.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Author: Eamon Walsh (ewalsh@tycho.nsa.gov) 2008
.TH "avc_open" "3" "12 Jun 2008" "" "SELinux API documentation"
.SH "NAME"
avc_open, avc_destroy, avc_reset, avc_cleanup \- userspace SELinux AVC setup and teardown
.
.SH "SYNOPSIS"
.B #include <selinux/selinux.h>
.br
.B #include <selinux/avc.h>
.sp
.BI "int avc_open(struct selinux_opt *" options ", unsigned " nopt ");"
.sp
.BI "void avc_destroy(void);"
.sp
.BI "int avc_reset(void);"
.sp
.BI "void avc_cleanup(void);"
.
.SH "DESCRIPTION"
.BR avc_open ()
initializes the userspace AVC and must be called before any other AVC operation can be performed.

.BR avc_destroy ()
destroys the userspace AVC, freeing all internal memory structures.  After this call has been made, 
.BR avc_open ()
must be called again before any AVC operations can be performed.
.BR avc_destroy ()
also closes the SELinux status page, which might have been opened manually by
.BR selinux_status_open (3).

.BR avc_reset ()
flushes the userspace AVC, causing it to forget any cached access decisions.  The userspace AVC normally calls this function automatically when needed, see
.B NETLINK NOTIFICATION
below.

.BR avc_cleanup ()
attempts to free unused memory within the userspace AVC, but does not flush any cached access decisions.  Under normal operation, calling this function should not be necessary.
.SH "OPTIONS"
The userspace AVC obeys callbacks set via
.BR selinux_set_callback (3),
in particular the logging and audit callbacks.

The options which may be passed to
.BR avc_open ()
include the following:
.TP
.B AVC_OPT_SETENFORCE
This option forces the userspace AVC into enforcing mode if the option value is non-NULL; permissive mode otherwise.  The system enforcing mode will be ignored.
.
.SH "KERNEL STATUS PAGE"
Linux kernel version 2.6.37 supports the SELinux kernel status page, enabling userspace applications to
.BR mmap (2)
SELinux status state in read-only mode to avoid system calls during the cache hit code path.

.BR avc_open ()
calls
.BR selinux_status_open (3)
to initialize the selinux status state.

.BR avc_has_perm (3)
and
.BR selinux_check_access (3)
both check for status updates through calls to
.BR selinux_status_updated (3)
at the start of each permission query and take the appropriate action.

Two status types are currently implemented.
.B setenforce
events will change the effective enforcing state used within the AVC, and
.B policyload
events will result in a cache flush.
.
.SH "NETLINK NOTIFICATION"
In the event that the kernel status page is not successfully
.BR mmap (2)'ed
the AVC will default to the netlink fallback mechanism, which opens a netlink socket for receiving status updates.
.B setenforce
and
.B policyload
events will have the same results as for the status page implementation, but all status update checks will now require a system call.
.
.SH "RETURN VALUE"
Functions with a return value return zero on success.  On error, \-1 is returned and
.I errno
is set appropriately.
.
.SH "AUTHOR"
Eamon Walsh <ewalsh@tycho.nsa.gov>
.
.SH "SEE ALSO"
.BR selinux (8),
.BR selinux_check_access (3),
.BR avc_has_perm (3),
.BR avc_context_to_sid (3),
.BR avc_cache_stats (3),
.BR avc_add_callback (3),
.BR selinux_status_open (3),
.BR selinux_status_updated (3),
.BR selinux_set_callback (3),
.BR security_compute_av (3)