diff mbox series

[v10,1/4] elf: Add la_activity during application exit

Message ID 20220117213136.1327053-2-adhemerval.zanella@linaro.org
State Superseded
Headers show
Series Multiple 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 Jan. 17, 2022, 9:31 p.m. UTC
la_activity is not called during application exit, even though
la_objclose is.

Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.
---
 elf/Makefile         |   7 ++
 elf/dl-fini.c        |  10 ++
 elf/tst-audit23.c    | 239 +++++++++++++++++++++++++++++++++++++++++++
 elf/tst-audit23mod.c |  23 +++++
 elf/tst-auditmod23.c |  74 ++++++++++++++
 5 files changed, 353 insertions(+)
 create mode 100644 elf/tst-audit23.c
 create mode 100644 elf/tst-audit23mod.c
 create mode 100644 elf/tst-auditmod23.c

Comments

Florian Weimer Jan. 18, 2022, 11:29 a.m. UTC | #1
* Adhemerval Zanella via Libc-alpha:

> diff --git a/elf/dl-fini.c b/elf/dl-fini.c
> index de8eb1b3c9..2705a15c88 100644
> --- a/elf/dl-fini.c
> +++ b/elf/dl-fini.c
> @@ -64,6 +64,11 @@ _dl_fini (void)
>  	__rtld_lock_unlock_recursive (GL(dl_load_lock));
>        else
>  	{
> +#ifdef SHARED
> +	  /* Auditing checkpoint: we will start deleting objects.  */
> +	  _dl_audit_activity_nsid (ns, LA_ACT_DELETE);
> +#endif
> +
>  	  /* Now we can allocate an array to hold all the pointers and
>  	     copy the pointers in.  */
>  	  struct link_map *maps[nloaded];
> @@ -153,6 +158,11 @@ _dl_fini (void)
>  	      /* Correct the previous increment.  */
>  	      --l->l_direct_opencount;
>  	    }
> +
> +#ifdef SHARED
> +	  /* Auditing checkpoint: we will start deleting objects.  */
> +	  _dl_audit_activity_nsid (ns, LA_ACT_CONSISTENT);
> +#endif
>  	}
>      }

The tense in the second comment seems wrong.

>  
> diff --git a/elf/tst-audit23.c b/elf/tst-audit23.c
> new file mode 100644
> index 0000000000..9a7e69c1e1
> --- /dev/null
> +++ b/elf/tst-audit23.c

> +  FILE *out = fmemopen (result.err.buffer, result.err.length, "r");
> +  TEST_VERIFY (out != NULL);
> +  char *buffer = NULL;
> +  size_t buffer_length = 0;
> +  while (xgetline (&buffer, &buffer_length, out))
> +    {
> +      if (startswith (buffer, "la_activity: "))

It may be simpler (or easier to maintain going forward) to have the
expected output (without varying pointers) and compare against that
verbatim.  This is what I implemented for some of the DNS tests.

Thanks,
Florian
Adhemerval Zanella Jan. 18, 2022, 1:10 p.m. UTC | #2
On 18/01/2022 08:29, Florian Weimer wrote:
> * Adhemerval Zanella via Libc-alpha:
> 
>> diff --git a/elf/dl-fini.c b/elf/dl-fini.c
>> index de8eb1b3c9..2705a15c88 100644
>> --- a/elf/dl-fini.c
>> +++ b/elf/dl-fini.c
>> @@ -64,6 +64,11 @@ _dl_fini (void)
>>  	__rtld_lock_unlock_recursive (GL(dl_load_lock));
>>        else
>>  	{
>> +#ifdef SHARED
>> +	  /* Auditing checkpoint: we will start deleting objects.  */
>> +	  _dl_audit_activity_nsid (ns, LA_ACT_DELETE);
>> +#endif
>> +
>>  	  /* Now we can allocate an array to hold all the pointers and
>>  	     copy the pointers in.  */
>>  	  struct link_map *maps[nloaded];
>> @@ -153,6 +158,11 @@ _dl_fini (void)
>>  	      /* Correct the previous increment.  */
>>  	      --l->l_direct_opencount;
>>  	    }
>> +
>> +#ifdef SHARED
>> +	  /* Auditing checkpoint: we will start deleting objects.  */
>> +	  _dl_audit_activity_nsid (ns, LA_ACT_CONSISTENT);
>> +#endif
>>  	}
>>      }
> 
> The tense in the second comment seems wrong.

Ack, in fact I think both comments do not add much (it is pretty obvious
from the function call).  I will remove them.

> 
>>  
>> diff --git a/elf/tst-audit23.c b/elf/tst-audit23.c
>> new file mode 100644
>> index 0000000000..9a7e69c1e1
>> --- /dev/null
>> +++ b/elf/tst-audit23.c
> 
>> +  FILE *out = fmemopen (result.err.buffer, result.err.length, "r");
>> +  TEST_VERIFY (out != NULL);
>> +  char *buffer = NULL;
>> +  size_t buffer_length = 0;
>> +  while (xgetline (&buffer, &buffer_length, out))
>> +    {
>> +      if (startswith (buffer, "la_activity: "))
> 
> It may be simpler (or easier to maintain going forward) to have the
> expected output (without varying pointers) and compare against that
> verbatim.  This is what I implemented for some of the DNS tests.

The main issue is to handle the vDSO (is_vdso) and match the cookies
and address with the subsequent la_activities/la_objclose.  So it
would require to keep track with some internal state anyway.

And checking on resolve/tst-ns_name.c I don't think it would be
simpler to use such scheme (specially the required handling it would 
require to parse a possible input to handle line with multiple options
and different outputs).
Florian Weimer Jan. 21, 2022, 10:50 a.m. UTC | #3
* Adhemerval Zanella via Libc-alpha:

> +static int
> +do_test (int argc, char *argv[])
> +{
> +  /* We must have either:
> +     - One our fource parameters left if called initially:
> +       + path to ld.so         optional
> +       + "--library-path"      optional
> +       + the library path      optional
> +       + the application name  */
> +  if (restart)
> +    return handle_restart ();
> +
> +  char *spargv[9];
> +  int i = 0;
> +  for (; i < argc - 1; i++)
> +    spargv[i] = argv[i + 1];
> +  spargv[i++] = (char *) "--direct";
> +  spargv[i++] = (char *) "--restart";
> +  spargv[i] = NULL;

Please add a check for an out-of-range argc value, or allocate the array
on the heap.

> +  while (xgetline (&buffer, &buffer_length, out))
> +    {
> +      if (startswith (buffer, "la_activity: "))
> +	{
> +	  uintptr_t cookie;
> +	  int this_act;
> +	  int r = sscanf (buffer + strlen ("la_activity: "),
> +			  "%d %"SCNxPTR"", &this_act, &cookie);
> +	  TEST_COMPARE (r, 2);

I wonder if you can fold the startswith check into the sscanf.  At least
you could put "la_activity: " into the format string.

Thanks,
Florian
Florian Weimer Jan. 21, 2022, 10:50 a.m. UTC | #4
* Adhemerval Zanella:

> On 18/01/2022 08:29, Florian Weimer wrote:
>> * Adhemerval Zanella via Libc-alpha:
>> 
>>> diff --git a/elf/dl-fini.c b/elf/dl-fini.c
>>> index de8eb1b3c9..2705a15c88 100644
>>> --- a/elf/dl-fini.c
>>> +++ b/elf/dl-fini.c
>>> @@ -64,6 +64,11 @@ _dl_fini (void)
>>>  	__rtld_lock_unlock_recursive (GL(dl_load_lock));
>>>        else
>>>  	{
>>> +#ifdef SHARED
>>> +	  /* Auditing checkpoint: we will start deleting objects.  */
>>> +	  _dl_audit_activity_nsid (ns, LA_ACT_DELETE);
>>> +#endif
>>> +
>>>  	  /* Now we can allocate an array to hold all the pointers and
>>>  	     copy the pointers in.  */
>>>  	  struct link_map *maps[nloaded];
>>> @@ -153,6 +158,11 @@ _dl_fini (void)
>>>  	      /* Correct the previous increment.  */
>>>  	      --l->l_direct_opencount;
>>>  	    }
>>> +
>>> +#ifdef SHARED
>>> +	  /* Auditing checkpoint: we will start deleting objects.  */
>>> +	  _dl_audit_activity_nsid (ns, LA_ACT_CONSISTENT);
>>> +#endif
>>>  	}
>>>      }
>> 
>> The tense in the second comment seems wrong.
>
> Ack, in fact I think both comments do not add much (it is pretty obvious
> from the function call).  I will remove them.
>
>> 
>>>  
>>> diff --git a/elf/tst-audit23.c b/elf/tst-audit23.c
>>> new file mode 100644
>>> index 0000000000..9a7e69c1e1
>>> --- /dev/null
>>> +++ b/elf/tst-audit23.c
>> 
>>> +  FILE *out = fmemopen (result.err.buffer, result.err.length, "r");
>>> +  TEST_VERIFY (out != NULL);
>>> +  char *buffer = NULL;
>>> +  size_t buffer_length = 0;
>>> +  while (xgetline (&buffer, &buffer_length, out))
>>> +    {
>>> +      if (startswith (buffer, "la_activity: "))
>> 
>> It may be simpler (or easier to maintain going forward) to have the
>> expected output (without varying pointers) and compare against that
>> verbatim.  This is what I implemented for some of the DNS tests.
>
> The main issue is to handle the vDSO (is_vdso) and match the cookies
> and address with the subsequent la_activities/la_objclose.  So it
> would require to keep track with some internal state anyway.
>
> And checking on resolve/tst-ns_name.c I don't think it would be
> simpler to use such scheme (specially the required handling it would 
> require to parse a possible input to handle line with multiple options
> and different outputs).

Okay, I just found the existing test rather difficult to review.

Thanks,
Florian
Adhemerval Zanella Jan. 24, 2022, 12:53 p.m. UTC | #5
On 21/01/2022 07:50, Florian Weimer wrote:
> * Adhemerval Zanella via Libc-alpha:
> 
>> +static int
>> +do_test (int argc, char *argv[])
>> +{
>> +  /* We must have either:
>> +     - One our fource parameters left if called initially:
>> +       + path to ld.so         optional
>> +       + "--library-path"      optional
>> +       + the library path      optional
>> +       + the application name  */
>> +  if (restart)
>> +    return handle_restart ();
>> +
>> +  char *spargv[9];
>> +  int i = 0;
>> +  for (; i < argc - 1; i++)
>> +    spargv[i] = argv[i + 1];
>> +  spargv[i++] = (char *) "--direct";
>> +  spargv[i++] = (char *) "--restart";
>> +  spargv[i] = NULL;
> 
> Please add a check for an out-of-range argc value, or allocate the array
> on the heap.

Ack.

> 
>> +  while (xgetline (&buffer, &buffer_length, out))
>> +    {
>> +      if (startswith (buffer, "la_activity: "))
>> +	{
>> +	  uintptr_t cookie;
>> +	  int this_act;
>> +	  int r = sscanf (buffer + strlen ("la_activity: "),
>> +			  "%d %"SCNxPTR"", &this_act, &cookie);
>> +	  TEST_COMPARE (r, 2);
> 
> I wonder if you can fold the startswith check into the sscanf.  At least
> you could put "la_activity: " into the format string.

Ack, I have changed to la_objopen and la_objclose as well.
diff mbox series

Patch

diff --git a/elf/Makefile b/elf/Makefile
index c6c4710e16..d9cf72ae82 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -375,6 +375,7 @@  tests += \
   tst-audit19b \
   tst-audit20 \
   tst-audit22 \
+  tst-audit23 \
   tst-auditmany \
   tst-auxobj \
   tst-auxobj-dlopen \
@@ -658,6 +659,7 @@  modules-names = \
   tst-audit13mod1 \
   tst-audit18mod \
   tst-audit19bmod \
+  tst-audit23mod \
   tst-auditlogmod-1 \
   tst-auditlogmod-2 \
   tst-auditlogmod-3 \
@@ -680,6 +682,7 @@  modules-names = \
   tst-auditmod19b \
   tst-auditmod20 \
   tst-auditmod22 \
+  tst-auditmod23 \
   tst-auxvalmod \
   tst-big-note-lib \
   tst-deep1mod1 \
@@ -2113,6 +2116,10 @@  tst-audit20-ENV = LD_AUDIT=$(objpfx)tst-auditmod20.so
 $(objpfx)tst-audit22.out: $(objpfx)tst-auditmod22.so
 tst-audit22-ARGS = -- $(host-test-program-cmd)
 
+$(objpfx)tst-audit23.out: $(objpfx)tst-auditmod23.so \
+			  $(objpfx)tst-audit23mod.so
+tst-audit23-ARGS = -- $(host-test-program-cmd)
+
 # 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-fini.c b/elf/dl-fini.c
index de8eb1b3c9..2705a15c88 100644
--- a/elf/dl-fini.c
+++ b/elf/dl-fini.c
@@ -64,6 +64,11 @@  _dl_fini (void)
 	__rtld_lock_unlock_recursive (GL(dl_load_lock));
       else
 	{
+#ifdef SHARED
+	  /* Auditing checkpoint: we will start deleting objects.  */
+	  _dl_audit_activity_nsid (ns, LA_ACT_DELETE);
+#endif
+
 	  /* Now we can allocate an array to hold all the pointers and
 	     copy the pointers in.  */
 	  struct link_map *maps[nloaded];
@@ -153,6 +158,11 @@  _dl_fini (void)
 	      /* Correct the previous increment.  */
 	      --l->l_direct_opencount;
 	    }
+
+#ifdef SHARED
+	  /* Auditing checkpoint: we will start deleting objects.  */
+	  _dl_audit_activity_nsid (ns, LA_ACT_CONSISTENT);
+#endif
 	}
     }
 
diff --git a/elf/tst-audit23.c b/elf/tst-audit23.c
new file mode 100644
index 0000000000..9a7e69c1e1
--- /dev/null
+++ b/elf/tst-audit23.c
@@ -0,0 +1,239 @@ 
+/* Check DT_AUDIT la_objopen and la_objclose for all objects.
+   Copyright (C) 2022 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 <errno.h>
+#include <getopt.h>
+#include <link.h>
+#include <limits.h>
+#include <inttypes.h>
+#include <gnu/lib-names.h>
+#include <string.h>
+#include <stdlib.h>
+#include <support/capture_subprocess.h>
+#include <support/check.h>
+#include <support/xstdio.h>
+#include <support/xdlfcn.h>
+#include <support/support.h>
+
+static int restart;
+#define CMDLINE_OPTIONS \
+  { "restart", no_argument, &restart, 1 },
+
+static int
+handle_restart (void)
+{
+  xdlopen ("tst-audit23mod.so", RTLD_NOW);
+  xdlmopen (LM_ID_NEWLM, LIBC_SO, RTLD_NOW);
+
+  return 0;
+}
+
+static inline bool
+startswith (const char *str, const char *pre)
+{
+  size_t lenpre = strlen (pre);
+  size_t lenstr = strlen (str);
+  return lenstr >= lenpre && memcmp (pre, str, lenpre) == 0;
+}
+
+static inline bool
+is_vdso (const char *str)
+{
+  return startswith (str, "linux-gate")
+	 || startswith (str, "linux-vdso");
+}
+
+static int
+do_test (int argc, char *argv[])
+{
+  /* We must have either:
+     - One our fource parameters left if called initially:
+       + path to ld.so         optional
+       + "--library-path"      optional
+       + the library path      optional
+       + the application name  */
+  if (restart)
+    return handle_restart ();
+
+  char *spargv[9];
+  int i = 0;
+  for (; i < argc - 1; i++)
+    spargv[i] = argv[i + 1];
+  spargv[i++] = (char *) "--direct";
+  spargv[i++] = (char *) "--restart";
+  spargv[i] = NULL;
+
+  setenv ("LD_AUDIT", "tst-auditmod23.so", 0);
+  struct support_capture_subprocess result
+    = support_capture_subprogram (spargv[0], spargv);
+  support_capture_subprocess_check (&result, "tst-audit22", 0, sc_allow_stderr);
+
+  /* The expected la_objopen/la_objclose:
+     1. executable
+     2. loader
+     3. libc.so
+     4. tst-audit23mod.so
+     5. libc.so (LM_ID_NEWLM).
+     6. vdso (optional and ignored).  */
+  enum { max_objs = 6 };
+  struct la_obj_t
+  {
+    char *lname;
+    uintptr_t laddr;
+    Lmid_t lmid;
+    bool closed;
+  } objs[max_objs] = { [0 ... max_objs-1] = { .closed = false } };
+  size_t nobjs = 0;
+
+  /* The expected namespaces are one for the audit module, one for the
+     application, and another for the dlmopen on handle_restart.  */
+  enum { max_ns = 3 };
+  uintptr_t acts[max_ns];
+  size_t nacts = 0;
+  int last_act = -1;
+  uintptr_t last_act_cookie = -1;
+  bool seen_first_objclose = false;
+
+  FILE *out = fmemopen (result.err.buffer, result.err.length, "r");
+  TEST_VERIFY (out != NULL);
+  char *buffer = NULL;
+  size_t buffer_length = 0;
+  while (xgetline (&buffer, &buffer_length, out))
+    {
+      if (startswith (buffer, "la_activity: "))
+	{
+	  uintptr_t cookie;
+	  int this_act;
+	  int r = sscanf (buffer + strlen ("la_activity: "),
+			  "%d %"SCNxPTR"", &this_act, &cookie);
+	  TEST_COMPARE (r, 2);
+
+	  /* The cookie identifies the object at the head of the link map,
+	     so we only add a new namespace if it changes from previous
+	     one.  This work since dlmopen is the last in the test body.  */
+	  if (cookie != last_act_cookie && last_act_cookie != -1)
+	    TEST_COMPARE (last_act, LA_ACT_CONSISTENT);
+
+	  if (this_act == LA_ACT_ADD && acts[nacts - 1] != cookie)
+	    {
+	      acts[nacts++] = cookie;
+	      last_act_cookie = cookie;
+	    }
+	  /* The LA_ACT_DELETE is called in the reverse order of LA_ACT_ADD
+	     at program termination (if the tests adds a dlclose or a library
+	     with extra dependencies this require to be adapted).  */
+	  else if (this_act == LA_ACT_DELETE)
+	    {
+	      last_act_cookie = acts[--nacts];
+	      TEST_COMPARE (acts[nacts], cookie);
+	      acts[nacts] = 0;
+	    }
+	  else if (this_act == LA_ACT_CONSISTENT)
+	    {
+	      TEST_COMPARE (cookie, last_act_cookie);
+
+	      /* LA_ACT_DELETE must always be followed by an la_objclose.  */
+	      if (last_act == LA_ACT_DELETE)
+		TEST_COMPARE (seen_first_objclose, true);
+	      else
+		TEST_COMPARE (last_act, LA_ACT_ADD);
+	    }
+
+	  last_act = this_act;
+	  seen_first_objclose = false;
+	}
+      else if (startswith (buffer, "la_objopen: "))
+	{
+	  char *lname;
+	  uintptr_t laddr;
+	  Lmid_t lmid;
+	  uintptr_t cookie;
+	  int r = sscanf (buffer + strlen ("la_objopen: "),
+			  "%"SCNxPTR"  %ms %"SCNxPTR" %ld", &cookie, &lname,
+			  &laddr, &lmid);
+	  TEST_COMPARE (r, 4);
+
+	  /* la_objclose is not triggered by vDSO because glibc does not
+	     unload it.  */
+	  if (is_vdso (lname))
+	    continue;
+	  if (nobjs == max_objs)
+	    FAIL_EXIT1 ("non expected la_objopen: %s %"PRIxPTR" %ld",
+			lname, laddr, lmid);
+	  objs[nobjs].lname = lname;
+	  objs[nobjs].laddr = laddr;
+	  objs[nobjs].lmid = lmid;
+	  objs[nobjs].closed = false;
+	  nobjs++;
+
+	  /* This indirectly checks that la_objopen always come before
+	     la_objclose btween la_activity calls.  */
+	  seen_first_objclose = false;
+	}
+      else if (startswith (buffer, "la_objclose: "))
+	{
+	  char *lname;
+	  uintptr_t laddr;
+	  Lmid_t lmid;
+	  uintptr_t cookie;
+	  int r = sscanf (buffer + strlen ("la_objclose: "),
+			  "%"SCNxPTR" %ms %"SCNxPTR" %ld", &cookie, &lname,
+			  &laddr, &lmid);
+	  TEST_COMPARE (r, 4);
+
+	  for (size_t i = 0; i < nobjs; i++)
+	    {
+	      if (strcmp (lname, objs[i].lname) == 0 && lmid == objs[i].lmid)
+		{
+		  TEST_COMPARE (objs[i].closed, false);
+		  objs[i].closed = true;
+		  break;
+		}
+	    }
+
+	  /* la_objclose should be called after la_activity(LA_ACT_DELETE) for
+	     the closed object's namespace.  */
+	  TEST_COMPARE (last_act, LA_ACT_DELETE);
+	  if (!seen_first_objclose)
+	    {
+	      TEST_COMPARE (last_act_cookie, cookie);
+	      seen_first_objclose = true;
+	    }
+	}
+    }
+
+  for (size_t i = 0; i < nobjs; i++)
+    {
+      TEST_COMPARE (objs[i].closed, true);
+      free (objs[i].lname);
+    }
+
+  /* la_activity(LA_ACT_CONSISTENT) should be the last callback received.
+     Since only one link map may be not-CONSISTENT at a time, this also
+     ensures la_activity(LA_ACT_CONSISTENT) is the last callback received
+     for every namespace.  */
+  TEST_COMPARE (last_act, LA_ACT_CONSISTENT);
+
+  free (buffer);
+  xfclose (out);
+
+  return 0;
+}
+
+#define TEST_FUNCTION_ARGV do_test
+#include <support/test-driver.c>
diff --git a/elf/tst-audit23mod.c b/elf/tst-audit23mod.c
new file mode 100644
index 0000000000..9a116ff682
--- /dev/null
+++ b/elf/tst-audit23mod.c
@@ -0,0 +1,23 @@ 
+/* Extra modules for tst-audit23
+   Copyright (C) 2022 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-auditmod23.c b/elf/tst-auditmod23.c
new file mode 100644
index 0000000000..42eccae11b
--- /dev/null
+++ b/elf/tst-auditmod23.c
@@ -0,0 +1,74 @@ 
+/* Audit modules loaded by tst-audit23.
+   Copyright (C) 2022 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 <inttypes.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/auxv.h>
+
+unsigned int
+la_version (unsigned int version)
+{
+  return LAV_CURRENT;
+}
+
+struct map_desc_t
+{
+  char *lname;
+  uintptr_t laddr;
+  Lmid_t lmid;
+};
+
+void
+la_activity (uintptr_t *cookie, unsigned int flag)
+{
+  fprintf (stderr, "%s: %d %"PRIxPTR"\n", __func__, flag, (uintptr_t) cookie);
+}
+
+unsigned int
+la_objopen (struct link_map *map, Lmid_t lmid, uintptr_t *cookie)
+{
+  const char *l_name = map->l_name[0] == '\0' ? "mainapp" : map->l_name;
+  fprintf (stderr, "%s: %"PRIxPTR" %s %"PRIxPTR" %ld\n", __func__,
+	   (uintptr_t) cookie, l_name, map->l_addr, lmid);
+
+  struct map_desc_t *map_desc = malloc (sizeof (struct map_desc_t));
+  if (map_desc == NULL)
+    abort ();
+
+  map_desc->lname = strdup (l_name);
+  map_desc->laddr = map->l_addr;
+  map_desc->lmid = lmid;
+
+  *cookie = (uintptr_t) map_desc;
+
+  return 0;
+}
+
+unsigned int
+la_objclose (uintptr_t *cookie)
+{
+  struct map_desc_t *map_desc = (struct map_desc_t *) *cookie;
+  fprintf (stderr, "%s: %"PRIxPTR" %s %"PRIxPTR" %ld\n", __func__,
+	   (uintptr_t) cookie, map_desc->lname, map_desc->laddr,
+	   map_desc->lmid);
+
+  return 0;
+}