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avc_open(3) — Linux manual page

avc_open(3)             SELinux API documentationavc_open(3)

NAME        top

       avc_open, avc_destroy, avc_reset, avc_cleanup - userspace SELinux       AVC setup and teardown

SYNOPSIS        top

#include <selinux/selinux.h>#include <selinux/avc.h>int avc_open(const struct selinux_opt *options, unsignednopt);void avc_destroy(void);int avc_reset(void);void avc_cleanup(void);

DESCRIPTION        top

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 byselinux_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, seeNETLINK 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.

OPTIONS        top

       The userspace AVC obeys callbacks set viaselinux_set_callback(3),       in particular the logging and audit callbacks.       The options which may be passed toavc_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.

KERNEL STATUS PAGE        top

       Linux kernel version 2.6.37 supports the SELinux kernel status       page, enabling userspace applications tommap(2) SELinux status       state in read-only mode to avoid system calls during the cache hit       code path.avc_open() callsselinux_status_open(3) to initialize the selinux       status state.avc_has_perm(3) andselinux_check_access(3) both check for status       updates through calls toselinux_status_updated(3) at the start of       each permission query and take the appropriate action.       Two status types are currently implemented.setenforceevents       will change the effective enforcing state used within the AVC, andpolicyloadevents will result in a cache flush.

NETLINK NOTIFICATION        top

       In the event that the kernel status page is not successfullymmap(2)'ed the AVC will default to the netlink fallback mechanism,       which opens a netlink socket for receiving status updates.setenforceandpolicyloadevents will have the same results as for       the status page implementation, but all status update checks will       now require a system call.

RETURN VALUE        top

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

AUTHOR        top

       Eamon Walsh <ewalsh@tycho.nsa.gov>

SEE ALSO        top

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)

COLOPHON        top

       This page is part of theselinux (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 isnot part of the original manual page), send a mail to       man-pages@man7.org                               12 Jun 2008avc_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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