1/* Sort array of link maps according to dependencies.
2 Copyright (C) 2017-2021 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#include <ldsodefs.h>
20
21
22/* Sort array MAPS according to dependencies of the contained objects.
23 Array USED, if non-NULL, is permutated along MAPS. If FOR_FINI this is
24 called for finishing an object. */
25void
26_dl_sort_maps (struct link_map **maps, unsigned int nmaps, char *used,
27 bool for_fini)
28{
29 /* A list of one element need not be sorted. */
30 if (nmaps <= 1)
31 return;
32
33 unsigned int i = 0;
34 uint16_t seen[nmaps];
35 memset (seen, 0, nmaps * sizeof (seen[0]));
36 while (1)
37 {
38 /* Keep track of which object we looked at this round. */
39 ++seen[i];
40 struct link_map *thisp = maps[i];
41
42 if (__glibc_unlikely (for_fini))
43 {
44 /* Do not handle ld.so in secondary namespaces and objects which
45 are not removed. */
46 if (thisp != thisp->l_real || thisp->l_idx == -1)
47 goto skip;
48 }
49
50 /* Find the last object in the list for which the current one is
51 a dependency and move the current object behind the object
52 with the dependency. */
53 unsigned int k = nmaps - 1;
54 while (k > i)
55 {
56 struct link_map **runp = maps[k]->l_initfini;
57 if (runp != NULL)
58 /* Look through the dependencies of the object. */
59 while (*runp != NULL)
60 if (__glibc_unlikely (*runp++ == thisp))
61 {
62 move:
63 /* Move the current object to the back past the last
64 object with it as the dependency. */
65 memmove (&maps[i], &maps[i + 1],
66 (k - i) * sizeof (maps[0]));
67 maps[k] = thisp;
68
69 if (used != NULL)
70 {
71 char here_used = used[i];
72 memmove (&used[i], &used[i + 1],
73 (k - i) * sizeof (used[0]));
74 used[k] = here_used;
75 }
76
77 if (seen[i + 1] > nmaps - i)
78 {
79 ++i;
80 goto next_clear;
81 }
82
83 uint16_t this_seen = seen[i];
84 memmove (&seen[i], &seen[i + 1], (k - i) * sizeof (seen[0]));
85 seen[k] = this_seen;
86
87 goto next;
88 }
89
90 if (__glibc_unlikely (for_fini && maps[k]->l_reldeps != NULL))
91 {
92 unsigned int m = maps[k]->l_reldeps->act;
93 struct link_map **relmaps = &maps[k]->l_reldeps->list[0];
94
95 /* Look through the relocation dependencies of the object. */
96 while (m-- > 0)
97 if (__glibc_unlikely (relmaps[m] == thisp))
98 {
99 /* If a cycle exists with a link time dependency,
100 preserve the latter. */
101 struct link_map **runp = thisp->l_initfini;
102 if (runp != NULL)
103 while (*runp != NULL)
104 if (__glibc_unlikely (*runp++ == maps[k]))
105 goto ignore;
106 goto move;
107 }
108 ignore:;
109 }
110
111 --k;
112 }
113
114 skip:
115 if (++i == nmaps)
116 break;
117 next_clear:
118 memset (&seen[i], 0, (nmaps - i) * sizeof (seen[0]));
119
120 next:;
121 }
122}
123