From: David Kilroy <David.Kilroy@arm.com>
Date: Wed, 12 Feb 2020 17:31:17 +0000 (-0300)
Subject: elf: avoid stack allocation in dl_open_worker
X-Git-Tag: glibc-2.32~673
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0a8ce6a0966283b17f373f430929bcadef1ae205;p=thirdparty%2Fglibc.git

elf: avoid stack allocation in dl_open_worker

As the sort was removed, there's no need to keep a separate map of
links. Instead, when relocating objects iterate over l_initfini
directly.

This allows us to remove the loop copying l_initfini elements into
map. We still need a loop to identify the first and last elements that
need relocation.

Tested by running the testsuite on x86_64.
---

diff --git a/elf/dl-open.c b/elf/dl-open.c
index 314adc2f7e5..7b3b177aa64 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -621,25 +621,18 @@ dl_open_worker (void *a)
      This allows IFUNC relocations to work and it also means copy
      relocation of dependencies are if necessary overwritten.
      __dl_map_object_deps has already sorted l_initfini for us.  */
-  unsigned int nmaps = 0;
+  unsigned int first = UINT_MAX;
+  unsigned int last = 0;
   unsigned int j = 0;
   struct link_map *l = new->l_initfini[0];
   do
     {
       if (! l->l_real->l_relocated)
-	++nmaps;
-      l = new->l_initfini[++j];
-    }
-  while (l != NULL);
-  /* Stack allocation is limited by the number of loaded objects.  */
-  struct link_map *maps[nmaps];
-  nmaps = 0;
-  j = 0;
-  l = new->l_initfini[0];
-  do
-    {
-      if (! l->l_real->l_relocated)
-	maps[nmaps++] = l;
+	{
+	  if (first == UINT_MAX)
+	    first = j;
+	  last = j + 1;
+	}
       l = new->l_initfini[++j];
     }
   while (l != NULL);
@@ -654,9 +647,12 @@ dl_open_worker (void *a)
      them.  However, such relocation dependencies in IFUNC resolvers
      are undefined anyway, so this is not a problem.  */
 
-  for (unsigned int i = nmaps; i-- > 0; )
+  for (unsigned int i = last; i-- > first; )
     {
-      l = maps[i];
+      l = new->l_initfini[i];
+
+      if (l->l_real->l_relocated)
+	continue;
 
       if (! relocation_in_progress)
 	{