linux-kernel - Re: [PATCH 01/11] tools: Add err.h with ERR_PTR PTR

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Message-ID: <20150828162139.GE11407@kernel.org>
Date:	Fri, 28 Aug 2015 13:21:39 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Jiri Olsa <jolsa@...nel.org>
Cc:	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>,
	Raphaël Beamonte <raphael.beamonte@...il.com>
Subject: Re: [PATCH 01/11] tools: Add err.h with ERR_PTR PTR_ERR interface

Em Wed, Aug 26, 2015 at 03:46:43PM +0200, Jiri Olsa escreveu:
> 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 | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 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..2df92df55cfe
> --- /dev/null
> +++ b/tools/include/linux/err.h
> @@ -0,0 +1,28 @@
> +#ifndef __TOOLS_LINUX_ERR_H
> +#define __TOOLS_LINUX_ERR_H
> +
> +#include <linux/compiler.h>
> +#include <linux/types.h>
> +
> +#include <asm/errno.h>
> +

You deleted the comment in the kernel sources at this point:

/*
 * 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.
 */

> +#define MAX_ERRNO	4095

Now we're dealing with user pointers, are we completely sure we can use
this trick here?

- Arnaldo

> +#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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