From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751786AbeBHJfr (ORCPT ); Thu, 8 Feb 2018 04:35:47 -0500 Received: from merlin.infradead.org ([205.233.59.134]:44898 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750806AbeBHJfp (ORCPT ); Thu, 8 Feb 2018 04:35:45 -0500 Date: Thu, 8 Feb 2018 10:35:35 +0100 From: Peter Zijlstra To: Linus Torvalds Cc: Borislav Petkov , kbuild test robot , Ingo Molnar , Thomas Gleixner , LKML , the arch/x86 maintainers Subject: Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f Message-ID: <20180208093535.GE25235@hirez.programming.kicks-ass.net> References: <5a7ae6af.WSMpvDEeUt6oucKB%fengguang.wu@intel.com> <20180207183543.GA8897@pd.tnic> <20180207184933.GA25201@hirez.programming.kicks-ass.net> <20180207191451.GC25201@hirez.programming.kicks-ass.net> <20180207192816.GA19536@pd.tnic> <20180208091302.GD25201@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180208091302.GD25201@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 08, 2018 at 10:13:02AM +0100, Peter Zijlstra wrote: > _The_ problem is that new binutils cannot sanely decode any function > that has a WARN in (this very much includes perf annotate): > new: > > 00000000000016a0 : > 16a0: 48 89 f2 mov %rsi,%rdx > 16a3: 89 fe mov %edi,%esi > 16a5: 48 c7 c7 00 00 00 00 mov $0x0,%rdi > 16a8: R_X86_64_32S .rodata.str1.8+0x288 > 16ac: e8 00 00 00 00 callq 16b1 > 16ad: R_X86_64_PC32 __warn_printk-0x4 > 16b1: 0f ff c3 ud0 %ebx,%eax > 16b4: 66 90 xchg %ax,%ax > 16b6: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1) > 16bd: 00 00 00 And note that this example is fairly 'good' as far as things go, it only eats the single byte ret instruction and is on an instruction boundary again, so the rest is good. There are examples where what it eats results in shifting the instruction boundary and the rest is _complete_ crap. Look what it does to sched_cpu_dying: 7199: 48 39 c3 cmp %rax,%rbx 719c: 0f 84 cc 00 00 00 je 726e 71a2: 0f ff 41 c6 ud0 -0x3a(%rcx),%eax 71a6: 87 3c 07 xchg %edi,(%rdi,%rax,1) 71a9: 00 00 add %al,(%rax) 71ab: 00 8b 43 04 83 f8 add %cl,-0x77cfbbd(%rbx) 71b1: 01 0f add %ecx,(%rdi) 71b3: 85 4f ff test %ecx,-0x1(%rdi) 71b6: ff (bad) 71b7: ff 48 8b decl -0x75(%rax) 71ba: 44 24 08 rex.R and $0x8,%al 7199: 48 39 c3 cmp %rax,%rbx 719c: 0f 84 cc 00 00 00 je 726e 71a2: 0f ff (bad) 71a4: 41 c6 87 3c 07 00 00 movb $0x0,0x73c(%r15) 71ab: 00 71ac: 8b 43 04 mov 0x4(%rbx),%eax 71af: 83 f8 01 cmp $0x1,%eax 71b2: 0f 85 4f ff ff ff jne 7107 71b8: 48 8b 44 24 08 mov 0x8(%rsp),%rax 71bd: 48 8b 74 24 10 mov 0x10(%rsp),%rsi