diff --git a/libgcc/Makefile.in b/libgcc/Makefile.in
index 6c4dc79ab715..5ef94380ec02 100644
--- a/libgcc/Makefile.in
+++ b/libgcc/Makefile.in
@@ -1048,8 +1048,9 @@ crtbeginT$(objext): $(srcdir)/crtstuff.c
 crtoffloadbegin$(objext): $(srcdir)/offloadstuff.c
 	$(crt_compile) $(CRTSTUFF_T_CFLAGS) -c $< -DCRT_BEGIN
 
+# crtoffloadend contains a constructor with calls to libgomp, so build as PIC.
 crtoffloadend$(objext): $(srcdir)/offloadstuff.c
-	$(crt_compile) $(CRTSTUFF_T_CFLAGS) -c $< -DCRT_END
+	$(crt_compile) $(CRTSTUFF_T_CFLAGS) $(PICFLAG) -c $< -DCRT_END
 
 crtoffloadtable$(objext): $(srcdir)/offloadstuff.c
 	$(crt_compile) $(CRTSTUFF_T_CFLAGS) -c $< -DCRT_TABLE
diff --git a/libgcc/offloadstuff.c b/libgcc/offloadstuff.c
index 4e1c4d41dd57..6796aa2a83c1 100644
--- a/libgcc/offloadstuff.c
+++ b/libgcc/offloadstuff.c
@@ -63,6 +63,19 @@ const void *const __offload_vars_end[0]
   __attribute__ ((__used__, visibility ("hidden"),
 		  section (OFFLOAD_VAR_TABLE_SECTION_NAME))) = { };
 
+extern void GOMP_offload_register_ver (unsigned, const void *, int,
+				       const void *);
+extern const void *const __OFFLOAD_TABLE__[0] __attribute__ ((weak));
+static void __attribute__((constructor))
+init_non_offload (void)
+{
+  /* If an OpenMP program has no offloading, post-offload_register callbacks
+     that need to run will require a call to GOMP_offload_register_ver, in
+     order to properly trigger those callbacks during init.  */
+  if (__OFFLOAD_TABLE__ == NULL)
+    GOMP_offload_register_ver (0, NULL, 0, NULL);
+}
+
 #elif defined CRT_TABLE
 
 extern const void *const __offload_func_table[];
diff --git a/libgfortran/gfortran.map b/libgfortran/gfortran.map
index db9b86cb183f..abb4def5b808 100644
--- a/libgfortran/gfortran.map
+++ b/libgfortran/gfortran.map
@@ -1765,3 +1765,8 @@ GFORTRAN_13 {
     __ieee_exceptions_MOD_ieee_get_modes;
     __ieee_exceptions_MOD_ieee_set_modes;
 } GFORTRAN_12;
+
+GFORTRAN_14 {
+  global:
+  _gfortran_mem_allocators_init;
+} GFORTRAN_13;
diff --git a/libgfortran/libgfortran.h b/libgfortran/libgfortran.h
index b972b0aa0cd5..535a3d67b25f 100644
--- a/libgfortran/libgfortran.h
+++ b/libgfortran/libgfortran.h
@@ -878,6 +878,11 @@ internal_proto(xrealloc);
 extern void xfree (void *);
 internal_proto(xfree);
 
+#if !defined(LIBGFOR_MINIMAL) && defined(__linux__)
+extern void mem_allocators_init (void *, void *, void *, void *);
+export_proto(mem_allocators_init);
+#endif
+
 /* environ.c */
 
 extern void init_variables (void);
diff --git a/libgfortran/runtime/main.c b/libgfortran/runtime/main.c
index bcdcb20a1236..b676ccc1df9e 100644
--- a/libgfortran/runtime/main.c
+++ b/libgfortran/runtime/main.c
@@ -61,9 +61,16 @@ get_args (int *argc, char ***argv)
 
 /* Initialize the runtime library.  */
 
-static void __attribute__((constructor))
-init (void)
+static void
+do_init (void)
 {
+#if !defined(LIBGFOR_MINIMAL) && defined(__linux__)
+  static bool do_init_ran = false;
+  if (do_init_ran)
+    return;
+  do_init_ran = true;
+#endif
+
   /* Must be first */
   init_variables ();
 
@@ -82,5 +89,37 @@ init (void)
 static void __attribute__((destructor))
 cleanup (void)
 {
+#if !defined(LIBGFOR_MINIMAL) && defined(__linux__)
+  static bool cleanup_ran = false;
+  if (cleanup_ran)
+    return;
+  cleanup_ran = true;
+#endif
+
   close_units ();
 }
+
+#if !defined(LIBGFOR_MINIMAL) && defined(__linux__)
+extern void __attribute__((weak))
+GOMP_post_offload_register_callback (void (*func)(void));
+
+extern void __attribute__((weak))
+GOMP_pre_gomp_target_fini_callback (void (*func)(void));
+#endif
+
+static void __attribute__((constructor))
+init (void)
+{
+#if !defined(LIBGFOR_MINIMAL) && defined(__linux__)
+  if (GOMP_post_offload_register_callback)
+    {
+      GOMP_post_offload_register_callback (do_init);
+      GOMP_pre_gomp_target_fini_callback (cleanup);
+      return;
+    }
+#endif
+
+  /* If libgomp is not present, then we can go ahead and call do_init
+     directly.  */
+  do_init ();
+}
diff --git a/libgfortran/runtime/memory.c b/libgfortran/runtime/memory.c
index a1539836c9c2..59b53843ffd8 100644
--- a/libgfortran/runtime/memory.c
+++ b/libgfortran/runtime/memory.c
@@ -26,6 +26,28 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #include "libgfortran.h"
 #include <errno.h>
 
+#if !defined(LIBGFOR_MINIMAL) && defined(__linux__)
+static void * (*gfortran_malloc)(size_t) = malloc;
+static void * (*gfortran_calloc)(size_t, size_t) = calloc;
+static void * (*gfortran_realloc)(void *, size_t) = realloc;
+static void (*gfortran_free)(void *) = free;
+
+void
+mem_allocators_init (void *malloc_ptr, void *calloc_ptr,
+		     void *realloc_ptr, void *free_ptr)
+{
+  gfortran_malloc = malloc_ptr;
+  gfortran_calloc = calloc_ptr;
+  gfortran_realloc = realloc_ptr;
+  gfortran_free = free_ptr;
+}
+
+#else
+#define gfortran_malloc malloc
+#define gfortran_calloc calloc
+#define gfortran_realloc realloc
+#define gfortran_free free
+#endif
 
 void *
 xmalloc (size_t n)
@@ -35,7 +57,7 @@ xmalloc (size_t n)
   if (n == 0)
     n = 1;
 
-  p = malloc (n);
+  p = gfortran_malloc (n);
 
   if (p == NULL)
     os_error ("Memory allocation failed");
@@ -57,7 +79,7 @@ xmallocarray (size_t nmemb, size_t size)
       os_error ("Integer overflow in xmallocarray");
     }
 
-  p = malloc (prod);
+  p = gfortran_malloc (prod);
 
   if (!p)
     os_error ("Memory allocation failed in xmallocarray");
@@ -73,7 +95,7 @@ xcalloc (size_t nmemb, size_t size)
   if (!nmemb || !size)
     nmemb = size = 1;
 
-  void *p = calloc (nmemb, size);
+  void *p = gfortran_calloc (nmemb, size);
   if (!p)
     os_error ("Allocating cleared memory failed");
 
@@ -86,7 +108,7 @@ xrealloc (void *ptr, size_t size)
   if (size == 0)
     size = 1;
 
-  void *newp = realloc (ptr, size);
+  void *newp = gfortran_realloc (ptr, size);
   if (!newp)
     os_error ("Memory allocation failure in xrealloc");
 
@@ -96,5 +118,5 @@ xrealloc (void *ptr, size_t size)
 void
 xfree (void *ptr)
 {
-  free (ptr);
+  gfortran_free (ptr);
 }
diff --git a/libgomp/libgomp.map b/libgomp/libgomp.map
index a9621c0a68c4..694a8f1a3598 100644
--- a/libgomp/libgomp.map
+++ b/libgomp/libgomp.map
@@ -423,6 +423,12 @@ GOMP_5.1.1 {
 	GOMP_taskwait_depend_nowait;
 } GOMP_5.1;
 
+GOMP_5.1.2 {
+  global:
+	GOMP_post_offload_register_callback;
+	GOMP_pre_gomp_target_fini_callback;
+} GOMP_5.1.1;
+
 OACC_2.0 {
   global:
 	acc_get_num_devices;
diff --git a/libgomp/target.c b/libgomp/target.c
index 6dd78e1e63dd..20a7f3776c2d 100644
--- a/libgomp/target.c
+++ b/libgomp/target.c
@@ -3153,6 +3153,70 @@ gomp_requires_to_name (char *buf, size_t size, int requires_mask)
 		   (p == buf ? "" : ", "));
 }
 
+/* Macro to define a callback set with a name, and routine to register
+   a callback function into set.  */
+#define GOMP_DEFINE_CALLBACK_SET(name)				\
+  static unsigned int num_ ## name ## _callbacks = 0;		\
+  static void (*name ## _callbacks[4])(void);			\
+  void GOMP_ ## name ## _callback (void (*fn)(void))		\
+  {								\
+    if (num_ ## name ## _callbacks				\
+	< (sizeof (name ## _callbacks)				\
+	   / sizeof (name ## _callbacks[0])))			\
+      {								\
+	name ## _callbacks[num_ ## name ## _callbacks] = fn;	\
+	num_ ## name ## _callbacks += 1;			\
+      }								\
+  }
+GOMP_DEFINE_CALLBACK_SET(post_offload_register)
+GOMP_DEFINE_CALLBACK_SET(pre_gomp_target_fini)
+#undef GOMP_DEFINE_CALLBACK_SET
+
+/* Routines to insert into libgfortran, under unified_shared_memory.  */
+static void *
+libgfortran_malloc_usm (size_t size)
+{
+  return omp_alloc (size, ompx_unified_shared_mem_alloc);
+}
+
+static void *
+libgfortran_calloc_usm (size_t n, size_t size)
+{
+  return omp_calloc (n, size, ompx_unified_shared_mem_alloc);
+}
+
+static void *
+libgfortran_realloc_usm (void *ptr, size_t size)
+{
+  return omp_realloc (ptr, size, ompx_unified_shared_mem_alloc,
+		      ompx_unified_shared_mem_alloc);
+}
+
+static void
+libgfortran_free_usm (void *ptr)
+{
+  omp_free (ptr, ompx_unified_shared_mem_alloc);
+}
+
+extern void __attribute__((weak))
+_gfortran_mem_allocators_init (void *, void *, void *, void *);
+
+static void
+gomp_libgfortran_omp_allocators_init (int omp_requires_mask)
+{
+  static bool init = false;
+  if (init)
+    return;
+  init = true;
+
+  if ((omp_requires_mask & GOMP_REQUIRES_UNIFIED_SHARED_MEMORY)
+      && _gfortran_mem_allocators_init != NULL)
+    _gfortran_mem_allocators_init (libgfortran_malloc_usm,
+				   libgfortran_calloc_usm,
+				   libgfortran_realloc_usm,
+				   libgfortran_free_usm);
+}
+
 /* This function should be called from every offload image while loading.
    It gets the descriptor of the host func and var tables HOST_TABLE, TYPE of
    the target, and DATA.  */
@@ -3163,6 +3227,9 @@ GOMP_offload_register_ver (unsigned version, const void *host_table,
 {
   int i;
 
+  if (host_table == NULL)
+    goto end;
+
   if (GOMP_VERSION_LIB (version) > GOMP_VERSION)
     gomp_fatal ("Library too old for offload (version %u < %u)",
 		GOMP_VERSION, GOMP_VERSION_LIB (version));
@@ -3229,6 +3296,14 @@ GOMP_offload_register_ver (unsigned version, const void *host_table,
 
   num_offload_images++;
   gomp_mutex_unlock (&register_lock);
+
+  /* Call into libgfortran to initialize OpenMP memory allocators.  */
+  gomp_libgfortran_omp_allocators_init (omp_requires_mask);
+
+ end:
+  for (int i = 0; i < num_post_offload_register_callbacks; i++)
+    post_offload_register_callbacks[i] ();
+  num_post_offload_register_callbacks = 0;
 }
 
 /* Legacy entry point.  */
@@ -3341,7 +3416,7 @@ gomp_unload_device (struct gomp_device_descr *devicep)
   if (devicep->state == GOMP_DEVICE_INITIALIZED)
     {
       unsigned i;
-      
+
       /* Unload from device all images registered at the moment.  */
       for (i = 0; i < num_offload_images; i++)
 	{
@@ -6507,6 +6582,13 @@ gomp_target_init (void)
   devices = devs;
   if (atexit (gomp_target_fini) != 0)
     gomp_fatal ("atexit failed");
+
+  /* Register 'pre_gomp_target_fini' callbacks to run before gomp_target_fini
+     during finalization.  */
+  for (int i = 0; i < num_pre_gomp_target_fini_callbacks; i++)
+    if (atexit (pre_gomp_target_fini_callbacks[i]) != 0)
+      gomp_fatal ("atexit failed");
+  num_pre_gomp_target_fini_callbacks = 0;
 }
 
 #else /* PLUGIN_SUPPORT */
diff --git a/libgomp/testsuite/libgomp.fortran/target-unified_shared_memory-1.f90 b/libgomp/testsuite/libgomp.fortran/target-unified_shared_memory-1.f90
new file mode 100644
index 000000000000..f82b1c7527cd
--- /dev/null
+++ b/libgomp/testsuite/libgomp.fortran/target-unified_shared_memory-1.f90
@@ -0,0 +1,13 @@
+! { dg-do run }
+
+program requires_unified_shared_memory
+  character(32) :: str
+  !$omp requires unified_shared_memory
+
+  str = trim (str)
+
+  !$omp target
+  block
+  end block
+
+end program requires_unified_shared_memory