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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 1B30DC433F5 for ; Thu, 28 Apr 2022 12:13:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:References:CC:To:From:Subject:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=hUVJ7+cV9522fhoan0IMiXDL/K9wvkJNEHc0UhCi4uY=; b=MHN2H1Z7y2vrewSVlZEA+JTZdJ Pz3r3mi7j3rBXYlbd3Te9E9yy6sYdXwWp6umbMavL+f58g4Iq4sZt81CSQsUDgcxhBf7k2s49WafG MCLvvg7LyI+fjudeN2uFiIVaEI55dv504g7oBpkHDApws50oUO8AqmOA4zpVzyeA0JytXA0xlBbx+ cTnKU4+91rea5WolxpvJHKy9VYVgiJqukf7ZAFaiVrq2zHCHwelZAhYMMp+HpqrFfnUDLqXuREsT2 Ow0MDe9IG4bwGkdSnB/qLTwlB67b6MJURh5ClYMr1dGHPrjoMWKmWfrurrD8S4hNyaM0ht+/moyNY rTkuvyjA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nk30D-006jLM-3u; Thu, 28 Apr 2022 12:12:10 +0000 Received: from szxga01-in.huawei.com ([45.249.212.187]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nk2ys-006ido-MR for linux-arm-kernel@lists.infradead.org; Thu, 28 Apr 2022 12:10:48 +0000 Received: from dggpemm500022.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KpvZr427hzhYnK; Thu, 28 Apr 2022 20:10:28 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500022.china.huawei.com (7.185.36.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 28 Apr 2022 20:10:43 +0800 Received: from [10.174.178.55] (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 28 Apr 2022 20:10:42 +0800 Subject: Re: [PATCH v2] arm64: add the printing of tpidr_elx in __show_regs() From: "Leizhen (ThunderTown)" To: Will Deacon CC: Catalin Marinas , , , "James Morse" References: <20220316062408.1113-1-thunder.leizhen@huawei.com> <20220428102156.GA14123@willie-the-truck> <4c956c17-6e13-37a1-7da3-b2c8243c2c01@huawei.com> Message-ID: <367e3bda-1541-2f9c-5b63-9820f03041e6@huawei.com> Date: Thu, 28 Apr 2022 20:10:42 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220428_051047_138958_498A3E6F X-CRM114-Status: GOOD ( 19.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2022/4/28 20:03, Leizhen (ThunderTown) wrote: > > > On 2022/4/28 19:07, Leizhen (ThunderTown) wrote: >> >> >> On 2022/4/28 18:21, Will Deacon wrote: >>> On Wed, Mar 16, 2022 at 02:24:08PM +0800, Zhen Lei wrote: >>>> Commit 7158627686f0 ("arm64: percpu: implement optimised pcpu access >>>> using tpidr_el1") and commit 6d99b68933fb ("arm64: alternatives: use >>>> tpidr_el2 on VHE hosts") use tpidr_elx to cache my_cpu_offset to optimize >>>> pcpu access. However, when performing reverse execution based on the >>>> registers and the memory contents in kdump, this information is sometimes >>>> required if there is a pcpu access. >>>> >>>> Signed-off-by: Zhen Lei >>>> --- >>>> arch/arm64/kernel/process.c | 11 +++++++++++ >>>> 1 file changed, 11 insertions(+) >>>> >>>> v1 --> v2: >>>> Directly print the tpidr_elx register of the current exception level. >>>> Avoid coupling with the implementation of 'my_cpu_offset'. >>>> >>>> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c >>>> index 5369e649fa79ff8..738932e6fa4e947 100644 >>>> --- a/arch/arm64/kernel/process.c >>>> +++ b/arch/arm64/kernel/process.c >>>> @@ -216,6 +216,17 @@ void __show_regs(struct pt_regs *regs) >>>> show_regs_print_info(KERN_DEFAULT); >>>> print_pstate(regs); >>>> >>>> + switch (read_sysreg(CurrentEL)) { >>> >>> This should use is_kernel_in_hyp_mode() to detect if we're running at El2. > > static inline bool is_kernel_in_hyp_mode(void) > { > return read_sysreg(CurrentEL) == CurrentEL_EL2; > } > > I think it's more intuitive to use "switch (read_sysreg(CurrentEL))". > >>> >>>> + case CurrentEL_EL1: >>>> + printk("tpidr_el1 : %016llx\n", read_sysreg(TPIDR_EL1)); >>>> + break; >>>> + case CurrentEL_EL2: >>>> + printk("tpidr_el2 : %016llx\n", read_sysreg(TPIDR_EL2)); >>>> + break; >>>> + default: >>>> + break; >>>> + } >>> >>> I think this path can be triggered directly from usermode, so we really >>> shouldn't be printing raw kernel virtual addresses here. >> >> I run echo c > /proc/sysrq-trigger and didn't trigger this path, but maybe >> there's another way. Analysis from the other side, except for the instruction >> address, all generic registers r0-r31 is output as raw. There's also an >> opportunity to contain the instruction address. > > On second thought, there seemed to be nothing wrong with it. The user need > to have capable() first. Then the address of the perpcu memory is not static, Sorry, __my_cpu_offset is just an offset. > the memory is dynamically allocated, exposing it is no different than exposing sp. > >> >> So how about: >> + if (oops_in_progress) >> + printk("tpidr : %016lx\n", __my_cpu_offset); >> >>> >>> Will >>> . >>> >> > -- Regards, Zhen Lei _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel