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 #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 */ 90 extern int fs_overflowuid; 91 extern 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