1 | /* The tunable framework. See the README to know how to use the tunable in |
2 | a glibc module. |
3 | |
4 | Copyright (C) 2016-2024 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 | <https://www.gnu.org/licenses/>. */ |
20 | |
21 | #ifndef _TUNABLES_H_ |
22 | #define _TUNABLES_H_ |
23 | |
24 | #include <stdbool.h> |
25 | #include <stddef.h> |
26 | #include <stdint.h> |
27 | |
28 | typedef intmax_t tunable_num_t; |
29 | |
30 | typedef union |
31 | { |
32 | tunable_num_t numval; |
33 | struct tunable_str_t |
34 | { |
35 | const char *str; |
36 | size_t len; |
37 | } strval; |
38 | } tunable_val_t; |
39 | |
40 | typedef void (*tunable_callback_t) (tunable_val_t *); |
41 | |
42 | /* Full name for a tunable is top_ns.tunable_ns.id. */ |
43 | #define TUNABLE_NAME_S(top,ns,id) #top "." #ns "." #id |
44 | |
45 | #define TUNABLE_ENUM_NAME(__top,__ns,__id) TUNABLE_ENUM_NAME1 (__top,__ns,__id) |
46 | #define TUNABLE_ENUM_NAME1(__top,__ns,__id) __top ## _ ## __ns ## _ ## __id |
47 | |
48 | #include "dl-tunable-list.h" |
49 | |
50 | extern void __tunables_init (char **); |
51 | extern void __tunables_print (void); |
52 | extern bool __tunable_is_initialized (tunable_id_t); |
53 | extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t); |
54 | extern void __tunable_set_val (tunable_id_t, tunable_val_t *, tunable_num_t *, |
55 | tunable_num_t *); |
56 | extern void __tunable_get_default (tunable_id_t id, void *valp); |
57 | rtld_hidden_proto (__tunables_init) |
58 | rtld_hidden_proto (__tunables_print) |
59 | rtld_hidden_proto (__tunable_is_initialized) |
60 | rtld_hidden_proto (__tunable_get_val) |
61 | rtld_hidden_proto (__tunable_set_val) |
62 | rtld_hidden_proto (__tunable_get_default) |
63 | |
64 | /* Define TUNABLE_GET and TUNABLE_SET in short form if TOP_NAMESPACE and |
65 | TUNABLE_NAMESPACE are defined. This is useful shorthand to get and set |
66 | tunables within a module. */ |
67 | #if defined TOP_NAMESPACE && defined TUNABLE_NAMESPACE |
68 | # define TUNABLE_IS_INITIALIZED(__id) \ |
69 | TUNABLE_IS_INITIALIZED_FULL(TOP_NAMESPACE, TUNABLE_NAMESPACE, __id) |
70 | # define TUNABLE_GET_DEFAULT(__id, __type) \ |
71 | TUNABLE_GET_DEFAULT_FULL(TOP_NAMESPACE, TUNABLE_NAMESPACE,__id, __type) |
72 | # define TUNABLE_GET(__id, __type, __cb) \ |
73 | TUNABLE_GET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __type, __cb) |
74 | # define TUNABLE_SET(__id, __val) \ |
75 | TUNABLE_SET_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, __val) |
76 | # define TUNABLE_SET_WITH_BOUNDS(__id, __val, __min, __max) \ |
77 | TUNABLE_SET_WITH_BOUNDS_FULL (TOP_NAMESPACE, TUNABLE_NAMESPACE, __id, \ |
78 | __val, __min, __max) |
79 | #else |
80 | # define TUNABLE_IS_INITIALIZED(__top, __ns, __id) \ |
81 | TUNABLE_IS_INITIALIZED_FULL(__top, __ns, __id) |
82 | # define TUNABLE_GET_DEFAULT(__top, __ns, __type) \ |
83 | TUNABLE_GET_DEFAULT_FULL(__top, __ns, __id, __type) |
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, __val) \ |
87 | TUNABLE_SET_FULL (__top, __ns, __id, __val) |
88 | # define TUNABLE_SET_WITH_BOUNDS(__top, __ns, __id, __val, __min, __max) \ |
89 | TUNABLE_SET_WITH_BOUNDS_FULL (__top, __ns, __id, __val, __min, __max) |
90 | #endif |
91 | |
92 | /* Return whether the tunable was initialized by the environment variable. */ |
93 | #define TUNABLE_IS_INITIALIZED_FULL(__top, __ns, __id) \ |
94 | ({ \ |
95 | tunable_id_t id = TUNABLE_ENUM_NAME (__top, __ns, __id); \ |
96 | __tunable_is_initialized (id); \ |
97 | }) |
98 | |
99 | /* Return the default value of the tunable. */ |
100 | #define TUNABLE_GET_DEFAULT_FULL(__top, __ns, __id, __type) \ |
101 | ({ \ |
102 | tunable_id_t id = TUNABLE_ENUM_NAME (__top, __ns, __id); \ |
103 | __type __ret; \ |
104 | __tunable_get_default (id, &__ret); \ |
105 | __ret; \ |
106 | }) |
107 | |
108 | /* Get and return a tunable value. If the tunable was set externally and __CB |
109 | is defined then call __CB before returning the value. */ |
110 | #define TUNABLE_GET_FULL(__top, __ns, __id, __type, __cb) \ |
111 | ({ \ |
112 | tunable_id_t id = TUNABLE_ENUM_NAME (__top, __ns, __id); \ |
113 | __type ret; \ |
114 | __tunable_get_val (id, &ret, __cb); \ |
115 | ret; \ |
116 | }) |
117 | |
118 | /* Set a tunable value. */ |
119 | #define TUNABLE_SET_FULL(__top, __ns, __id, __val) \ |
120 | ({ \ |
121 | __tunable_set_val (TUNABLE_ENUM_NAME (__top, __ns, __id), \ |
122 | & (tunable_val_t) {.numval = __val}, NULL, NULL); \ |
123 | }) |
124 | |
125 | /* Set a tunable value together with min/max values. */ |
126 | #define TUNABLE_SET_WITH_BOUNDS_FULL(__top, __ns, __id,__val, __min, __max) \ |
127 | ({ \ |
128 | __tunable_set_val (TUNABLE_ENUM_NAME (__top, __ns, __id), \ |
129 | & (tunable_val_t) {.numval = __val}, \ |
130 | & (tunable_num_t) {__min}, \ |
131 | & (tunable_num_t) {__max}); \ |
132 | }) |
133 | |
134 | /* Namespace sanity for callback functions. Use this macro to keep the |
135 | namespace of the modules clean. */ |
136 | #define TUNABLE_CALLBACK(__name) _dl_tunable_ ## __name |
137 | |
138 | static __always_inline bool |
139 | tunable_val_lt (tunable_num_t lhs, tunable_num_t rhs, bool unsigned_cmp) |
140 | { |
141 | if (unsigned_cmp) |
142 | return (uintmax_t) lhs < (uintmax_t) rhs; |
143 | else |
144 | return lhs < rhs; |
145 | } |
146 | |
147 | static __always_inline bool |
148 | tunable_val_gt (tunable_num_t lhs, tunable_num_t rhs, bool unsigned_cmp) |
149 | { |
150 | if (unsigned_cmp) |
151 | return (uintmax_t) lhs > (uintmax_t) rhs; |
152 | else |
153 | return lhs > rhs; |
154 | } |
155 | |
156 | /* Compare two name strings, bounded by the name hardcoded in glibc. */ |
157 | static __always_inline bool |
158 | tunable_is_name (const char *orig, const char *envname) |
159 | { |
160 | for (;*orig != '\0' && *envname != '\0'; envname++, orig++) |
161 | if (*orig != *envname) |
162 | break; |
163 | |
164 | /* The ENVNAME is immediately followed by a value. */ |
165 | if (*orig == '\0' && *envname == '=') |
166 | return true; |
167 | else |
168 | return false; |
169 | } |
170 | |
171 | #endif |
172 | |