From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754548AbaHEDTt (ORCPT ); Mon, 4 Aug 2014 23:19:49 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.228]:52755 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754352AbaHEDTW (ORCPT ); Mon, 4 Aug 2014 23:19:22 -0400 Date: Mon, 4 Aug 2014 23:19:18 -0400 From: Steven Rostedt To: Linus Torvalds Cc: Alexei Starovoitov , Michel =?ISO-8859-1?B?RORuemVy?= , Jakub Jelinek , Linux Kernel Mailing List , Debian GCC Maintainers , Debian Kernel Team Subject: Re: Random panic in load_balance() with 3.16-rc Message-ID: <20140804231918.36bd06f4@gandalf.local.home> In-Reply-To: References: <20140723182518.GD3935@laptop> <20140723184111.GG3935@laptop> <20140723190230.GH3935@laptop> <53D064C7.5050807@daenzer.net> <53D1B1EF.7030603@daenzer.net> <20140725035527.GA30108@pg-vmw-gw1> <20140725140237.GB32669@home.goodmis.org> X-Mailer: Claws Mail 3.10.1 (GTK+ 2.24.24; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="MP_/EY6f5mVpsPZ2v5Fdq=b68VA" X-RR-Connecting-IP: 107.14.168.118:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --MP_/EY6f5mVpsPZ2v5Fdq=b68VA Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Disposition: inline On Fri, 25 Jul 2014 11:29:06 -0700 Linus Torvalds wrote: > On Fri, Jul 25, 2014 at 7:02 AM, Steven Rostedt wrote: > > > > But wouldn't it be rather trivial to run a static analyzer on the final > > vmlinux to make sure there are no red zones? I mean, you would only need > > to read each function and check to make sure that the offset of rbp is > > within the change of rsp, wouldn't you? > > > > Almost seems like an objdump -rd into a perl script could do this. > > I'm sure it's possible, but it sounds potentially complicated. It's > not like the function prologue is fixed, and gcc will create code > (including conditional branches etc) before the whole frame setup if > there are simple things that can be done purely with the > callee-clobbered registers etc. > > Some simple pattern to make sure that the "sub $frame-size,%rsp" comes > before any accesses to (%rbp) (when frame pointers are enabled) > *might* work, but it might also end up missing things. > > You want to try? > I tried :-) Seems to stay clean with my x86_64 vmlinux build. I compiled the fair.s file and tested it and it got this: $ objump -dr fair.o | ./check-vmlinux.pl ERROR: : depth=-40 offset=136 at 4210 3572: 48 c7 85 78 ff ff ff movq $0x0,-0x88(%rbp) ERROR: : depth=8 offset=48 at 5734 4a79: 48 89 45 d0 mov %rax,-0x30(%rbp) ERROR: : depth=8 offset=48 at 5743 4a9c: 48 8b 75 d0 mov -0x30(%rbp),%rsi The sched_group_set_shares errors seem to be bogus as that is done after %rbp has been popped. Looks to be code that was jumped to from the main body. I could probably fix this by ignoring code after a pop of %rbp. Or make it more complex and be a bit smarter about branches. The script will read a file if passed by parameter, otherwise it reads standard input. e.g. $ objump -dr fair.o | ./check-vmlinux.pl or $ objdump -dr fair.o > /tmp/fair.dump $ ./check-vmlinux.pl /tmp/fair.dump produce the same. It's a little hacky, but I only spent a half hour at most on it. -- Steve --MP_/EY6f5mVpsPZ2v5Fdq=b68VA Content-Type: application/x-perl Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename=check-vmlinux.pl IyEvdXNyL2Jpbi9wZXJsIC13CiMgQ29weXJpZ2h0IFN0ZXZlbiBSb3N0ZWR0LCBSZWQgSGF0IElu Yy4KIwojIExpY2Vuc2VkIHVuZGVyIEdQTCB2MgoKbXkgJHN0YXJ0X3N0YXRlID0gMDsKbXkgJGZ1 bmN0aW9uX3N0YXRlID0gMTsKbXkgJGZyYW1lX3N0YXRlID0gMjsKCm15ICRzdGF0ZSA9IC0xOwpt eSAkZGVwdGggPSAwOwpteSAkZnVuYzsKCmlmICgkI0FSR1YgPj0gMCkgewogICAgb3BlbiBJTiwg JEFSR1ZbMF0gb3IgZGllICJDYW4ndCBvcGVuICRBUkdWWzBdXG4iOwogICAgY2xvc2UgU1RESU47 CiAgICAqU1RESU4gPSAqSU47Cn0KCm15ICRlcnIgPSAwOwoKc3ViIHByb2Nlc3NfbnVtIHsKICAg IG15ICgkbnVtKSA9IEBfOwoKICAgIG15ICR2YWw7CgogICAgIyBjaGVjayBpZiBpdCBpcyBuZWdh dGl2ZQogICAgaWYgKCRudW0gPX4gcy9eMHhmZmZmZmZmZi8weC8pIHsKCSR2YWwgPSB1bnBhY2so J2wnLCBwYWNrKCdMJywgb2N0KCRudW0pKSk7CiAgICB9IGVsc2UgewoJJHZhbCA9IG9jdCAkbnVt OwogICAgfQoKICAgIHJldHVybiAkdmFsOwp9Cgp3aGlsZSAoPD4pIHsKICAgIGlmICgvXltbOnhk aWdpdDpdXStccyg8XFMrPik6LykgewoJJHN0YXRlID0gJGZ1bmN0aW9uX3N0YXRlOwoJJGZ1bmMg PSAkMTsKCW5leHQ7CiAgICB9CgogICAgaWYgKC9cc3JldHEvKSB7Cgkkc3RhdGUgPSAkc3RhcnRf c3RhdGU7CgluZXh0OwogICAgfQoKICAgIGlmICgvXHNtb3ZccytcJXJzcCxcJXJicC8pIHsKCSRz dGF0ZSA9ICRmcmFtZV9zdGF0ZTsKCSRkZXB0aCA9IDA7CgluZXh0OwogICAgfQoKICAgIG5leHQg aWYgKCRzdGF0ZSAhPSAkZnJhbWVfc3RhdGUpOwoKICAgIGlmICgvXHNwdXNoXHMrXCUvIHx8IC9c c3B1c2hmcVxzKiQvIHx8IC9cc3B1c2hxXHMqKC0pPzB4LykgewoJJGRlcHRoIC09IDg7CgluZXh0 OwogICAgfQoKICAgIGlmICgvXHNwb3BccytcJS8gfHwgL1xzcG9wZnFccyokLykgewoJJGRlcHRo ICs9IDg7CgluZXh0OwogICAgfQoKICAgIGlmICgvXHNzdWJccytcJCgweFtbOnhkaWdpdDpdXSsp LFwlcnNwLykgewoJJGRlcHRoIC09IHByb2Nlc3NfbnVtKCQxKTsKCW5leHQ7CiAgICB9CgogICAg aWYgKC9cc2xlYVxzLykgewoJIyBpZ25vcmUgYWRkcmVzcyBjYWxjdWxhdGlvbnMKCW5leHQ7CiAg ICB9CgogICAgaWYgKC9cc2FkZFxzK1wkKDB4W1s6eGRpZ2l0Ol1dKyksXCVyc3AvKSB7CgkkZGVw dGggKz0gcHJvY2Vzc19udW0oJDEpOwoJbmV4dDsKICAgIH0KCiAgICBpZiAoLy0weChbWzp4ZGln aXQ6XV0rKVwoXCVyYnBcKS8pIHsKCW15ICRvZmZzZXQgPSBoZXggJDE7CglpZiAoJG9mZnNldCAr ICRkZXB0aCA+IDApIHsKCSAgICBwcmludCAiRVJST1I6ICRmdW5jOiBkZXB0aD0kZGVwdGggb2Zm c2V0PSRvZmZzZXQgYXQgJC5cbiI7CgkgICAgcHJpbnQ7CgkgICAgJGVycisrOwoJfQogICAgfQp9 CgppZiAoISRlcnIpIHsKICAgIHByaW50ICJBbGwgY2xlYW4hXG4iOwp9Cg== --MP_/EY6f5mVpsPZ2v5Fdq=b68VA--