From patchwork Fri Jan 6 08:56:13 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Li, Xin3" X-Patchwork-Id: 13091184 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB9D1C54E76 for ; Fri, 6 Jan 2023 09:22:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233398AbjAFJWH (ORCPT ); Fri, 6 Jan 2023 04:22:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44038 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233100AbjAFJU0 (ORCPT ); Fri, 6 Jan 2023 04:20:26 -0500 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA2DF6B5DB; Fri, 6 Jan 2023 01:20:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1672996824; x=1704532824; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=JFgGgK1UiImaF1he4az5OO5OcUrrSSoji4V3Q7e0Ou0=; b=nOZP93T5VmUAaDuRrZD53Dcsfa6AidcQHAmTwOWR6eQhzZ4QvH/V2LCx syksxbwqe8e/qMKogB0ns3RAFSl/RIZz2acEk0TAzUg448kYJ5ZUyMk/S XX9Brsny05/e7v7fRH7Jvc206LtthaRhjufHhwQAVmorQPsUDk2E0YRKr CZLrDie5YSIyMO/C1dZynB7I85M0IQQ5lo/qAD317I6QS466W7x7uaX6x 11ADoyqG9s6Z8LWT5uqoQmrt4X4uPEn3VBPH2QNfmK7h4fg+q22egkNMI LvNX6AFKHf68IYCnSsev7ciHMObW+hgKvmHcRthluqHWptgHpCQuWlAC7 Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10581"; a="322511631" X-IronPort-AV: E=Sophos;i="5.96,304,1665471600"; d="scan'208";a="322511631" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jan 2023 01:20:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10581"; a="719139457" X-IronPort-AV: E=Sophos;i="5.96,304,1665471600"; d="scan'208";a="719139457" Received: from unknown (HELO fred..) ([172.25.112.68]) by fmsmga008.fm.intel.com with ESMTP; 06 Jan 2023 01:20:17 -0800 From: Xin Li To: linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org, andrew.cooper3@citrix.com, seanjc@google.com, pbonzini@redhat.com, ravi.v.shankar@intel.com Subject: [RFC PATCH v2 28/32] x86/fred: fixup fault on ERETU by jumping to fred_entrypoint_user Date: Fri, 6 Jan 2023 00:56:13 -0800 Message-Id: <20230106085617.17248-29-xin3.li@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230106085617.17248-1-xin3.li@intel.com> References: <20230106085617.17248-1-xin3.li@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org If the stack frame contains an invalid user context (e.g. due to invalid SS, a non-canonical RIP, etc.) the ERETU instruction will trap (#SS or #GP). From a Linux point of view, this really should be considered a user space failure, so use the standard fault fixup mechanism to intercept the fault, fix up the exception frame, and redirect execution to fred_entrypoint_user. The end result is that it appears just as if the hardware had taken the exception immediately after completing the transition to user space. Suggested-by: H. Peter Anvin (Intel) Signed-off-by: Xin Li --- arch/x86/entry/entry_64_fred.S | 8 +++++-- arch/x86/include/asm/extable_fixup_types.h | 4 +++- arch/x86/mm/extable.c | 28 ++++++++++++++++++++++ 3 files changed, 37 insertions(+), 3 deletions(-) diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S index 1fb765fd3871..027ef8f1e600 100644 --- a/arch/x86/entry/entry_64_fred.S +++ b/arch/x86/entry/entry_64_fred.S @@ -5,8 +5,10 @@ * The actual FRED entry points. */ #include -#include +#include #include +#include +#include #include #include "calling.h" @@ -38,7 +40,9 @@ SYM_CODE_START_NOALIGN(fred_entrypoint_user) call fred_entry_from_user SYM_INNER_LABEL(fred_exit_user, SYM_L_GLOBAL) FRED_EXIT - ERETU +1: ERETU + + _ASM_EXTABLE_TYPE(1b, fred_entrypoint_user, EX_TYPE_ERETU) SYM_CODE_END(fred_entrypoint_user) /* diff --git a/arch/x86/include/asm/extable_fixup_types.h b/arch/x86/include/asm/extable_fixup_types.h index 991e31cfde94..1585c798a02f 100644 --- a/arch/x86/include/asm/extable_fixup_types.h +++ b/arch/x86/include/asm/extable_fixup_types.h @@ -64,6 +64,8 @@ #define EX_TYPE_UCOPY_LEN4 (EX_TYPE_UCOPY_LEN | EX_DATA_IMM(4)) #define EX_TYPE_UCOPY_LEN8 (EX_TYPE_UCOPY_LEN | EX_DATA_IMM(8)) -#define EX_TYPE_ZEROPAD 20 /* longword load with zeropad on fault */ +#define EX_TYPE_ZEROPAD 20 /* longword load with zeropad on fault */ + +#define EX_TYPE_ERETU 21 #endif diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c index 60814e110a54..31542a2507ae 100644 --- a/arch/x86/mm/extable.c +++ b/arch/x86/mm/extable.c @@ -6,6 +6,7 @@ #include #include +#include #include #include #include @@ -195,6 +196,29 @@ static bool ex_handler_ucopy_len(const struct exception_table_entry *fixup, return ex_handler_uaccess(fixup, regs, trapnr); } +#ifdef CONFIG_X86_FRED +static bool ex_handler_eretu(const struct exception_table_entry *fixup, + struct pt_regs *regs, unsigned long error_code) +{ + struct pt_regs *uregs = (struct pt_regs *)(regs->sp - offsetof(struct pt_regs, ip)); + unsigned short ss = uregs->ss; + unsigned short cs = uregs->cs; + + fred_info(uregs)->edata = fred_event_data(regs); + uregs->ssl = regs->ssl; + uregs->ss = ss; + uregs->csl = regs->csl; + uregs->current_stack_level = 0; + uregs->cs = cs; + + /* Copy error code to uregs and adjust stack pointer accordingly */ + uregs->orig_ax = error_code; + regs->sp -= 8; + + return ex_handler_default(fixup, regs); +} +#endif + int ex_get_fixup_type(unsigned long ip) { const struct exception_table_entry *e = search_exception_tables(ip); @@ -272,6 +296,10 @@ int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code, return ex_handler_ucopy_len(e, regs, trapnr, reg, imm); case EX_TYPE_ZEROPAD: return ex_handler_zeropad(e, regs, fault_addr); +#ifdef CONFIG_X86_FRED + case EX_TYPE_ERETU: + return ex_handler_eretu(e, regs, error_code); +#endif } BUG(); }