Re: [PATCH v2 02/14] elf: Add a DTV setup test [BZ #27136]

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

On 13/04/2021 05:18, Szabolcs Nagy via Libc-alpha wrote:
> The test dlopens a large number of modules with TLS, they are reused
> from an existing test.
> 
> The test relies on the reuse of slotinfo entries after dlclose, without
> bug 27135 fixed this needs a failing dlopen. With a slotinfo list that
> has non-monotone increasing generation counters, bug 27136 can trigger.
> 
> --
> v2:
> - moved from nptl/ to elf/
> - dlopen a different set of existing modules.
> - code style fixes (!= NULL etc).
> - moved after bug fix patch

LGTM, with just a small suggestion below?

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  elf/Makefile           | 10 ++++-
>  elf/tst-tls20.c        | 98 ++++++++++++++++++++++++++++++++++++++++++
>  elf/tst-tls20mod-bad.c |  2 +
>  3 files changed, 109 insertions(+), 1 deletion(-)
>  create mode 100644 elf/tst-tls20.c
>  create mode 100644 elf/tst-tls20mod-bad.c
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index 0bef49e53d..b1344f1133 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -222,7 +222,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
>  	 tst-audit14 tst-audit15 tst-audit16 \
>  	 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
> +	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
> +	 tst-tls20
>  #	 reldep9
>  tests-internal += loadtest unload unload2 circleload1 \
>  	 neededtest neededtest2 neededtest3 neededtest4 \

Ok.

> @@ -344,6 +345,7 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
>  		libmarkermod2-1 libmarkermod2-2 \
>  		libmarkermod3-1 libmarkermod3-2 libmarkermod3-3 \
>  		libmarkermod4-1 libmarkermod4-2 libmarkermod4-3 libmarkermod4-4 \
> +		tst-tls20mod-bad
>  
>  # Most modules build with _ISOMAC defined, but those filtered out
>  # depend on internal headers.

Ok.

> @@ -1924,3 +1926,9 @@ $(objpfx)tst-rtld-help.out: $(objpfx)ld.so
>  	fi; \
>  	(exit $$status); \
>  	$(evaluate-test)
> +
> +# Reuses tst-tls-many-dynamic-modules
> +tst-tls20mod-bad.so-no-z-defs = yes
> +$(objpfx)tst-tls20: $(libdl) $(shared-thread-library)
> +$(objpfx)tst-tls20.out: $(objpfx)tst-tls20mod-bad.so \
> +			$(tst-tls-many-dynamic-modules:%=$(objpfx)%.so)
> diff --git a/elf/tst-tls20.c b/elf/tst-tls20.c

Ok.

> new file mode 100644
> index 0000000000..a378c1fa08
> --- /dev/null
> +++ b/elf/tst-tls20.c
> @@ -0,0 +1,98 @@
> +/* Test dtv setup if entries don't have monotone increasing generation.
> +   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-tls20mod-bad.so", RTLD_NOW);
> +  if (m != NULL)
> +    FAIL_EXIT1 ("dlopen of tst-tls20mod-bad.so succeeded\n");
> +}
> +
> +static void
> +load_mod (int i)
> +{
> +  char buf[100];
> +  snprintf (buf, sizeof buf, "tst-tls-manydynamic%02dmod.so", i);
> +  mod[i] = xdlopen (buf, RTLD_LAZY);
> +}

Maybe xasprintf here?  

> +
> +static void
> +unload_mod (int i)
> +{
> +  if (mod[i] != NULL)
> +    xdlclose (mod[i]);
> +  mod[i] = NULL;
> +}
> +
> +static void
> +access (int i)
> +{
> +  char buf[100];
> +  snprintf (buf, sizeof buf, "tls_global_%02d", i);

Same as before.

> +  dlerror ();
> +  int *p = dlsym (mod[i], buf);
> +  printf ("mod[%d]: &tls = %p\n", i, p);
> +  if (p == NULL)
> +    FAIL_EXIT1 ("dlsym failed: %s\n", dlerror ());
> +  ++*p;
> +}
> +
> +static void *
> +start (void *a)
> +{
> +  for (int i = 0; i < NMOD; i++)
> +    if (mod[i] != NULL)
> +      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/elf/tst-tls20mod-bad.c b/elf/tst-tls20mod-bad.c
> new file mode 100644
> index 0000000000..c1aed8ea7d
> --- /dev/null
> +++ b/elf/tst-tls20mod-bad.c
> @@ -0,0 +1,2 @@
> +void missing_symbol (void);
> +void f (void) {missing_symbol ();}
> 

Ok.