[RFC,v2,5/6] elf/dl-fini.c: Handle proxy link_map entries in the shutdown path

Message ID 20180606181934.2480-6-vivek@collabora.com
State New
Headers show
Series
  • Proof-of-Concept implementation of RTLD_SHARED for dlmopen
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Commit Message

Vivek Das Mohapatra June 6, 2018, 6:19 p.m.
When cleaning up before exit we should not call destructors or
otherwise free [most of] the contents of proxied link_map entries
since they share [most of] their contents with the LM_ID_BASE
objects to which they point.
---
 elf/dl-close.c | 43 ++++++++++++++++++++++++++-----------------
 elf/dl-fini.c  |  6 ++++--
 2 files changed, 30 insertions(+), 19 deletions(-)

Patch

diff --git a/elf/dl-close.c b/elf/dl-close.c
index ecd6729704..6c706a4ae8 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -267,8 +267,9 @@  _dl_close_worker (struct link_map *map, bool force)
 		  && (imap->l_flags_1 & DF_1_NODELETE) == 0);
 
 	  /* Call its termination function.  Do not do it for
-	     half-cooked objects.  */
-	  if (imap->l_init_called)
+	     half-cooked objects.
+             Proxies should never have this flag set, but we double check.  */
+	  if (imap->l_init_called && !imap->l_proxy)
 	    {
 	      /* When debugging print a message first.  */
 	      if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS,
@@ -353,7 +354,9 @@  _dl_close_worker (struct link_map *map, bool force)
 	     one for the terminating NULL pointer.  */
 	  size_t remain = (new_list != NULL) + 1;
 	  bool removed_any = false;
-	  for (size_t cnt = 0; imap->l_scope[cnt] != NULL; ++cnt)
+	  for (size_t cnt = 0;
+               imap->l_scope && imap->l_scope[cnt] != NULL;
+               ++cnt)
 	    /* This relies on l_scope[] entries being always set either
 	       to its own l_symbolic_searchlist address, or some map's
 	       l_searchlist address.  */
@@ -676,8 +679,10 @@  _dl_close_worker (struct link_map *map, bool force)
 
 	  /* We can unmap all the maps at once.  We determined the
 	     start address and length when we loaded the object and
-	     the `munmap' call does the rest.  */
-	  DL_UNMAP (imap);
+	     the `munmap' call does the rest. Proxies do not have
+             any segments of their own to unmap.  */
+          if (!imap->l_proxy)
+            DL_UNMAP (imap);
 
 	  /* Finally, unlink the data structure and free it.  */
 #if DL_NNS == 1
@@ -717,19 +722,23 @@  _dl_close_worker (struct link_map *map, bool force)
 	    _dl_debug_printf ("\nfile=%s [%lu];  destroying link map\n",
 			      imap->l_name, imap->l_ns);
 
-	  /* This name always is allocated.  */
-	  free (imap->l_name);
-	  /* Remove the list with all the names of the shared object.  */
+          /* Skip structures borrowed by proxies from the real map.  */
+          if (!imap->l_proxy)
+            {
+              /* This name always is allocated.  */
+              free (imap->l_name);
+              /* Remove the list with all the names of the shared object.  */
 
-	  struct libname_list *lnp = imap->l_libname;
-	  do
-	    {
-	      struct libname_list *this = lnp;
-	      lnp = lnp->next;
-	      if (!this->dont_free)
-		free (this);
-	    }
-	  while (lnp != NULL);
+              struct libname_list *lnp = imap->l_libname;
+              do
+                {
+                  struct libname_list *this = lnp;
+                  lnp = lnp->next;
+                  if (!this->dont_free)
+                    free (this);
+                }
+              while (lnp != NULL);
+            }
 
 	  /* Remove the searchlists.  */
 	  free (imap->l_initfini);
diff --git a/elf/dl-fini.c b/elf/dl-fini.c
index 3cfc262400..0403f6c4d8 100644
--- a/elf/dl-fini.c
+++ b/elf/dl-fini.c
@@ -72,7 +72,7 @@  _dl_fini (void)
 	  assert (nloaded != 0 || GL(dl_ns)[ns]._ns_loaded == NULL);
 	  for (l = GL(dl_ns)[ns]._ns_loaded, i = 0; l != NULL; l = l->l_next)
 	    /* Do not handle ld.so in secondary namespaces.  */
-	    if (l == l->l_real)
+	    if (l == l->l_real || l->l_proxy)
 	      {
 		assert (i < nloaded);
 
@@ -110,7 +110,9 @@  _dl_fini (void)
 	    {
 	      struct link_map *l = maps[i];
 
-	      if (l->l_init_called)
+              /* Do not call fini functions via proxies, or for
+                 objects which are not marked as initialised.  */
+	      if (l->l_init_called && !l->l_proxy)
 		{
 		  /* Make sure nothing happens if we are called twice.  */
 		  l->l_init_called = 0;