + 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