avc_init man page on Oracle

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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 call‐
       backs 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 argu‐
       ments 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	 argu‐
       ment,   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 per‐
       form 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)
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