include/linux/highuid.h

   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
  34 extern int overflowuid;
  35 extern int overflowgid;
  36
  37 extern void __bad_uid(void);
  38 extern 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  */
  81 extern int fs_overflowuid;
  82 extern 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 */