LXR linux-old/include/linux/highuid.h

   1#ifndef _LINUX_HIGHUID_H
   2#define _LINUX_HIGHUID_H
   3
   4#include <linux/config.h>
   5#include <linux/types.h>
   6
   7/*
   8 * general notes:
   9 *
  10 * CONFIG_UID16 is defined if the given architecture needs to
  11 * support backwards compatibility for old system calls.
  12 *
  13 * kernel code should use uid_t and gid_t at all times when dealing with
  14 * kernel-private data.
  15 *
  16 * old_uid_t and old_gid_t should only be different if CONFIG_UID16 is
  17 * defined, else the platform should provide dummy typedefs for them
  18 * such that they are equivalent to __kernel_{u,g}id_t.
  19 *
  20 * uid16_t and gid16_t are used on all architectures. (when dealing
  21 * with structures hard coded to 16 bits, such as in filesystems)
  22 */
  23
  24
  25/*
  26 * This is the "overflow" UID and GID. They are used to signify uid/gid
  27 * overflow to old programs when they request uid/gid information but are
  28 * using the old 16 bit interfaces.
  29 * When you run a libc5 program, it will think that all highuid files or
  30 * processes are owned by this uid/gid.
  31 * The idea is that it's better to do so than possibly return 0 in lieu of
  32 * 65536, etc.
  33 */
  34
  35extern int overflowuid;
  36extern int overflowgid;
  37
  38#define DEFAULT_OVERFLOWUID     65534
  39#define DEFAULT_OVERFLOWGID     65534
  40
  41#ifdef CONFIG_UID16
  42
  43/* prevent uid mod 65536 effect by returning a default value for high UIDs */
  44#define high2lowuid(uid) ((uid) > 65535 ? (old_uid_t)overflowuid : (old_uid_t)(uid))
  45#define high2lowgid(gid) ((gid) > 65535 ? (old_gid_t)overflowgid : (old_gid_t)(gid))
  46/*
  47 * -1 is different in 16 bits than it is in 32 bits
  48 * these macros are used by chown(), setreuid(), ...,
  49 */
  50#define low2highuid(uid) ((uid) == (old_uid_t)-1 ? (uid_t)-1 : (uid_t)(uid))
  51#define low2highgid(gid) ((gid) == (old_gid_t)-1 ? (gid_t)-1 : (gid_t)(gid))
  52
  53/* Avoid extra ifdefs with these macros */
  54
  55#define SET_UID16(var, uid)     var = high2lowuid(uid)
  56#define SET_GID16(var, gid)     var = high2lowgid(gid)
  57#define NEW_TO_OLD_UID(uid)     high2lowuid(uid)
  58#define NEW_TO_OLD_GID(gid)     high2lowgid(gid)
  59
  60/* specific to fs/stat.c */
  61#define SET_OLDSTAT_UID(stat, uid)      (stat).st_uid = high2lowuid(uid)
  62#define SET_OLDSTAT_GID(stat, gid)      (stat).st_gid = high2lowgid(gid)
  63#define SET_STAT_UID(stat, uid)         (stat).st_uid = high2lowuid(uid)
  64#define SET_STAT_GID(stat, gid)         (stat).st_gid = high2lowgid(gid)
  65
  66#else
  67
  68#define SET_UID16(var, uid)     do { ; } while (0)
  69#define SET_GID16(var, gid)     do { ; } while (0)
  70#define NEW_TO_OLD_UID(uid)     (uid)
  71#define NEW_TO_OLD_GID(gid)     (gid)
  72
  73#define SET_OLDSTAT_UID(stat, uid)      (stat).st_uid = (uid)
  74#define SET_OLDSTAT_GID(stat, gid)      (stat).st_gid = (gid)
  75#define SET_STAT_UID(stat, uid)         (stat).st_uid = (uid)
  76#define SET_STAT_GID(stat, gid)         (stat).st_gid = (gid)
  77
  78#endif /* CONFIG_UID16 */
  79
  80
  81/*
  82 * Everything below this line is needed on all architectures, to deal with
  83 * filesystems that only store 16 bits of the UID/GID, etc.
  84 */
  85
  86/*
  87 * This is the UID and GID that will get written to disk if a filesystem
  88 * only supports 16-bit UIDs and the kernel has a high UID/GID to write
  89 */
  90extern int fs_overflowuid;
  91extern int fs_overflowgid;
  92
  93#define DEFAULT_FS_OVERFLOWUID  65534
  94#define DEFAULT_FS_OVERFLOWGID  65534
  95
  96/*
  97 * Since these macros are used in architectures that only need limited
  98 * 16-bit UID back compatibility, we won't use old_uid_t and old_gid_t
  99 */
 100#define fs_high2lowuid(uid) ((uid) > 65535 ? (uid16_t)fs_overflowuid : (uid16_t)(uid))
 101#define fs_high2lowgid(gid) ((gid) > 65535 ? (gid16_t)fs_overflowgid : (gid16_t)(gid))
 102
 103#define low_16_bits(x)  ((x) & 0xFFFF)
 104#define high_16_bits(x) (((x) & 0xFFFF0000) >> 16)
 105
 106#endif /* _LINUX_HIGHUID_H */
 107