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.

1 files changed, 16 insertions, 2 deletions

diff --git a/elf/Makefile b/elf/Makefile
index 632a4d8b0f..dfd43fb39b 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -201,7 +201,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
 	 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-dlopenfail-2
+	 tst-dlopenfail-2 \
+	 tst-filterobj tst-filterobj-dlopen tst-auxobj tst-auxobj-dlopen
 #	 reldep9
 tests-internal += loadtest unload unload2 circleload1 \
 	 neededtest neededtest2 neededtest3 neededtest4 \
@@ -312,7 +313,8 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		tst-auditmanymod7 tst-auditmanymod8 tst-auditmanymod9 \
 		tst-initlazyfailmod tst-finilazyfailmod \
 		tst-dlopenfailmod1 tst-dlopenfaillinkmod tst-dlopenfailmod2 \
-		tst-dlopenfailmod3 tst-ldconfig-ld-mod
+		tst-dlopenfailmod3 tst-ldconfig-ld-mod \
+		tst-filterobj-flt tst-filterobj-aux tst-filterobj-filtee
 # 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%,\
@@ -1699,3 +1701,15 @@ LDFLAGS-tst-dlopen-nodelete-reloc-mod17.so = -Wl,--no-as-needed
 
 $(objpfx)tst-ldconfig-ld_so_conf-update.out: $(objpfx)tst-ldconfig-ld-mod.so
 $(objpfx)tst-ldconfig-ld_so_conf-update: $(libdl)
+
+LDFLAGS-tst-filterobj-flt.so = -Wl,--filter=$(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