Re: [PATCH 04/15] Add a DTV setup test [BZ #27136]

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 15/02/2021 08:59, Szabolcs Nagy via Libc-alpha wrote:
> The test relies on reusing slotinfo entries after dlclose which
> can result in non-monotonic increasing generation counters in
> the slotinfo list. It can trigger bug 27136.
> 
> The test requires large number of modules with TLS so the
> modules of tst-tls7 are used instead of duplicating them.

This patch need to be moved after the one that actually fixes
BZ #27136.

I am getting consistently the error:

| mod[57]: &x = 0x7f1a340013f0
| mod[58]: &x = 0x7f1a340012b0
| mod[59]: &x = 0x7f1a340011f0
| mod[60]: &x = 0x7f1a340010b0
| mod[61]: &x = 0x7f1a340010f0
| mod[62]: &x = (nil)
| error: tst-tls8.c:62: dlsym failed: (null)
 
On multiple platforms (x86_64, arm, aarch64, and powerpc64le) and I 
think this is the expected result on a platform without BZ#27136 
fixed.

Patch looks ok in general, some comments below.

> ---
>  nptl/Makefile          | 10 ++++-
>  nptl/tst-tls8.c        | 96 ++++++++++++++++++++++++++++++++++++++++++
>  nptl/tst-tls8mod-bad.c |  2 +
>  3 files changed, 106 insertions(+), 2 deletions(-)
>  create mode 100644 nptl/tst-tls8.c
>  create mode 100644 nptl/tst-tls8mod-bad.c
> 
> diff --git a/nptl/Makefile b/nptl/Makefile
> index 208629876d..a11b598efd 100644
> --- a/nptl/Makefile
> +++ b/nptl/Makefile
> @@ -354,7 +354,7 @@ LDFLAGS-pthread.so = -Wl,--enable-new-dtags,-z,nodelete,-z,initfirst
>  tests += tst-cancelx7 tst-cancelx17 tst-cleanupx4
>  
>  ifeq ($(build-shared),yes)
> -tests += tst-compat-forwarder tst-audit-threads
> +tests += tst-compat-forwarder tst-audit-threads tst-tls8
>  tests-internal += tst-tls3 tst-tls3-malloc tst-tls5 tst-stackguard1 tst-tls7
>  ifeq ($(have-z-execstack),yes)
>  tests += tst-execstack

Ok.

> @@ -371,7 +371,7 @@ modules-names = tst-tls3mod \
>  		tst-execstack-mod \
>  		tst-compat-forwarder-mod tst-audit-threads-mod1 \
>  		tst-audit-threads-mod2 \
> -		tst-tls7mod tst-tls7mod-dep
> +		tst-tls7mod tst-tls7mod-dep tst-tls8mod-bad
>  extra-test-objs += $(addsuffix .os,$(strip $(modules-names))) \
>  		   tst-cleanup4aux.o tst-cleanupx4aux.o $(tst-tls7mod-deps)
>  test-extras += tst-cleanup4aux tst-cleanupx4aux

Ok.

> @@ -528,6 +528,12 @@ $(objpfx)tst-tls7mod.so: $(tst-tls7mod-deps:%=$(objpfx)%)
>  $(tst-tls7mod-deps:%=$(objpfx)%): $(objpfx)tst-tls7mod-dep.so
>  	cp -f $< $@
>  
> +# Reuse tst-tls7mod-dep*.so.
> +tst-tls8mod-bad.so-no-z-defs = yes
> +$(objpfx)tst-tls8: $(libdl) $(shared-thread-library)
> +$(objpfx)tst-tls8.out: $(objpfx)tst-tls8mod-bad.so \
> +		       $(tst-tls7mod-deps:%=$(objpfx)%)
> +
>  $(objpfx)tst-dlsym1: $(libdl) $(shared-thread-library)
>  
>  ifeq (yes,$(build-shared))
> diff --git a/nptl/tst-tls8.c b/nptl/tst-tls8.c
> new file mode 100644
> index 0000000000..be7b64c9be
> --- /dev/null
> +++ b/nptl/tst-tls8.c
> @@ -0,0 +1,96 @@
> +/* Test dtv setup if entries don't have monoton increasing generation.

s/monoton/monotonic

> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <dlfcn.h>
> +#include <pthread.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <support/check.h>
> +#include <support/xdlfcn.h>
> +#include <support/xthread.h>
> +
> +#define NMOD 100
> +static void *mod[NMOD];
> +
> +static void
> +load_fail (void)
> +{
> +  /* Expected to fail because of a missing symbol.  */
> +  void *m = dlopen ("tst-tls8mod-bad.so", RTLD_NOW);
> +  if (m != NULL)
> +    FAIL_EXIT1 ("dlopen of tst-tls8mod-bad.so succeeded\n");
> +}

Ok.

> +
> +static void
> +load_mod (int i)
> +{
> +  char buf[100];
> +  sprintf (buf, "tst-tls7mod-dep-%02d.so", i);

Maybe use snprintf or xasprintf here?

> +  mod[i] = xdlopen (buf, RTLD_LAZY);
> +}
> +
> +static void
> +unload_mod (int i)
> +{
> +  if (mod[i])

No implicit check.

> +    xdlclose (mod[i]);
> +  mod[i] = 0;

Use NULL here.

> +}
> +
> +static void
> +access (int i)
> +{
> +  dlerror ();
> +  int *p = dlsym (mod[i], "x");
> +  printf ("mod[%d]: &x = %p\n", i, p);
> +  if (p == NULL)
> +    FAIL_EXIT1 ("dlsym failed: %s\n", dlerror ());
> +  ++*p;
> +}
> +

Ok.

> +static void *
> +start (void *a)
> +{
> +  for (int i = 0; i < NMOD; i++)
> +    if (mod[i])

No implicit check.

> +      access (i);
> +  return 0;
> +}
> +
> +static int
> +do_test (void)
> +{
> +  int i;
> +
> +  for (i = 0; i < NMOD; i++)
> +    {
> +      load_mod (i);
> +      /* Bump the generation of mod[0] without using new dtv slot.  */
> +      unload_mod (0);
> +      load_fail (); /* Ensure GL(dl_tls_dtv_gaps) is true: see bug 27135.  */
> +      load_mod (0);
> +      /* Access TLS in all loaded modules.  */
> +      pthread_t t = xpthread_create (0, start, 0);
> +      xpthread_join (t);
> +    }
> +  for (i = 0; i < NMOD; i++)
> +    unload_mod (i);
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
Ok.

> diff --git a/nptl/tst-tls8mod-bad.c b/nptl/tst-tls8mod-bad.c
> new file mode 100644
> index 0000000000..c1aed8ea7d
> --- /dev/null
> +++ b/nptl/tst-tls8mod-bad.c
> @@ -0,0 +1,2 @@
> +void missing_symbol (void);
> +void f (void) {missing_symbol ();}

Use the usual format:

 void f (void)
 {
   missing_symbol ();
 }