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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 E2097C46475 for ; Thu, 25 Oct 2018 18:50:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 90BDE2082E for ; Thu, 25 Oct 2018 18:50:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DnMzCL4S" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 90BDE2082E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727650AbeJZDYp (ORCPT ); Thu, 25 Oct 2018 23:24:45 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:33737 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727350AbeJZDYp (ORCPT ); Thu, 25 Oct 2018 23:24:45 -0400 Received: by mail-pf1-f194.google.com with SMTP id a15-v6so811463pfn.0 for ; Thu, 25 Oct 2018 11:50:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:openpgp:autocrypt:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=CCcfAAa60Lij0HK6kPABjhvOUAflfQrx47AmMuzdjxc=; b=DnMzCL4SagvhfHVpD6SVmVjYcNLZ6QkDQyYr+ObYRkjw6dIA+Sfz97ooB4tK++pm0q Cz300rYEF5ObHh0aOon5W9GtWrRYgP21FbDYPbrxiXRM41dNcU6CwcYJwpmuCaQY22uV rNd60PV3AFFZtZben3V9DTwX9XhyqkUXFL98PQ51YdW9J+QmSMGyTkxKjKKe8hbPPTZE LlTWQ261r1lFPeWM+/L6P/roQgyluNmWbjAspkfqmpUsqYoonsVd+fxp4EV7qyzbSp88 00tPsDHtLnisi0qulBXwhP8wXNshFUfSUOEzLqQEUfkqZPC5pS0zbCLb/D+u1mVxmeZO ToYw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=CCcfAAa60Lij0HK6kPABjhvOUAflfQrx47AmMuzdjxc=; b=Qo4WnDDxIQLp48x5r1YetIsAzv0ciFLVlHZhVzwnO3CZgg6yWE9ALGyqGpCGol9uF9 e4EaUQvZ9+a6aLyZFaoZAH9w6fQBkP16KZ+9++ac9Q/eHE42EPTipyl9gEKSAYRjzcvS 4rgbmXxK3kRoBktuLu2spXv81p1IgE/rkuuousoG5t+xpc7p1GumQNLfSHfhUx/oGPgh +WYV42yWC4T9fhVgztu4rTEF8S+LwkJNcoRubrsYg/mDi3lrips6FBvE64NpzTYdsbkY LPtE6AHEyLek874DpcL8lyr4TAeFdeGOOM6ZTzhHDKXIWjkQlg+M5ctwmho8P/fMjEsT 09qg== X-Gm-Message-State: AGRZ1gKR/sSnJJkKC1X8GLXMJrJL6yxQA0qW/WA1FLqUdoBI9stjrc1y /+RlnkGWPHaWZenhYo5CG3apN8cb X-Google-Smtp-Source: AJdET5em0MawkWpHIAv1bP1zN9uxEXNXQ/8p3oOhzjGia4h2/ON+EQz+KlbhpwoZ5XV4kcdyVVFxYw== X-Received: by 2002:aa7:8195:: with SMTP id g21-v6mr359628pfi.71.1540493447088; Thu, 25 Oct 2018 11:50:47 -0700 (PDT) Received: from [10.67.49.121] ([192.19.223.250]) by smtp.googlemail.com with ESMTPSA id m5-v6sm6674289pfc.188.2018.10.25.11.50.44 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Oct 2018 11:50:46 -0700 (PDT) Subject: Re: [PATCH] ARM: mm: Facilitate debugging CONFIG_KUSER_HELPERS disabled To: "Eric W. Biederman" Cc: linux-arm-kernel@lists.infradead.org, andrew@lunn.ch, Russell King , Tony Lindgren , Souptick Joarder , open list References: <20181025180957.7900-1-f.fainelli@gmail.com> <87tvl9nas6.fsf@xmission.com> From: Florian Fainelli Openpgp: preference=signencrypt Autocrypt: addr=f.fainelli@gmail.com; prefer-encrypt=mutual; keydata= xsDiBEjPuBIRBACW9MxSJU9fvEOCTnRNqG/13rAGsj+vJqontvoDSNxRgmafP8d3nesnqPyR xGlkaOSDuu09rxuW+69Y2f1TzjFuGpBk4ysWOR85O2Nx8AJ6fYGCoeTbovrNlGT1M9obSFGQ X3IzRnWoqlfudjTO5TKoqkbOgpYqIo5n1QbEjCCwCwCg3DOH/4ug2AUUlcIT9/l3pGvoRJ0E AICDzi3l7pmC5IWn2n1mvP5247urtHFs/uusE827DDj3K8Upn2vYiOFMBhGsxAk6YKV6IP0d ZdWX6fqkJJlu9cSDvWtO1hXeHIfQIE/xcqvlRH783KrihLcsmnBqOiS6rJDO2x1eAgC8meAX SAgsrBhcgGl2Rl5gh/jkeA5ykwbxA/9u1eEuL70Qzt5APJmqVXR+kWvrqdBVPoUNy/tQ8mYc nzJJ63ng3tHhnwHXZOu8hL4nqwlYHRa9eeglXYhBqja4ZvIvCEqSmEukfivk+DlIgVoOAJbh qIWgvr3SIEuR6ayY3f5j0f2ejUMYlYYnKdiHXFlF9uXm1ELrb0YX4GMHz80nRmxvcmlhbiBG YWluZWxsaSA8Zi5mYWluZWxsaUBnbWFpbC5jb20+wmYEExECACYCGyMGCwkIBwMCBBUCCAME FgIDAQIeAQIXgAUCVF/S8QUJHlwd3wAKCRBhV5kVtWN2DvCVAJ4u4/bPF4P3jxb4qEY8I2gS 6hG0gACffNWlqJ2T4wSSn+3o7CCZNd7SLSDOw00ESM+4EhAQAL/o09boR9D3Vk1Tt7+gpYr3 WQ6hgYVON905q2ndEoA2J0dQxJNRw3snabHDDzQBAcqOvdi7YidfBVdKi0wxHhSuRBfuOppu pdXkb7zxuPQuSveCLqqZWRQ+Cc2QgF7SBqgznbe6Ngout5qXY5Dcagk9LqFNGhJQzUGHAsIs hap1f0B1PoUyUNeEInV98D8Xd/edM3mhO9nRpUXRK9Bvt4iEZUXGuVtZLT52nK6Wv2EZ1TiT OiqZlf1P+vxYLBx9eKmabPdm3yjalhY8yr1S1vL0gSA/C6W1o/TowdieF1rWN/MYHlkpyj9c Rpc281gAO0AP3V1G00YzBEdYyi0gaJbCEQnq8Vz1vDXFxHzyhgGz7umBsVKmYwZgA8DrrB0M oaP35wuGR3RJcaG30AnJpEDkBYHznI2apxdcuTPOHZyEilIRrBGzDwGtAhldzlBoBwE3Z3MY 31TOpACu1ZpNOMysZ6xiE35pWkwc0KYm4hJA5GFfmWSN6DniimW3pmdDIiw4Ifcx8b3mFrRO BbDIW13E51j9RjbO/nAaK9ndZ5LRO1B/8Fwat7bLzmsCiEXOJY7NNpIEpkoNoEUfCcZwmLrU +eOTPzaF6drw6ayewEi5yzPg3TAT6FV3oBsNg3xlwU0gPK3v6gYPX5w9+ovPZ1/qqNfOrbsE FRuiSVsZQ5s3AAMFD/9XjlnnVDh9GX/r/6hjmr4U9tEsM+VQXaVXqZuHKaSmojOLUCP/YVQo 7IiYaNssCS4FCPe4yrL4FJJfJAsbeyDykMN7wAnBcOkbZ9BPJPNCbqU6dowLOiy8AuTYQ48m vIyQ4Ijnb6GTrtxIUDQeOBNuQC/gyyx3nbL/lVlHbxr4tb6YkhkO6shjXhQh7nQb33FjGO4P WU11Nr9i/qoV8QCo12MQEo244RRA6VMud06y/E449rWZFSTwGqb0FS0seTcYNvxt8PB2izX+ HZA8SL54j479ubxhfuoTu5nXdtFYFj5Lj5x34LKPx7MpgAmj0H7SDhpFWF2FzcC1bjiW9mjW HaKaX23Awt97AqQZXegbfkJwX2Y53ufq8Np3e1542lh3/mpiGSilCsaTahEGrHK+lIusl6mz Joil+u3k01ofvJMK0ZdzGUZ/aPMZ16LofjFA+MNxWrZFrkYmiGdv+LG45zSlZyIvzSiG2lKy kuVag+IijCIom78P9jRtB1q1Q5lwZp2TLAJlz92DmFwBg1hyFzwDADjZ2nrDxKUiybXIgZp9 aU2d++ptEGCVJOfEW4qpWCCLPbOT7XBr+g/4H3qWbs3j/cDDq7LuVYIe+wchy/iXEJaQVeTC y5arMQorqTFWlEOgRA8OP47L9knl9i4xuR0euV6DChDrguup2aJVU8JPBBgRAgAPAhsMBQJU X9LxBQkeXB3fAAoJEGFXmRW1Y3YOj4UAn3nrFLPZekMeqX5aD/aq/dsbXSfyAKC45Go0YyxV HGuUuzv+GKZ6nsysJw== Message-ID: Date: Thu, 25 Oct 2018 11:50:43 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <87tvl9nas6.fsf@xmission.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/25/18 11:25 AM, Eric W. Biederman wrote: > Florian Fainelli writes: > >> Some software such as perf makes unconditional use of the special >> [vectors] page which is only provided when CONFIG_KUSER_HELPERS is >> enabled in the kernel. >> >> Facilitate the debugging of such situations by printing a debug message >> to the kernel log showing the task name and the faulting address. > > Can't someone trigger this segv deliberately and spam the kerne log? > Doesn't this need something like printk_ratelimit or something to ensure > this message only gets printed once? Yes, good point, thanks. -- Florian