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, 51 insertions, 0 deletions

diff --git a/elf/tst-nodelete.cc b/elf/tst-nodelete.cc
new file mode 100644
index 0000000000..176cb68836
--- /dev/null
+++ b/elf/tst-nodelete.cc
@@ -0,0 +1,51 @@
+#include "../dlfcn/dlfcn.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+static int
+do_test (void)
+{
+  int result = 0;
+
+  /* This is a test for correct handling of dlopen failures for library that
+     is loaded with RTLD_NODELETE flag.  The first dlopen should fail because
+     of undefined symbols in shared library.  The second dlopen then verifies
+     that library was properly unloaded.  */
+  if (dlopen ("tst-nodelete-rtldmod.so", RTLD_NOW | RTLD_NODELETE) != NULL
+      || dlopen ("tst-nodelete-rtldmod.so", RTLD_LAZY | RTLD_NOLOAD) != NULL)
+    {
+      printf ("RTLD_NODELETE test failed\n");
+      result = 1;
+    }
+
+  /* This is a test for correct handling of dlopen failures for library that
+     is linked with '-z nodelete' option and hence has DF_1_NODELETE flag.
+     The first dlopen should fail because of undefined symbols in shared
+     library.  The second dlopen then verifies that library was properly
+     unloaded.  */
+  if (dlopen ("tst-nodelete-zmod.so", RTLD_NOW) != NULL
+      || dlopen ("tst-nodelete-zmod.so", RTLD_LAZY | RTLD_NOLOAD) != NULL)
+    {
+      printf ("-z nodelete test failed\n");
+      result = 1;
+    }
+
+   /* This is a test for correct handling of dlopen failures for library
+     with unique symbols.  The first dlopen should fail because of undefined
+     symbols in shared library.  The second dlopen then verifies that library
+     was properly unloaded.  */
+  if (dlopen ("tst-nodelete-uniquemod.so", RTLD_NOW) != NULL
+      || dlopen ("tst-nodelete-uniquemod.so", RTLD_LAZY | RTLD_NOLOAD) != NULL)
+    {
+      printf ("Unique symbols test failed\n");
+      result = 1;
+    }
+
+  if (result == 0)
+    printf ("SUCCESS\n");
+
+  return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"