[glibc] Fix getting return address in elf/tst-audit28.c.

[Stefan Liebler <stli@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=5d72e7e41a7860b911251bfc8dd3641460cc20a0

commit 5d72e7e41a7860b911251bfc8dd3641460cc20a0
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Thu Jul 13 15:13:48 2023 +0200

    Fix getting return address in elf/tst-audit28.c.
    
    Starting with commit 1bcfe0f732066ae5336b252295591ebe7e51c301, the
    test was enhanced and the object for __builtin_return_address (0)
    is searched with _dl_find_object.
    
    Unfortunately on e.g. s390 (31bit), a postprocessing step is needed
    as the highest bit has to be masked out.  This can be done with
    __builtin_extract_return_addr.
    
    Without this postprocessing, _dl_find_object returns with -1 and the
    content of dlfo is invalid, which may lead to segfaults in basename.
    Therefore those checks are now only done on success.
    Reviewed-by: Florian Weimer <fweimer@redhat.com>

Diff:
---
 elf/tst-auditmod28.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/elf/tst-auditmod28.c b/elf/tst-auditmod28.c
index f6dfbbe202..35180208ba 100644
--- a/elf/tst-auditmod28.c
+++ b/elf/tst-auditmod28.c
@@ -73,12 +73,19 @@ la_version (unsigned int current)
 
   /* Check _dl_find_object.  */
   struct dl_find_object dlfo;
-  TEST_COMPARE (_dl_find_object (__builtin_return_address (0), &dlfo), 0);
-  /* "ld.so" is seen with --enable-hardcoded-path-in-tests.  */
-  if (strcmp (basename (dlfo.dlfo_link_map->l_name), "ld.so") != 0)
-    TEST_COMPARE_STRING (basename (dlfo.dlfo_link_map->l_name), LD_SO);
-  TEST_COMPARE (_dl_find_object (dlsym (handle, "environ"), &dlfo), 0);
-  TEST_COMPARE_STRING (basename (dlfo.dlfo_link_map->l_name), LIBC_SO);
+  void *ret_addr = __builtin_extract_return_addr (__builtin_return_address (0));
+  int ret_dl_find_object =_dl_find_object (ret_addr, &dlfo);
+  TEST_COMPARE (ret_dl_find_object, 0);
+  if (ret_dl_find_object == 0)
+    {
+      /* "ld.so" is seen with --enable-hardcoded-path-in-tests.  */
+      if (strcmp (basename (dlfo.dlfo_link_map->l_name), "ld.so") != 0)
+	TEST_COMPARE_STRING (basename (dlfo.dlfo_link_map->l_name), LD_SO);
+    }
+  ret_dl_find_object = _dl_find_object (dlsym (handle, "environ"), &dlfo);
+  TEST_COMPARE (ret_dl_find_object, 0);
+  if (ret_dl_find_object == 0)
+    TEST_COMPARE_STRING (basename (dlfo.dlfo_link_map->l_name), LIBC_SO);
   TEST_COMPARE (_dl_find_object ((void *) 1, &dlfo), -1);
   TEST_COMPARE (_dl_find_object ((void *) -1, &dlfo), -1);