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 B9E53C433FE for ; Sat, 8 Oct 2022 22:09:17 +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:MIME-Version:In-Reply-To:References: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=eDwMA4h0SThKbEmDdtTEF//zUvy20IMRc/Mz1uAQ7nA=; b=Mo5u1Dq4c6V5S4 WX5b3ZcQ4KldvZfamlwyfivZjJYDSrYq5aH9K7iQugc46wQOzNFgfW2Py7Q6eSyXCY8hHI2zvKY9i 3srJWAxJIpEz1Mt8zioPR87SReuhFUyyvzzuzCSdPJQi8eEBP/ZqgJ8xu8b5ogms5XE7zZCmccuhW ZxT8gMox92j0dtvSRg/niRWouyoJ51rhHe6mL1yKi229EB3EXHZuEtVVP7OB0vhKAI2lWPJQbhmPm h8oc/8kuJXnFD72bdlZVfBkG1Rb5Exz5eSExRpNghNfbbR0qS59IbJWqViopOEYCK1+Qpya46WZ5F inVWXkzpZw2DvpXv4PMg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ohI0K-00ELlg-IF; Sat, 08 Oct 2022 22:09:08 +0000 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ohI0G-00ELih-0M for linux-mtd@lists.infradead.org; Sat, 08 Oct 2022 22:09:07 +0000 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-98-KtAFQuLTPeKLVd871cru4Q-1; Sat, 08 Oct 2022 23:08:05 +0100 X-MC-Unique: KtAFQuLTPeKLVd871cru4Q-1 Received: from AcuMS.Aculab.com (10.202.163.4) by AcuMS.aculab.com (10.202.163.4) with Microsoft SMTP Server (TLS) id 15.0.1497.38; Sat, 8 Oct 2022 23:08:03 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.040; Sat, 8 Oct 2022 23:08:03 +0100 From: David Laight To: "'Jason A. Donenfeld'" , "linux-kernel@vger.kernel.org" , "patches@lists.linux.dev" CC: Andreas Noever , Andrew Morton , Andy Shevchenko , Borislav Petkov , "Catalin Marinas" , =?utf-8?B?Q2hyaXN0b3BoIELDtmhtd2FsZGVy?= , Christoph Hellwig , Christophe Leroy , Daniel Borkmann , Dave Airlie , Dave Hansen , "David S . Miller" , "Eric Dumazet" , Florian Westphal , "Greg Kroah-Hartman" , "H . Peter Anvin" , Heiko Carstens , Helge Deller , Herbert Xu , Huacai Chen , Hugh Dickins , Jakub Kicinski , "James E . J . Bottomley" , Jan Kara , Jason Gunthorpe , Jens Axboe , Johannes Berg , Jonathan Corbet , Jozsef Kadlecsik , KP Singh , Kees Cook , Marco Elver , Mauro Carvalho Chehab , "Michael Ellerman" , Pablo Neira Ayuso , "Paolo Abeni" , Peter Zijlstra , "Richard Weinberger" , Russell King , "Theodore Ts'o" , Thomas Bogendoerfer , "Thomas Gleixner" , Thomas Graf , Ulf Hansson , Vignesh Raghavendra , WANG Xuerui , Will Deacon , Yury Norov , "dri-devel@lists.freedesktop.org" , "kasan-dev@googlegroups.com" , "kernel-janitors@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-block@vger.kernel.org" , "linux-crypto@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-media@vger.kernel.org" , "linux-mips@vger.kernel.org" , "linux-mm@kvack.org" , "linux-mmc@vger.kernel.org" , "linux-mtd@lists.infradead.org" , "linux-nvme@lists.infradead.org" , "linux-parisc@vger.kernel.org" , "linux-rdma@vger.kernel.org" , "linux-s390@vger.kernel.org" , "linux-um@lists.infradead.org" , "linux-usb@vger.kernel.org" , "linux-wireless@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "loongarch@lists.linux.dev" , "netdev@vger.kernel.org" , "sparclinux@vger.kernel.org" , "x86@kernel.org" , Jan Kara Subject: RE: [PATCH v4 2/6] treewide: use prandom_u32_max() when possible Thread-Topic: [PATCH v4 2/6] treewide: use prandom_u32_max() when possible Thread-Index: AQHY2ncm2NigVNsUqkWyNH5TWnqFQK4FDn2g Date: Sat, 8 Oct 2022 22:08:03 +0000 Message-ID: <01fafe0e56554b1c9c934c458b93473a@AcuMS.aculab.com> References: <20221007180107.216067-1-Jason@zx2c4.com> <20221007180107.216067-3-Jason@zx2c4.com> In-Reply-To: <20221007180107.216067-3-Jason@zx2c4.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221008_150904_349383_AC69CD75 X-CRM114-Status: GOOD ( 11.87 ) 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 From: Jason A. Donenfeld > Sent: 07 October 2022 19:01 > > Rather than incurring a division or requesting too many random bytes for > the given range, use the prandom_u32_max() function, which only takes > the minimum required bytes from the RNG and avoids divisions. > ... > --- a/lib/cmdline_kunit.c > +++ b/lib/cmdline_kunit.c > @@ -76,7 +76,7 @@ static void cmdline_test_lead_int(struct kunit *test) > int rc = cmdline_test_values[i]; > int offset; > > - sprintf(in, "%u%s", prandom_u32_max(256), str); > + sprintf(in, "%u%s", get_random_int() % 256, str); > /* Only first '-' after the number will advance the pointer */ > offset = strlen(in) - strlen(str) + !!(rc == 2); > cmdline_do_one_test(test, in, rc, offset); > @@ -94,7 +94,7 @@ static void cmdline_test_tail_int(struct kunit *test) > int rc = strcmp(str, "") ? (strcmp(str, "-") ? 0 : 1) : 1; > int offset; > > - sprintf(in, "%s%u", str, prandom_u32_max(256)); > + sprintf(in, "%s%u", str, get_random_int() % 256); > /* > * Only first and leading '-' not followed by integer > * will advance the pointer. Something has gone backwards here.... And get_random_u8() looks a better fit. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/