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       avc_init - legacy userspace SELinux AVC setup.


       #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);


       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.


       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

              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

       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.


       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.


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


       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.


       Eamon Walsh <>


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

                                  27 May 2004                      avc_init(3)