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avc_init(3)                SELinux API documentation               avc_init(3)



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 audit-
       data parameter for the given class, printing a human-readable interpretation to msgbuf using no more than  msg-
       bufsize 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, modi-
       fying 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 nec-
       essary.

       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 <ewalshATtycho.gov>


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




                                  27 May 2004                      avc_init(3)