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=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 EF40DC433E1 for ; Thu, 27 Aug 2020 10:42:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id ABF4E22B40 for ; Thu, 27 Aug 2020 10:42:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ABF4E22B40 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 503DA8E000A; Thu, 27 Aug 2020 06:42:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B26E8E0003; Thu, 27 Aug 2020 06:42:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 37C198E000A; Thu, 27 Aug 2020 06:42:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0242.hostedemail.com [216.40.44.242]) by kanga.kvack.org (Postfix) with ESMTP id 1AA088E0003 for ; Thu, 27 Aug 2020 06:42:51 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id D54FA181AEF15 for ; Thu, 27 Aug 2020 10:42:50 +0000 (UTC) X-FDA: 77196010500.18.ray61_3111c422706c Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin18.hostedemail.com (Postfix) with ESMTP id A5F78100EC679 for ; Thu, 27 Aug 2020 10:42:50 +0000 (UTC) X-HE-Tag: ray61_3111c422706c X-Filterd-Recvd-Size: 5922 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Thu, 27 Aug 2020 10:42:50 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 611E8101E; Thu, 27 Aug 2020 03:42:49 -0700 (PDT) Received: from [192.168.1.190] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0285D3F66B; Thu, 27 Aug 2020 03:42:45 -0700 (PDT) Subject: Re: [PATCH 21/35] arm64: mte: Add in-kernel tag fault handler To: Catalin Marinas , Andrey Konovalov Cc: Dmitry Vyukov , kasan-dev@googlegroups.com, Andrey Ryabinin , Alexander Potapenko , Marco Elver , Evgenii Stepanov , Elena Petrova , Branislav Rankov , Kevin Brodsky , Will Deacon , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20200827095429.GC29264@gaia> From: Vincenzo Frascino Message-ID: Date: Thu, 27 Aug 2020 11:44:58 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200827095429.GC29264@gaia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A5F78100EC679 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 8/27/20 10:54 AM, Catalin Marinas wrote: > On Fri, Aug 14, 2020 at 07:27:03PM +0200, Andrey Konovalov wrote: >> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c >> index 5e832b3387f1..c62c8ba85c0e 100644 >> --- a/arch/arm64/mm/fault.c >> +++ b/arch/arm64/mm/fault.c >> @@ -33,6 +33,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> #include >> @@ -222,6 +223,20 @@ int ptep_set_access_flags(struct vm_area_struct *vma, >> return 1; >> } >> >> +static bool is_el1_mte_sync_tag_check_fault(unsigned int esr) >> +{ >> + unsigned int ec = ESR_ELx_EC(esr); >> + unsigned int fsc = esr & ESR_ELx_FSC; >> + >> + if (ec != ESR_ELx_EC_DABT_CUR) >> + return false; >> + >> + if (fsc == ESR_ELx_FSC_MTE) >> + return true; >> + >> + return false; >> +} >> + >> static bool is_el1_instruction_abort(unsigned int esr) >> { >> return ESR_ELx_EC(esr) == ESR_ELx_EC_IABT_CUR; >> @@ -294,6 +309,18 @@ static void die_kernel_fault(const char *msg, unsigned long addr, >> do_exit(SIGKILL); >> } >> >> +static void report_tag_fault(unsigned long addr, unsigned int esr, >> + struct pt_regs *regs) >> +{ >> + bool is_write = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0; >> + >> + pr_alert("Memory Tagging Extension Fault in %pS\n", (void *)regs->pc); >> + pr_alert(" %s at address %lx\n", is_write ? "Write" : "Read", addr); >> + pr_alert(" Pointer tag: [%02x], memory tag: [%02x]\n", >> + mte_get_ptr_tag(addr), >> + mte_get_mem_tag((void *)addr)); >> +} >> + >> static void __do_kernel_fault(unsigned long addr, unsigned int esr, >> struct pt_regs *regs) >> { >> @@ -317,12 +344,16 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr, >> msg = "execute from non-executable memory"; >> else >> msg = "read from unreadable memory"; >> + } else if (is_el1_mte_sync_tag_check_fault(esr)) { >> + report_tag_fault(addr, esr, regs); >> + msg = "memory tagging extension fault"; > > IIUC, that's dead code. See my comment below on do_tag_check_fault(). > That's correct. This was useful with "panic_on_mte_fault" kernel command line parameter. Since it has now been replaced by a similar kasan feature, this code can be safely removed. >> } else if (addr < PAGE_SIZE) { >> msg = "NULL pointer dereference"; >> } else { >> msg = "paging request"; >> } >> >> + > > Unnecessary empty line. > Agree. >> die_kernel_fault(msg, addr, esr, regs); >> } >> >> @@ -658,10 +689,27 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs) >> return 0; >> } >> >> +static int do_tag_recovery(unsigned long addr, unsigned int esr, >> + struct pt_regs *regs) >> +{ >> + report_tag_fault(addr, esr, regs); >> + >> + /* Skip over the faulting instruction and continue: */ >> + arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE); > > Ooooh, do we expect the kernel to still behave correctly after this? I > thought the recovery means disabling tag checking altogether and > restarting the instruction rather than skipping over it. We only skip if > we emulated it. > I tried to dig it out but I am not sure why we need this as well. >> + >> + return 0; >> +} >> + >> + >> static int do_tag_check_fault(unsigned long addr, unsigned int esr, >> struct pt_regs *regs) >> { >> - do_bad_area(addr, esr, regs); >> + /* The tag check fault (TCF) is per TTBR */ >> + if (is_ttbr0_addr(addr)) >> + do_bad_area(addr, esr, regs); >> + else >> + do_tag_recovery(addr, esr, regs); > > So we never invoke __do_kernel_fault() for a synchronous tag check in > the kernel. What's with all the is_el1_mte_sync_tag_check_fault() check > above? > That's correct. This had a meaning with "panic_on_mte_fault" but since the feature has been replaced is_el1_mte_sync_tag_check_fault() is not useful anymore. -- Regards, Vincenzo