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/* The tunable framework. See the README to know how to use the tunable in
a glibc module.
Copyright (C) 2016-2021 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
<https://www.gnu.org/licenses/>. */
#ifndef _TUNABLES_H_
#define _TUNABLES_H_
#include <stdbool.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. */
bool initialized; /* Flag to indicate that the tunable is
initialized. */
tunable_seclevel_t security_level; /* Specify the security level for the
tunable with respect to AT_SECURE
programs. See description of
tunable_seclevel_t to see a
description of the values.
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_get_val (tunable_id_t, void *, tunable_callback_t);
extern void __tunable_set_val (tunable_id_t, void *, void *, void *);
rtld_hidden_proto (__tunables_init)
rtld_hidden_proto (__tunable_get_val)
rtld_hidden_proto (__tunable_set_val)
/* Define TUNABLE_GET and TUNABLE_SET in short form if TOP_NAMESPACE and
TUNABLE_NAMESPACE are defined. This is useful shorthand to get and set
tunables within a module. */
#if defined TOP_NAMESPACE && defined TUNABLE_NAMESPACE
# define TUNABLE_GET(__id, __type, __cb) \
TUNABLE_GET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __type, __cb)
# define TUNABLE_SET(__id, __type, __val) \
TUNABLE_SET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __type, __val)
# define TUNABLE_SET_WITH_BOUNDS(__id, __type, __val, __min, __max) \
TUNABLE_SET_WITH_BOUNDS_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, \
__type, __val, __min, __max)
#else
# define TUNABLE_GET(__top, __ns, __id, __type, __cb) \
TUNABLE_GET_FULL (__top, __ns, __id, __type, __cb)
# define TUNABLE_SET(__top, __ns, __id, __type, __val) \
TUNABLE_SET_FULL (__top, __ns, __id, __type, __val)
# define TUNABLE_SET_WITH_BOUNDS(__top, __ns, __id, __type, __val, \
__min, __max) \
TUNABLE_SET_WITH_BOUNDS_FULL (__top, __ns, __id, __type, __val, \
__min, __max)
#endif
/* Get and return a tunable value. If the tunable was set externally and __CB
is defined then call __CB before returning the value. */
# define TUNABLE_GET_FULL(__top, __ns, __id, __type, __cb) \
({ \
tunable_id_t id = TUNABLE_ENUM_NAME (__top, __ns, __id); \
__type ret; \
__tunable_get_val (id, &ret, __cb); \
ret; \
})
/* Set a tunable value. */
# define TUNABLE_SET_FULL(__top, __ns, __id, __type, __val) \
({ \
__tunable_set_val (TUNABLE_ENUM_NAME (__top, __ns, __id), \
& (__type) {__val}, NULL, NULL); \
})
/* Set a tunable value together with min/max values. */
# define TUNABLE_SET_WITH_BOUNDS_FULL(__top, __ns, __id, __type, __val, \
__min, __max) \
({ \
__tunable_set_val (TUNABLE_ENUM_NAME (__top, __ns, __id), \
& (__type) {__val}, & (__type) {__min}, \
& (__type) {__max}); \
})
/* Namespace sanity for callback functions. Use this macro to keep the
namespace of the modules clean. */
# define TUNABLE_CALLBACK(__name) _dl_tunable_ ## __name
# define TUNABLES_FRONTEND_valstring 1
/* The default value for TUNABLES_FRONTEND. */
# define TUNABLES_FRONTEND_yes TUNABLES_FRONTEND_valstring
/* Compare two name strings, bounded by the name hardcoded in glibc. */
static __always_inline bool
tunable_is_name (const char *orig, const char *envname)
{
for (;*orig != '\0' && *envname != '\0'; envname++, orig++)
if (*orig != *envname)
break;
/* The ENVNAME is immediately followed by a value. */
if (*orig == '\0' && *envname == '=')
return true;
else
return false;
}
#endif
#endif
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