aboutsummaryrefslogtreecommitdiff
path: root/elf/dl-tunables.h
blob: 969e50327bb77360d9594d42b6522485fa67dd4c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/* The tunable framework.  See the README to know how to use the tunable in
   a glibc module.

   Copyright (C) 2016-2020 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_

#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 *);
rtld_hidden_proto (__tunables_init)
rtld_hidden_proto (__tunable_get_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)
#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)
#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});				      \
})

/* 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