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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7921EC4708D for ; Fri, 16 Dec 2022 11:41:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229912AbiLPLlC (ORCPT ); Fri, 16 Dec 2022 06:41:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43832 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229780AbiLPLlA (ORCPT ); Fri, 16 Dec 2022 06:41:00 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 951A41658C; Fri, 16 Dec 2022 03:40:57 -0800 (PST) Received: from dggpemm500006.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4NYRwT59tyzmWjQ; Fri, 16 Dec 2022 19:39:53 +0800 (CST) Received: from [10.174.178.55] (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Fri, 16 Dec 2022 19:40:54 +0800 Subject: Re: [PATCH v9] kallsyms: Add self-test facility To: David Laight , 'Geert Uytterhoeven' CC: Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , "live-patching@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Masahiro Yamada , Alexei Starovoitov , Jiri Olsa , Kees Cook , Andrew Morton , Luis Chamberlain , "linux-modules@vger.kernel.org" , Steven Rostedt , Ingo Molnar , linux-m68k , "Jason A. Donenfeld" References: <20221115083349.1662-1-thunder.leizhen@huawei.com> From: "Leizhen (ThunderTown)" Message-ID: <75b4f3be-1e79-5602-5774-aa1fab3f07ce@huawei.com> Date: Fri, 16 Dec 2022 19:40:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On 2022/12/16 18:40, David Laight wrote: > From: Geert Uytterhoeven >> Sent: 15 December 2022 13:25 > ... >> Looks like commit 3bc753c06dd02a35 ("kbuild: treat char as always >> unsigned") is to blame. >> >> Changing: >> >> --- a/arch/m68k/include/asm/string.h >> +++ b/arch/m68k/include/asm/string.h >> @@ -42,7 +42,7 @@ static inline char *strncpy(char *dest, const >> char *src, size_t n) >> #define __HAVE_ARCH_STRCMP >> static inline int strcmp(const char *cs, const char *ct) >> { >> - char res; >> + signed char res; >> >> asm ("\n" >> "1: move.b (%0)+,%2\n" /* get *cs */ >> >> fixes strcmp, but the test still fails: > > Try 'int res;' and an explicit sign extend (I think): > "3: extb %2\n" Compilation failed. I tried "return (int)(signed char)res;", it's still failed. > > The strcmp() is still wrong if either input string > has characters with the top bit set. > The result needs to be based of the carry flag not > the sign of the byte subtract. > > It is too long since I've written m68k asm. > I've checked, all byte operations leave the high 24bits > unchanged. Currently, only ASCCIs. So it won't be the reason. > So it is possible that gcc is making assumptions and > skipping the sign extend under some circumstances. Wow, because compare_symbol_name() works properly during the previous binary search, the compiler must have done something bad. So I add 'volatile' to prevent compiler optimizations, and it's OK now. diff --git a/arch/m68k/include/asm/string.h b/arch/m68k/include/asm/string.h index f759d944c449940..3db81e5a783c72a 100644 --- a/arch/m68k/include/asm/string.h +++ b/arch/m68k/include/asm/string.h @@ -42,9 +42,9 @@ static inline char *strncpy(char *dest, const char *src, size_t n) #define __HAVE_ARCH_STRCMP static inline int strcmp(const char *cs, const char *ct) { - char res; + signed char res; - asm ("\n" + asm volatile ("\n" "1: move.b (%0)+,%2\n" /* get *cs */ " cmp.b (%1)+,%2\n" /* compare a byte */ " jne 2f\n" /* not equal, break out */ > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) > -- Regards, Zhen Lei