selinux_status_open(3) SELinux API documentation selinux_status_open(3)
selinux_status_open, selinux_status_close, selinux_status_updated, selinux_status_getenforce, selinux_status_policyload and selinux_status_deny_unknown - reference the SELinux kernel status without invocation of system calls
#include <selinux/avc.h> int selinux_status_open(int fallback); void selinux_status_close(void); int selinux_status_updated(void); int selinux_status_getenforce(void); int selinux_status_policyload(void); int selinux_status_deny_unknown(void);
Linux 2.6.37 or later provides a SELinux kernel status page; being mostly placed on /sys/fs/selinux/status entry. It enables userspace applications to mmap this page with read-only mode, then it informs some status without system call invocations. In some cases that a userspace application tries to apply heavy frequent access control; such as row-level security in databases, it will face unignorable cost to communicate with kernel space to check invalidation of userspace avc. These functions provides applications a way to know some kernel events without system-call invocation or worker thread for monitoring. selinux_status_open() tries to open(2) /sys/fs/selinux/status and mmap(2) it in read-only mode. The file-descriptor and pointer to the page shall be stored internally; Don't touch them directly. Set 1 on the fallback argument to handle a case of older kernels without kernel status page support. In this case, this function tries to open a netlink socket using avc_netlink_open(3) and overwrite corresponding callbacks (setenforce and policyload). Thus, we need to pay attention to the interaction with these interfaces, when fallback mode is enabled. selinux_status_close() unmap the kernel status page and close its file descriptor, or close the netlink socket if fallbacked. selinux_status_updated() processes status update events. There are two kinds of status updates. setenforce events will change the effective enforcing state used within the AVC, and policyload events will result in a cache flush. This function returns 0 if there have been no updates since the last call, 1 if there have been updates since the last call, or -1 on error. selinux_status_getenforce() returns 0 if SELinux is running in permissive mode, 1 if enforcing mode, or -1 on error. Same as security_getenforce(3) except with or without system call invocation. selinux_status_policyload() returns times of policy reloaded on the running system, or -1 on error. Note that it is not a reliable value on fallback-mode until it receive the first event message via netlink socket. Thus, don't use this value to know actual times of policy reloaded. selinux_status_deny_unknown() returns 0 if SELinux treats policy queries on undefined object classes or permissions as being allowed, 1 if such queries are denied, or -1 on error. Also note that these interfaces are not thread-safe, so you have to protect them from concurrent calls using exclusive locks when multiple threads are performing.
selinux_status_open() returns 0 or 1 on success. 1 means we are ready to use these interfaces, but netlink socket was opened as fallback instead of the kernel status page. On error, -1 shall be returned. Any other functions with a return value shall return its characteristic value as described above, or -1 on errors.
mmap(2), avc_netlink_open(3), security_getenforce(3), security_deny_unknown(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 2021-08-27. (At that time, the date of the most recent commit that was found in the repository was 2021-08-23.) 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 firstname.lastname@example.org email@example.com 22 January 2011 selinux_status_open(3)
Pages that refer to this page: avc_init(3), avc_open(3)