tools: Add err.h with ERR_PTR PTR_ERR interface

#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 */