Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752090AbaGFTYp (ORCPT ); Sun, 6 Jul 2014 15:24:45 -0400 Received: from mail-vc0-f171.google.com ([209.85.220.171]:46585 "EHLO mail-vc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751933AbaGFTYn (ORCPT ); Sun, 6 Jul 2014 15:24:43 -0400 MIME-Version: 1.0 In-Reply-To: References: Date: Sun, 6 Jul 2014 12:24:42 -0700 X-Google-Sender-Auth: ytALZ54MlWQEDjidq1dg7MW5H4g Message-ID: Subject: Re: [GIT PULL] bug fix for devicetree memory parsing From: Linus Torvalds To: Grant Likely Cc: Rob Herring , Laura Abbott , "devicetree@vger.kernel.org" , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jul 6, 2014 at 2:37 AM, Grant Likely wrote: > > Can you pull this bug fix into your tree please? I took it, but I think both your explanation and the patch itself is actually crap. It may fix the issue, but it's seriously confused. Your explanation says that it's a 32-bit platform issue. No it's not. Most 32-bit configurations still have a 64-bit phys_addr_t (ie PAE/LPAE etc). And the code is crap, because it uses ULONG_MAX etc in ways that simply make no f*cking sense. And why does it care about sizeof? Why does the code not just do something like #define MAX_PHYS_ADDR ((phys_addr_t) ~0) and then do if (base > MAX_PHYS_ADDR || base + size > MAX_PHYS_ADDR) ... and be done with it? All those sizeof tests are completely pointless. If it turns out that phys_addr_t is the same size as u64, then the tests will never be true, and the compiler will happily optimize them away. So I think this fixes a problem, but it's all ugly as hell. I ended up pulling it because I'm lazy and don't have a machine to test a proper fix on anyway, but I hope this can get cleaned up. And more importantly, I hope maintainers will spend a bit more time thinking about things like this. It's not just that the code is unnecessarily complex, it's WRONG. Comparing things to "ULONG_MAX" makes absolutely zero sense, since "ULONG_MAX" has nothing to do with anything. It's just stupid and misleading, and it just so happens to work by random luck because it so *happens* that phys_addr_t is smaller than "u64" only when ULONG_MAX happens to be the same size. But even that is not guaranteed (ie some stupid broken architecture might have a 32-bit physical address space despite having a 64-bit "long") Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/