diff mbox series

[2/5] elf: Avoid unnecessary slowdown from profiling with audit (BZ#15533)

Message ID 20210707182610.3940620-3-adhemerval.zanella@linaro.org
State Superseded
Headers show
Series Some rtld-audit fixes | expand

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent

Commit Message

Adhemerval Zanella July 7, 2021, 6:26 p.m. UTC
The rtld-audit interfaces introduce a slowdown due to enabling profiling
instrumentation (as if LD_AUDIT implied LD_PROFILE).  However, instrumenting
is only necessary if one of audit libraries provides PLT (la_plt{enter,exit}
symbols) or symbol bynding (la_symbind{32,64})hooks.  Otherwise, the
slowdown can be avoided.

The following patch adjusts the logic that enables profiling to iterate
over all audit modules and check if any of those provides a PLT hook.

Co-authored-by: Alexander Monakov <amonakov@ispras.dot.ru>
---
 elf/Makefile          | 13 +++++++++++-
 elf/dl-reloc.c        | 13 +++++++++++-
 elf/rtld.c            |  8 +-------
 elf/tst-audit18a.c    | 39 +++++++++++++++++++++++++++++++++++
 elf/tst-audit18b.c    | 30 +++++++++++++++++++++++++++
 elf/tst-audit18bmod.c | 22 ++++++++++++++++++++
 elf/tst-auditmod18a.c | 25 ++++++++++++++++++++++
 elf/tst-auditmod18b.c | 48 +++++++++++++++++++++++++++++++++++++++++++
 include/link.h        |  2 ++
 9 files changed, 191 insertions(+), 9 deletions(-)
 create mode 100644 elf/tst-audit18a.c
 create mode 100644 elf/tst-audit18b.c
 create mode 100644 elf/tst-audit18bmod.c
 create mode 100644 elf/tst-auditmod18a.c
 create mode 100644 elf/tst-auditmod18b.c

Comments

Florian Weimer July 7, 2021, 7:20 p.m. UTC | #1
* Adhemerval Zanella via Libc-alpha:

> diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
> index e13a672ade..998cfef099 100644
> --- a/elf/dl-reloc.c
> +++ b/elf/dl-reloc.c
> @@ -181,7 +181,18 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
>  #ifdef SHARED
>    /* If we are auditing, install the same handlers we need for profiling.  */
>    if ((reloc_mode & __RTLD_AUDIT) == 0)
> -    consider_profiling |= GLRO(dl_audit) != NULL;
> +    {
> +      struct audit_ifaces *afct = GLRO(dl_audit);
> +      for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
> +	{
> +	  /* Profiling is needed only if PLT hooks are provided.  */
> +	  if (afct->symbind != NULL
> +	      || afct->ARCH_LA_PLTENTER != NULL
> +	      || afct->ARCH_LA_PLTEXIT != NULL)
> +	    consider_profiling = 1;
> +	  afct = afct->next;
> +	}
> +    }

Is the afct->symbind check really necessary?  Looking at _dl_fixup, it
should be safe to call symbind with just the standard trampoline.

I think this needs a NEWS entry, describing how to activate this
optimization.

Thanks,
Florian
Adhemerval Zanella July 7, 2021, 8:05 p.m. UTC | #2
On 07/07/2021 16:20, Florian Weimer wrote:
> * Adhemerval Zanella via Libc-alpha:
> 
>> diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
>> index e13a672ade..998cfef099 100644
>> --- a/elf/dl-reloc.c
>> +++ b/elf/dl-reloc.c
>> @@ -181,7 +181,18 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
>>  #ifdef SHARED
>>    /* If we are auditing, install the same handlers we need for profiling.  */
>>    if ((reloc_mode & __RTLD_AUDIT) == 0)
>> -    consider_profiling |= GLRO(dl_audit) != NULL;
>> +    {
>> +      struct audit_ifaces *afct = GLRO(dl_audit);
>> +      for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
>> +	{
>> +	  /* Profiling is needed only if PLT hooks are provided.  */
>> +	  if (afct->symbind != NULL
>> +	      || afct->ARCH_LA_PLTENTER != NULL
>> +	      || afct->ARCH_LA_PLTEXIT != NULL)
>> +	    consider_profiling = 1;
>> +	  afct = afct->next;
>> +	}
>> +    }
> 
> Is the afct->symbind check really necessary?  Looking at _dl_fixup, it
> should be safe to call symbind with just the standard trampoline.

Yes, elf/tst-audit18b check specifically for this.  Without it,
returning LA_FLG_BINDFROM | LA_FLG_BINDTO from la_objopen() won't
trigger a la_symbind{32,64}.

> 
> I think this needs a NEWS entry, describing how to activate this
> optimization.

I can add a NEW entry, although it is not really a 'new feature'.
What about:

  * The audit libraries will avoid unnecessary slowdown if it is not
    required either PLT tracking or symbol binding profiling (enabled
    with LA_FLG_BINDFROM or LA_FLG_BINDTO from la_objopen() callback).
Florian Weimer July 7, 2021, 8:15 p.m. UTC | #3
* Adhemerval Zanella:

> On 07/07/2021 16:20, Florian Weimer wrote:
>> * Adhemerval Zanella via Libc-alpha:
>> 
>>> diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
>>> index e13a672ade..998cfef099 100644
>>> --- a/elf/dl-reloc.c
>>> +++ b/elf/dl-reloc.c
>>> @@ -181,7 +181,18 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
>>>  #ifdef SHARED
>>>    /* If we are auditing, install the same handlers we need for profiling.  */
>>>    if ((reloc_mode & __RTLD_AUDIT) == 0)
>>> -    consider_profiling |= GLRO(dl_audit) != NULL;
>>> +    {
>>> +      struct audit_ifaces *afct = GLRO(dl_audit);
>>> +      for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
>>> +	{
>>> +	  /* Profiling is needed only if PLT hooks are provided.  */
>>> +	  if (afct->symbind != NULL
>>> +	      || afct->ARCH_LA_PLTENTER != NULL
>>> +	      || afct->ARCH_LA_PLTEXIT != NULL)
>>> +	    consider_profiling = 1;
>>> +	  afct = afct->next;
>>> +	}
>>> +    }
>> 
>> Is the afct->symbind check really necessary?  Looking at _dl_fixup, it
>> should be safe to call symbind with just the standard trampoline.
>
> Yes, elf/tst-audit18b check specifically for this.  Without it,
> returning LA_FLG_BINDFROM | LA_FLG_BINDTO from la_objopen() won't
> trigger a la_symbind{32,64}.

Hmm, I'm surprised we get a la_symbind call with BIND_NOW at all.  And
for BIND_NOW the choice of trampoline really should not matter anyway.

Anyway, I think we have a feature request that without
la_ltenter/la_pltexit defined, the presence of la_symbind should not
incur the overhead from the profiling trampoline.  The afct->symbind
check defeats that.

Thanks,
Florian
John Mellor-Crummey July 7, 2021, 8:53 p.m. UTC | #4
Forian is correct that what the HPCToolkit team wants is to use la_symbind without la_ltenter/la_pltexit defined.  We don’t want the overhead from the profiling trampoline just to get the la_symbind call.
--
John Mellor-Crummey		Professor
Dept of Computer Science	Rice University
email: johnmc@rice.edu		phone: 713-348-5179

> On Jul 7, 2021, at 3:15 PM, Florian Weimer <fweimer@redhat.com> wrote:
> 
> * Adhemerval Zanella:
> 
>> On 07/07/2021 16:20, Florian Weimer wrote:
>>> * Adhemerval Zanella via Libc-alpha:
>>> 
>>>> diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
>>>> index e13a672ade..998cfef099 100644
>>>> --- a/elf/dl-reloc.c
>>>> +++ b/elf/dl-reloc.c
>>>> @@ -181,7 +181,18 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
>>>> #ifdef SHARED
>>>>   /* If we are auditing, install the same handlers we need for profiling.  */
>>>>   if ((reloc_mode & __RTLD_AUDIT) == 0)
>>>> -    consider_profiling |= GLRO(dl_audit) != NULL;
>>>> +    {
>>>> +      struct audit_ifaces *afct = GLRO(dl_audit);
>>>> +      for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
>>>> +	{
>>>> +	  /* Profiling is needed only if PLT hooks are provided.  */
>>>> +	  if (afct->symbind != NULL
>>>> +	      || afct->ARCH_LA_PLTENTER != NULL
>>>> +	      || afct->ARCH_LA_PLTEXIT != NULL)
>>>> +	    consider_profiling = 1;
>>>> +	  afct = afct->next;
>>>> +	}
>>>> +    }
>>> 
>>> Is the afct->symbind check really necessary?  Looking at _dl_fixup, it
>>> should be safe to call symbind with just the standard trampoline.
>> 
>> Yes, elf/tst-audit18b check specifically for this.  Without it,
>> returning LA_FLG_BINDFROM | LA_FLG_BINDTO from la_objopen() won't
>> trigger a la_symbind{32,64}.
> 
> Hmm, I'm surprised we get a la_symbind call with BIND_NOW at all.  And
> for BIND_NOW the choice of trampoline really should not matter anyway.
> 
> Anyway, I think we have a feature request that without
> la_ltenter/la_pltexit defined, the presence of la_symbind should not
> incur the overhead from the profiling trampoline.  The afct->symbind
> check defeats that.
> 
> Thanks,
> Florian
>
Adhemerval Zanella July 19, 2021, 1:17 p.m. UTC | #5
On 07/07/2021 17:15, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> On 07/07/2021 16:20, Florian Weimer wrote:
>>> * Adhemerval Zanella via Libc-alpha:
>>>
>>>> diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
>>>> index e13a672ade..998cfef099 100644
>>>> --- a/elf/dl-reloc.c
>>>> +++ b/elf/dl-reloc.c
>>>> @@ -181,7 +181,18 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
>>>>  #ifdef SHARED
>>>>    /* If we are auditing, install the same handlers we need for profiling.  */
>>>>    if ((reloc_mode & __RTLD_AUDIT) == 0)
>>>> -    consider_profiling |= GLRO(dl_audit) != NULL;
>>>> +    {
>>>> +      struct audit_ifaces *afct = GLRO(dl_audit);
>>>> +      for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
>>>> +	{
>>>> +	  /* Profiling is needed only if PLT hooks are provided.  */
>>>> +	  if (afct->symbind != NULL
>>>> +	      || afct->ARCH_LA_PLTENTER != NULL
>>>> +	      || afct->ARCH_LA_PLTEXIT != NULL)
>>>> +	    consider_profiling = 1;
>>>> +	  afct = afct->next;
>>>> +	}
>>>> +    }
>>>
>>> Is the afct->symbind check really necessary?  Looking at _dl_fixup, it
>>> should be safe to call symbind with just the standard trampoline.
>>
>> Yes, elf/tst-audit18b check specifically for this.  Without it,
>> returning LA_FLG_BINDFROM | LA_FLG_BINDTO from la_objopen() won't
>> trigger a la_symbind{32,64}.
> 
> Hmm, I'm surprised we get a la_symbind call with BIND_NOW at all.  And
> for BIND_NOW the choice of trampoline really should not matter anyway.
> 
> Anyway, I think we have a feature request that without
> la_ltenter/la_pltexit defined, the presence of la_symbind should not
> incur the overhead from the profiling trampoline.  The afct->symbind
> check defeats that.

Indeed, we will need to track the la_symbind for bind-now in a different 
fix then.  I will update the patch.
diff mbox series

Patch

diff --git a/elf/Makefile b/elf/Makefile
index 5214196de6..a26f5ce320 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -219,7 +219,8 @@  tests += restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-dlopen-self tst-auditmany tst-initfinilazyfail tst-dlopenfail \
 	 tst-dlopenfail-2 \
 	 tst-filterobj tst-filterobj-dlopen tst-auxobj tst-auxobj-dlopen \
-	 tst-audit14 tst-audit15 tst-audit16 tst-audit17 \
+	 tst-audit14 tst-audit15 tst-audit16 tst-audit17 tst-audit18a \
+	 tst-audit18b \
 	 tst-single_threaded tst-single_threaded-pthread \
 	 tst-tls-ie tst-tls-ie-dlmopen argv0test \
 	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
@@ -294,6 +295,7 @@  modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		tst-unique1mod1 tst-unique1mod2 \
 		tst-unique2mod1 tst-unique2mod2 \
 		tst-auditmod9a tst-auditmod9b \
+		tst-auditmod18a tst-audit18bmod tst-auditmod18b \
 		$(if $(CXX),tst-unique3lib tst-unique3lib2 tst-unique4lib \
 		  tst-nodelete-uniquemod tst-nodelete-rtldmod \
 		  tst-nodelete-zmod \
@@ -1478,6 +1480,15 @@  $(objpfx)tst-auditmod17.so: $(objpfx)tst-auditmod17.os
 	mv -f $@.new $@
 tst-audit17-ENV = LD_AUDIT=$(objpfx)tst-auditmod17.so
 
+$(objpfx)tst-audit18a.out: $(objpfx)tst-auditmod18a.so
+tst-audit18a-ENV = LD_AUDIT=$(objpfx)tst-auditmod18a.so
+$(objpfx)tst-audit18b.out: $(objpfx)tst-auditmod18b.so \
+			   $(objpfx)tst-audit18bmod.so
+$(objpfx)tst-audit18b: $(objpfx)tst-audit18bmod.so
+LDFLAGS-tst-audit18bmod.so = -Wl,-z,now
+LDFLAGS-tst-audit18b = -Wl,-z,now
+tst-audit18b-ENV = LD_AUDIT=$(objpfx)tst-auditmod18b.so
+
 # tst-sonamemove links against an older implementation of the library.
 LDFLAGS-tst-sonamemove-linkmod1.so = \
   -Wl,--version-script=tst-sonamemove-linkmod1.map \
diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
index e13a672ade..998cfef099 100644
--- a/elf/dl-reloc.c
+++ b/elf/dl-reloc.c
@@ -181,7 +181,18 @@  _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
 #ifdef SHARED
   /* If we are auditing, install the same handlers we need for profiling.  */
   if ((reloc_mode & __RTLD_AUDIT) == 0)
-    consider_profiling |= GLRO(dl_audit) != NULL;
+    {
+      struct audit_ifaces *afct = GLRO(dl_audit);
+      for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
+	{
+	  /* Profiling is needed only if PLT hooks are provided.  */
+	  if (afct->symbind != NULL
+	      || afct->ARCH_LA_PLTENTER != NULL
+	      || afct->ARCH_LA_PLTEXIT != NULL)
+	    consider_profiling = 1;
+	  afct = afct->next;
+	}
+    }
 #elif defined PROF
   /* Never use dynamic linker profiling for gprof profiling code.  */
 # define consider_profiling 0
diff --git a/elf/rtld.c b/elf/rtld.c
index fbbd60b446..bf9eb5a33e 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1014,13 +1014,7 @@  ERROR: audit interface '%s' requires version %d (maximum supported version %d);
     "la_objsearch\0"
     "la_objopen\0"
     "la_preinit\0"
-#if __ELF_NATIVE_CLASS == 32
-    "la_symbind32\0"
-#elif __ELF_NATIVE_CLASS == 64
-    "la_symbind64\0"
-#else
-# error "__ELF_NATIVE_CLASS must be defined"
-#endif
+    LA_SYMBIND "\0"
 #define STRING(s) __STRING (s)
     "la_" STRING (ARCH_LA_PLTENTER) "\0"
     "la_" STRING (ARCH_LA_PLTEXIT) "\0"
diff --git a/elf/tst-audit18a.c b/elf/tst-audit18a.c
new file mode 100644
index 0000000000..36b781f9be
--- /dev/null
+++ b/elf/tst-audit18a.c
@@ -0,0 +1,39 @@ 
+/* Check if DT_AUDIT a module without la_plt{enter,exit} symbols does not incur
+   in profiling (BZ#15533).
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <link.h>
+#include <stdio.h>
+
+/* We interpose the profile resolver and if it is called it means profiling is
+   enabled.  */
+void
+_dl_runtime_profile (ElfW(Word) addr)
+{
+  volatile int *p = NULL;
+  *p = 0;
+}
+
+static int
+do_test (void)
+{
+  printf ("...");
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-audit18b.c b/elf/tst-audit18b.c
new file mode 100644
index 0000000000..21381fe950
--- /dev/null
+++ b/elf/tst-audit18b.c
@@ -0,0 +1,30 @@ 
+/* Check if DT_AUDIT a module built with bind-now does trigger la_symbind.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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
+   <https://www.gnu.org/licenses/>.  */
+
+extern int foo (void);
+
+int
+do_test (void)
+{
+  foo ();
+  /* If audit la_symbind() callback is called it will exit the test with
+      EXIT_SUCCESS.  */
+  return 1;
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-audit18bmod.c b/elf/tst-audit18bmod.c
new file mode 100644
index 0000000000..91f171b5bc
--- /dev/null
+++ b/elf/tst-audit18bmod.c
@@ -0,0 +1,22 @@ 
+/* Check if DT_AUDIT a module built with bind-now does trigger la_symbind.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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
+   <https://www.gnu.org/licenses/>.  */
+
+int foo (void)
+{
+  return 0;
+}
diff --git a/elf/tst-auditmod18a.c b/elf/tst-auditmod18a.c
new file mode 100644
index 0000000000..333db0077c
--- /dev/null
+++ b/elf/tst-auditmod18a.c
@@ -0,0 +1,25 @@ 
+/* Check if DT_ADIT a module without la_plt{enter,exit} symbols does not incur
+   in profiling (BZ#15533).
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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
+   <https://www.gnu.org/licenses/>.  */
+
+unsigned int
+la_version (unsigned int version)
+{
+  return version;
+}
+
diff --git a/elf/tst-auditmod18b.c b/elf/tst-auditmod18b.c
new file mode 100644
index 0000000000..40ebcd5be2
--- /dev/null
+++ b/elf/tst-auditmod18b.c
@@ -0,0 +1,48 @@ 
+/* Check if DT_AUDIT a module built with bind-now does trigger la_symbind.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <link.h>
+#include <stdlib.h>
+#include <string.h>
+
+unsigned int
+la_version (unsigned int version)
+{
+  return version;
+}
+
+unsigned int
+la_objopen (struct link_map* map, Lmid_t lmid, uintptr_t* cookie)
+{
+  return LA_FLG_BINDFROM | LA_FLG_BINDTO;
+}
+
+uintptr_t
+#if __ELF_NATIVE_CLASS == 32
+la_symbind32 (Elf32_Sym *sym, unsigned int ndx, uintptr_t *refcook,
+              uintptr_t *defcook, unsigned int *flags, const char *symname)
+#else
+la_symbind64 (Elf64_Sym *sym, unsigned int ndx, uintptr_t *refcook,
+              uintptr_t *defcook, unsigned int *flags, const char *symname)
+#endif
+{
+  /* Filter out glibc own symbols libc.so is not built with -z,now.  */
+  if (strcmp (symname, "foo") == 0)
+    exit (EXIT_SUCCESS);
+  return sym->st_value;
+} 
diff --git a/include/link.h b/include/link.h
index 4af16cb596..ebd0f511e2 100644
--- a/include/link.h
+++ b/include/link.h
@@ -355,8 +355,10 @@  struct auditstate
 
 #if __ELF_NATIVE_CLASS == 32
 # define symbind symbind32
+# define LA_SYMBIND "la_symbind32"
 #elif __ELF_NATIVE_CLASS == 64
 # define symbind symbind64
+# define LA_SYMBIND "la_symbind64"
 #else
 # error "__ELF_NATIVE_CLASS must be defined"
 #endif