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 1C8A0C433FE for ; Thu, 10 Nov 2022 01:54:57 +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:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=i37ruPVPGrH7iQXQbalpLwLpWQuscL5YwYp9n1L/F0E=; b=raRa7iU+3l0uU5 avZTSyCr4ZYfQDT1iE7ZqoepkB9wSC90fiv6fhciF5hymotT67ziKmfLo/3xZIkMHno3sphD19ZPp KqNjXPzDS92D52hSZL046vBiLt7OYLsziHFCPoADueJwd22QjrF+tUKlOfnE+4zXATeG9vy13vLaw eBA+RogbVSCensbjCzgQ13AvP5eoFY3FLEl/670wYHgVj1gTRFb8xHacW/StQ9qNR01i4Ou8JtNCI W7fE0o7X65T0LIfS3B31YaENEbOhAegB7Q1WorIQZZE7PxngJZGD/J7lbmhpxm5hONWgAFVdh7Eqw LPikvGJkXwuMVuDj7ONA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oswmC-001jhr-P1; Thu, 10 Nov 2022 01:54:44 +0000 Received: from fudo.makrotopia.org ([2a07:2ec0:3002::71]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oswlv-001jam-Rh for linux-mtd@lists.infradead.org; Thu, 10 Nov 2022 01:54:29 +0000 Received: from local by fudo.makrotopia.org with esmtpsa (TLS1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.94.2) (envelope-from ) id 1oswlW-0002Yx-Jg; Thu, 10 Nov 2022 02:54:02 +0100 Date: Thu, 10 Nov 2022 01:52:43 +0000 From: Daniel Golle To: Matthew Wilcox Cc: Jens Axboe , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Davidlohr Bueso , "Martin K. Petersen" , Chaitanya Kulkarni , Ming Lei , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-efi@vger.kernel.org Subject: Re: [PATCH v4 2/5] block: add partition parser for U-Boot uImage.FIT Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221109_175427_901571_7F393CF9 X-CRM114-Status: GOOD ( 28.57 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On Wed, Nov 09, 2022 at 05:21:01PM +0000, Matthew Wilcox wrote: > On Wed, Nov 09, 2022 at 02:36:11PM +0000, Daniel Golle wrote: > > On Wed, Nov 09, 2022 at 01:58:29PM +0000, Matthew Wilcox wrote: > > > ... actually, why can't you call read_part_sector() and avoid all of > > > this? > > > > I've tried that before and the problem is that read_part_sector() > > returns a pointer to one sector (typically 512 bytes) of data. > > And this pointer should not be accesses beyond sector boundaries, > > right? You'd have to call read_part_sector() again for the next > > sector. > > > > The FIT structure, however, usually exceeds the size of one sector, > > and having a continous memory area covering the structure as a whole > > is crucial for libfdt to do its job. > > > > I could, of course, use read_part_sector() to copy all sectors > > covering the FIT structure into a buffer, but that seemed strange > > given that read_part_sector() actually used read_mapping_page() > > (and now uses read_mapping_folio()) internally and then returns a > > pointer to the offset within the page/folio. So why not read it in one > > piece in first place instead of having it first split up to sectors > > by read_part_sector() just to then having to reassemble it into a > > continous buffer again. > > Are you guaranteed that it's "sufficiently" aligned on storage so > that it fits entirely within a single page? If not, you'll have > to copy it, vmap it, or fix libfdt to handle a segmented buffer. Yes, for the uImage.FIT to be usable for the partition parser it has to be page-aligned. There is a check which makes sure that this is the case: > + /* uImage.FIT should be aligned to page boundaries */ > + if (fit_start_sector % (1 << (PAGE_SHIFT - SECTOR_SHIFT))) > + return 0; In case of mtdblock or ubiblock devices, the image always starts at offset 0, so this is never a problem. In case of the image being stored in a GPT partition, one has to make sure that the start sector of the partition is page aligned, otherwise the above check will fail and the partition parser will bail out. ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/