From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vMVjm1M5kzDqBQ for ; Tue, 14 Feb 2017 03:04:27 +1100 (AEDT) Date: Mon, 13 Feb 2017 09:44:37 -0600 From: Segher Boessenkool To: Cyril Bur Cc: linuxppc-dev@lists.ozlabs.org, akshay.adiga@linux.vnet.ibm.com Subject: Re: [PATCH v2] powerpc: Blacklist GCC 5.4 6.1 and 6.2 Message-ID: <20170213154437.GP21840@gate.crashing.org> References: <20170213033536.8908-1-cyrilbur@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170213033536.8908-1-cyrilbur@gmail.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Cyril, On Mon, Feb 13, 2017 at 02:35:36PM +1100, Cyril Bur wrote: > A bug in the -02 optimisation of GCC 5.4 6.1 and 6.2 causes > setup_command_line() to not pass the correct first argument to strcpy > and therefore not actually copy the command_line. There is no such thing as an "-O2 optimisation". > At the time of writing GCC 5.4 is the most recent and is affected. GCC > 6.3 contains the backported fix, has been tested and appears safe to > use. 6.3 is (of course) the newer release; 5.4 is a maintenance release of a compiler that is a year older. > +# - gcc-5.4, 6.1, 6.2 don't copy the command_line around correctly > + echo -n '*** GCC-5.4 6.1 6.2 have a bad -O2 optimisation ' ; \ > + echo 'which will cause lost command_line options (at least).' ; \ Maybe something more like "GCC 5.4, 6.1, and 6.2 have a bug that results in a kernel that does not boot. Please use GCC 6.3 or later.". Please mention the GCC PR # somewhere in the code, too? Segher