linux/include/linux/highuid.h
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   1#ifndef _LINUX_HIGHUID_H
   2#define _LINUX_HIGHUID_H
   3
   4#include <linux/types.h>
   5
   6/*
   7 * general notes:
   8 *
   9 * CONFIG_UID16 is defined if the given architecture needs to
  10 * support backwards compatibility for old system calls.
  11 *
  12 * kernel code should use uid_t and gid_t at all times when dealing with
  13 * kernel-private data.
  14 *
  15 * old_uid_t and old_gid_t should only be different if CONFIG_UID16 is
  16 * defined, else the platform should provide dummy typedefs for them
  17 * such that they are equivalent to __kernel_{u,g}id_t.
  18 *
  19 * uid16_t and gid16_t are used on all architectures. (when dealing
  20 * with structures hard coded to 16 bits, such as in filesystems)
  21 */
  22
  23
  24/*
  25 * This is the "overflow" UID and GID. They are used to signify uid/gid
  26 * overflow to old programs when they request uid/gid information but are
  27 * using the old 16 bit interfaces.
  28 * When you run a libc5 program, it will think that all highuid files or
  29 * processes are owned by this uid/gid.
  30 * The idea is that it's better to do so than possibly return 0 in lieu of
  31 * 65536, etc.
  32 */
  33
  34extern int overflowuid;
  35extern int overflowgid;
  36
  37extern void __bad_uid(void);
  38extern void __bad_gid(void);
  39
  40#define DEFAULT_OVERFLOWUID     65534
  41#define DEFAULT_OVERFLOWGID     65534
  42
  43#ifdef CONFIG_UID16
  44
  45/* prevent uid mod 65536 effect by returning a default value for high UIDs */
  46#define high2lowuid(uid) ((uid) & ~0xFFFF ? (old_uid_t)overflowuid : (old_uid_t)(uid))
  47#define high2lowgid(gid) ((gid) & ~0xFFFF ? (old_gid_t)overflowgid : (old_gid_t)(gid))
  48/*
  49 * -1 is different in 16 bits than it is in 32 bits
  50 * these macros are used by chown(), setreuid(), ...,
  51 */
  52#define low2highuid(uid) ((uid) == (old_uid_t)-1 ? (uid_t)-1 : (uid_t)(uid))
  53#define low2highgid(gid) ((gid) == (old_gid_t)-1 ? (gid_t)-1 : (gid_t)(gid))
  54
  55#define __convert_uid(size, uid) \
  56        (size >= sizeof(uid) ? (uid) : high2lowuid(uid))
  57#define __convert_gid(size, gid) \
  58        (size >= sizeof(gid) ? (gid) : high2lowgid(gid))
  59        
  60
  61#else
  62
  63#define __convert_uid(size, uid) (uid)
  64#define __convert_gid(size, gid) (gid)
  65
  66#endif /* !CONFIG_UID16 */
  67
  68/* uid/gid input should be always 32bit uid_t */
  69#define SET_UID(var, uid) do { (var) = __convert_uid(sizeof(var), (uid)); } while (0)
  70#define SET_GID(var, gid) do { (var) = __convert_gid(sizeof(var), (gid)); } while (0)
  71
  72/*
  73 * Everything below this line is needed on all architectures, to deal with
  74 * filesystems that only store 16 bits of the UID/GID, etc.
  75 */
  76
  77/*
  78 * This is the UID and GID that will get written to disk if a filesystem
  79 * only supports 16-bit UIDs and the kernel has a high UID/GID to write
  80 */
  81extern int fs_overflowuid;
  82extern int fs_overflowgid;
  83
  84#define DEFAULT_FS_OVERFLOWUID  65534
  85#define DEFAULT_FS_OVERFLOWGID  65534
  86
  87/*
  88 * Since these macros are used in architectures that only need limited
  89 * 16-bit UID back compatibility, we won't use old_uid_t and old_gid_t
  90 */
  91#define fs_high2lowuid(uid) ((uid) & ~0xFFFF ? (uid16_t)fs_overflowuid : (uid16_t)(uid))
  92#define fs_high2lowgid(gid) ((gid) & ~0xFFFF ? (gid16_t)fs_overflowgid : (gid16_t)(gid))
  93
  94#define low_16_bits(x)  ((x) & 0xFFFF)
  95#define high_16_bits(x) (((x) & 0xFFFF0000) >> 16)
  96
  97#endif /* _LINUX_HIGHUID_H */
  98
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