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
  35 extern int overflowuid;
  36 extern int overflowgid;
  37
  38 extern void __bad_uid(void);
  39 extern void __bad_gid(void);
  40
  41 #define DEFAULT_OVERFLOWUID     65534
  42 #define DEFAULT_OVERFLOWGID     65534
  43
  44 #ifdef CONFIG_UID16
  45
  46 /* prevent uid mod 65536 effect by returning a default value for high UIDs */
  47 #define high2lowuid(uid) ((uid) & ~0xFFFF ? (old_uid_t)overflowuid : (old_uid_t)(uid))
  48 #define high2lowgid(gid) ((gid) & ~0xFFFF ? (old_gid_t)overflowgid : (old_gid_t)(gid))
  49 /*
  50  * -1 is different in 16 bits than it is in 32 bits
  51  * these macros are used by chown(), setreuid(), ...,
  52  */
  53 #define low2highuid(uid) ((uid) == (old_uid_t)-1 ? (uid_t)-1 : (uid_t)(uid))
  54 #define low2highgid(gid) ((gid) == (old_gid_t)-1 ? (gid_t)-1 : (gid_t)(gid))
  55
  56 #define __convert_uid(size, uid) \
  57         (size >= sizeof(uid) ? (uid) : high2lowuid(uid))
  58 #define __convert_gid(size, gid) \
  59         (size >= sizeof(gid) ? (gid) : high2lowgid(gid))
  60
  61
  62 #else
  63
  64 #define __convert_uid(size, uid) (uid)
  65 #define __convert_gid(size, gid) (gid)
  66
  67 #endif /* !CONFIG_UID16 */
  68
  69 /* uid/gid input should be always 32bit uid_t */
  70 #define SET_UID(var, uid) do { (var) = __convert_uid(sizeof(var), (uid)); } while (0)
  71 #define SET_GID(var, gid) do { (var) = __convert_gid(sizeof(var), (gid)); } while (0)
  72
  73 /*
  74  * Everything below this line is needed on all architectures, to deal with
  75  * filesystems that only store 16 bits of the UID/GID, etc.
  76  */
  77
  78 /*
  79  * This is the UID and GID that will get written to disk if a filesystem
  80  * only supports 16-bit UIDs and the kernel has a high UID/GID to write
  81  */
  82 extern int fs_overflowuid;
  83 extern int fs_overflowgid;
  84
  85 #define DEFAULT_FS_OVERFLOWUID  65534
  86 #define DEFAULT_FS_OVERFLOWGID  65534
  87
  88 /*
  89  * Since these macros are used in architectures that only need limited
  90  * 16-bit UID back compatibility, we won't use old_uid_t and old_gid_t
  91  */
  92 #define fs_high2lowuid(uid) ((uid) & ~0xFFFF ? (uid16_t)fs_overflowuid : (uid16_t)(uid))
  93 #define fs_high2lowgid(gid) ((gid) & ~0xFFFF ? (gid16_t)fs_overflowgid : (gid16_t)(gid))
  94
  95 #define low_16_bits(x)  ((x) & 0xFFFF)
  96 #define high_16_bits(x) (((x) & 0xFFFF0000) >> 16)
  97
  98 #endif /* _LINUX_HIGHUID_H */