From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 461C36B0033 for ; Sun, 5 Nov 2017 07:54:56 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id 15so9271395pgc.16 for ; Sun, 05 Nov 2017 04:54:56 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id t67sor2824349pgb.205.2017.11.05.04.54.54 for (Google Transport Security); Sun, 05 Nov 2017 04:54:55 -0800 (PST) Date: Sun, 5 Nov 2017 23:54:43 +1100 From: Nicholas Piggin Subject: Re: POWER: Unexpected fault when writing to brk-allocated memory Message-ID: <20171105235443.045fb4b7@roar.ozlabs.ibm.com> In-Reply-To: <919a1cb5-c3b5-ddee-d6a6-0994c282ae84@redhat.com> References: <20171105231850.5e313e46@roar.ozlabs.ibm.com> <919a1cb5-c3b5-ddee-d6a6-0994c282ae84@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Florian Weimer Cc: "Aneesh Kumar K . V" , linuxppc-dev@lists.ozlabs.org, linux-mm On Sun, 5 Nov 2017 13:35:40 +0100 Florian Weimer wrote: > On 11/05/2017 01:18 PM, Nicholas Piggin wrote: > > > There was a recent change to move to 128TB address space by default, > > and option for 512TB addresses if explicitly requested. > > Do you have a commit hash for the introduction of 128TB by default? Thanks. I guess this one f6eedbba7a26 ("powerpc/mm/hash: Increase VA range to 128TB") > > > Your brk request asked for > 128TB which the kernel gave it, but the > > address limit in the paca that the SLB miss tests against was not > > updated to reflect the switch to 512TB address space. > > > > Why is your brk starting so high? Are you trying to test the > 128TB > > case, or maybe something is confused by the 64->128TB change? What's > > the strace look like if you run on a distro or <= 4.10 kernel? > > I think it is a consequence of running with an explicit loader > invocation. With that, the heap is placed above ld.so, which can be > quite high in the address space. > > I'm attaching two runs of cat, one executing directly as /bin/cat, and > one with /lib64/ld64.so.1 /bin/cat. > > Fortunately, this does *not* apply to PIE binaries (also attached). > However, explicit loader invocations are sometimes used in test suites > (not just for glibc), and these sporadic test failures are quite annoying. > > Do you still need the strace log? And if yes, of what exactly? Thanks, that should be quite helpful. I'll spend a bit more time to study it, I'll let you know if I need any other traces. > > > Something like the following patch may help if you could test. > > Okay, this will take some time. It's no rush, there will probably be a revision to come. Thanks, Nick -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org