source: rtems/cpukit/posix/src/munmap.c @ 87de70a2

/*
 * Copyright (c) 2012 Chris Johns (chrisj@rtems.org)
 * Copyright (c) 2017 Gedare Bloom (gedare@rtems.org)
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rtems.org/license/LICENSE.
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/mman.h>

#include <rtems/posix/mmanimpl.h> 
#include <rtems/posix/shmimpl.h>

static void shm_munmap( rtems_libio_t *iop )
{
  POSIX_Shm_Control *shm = iop_to_shm( iop );

  /* decrement mmap's shm reference_count and maybe delete the object */
  POSIX_Shm_Attempt_delete(shm);
}

int munmap(void *addr, size_t len)
{
  mmap_mapping      *mapping;
  rtems_chain_node  *node;
  uint32_t           refcnt;
  
  /*
   * Clear errno.
   */
  errno = 0;

  /*
   * Length cannot be 0.
   */
  if ( len == 0 ) {
    errno = EINVAL;
    return -1;
  }

  /*
   * Obtain the mmap lock. Sets errno on failure.
   */
  if ( !mmap_mappings_lock_obtain( ))
    return -1;

  node = rtems_chain_first (&mmap_mappings);
  while ( !rtems_chain_is_tail( &mmap_mappings, node )) {
    mapping = (mmap_mapping*) node;
    if ( ( addr >= mapping->addr ) &&
         ( addr < ( mapping->addr + mapping->len )) ) {
      rtems_chain_extract( node );
      /* FIXME: generally need a way to clean-up the backing object, but
       * currently it only matters for MAP_SHARED shm objects. */
      if ( mapping->is_shared_shm == true ) {
        shm_munmap(mapping->iop);
      }
      refcnt = rtems_libio_decrement_mapping_refcnt(mapping->iop);
      if ( refcnt == 0 ) {
        rtems_libio_check_deferred_free(mapping->iop);
      }
      /* only free the mapping address for non-fixed mapping */
      if (( mapping->flags & MAP_FIXED ) != MAP_FIXED ) {
        /* only free the mapping address for non-shared mapping, because we
         * re-use the mapping address across all of the shared mappings, and
         * it is memory managed independently... */
        if (( mapping->flags & MAP_SHARED ) != MAP_SHARED ) {
          free( mapping->addr );
        }
      }
      free( mapping );
      break;
    }
    node = rtems_chain_next( node );
  }

  mmap_mappings_lock_release( );
  return 0;
}