linux-kernel - Re: [PATCH 1/5] tools: Add err.h with ERR_PTR PTR

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Message-ID: <CAE_Gge3LESL4h154CR=G3w+8Pw4ycwB6twyJqy=qzMbNPvWkzg@mail.gmail.com>
Date:	Tue, 8 Sep 2015 17:29:46 -0400
From:	Raphaël Beamonte <raphael.beamonte@...il.com>
To:	Jiri Olsa <jolsa@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Matt Fleming <matt@...eblueprint.co.uk>
Subject: Re: [PATCH 1/5] tools: Add err.h with ERR_PTR PTR_ERR interface

2015-09-07 4:38 GMT-04:00 Jiri Olsa <jolsa@...nel.org>:
> Adding part of the kernel's <linux/err.h> 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 <jolsa@...nel.org>
> ---
>  tools/include/linux/err.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
>  create mode 100644 tools/include/linux/err.h

Reviewed-by: Raphaël Beamonte <raphael.beamonte@...il.com>

>
> 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 <linux/compiler.h>
> +#include <linux/types.h>
> +
> +#include <asm/errno.h>
> +
> +/*
> + * 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
>
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