From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755365AbbATQpT (ORCPT ); Tue, 20 Jan 2015 11:45:19 -0500 Received: from bhuna.collabora.co.uk ([93.93.135.160]:60975 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753693AbbATQpP (ORCPT ); Tue, 20 Jan 2015 11:45:15 -0500 Message-ID: <54BE8615.7070708@collabora.co.uk> Date: Tue, 20 Jan 2015 17:45:09 +0100 From: Javier Martinez Canillas User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.2.0 MIME-Version: 1.0 To: Lee Jones CC: Olof Johansson , Doug Anderson , Bill Richardson , Simon Glass , Gwendal Grignou , Jonathan Corbet , linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RESEND v2 2/7] mfd: cros_ec: Add char dev and virtual dev pointers References: <1420205572-2640-1-git-send-email-javier.martinez@collabora.co.uk> <1420205572-2640-3-git-send-email-javier.martinez@collabora.co.uk> <20150120075011.GS21886@x1> <54BE770D.6030806@collabora.co.uk> <20150120163622.GD30656@x1> In-Reply-To: <20150120163622.GD30656@x1> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Lee, On 01/20/2015 05:36 PM, Lee Jones wrote: >> > >> > Is this safe? Are you sure it's okay to provide an interface from >> > userspace to read (kernel?) memory? >> > >> >> This interface is not to read any kernel memory but only the memory mapped >> I/O region for the Low Pin Count (LPC) bus. So user-space only can choose >> and offset and a number of bytes using the CROS_EC_DEV_IOCRDMEM ioctl cmd >> which uses the following structure as argument: >> >> /* >> * @offset: within EC_LPC_ADDR_MEMMAP region >> * @bytes: number of bytes to read. zero means "read a string" (including '\0') >> * (at most only EC_MEMMAP_SIZE bytes can be read) >> * @buffer: where to store the result >> * ioctl returns the number of bytes read, negative on error >> */ >> struct cros_ec_readmem { >> uint32_t offset; >> uint32_t bytes; >> uint8_t buffer[EC_MEMMAP_SIZE]; >> }; >> >> The cros_ec_lpc_readmem() handler that the function pointer is set only >> reads bytes from EC_LPC_ADDR_MEMMAP + offset if offset < EC_MEMMAP_SIZE >> and the data is copied to the user-space buffer from the structure passed >> as argument with copy_to_user(). >> >> So in that sense is similar to the spidev or i2c-dev interfaces that are >> used to access these buses from user-space. > > Very well. The purpose of my question was to be provocative and to > make you think about the interface. As long as you're sure it can't > be abused, then I'm happy. > Ok, thanks a lot. Does it mean I've your Acked-by for this patch too? Best regards, Javier