// SPDX-License-Identifier: GPL-2.0-only

  /*
   * mmap based event notifications for SELinux
   *
   * Author: KaiGai Kohei <kaigai@ak.jp.nec.com>
   *
   * Copyright (C) 2010 NEC corporation

   */
  #include <linux/kernel.h>
  #include <linux/gfp.h>
  #include <linux/mm.h>
  #include <linux/mutex.h>
  #include "avc.h"

  #include "security.h"

  
  /*
   * The selinux_status_page shall be exposed to userspace applications
   * using mmap interface on /selinux/status.
   * It enables to notify applications a few events that will cause reset
   * of userspace access vector without context switching.
   *
   * The selinux_kernel_status structure on the head of status page is
   * protected from concurrent accesses using seqlock logic, so userspace
   * application should reference the status page according to the seqlock
   * logic.
   *
   * Typically, application checks status->sequence at the head of access
   * control routine. If it is odd-number, kernel is updating the status,
   * so please wait for a moment. If it is changed from the last sequence
   * number, it means something happen, so application will reset userspace
   * avc, if needed.
   * In most cases, application shall confirm the kernel status is not
   * changed without any system call invocations.
   */

  
  /*
   * selinux_kernel_status_page
   *
   * It returns a reference to selinux_status_page. If the status page is
   * not allocated yet, it also tries to allocate it at the first time.
   */

  struct page *selinux_kernel_status_page(struct selinux_state *state)

  {
  	struct selinux_kernel_status   *status;
  	struct page		       *result = NULL;

  	mutex_lock(&state->status_lock);
  	if (!state->status_page) {
  		state->status_page = alloc_page(GFP_KERNEL|__GFP_ZERO);

  		if (state->status_page) {
  			status = page_address(state->status_page);

  
  			status->version = SELINUX_KERNEL_STATUS_VERSION;
  			status->sequence = 0;

  			status->enforcing = enforcing_enabled(state);

  			/*
  			 * NOTE: the next policyload event shall set
  			 * a positive value on the status->policyload,
  			 * although it may not be 1, but never zero.
  			 * So, application can know it was updated.
  			 */
  			status->policyload = 0;

  			status->deny_unknown =
  				!security_get_allow_unknown(state);

  		}
  	}

  	result = state->status_page;
  	mutex_unlock(&state->status_lock);

  
  	return result;
  }
  
  /*
   * selinux_status_update_setenforce
   *
   * It updates status of the current enforcing/permissive mode.
   */

  void selinux_status_update_setenforce(struct selinux_state *state,
  				      int enforcing)

  {
  	struct selinux_kernel_status   *status;

  	mutex_lock(&state->status_lock);
  	if (state->status_page) {
  		status = page_address(state->status_page);

  
  		status->sequence++;
  		smp_wmb();
  
  		status->enforcing = enforcing;
  
  		smp_wmb();
  		status->sequence++;
  	}

  	mutex_unlock(&state->status_lock);

  }
  
  /*
   * selinux_status_update_policyload
   *
   * It updates status of the times of policy reloaded, and current
   * setting of deny_unknown.
   */

  void selinux_status_update_policyload(struct selinux_state *state,
  				      int seqno)

  {
  	struct selinux_kernel_status   *status;

  	mutex_lock(&state->status_lock);
  	if (state->status_page) {
  		status = page_address(state->status_page);

  
  		status->sequence++;
  		smp_wmb();
  
  		status->policyload = seqno;

  		status->deny_unknown = !security_get_allow_unknown(state);

  
  		smp_wmb();
  		status->sequence++;
  	}

  	mutex_unlock(&state->status_lock);

  }