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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D2F1C48286 for ; Sun, 4 Feb 2024 11:03:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C977E6B0075; Sun, 4 Feb 2024 06:03:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C48166B007D; Sun, 4 Feb 2024 06:03:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AE87A6B007E; Sun, 4 Feb 2024 06:03:21 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 9B98B6B0075 for ; Sun, 4 Feb 2024 06:03:21 -0500 (EST) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 43ECE806FA for ; Sun, 4 Feb 2024 11:03:21 +0000 (UTC) X-FDA: 81753835002.23.FE6FEAE Received: from out4-smtp.messagingengine.com (out4-smtp.messagingengine.com [66.111.4.28]) by imf01.hostedemail.com (Postfix) with ESMTP id EC7484001C for ; Sun, 4 Feb 2024 11:03:18 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=flygoat.com header.s=fm1 header.b=klD336ts; dkim=pass header.d=messagingengine.com header.s=fm3 header.b="J gyI4Lq"; dmarc=pass (policy=none) header.from=flygoat.com; spf=pass (imf01.hostedemail.com: domain of jiaxun.yang@flygoat.com designates 66.111.4.28 as permitted sender) smtp.mailfrom=jiaxun.yang@flygoat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707044599; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Bf+fUOrYXcGEM/eDTspqcwbDeCrIad7HJCkL0vJjXLo=; b=offExRwzSl0WO7ZSATRPMmZnWyt8kY7DyZ0rmEYiyWBcuGHNzxPt5HME+OI2mo0AZfQ2Gg mu/AUPYKU4WxcQNSOAssnssQi0IzFf22XamBR5zOU+ddCNvzg/gtDMPPdOv4uVysUzRpJ/ fdNV2CmNLgN9ypoojfzwJxRrFFfmX6o= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=flygoat.com header.s=fm1 header.b=klD336ts; dkim=pass header.d=messagingengine.com header.s=fm3 header.b="J gyI4Lq"; dmarc=pass (policy=none) header.from=flygoat.com; spf=pass (imf01.hostedemail.com: domain of jiaxun.yang@flygoat.com designates 66.111.4.28 as permitted sender) smtp.mailfrom=jiaxun.yang@flygoat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1707044599; a=rsa-sha256; cv=none; b=j1tWRlwsAZXh+P/GNXef/ai16HwOfK5B426JAlyX70Bv0hEP1JbydZ8HmauIuSurFhqQH6 zFApvQeqCAjstSQZrEOj2Go42oiR/MakYYE/GyZGrAarzfmZ5Hd4sxY8Vn86hNq5fKbisT OKwBVNnQf1xwUuz4+c9VkOAQpRSnb1o= Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.nyi.internal (Postfix) with ESMTP id 31F905C00D1; Sun, 4 Feb 2024 06:03:18 -0500 (EST) Received: from mailfrontend2 ([10.202.2.163]) by compute3.internal (MEProxy); Sun, 04 Feb 2024 06:03:18 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=flygoat.com; h= cc:cc:content-transfer-encoding:content-type:content-type:date :date:from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to; s=fm1; t=1707044598; x=1707130998; bh=Bf+fUOrYXcGEM/eDTspqcwbDeCrIad7HJCkL0vJjXLo=; b= klD336tsM1X2o9/VFc1F2tiyrPMCN8vuP1BjytGFIGBJ2Rxb6lHcG6Me/Ha3i3Uh S+nERwVD4tqcNLb6cHAY9q4XCdA3LV7MMa2d4ELjiej+BZZaN/NgNaBo1CS0/PWo zc23jK3N5jqKT06eN35uWiOsqGNGOmW87/mQEne68vI9D7wjsYWy6JkeYnYk8yR/ vSOsLLd8m5Sr9il4Sdh4K/RG2/BZ0U9545PTRgKJlOtQwkhQDEVdt6OF9/1BvRqg FCpLP+9017MxqjF81tLyXFsCSNnmY47CmuR4e9FKfanzOdJ7Aa6hfLqX408qPDZv M/kipRaZCnX85eXc5Wkt/Q== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:content-type:date:date:feedback-id:feedback-id :from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to:x-me-proxy:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm3; t=1707044598; x= 1707130998; bh=Bf+fUOrYXcGEM/eDTspqcwbDeCrIad7HJCkL0vJjXLo=; b=J gyI4Lqb8jFaFM6HQMVA+uf8nSiSvbsykpqRFok0ht0Nz1lM48osxHhH+Jdjmk3Es +iz/gr39XspwzhpwifTFJcL6Ki4Y/HXAmT6SVzPEQjvWqDuZtrJvpnr4jJVc8aIL 7MB7PHU9WmcbzB3WdAdsIj3KeIlw10sNsn3zTcZnRpxGGwYpn9iyQBrsMAL3q53E vTclfAnK+diImUUk5L6rZV0gioei3wO5lP6i7gPq87Pcd9l6GpBRMn7OObC2tcu8 LZ4vp0Wf4jEUVe6V4fHID9Q1hX7xsTIcHYR2iFJKaZru6jaQxjzHClqIpT92kEX5 0JhLy2Lqfz6NSMIhgU4Tw== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvkedrfedukedgvdefucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepkfffgggfuffvvehfhfgjtgfgsehtkeertddtvdejnecuhfhrohhmpeflihgr gihunhcujggrnhhguceojhhirgiguhhnrdihrghnghesfhhlhihgohgrthdrtghomheqne cuggftrfgrthhtvghrnhepleeuffehheegleeuvdelgffhueekjeetueevuefhffdtgfeu hfeggfeukefffedtnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilh hfrhhomhepjhhirgiguhhnrdihrghnghesfhhlhihgohgrthdrtghomh X-ME-Proxy: Feedback-ID: ifd894703:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Sun, 4 Feb 2024 06:03:16 -0500 (EST) Message-ID: <716af17c-136b-4852-86ce-a23bafe34fbb@flygoat.com> Date: Sun, 4 Feb 2024 11:03:15 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/3] Handle delay slot for extable lookup Content-Language: en-US To: Linus Torvalds Cc: Oleg Nesterov , Thomas Bogendoerfer , Andrew Morton , Ben Hutchings , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, Xi Ruoyao References: <20240202-exception_ip-v2-0-e6894d5ce705@flygoat.com> From: Jiaxun Yang Autocrypt: addr=jiaxun.yang@flygoat.com; keydata= xsFNBFnp/kwBEADEHKlSYJNLpFE1HPHfvsxjggAIK3ZtHTj5iLuRkEHDPiyyiLtmIgimmD3+ XN/uu2k1FFbrYiYgMjpGCXeRtdCLqkd+g9V4kYMlgi4MPHLt3XEuHcoKD1Yd2qYPT/OiQeGM 6bPtGUZlgfOpze1XuqHQ2VMWATL+kLYzk6FUUL715t8J5J9TgZBvSy8zc6gvpp3awsCwjFSv X3fiPMTC2dIiiMh4rKQKGboI1c7svgu6blHpy/Q5pXlEVqfLc7tFTGnvUp95jsK639GD8Ht3 0fSBxHGrTslrT775Aqi+1IsbJKBOmxIuU9eUGBUaZ00beGE09ovxiz2n2JKXKKZklNqhzifb 6uyVCOKdckR8uGqzRuohxDS7vlDZfFD5Z5OhplFY/9q+2IjCrWMmbHGSWYs9VV52XGM+wiEG sM5bup03N2q1kDXUWJ+zNNYowuOJKN9uxF3jBjdXSDi3uJu/ZUL/mBqI58SkHq5NTaHypRoE 5BxVmgDMCGQe93adKHUNmt4HK28R506S7019+umg1bq5vA/ncmh/J2k8MFGPXqO8t1xVI2O5 qrRheRKu1oST46ZJ7vKET1UwgcXTZ1iwqFlA26/iKxXoL7R7/AqWrapokEsUzRblGcutGZ/b 4lJVOxxAWaRcajpWvwqscI2mUF++O7DxYbhOJ/EFY2rv0i6+/QARAQABzSVKaWF4dW4gWWFu ZyA8amlheHVuLnlhbmdAZmx5Z29hdC5jb20+wsGRBBMBCAA7AhsjAh4BAheABQsJCAcCBhUK CQgLAgQWAgMBFiEEmAN5vv6/v0d+oE75wRGUkHP8D2cFAmKcjj8CGQEACgkQwRGUkHP8D2fx LxAAuNjknjfMBXIwEDpY+L2KMMU4V5rvTBATQ0dHZZzTlmTJuEduj/YdlVo0uTClRr9qkfEr Nfdr/YIS6BN6Am1x6nF2PAqHu/MkTNNFSAFiABh35hcm032jhrZVqLgAPLeydwQguIR8KXQB pP6S/jL3c7mUvVkoYy2g5PE1eH1MPeBwkg/r/ib9qNJSTuJH3SXnfZ4zoynvf3ipqnHsn2Sa 90Ta0Bux6ZgXIVlTL+LRDU88LISTpjBITyzn5F6fNEArxNDQFm4yrbPNbpWJXml50AWqsywp q9jRpu9Ly4qX2szkruJ/EnnAuS/FbEd4Agx2KZFb6LxxGAr4useXn6vab9p1bwRVBzfiXzqR WeTRAqwmJtdvzyo3tpkLmNC/jC3UsjqgfyBtiDSQzq0pSu7baOjvCGiRgeDCRSWq/T3HGZug 02QAi0Wwt/k5DX7jJS4Z5AAkfimXG3gq2nhiA6R995bYRyO8nIa+jmkMlYRFkwWdead3i/a0 zrtUyfZnIyWxUOsqHrfsN45rF2b0wHGpnFUfnR3Paa4my1uuwfp4BI6ZDVSVjz0oFBJ5y39A DCvFSpJkiJM/q71Erhyqn6c1weRnMok3hmG0rZ8RCSh5t7HllmyUUWe4OT97d5dhI7K/rnhc ze8vkrTNT6/fOvyPFqpSgYRDXGz2qboX/P6MG3zOOARlnqgjEgorBgEEAZdVAQUBAQdAUBqi bYcf0EGVya3wlwRABMwYsMimlsLEzvE4cKwoZzEDAQgHwsF2BBgBCAAgFiEEmAN5vv6/v0d+ oE75wRGUkHP8D2cFAmWeqCMCGwwACgkQwRGUkHP8D2dXlw/8CGKNXDloh1d7v/jDgcPPmlXd lQ4hssICgi6D+9aj3qYChIyuaNncRsUEOYvTmZoCHgQ6ymUUUBDuuog1KpuP3Ap8Pa3r5Tr6 TXtOl6Zi23ZWsrmthuYtJ8Yn5brxs6KQ5k4vCTkbF8ukue4Xl4O0RVlaIgJihJHZTfd9rUZy QugM8X98iLuUqYHCq2bAXHOq9h+mTLrhdy09dUalFyhOVejWMftULGfoXnRVz6OaHSBjTz5P HwZDAFChOUUR6vh31Lac2exTqtY/g+TjiUbXUPDEzN4mENACF/Aw+783v5CSEkSNYNxrCdt8 5+MRdhcj7y1wGfnSsKubHTOkBQJSanNr0cZZlPsJK0gxB2YTG6Nin13oX8mV7sAa3vBqqwfj ZtjNA+Up9IJY4Iz5upykUDAtCcvm82UnJoe5bMuoiyVccuqd5K/058AAxWv8fIvB4bSgmGMM aAN9l7GLyi4NhsKCCcAGSc2YAsxFrH6whVqY6JIF+08n1kur5ULrEKHpTTeffwajCgZPWpFc 7Mg2PDpoOwdpKLKlmIpyDexGVH0Lj/ycBL8ujDYZ2tA9HhEaO4dW6zsQyt1v6mZffpWK+ZXb Cs8oFeACbrtNFF0nhNI6LUPH3oaVOkUoRQUYDuX6mIc4VTwMA8EoZlueKEHfZIKrRf2QYbOZ HVO98ZmbMeg= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: EC7484001C X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: dbikgz785iostyzn3zizga1h7kx8au9n X-HE-Tag: 1707044598-133716 X-HE-Meta: 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 hOl2Jz6I tzauECKJ3ndeMfMA12ZjG1D9gcl1/l5bnhL0bZjOqhTdGr46vFcF3MufVblVC57WSPU+f60PUTLHLNbeoQH76bgjy5acSO6NVyeDdH8DAUgC7oRniKAbhg1ZjPqH+IyjwrbT2mCeDNoIZY9QLNDXUmYZ9Y4y2nUnUk5xFC+OXiuSe4QQ+VECCDg7B27VAnghzdAxsJ9Mgl0LFaliGgq5QoZ2/zV+I2HhWKzv0mrzHXht3JaNg1fbpoLdx5bdk2FQ6UyqczBR4R1YItiQ58kCOnaDj342gmULwwKaCG/PiQNC9f1qlqXGCsGzZ5oXrBrFO/6K4BVQ3/WDhdRc= 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: List-Subscribe: List-Unsubscribe: 在 2024/2/4 07:41, Linus Torvalds 写道: [...] > The thing is, the only reason for the code in > get_mmap_lock_carefully() is for kernel bugs. IOW, some kernel bug > with a wild pointer, and we do not want to deadlock on the mm > semaphore, we want to get back to the fault handler and it should > report an oops. > > ... and one of the "wild pointers" might in fact be the instruction > pointer, in case we've branched through a NULL function pointer or > similar. IOW, the exception *source* might be the instruction pointer > itself. Well this is the tricky part of my assumption. In `exception_epc()` `__isa_exception_epc()` stuff is only called if we are in delay slot. It is impossible for a invalid instruction_pointer to be considered as "in delay slot" by hardware. I'd agree that sounds fragile though. Thanks > > So I realy think that MIPS needs to have some kind of "safe kernel > exception pointer" helper. One that is guaranteed not to fault when > evaluating the exception pointer. > > Assuming the kernel itself is never built with MIPS16e instructions, > maybe that's a safe assumption thanks to the "get_isa16_mode()" check > of EPC. But all of this makes me nervous. > > Linus -- --- Jiaxun Yang