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authorCarlos O'Donell <carlos@systemhalted.org>2015-01-21 01:51:10 -0500
committerCarlos O'Donell <carlos@systemhalted.org>2015-01-21 01:51:10 -0500
commitccdb048df457d581f6ac7ede8b0c7a593a891dfa (patch)
tree9f87447c45093fb2ded95c982e68c9e6e886129c /dlfcn/tst-rec-dlopen.c
parent042e1521c794a945edc43b5bfa7e69ad70420524 (diff)
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Fix recursive dlopen.
The ability to recursively call dlopen is useful for malloc implementations that wish to load other dynamic modules that implement reentrant/AS-safe functions to use in their own implementation. Given that a user malloc implementation may be called by an ongoing dlopen to allocate memory the user malloc implementation interrupts dlopen and if it calls dlopen again that's a reentrant call. This patch fixes the issues with the ld.so.cache mapping and the _r_debug assertion which prevent this from working as expected. See: https://sourceware.org/ml/libc-alpha/2014-12/msg00446.html
Diffstat (limited to 'dlfcn/tst-rec-dlopen.c')
-rw-r--r--dlfcn/tst-rec-dlopen.c144
1 files changed, 144 insertions, 0 deletions
diff --git a/dlfcn/tst-rec-dlopen.c b/dlfcn/tst-rec-dlopen.c
new file mode 100644
index 0000000..35b08d4
--- /dev/null
+++ b/dlfcn/tst-rec-dlopen.c
@@ -0,0 +1,144 @@
+/* Test recursive dlopen using malloc hooks.
+ Copyright (C) 1998-2014 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
+
+ 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
+ <http://www.gnu.org/licenses/>. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <malloc.h>
+#include <dlfcn.h>
+
+#define DSO "moddummy1.so"
+#define FUNC "dummy1"
+
+#define DSO1 "moddummy2.so"
+#define FUNC1 "dummy2"
+
+/* Result of the called function. */
+int func_result;
+
+/* Prototype for my hook. */
+void *custom_malloc_hook (size_t, const void *);
+
+/* Pointer to old malloc hooks. */
+void *(*old_malloc_hook) (size_t, const void *);
+
+/* Call function func_name in DSO dso_name via dlopen. */
+void
+call_func (const char *dso_name, const char *func_name)
+{
+ int ret;
+ void *dso;
+ int (*func) (void);
+ char *err;
+
+ /* Open the DSO. */
+ dso = dlopen (dso_name, RTLD_NOW|RTLD_GLOBAL);
+ if (dso == NULL)
+ {
+ err = dlerror ();
+ fprintf (stderr, "%s\n", err);
+ exit (1);
+ }
+ /* Clear any errors. */
+ dlerror ();
+
+ /* Lookup func. */
+ *(void **) (&func) = dlsym (dso, func_name);
+ if (func == NULL)
+ {
+ err = dlerror ();
+ if (err != NULL)
+ {
+ fprintf (stderr, "%s\n", err);
+ exit (1);
+ }
+ }
+ /* Call func. */
+ func_result = (*func) ();
+
+ /* Close the library and look for errors too. */
+ ret = dlclose (dso);
+ if (ret != 0)
+ {
+ err = dlerror ();
+ fprintf (stderr, "%s\n", err);
+ exit (1);
+ }
+
+}
+
+/* Empty hook that does nothing. */
+void *
+custom_malloc_hook (size_t size, const void *caller)
+{
+ void *result;
+ /* Restore old hooks. */
+ __malloc_hook = old_malloc_hook;
+ /* First call a function in another library via dlopen. */
+ call_func (DSO1, FUNC1);
+ /* Called recursively. */
+ result = malloc (size);
+ /* Restore new hooks. */
+ __malloc_hook = custom_malloc_hook;
+ return result;
+}
+
+static int
+do_test (void)
+{
+ /* Save old hook. */
+ old_malloc_hook = __malloc_hook;
+ /* Install new hook. */
+ __malloc_hook = custom_malloc_hook;
+
+ /* Bug 17702 fixes two things:
+ * A recursive dlopen unmapping the ld.so.cache.
+ * An assertion that _r_debug is RT_CONSISTENT at entry to dlopen.
+ We can only test the latter. Testing the former requires modifying
+ ld.so.conf to cache the dummy libraries, then running ldconfig,
+ then run the test. If you do all of that (and glibc's test
+ infrastructure doesn't support that yet) then the test will
+ SEGFAULT without the fix. If you don't do that, then the test
+ will abort because of the assert described in detail below. */
+ call_func (DSO, FUNC);
+
+ /* Restore old hook. */
+ __malloc_hook = old_malloc_hook;
+
+ /* The function dummy2() is called by the malloc hook. Check to
+ see that it was called. This ensures the second recursive
+ dlopen happened and we called the function in that library.
+ Before the fix you either get a SIGSEGV when accessing mmap'd
+ ld.so.cache data or an assertion failure about _r_debug not
+ beint RT_CONSISTENT. We don't test for the SIGSEGV since it
+ would require finding moddummy1 or moddummy2 in the cache and
+ we don't have any infrastructure to test that, but the _r_debug
+ assertion triggers. */
+ printf ("Returned result is %d\n", func_result);
+ if (func_result <= 0)
+ {
+ printf ("FAIL: Function call_func() not called.\n");
+ exit (1);
+ }
+
+ printf ("PASS: Function call_func() called more than once.\n");
+ return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"