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fd5b9b44 | 1 | /* NSS actions, elements in a nsswitch.conf configuration line. |
581c785b | 2 | Copyright (c) 2020-2022 Free Software Foundation, Inc. |
fd5b9b44 FW |
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 | ||
f8847d83 | 19 | #include <nsswitch.h> |
fd5b9b44 FW |
20 | |
21 | #include <string.h> | |
22 | #include <libc-lock.h> | |
23 | ||
24 | /* Maintain a global list of NSS action lists. Since most databases | |
25 | use the same list of actions, this list is usually short. | |
26 | Deduplication in __nss_action_allocate ensures that the list does | |
27 | not grow without bounds. */ | |
28 | ||
29 | struct nss_action_list_wrapper | |
30 | { | |
31 | /* The next element of the list. */ | |
32 | struct nss_action_list_wrapper *next; | |
33 | ||
34 | /* Number of elements in the list (excluding the terminator). */ | |
35 | size_t count; | |
36 | ||
37 | /* NULL-terminated list of actions. */ | |
38 | struct nss_action actions[]; | |
39 | }; | |
40 | ||
41 | /* Toplevel list of allocated NSS action lists. */ | |
42 | static struct nss_action_list_wrapper *nss_actions; | |
43 | ||
44 | /* Lock covers the nss_actions list. */ | |
45 | __libc_lock_define (static, nss_actions_lock); | |
46 | ||
47 | /* Returns true if the actions are equal (same module, same actions | |
48 | array). */ | |
49 | static bool | |
50 | actions_equal (const struct nss_action *a, const struct nss_action *b) | |
51 | { | |
52 | return a->module == b->module && a->action_bits == b->action_bits; | |
53 | } | |
54 | ||
55 | ||
56 | /* Returns true if COUNT actions at A and B are equal (according to | |
57 | actions_equal above). Caller must ensure that either A or B have at | |
58 | least COUNT actions. */ | |
59 | static bool | |
60 | action_lists_equal (const struct nss_action *a, const struct nss_action *b, | |
61 | size_t count) | |
62 | { | |
63 | for (size_t i = 0; i < count; ++i) | |
64 | if (!actions_equal (a + i, b + i)) | |
65 | return false; | |
66 | return true; | |
67 | } | |
68 | ||
69 | /* Returns a pre-allocated action list for COUNT actions at ACTIONS, | |
70 | or NULL if no such list exists. */ | |
71 | static nss_action_list | |
72 | find_allocated (struct nss_action *actions, size_t count) | |
73 | { | |
74 | for (struct nss_action_list_wrapper *p = nss_actions; p != NULL; p = p->next) | |
75 | if (p->count == count && action_lists_equal (p->actions, actions, count)) | |
76 | return p->actions; | |
77 | return NULL; | |
78 | } | |
79 | ||
80 | nss_action_list | |
81 | __nss_action_allocate (struct nss_action *actions, size_t count) | |
82 | { | |
83 | nss_action_list result = NULL; | |
84 | __libc_lock_lock (nss_actions_lock); | |
85 | ||
86 | result = find_allocated (actions, count); | |
87 | if (result == NULL) | |
88 | { | |
89 | struct nss_action_list_wrapper *wrapper | |
90 | = malloc (sizeof (*wrapper) + sizeof (*actions) * count); | |
91 | if (wrapper != NULL) | |
92 | { | |
93 | wrapper->next = nss_actions; | |
94 | wrapper->count = count; | |
95 | memcpy (wrapper->actions, actions, sizeof (*actions) * count); | |
96 | nss_actions = wrapper; | |
97 | result = wrapper->actions; | |
98 | } | |
99 | } | |
100 | ||
101 | __libc_lock_unlock (nss_actions_lock); | |
102 | return result; | |
103 | } | |
104 | ||
105 | void __libc_freeres_fn_section | |
106 | __nss_action_freeres (void) | |
107 | { | |
108 | struct nss_action_list_wrapper *current = nss_actions; | |
109 | while (current != NULL) | |
110 | { | |
111 | struct nss_action_list_wrapper *next = current->next; | |
112 | free (current); | |
113 | current = next; | |
114 | } | |
115 | nss_actions = NULL; | |
116 | } |