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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 73F90ECDE4B for ; Thu, 8 Nov 2018 14:15:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 414CA20827 for ; Thu, 8 Nov 2018 14:15:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 414CA20827 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.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 S1727246AbeKHXuw (ORCPT ); Thu, 8 Nov 2018 18:50:52 -0500 Received: from mail.bootlin.com ([62.4.15.54]:39694 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726359AbeKHXuw (ORCPT ); Thu, 8 Nov 2018 18:50:52 -0500 Received: by mail.bootlin.com (Postfix, from userid 110) id 613DD224CD; Thu, 8 Nov 2018 15:15:10 +0100 (CET) Received: from bbrezillon (aaubervilliers-681-1-30-49.w90-88.abo.wanadoo.fr [90.88.15.49]) by mail.bootlin.com (Postfix) with ESMTPSA id 199852073D; Thu, 8 Nov 2018 15:15:10 +0100 (CET) Date: Thu, 8 Nov 2018 15:15:09 +0100 From: Boris Brezillon To: Cc: , , , , , , , Subject: Re: [PATCH 3/7] mtd: spi-nor: add restriction for nmaps in smpt parser Message-ID: <20181108151509.364e3a85@bbrezillon> In-Reply-To: <86d16e39-15df-c12c-7bf3-25996db0c3a9@microchip.com> References: <20181108110653.21063-1-tudor.ambarus@microchip.com> <20181108110653.21063-4-tudor.ambarus@microchip.com> <20181108135447.36a0314c@bbrezillon> <86d16e39-15df-c12c-7bf3-25996db0c3a9@microchip.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 8 Nov 2018 13:58:45 +0000 wrote: > On 11/08/2018 02:54 PM, Boris Brezillon wrote: > > On Thu, 8 Nov 2018 11:07:11 +0000 > > wrote: > > > >> The map selector is limited to a maximum of 8 bits, allowing > >> for a maximum of 256 possible map configurations. The total > >> number of map configurations should be addressable by the > >> total number of bits described by the detection commands. > >> > >> For example: if there are five to eight possible sector map > >> configurations, at least three configuration detection commands > >> will be needed to extract three bits of configuration selection > >> information from the device in order to identify which configuration > >> is currently in use. > >> > >> Suggested-by: Boris Brezillon > > > > I don't remember suggesting this :-). > > I see this when you discussed with Yogesh: > > + for (nmaps = 0; i< smpt_len; nmaps++) { > + if(!(smpt[i] & SMPT_DESC_TYPE_MAP)) { > + i += 2; > + continue; > + } > + > + if(!map_id_is_valid) { > + if (nmaps) { > + ret = NULL; > + break; > + } > > If I understand correctly, you meant that if there are no detection commands, > and more than a configuration map, then return an error. Yes, because in this case we have no way to know what config is currently selected. > > This is correct in my opinion. What I did was to generalize this idea. If smtp > defines more maps than you can select using detection commands, return error. AFAICT you're no longer checking that map_id is valid (see below). > > + > + ret = smpt+i; > + } else if (map_id == SMPT_MAP_ID(smpt[i])) { > + ret = smpt+i; > + break; > + } > + > /* increment the table index to the next map */ > i += SMPT_MAP_REGION_COUNT(smpt[i]) + 1; > } > > > > >> Signed-off-by: Tudor Ambarus > >> --- > >> drivers/mtd/spi-nor/spi-nor.c | 15 +++++++++++++-- > >> 1 file changed, 13 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c > >> index 59dcedb08691..bd1866d714f2 100644 > >> --- a/drivers/mtd/spi-nor/spi-nor.c > >> +++ b/drivers/mtd/spi-nor/spi-nor.c > >> @@ -2868,7 +2868,7 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt, > >> const u32 *ret = NULL; > >> u32 addr; > >> int err; > >> - u8 i; > >> + u8 i, ncmds, nmaps; > >> u8 addr_width, read_opcode, read_dummy; > >> u8 read_data_mask, data_byte, map_id; > >> > >> @@ -2877,6 +2877,7 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt, > >> read_opcode = nor->read_opcode; > >> > >> map_id = 0; > >> + ncmds = 0; > >> /* Determine if there are any optional Detection Command Descriptors */ > >> for (i = 0; i < smpt_len; i += 2) { > >> if (smpt[i] & SMPT_DESC_TYPE_MAP) > >> @@ -2896,6 +2897,7 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt, > >> * Configuration that is currently in use. > >> */ > >> map_id = map_id << 1 | !!(data_byte & read_data_mask); > >> + ncmds++; > >> } > >> > >> /* > >> @@ -2905,7 +2907,16 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt, > >> * > >> * Find the matching configuration map. > >> */ > >> - while (i < smpt_len) { > >> + for (nmaps = 0; i < smpt_len; nmaps++) { > >> + /* > >> + * The map selector is limited to a maximum of 8 bits, allowing > >> + * for a maximum of 256 possible map configurations. The total > >> + * number of map configurations should be addressable by the > >> + * total number of bits described by the detection commands. > >> + */ > >> + if (ncmds && nmaps >= (1 << (ncmds + 1))) > >> + break; You're no longer checking that when ncmds == 0 nmaps has to be 1. So, say the chip exposed no smpt commands and has several maps defined, map_id will be 0 while it should have be "undefined". My version would return an error, but yours tries to find map_id 0. > >> + > > > > Maybe I missed something but it sounds like this change is just > > optimizing the SPMT parsing a bit, and to be honest, I'm not sure this > > is really needed. Most of the time, smpt_len will be rather small, so > > trying to bail out earlier is not bringing much perf improvements. > > It's rather a smtp validity check. I want to return an error if there are not > enough detection commands to identify the map id. You would have failed the same way without this validity check after a maximum of smpt_len iterations, right?