LXR linux/include/linux/highuid.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef _LINUX_HIGHUID_H
   3#define _LINUX_HIGHUID_H
   4
   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
  38extern void __bad_uid(void);
  39extern 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 */
  82extern int fs_overflowuid;
  83extern 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 */
  99