NAME

       avc_init - legacy userspace SELinux AVC setup

SYNOPSIS

       #include <selinux/selinux.h>
       #include <selinux/avc.h>

       int avc_init(const char *msgprefix,
                    const struct avc_memory_callback *mem_callbacks,
                    const struct avc_log_callback *log_callbacks,
                    const struct avc_thread_callback *thread_callbacks,
                    const struct avc_lock_callback *lock_callbacks);

DESCRIPTION

       avc_init()    is    deprecated;    please    use    avc_open(3)    in   conjunction   with
       selinux_set_callback(3) in all new code.

       avc_init() initializes the userspace AVC and must be called before any other AVC operation
       can  be  performed.  A non-NULL msgprefix will be prepended to all audit messages produced
       by the userspace AVC.  The default is  `uavc'.   The  remaining  arguments,  if  non-NULL,
       specify callbacks to be used by the userspace AVC.

CALLBACKS

       The  userspace  AVC  can  be  directed  how  to perform memory allocation, logging, thread
       creation, and locking via callback functions passed to avc_init().  The  purpose  of  this
       functionality  is  to  allow  the  userspace  AVC  to be smoothly integrated into existing
       userspace object managers.

       Use an avc_memory_callback structure to specify alternate  functions  for  dynamic  memory
       allocation.

              struct avc_memory_callback {
                  void  *(*func_malloc)(size_t size);
                  void  (*func_free)(void *ptr);
              };

       The  two fields of the structure should be pointers to functions which behave as malloc(3)
       and free(3), which are used by default.

       Use an avc_log_callback structure to specify alternate functions for logging.

              struct avc_log_callback {
                  void  (*func_log)(const char *fmt, ...);
                  void  (*func_audit)(void *auditdata,
                                      security_class_t class,
                                      char *msgbuf, size_t msgbufsize);
              };

       The func_log callback should accept a printf(3) style format and arguments and log them as
       desired.   The  default behavior prints the message on the standard error.  The func_audit
       callback should interpret the auditdata parameter for the given class, printing  a  human-
       readable  interpretation  to msgbuf using no more than msgbufsize characters.  The default
       behavior is to ignore auditdata.

       Use an avc_thread_callback structure to specify functions for  starting  and  manipulating
       threads.

              struct avc_thread_callback {
                  void  *(*func_create_thread)(void (*run)(void));
                  void  (*func_stop_thread)(void *thread);
              };

       The  func_create_thread  callback  should  create  a new thread and return a pointer which
       references it.  The thread should execute the run argument, which does  not  return  under
       normal  conditions.   The  func_stop_thread  callback  should  cancel  the  running thread
       referenced by thread.  By default, threading is not used; see NETLINK NOTIFICATION below.

       Use an avc_lock_callback structure to specify functions to  create,  obtain,  and  release
       locks for use by threads.

              struct avc_lock_callback {
                  void  *(*func_alloc_lock)(void);
                  void  (*func_get_lock)(void *lock);
                  void  (*func_release_lock)(void *lock);
                  void  (*func_free_lock)(void *lock);
              };

       The  func_alloc_lock  callback  should  create  a  new  lock,  returning  a  pointer which
       references it.  The func_get_lock callback should obtain lock, blocking if necessary.  The
       func_release_lock  callback  should  release  lock.   The  func_free_lock  callback should
       destroy lock, freeing any resources associated with it.  The default behavior  is  not  to
       perform any locking.  Note that undefined behavior may result if threading is used without
       appropriate locking.

NETLINK NOTIFICATION

       Beginning with version 2.6.4, the Linux kernel supports SELinux status change notification
       via  netlink.   Two  message  types  are  currently implemented, indicating changes to the
       enforcing mode and to the loaded policy in the kernel, respectively.   The  userspace  AVC
       listens  for  these  messages  and takes the appropriate action, modifying the behavior of
       avc_has_perm(3) to reflect the current enforcing mode and flushing the cache on receipt of
       a  policy  load  notification.  Audit messages are produced when netlink notifications are
       processed.

       In the default single-threaded mode, the userspace AVC checks for new netlink messages  at
       the  start  of  each  permission  query.  If threading and locking callbacks are passed to
       avc_init() however, a dedicated thread will be started to listen on  the  netlink  socket.
       This  may increase performance and will ensure that log messages are generated immediately
       rather than at the time of the next permission query.

RETURN VALUE

       Functions with a return value return zero on success.  On error, -1 is returned and  errno
       is set appropriately.

NOTES

       The  msgprefix  argument  to  avc_init() currently has a length limit of 15 characters and
       will be truncated if necessary.

       If a provided func_malloc callback does not set errno appropriately  on  error,  userspace
       AVC calls may exhibit the same behavior.

       If  a netlink thread has been created and an error occurs on the socket (such as an access
       error), the thread may terminate and cause the userspace  AVC  to  return  EINVAL  on  all
       further permission checks until avc_destroy is called.

AUTHOR

       Eamon Walsh <ewalsh@tycho.nsa.gov>

SEE ALSO

       avc_open(3), selinux_set_callback(3), selinux(8)

                                           27 May 2004                                avc_init(3)