From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Date: Sat, 04 Mar 2017 23:08:50 +0000 Subject: Re: [PATCH 1/3] futex: remove duplicated code Message-Id: <201703042308.v24N8wvh012716@mail.zytor.com> List-Id: References: <20170303122712.13353-1-jslaby@suse.cz> <20170304130550.GT21222@n2100.armlinux.org.uk> <3994975e-89a5-d2b5-60be-a8633ddc3733@zytor.com> <20170304213805.GA2449@lianli.shorne-pla.net> In-Reply-To: <20170304213805.GA2449@lianli.shorne-pla.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Stafford Horne Cc: Russell King - ARM Linux , Jiri Slaby , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Catalin Marinas , Will Deacon , Richard Kuo , Tony Luck , Fenghua Yu , Michal Simek , Ralf Baechle , Jonas Bonn , Stefan Kristiansson , "James E.J. Bottomley" , Helge Deller , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Martin Schwidefsky , Heiko Carstens , Yoshinori Sato , Rich Felker , "David S. Miller"@zytor.com ,Chris Metcalf ,Thomas Gleixner ,Ingo Molnar ,Chris Zankel ,Max Filippov ,Arnd Bergmann ,x86@kernel.org,linux-alpha@vger.kernel.org,linux-snps-arc@lists.infradead.org,linux-arm-kernel@lists.infradead.org,linux-hexagon@vger.kernel.org,linux-ia64@vger.kernel.org,linux-mips@linux-mips.org,openrisc@lists.librecores.org,linux-parisc@vger.kernel.org,linuxppc-dev@lists.ozlabs.org,linux-s390@vger.kernel.org,linux-sh@vger.kernel.org,sparclinux@vger.kernel.org,linux-xtensa@linux-xtensa.org,linux-arch@vger.kernel.org From: hpa@zytor.com Message-ID: On March 4, 2017 1:38:05 PM PST, Stafford Horne wrote: >On Sat, Mar 04, 2017 at 11:15:17AM -0800, H. Peter Anvin wrote: >> On 03/04/17 05:05, Russell King - ARM Linux wrote: >> >> >> >> +static int futex_atomic_op_inuser(int encoded_op, u32 __user >*uaddr) >> >> +{ >> >> + int op = (encoded_op >> 28) & 7; >> >> + int cmp = (encoded_op >> 24) & 15; >> >> + int oparg = (encoded_op << 8) >> 20; >> >> + int cmparg = (encoded_op << 20) >> 20; >> > >> > Hmm. oparg and cmparg look like they're doing these shifts to get >sign >> > extension of the 12-bit values by assuming that "int" is 32-bit - >> > probably worth a comment, or for safety, they should be "s32" so >it's >> > not dependent on the bit-width of "int". >> > >> >> For readability, perhaps we should make sign- and zero-extension an >> explicit facility? > >There is some of this in already here, 32 and 64 bit versions: > > include/linux/bitops.h > >Do we really need zero extension? It seems the same. > >Example implementation from bitops.h > >static inline __s32 sign_extend32(__u32 value, int index) >{ > __u8 shift = 31 - index; > return (__s32)(value << shift) >> shift; >} > >> /* >> * Truncate an integer x to n bits, using sign- or >> * zero-extension, respectively. >> */ >> static inline __const_func__ s32 sex32(s32 x, int n) >> { >> return (x << (32-n)) >> (32-n); >> } >> >> static inline __const_func__ s64 sex64(s64 x, int n) >> { >> return (x << (64-n)) >> (64-n); >> } >> >> #define sex(x,y) \ >> ((__typeof__(x)) \ >> (((__builtin_constant_p(y) && ((y) <= 32)) || \ >> (sizeof(x) <= sizeof(s32))) \ >> ? sex32((x),(y)) : sex64((x),(y)))) >> >> static inline __const_func__ u32 zex32(u32 x, int n) >> { >> return (x << (32-n)) >> (32-n); >> } >> >> static inline __const_func__ u64 zex64(u64 x, int n) >> { >> return (x << (64-n)) >> (64-n); >> } >> >> #define zex(x,y) \ >> ((__typeof__(x)) \ >> (((__builtin_constant_p(y) && ((y) <= 32)) || \ >> (sizeof(x) <= sizeof(u32))) \ >> ? zex32((x),(y)) : zex64((x),(y)))) >> Also, i strongly believe that making it syntactically cumbersome encodes people to open-code it which is bad... -- Sent from my Android device with K-9 Mail. Please excuse my brevity. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752503AbdCDXNz convert rfc822-to-8bit (ORCPT ); Sat, 4 Mar 2017 18:13:55 -0500 Received: from terminus.zytor.com ([65.50.211.136]:58738 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752186AbdCDXNw (ORCPT ); Sat, 4 Mar 2017 18:13:52 -0500 From: "H. Peter Anvin" Message-Id: <201703042308.v24N8wvh012716@mail.zytor.com> Date: Sat, 04 Mar 2017 15:08:50 -0800 User-Agent: K-9 Mail for Android In-Reply-To: <20170304213805.GA2449@lianli.shorne-pla.net> References: <20170303122712.13353-1-jslaby@suse.cz> <20170304130550.GT21222@n2100.armlinux.org.uk> <3994975e-89a5-d2b5-60be-a8633ddc3733@zytor.com> <20170304213805.GA2449@lianli.shorne-pla.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Subject: Re: [PATCH 1/3] futex: remove duplicated code To: Stafford Horne CC: Russell King - ARM Linux , Jiri Slaby , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Catalin Marinas , Will Deacon , Richard Kuo , Tony Luck , Fenghua Yu , Michal Simek , Ralf Baechle , Jonas Bonn , Stefan Kristiansson , "James E.J. Bottomley" , Helge Deller , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Martin Schwidefsky , Heiko Carstens , Yoshinori Sato , Rich Felker , "David S. Miller"@zytor.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ,Chris Metcalf ,Thomas Gleixner ,Ingo Molnar ,Chris Zankel ,Max Filippov ,Arnd Bergmann ,x86@kernel.org,linux-alpha@vger.kernel.org,linux-snps-arc@lists.infradead.org,linux-arm-kernel@lists.infradead.org,linux-hexagon@vger.kernel.org,linux-ia64@vger.kernel.org,linux-mips@linux-mips.org,openrisc@lists.librecores.org,linux-parisc@vger.kernel.org,linuxppc-dev@lists.ozlabs.org,linux-s390@vger.kernel.org,linux-sh@vger.kernel.org,sparclinux@vger.kernel.org,linux-xtensa@linux-xtensa.org,linux-arch@vger.kernel.org From: hpa@zytor.com Message-ID: On March 4, 2017 1:38:05 PM PST, Stafford Horne wrote: >On Sat, Mar 04, 2017 at 11:15:17AM -0800, H. Peter Anvin wrote: >> On 03/04/17 05:05, Russell King - ARM Linux wrote: >> >> >> >> +static int futex_atomic_op_inuser(int encoded_op, u32 __user >*uaddr) >> >> +{ >> >> + int op = (encoded_op >> 28) & 7; >> >> + int cmp = (encoded_op >> 24) & 15; >> >> + int oparg = (encoded_op << 8) >> 20; >> >> + int cmparg = (encoded_op << 20) >> 20; >> > >> > Hmm. oparg and cmparg look like they're doing these shifts to get >sign >> > extension of the 12-bit values by assuming that "int" is 32-bit - >> > probably worth a comment, or for safety, they should be "s32" so >it's >> > not dependent on the bit-width of "int". >> > >> >> For readability, perhaps we should make sign- and zero-extension an >> explicit facility? > >There is some of this in already here, 32 and 64 bit versions: > > include/linux/bitops.h > >Do we really need zero extension? It seems the same. > >Example implementation from bitops.h > >static inline __s32 sign_extend32(__u32 value, int index) >{ > __u8 shift = 31 - index; > return (__s32)(value << shift) >> shift; >} > >> /* >> * Truncate an integer x to n bits, using sign- or >> * zero-extension, respectively. >> */ >> static inline __const_func__ s32 sex32(s32 x, int n) >> { >> return (x << (32-n)) >> (32-n); >> } >> >> static inline __const_func__ s64 sex64(s64 x, int n) >> { >> return (x << (64-n)) >> (64-n); >> } >> >> #define sex(x,y) \ >> ((__typeof__(x)) \ >> (((__builtin_constant_p(y) && ((y) <= 32)) || \ >> (sizeof(x) <= sizeof(s32))) \ >> ? sex32((x),(y)) : sex64((x),(y)))) >> >> static inline __const_func__ u32 zex32(u32 x, int n) >> { >> return (x << (32-n)) >> (32-n); >> } >> >> static inline __const_func__ u64 zex64(u64 x, int n) >> { >> return (x << (64-n)) >> (64-n); >> } >> >> #define zex(x,y) \ >> ((__typeof__(x)) \ >> (((__builtin_constant_p(y) && ((y) <= 32)) || \ >> (sizeof(x) <= sizeof(u32))) \ >> ? zex32((x),(y)) : zex64((x),(y)))) >> Also, i strongly believe that making it syntactically cumbersome encodes people to open-code it which is bad... -- Sent from my Android device with K-9 Mail. Please excuse my brevity. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.zytor.com (unknown [IPv6:2001:1868:a000:17::138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vbMKY6D1gzDq5W for ; Sun, 5 Mar 2017 10:13:05 +1100 (AEDT) From: "H. Peter Anvin" Message-Id: <201703042308.v24N8wvh012716@mail.zytor.com> Date: Sat, 04 Mar 2017 15:08:50 -0800 In-Reply-To: <20170304213805.GA2449@lianli.shorne-pla.net> References: <20170303122712.13353-1-jslaby@suse.cz> <20170304130550.GT21222@n2100.armlinux.org.uk> <3994975e-89a5-d2b5-60be-a8633ddc3733@zytor.com> <20170304213805.GA2449@lianli.shorne-pla.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Subject: Re: [PATCH 1/3] futex: remove duplicated code To: Stafford Horne CC: Russell King - ARM Linux , Jiri Slaby , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Catalin Marinas , Will Deacon , Richard Kuo , Tony Luck , Fenghua Yu , Michal Simek , Ralf Baechle , Jonas Bonn , Stefan Kristiansson , "James E.J. Bottomley" , Helge Deller , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Martin Schwidefsky , Heiko Carstens , Yoshinori Sato , Rich Felker , "David S. Miller"@zytor.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , ,Chris Metcalf ,Thomas Gleixner ,Ingo Molnar ,Chris Zankel ,Max Filippov ,Arnd Bergmann ,x86@kernel.org,linux-alpha@vger.kernel.org,linux-snps-arc@lists.infradead.org,linux-arm-kernel@lists.infradead.org,linux-hexagon@vger.kernel.org,linux-ia64@vger.kernel.org,linux-mips@linux-mips.org,openrisc@lists.librecores.org,linux-parisc@vger.kernel.org,linuxppc-dev@lists.ozlabs.org,linux-s390@vger.kernel.org,linux-sh@vger.kernel.org,sparclinux@vger.kernel.org,linux-xtensa@linux-xtensa.org,linux-arch@vger.kernel.org From: hpa@zytor.com Message-ID: On March 4, 2017 1:38:05 PM PST, Stafford Horne wrote: >On Sat, Mar 04, 2017 at 11:15:17AM -0800, H=2E Peter Anvin wrote: >> On 03/04/17 05:05, Russell King - ARM Linux wrote: >> >> =20 >> >> +static int futex_atomic_op_inuser(int encoded_op, u32 __user >*uaddr) >> >> +{ >> >> + int op =3D (encoded_op >> 28) & 7; >> >> + int cmp =3D (encoded_op >> 24) & 15; >> >> + int oparg =3D (encoded_op << 8) >> 20; >> >> + int cmparg =3D (encoded_op << 20) >> 20; >> >=20 >> > Hmm=2E oparg and cmparg look like they're doing these shifts to get >sign >> > extension of the 12-bit values by assuming that "int" is 32-bit - >> > probably worth a comment, or for safety, they should be "s32" so >it's >> > not dependent on the bit-width of "int"=2E >> >=20 >>=20 >> For readability, perhaps we should make sign- and zero-extension an >> explicit facility? > >There is some of this in already here, 32 and 64 bit versions: > > include/linux/bitops=2Eh > >Do we really need zero extension? It seems the same=2E > >Example implementation from bitops=2Eh > >static inline __s32 sign_extend32(__u32 value, int index) >{ > __u8 shift =3D 31 - index; > return (__s32)(value << shift) >> shift; >} > >> /* >> * Truncate an integer x to n bits, using sign- or >> * zero-extension, respectively=2E >> */ >> static inline __const_func__ s32 sex32(s32 x, int n) >> { >> return (x << (32-n)) >> (32-n); >> } >>=20 >> static inline __const_func__ s64 sex64(s64 x, int n) >> { >> return (x << (64-n)) >> (64-n); >> } >>=20 >> #define sex(x,y) \ >> ((__typeof__(x)) \ >> (((__builtin_constant_p(y) && ((y) <=3D 32)) || \ >> (sizeof(x) <=3D sizeof(s32))) \ >> ? sex32((x),(y)) : sex64((x),(y)))) >>=20 >> static inline __const_func__ u32 zex32(u32 x, int n) >> { >> return (x << (32-n)) >> (32-n); >> } >>=20 >> static inline __const_func__ u64 zex64(u64 x, int n) >> { >> return (x << (64-n)) >> (64-n); >> } >>=20 >> #define zex(x,y) \ >> ((__typeof__(x)) \ >> (((__builtin_constant_p(y) && ((y) <=3D 32)) || \ >> (sizeof(x) <=3D sizeof(u32))) \ >> ? zex32((x),(y)) : zex64((x),(y)))) >>=20 Also, i strongly believe that making it syntactically cumbersome encodes p= eople to open-code it which is bad=2E=2E=2E --=20 Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E From mboxrd@z Thu Jan 1 00:00:00 1970 From: hpa@zytor.com (H. Peter Anvin) Date: Sat, 04 Mar 2017 15:08:50 -0800 Subject: [PATCH 1/3] futex: remove duplicated code In-Reply-To: <20170304213805.GA2449@lianli.shorne-pla.net> References: <20170303122712.13353-1-jslaby@suse.cz> <20170304130550.GT21222@n2100.armlinux.org.uk> <3994975e-89a5-d2b5-60be-a8633ddc3733@zytor.com> <20170304213805.GA2449@lianli.shorne-pla.net> List-ID: Message-ID: <201703042308.v24N8wvh012716@mail.zytor.com> To: linux-snps-arc@lists.infradead.org ,Chris Metcalf ,Thomas Gleixner ,Ingo Molnar ,Chris Zankel ,Max Filippov ,Arnd Bergmann ,x86 at kernel.org,linux-alpha at vger.kernel.org,linux-snps-arc at lists.infradead.org,linux-arm-kernel at lists.infradead.org,linux-hexagon at vger.kernel.org,linux-ia64 at vger.kernel.org,linux-mips at linux-mips.org,openrisc at lists.librecores.org,linux-parisc at vger.kernel.org,linuxppc-dev at lists.ozlabs.org,linux-s390 at vger.kernel.org,linux-sh at vger.kernel.org,sparclinux at vger.kernel.org,linux-xtensa at linux-xtensa.org,linux-arch at vger.kernel.org From: hpa@zytor.com List-ID: To: linux-snps-arc@lists.infradead.org Message-ID: On March 4, 2017 1:38:05 PM PST, Stafford Horne wrote: >On Sat, Mar 04, 2017@11:15:17AM -0800, H. Peter Anvin wrote: >> On 03/04/17 05:05, Russell King - ARM Linux wrote: >> >> >> >> +static int futex_atomic_op_inuser(int encoded_op, u32 __user >*uaddr) >> >> +{ >> >> + int op = (encoded_op >> 28) & 7; >> >> + int cmp = (encoded_op >> 24) & 15; >> >> + int oparg = (encoded_op << 8) >> 20; >> >> + int cmparg = (encoded_op << 20) >> 20; >> > >> > Hmm. oparg and cmparg look like they're doing these shifts to get >sign >> > extension of the 12-bit values by assuming that "int" is 32-bit - >> > probably worth a comment, or for safety, they should be "s32" so >it's >> > not dependent on the bit-width of "int". >> > >> >> For readability, perhaps we should make sign- and zero-extension an >> explicit facility? > >There is some of this in already here, 32 and 64 bit versions: > > include/linux/bitops.h > >Do we really need zero extension? It seems the same. > >Example implementation from bitops.h > >static inline __s32 sign_extend32(__u32 value, int index) >{ > __u8 shift = 31 - index; > return (__s32)(value << shift) >> shift; >} > >> /* >> * Truncate an integer x to n bits, using sign- or >> * zero-extension, respectively. >> */ >> static inline __const_func__ s32 sex32(s32 x, int n) >> { >> return (x << (32-n)) >> (32-n); >> } >> >> static inline __const_func__ s64 sex64(s64 x, int n) >> { >> return (x << (64-n)) >> (64-n); >> } >> >> #define sex(x,y) \ >> ((__typeof__(x)) \ >> (((__builtin_constant_p(y) && ((y) <= 32)) || \ >> (sizeof(x) <= sizeof(s32))) \ >> ? sex32((x),(y)) : sex64((x),(y)))) >> >> static inline __const_func__ u32 zex32(u32 x, int n) >> { >> return (x << (32-n)) >> (32-n); >> } >> >> static inline __const_func__ u64 zex64(u64 x, int n) >> { >> return (x << (64-n)) >> (64-n); >> } >> >> #define zex(x,y) \ >> ((__typeof__(x)) \ >> (((__builtin_constant_p(y) && ((y) <= 32)) || \ >> (sizeof(x) <= sizeof(u32))) \ >> ? zex32((x),(y)) : zex64((x),(y)))) >> Also, i strongly believe that making it syntactically cumbersome encodes people to open-code it which is bad... -- Sent from my Android device with K-9 Mail. Please excuse my brevity.