include/linux/namei.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_NAMEI_H
   3 #define _LINUX_NAMEI_H
   4
   5 #include <linux/fs.h>
   6 #include <linux/kernel.h>
   7 #include <linux/path.h>
   8 #include <linux/fcntl.h>
   9 #include <linux/errno.h>
  10
  11 enum { MAX_NESTED_LINKS = 8 };
  12
  13 #define MAXSYMLINKS 40
  14
  15 /*
  16  * Type of the last component on LOOKUP_PARENT
  17  */
  18 enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT};
  19
  20 /* pathwalk mode */
  21 #define LOOKUP_FOLLOW           0x0001  /* follow links at the end */
  22 #define LOOKUP_DIRECTORY        0x0002  /* require a directory */
  23 #define LOOKUP_AUTOMOUNT        0x0004  /* force terminal automount */
  24 #define LOOKUP_EMPTY            0x4000  /* accept empty path [user_... only] */
  25 #define LOOKUP_DOWN             0x8000  /* follow mounts in the starting point */
  26 #define LOOKUP_MOUNTPOINT       0x0080  /* follow mounts in the end */
  27
  28 #define LOOKUP_REVAL            0x0020  /* tell ->d_revalidate() to trust no cache */
  29 #define LOOKUP_RCU              0x0040  /* RCU pathwalk mode; semi-internal */
  30
  31 /* These tell filesystem methods that we are dealing with the final component... */
  32 #define LOOKUP_OPEN             0x0100  /* ... in open */
  33 #define LOOKUP_CREATE           0x0200  /* ... in object creation */
  34 #define LOOKUP_EXCL             0x0400  /* ... in exclusive creation */
  35 #define LOOKUP_RENAME_TARGET    0x0800  /* ... in destination of rename() */
  36
  37 /* internal use only */
  38 #define LOOKUP_PARENT           0x0010
  39
  40 /* Scoping flags for lookup. */
  41 #define LOOKUP_NO_SYMLINKS      0x010000 /* No symlink crossing. */
  42 #define LOOKUP_NO_MAGICLINKS    0x020000 /* No nd_jump_link() crossing. */
  43 #define LOOKUP_NO_XDEV          0x040000 /* No mountpoint crossing. */
  44 #define LOOKUP_BENEATH          0x080000 /* No escaping from starting point. */
  45 #define LOOKUP_IN_ROOT          0x100000 /* Treat dirfd as fs root. */
  46 #define LOOKUP_CACHED           0x200000 /* Only do cached lookup */
  47 #define LOOKUP_LINKAT_EMPTY     0x400000 /* Linkat request with empty path. */
  48 /* LOOKUP_* flags which do scope-related checks based on the dirfd. */
  49 #define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT)
  50
  51 extern int path_pts(struct path *path);
  52
  53 extern int user_path_at(int, const char __user *, unsigned, struct path *);
  54
  55 struct dentry *lookup_one_qstr_excl(const struct qstr *name,
  56                                     struct dentry *base,
  57                                     unsigned int flags);
  58 extern int kern_path(const char *, unsigned, struct path *);
  59
  60 extern struct dentry *kern_path_create(int, const char *, struct path *, unsigned int);
  61 extern struct dentry *user_path_create(int, const char __user *, struct path *, unsigned int);
  62 extern void done_path_create(struct path *, struct dentry *);
  63 extern struct dentry *kern_path_locked(const char *, struct path *);
  64 extern struct dentry *user_path_locked_at(int , const char __user *, struct path *);
  65 int vfs_path_parent_lookup(struct filename *filename, unsigned int flags,
  66                            struct path *parent, struct qstr *last, int *type,
  67                            const struct path *root);
  68 int vfs_path_lookup(struct dentry *, struct vfsmount *, const char *,
  69                     unsigned int, struct path *);
  70
  71 extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int);
  72 extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
  73 extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
  74 extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int);
  75 struct dentry *lookup_one(struct mnt_idmap *, const char *, struct dentry *, int);
  76 struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
  77                                    const char *name, struct dentry *base,
  78                                    int len);
  79 struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
  80                                             const char *name,
  81                                             struct dentry *base, int len);
  82
  83 extern int follow_down_one(struct path *);
  84 extern int follow_down(struct path *path, unsigned int flags);
  85 extern int follow_up(struct path *);
  86
  87 extern struct dentry *lock_rename(struct dentry *, struct dentry *);
  88 extern struct dentry *lock_rename_child(struct dentry *, struct dentry *);
  89 extern void unlock_rename(struct dentry *, struct dentry *);
  90
  91 /**
  92  * mode_strip_umask - handle vfs umask stripping
  93  * @dir:        parent directory of the new inode
  94  * @mode:       mode of the new inode to be created in @dir
  95  *
  96  * In most filesystems, umask stripping depends on whether or not the
  97  * filesystem supports POSIX ACLs. If the filesystem doesn't support it umask
  98  * stripping is done directly in here. If the filesystem does support POSIX
  99  * ACLs umask stripping is deferred until the filesystem calls
 100  * posix_acl_create().
 101  *
 102  * Some filesystems (like NFSv4) also want to avoid umask stripping by the
 103  * VFS, but don't support POSIX ACLs. Those filesystems can set SB_I_NOUMASK
 104  * to get this effect without declaring that they support POSIX ACLs.
 105  *
 106  * Returns: mode
 107  */
 108 static inline umode_t __must_check mode_strip_umask(const struct inode *dir, umode_t mode)
 109 {
 110         if (!IS_POSIXACL(dir) && !(dir->i_sb->s_iflags & SB_I_NOUMASK))
 111                 mode &= ~current_umask();
 112         return mode;
 113 }
 114
 115 extern int __must_check nd_jump_link(const struct path *path);
 116
 117 static inline void nd_terminate_link(void *name, size_t len, size_t maxlen)
 118 {
 119         ((char *) name)[min(len, maxlen)] = '\0';
 120 }
 121
 122 /**
 123  * retry_estale - determine whether the caller should retry an operation
 124  * @error: the error that would currently be returned
 125  * @flags: flags being used for next lookup attempt
 126  *
 127  * Check to see if the error code was -ESTALE, and then determine whether
 128  * to retry the call based on whether "flags" already has LOOKUP_REVAL set.
 129  *
 130  * Returns true if the caller should try the operation again.
 131  */
 132 static inline bool
 133 retry_estale(const long error, const unsigned int flags)
 134 {
 135         return unlikely(error == -ESTALE && !(flags & LOOKUP_REVAL));
 136 }
 137
 138 #endif /* _LINUX_NAMEI_H */