Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757213AbcJSRpv (ORCPT ); Wed, 19 Oct 2016 13:45:51 -0400 Received: from mail-qt0-f178.google.com ([209.85.216.178]:33900 "EHLO mail-qt0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752883AbcJSRpu (ORCPT ); Wed, 19 Oct 2016 13:45:50 -0400 MIME-Version: 1.0 In-Reply-To: References: From: Dmitry Safonov <0x7f454c46@gmail.com> Date: Wed, 19 Oct 2016 20:45:29 +0300 Message-ID: Subject: Re: x32 is broken in 4.9-rc1 due to "x86/signal: Add SA_{X32,IA32}_ABI sa_flags" To: Mikulas Patocka Cc: Dmitry Safonov , Oleg Nesterov , linux-mm@kvack.org, Cyrill Gorcunov , Pavel Emelyanov , Thomas Gleixner , open 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 Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id u9JHjtRs019812 Content-Length: 2058 Lines: 53 2016-10-19 20:33 GMT+03:00 Mikulas Patocka : > > > On Wed, 19 Oct 2016, Mikulas Patocka wrote: > >> Hi >> >> In the kernel 4.9-rc1, the x32 support is seriously broken, a x32 process >> is killed with SIGKILL after returning from any signal handler. > > I should have said they are killed with SIGSEGV, not SIGKILL. > >> I use Debian sid x64-64 distribution with x32 architecture added from >> debian-ports. >> >> I bisected the bug and found out that it is caused by the patch >> 6846351052e685c2d1428e80ead2d7ca3d7ed913 ("x86/signal: Add >> SA_{X32,IA32}_ABI sa_flags"). >> >> example (strace of a process after receiving the SIGWINCH signal): >> >> epoll_wait(10, 0xef6890, 32, -1) = -1 EINTR (Interrupted system call) >> --- SIGWINCH {si_signo=SIGWINCH, si_code=SI_USER, si_pid=1772, si_uid=0} --- >> poll([{fd=4, events=POLLOUT}], 1, 0) = 1 ([{fd=4, revents=POLLOUT}]) >> write(4, "\0", 1) = 1 >> rt_sigreturn({mask=[INT QUIT ILL TRAP BUS KILL SEGV USR2 PIPE ALRM STKFLT TSTP TTOU URG XCPU XFSZ VTALRM IO PWR SYS RTMIN]}) = 0 >> --- SIGSEGV {si_signo=SIGSEGV, si_code=SI_KERNEL, si_addr=NULL} --- >> +++ killed by SIGSEGV +++ >> Neoprávnìný pøístup do pamìti (SIGSEGV) >> >> Mikulas > > BTW. when I take core dump of the killed x32 process, it shows: > > ELF Header: > Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 > Class: ELF32 > Data: 2's complement, little endian > Version: 1 (current) > OS/ABI: UNIX - System V > ABI Version: 0 > Type: CORE (Core file) > Machine: Intel 80386 > ^^^^^^^^^^^^^^^^^^^ > > So, the kernel somehow thinks that it is i386 process, not x32 process. A > core dump of a real x32 process shows "Class: ELF32, Machine: Advanced > Micro Devices X86-64". Thanks for catching, will check it today. -- Dmitry