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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 B5B11C433DF for ; Wed, 1 Jul 2020 07:03:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9362220722 for ; Wed, 1 Jul 2020 07:03:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728008AbgGAHDp (ORCPT ); Wed, 1 Jul 2020 03:03:45 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:7470 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726927AbgGAHDo (ORCPT ); Wed, 1 Jul 2020 03:03:44 -0400 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 49xXJF6R5rz9v1xr; Wed, 1 Jul 2020 09:03:41 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id lJg3lFJH2Aax; Wed, 1 Jul 2020 09:03:41 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 49xXJF20wwz9v1xq; Wed, 1 Jul 2020 09:03:41 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id C5EB48B7DE; Wed, 1 Jul 2020 09:03:41 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id o-A-Qpkw4yiK; Wed, 1 Jul 2020 09:03:41 +0200 (CEST) Received: from pc16570vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 1B87B8B75F; Wed, 1 Jul 2020 09:03:41 +0200 (CEST) Subject: Re: [PATCH v2] powerpc/uaccess: Use flexible addressing with __put_user()/__get_user() To: Segher Boessenkool Cc: Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , npiggin@gmail.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <7b916759-1683-b4df-0d4b-b04b3fcd9a02@csgroup.eu> <878sg6862r.fsf@mpe.ellerman.id.au> <875zb98i5a.fsf@mpe.ellerman.id.au> <311c3471-cad7-72d5-a5e6-04cf892c5e41@csgroup.eu> <20200630163324.GW3598@gate.crashing.org> <20200630211817.GZ3598@gate.crashing.org> From: Christophe Leroy Message-ID: Date: Wed, 1 Jul 2020 09:05:04 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200630211817.GZ3598@gate.crashing.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 30/06/2020 à 23:18, Segher Boessenkool a écrit : > Hi again, > > Thanks for your work so far! > > On Tue, Jun 30, 2020 at 06:53:39PM +0000, Christophe Leroy wrote: >> On 06/30/2020 04:33 PM, Segher Boessenkool wrote: >>>>> + make -s CC=powerpc64-linux-gnu-gcc -j 160 >>>>> In file included from /linux/include/linux/uaccess.h:11:0, >>>>> from /linux/include/linux/sched/task.h:11, >>>>> from /linux/include/linux/sched/signal.h:9, >>>>> from /linux/include/linux/rcuwait.h:6, >>>>> from /linux/include/linux/percpu-rwsem.h:7, >>>>> from /linux/include/linux/fs.h:33, >>>>> from /linux/include/linux/huge_mm.h:8, >>>>> from /linux/include/linux/mm.h:675, >>>>> from /linux/arch/powerpc/kernel/signal_32.c:17: >>>>> /linux/arch/powerpc/kernel/signal_32.c: In function >>>>> 'save_user_regs.isra.14.constprop': >>>>> /linux/arch/powerpc/include/asm/uaccess.h:161:2: error: 'asm' operand has >>>>> impossible constraints >>>>> __asm__ __volatile__( \ >>>>> ^ >>>>> /linux/arch/powerpc/include/asm/uaccess.h:197:12: note: in expansion of >>>>> macro '__put_user_asm' >>>>> case 4: __put_user_asm(x, ptr, retval, "stw"); break; \ >>>>> ^ >>>>> /linux/arch/powerpc/include/asm/uaccess.h:206:2: note: in expansion of >>>>> macro '__put_user_size_allowed' >>>>> __put_user_size_allowed(x, ptr, size, retval); \ >>>>> ^ >>>>> /linux/arch/powerpc/include/asm/uaccess.h:220:2: note: in expansion of >>>>> macro '__put_user_size' >>>>> __put_user_size(__pu_val, __pu_addr, __pu_size, __pu_err); \ >>>>> ^ >>>>> /linux/arch/powerpc/include/asm/uaccess.h:96:2: note: in expansion of >>>>> macro '__put_user_nocheck' >>>>> __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr))) >>>>> ^ >>>>> /linux/arch/powerpc/kernel/signal_32.c:120:7: note: in expansion of macro >>>>> '__put_user' >>>>> if (__put_user((unsigned int)gregs[i], &frame->mc_gregs[i])) >>>>> ^ >>> >>> Can we see what that was after the macro jungle? Like, the actual >>> preprocessed code? >> >> Sorry for previous misunderstanding >> >> Here is the code: >> >> #define __put_user_asm(x, addr, err, op) \ >> __asm__ __volatile__( \ >> "1: " op "%U2%X2 %1,%2 # put_user\n" \ >> "2:\n" \ >> ".section .fixup,\"ax\"\n" \ >> "3: li %0,%3\n" \ >> " b 2b\n" \ >> ".previous\n" \ >> EX_TABLE(1b, 3b) \ >> : "=r" (err) \ >> : "r" (x), "m<>" (*addr), "i" (-EFAULT), "0" (err)) > > Yeah I don't see it. I'll have to look at compiler debug dumps, but I > don't have any working 4.9 around, and I cannot reproduce this with > either older or newer compilers. I reproduced it with 4.8.5 > > It is complainig that constrain_operands just does not work *at all* on > this "m<>" constraint apparently, which doesn't make much sense. > Here is a small reproducer: #include #include #include struct mcontext { elf_gregset_t32 mc_gregs; elf_fpregset_t mc_fregs; unsigned int mc_pad[2]; elf_vrregset_t32 mc_vregs __attribute__((__aligned__(16))); elf_vsrreghalf_t32 mc_vsregs __attribute__((__aligned__(16))); }; int save_general_regs(struct pt_regs *regs, struct mcontext __user *frame) { elf_greg_t64 *gregs = (elf_greg_t64 *)regs; int i; for (i = 0; i <= PT_RESULT; i ++) { if (i == 14) i = 32; if (__put_user((unsigned int)gregs[i], &frame->mc_gregs[i])) return -EFAULT; } return 0; } If you remove the "if i == 14 ..." you get no failure. Preprocessor result: int save_general_regs(struct pt_regs *regs, struct mcontext *frame) { elf_greg_t64 *gregs = (elf_greg_t64 *)regs; int i; for (i = 0; i <= 43; i ++) { if (i == 14) i = 32; if (({ long __pu_err; __typeof__(*((&frame->mc_gregs[i]))) *__pu_addr = ((&frame->mc_gregs[i])); __typeof__(*((&frame->mc_gregs[i]))) __pu_val = ((__typeof__(*(&frame->mc_gregs[i])))((unsigned int)gregs[i])); __typeof__(sizeof(*(&frame->mc_gregs[i]))) __pu_size = (sizeof(*(&frame->mc_gregs[i]))); if (!(((unsigned long)__pu_addr) >= 0x8000000000000000ul)) might_fault(); (void)0; do { allow_write_to_user(__pu_addr, __pu_size); do { __pu_err = 0; switch (__pu_size) { case 1: __asm__ __volatile__( "1: " "stb" "%U2%X2 %1,%2 # put_user\n" "2:\n" ".section .fixup,\"ax\"\n" "3: li %0,%3\n" " b 2b\n" ".previous\n" ".section __ex_table,\"a\";" " " ".balign 4;" " " ".long (1b) - . ;" " " ".long (3b) - . ;" " " ".previous" " " : "=r" (__pu_err) : "r" (__pu_val), "m<>" (*__pu_addr), "i" (-14), "0" (__pu_err)); break; case 2: __asm__ __volatile__( "1: " "sth" "%U2%X2 %1,%2 # put_user\n" "2:\n" ".section .fixup,\"ax\"\n" "3: li %0,%3\n" " b 2b\n" ".previous\n" ".section __ex_table,\"a\";" " " ".balign 4;" " " ".long (1b) - . ;" " " ".long (3b) - . ;" " " ".previous" " " : "=r" (__pu_err) : "r" (__pu_val), "m<>" (*__pu_addr), "i" (-14), "0" (__pu_err)); break; case 4: __asm__ __volatile__( "1: " "stw" "%U2%X2 %1,%2 # put_user\n" "2:\n" ".section .fixup,\"ax\"\n" "3: li %0,%3\n" " b 2b\n" ".previous\n" ".section __ex_table,\"a\";" " " ".balign 4;" " " ".long (1b) - . ;" " " ".long (3b) - . ;" " " ".previous" " " : "=r" (__pu_err) : "r" (__pu_val), "m<>" (*__pu_addr), "i" (-14), "0" (__pu_err)); break; case 8: __asm__ __volatile__( "1: " "std" "%U2%X2 %1,%2 # put_user\n" "2:\n" ".section .fixup,\"ax\"\n" "3: li %0,%3\n" " b 2b\n" ".previous\n" ".section __ex_table,\"a\";" " " ".balign 4;" " " ".long (1b) - . ;" " " ".long (3b) - . ;" " " ".previous" " " : "=r" (__pu_err) : "r" (__pu_val), "m<>" (*__pu_addr), "i" (-14), "0" (__pu_err)); break; default: __put_user_bad(); } } while (0); prevent_write_to_user(__pu_addr, __pu_size); } while (0); __pu_err; })) return -14; } return 0; } Christophe