root/fs/xattr_acl.c

DEFINITIONS

1. posix_acl_from_xattr
2. posix_acl_to_xattr

/*
 * linux/fs/xattr_acl.c
 *
 * Almost all from linux/fs/ext2/acl.c:
 * Copyright (C) 2001 by Andreas Gruenbacher, <a.gruenbacher@computer.org>
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/posix_acl_xattr.h>


/*
 * Convert from extended attribute to in-memory representation.
 */
struct posix_acl *
posix_acl_from_xattr(const void *value, size_t size)
{
        posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
        posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
        int count;
        struct posix_acl *acl;
        struct posix_acl_entry *acl_e;

        if (!value)
                return NULL;
        if (size < sizeof(posix_acl_xattr_header))
                 return ERR_PTR(-EINVAL);
        if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
                return ERR_PTR(-EOPNOTSUPP);

        count = posix_acl_xattr_count(size);
        if (count < 0)
                return ERR_PTR(-EINVAL);
        if (count == 0)
                return NULL;
        
        acl = posix_acl_alloc(count, GFP_KERNEL);
        if (!acl)
                return ERR_PTR(-ENOMEM);
        acl_e = acl->a_entries;
        
        for (end = entry + count; entry != end; acl_e++, entry++) {
                acl_e->e_tag  = le16_to_cpu(entry->e_tag);
                acl_e->e_perm = le16_to_cpu(entry->e_perm);

                switch(acl_e->e_tag) {
                        case ACL_USER_OBJ:
                        case ACL_GROUP_OBJ:
                        case ACL_MASK:
                        case ACL_OTHER:
                                acl_e->e_id = ACL_UNDEFINED_ID;
                                break;

                        case ACL_USER:
                        case ACL_GROUP:
                                acl_e->e_id = le32_to_cpu(entry->e_id);
                                break;

                        default:
                                goto fail;
                }
        }
        return acl;

fail:
        posix_acl_release(acl);
        return ERR_PTR(-EINVAL);
}
EXPORT_SYMBOL (posix_acl_from_xattr);

/*
 * Convert from in-memory to extended attribute representation.
 */
int
posix_acl_to_xattr(const struct posix_acl *acl, void *buffer, size_t size)
{
        posix_acl_xattr_header *ext_acl = (posix_acl_xattr_header *)buffer;
        posix_acl_xattr_entry *ext_entry = ext_acl->a_entries;
        int real_size, n;

        real_size = posix_acl_xattr_size(acl->a_count);
        if (!buffer)
                return real_size;
        if (real_size > size)
                return -ERANGE;
        
        ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);

        for (n=0; n < acl->a_count; n++, ext_entry++) {
                ext_entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
                ext_entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
                ext_entry->e_id   = cpu_to_le32(acl->a_entries[n].e_id);
        }
        return real_size;
}
EXPORT_SYMBOL (posix_acl_to_xattr);