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kernel add
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#ifndef _LINUX_HIGHUID_H
#define _LINUX_HIGHUID_H
#include <linux/types.h>
/*
* general notes:
*
* CONFIG_UID16 is defined if the given architecture needs to
* support backwards compatibility for old system calls.
*
* kernel code should use uid_t and gid_t at all times when dealing with
* kernel-private data.
*
* old_uid_t and old_gid_t should only be different if CONFIG_UID16 is
* defined, else the platform should provide dummy typedefs for them
* such that they are equivalent to __kernel_{u,g}id_t.
*
* uid16_t and gid16_t are used on all architectures. (when dealing
* with structures hard coded to 16 bits, such as in filesystems)
*/
/*
* This is the "overflow" UID and GID. They are used to signify uid/gid
* overflow to old programs when they request uid/gid information but are
* using the old 16 bit interfaces.
* When you run a libc5 program, it will think that all highuid files or
* processes are owned by this uid/gid.
* The idea is that it's better to do so than possibly return 0 in lieu of
* 65536, etc.
*/
extern int overflowuid;
extern int overflowgid;
extern void __bad_uid(void);
extern void __bad_gid(void);
#define DEFAULT_OVERFLOWUID 65534
#define DEFAULT_OVERFLOWGID 65534
#ifdef CONFIG_UID16
/* prevent uid mod 65536 effect by returning a default value for high UIDs */
#define high2lowuid(uid) ((uid) & ~0xFFFF ? (old_uid_t)overflowuid : (old_uid_t)(uid))
#define high2lowgid(gid) ((gid) & ~0xFFFF ? (old_gid_t)overflowgid : (old_gid_t)(gid))
/*
* -1 is different in 16 bits than it is in 32 bits
* these macros are used by chown(), setreuid(), ...,
*/
#define low2highuid(uid) ((uid) == (old_uid_t)-1 ? (uid_t)-1 : (uid_t)(uid))
#define low2highgid(gid) ((gid) == (old_gid_t)-1 ? (gid_t)-1 : (gid_t)(gid))
#define __convert_uid(size, uid) \
(size >= sizeof(uid) ? (uid) : high2lowuid(uid))
#define __convert_gid(size, gid) \
(size >= sizeof(gid) ? (gid) : high2lowgid(gid))
#else
#define __convert_uid(size, uid) (uid)
#define __convert_gid(size, gid) (gid)
#endif /* !CONFIG_UID16 */
/* uid/gid input should be always 32bit uid_t */
#define SET_UID(var, uid) do { (var) = __convert_uid(sizeof(var), (uid)); } while (0)
#define SET_GID(var, gid) do { (var) = __convert_gid(sizeof(var), (gid)); } while (0)
/*
* Everything below this line is needed on all architectures, to deal with
* filesystems that only store 16 bits of the UID/GID, etc.
*/
/*
* This is the UID and GID that will get written to disk if a filesystem
* only supports 16-bit UIDs and the kernel has a high UID/GID to write
*/
extern int fs_overflowuid;
extern int fs_overflowgid;
#define DEFAULT_FS_OVERFLOWUID 65534
#define DEFAULT_FS_OVERFLOWGID 65534
/*
* Since these macros are used in architectures that only need limited
* 16-bit UID back compatibility, we won't use old_uid_t and old_gid_t
*/
#define fs_high2lowuid(uid) ((uid) & ~0xFFFF ? (uid16_t)fs_overflowuid : (uid16_t)(uid))
#define fs_high2lowgid(gid) ((gid) & ~0xFFFF ? (gid16_t)fs_overflowgid : (gid16_t)(gid))
#define low_16_bits(x) ((x) & 0xFFFF)
#define high_16_bits(x) (((x) & 0xFFFF0000) >> 16)
#endif /* _LINUX_HIGHUID_H */
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