Add forced deletion support to _dl_close_worker

https://sourceware.org/bugzilla/show_bug.cgi?id=17833

I've a shared library that contains both undefined and unique symbols.
Then I try to call the following sequence of dlopen:

1. dlopen("./libfoo.so", RTLD_NOW)
2. dlopen("./libfoo.so", RTLD_LAZY | RTLD_GLOBAL)

First dlopen call terminates with error because of undefined symbols,
but STB_GNU_UNIQUE ones set DF_1_NODELETE flag and hence block library
in the memory.

The library goes into inconsistent state as several structures remain
uninitialized. For instance, relocations for GOT table were not performed.

By the time of second dlopen call this library looks like as it would be
fully initialized but this is not true: any call through incorrect GOT
table leads to segmentation fault.  On some systems this inconsistency
triggers assertions in the dynamic linker.

This patch adds a parameter to _dl_close_worker to implement forced object
deletion in case of dlopen() failure:

1. Clears DF_1_NODELETE bit if forced, to allow library to be removed from
memory.
2. For each unique symbol that is defined in this object clears
appropriate entry in _ns_unique_sym_table.

	[BZ #17833]
	* elf/Makefile (tests): Add tst-nodelete.
	(modules-names): Add tst-nodelete-uniquemod.
	(tst-nodelete-uniquemod.so-no-z-defs): New.
	(tst-nodelete-rtldmod.so-no-z-defs): Likewise.
	(tst-nodelete-zmod.so-no-z-defs): Likewise.
	($(objpfx)tst-nodelete): Likewise.
	($(objpfx)tst-nodelete.out): Likewise.
	(LDFLAGS-tst-nodelete): Likewise.
	(LDFLAGS-tst-nodelete-zmod.so): Likewise.
	* elf/dl-close.c (_dl_close_worker): Add a parameter to
	implement forced object deletion.
	(_dl_close): Pass false to _dl_close_worker.
	* elf/dl-open.c (_dl_open): Pass true to _dl_close_worker.
	* elf/tst-nodelete.cc: New file.
	* elf/tst-nodeletelib.cc: Likewise.
	* elf/tst-znodeletelib.cc: Likewise.
	* include/dlfcn.h (_dl_close_worker): Add a new parameter.

1 files changed, 2 insertions, 1 deletions

diff --git a/include/dlfcn.h b/include/dlfcn.h
index a67b2e3251..0ce0af5276 100644
--- a/include/dlfcn.h
+++ b/include/dlfcn.h
@@ -54,7 +54,8 @@ struct link_map;
 extern void _dl_close (void *map) attribute_hidden;
 /* Same as above, but without locking and safety checks for user
    provided map arguments.  */
-extern void _dl_close_worker (struct link_map *map) attribute_hidden;
+extern void _dl_close_worker (struct link_map *map, bool force)
+    attribute_hidden;
 
 /* Look up NAME in shared object HANDLE (which may be RTLD_DEFAULT or
    RTLD_NEXT).  WHO is the calling function, for RTLD_NEXT.  Returns