glibc/elf/dl-tunables.h

/* The tunable framework.  See the README to know how to use the tunable in
   a glibc module.

   Copyright (C) 2016 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/>.  */

#ifndef _TUNABLES_H_
#define _TUNABLES_H_

#if !HAVE_TUNABLES
static inline void
__always_inline
__tunables_init (char **unused __attribute__ ((unused)))
{
  /* This is optimized out if tunables are not enabled.  */
}
#else

# include <stddef.h>
# include "dl-tunable-types.h"

/* A tunable.  */
struct _tunable
{
  const char *name;			/* Internal name of the tunable.  */
  tunable_type_t type;			/* Data type of the tunable.  */
  tunable_val_t val;			/* The value.  */
  const char *strval;			/* The string containing the value,
					   points into envp.  */
  bool is_secure;			/* Whether the tunable must be read
					   even for setuid binaries.  Note that
					   even if the tunable is read, it may
					   not get used by the target module if
					   the value is considered unsafe.  */
  /* Compatibility elements.  */
  const char *env_alias;		/* The compatibility environment
					   variable name.  */
};

typedef struct _tunable tunable_t;

/* Full name for a tunable is top_ns.tunable_ns.id.  */
# define TUNABLE_NAME_S(top,ns,id) #top "." #ns "." #id

# define TUNABLE_ENUM_NAME(top,ns,id) TUNABLE_ENUM_NAME1 (top,ns,id)
# define TUNABLE_ENUM_NAME1(top,ns,id) top ## _ ## ns ## _ ## id

# include "dl-tunable-list.h"

extern void __tunables_init (char **);
extern void __tunable_set_val (tunable_id_t, void *, tunable_callback_t);

/* Check if the tunable has been set to a non-default value and if it is, copy
   it over into __VAL.  */
# define TUNABLE_SET_VAL(__id,__val) \
({									      \
  __tunable_set_val							      \
   (TUNABLE_ENUM_NAME (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id), (__val),      \
    NULL);								      \
})

/* Same as TUNABLE_SET_VAL, but also call the callback function __CB.  */
# define TUNABLE_SET_VAL_WITH_CALLBACK(__id,__val,__cb) \
({									      \
  __tunable_set_val							      \
   (TUNABLE_ENUM_NAME (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id), (__val),      \
    DL_TUNABLE_CALLBACK (__cb));					      \
})

/* Namespace sanity for callback functions.  Use this macro to keep the
   namespace of the modules clean.  */
# define DL_TUNABLE_CALLBACK(__name) _dl_tunable_ ## __name

# define TUNABLES_FRONTEND_valstring 1
/* The default value for TUNABLES_FRONTEND.  */
# define TUNABLES_FRONTEND_yes TUNABLES_FRONTEND_valstring
#endif
#endif