posix/mman: add mmap support for shm objects

Update #2859.

3 files changed, 66 insertions, 1 deletions

diff --git a/cpukit/posix/include/rtems/posix/mmanimpl.h b/cpukit/posix/include/rtems/posix/mmanimpl.h
index 9743685a57..bb33ac97ed 100644
--- a/cpukit/posix/include/rtems/posix/mmanimpl.h
+++ b/cpukit/posix/include/rtems/posix/mmanimpl.h
@@ -16,12 +16,15 @@
 #ifndef _RTEMS_POSIX_MMANIMPL_H
 #define _RTEMS_POSIX_MMANIMPL_H
 
-#include <rtems/chain.h>
+#include <rtems/libio_.h>
+#include <rtems/chain.h> /* FIXME: use score chains for proper layering? */
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+/* FIXME: add Doxygen */
+
 /**
  * Every mmap'ed region has a mapping.
  */
@@ -30,6 +33,8 @@ typedef struct mmap_mappings_s {
   void*            addr;  /**< The address of the mapped memory */
   size_t           len;   /**< The length of memory mapped */
   int              flags; /**< The mapping flags */
+  rtems_libio_t   *iop;   /**< The mapped object's file descriptor pointer */
+  bool             is_shared_shm; /**< True if MAP_SHARED of shared memory */
 } mmap_mapping;
 
 extern rtems_chain_control mmap_mappings;
diff --git a/cpukit/posix/include/rtems/posix/shm.h b/cpukit/posix/include/rtems/posix/shm.h
index dfdd58ed2a..9284b398cf 100644
--- a/cpukit/posix/include/rtems/posix/shm.h
+++ b/cpukit/posix/include/rtems/posix/shm.h
@@ -91,6 +91,16 @@ struct POSIX_Shm_Object_operations {
    * Returns the number of bytes read (copied) into @a buf.
    */
   int ( *object_read ) ( POSIX_Shm_Object *shm_obj, void *buf, size_t count );
+
+  /**
+   * @brief Maps a shared memory object.
+   *
+   * Establishes a memory mapping between the shared memory object and the
+   * caller.
+   *
+   * Returns the mapped address of the object.
+   */
+  void * ( *object_mmap ) ( POSIX_Shm_Object *shm_obj, size_t len, int prot, off_t off);
 };
 
 /**
@@ -144,6 +154,16 @@ extern int _POSIX_Shm_Object_read_from_workspace(
 );
 
 /**
+ * @brief object_mmap operation for shm objects stored in RTEMS Workspace.
+ */
+extern void * _POSIX_Shm_Object_mmap_from_workspace(
+  POSIX_Shm_Object *shm_obj,
+  size_t len,
+  int prot,
+  off_t off
+);
+
+/**
  * @brief object_create operation for shm objects stored in C program heap.
  */
 extern int _POSIX_Shm_Object_create_from_heap(
@@ -173,6 +193,16 @@ extern int _POSIX_Shm_Object_read_from_heap(
   size_t count
 );
 
+/**
+ * @brief object_mmap operation for shm objects stored in C program heap.
+ */
+extern void * _POSIX_Shm_Object_mmap_from_heap(
+  POSIX_Shm_Object *shm_obj,
+  size_t len,
+  int prot,
+  off_t off
+);
+
 /** @} */
 
 #ifdef __cplusplus
diff --git a/cpukit/posix/include/rtems/posix/shmimpl.h b/cpukit/posix/include/rtems/posix/shmimpl.h
index 6d81e5eb27..f16af8123d 100644
--- a/cpukit/posix/include/rtems/posix/shmimpl.h
+++ b/cpukit/posix/include/rtems/posix/shmimpl.h
@@ -96,6 +96,36 @@ static inline POSIX_Shm_Control* loc_to_shm(
   return (POSIX_Shm_Control*) loc->node_access;
 }
 
+static inline int POSIX_Shm_Attempt_delete(
+    POSIX_Shm_Control* shm
+)
+{
+  Objects_Control       *obj;
+  ISR_lock_Context       lock_ctx;
+  int err;
+
+  err = 0;
+
+  _Objects_Allocator_lock();
+  --shm->reference_count;
+  if ( shm->reference_count == 0 ) {
+    if ( (*shm->shm_object.ops->object_delete)( &shm->shm_object ) != 0 ) {
+      err = EIO;
+    }
+  }
+  /* check if the object has been unlinked yet. */
+  obj = _Objects_Get( shm->Object.id, &lock_ctx, &_POSIX_Shm_Information );
+  if ( obj == NULL ) {
+    /* if it was unlinked, then it can be freed. */
+    _POSIX_Shm_Free( shm );
+  } else {
+    /* it will be freed when it is unlinked. */
+    _ISR_lock_ISR_enable( &lock_ctx );
+  }
+  _Objects_Allocator_unlock();
+  return err;
+}
+
 /** @} */
 
 #ifdef __cplusplus