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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id v131si38191551pgb.452.2019.04.12.11.16.03 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 12 Apr 2019 11:16:03 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of peterz@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=TXtxbDYu; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=peterz@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=vLgYVDT49iGyhQ7eAaa1ouryxRYhUiXDgOprm8yEPCE=; b=TXtxbDYuMujQhLK+HaFsZkwEi ExxaqmfppeQtbOkWZPOZ2cCRPEV+S8sfIQnDJF5mi941nvZ00/tSkwtBibSXyg8MOvY6p0k6RpNOX lwozqoFRxl01U59Jze3IxOcOWGtOmBYKsB2T8WdmwPgOlUEXrO9SgyyR0u7KlZ7q854B9M4hg4v6e dLsdE9woWI/1TvbMWk5ksNt2u2XKJK813fNAW3KlIf+VJXfIBQ4iXaVZR18TkYS59DCcSIs66/F12 QFW2ldsE539CqlBznmHrmdT7CIG8YLL+WdItNlI19A1O5xBfyJUp7uq9AP/90+GBDJWL7uX3RHsb5 FVkbrZiiQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hF0iV-0003m7-Hz; Fri, 12 Apr 2019 18:15:59 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 69C5029B20C3F; Fri, 12 Apr 2019 20:15:57 +0200 (CEST) Date: Fri, 12 Apr 2019 20:15:57 +0200 From: Peter Zijlstra To: David Howells Cc: Linus Torvalds , kernel test robot , LKP , Linux List Kernel Mailing , Linux-MM , linux-arch , Ingo Molnar , Thomas Gleixner , Will Deacon , Andy Lutomirski , Nadav Amit Subject: Re: 1808d65b55 ("asm-generic/tlb: Remove arch_tlb*_mmu()"): BUG: KASAN: stack-out-of-bounds in __change_page_attr_set_clr Message-ID: <20190412181557.GC12232@hirez.programming.kicks-ass.net> References: <5cae03c4.iIPk2cWlfmzP0Zgy%lkp@intel.com> <20190411193906.GA12232@hirez.programming.kicks-ass.net> <20190411195424.GL14281@hirez.programming.kicks-ass.net> <20190411211348.GA8451@worktop.programming.kicks-ass.net> <20190412105633.GM14281@hirez.programming.kicks-ass.net> <5890.1555087830@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5890.1555087830@warthog.procyon.org.uk> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Apr 12, 2019 at 05:50:30PM +0100, David Howells wrote: > Linus Torvalds wrote: > > > We should never have stack alignment bigger than 16 bytes. And > > preferably not even that. > > At least one arch I know of (FRV) had instructions that could atomically > load/store register pairs or register quads, but they had to be pair- or > quad-aligned (ie. 8- or 16-byte), which made for more efficient code if you > could use them. > > I don't know whether any arch we currently support has features like this (I > know some have multi-reg load/stores, but they seem to require only > word-alignment). ARC (iirc) has u64 atomics with natural alignment requirements but alignof(u64)=4 due it being a 32bit arch. Which is awkward. ARMv7 can also do u64 ops when aligned right, but I forgot if they have proper alignment or not.