nptl_db: Support different libpthread/ld.so load orders (bug 27744)

libthread_db is loaded once GDB encounters libpthread, and at this
point, ld.so may not have been processed by GDB yet. As a result,
_rtld_global cannot be accessed by regular means from libthread_db.
To make this work until GDB can be fixed, acess _rtld_global through
a pointer stored in libpthread.

The new test does not reproduce bug 27744 with
--disable-hardcoded-path-in-tests, but is still a valid smoke test.
With --enable-hardcoded-path-in-tests, it is necessary to avoid
add-symbol-file because this can tickle a GDB bug.

Fixes commit 1daccf403b1bd86370eb94edca794dc106d02039 ("nptl: Move
stack list variables into _rtld_global").

Tested-by: Emil Velikov <emil.velikov@collabora.com>

1 files changed, 8 insertions, 7 deletions

diff --git a/nptl_db/td_init.c b/nptl_db/td_init.c
index 1d15681228..06b5adc5c2 100644
--- a/nptl_db/td_init.c
+++ b/nptl_db/td_init.c
@@ -33,13 +33,14 @@ td_init (void)
 bool
 __td_ta_rtld_global (td_thragent_t *ta)
 {
-  if (ta->ta_addr__rtld_global == 0
-      && td_mod_lookup (ta->ph, LD_SO, SYM__rtld_global,
-                        &ta->ta_addr__rtld_global) != PS_OK)
+  if (ta->ta_addr__rtld_global == 0)
     {
-      ta->ta_addr__rtld_global = (void*)-1;
-      return false;
+      psaddr_t rtldglobalp;
+      if (DB_GET_VALUE (rtldglobalp, ta, __nptl_rtld_global, 0) == TD_OK)
+        ta->ta_addr__rtld_global = rtldglobalp;
+      else
+        ta->ta_addr__rtld_global = (void *) -1;
     }
-  else
-    return ta->ta_addr__rtld_global != (void*)-1;
+
+  return ta->ta_addr__rtld_global != (void *)-1;
 }