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[PATCH v3 1/3] elf: Allow dlopen of filter object to work [BZ #16272]
- From: David Kilroy <David dot Kilroy at arm dot com>
- To: "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Cc: nd <nd at arm dot com>
- Date: Tue, 3 Dec 2019 17:30:10 +0000
- Subject: [PATCH v3 1/3] elf: Allow dlopen of filter object to work [BZ #16272]
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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 relocatiion 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 filter objects are used, both as a normal link and when dlopen'd.
Tested by running the testsuite on x86_64.
---
elf/Makefile | 12 ++++++++++--
elf/dl-deps.c | 35 ++++++++++++++++++++++++++---------
elf/dl-open.c | 11 +++++++----
elf/tst-filterobj-dlopen.c | 39 +++++++++++++++++++++++++++++++++++++++
elf/tst-filterobj-flt.c | 24 ++++++++++++++++++++++++
elf/tst-filterobj-lib.c | 24 ++++++++++++++++++++++++
elf/tst-filterobj-lib.h | 18 ++++++++++++++++++
elf/tst-filterobj.c | 36 ++++++++++++++++++++++++++++++++++++
8 files changed, 184 insertions(+), 15 deletions(-)
create mode 100644 elf/tst-filterobj-dlopen.c
create mode 100644 elf/tst-filterobj-flt.c
create mode 100644 elf/tst-filterobj-lib.c
create mode 100644 elf/tst-filterobj-lib.h
create mode 100644 elf/tst-filterobj.c
diff --git a/elf/Makefile b/elf/Makefile
index 0debea7..69f11c7 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -199,7 +199,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
tst-debug1 tst-main1 tst-absolute-sym tst-absolute-zero tst-big-note \
tst-unwind-ctor tst-unwind-main tst-audit13 \
tst-sonamemove-link tst-sonamemove-dlopen tst-dlopen-tlsmodid \
- tst-dlopen-self tst-auditmany tst-initfinilazyfail tst-dlopenfail
+ tst-dlopen-self tst-auditmany tst-initfinilazyfail tst-dlopenfail \
+ tst-filterobj tst-filterobj-dlopen
# reldep9
tests-internal += loadtest unload unload2 circleload1 \
neededtest neededtest2 neededtest3 neededtest4 \
@@ -292,7 +293,8 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
tst-auditmanymod4 tst-auditmanymod5 tst-auditmanymod6 \
tst-auditmanymod7 tst-auditmanymod8 tst-auditmanymod9 \
tst-initlazyfailmod tst-finilazyfailmod \
- tst-dlopenfailmod1 tst-dlopenfaillinkmod tst-dlopenfailmod2
+ tst-dlopenfailmod1 tst-dlopenfaillinkmod tst-dlopenfailmod2 \
+ tst-filterobj-flt tst-filterobj-lib
# Most modules build with _ISOMAC defined, but those filtered out
# depend on internal headers.
modules-names-tests = $(filter-out ifuncmod% tst-libc_dlvsym-dso tst-tlsmod%,\
@@ -1627,3 +1629,9 @@ $(objpfx)tst-dlopenfailmod1.so: \
$(shared-thread-library) $(objpfx)tst-dlopenfaillinkmod.so
LDFLAGS-tst-dlopenfaillinkmod.so = -Wl,-soname,tst-dlopenfail-missingmod.so
$(objpfx)tst-dlopenfailmod2.so: $(shared-thread-library)
+
+LDFLAGS-tst-filterobj-flt.so = -Wl,--filter=$(objpfx)tst-filterobj-lib.so
+$(objpfx)tst-filterobj: $(objpfx)tst-filterobj-flt.so | $(objpfx)tst-filterobj-lib.so
+$(objpfx)tst-filterobj-dlopen: $(libdl) | $(objpfx)tst-filterobj-lib.so
+$(objpfx)tst-filterobj.out: $(objpfx)tst-filterobj-lib.so
+$(objpfx)tst-filterobj-dlopen.out: $(objpfx)tst-filterobj-lib.so
diff --git a/elf/dl-deps.c b/elf/dl-deps.c
index c29b988..bb85c83 100644
--- a/elf/dl-deps.c
+++ b/elf/dl-deps.c
@@ -550,13 +550,14 @@ 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 +582,32 @@ 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. First, find it in the search list. */
+ for (i = 0; i < nlist; ++i)
+ if (map->l_searchlist.r_list[i] == map)
+ break;
+ assert (i < nlist);
+ if (i > 0)
+ {
+ /* Copy the binary into position 0. */
+ memcpy (l_initfini, &map->l_searchlist.r_list[i],
+ sizeof (struct link_map *));
+ /* Copy the filtees. */
+ memcpy (&l_initfini[1], map->l_searchlist.r_list,
+ i * sizeof (struct link_map *));
+ /* Copy the remainder. */
+ memcpy (&l_initfini[i + 1], &map->l_searchlist.r_list[i + 1],
+ (nlist - i - 1) * sizeof (struct link_map *));
+ }
+ 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 df9f29a..9996fe9 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -637,22 +637,25 @@ 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-filterobj-dlopen.c b/elf/tst-filterobj-dlopen.c
new file mode 100644
index 0000000..81eed0f
--- /dev/null
+++ b/elf/tst-filterobj-dlopen.c
@@ -0,0 +1,39 @@
+/* Test for BZ16272, dlopen'ing a filter object.
+ Ensure that symbols from the filter object resolve to the filtee.
+
+ Copyright (C) 2019 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-flt.c b/elf/tst-filterobj-flt.c
new file mode 100644
index 0000000..b4e10b2
--- /dev/null
+++ b/elf/tst-filterobj-flt.c
@@ -0,0 +1,24 @@
+/* Copyright (C) 2019 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-lib.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-lib.c b/elf/tst-filterobj-lib.c
new file mode 100644
index 0000000..07e2348
--- /dev/null
+++ b/elf/tst-filterobj-lib.c
@@ -0,0 +1,24 @@
+/* Copyright (C) 2019 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-lib.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-lib.h b/elf/tst-filterobj-lib.h
new file mode 100644
index 0000000..bed9bf8
--- /dev/null
+++ b/elf/tst-filterobj-lib.h
@@ -0,0 +1,18 @@
+/* Copyright (C) 2019 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);
diff --git a/elf/tst-filterobj.c b/elf/tst-filterobj.c
new file mode 100644
index 0000000..d38eb9b
--- /dev/null
+++ b/elf/tst-filterobj.c
@@ -0,0 +1,36 @@
+/* Test that symbols from filter objects are resolved to the filtee.
+
+ Copyright (C) 2019 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-lib.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"
--
2.7.4