[v2] rtld: Add glibc.rtld.enable_secure tunable.

  Add a tunable for setting __libc_enable_secure to 1.  Does not set
__libc_enable_secure to 0 if the tunable is set to 0.  Ignores any
tunables following glib.rtld.enable_secure.  One use-case for this
addition is to enable testing code paths that depend on
__libc_eanble_secure being set without the need to use setxid binaries.
---
Changes to v1:
  * handle the tunable for the dynamic loader as well.
  
NOTE: I'm not certain I've picked the appropriate place to handle
glibc.rtld.enable_secure.  I tried to make it happen as early as
possible to minimize and places where __libc_enable_secure might be
checked before the tunable initialization takes place.

 NEWS                                |   4 +
 csu/libc-start.c                    |   4 +
 elf/Makefile                        |   2 +
 elf/dl-tunables.c                   |   8 +-
 elf/dl-tunables.h                   |  11 +++
 elf/dl-tunables.list                |   6 ++
 elf/tst-rtld-list-tunables.exp      |   1 +
 elf/tst-tunables-enable_secure.c    | 115 ++++++++++++++++++++++++++++
 sysdeps/unix/sysv/linux/dl-sysdep.c |   3 +
 9 files changed, 153 insertions(+), 1 deletion(-)
 create mode 100644 elf/tst-tunables-enable_secure.c
  

On 2023-12-05 12:45, Joe Simmons-Talbott wrote:
> Add a tunable for setting __libc_enable_secure to 1.  Does not set
> __libc_enable_secure to 0 if the tunable is set to 0.  Ignores any
> tunables following glib.rtld.enable_secure.  One use-case for this
> addition is to enable testing code paths that depend on
> __libc_eanble_secure being set without the need to use setxid binaries.
> ---
> Changes to v1:
>    * handle the tunable for the dynamic loader as well.
>    
> NOTE: I'm not certain I've picked the appropriate place to handle
> glibc.rtld.enable_secure.  I tried to make it happen as early as
> possible to minimize and places where __libc_enable_secure might be
> checked before the tunable initialization takes place.
> 
>   NEWS                                |   4 +
>   csu/libc-start.c                    |   4 +
>   elf/Makefile                        |   2 +
>   elf/dl-tunables.c                   |   8 +-
>   elf/dl-tunables.h                   |  11 +++
>   elf/dl-tunables.list                |   6 ++
>   elf/tst-rtld-list-tunables.exp      |   1 +
>   elf/tst-tunables-enable_secure.c    | 115 ++++++++++++++++++++++++++++
>   sysdeps/unix/sysv/linux/dl-sysdep.c |   3 +
>   9 files changed, 153 insertions(+), 1 deletion(-)
>   create mode 100644 elf/tst-tunables-enable_secure.c
> 
> diff --git a/NEWS b/NEWS
> index 8c1c149f91..b04fb15064 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -43,6 +43,10 @@ Major new features:
>     on thread stack created by pthread_create or memory allocated by
>     malloc).
>   
> +* A new tunable, glibc.rtld.enable_secure, used to set __libc_enable_secure
> +  to 1.  Setting the tunable to 0 does *NOT* set __libc_enable_secure to 0.
> +  Once the tunable is encountered all following tunables are ignored.
> +

__libc_enable_secure is an internal detail.  How about rephrasing it in 
terms of the feature this implements, i.e. "A new tunable, ... used to 
run a program as if it were a setuid process, enabling a number of 
security features. This is currently a testing tool to allow more 
extensive verification tests for AT_SECURE programs and not meant to be 
a security feature".

>   Deprecated and removed features, and other changes affecting compatibility:
>   
>   * The ldconfig program now skips file names containing ';' or ending in
> diff --git a/csu/libc-start.c b/csu/libc-start.c
> index c3bb6d09bc..2f546a3677 100644
> --- a/csu/libc-start.c
> +++ b/csu/libc-start.c
> @@ -266,6 +266,10 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
>   
>     __tunables_init (__environ);
>   
> +  int32_t tes = TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t, NULL);
> +  if (tes == 1)
> +    __libc_enable_secure = 1;
> +

OK, but I wonder if it's easier to just do this in __tunables_init so 
that it's done in a single place.

>     ARCH_INIT_CPU_FEATURES ();
>   
>     /* Do static pie self relocation after tunables and cpu features
> diff --git a/elf/Makefile b/elf/Makefile
> index afec7be084..6c38a72b0d 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -285,6 +285,7 @@ tests-static-internal := \
>     tst-tls1-static \
>     tst-tls1-static-non-pie \
>     tst-tunables \
> +  tst-tunables-enable_secure \
>     # tests-static-internal
>   
>   CRT-tst-tls1-static-non-pie := $(csu-objpfx)crt1.o
> @@ -2672,6 +2673,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
>   $(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
>   
>   tst-tunables-ARGS = -- $(host-test-program-cmd)
> +tst-tunables-enable_secure-ARGS = -- $(host-test-program-cmd)
>   
>   $(objpfx)list-tunables.out: tst-rtld-list-tunables.sh $(objpfx)ld.so
>   	$(SHELL) $< $(objpfx)ld.so '$(test-wrapper-env)' \
> diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> index 644d21d1b0..d6c55cfaf2 100644
> --- a/elf/dl-tunables.c
> +++ b/elf/dl-tunables.c
> @@ -250,7 +250,13 @@ parse_tunables (char *valstring)
>       }
>   
>     for (int i = 0; i < ntunables; i++)
> -    tunable_initialize (tunables[i].t, tunables[i].value);
> +    {
> +      tunable_initialize (tunables[i].t, tunables[i].value);
> +
> +      /* Ignore all tunables after encountering "glibc.rtld.enable_secure" */
> +      if (tunable_strcmp(tunables[i].t->name, "glibc.rtld.enable_secure") == 0)
> +	break;

This still has the problem that Szabolcs pointed out, i.e. one only 
needs to reorder tunables to be before enable_secure to avoid being 
ignored.  What you need to do is when you encounter enable_secure in 
parse_tunable_string (look for the tunable_is_name call in there), you 
return 0.  That will ensure that no tunables are set at all and you've 
successfully emulated setxid for tunables.  If you set 
__libc_enable_secure there, all code that follows will run as if the 
program were AT_SECURE.

> +    }
>   }
>   
>   /* Initialize the tunables list from the environment.  For now we only use the
> diff --git a/elf/dl-tunables.h b/elf/dl-tunables.h
> index 0df4dde24e..2d4fc84d74 100644
> --- a/elf/dl-tunables.h
> +++ b/elf/dl-tunables.h
> @@ -164,4 +164,15 @@ tunable_is_name (const char *orig, const char *envname)
>       return false;
>   }
>   
> +/* Compare two strings. */
> +static __always_inline int
> +tunable_strcmp (const char *left, const char *right)
> +{
> +  for (;*left != '\0' && *right != '\0'; right++, left++)
> +    if (*left != *right)
> +      break;
> +
> +  return *left - *right;
> +}
> +
>   #endif
> diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
> index 1b23fc9473..cb1b35854e 100644
> --- a/elf/dl-tunables.list
> +++ b/elf/dl-tunables.list
> @@ -136,6 +136,12 @@ glibc {
>         minval: 0
>         default: 512
>       }
> +    enable_secure {
> +      type: INT_32
> +      minval: 0
> +      maxval: 1
> +      default: 0
> +    }
>     }
>   
>     mem {
> diff --git a/elf/tst-rtld-list-tunables.exp b/elf/tst-rtld-list-tunables.exp
> index 2233ea9c7c..db0e1c86e9 100644
> --- a/elf/tst-rtld-list-tunables.exp
> +++ b/elf/tst-rtld-list-tunables.exp
> @@ -12,5 +12,6 @@ glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0x[f]+)
>   glibc.malloc.top_pad: 0x20000 (min: 0x0, max: 0x[f]+)
>   glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0x[f]+)
>   glibc.rtld.dynamic_sort: 2 (min: 1, max: 2)
> +glibc.rtld.enable_secure: 0 (min: 0, max: 1)
>   glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
>   glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0x[f]+)
> diff --git a/elf/tst-tunables-enable_secure.c b/elf/tst-tunables-enable_secure.c
> new file mode 100644
> index 0000000000..e749ec9f17
> --- /dev/null
> +++ b/elf/tst-tunables-enable_secure.c
> @@ -0,0 +1,115 @@
> +/* Check GLIBC_TUNABLES parsing for enable_secure.
> +   Copyright (C) 2023 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 <array_length.h>
> +#include <dl-tunables.h>
> +#include <getopt.h>
> +#include <intprops.h>
> +#include <stdint.h>
> +#include <stdlib.h>
> +#include <support/capture_subprocess.h>
> +#include <support/check.h>
> +#include <sys/auxv.h>
> +#include <unistd.h>
> +
> +static int restart;
> +#define CMDLINE_OPTIONS \
> +  { "restart", no_argument, &restart, 1 },
> +
> +static const struct test_t
> +{
> +  const char *env;
> +  int32_t expected_malloc_check;
> +  int32_t expected_enable_secure;
> +} tests[] =
> +{
> +  /* Expected tunable format.  */
> +  {
> +    "glibc.malloc.check=2:glibc.rtld.enable_secure=1",
> +    2,
> +    1,
> +  },
> +  /* Tunables encountered after enable_secure should be ignored. */
> +  {
> +    "glibc.rtld.enable_secure=1:glibc.malloc.check=2",
> +    0,
> +    1,
> +  },
> +};
> +
> +static int
> +handle_restart (int i)
> +{
> +  TEST_COMPARE (tests[i].expected_malloc_check,
> +		TUNABLE_GET_FULL (glibc, malloc, check, int32_t, NULL));
> +  TEST_COMPARE (tests[i].expected_enable_secure,
> +		TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t, NULL));
> +  if (tests[i].expected_enable_secure == 1)
> +    {
> +      TEST_COMPARE (1, __libc_enable_secure);
> +    }
> +  return 0;
> +}
> +
> +static int
> +do_test (int argc, char *argv[])
> +{
> +  /* We must have either:
> +     - One or four parameters left if called initially:
> +       + path to ld.so         optional
> +       + "--library-path"      optional
> +       + the library path      optional
> +       + the application name
> +       + the test to check  */
> +
> +  TEST_VERIFY_EXIT (argc == 2 || argc == 5);
> +
> +  if (restart)
> +    return handle_restart (atoi (argv[1]));
> +
> +  char nteststr[INT_BUFSIZE_BOUND (int)];
> +
> +  char *spargv[10];
> +  {
> +    int i = 0;
> +    for (; i < argc - 1; i++)
> +      spargv[i] = argv[i + 1];
> +    spargv[i++] = (char *) "--direct";
> +    spargv[i++] = (char *) "--restart";
> +    spargv[i++] = nteststr;
> +    spargv[i] = NULL;
> +  }
> +
> +  for (int i = 0; i < array_length (tests); i++)
> +    {
> +      snprintf (nteststr, sizeof nteststr, "%d", i);
> +
> +      printf ("[%d] Spawned test for %s\n", i, tests[i].env);
> +      setenv ("GLIBC_TUNABLES", tests[i].env, 1);
> +      struct support_capture_subprocess result
> +	= support_capture_subprogram (spargv[0], spargv);
> +      support_capture_subprocess_check (&result, "tst-tunables-enable_secure",
> +		                        0, sc_allow_stderr);
> +      support_capture_subprocess_free (&result);
> +    }
> +
> +  return 0;
> +}
> +
> +#define TEST_FUNCTION_ARGV do_test
> +#include <support/test-driver.c>
> diff --git a/sysdeps/unix/sysv/linux/dl-sysdep.c b/sysdeps/unix/sysv/linux/dl-sysdep.c
> index 1b3dd869b5..d3a30e8d7a 100644
> --- a/sysdeps/unix/sysv/linux/dl-sysdep.c
> +++ b/sysdeps/unix/sysv/linux/dl-sysdep.c
> @@ -108,6 +108,9 @@ _dl_sysdep_start (void **start_argptr,
>     dl_hwcap_check ();
>   
>     __tunables_init (_environ);
> +  int32_t tes = TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t, NULL);
> +  if (tes == 1)
> +    __libc_enable_secure = 1;

OK, but maybe better to just do it in __tunables_init.  Any specific 
reason why you're doing it here?  For example, you've missed the hurd 
dl-sysdep change.

>   
>     /* Initialize DSO sorting algorithm after tunables.  */
>     _dl_sort_maps_init ();

Thanks,
Sid
  

On Tue, Dec 12, 2023 at 02:48:53PM -0500, Siddhesh Poyarekar wrote:
> On 2023-12-05 12:45, Joe Simmons-Talbott wrote:
> > Add a tunable for setting __libc_enable_secure to 1.  Does not set
> > __libc_enable_secure to 0 if the tunable is set to 0.  Ignores any
> > tunables following glib.rtld.enable_secure.  One use-case for this
> > addition is to enable testing code paths that depend on
> > __libc_eanble_secure being set without the need to use setxid binaries.
> > ---
> > Changes to v1:
> >    * handle the tunable for the dynamic loader as well.
> > NOTE: I'm not certain I've picked the appropriate place to handle
> > glibc.rtld.enable_secure.  I tried to make it happen as early as
> > possible to minimize and places where __libc_enable_secure might be
> > checked before the tunable initialization takes place.
> > 
> >   NEWS                                |   4 +
> >   csu/libc-start.c                    |   4 +
> >   elf/Makefile                        |   2 +
> >   elf/dl-tunables.c                   |   8 +-
> >   elf/dl-tunables.h                   |  11 +++
> >   elf/dl-tunables.list                |   6 ++
> >   elf/tst-rtld-list-tunables.exp      |   1 +
> >   elf/tst-tunables-enable_secure.c    | 115 ++++++++++++++++++++++++++++
> >   sysdeps/unix/sysv/linux/dl-sysdep.c |   3 +
> >   9 files changed, 153 insertions(+), 1 deletion(-)
> >   create mode 100644 elf/tst-tunables-enable_secure.c
> > 
> > diff --git a/NEWS b/NEWS
> > index 8c1c149f91..b04fb15064 100644
> > --- a/NEWS
> > +++ b/NEWS
> > @@ -43,6 +43,10 @@ Major new features:
> >     on thread stack created by pthread_create or memory allocated by
> >     malloc).
> > +* A new tunable, glibc.rtld.enable_secure, used to set __libc_enable_secure
> > +  to 1.  Setting the tunable to 0 does *NOT* set __libc_enable_secure to 0.
> > +  Once the tunable is encountered all following tunables are ignored.
> > +
> 
> __libc_enable_secure is an internal detail.  How about rephrasing it in
> terms of the feature this implements, i.e. "A new tunable, ... used to run a
> program as if it were a setuid process, enabling a number of security
> features. This is currently a testing tool to allow more extensive
> verification tests for AT_SECURE programs and not meant to be a security
> feature".

Updated.

> 
> >   Deprecated and removed features, and other changes affecting compatibility:
> >   * The ldconfig program now skips file names containing ';' or ending in
> > diff --git a/csu/libc-start.c b/csu/libc-start.c
> > index c3bb6d09bc..2f546a3677 100644
> > --- a/csu/libc-start.c
> > +++ b/csu/libc-start.c
> > @@ -266,6 +266,10 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
> >     __tunables_init (__environ);
> > +  int32_t tes = TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t, NULL);
> > +  if (tes == 1)
> > +    __libc_enable_secure = 1;
> > +
> 
> OK, but I wonder if it's easier to just do this in __tunables_init so that
> it's done in a single place.

Moved this __tunables_init as you've suggested.

> 
> >     ARCH_INIT_CPU_FEATURES ();
> >     /* Do static pie self relocation after tunables and cpu features
> > diff --git a/elf/Makefile b/elf/Makefile
> > index afec7be084..6c38a72b0d 100644
> > --- a/elf/Makefile
> > +++ b/elf/Makefile
> > @@ -285,6 +285,7 @@ tests-static-internal := \
> >     tst-tls1-static \
> >     tst-tls1-static-non-pie \
> >     tst-tunables \
> > +  tst-tunables-enable_secure \
> >     # tests-static-internal
> >   CRT-tst-tls1-static-non-pie := $(csu-objpfx)crt1.o
> > @@ -2672,6 +2673,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
> >   $(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
> >   tst-tunables-ARGS = -- $(host-test-program-cmd)
> > +tst-tunables-enable_secure-ARGS = -- $(host-test-program-cmd)
> >   $(objpfx)list-tunables.out: tst-rtld-list-tunables.sh $(objpfx)ld.so
> >   	$(SHELL) $< $(objpfx)ld.so '$(test-wrapper-env)' \
> > diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> > index 644d21d1b0..d6c55cfaf2 100644
> > --- a/elf/dl-tunables.c
> > +++ b/elf/dl-tunables.c
> > @@ -250,7 +250,13 @@ parse_tunables (char *valstring)
> >       }
> >     for (int i = 0; i < ntunables; i++)
> > -    tunable_initialize (tunables[i].t, tunables[i].value);
> > +    {
> > +      tunable_initialize (tunables[i].t, tunables[i].value);
> > +
> > +      /* Ignore all tunables after encountering "glibc.rtld.enable_secure" */
> > +      if (tunable_strcmp(tunables[i].t->name, "glibc.rtld.enable_secure") == 0)
> > +	break;
> 
> This still has the problem that Szabolcs pointed out, i.e. one only needs to
> reorder tunables to be before enable_secure to avoid being ignored.  What
> you need to do is when you encounter enable_secure in parse_tunable_string
> (look for the tunable_is_name call in there), you return 0.  That will
> ensure that no tunables are set at all and you've successfully emulated
> setxid for tunables.  If you set __libc_enable_secure there, all code that
> follows will run as if the program were AT_SECURE.
> 

Updated as you suggested and setting enable_secure doesn't set any
tunables.

> > +    }
> >   }
> >   /* Initialize the tunables list from the environment.  For now we only use the
> > diff --git a/elf/dl-tunables.h b/elf/dl-tunables.h
> > index 0df4dde24e..2d4fc84d74 100644
> > --- a/elf/dl-tunables.h
> > +++ b/elf/dl-tunables.h
> > @@ -164,4 +164,15 @@ tunable_is_name (const char *orig, const char *envname)
> >       return false;
> >   }
> > +/* Compare two strings. */
> > +static __always_inline int
> > +tunable_strcmp (const char *left, const char *right)
> > +{
> > +  for (;*left != '\0' && *right != '\0'; right++, left++)
> > +    if (*left != *right)
> > +      break;
> > +
> > +  return *left - *right;
> > +}
> > +
> >   #endif
> > diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
> > index 1b23fc9473..cb1b35854e 100644
> > --- a/elf/dl-tunables.list
> > +++ b/elf/dl-tunables.list
> > @@ -136,6 +136,12 @@ glibc {
> >         minval: 0
> >         default: 512
> >       }
> > +    enable_secure {
> > +      type: INT_32
> > +      minval: 0
> > +      maxval: 1
> > +      default: 0
> > +    }
> >     }
> >     mem {
> > diff --git a/elf/tst-rtld-list-tunables.exp b/elf/tst-rtld-list-tunables.exp
> > index 2233ea9c7c..db0e1c86e9 100644
> > --- a/elf/tst-rtld-list-tunables.exp
> > +++ b/elf/tst-rtld-list-tunables.exp
> > @@ -12,5 +12,6 @@ glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0x[f]+)
> >   glibc.malloc.top_pad: 0x20000 (min: 0x0, max: 0x[f]+)
> >   glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0x[f]+)
> >   glibc.rtld.dynamic_sort: 2 (min: 1, max: 2)
> > +glibc.rtld.enable_secure: 0 (min: 0, max: 1)
> >   glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
> >   glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0x[f]+)
> > diff --git a/elf/tst-tunables-enable_secure.c b/elf/tst-tunables-enable_secure.c
> > new file mode 100644
> > index 0000000000..e749ec9f17
> > --- /dev/null
> > +++ b/elf/tst-tunables-enable_secure.c
> > @@ -0,0 +1,115 @@
> > +/* Check GLIBC_TUNABLES parsing for enable_secure.
> > +   Copyright (C) 2023 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 <array_length.h>
> > +#include <dl-tunables.h>
> > +#include <getopt.h>
> > +#include <intprops.h>
> > +#include <stdint.h>
> > +#include <stdlib.h>
> > +#include <support/capture_subprocess.h>
> > +#include <support/check.h>
> > +#include <sys/auxv.h>
> > +#include <unistd.h>
> > +
> > +static int restart;
> > +#define CMDLINE_OPTIONS \
> > +  { "restart", no_argument, &restart, 1 },
> > +
> > +static const struct test_t
> > +{
> > +  const char *env;
> > +  int32_t expected_malloc_check;
> > +  int32_t expected_enable_secure;
> > +} tests[] =
> > +{
> > +  /* Expected tunable format.  */
> > +  {
> > +    "glibc.malloc.check=2:glibc.rtld.enable_secure=1",
> > +    2,
> > +    1,
> > +  },
> > +  /* Tunables encountered after enable_secure should be ignored. */
> > +  {
> > +    "glibc.rtld.enable_secure=1:glibc.malloc.check=2",
> > +    0,
> > +    1,
> > +  },
> > +};
> > +
> > +static int
> > +handle_restart (int i)
> > +{
> > +  TEST_COMPARE (tests[i].expected_malloc_check,
> > +		TUNABLE_GET_FULL (glibc, malloc, check, int32_t, NULL));
> > +  TEST_COMPARE (tests[i].expected_enable_secure,
> > +		TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t, NULL));
> > +  if (tests[i].expected_enable_secure == 1)
> > +    {
> > +      TEST_COMPARE (1, __libc_enable_secure);
> > +    }
> > +  return 0;
> > +}
> > +
> > +static int
> > +do_test (int argc, char *argv[])
> > +{
> > +  /* We must have either:
> > +     - One or four parameters left if called initially:
> > +       + path to ld.so         optional
> > +       + "--library-path"      optional
> > +       + the library path      optional
> > +       + the application name
> > +       + the test to check  */
> > +
> > +  TEST_VERIFY_EXIT (argc == 2 || argc == 5);
> > +
> > +  if (restart)
> > +    return handle_restart (atoi (argv[1]));
> > +
> > +  char nteststr[INT_BUFSIZE_BOUND (int)];
> > +
> > +  char *spargv[10];
> > +  {
> > +    int i = 0;
> > +    for (; i < argc - 1; i++)
> > +      spargv[i] = argv[i + 1];
> > +    spargv[i++] = (char *) "--direct";
> > +    spargv[i++] = (char *) "--restart";
> > +    spargv[i++] = nteststr;
> > +    spargv[i] = NULL;
> > +  }
> > +
> > +  for (int i = 0; i < array_length (tests); i++)
> > +    {
> > +      snprintf (nteststr, sizeof nteststr, "%d", i);
> > +
> > +      printf ("[%d] Spawned test for %s\n", i, tests[i].env);
> > +      setenv ("GLIBC_TUNABLES", tests[i].env, 1);
> > +      struct support_capture_subprocess result
> > +	= support_capture_subprogram (spargv[0], spargv);
> > +      support_capture_subprocess_check (&result, "tst-tunables-enable_secure",
> > +		                        0, sc_allow_stderr);
> > +      support_capture_subprocess_free (&result);
> > +    }
> > +
> > +  return 0;
> > +}
> > +
> > +#define TEST_FUNCTION_ARGV do_test
> > +#include <support/test-driver.c>
> > diff --git a/sysdeps/unix/sysv/linux/dl-sysdep.c b/sysdeps/unix/sysv/linux/dl-sysdep.c
> > index 1b3dd869b5..d3a30e8d7a 100644
> > --- a/sysdeps/unix/sysv/linux/dl-sysdep.c
> > +++ b/sysdeps/unix/sysv/linux/dl-sysdep.c
> > @@ -108,6 +108,9 @@ _dl_sysdep_start (void **start_argptr,
> >     dl_hwcap_check ();
> >     __tunables_init (_environ);
> > +  int32_t tes = TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t, NULL);
> > +  if (tes == 1)
> > +    __libc_enable_secure = 1;
> 
> OK, but maybe better to just do it in __tunables_init.  Any specific reason
> why you're doing it here?  For example, you've missed the hurd dl-sysdep
> change.

Updated to do this in __tubables_init as you've suggested.

Thanks,
Joe