From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [195.92.253.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3wvVRy5SBJzDr0T for ; Sat, 24 Jun 2017 06:29:50 +1000 (AEST) Date: Fri, 23 Jun 2017 21:29:44 +0100 From: Al Viro To: Larry Finger Cc: LKML , Thorsten Leemhuis , linuxppc-dev@lists.ozlabs.org Subject: Re: Regression in kernel 4.12-rc1 for Powerpc 32 - bisected to commit 3448890c32c3 Message-ID: <20170623202943.GS10672@ZenIV.linux.org.uk> References: <69187aa4-611f-b08a-8d14-b8fa47b4c464@lwfinger.net> <1588557c-2706-0c0e-3387-4ae65d0b5790@lwfinger.net> <20170621212257.GN10672@ZenIV.linux.org.uk> <5f4b9fa4-262a-31b1-32ba-a2f6e789b3d6@lwfinger.net> <20170621213415.GO10672@ZenIV.linux.org.uk> <655d304e-e455-6e0c-56e1-f127653ea13c@lwfinger.net> <20170622141203.GP10672@ZenIV.linux.org.uk> <7bbd4c87-e8ff-5f83-8c4c-e205872083bf@lwfinger.net> <20170622192515.GQ10672@ZenIV.linux.org.uk> <2346c306-8e26-94cb-3c63-b866a7f4625d@lwfinger.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <2346c306-8e26-94cb-3c63-b866a7f4625d@lwfinger.net> Sender: Al Viro List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Jun 23, 2017 at 01:49:16PM -0500, Larry Finger wrote: > > BTW, could you try to check what happens if you kill the > > if (__builtin_constant_p(n) && (n <= 8)) > > bits in raw_copy_{to,from}_user()? The usefulness of those (in __copy_from_user() > > originally) had always been dubious and the things are simpler without them. > > If _that_ turns out to cure breakage, I would be very surprised, though. > > > Sorry I was gone so long. Installing jessie on this box resulted in a crash > on boot. Lubuntu 14.04 yielded a desktop with a functioning cursor, but > nothing else. Finally, Ubuntu 12.04 resulted in a working system. I hate > Unity, but I guess I'm stuck for now. Ho-hum... Jessie is 3.16, so whatever is crashing there, it's something different... Ubuntu 12.04 is what, 3.2? > I know how easy it is to screw up a long bisection by booting the wrong > kernel. To help that problem and to work around the yaconf/yboot nonsense on > the MAC, my /etc/yaconf has always had generic kernel stanzas with only > default, old, and original kernels mentioned. From there I use a local > script to finish a kernel installation by moving the default links to the > old ones and creating the new default links pointing to the current kernel. > With those long-tested scripts, I'm sure that I am booting the one I want. > > With the new installation, kernel 4.12-rc6 failed, as did 3448890c with the > backported 46f401c4 added. > > Replacing "if (__builtin_constant_p(n) && (n <= 8))" with "if (0)" had no effect. OK, that simplifies things a bit. Just to make sure we are on the same page: * f2ed8bebee69 + cherry-pick of 46f401c4 boots (Ubuntu 12.04 userland) * 3448890c32c3 + cherry-pick of 46f401c4 fails (Ubuntu 12.04 userland), ditto with removal of constant-size bits in raw_copy_..._user(). Failure appears to be on udev getting EFAULT on some syscalls. * straight Ubuntu 12.04 works * jessie crashes on boot. Could you post the boot logs of the first two?