From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F3E2C43381 for ; Thu, 7 Mar 2019 17:12:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 38B182081B for ; Thu, 7 Mar 2019 17:12:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726526AbfCGRMU convert rfc822-to-8bit (ORCPT ); Thu, 7 Mar 2019 12:12:20 -0500 Received: from terminus.zytor.com ([198.137.202.136]:35783 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726351AbfCGRMS (ORCPT ); Thu, 7 Mar 2019 12:12:18 -0500 Received: from [172.19.131.165] ([8.46.77.96]) (authenticated bits=0) by mail.zytor.com (8.15.2/8.15.2) with ESMTPSA id x27HBMrG2267650 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NO); Thu, 7 Mar 2019 09:11:27 -0800 Date: Thu, 07 Mar 2019 09:04:36 -0800 User-Agent: K-9 Mail for Android In-Reply-To: <20190307164705.qbu4ytdfdmsighas@treble> References: <20190307114511.870090179@infradead.org> <20190307120317.GD32477@hirez.programming.kicks-ass.net> <20190307125526.GB32534@hirez.programming.kicks-ass.net> <20190307131312.GC32534@hirez.programming.kicks-ass.net> <20190307164705.qbu4ytdfdmsighas@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Subject: Re: [PATCH 00/20] objtool: UACCESS validation v3 To: Josh Poimboeuf , Peter Zijlstra CC: torvalds@linux-foundation.org, tglx@linutronix.de, julien.thierry@arm.com, will.deacon@arm.com, luto@amacapital.net, mingo@kernel.org, catalin.marinas@arm.com, james.morse@arm.com, valentin.schneider@arm.com, brgerst@gmail.com, luto@kernel.org, bp@alien8.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org, dvyukov@google.com, rostedt@goodmis.org From: hpa@zytor.com Message-ID: <2F80FC70-5D2F-425F-BEB5-D70E981CC684@zytor.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On March 7, 2019 8:47:05 AM PST, Josh Poimboeuf wrote: >On Thu, Mar 07, 2019 at 02:13:12PM +0100, Peter Zijlstra wrote: >> On Thu, Mar 07, 2019 at 01:55:26PM +0100, Peter Zijlstra wrote: >> > On Thu, Mar 07, 2019 at 01:03:17PM +0100, Peter Zijlstra wrote: >> >> >> > > 01be 20d3: 31 c0 xor %eax,%eax >> > > 01c0 20d5: 4c 39 eb cmp %r13,%rbx >> > > 01c3 20d8: 77 08 ja 20e2 ><__do_sys_waitid+0x1cd> >> >> randconfig-build/kernel/exit.o: warning: objtool: >__do_sys_waitid()+0x1c3: (branch) >> >> > > 01cd 20e2: 83 f0 01 xor $0x1,%eax >> > > 01d0 20e5: 48 89 c2 mov %rax,%rdx >> > > 01d3 20e8: 83 e2 01 and $0x1,%edx >> > > 01d6 20eb: 48 83 c2 02 add $0x2,%rdx >> > > 01da 20ef: 48 ff 04 d5 00 00 00 incq 0x0(,%rdx,8) >> > > 01e1 20f6: 00 >> > > 01de 20f3: R_X86_64_32S _ftrace_branch+0x148 >> > > 01e2 20f7: 84 c0 test %al,%al >> > > 01e4 20f9: 75 2d jne 2128 ><__do_sys_waitid+0x213> >> > >> > we do not take this branch and fall-through. >> >> And that is the error, I think. We should've taken it and went to: >> >> return -EFAULT; >> >> because: >> >> +1be xor %eax,%eax eax=0 >> +1cd xor $0x1,%eax eax=1 >> +1e2 test %al,%al 1&1==1 -> ZF=0 >> +1e4 jnz >> >> Is an unconditional code sequence, but there's no way objtool can do >> that without becoming a full blown interpreter :/ >> >> > > 0213 2128: 49 c7 c7 f2 ff ff ff mov >$0xfffffffffffffff2,%r15 >> > > ffffffffffffe0eb } >> > > 021a 212f: 48 8d 65 d8 lea -0x28(%rbp),%rsp >> > > 021e 2133: 4c 89 f8 mov %r15,%rax >> > > 0221 2136: 5b pop %rbx >> > > 0222 2137: 41 5c pop %r12 >> > > 0224 2139: 41 5d pop %r13 >> > > 0226 213b: 41 5e pop %r14 >> > > 0228 213d: 41 5f pop %r15 >> > > 022a 213f: 5d pop %rbp >> > > 022b 2140: c3 retq > >This "fixes" it, and also seems to help -Os make much code: > >diff --git a/include/linux/compiler.h b/include/linux/compiler.h >index 445348facea9..8de63db58fdd 100644 >--- a/include/linux/compiler.h >+++ b/include/linux/compiler.h >@@ -67,7 +67,7 @@ void ftrace_likely_update(struct ftrace_likely_data >*f, int val, > .line = __LINE__, \ > }; \ > ______r = !!(cond); \ >- ______f.miss_hit[______r]++; \ >+ if (______r) ______f.miss_hit[1]++; else ______f.miss_hit[0]++; \ > ______r; \ > })) > #endif /* CONFIG_PROFILE_ALL_BRANCHES */ if (cond)? Or is ___r used elsewhere? -- Sent from my Android device with K-9 Mail. Please excuse my brevity.