1/* The tunable framework. See the README to know how to use the tunable in
2 a glibc module.
3
4 Copyright (C) 2016-2019 Free Software Foundation, Inc.
5 This file is part of the GNU C Library.
6
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public
9 License as published by the Free Software Foundation; either
10 version 2.1 of the License, or (at your option) any later version.
11
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
16
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; if not, see
19 <http://www.gnu.org/licenses/>. */
20
21#ifndef _TUNABLES_H_
22#define _TUNABLES_H_
23
24#if !HAVE_TUNABLES
25static inline void
26__always_inline
27__tunables_init (char **unused __attribute__ ((unused)))
28{
29 /* This is optimized out if tunables are not enabled. */
30}
31#else
32
33# include <stddef.h>
34# include "dl-tunable-types.h"
35
36/* A tunable. */
37struct _tunable
38{
39 const char *name; /* Internal name of the tunable. */
40 tunable_type_t type; /* Data type of the tunable. */
41 tunable_val_t val; /* The value. */
42 bool initialized; /* Flag to indicate that the tunable is
43 initialized. */
44 tunable_seclevel_t security_level; /* Specify the security level for the
45 tunable with respect to AT_SECURE
46 programs. See description of
47 tunable_seclevel_t to see a
48 description of the values.
49
50 Note that even if the tunable is
51 read, it may not get used by the
52 target module if the value is
53 considered unsafe. */
54 /* Compatibility elements. */
55 const char *env_alias; /* The compatibility environment
56 variable name. */
57};
58
59typedef struct _tunable tunable_t;
60
61/* Full name for a tunable is top_ns.tunable_ns.id. */
62# define TUNABLE_NAME_S(top,ns,id) #top "." #ns "." #id
63
64# define TUNABLE_ENUM_NAME(__top,__ns,__id) TUNABLE_ENUM_NAME1 (__top,__ns,__id)
65# define TUNABLE_ENUM_NAME1(__top,__ns,__id) __top ## _ ## __ns ## _ ## __id
66
67# include "dl-tunable-list.h"
68
69extern void __tunables_init (char **);
70extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
71extern void __tunable_set_val (tunable_id_t, void *);
72rtld_hidden_proto (__tunables_init)
73rtld_hidden_proto (__tunable_get_val)
74
75/* Define TUNABLE_GET and TUNABLE_SET in short form if TOP_NAMESPACE and
76 TUNABLE_NAMESPACE are defined. This is useful shorthand to get and set
77 tunables within a module. */
78#if defined TOP_NAMESPACE && defined TUNABLE_NAMESPACE
79# define TUNABLE_GET(__id, __type, __cb) \
80 TUNABLE_GET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __type, __cb)
81# define TUNABLE_SET(__id, __type, __val) \
82 TUNABLE_SET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __type, __val)
83#else
84# define TUNABLE_GET(__top, __ns, __id, __type, __cb) \
85 TUNABLE_GET_FULL (__top, __ns, __id, __type, __cb)
86# define TUNABLE_SET(__top, __ns, __id, __type, __val) \
87 TUNABLE_SET_FULL (__top, __ns, __id, __type, __val)
88#endif
89
90/* Get and return a tunable value. If the tunable was set externally and __CB
91 is defined then call __CB before returning the value. */
92# define TUNABLE_GET_FULL(__top, __ns, __id, __type, __cb) \
93({ \
94 tunable_id_t id = TUNABLE_ENUM_NAME (__top, __ns, __id); \
95 __type ret; \
96 __tunable_get_val (id, &ret, __cb); \
97 ret; \
98})
99
100/* Set a tunable value. */
101# define TUNABLE_SET_FULL(__top, __ns, __id, __type, __val) \
102({ \
103 __tunable_set_val (TUNABLE_ENUM_NAME (__top, __ns, __id), \
104 & (__type) {__val}); \
105})
106
107/* Namespace sanity for callback functions. Use this macro to keep the
108 namespace of the modules clean. */
109# define TUNABLE_CALLBACK(__name) _dl_tunable_ ## __name
110
111# define TUNABLES_FRONTEND_valstring 1
112/* The default value for TUNABLES_FRONTEND. */
113# define TUNABLES_FRONTEND_yes TUNABLES_FRONTEND_valstring
114
115/* Compare two name strings, bounded by the name hardcoded in glibc. */
116static inline bool
117__always_inline
118tunable_is_name (const char *orig, const char *envname)
119{
120 for (;*orig != '\0' && *envname != '\0'; envname++, orig++)
121 if (*orig != *envname)
122 break;
123
124 /* The ENVNAME is immediately followed by a value. */
125 if (*orig == '\0' && *envname == '=')
126 return true;
127 else
128 return false;
129}
130
131#endif
132#endif
133