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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | KERNEL STATUS PAGE | NETLINK NOTIFICATION | RETURN VALUE | AUTHOR | SEE ALSO | COLOPHON |
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avc_open(3) SELinux API documentation avc_open(3)
avc_open, avc_destroy, avc_reset, avc_cleanup - userspace SELinux
AVC setup and teardown
#include <selinux/selinux.h>
#include <selinux/avc.h>
int avc_open(const struct selinux_opt *options, unsigned nopt);
void avc_destroy(void);
int avc_reset(void);
void avc_cleanup(void);
avc_open() initializes the userspace AVC and must be called before
any other AVC operation can be performed.
avc_destroy() destroys the userspace AVC, freeing all internal
memory structures. After this call has been made, avc_open() must
be called again before any AVC operations can be performed.
avc_destroy() also closes the SELinux status page, which might
have been opened manually by selinux_status_open(3).
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 NETLINK NOTIFICATION
below.
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.
The userspace AVC obeys callbacks set via selinux_set_callback(3),
in particular the logging and audit callbacks.
The options which may be passed to avc_open() include the
following:
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.
Linux kernel version 2.6.37 supports the SELinux kernel status
page, enabling userspace applications to mmap(2) SELinux status
state in read-only mode to avoid system calls during the cache hit
code path.
avc_open() calls selinux_status_open(3) to initialize the selinux
status state.
avc_has_perm(3) and selinux_check_access(3) both check for status
updates through calls to selinux_status_updated(3) at the start of
each permission query and take the appropriate action.
Two status types are currently implemented. setenforce events
will change the effective enforcing state used within the AVC, and
policyload events will result in a cache flush.
In the event that the kernel status page is not successfully
mmap(2)'ed the AVC will default to the netlink fallback mechanism,
which opens a netlink socket for receiving status updates.
setenforce and policyload events will have the same results as for
the status page implementation, but all status update checks will
now require a system call.
Functions with a return value return zero on success. On error,
-1 is returned and errno is set appropriately.
Eamon Walsh <ewalsh@tycho.nsa.gov>
selinux(8), selinux_check_access(3), avc_has_perm(3),
avc_context_to_sid(3), avc_cache_stats(3), avc_add_callback(3),
selinux_status_open(3), selinux_status_updated(3),
selinux_set_callback(3), security_compute_av(3)
This page is part of the selinux (Security-Enhanced Linux user-
space libraries and tools) project. Information about the project
can be found at ⟨https://github.com/SELinuxProject/selinux/wiki⟩.
If you have a bug report for this manual page, see
⟨https://github.com/SELinuxProject/selinux/wiki/Contributing⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/SELinuxProject/selinux⟩ on 2025-08-11. (At
that time, the date of the most recent commit that was found in
the repository was 2025-08-04.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
12 Jun 2008 avc_open(3)
Pages that refer to this page: avc_add_callback(3), avc_context_to_sid(3), avc_init(3), avc_netlink_loop(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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