From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753412AbbIHV3R (ORCPT ); Tue, 8 Sep 2015 17:29:17 -0400 Received: from mail-yk0-f173.google.com ([209.85.160.173]:34904 "EHLO mail-yk0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752155AbbIHV3P convert rfc822-to-8bit (ORCPT ); Tue, 8 Sep 2015 17:29:15 -0400 MIME-Version: 1.0 In-Reply-To: <20150908210652.GR3475@kernel.org> References: <1441615087-13886-1-git-send-email-jolsa@kernel.org> <1441615087-13886-2-git-send-email-jolsa@kernel.org> <20150908210652.GR3475@kernel.org> From: =?UTF-8?Q?Rapha=C3=ABl_Beamonte?= Date: Tue, 8 Sep 2015 17:28:55 -0400 X-Google-Sender-Auth: De4FM_6rec3WFnRoqo4YvCFpISo Message-ID: Subject: Re: [PATCH 1/5] tools: Add err.h with ERR_PTR PTR_ERR interface To: Arnaldo Carvalho de Melo Cc: Jiri Olsa , lkml , David Ahern , Ingo Molnar , Namhyung Kim , Peter Zijlstra , Matt Fleming Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2015-09-08 17:06 GMT-04:00 Arnaldo Carvalho de Melo : > Em Tue, Sep 08, 2015 at 04:22:39PM -0400, Raphaël Beamonte escreveu: >> 2015-09-07 4:38 GMT-04:00 Jiri Olsa : >> > Adding part of the kernel's interface: >> > inline void * __must_check ERR_PTR(long error); >> > inline long __must_check PTR_ERR(__force const void *ptr); >> > inline bool __must_check IS_ERR(__force const void *ptr); >> > >> > it will be used to propagate error through pointers >> > in following patches. >> > >> > Link: http://lkml.kernel.org/n/tip-ufgnyf683uab69anmmrabgdf@git.kernel.org >> > Signed-off-by: Jiri Olsa >> > --- >> > tools/include/linux/err.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++ >> > 1 file changed, 49 insertions(+) >> > create mode 100644 tools/include/linux/err.h >> > >> > diff --git a/tools/include/linux/err.h b/tools/include/linux/err.h >> > new file mode 100644 >> > index 000000000000..c9ada48f5156 >> > --- /dev/null >> > +++ b/tools/include/linux/err.h >> > @@ -0,0 +1,49 @@ >> > +#ifndef __TOOLS_LINUX_ERR_H >> > +#define __TOOLS_LINUX_ERR_H >> > + >> > +#include >> > +#include >> > + >> > +#include >> > + >> > +/* >> > + * Original kernel header comment: >> > + * >> > + * Kernel pointers have redundant information, so we can use a >> > + * scheme where we can return either an error code or a normal >> > + * pointer with the same return value. >> > + * >> > + * This should be a per-architecture thing, to allow different >> > + * error and pointer decisions. >> > + * >> > + * Userspace note: >> > + * The same principle works for userspace, because 'error' pointers >> > + * fall down to the unused hole far from user space, as described >> > + * in Documentation/x86/x86_64/mm.txt for x86_64 arch: >> > + * >> > + * 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm hole caused by [48:63] sign extension >> > + * ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole >> > + * >> > + * It should be the same case for other architectures, because >> > + * this code is used in generic kernel code. >> > + */ >> > +#define MAX_ERRNO 4095 >> > + >> > +#define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO) >> > + >> > +static inline void * __must_check ERR_PTR(long error) >> > +{ >> > + return (void *) error; >> > +} >> > + >> > +static inline long __must_check PTR_ERR(__force const void *ptr) >> > +{ >> > + return (long) ptr; >> > +} >> > + >> > +static inline bool __must_check IS_ERR(__force const void *ptr) >> > +{ >> > + return IS_ERR_VALUE((unsigned long)ptr); >> > +} >> > + >> > +#endif /* _LINUX_ERR_H */ >> > -- >> > 2.4.3 >> >> Perhaps a dumb question, but it seems the code is exactly the same as >> in linux/err.h besides the part of the comment you added. Why not >> using that file directly in the other patches then? > > We can't do that. > > Read: > > commit 3f735377bfd6567d80815a6242c147211963680a > Author: Arnaldo Carvalho de Melo > Date: Sun Jul 5 22:48:21 2015 -0300 > > tools: Copy lib/rbtree.c to tools/lib/ > > So that we can remove kernel specific stuff we've been stubbing out via > a tools/include/linux/export.h that gets removed in this patch and to > avoid breakages in the future like the one fixed recently where > rcupdate.h started being used in rbtree.h. > > > -------------------------- > > There are more copies like that, but the explanation above should be > enough, no? Yes, I understand now! Thanks! > > > - Arnaldo