posix_acl.h

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/*
  File: linux/posix_acl.h

  (C) 2002 Andreas Gruenbacher, <[email protected]>
*/


#ifndef __LINUX_POSIX_ACL_H
#define __LINUX_POSIX_ACL_H

#include <linux/bug.h>
#include <linux/slab.h>
#include <linux/rcupdate.h>

#define ACL_UNDEFINED_ID    (-1)

/* a_type field in acl_user_posix_entry_t */
#define ACL_TYPE_ACCESS     (0x8000)
#define ACL_TYPE_DEFAULT    (0x4000)

/* e_tag entry in struct posix_acl_entry */
#define ACL_USER_OBJ        (0x01)
#define ACL_USER        (0x02)
#define ACL_GROUP_OBJ       (0x04)
#define ACL_GROUP       (0x08)
#define ACL_MASK        (0x10)
#define ACL_OTHER       (0x20)

/* permissions in the e_perm field */
#define ACL_READ        (0x04)
#define ACL_WRITE       (0x02)
#define ACL_EXECUTE     (0x01)
//#define ACL_ADD       (0x08)
//#define ACL_DELETE        (0x10)

struct posix_acl_entry {
    short           e_tag;
    unsigned short      e_perm;
    union {
        kuid_t      e_uid;
        kgid_t      e_gid;
#ifndef CONFIG_UIDGID_STRICT_TYPE_CHECKS
        unsigned int    e_id;
#endif
    };
};

struct posix_acl {
    union {
        atomic_t        a_refcount;
        struct rcu_head     a_rcu;
    };
    unsigned int        a_count;
    struct posix_acl_entry  a_entries[0];
};

#define FOREACH_ACL_ENTRY(pa, acl, pe) \
    for(pa=(acl)->a_entries, pe=pa+(acl)->a_count; pa<pe; pa++)


/*
 * Duplicate an ACL handle.
 */
static inline struct posix_acl *
posix_acl_dup(struct posix_acl *acl)
{
    if (acl)
        atomic_inc(&acl->a_refcount);
    return acl;
}

/*
 * Free an ACL handle.
 */
static inline void
posix_acl_release(struct posix_acl *acl)
{
    if (acl && atomic_dec_and_test(&acl->a_refcount))
        kfree_rcu(acl, a_rcu);
}


/* posix_acl.c */

extern void posix_acl_init(struct posix_acl *, int);
extern struct posix_acl *posix_acl_alloc(int, gfp_t);
extern int posix_acl_valid(const struct posix_acl *);
extern int posix_acl_permission(struct inode *, const struct posix_acl *, int);
extern struct posix_acl *posix_acl_from_mode(umode_t, gfp_t);
extern int posix_acl_equiv_mode(const struct posix_acl *, umode_t *);
extern int posix_acl_create(struct posix_acl **, gfp_t, umode_t *);
extern int posix_acl_chmod(struct posix_acl **, gfp_t, umode_t);

extern struct posix_acl *get_posix_acl(struct inode *, int);
extern int set_posix_acl(struct inode *, int, struct posix_acl *);

#ifdef CONFIG_FS_POSIX_ACL
static inline struct posix_acl **acl_by_type(struct inode *inode, int type)
{
    switch (type) {
    case ACL_TYPE_ACCESS:
        return &inode->i_acl;
    case ACL_TYPE_DEFAULT:
        return &inode->i_default_acl;
    default:
        BUG();
    }
}

static inline struct posix_acl *get_cached_acl(struct inode *inode, int type)
{
    struct posix_acl **p = acl_by_type(inode, type);
    struct posix_acl *acl = ACCESS_ONCE(*p);
    if (acl) {
        spin_lock(&inode->i_lock);
        acl = *p;
        if (acl != ACL_NOT_CACHED)
            acl = posix_acl_dup(acl);
        spin_unlock(&inode->i_lock);
    }
    return acl;
}

static inline struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
{
    return rcu_dereference(*acl_by_type(inode, type));
}

static inline void set_cached_acl(struct inode *inode,
                  int type,
                  struct posix_acl *acl)
{
    struct posix_acl **p = acl_by_type(inode, type);
    struct posix_acl *old;
    spin_lock(&inode->i_lock);
    old = *p;
    rcu_assign_pointer(*p, posix_acl_dup(acl));
    spin_unlock(&inode->i_lock);
    if (old != ACL_NOT_CACHED)
        posix_acl_release(old);
}

static inline void forget_cached_acl(struct inode *inode, int type)
{
    struct posix_acl **p = acl_by_type(inode, type);
    struct posix_acl *old;
    spin_lock(&inode->i_lock);
    old = *p;
    *p = ACL_NOT_CACHED;
    spin_unlock(&inode->i_lock);
    if (old != ACL_NOT_CACHED)
        posix_acl_release(old);
}

static inline void forget_all_cached_acls(struct inode *inode)
{
    struct posix_acl *old_access, *old_default;
    spin_lock(&inode->i_lock);
    old_access = inode->i_acl;
    old_default = inode->i_default_acl;
    inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
    spin_unlock(&inode->i_lock);
    if (old_access != ACL_NOT_CACHED)
        posix_acl_release(old_access);
    if (old_default != ACL_NOT_CACHED)
        posix_acl_release(old_default);
}
#endif

static inline void cache_no_acl(struct inode *inode)
{
#ifdef CONFIG_FS_POSIX_ACL
    inode->i_acl = NULL;
    inode->i_default_acl = NULL;
#endif
}

#endif  /* __LINUX_POSIX_ACL_H */