commit eb447b7b4bd6177f876ba9420ad9e048c27bae91

Author: David Kilroy <David.Kilroy@arm.com>

Date:   Wed Feb 12 14:28:15 2020 -0300

    elf: Allow dlopen of filter object to work [BZ #16272]

    There are two fixes that are needed to be able to dlopen filter

    objects. First _dl_map_object_deps cannot assume that map will be at

    the beginning of l_searchlist.r_list[], as filtees are inserted before

    map. Secondly dl_open_worker needs to ensure that filtees get

    relocated.

    In _dl_map_object_deps:

    * avoiding removing relocation dependencies of map by setting

      l_reserved to 0 and otherwise processing the rest of the search

      list.

    * ensure that map remains at the beginning of l_initfini - the list

      of things that need initialisation (and destruction). Do this by

      splitting the copy up. This may not be required, but matches the

      initialization order without dlopen.

    Modify dl_open_worker to relocate the objects in new->l_inifini.

    new->l_initfini is constructed in _dl_map_object_deps, and lists the

    objects that need initialization and destruction. Originally the list

    of objects in new->l_next are relocated. All of these objects should

    also be included in new->l_initfini (both lists are populated with

    dependencies in _dl_map_object_deps). We can't use new->l_prev to pick

    up filtees, as during a recursive dlopen from an interposed malloc

    call, l->prev can contain objects that are not ready for relocation.

    Add tests to verify that symbols resolve to the filtee implementation

    when auxiliary and filter objects are used, both as a normal link and

    when dlopen'd.

    Tested by running the testsuite on x86_64.

# Conflicts:

#	elf/Makefile

diff --git a/elf/Makefile b/elf/Makefile

index a52d9b1f6a4364a7..b4b618ce62a9e6df 100644

--- a/elf/Makefile

+++ b/elf/Makefile

@@ -192,7 +192,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \

 	 tst-latepthread tst-tls-manydynamic tst-nodelete-dlclose \

 	 tst-debug1 tst-main1 tst-absolute-sym tst-absolute-zero tst-big-note \

 	 tst-sonamemove-link tst-sonamemove-dlopen tst-initfinilazyfail \

-	 tst-dlopenfail tst-dlopenfail-2

+	 tst-dlopenfail tst-dlopenfail-2 \

+	 tst-filterobj tst-filterobj-dlopen tst-auxobj tst-auxobj-dlopen

 #	 reldep9

 tests-internal += loadtest unload unload2 circleload1 \

 	 neededtest neededtest2 neededtest3 neededtest4 \

@@ -302,7 +303,8 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \

 		tst-sonamemove-runmod1 tst-sonamemove-runmod2 \

 		tst-initlazyfailmod tst-finilazyfailmod \

 		tst-dlopenfailmod1 tst-dlopenfaillinkmod tst-dlopenfailmod2 \

-		tst-dlopenfailmod3

+		tst-dlopenfailmod3 \

+		tst-filterobj-flt tst-filterobj-aux tst-filterobj-filtee

 ifeq (yes,$(have-mtls-dialect-gnu2))

 tests += tst-gnu2-tls1

@@ -1626,3 +1628,15 @@ $(objpfx)tst-dlopen-nodelete-reloc-mod17.so: \

   $(objpfx)tst-dlopen-nodelete-reloc-mod15.so \

   $(objpfx)tst-dlopen-nodelete-reloc-mod16.so

 LDFLAGS-tst-dlopen-nodelete-reloc-mod17.so = -Wl,--no-as-needed

+

+LDFLAGS-tst-filterobj-flt.so = -Wl,--filter=$(objpfx)tst-filterobj-filtee.so

+$(objpfx)tst-filterobj: $(objpfx)tst-filterobj-flt.so

+$(objpfx)tst-filterobj-dlopen: $(libdl)

+$(objpfx)tst-filterobj.out: $(objpfx)tst-filterobj-filtee.so

+$(objpfx)tst-filterobj-dlopen.out: $(objpfx)tst-filterobj-filtee.so

+

+LDFLAGS-tst-filterobj-aux.so = -Wl,--auxiliary=$(objpfx)tst-filterobj-filtee.so

+$(objpfx)tst-auxobj: $(objpfx)tst-filterobj-aux.so

+$(objpfx)tst-auxobj-dlopen: $(libdl)

+$(objpfx)tst-auxobj.out: $(objpfx)tst-filterobj-filtee.so

+$(objpfx)tst-auxobj-dlopen.out: $(objpfx)tst-filterobj-filtee.so

diff --git a/elf/dl-deps.c b/elf/dl-deps.c

index 9d9b1ba7f244348a..50f053a1586efdc3 100644

--- a/elf/dl-deps.c

+++ b/elf/dl-deps.c

@@ -485,14 +485,18 @@ _dl_map_object_deps (struct link_map *map,

   map->l_searchlist.r_list = &l_initfini[nlist + 1];

   map->l_searchlist.r_nlist = nlist;

+  unsigned int map_index = UINT_MAX;

   for (nlist = 0, runp = known; runp; runp = runp->next)

     {

       if (__builtin_expect (trace_mode, 0) && runp->map->l_faked)

 	/* This can happen when we trace the loading.  */

 	--map->l_searchlist.r_nlist;

-      else

+      else {

+	if (runp->map == map)

+	  map_index = nlist;

 	map->l_searchlist.r_list[nlist++] = runp->map;

+      }

       /* Now clear all the mark bits we set in the objects on the search list

 	 to avoid duplicates, so the next call starts fresh.  */

@@ -550,13 +554,14 @@ Filters not supported with LD_TRACE_PRELINKING"));

     }

   /* Maybe we can remove some relocation dependencies now.  */

-  assert (map->l_searchlist.r_list[0] == map);

   struct link_map_reldeps *l_reldeps = NULL;

   if (map->l_reldeps != NULL)

     {

-      for (i = 1; i < nlist; ++i)

+      for (i = 0; i < nlist; ++i)

 	map->l_searchlist.r_list[i]->l_reserved = 1;

+      /* Avoid removing relocation dependencies of the main binary.  */

+      map->l_reserved = 0;

       struct link_map **list = &map->l_reldeps->list[0];

       for (i = 0; i < map->l_reldeps->act; ++i)

 	if (list[i]->l_reserved)

@@ -581,16 +586,30 @@ Filters not supported with LD_TRACE_PRELINKING"));

 	      }

 	  }

-      for (i = 1; i < nlist; ++i)

+      for (i = 0; i < nlist; ++i)

 	map->l_searchlist.r_list[i]->l_reserved = 0;

     }

-  /* Sort the initializer list to take dependencies into account.  The binary

-     itself will always be initialize last.  */

-  memcpy (l_initfini, map->l_searchlist.r_list,

-	  nlist * sizeof (struct link_map *));

-  /* We can skip looking for the binary itself which is at the front of

-     the search list.  */

+  /* Sort the initializer list to take dependencies into account.  Always

+     initialize the binary itself last.  */

+  assert (map_index < nlist);

+  if (map_index > 0)

+    {

+      /* Copy the binary into position 0.  */

+      l_initfini[0] = map->l_searchlist.r_list[map_index];

+

+      /* Copy the filtees.  */

+      for (i = 0; i < map_index; ++i)

+	l_initfini[i+1] = map->l_searchlist.r_list[i];

+

+      /* Copy the remainder.  */

+      for (i = map_index + 1; i < nlist; ++i)

+	l_initfini[i] = map->l_searchlist.r_list[i];

+    }

+  else

+    memcpy (l_initfini, map->l_searchlist.r_list,

+	    nlist * sizeof (struct link_map *));

+

   _dl_sort_maps (&l_initfini[1], nlist - 1, NULL, false);

   /* Terminate the list of dependencies.  */

diff --git a/elf/dl-open.c b/elf/dl-open.c

index d834b89754d2b073..d31356f7e17dfb14 100644

--- a/elf/dl-open.c

+++ b/elf/dl-open.c

@@ -618,22 +618,25 @@ dl_open_worker (void *a)

      allows IFUNC relocations to work and it also means copy

      relocation of dependencies are if necessary overwritten.  */

   unsigned int nmaps = 0;

-  struct link_map *l = new;

+  unsigned int j = 0;

+  struct link_map *l = new->l_initfini[0];

   do

     {

       if (! l->l_real->l_relocated)

 	++nmaps;

-      l = l->l_next;

+      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;

-  l = new;

+  j = 0;

+  l = new->l_initfini[0];

   do

     {

       if (! l->l_real->l_relocated)

 	maps[nmaps++] = l;

-      l = l->l_next;

+      l = new->l_initfini[++j];

     }

   while (l != NULL);

   _dl_sort_maps (maps, nmaps, NULL, false);

diff --git a/elf/tst-auxobj-dlopen.c b/elf/tst-auxobj-dlopen.c

new file mode 100644

index 0000000000000000..cb54aba19470a1fe

--- /dev/null

+++ b/elf/tst-auxobj-dlopen.c

@@ -0,0 +1,47 @@

+/* Test for BZ#16272, dlopen'ing an auxiliary filter object.

+   Ensure that symbols from the resolve correctly.

+

+   Copyright (C) 2020 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <https://www.gnu.org/licenses/>.  */

+

+#include <stdio.h>

+#include <support/check.h>

+#include <support/xdlfcn.h>

+

+static int do_test (void)

+{

+  void *lib = xdlopen ("tst-filterobj-aux.so", RTLD_LAZY);

+  char *(*fn)(void) = xdlsym (lib, "get_text");

+  const char* text = fn ();

+

+  printf ("%s\n", text);

+

+  /* Verify the text matches what we expect from the filtee */

+  TEST_COMPARE_STRING (text, "Hello from filtee (PASS)");

+

+  fn = xdlsym (lib, "get_text2");

+  text = fn ();

+

+  printf ("%s\n", text);

+

+  /* Verify the text matches what we expect from the auxiliary object */

+  TEST_COMPARE_STRING (text, "Hello from auxiliary filter object (PASS)");

+

+  return 0;

+}

+

+#include <support/test-driver.c>

diff --git a/elf/tst-auxobj.c b/elf/tst-auxobj.c

new file mode 100644

index 0000000000000000..bdc7713b04b4a79b

--- /dev/null

+++ b/elf/tst-auxobj.c

@@ -0,0 +1,42 @@

+/* Test that symbols from auxiliary filter objects are resolved to the

+   filtee.

+

+   Copyright (C) 2020 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <https://www.gnu.org/licenses/>.  */

+

+#include <stdio.h>

+#include <support/check.h>

+#include "tst-filterobj-filtee.h"

+

+static int do_test (void)

+{

+  const char* text = get_text ();

+  printf ("%s\n", text);

+

+  /* Verify the text matches what we expect from the filtee */

+  TEST_COMPARE_STRING (text, "Hello from filtee (PASS)");

+

+  text = get_text2 ();

+  printf ("%s\n", text);

+

+  /* Verify the text matches what we expect from the auxiliary object */

+  TEST_COMPARE_STRING (text, "Hello from auxiliary filter object (PASS)");

+

+  return 0;

+}

+

+#include <support/test-driver.c>

diff --git a/elf/tst-filterobj-aux.c b/elf/tst-filterobj-aux.c

new file mode 100644

index 0000000000000000..0b732f2fb3a69a7f

--- /dev/null

+++ b/elf/tst-filterobj-aux.c

@@ -0,0 +1,33 @@

+/* Auxiliary filter object.

+   Contains symbols to be resolved in filtee, and one which doesn't.

+

+   Copyright (C) 2020 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <https://www.gnu.org/licenses/>.  */

+

+#include "tst-filterobj-filtee.h"

+

+/* We never want to see the output of the auxiliary object.  */

+const char *get_text (void)

+{

+  return "Hello from auxiliary filter object (FAIL)";

+}

+

+/* The filtee doesn't implement this symbol, so this should resolve.  */

+const char *get_text2 (void)

+{

+  return "Hello from auxiliary filter object (PASS)";

+}

diff --git a/elf/tst-filterobj-dlopen.c b/elf/tst-filterobj-dlopen.c

new file mode 100644

index 0000000000000000..c5b5072979802b98

--- /dev/null

+++ b/elf/tst-filterobj-dlopen.c

@@ -0,0 +1,39 @@

+/* Test for BZ#16272, dlopen'ing a filter object.

+   Ensure that symbols from the filter object resolve to the filtee.

+

+   Copyright (C) 2020 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <https://www.gnu.org/licenses/>.  */

+

+#include <stdio.h>

+#include <support/check.h>

+#include <support/xdlfcn.h>

+

+static int do_test (void)

+{

+  void *lib = xdlopen ("tst-filterobj-flt.so", RTLD_LAZY);

+  char *(*fn)(void) = xdlsym (lib, "get_text");

+  const char* text = fn ();

+

+  printf ("%s\n", text);

+

+  /* Verify the text matches what we expect from the filtee */

+  TEST_COMPARE_STRING (text, "Hello from filtee (PASS)");

+

+  return 0;

+}

+

+#include <support/test-driver.c>

diff --git a/elf/tst-filterobj-filtee.c b/elf/tst-filterobj-filtee.c

new file mode 100644

index 0000000000000000..8fa557cbd251f53c

--- /dev/null

+++ b/elf/tst-filterobj-filtee.c

@@ -0,0 +1,27 @@

+/* Filtee for BZ#16272 test.

+   Contains desired symbol implementations.

+

+   Copyright (C) 2020 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <https://www.gnu.org/licenses/>.  */

+

+#include "tst-filterobj-filtee.h"

+

+/* This is the real implementation that wants to be called */

+const char *get_text (void)

+{

+  return "Hello from filtee (PASS)";

+}

diff --git a/elf/tst-filterobj-filtee.h b/elf/tst-filterobj-filtee.h

new file mode 100644

index 0000000000000000..46aee28178b88a77

--- /dev/null

+++ b/elf/tst-filterobj-filtee.h

@@ -0,0 +1,24 @@

+/* Filtee header for BZ#16272 test.

+   Contains prototypes for symbols implemented in the filtee.

+

+   Copyright (C) 2020 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <https://www.gnu.org/licenses/>.  */

+

+const char *get_text (void);

+

+/* For testing auxiliary filter object.  */

+const char *get_text2 (void);

diff --git a/elf/tst-filterobj-flt.c b/elf/tst-filterobj-flt.c

new file mode 100644

index 0000000000000000..5062654be6f14a80

--- /dev/null

+++ b/elf/tst-filterobj-flt.c

@@ -0,0 +1,27 @@

+/* Filter object for BZ#16272 test.

+   Contains symbols to be resolved in filtee.

+

+   Copyright (C) 2020 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <https://www.gnu.org/licenses/>.  */

+

+#include "tst-filterobj-filtee.h"

+

+/* We never want to see the output of the filter object */

+const char *get_text (void)

+{

+  return "Hello from filter object (FAIL)";

+}

diff --git a/elf/tst-filterobj.c b/elf/tst-filterobj.c

new file mode 100644

index 0000000000000000..96bfae019ea670bc

--- /dev/null

+++ b/elf/tst-filterobj.c

@@ -0,0 +1,36 @@

+/* Test that symbols from filter objects are resolved to the filtee.

+

+   Copyright (C) 2020 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <https://www.gnu.org/licenses/>.  */

+

+#include <stdio.h>

+#include <support/check.h>

+#include "tst-filterobj-filtee.h"

+

+static int do_test (void)

+{

+  const char* text = get_text ();

+

+  printf ("%s\n", text);

+

+  /* Verify the text matches what we expect from the filtee */

+  TEST_COMPARE_STRING (text, "Hello from filtee (PASS)");

+

+  return 0;

+}

+

+#include <support/test-driver.c>