Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752577AbZA1BiQ (ORCPT ); Tue, 27 Jan 2009 20:38:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751905AbZA1Bh7 (ORCPT ); Tue, 27 Jan 2009 20:37:59 -0500 Received: from hera.kernel.org ([140.211.167.34]:55539 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751887AbZA1Bh7 (ORCPT ); Tue, 27 Jan 2009 20:37:59 -0500 Subject: Re: [mingo@elte.hu: [git pull] headers_check fixes] From: Jaswinder Singh Rajput To: Linus Torvalds Cc: Ingo Molnar , Linux Kernel Mailing List , Andrew Morton , Sam Ravnborg , Jaswinder Singh Rajput , "David S. Miller" In-Reply-To: References: <20090127222825.GA27097@elte.hu> Content-Type: text/plain Date: Wed, 28 Jan 2009 07:06:54 +0530 Message-Id: <1233106614.3256.6.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.24.3 (2.24.3-1.fc10) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4268 Lines: 132 On Tue, 2009-01-27 at 14:57 -0800, Linus Torvalds wrote: > > The thing is, the headers_check stuff is just wrong if it causes these > things, and I'd rather just turn it off. > Basic idea of headers_check is: 1. clean header files so that they do not export useless things in userspace, like: usr/include/linux/elf-fdpic.h:62: extern's make no sense in userspace 2. provide sufficient stuff like: usr/include/asm/swab.h:7: found __[us]{8,16,32,64} type without #include 3. warns about exporting kernel space defines which are not valid in userspace and is always false for userspace usr/include/asm/swab.h:10: leaks CONFIG_X86 to userspace where it is not valid And by headers_check tools we also able to find blunder mistakes which are very difficult to find by naked eye like: usr/include/asm-generic/fcntl.h:127: leaks CONFIG_64BIT to userspace where it is not valid for userspace this will be always false. and some files was totally covered with ifdefs CONFIG_* and exported which are useless like: usr/include/linux/if_frad.h:29: leaks CONFIG_DLCI to userspace where it is not valid > If those > > #ifdef CONFIG_XYZ > > things result in problems, then we should just make the rule be that we > turn that kind of string into > > #if 0 > This will looks ugly in userspace with so many #if 0 and make impossible to read the code. > automatically when exporting the kernel headers. IOW, just about > _anything_ that headers_check complains about automatically is something > that should just be _fixed_ automatically at header install time rather > than make the code harder to read. > > So I think it makes our headers worse. Code like > > > +#ifdef __KERNEL__ > > +# ifdef CONFIG_X86_BSWAP > > +# define __X86_BSWAP > > +# endif /* CONFIG_X86_BSWAP */ > > +#endif /* __KERNEL__ */ > > just doesn't make sense. It doesn't make sense _inside_ the kernel, and it > doesn't make sense _outside_ it either. > my earlier patch was like this: diff --git a/arch/x86/include/asm/swab.h b/arch/x86/include/asm/swab.h index 306d417..613be68 100644 --- a/arch/x86/include/asm/swab.h +++ b/arch/x86/include/asm/swab.h @@ -1,12 +1,15 @@ #ifndef _ASM_X86_SWAB_H #define _ASM_X86_SWAB_H -#include +#include +#ifdef __KERNEL__ #include +#endif /* __KERNEL__ */ static inline __attribute_const__ __u32 __arch_swab32(__u32 val) { #ifdef __i386__ +#ifdef __KERNEL__ # ifdef CONFIG_X86_BSWAP asm("bswap %0" : "=r" (val) : "0" (val)); # else @@ -16,7 +19,13 @@ static inline __attribute_const__ __u32 __arch_swab32(__u32 val) : "=q" (val) : "0" (val)); # endif - +#else /* __KERNEL__ */ + asm("xchgb %b0,%h0\n\t" /* swap lower bytes */ + "rorl $16,%0\n\t" /* swap words */ + "xchgb %b0,%h0" /* swap higher bytes */ + : "=q" (val) + : "0" (val)); +#endif /* __KERNEL__ */ #else /* __i386__ */ asm("bswapl %0" : "=r" (val) @@ -37,6 +46,7 @@ static inline __attribute_const__ __u64 __arch_swab64(__u64 val) __u64 u; } v; v.u = val; +#ifdef __KERNEL__ # ifdef CONFIG_X86_BSWAP asm("bswapl %0 ; bswapl %1 ; xchgl %0,%1" : "=r" (v.s.a), "=r" (v.s.b) @@ -48,6 +58,13 @@ static inline __attribute_const__ __u64 __arch_swab64(__u64 val) : "=r" (v.s.a), "=r" (v.s.b) : "0" (v.s.a), "1" (v.s.b)); # endif +#else /* __KERNEL__ */ + v.s.a = __arch_swab32(v.s.a); + v.s.b = __arch_swab32(v.s.b); + asm("xchgl %0,%1" + : "=r" (v.s.a), "=r" (v.s.b) + : "0" (v.s.a), "1" (v.s.b)); +#endif /* __KERNEL__ */ return v.u; #else /* __i386__ */ asm("bswapq %0" to get rid of multiple blocks so I used above technique. If we do not want to export __arch_swab32 and __arch_swab64 then we can put whole block in #ifdef __KERNEL__ then we will get rid of above solution. -- JSR -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/