1/* Global list of NSS service modules.
2 Copyright (c) 2020-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#ifndef _NSS_MODULE_H
20#define _NSS_MODULE_H
21
22#include <nss.h>
23#include <stdbool.h>
24
25/* See nss_database.h for a summary of how this relates. */
26
27/* Typed function pointers for all functions that can be defined by a
28 service module. */
29struct nss_module_functions
30{
31#undef DEFINE_NSS_FUNCTION
32#define DEFINE_NSS_FUNCTION(f) nss_##f *f;
33#include "function.def"
34};
35
36/* Number of elements of the nss_module_functions_untyped array. */
37enum
38 {
39 nss_module_functions_count = (sizeof (struct nss_module_functions)
40 / sizeof (void *))
41 };
42
43/* Untyped version of struct nss_module_functions, for consistent
44 processing purposes. */
45typedef void *nss_module_functions_untyped[nss_module_functions_count];
46
47/* Locate the nss_files functions, as if by dlopen/dlsym. */
48void __nss_files_functions (nss_module_functions_untyped pointers)
49 attribute_hidden;
50
51/* Initialization state of a NSS module. */
52enum nss_module_state
53{
54 nss_module_uninitialized,
55 nss_module_loaded,
56 nss_module_failed,
57};
58
59/* A NSS service module (potentially unloaded). Client code should
60 use the functions below. */
61struct nss_module
62{
63 /* Actual type is enum nss_module_state. Use int due to atomic
64 access. Used in a double-checked locking idiom. */
65 int state;
66
67 /* The function pointers in the module. */
68 union
69 {
70 struct nss_module_functions typed;
71 nss_module_functions_untyped untyped;
72 } functions;
73
74 /* Only used for __libc_freeres unloading. */
75 void *handle;
76
77 /* The next module in the list. */
78 struct nss_module *next;
79
80 /* The name of the module (as it appears in /etc/nsswitch.conf). */
81 char name[];
82};
83
84/* Allocates the NSS module NAME (of NAME_LENGTH bytes) and places it
85 into the global list. If it already exists in the list, return the
86 pre-existing module. This does not actually load the module.
87 Returns NULL on memory allocation failure. */
88struct nss_module *__nss_module_allocate (const char *name,
89 size_t name_length) attribute_hidden;
90
91/* Ensures that MODULE is in a loaded or failed state. */
92bool __nss_module_load (struct nss_module *module) attribute_hidden;
93
94/* Ensures that MODULE is loaded and returns a pointer to the function
95 NAME defined in it. Returns NULL if MODULE could not be loaded, or
96 if the function NAME is not defined in the module. */
97void *__nss_module_get_function (struct nss_module *module, const char *name)
98 attribute_hidden;
99
100/* Block attempts to dlopen any module we haven't already opened. */
101void __nss_module_disable_loading (void);
102
103#endif /* NSS_MODULE_H */
104