1 /* Hardware capability support for run-time dynamic loader.
2 Copyright (C) 2012-2023 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 #include <assert.h>
20 #include <elf.h>
21 #include <errno.h>
22 #include <libintl.h>
23 #include <unistd.h>
24 #include <ldsodefs.h>
25
26 #include <dl-procinfo.h>
27 #include <dl-hwcaps.h>
28
29 /* This is the result of counting the substrings in a colon-separated
30 hwcaps string. */
31 struct hwcaps_counts
32 {
33 /* Number of substrings. */
34 size_t count;
35
36 /* Sum of the individual substring lengths (without separators or
37 null terminators). */
38 size_t total_length;
39
40 /* Maximum length of an individual substring. */
41 size_t maximum_length;
42 };
43
44 /* Update *COUNTS according to the contents of HWCAPS. Skip over
45 entries whose bit is not set in MASK. */
46 static void
47 update_hwcaps_counts (struct hwcaps_counts *counts, const char *hwcaps,
48 uint32_t bitmask, const char *mask)
49 {
50 struct dl_hwcaps_split_masked sp;
51 _dl_hwcaps_split_masked_init (&sp, hwcaps, bitmask, mask);
52 while (_dl_hwcaps_split_masked (&sp))
53 {
54 ++counts->count;
55 counts->total_length += sp.split.length;
56 if (sp.split.length > counts->maximum_length)
57 counts->maximum_length = sp.split.length;
58 }
59 }
60
61 /* State for copy_hwcaps. Must be initialized to point to
62 the storage areas for the array and the strings themselves. */
63 struct copy_hwcaps
64 {
65 struct r_strlenpair *next_pair;
66 char *next_string;
67 };
68
69 /* Copy HWCAPS into the string pairs and strings, advancing *TARGET.
70 Skip over entries whose bit is not set in MASK. */
71 static void
72 copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
73 uint32_t bitmask, const char *mask)
74 {
75 struct dl_hwcaps_split_masked sp;
76 _dl_hwcaps_split_masked_init (&sp, hwcaps, bitmask, mask);
77 while (_dl_hwcaps_split_masked (&sp))
78 {
79 target->next_pair->str = target->next_string;
80 char *slash = __mempcpy (__mempcpy (target->next_string,
81 GLIBC_HWCAPS_PREFIX,
82 strlen (GLIBC_HWCAPS_PREFIX)),
83 sp.split.segment, sp.split.length);
84 *slash = '/';
85 target->next_pair->len
86 = strlen (GLIBC_HWCAPS_PREFIX) + sp.split.length + 1;
87 ++target->next_pair;
88 target->next_string = slash + 1;
89 }
90 }
91
92 struct dl_hwcaps_priority *_dl_hwcaps_priorities;
93 uint32_t _dl_hwcaps_priorities_length;
94
95 /* Allocate _dl_hwcaps_priorities and fill it with data. */
96 static void
97 compute_priorities (size_t total_count, const char *prepend,
98 uint32_t bitmask, const char *mask)
99 {
100 _dl_hwcaps_priorities = malloc (total_count
101 * sizeof (*_dl_hwcaps_priorities));
102 if (_dl_hwcaps_priorities == NULL)
103 _dl_signal_error (ENOMEM, NULL, NULL,
104 N_("cannot create HWCAP priorities"));
105 _dl_hwcaps_priorities_length = total_count;
106
107 /* First the prepended subdirectories. */
108 size_t i = 0;
109 {
110 struct dl_hwcaps_split sp;
111 _dl_hwcaps_split_init (&sp, prepend);
112 while (_dl_hwcaps_split (&sp))
113 {
114 _dl_hwcaps_priorities[i].name = sp.segment;
115 _dl_hwcaps_priorities[i].name_length = sp.length;
116 _dl_hwcaps_priorities[i].priority = i + 1;
117 ++i;
118 }
119 }
120
121 /* Then the built-in subdirectories that are actually active. */
122 {
123 struct dl_hwcaps_split_masked sp;
124 _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
125 while (_dl_hwcaps_split_masked (&sp))
126 {
127 _dl_hwcaps_priorities[i].name = sp.split.segment;
128 _dl_hwcaps_priorities[i].name_length = sp.split.length;
129 _dl_hwcaps_priorities[i].priority = i + 1;
130 ++i;
131 }
132 }
133 assert (i == total_count);
134 }
135
136 /* Sort the _dl_hwcaps_priorities array by name. */
137 static void
138 sort_priorities_by_name (void)
139 {
140 /* Insertion sort. There is no need to link qsort into the dynamic
141 loader for such a short array. */
142 for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
143 for (size_t j = i; j > 0; --j)
144 {
145 struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
146 struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;
147
148 /* Bail out if current is greater or equal to the previous
149 value. */
150 uint32_t to_compare;
151 if (current->name_length < previous->name_length)
152 to_compare = current->name_length;
153 else
154 to_compare = previous->name_length;
155 int cmp = memcmp (current->name, previous->name, to_compare);
156 if (cmp > 0
157 || (cmp == 0 && current->name_length >= previous->name_length))
158 break;
159
160 /* Swap *previous and *current. */
161 struct dl_hwcaps_priority tmp = *previous;
162 *previous = *current;
163 *current = tmp;
164 }
165 }
166
167 /* Return an array of useful/necessary hardware capability names. */
168 const struct r_strlenpair *
169 _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
170 const char *glibc_hwcaps_mask,
171 size_t *sz, size_t *max_capstrlen)
172 {
173 /* glibc-hwcaps subdirectories. */
174 uint32_t hwcaps_subdirs_active = _dl_hwcaps_subdirs_active ();
175 struct hwcaps_counts hwcaps_counts = { 0, };
176 update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
177 update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
178 hwcaps_subdirs_active, glibc_hwcaps_mask);
179 compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
180 hwcaps_subdirs_active, glibc_hwcaps_mask);
181 sort_priorities_by_name ();
182
183 /* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
184 and a "/" suffix once stored in the result. */
185 hwcaps_counts.maximum_length += strlen (GLIBC_HWCAPS_PREFIX) + 1;
186 size_t total = (hwcaps_counts.count * (strlen (GLIBC_HWCAPS_PREFIX) + 1)
187 + hwcaps_counts.total_length);
188
189 *sz = hwcaps_counts.count + 1;
190
191 /* This is the overall result. */
192 struct r_strlenpair *overall_result
193 = malloc (*sz * sizeof (*overall_result) + total);
194 if (overall_result == NULL)
195 _dl_signal_error (ENOMEM, NULL, NULL,
196 N_("cannot create capability list"));
197
198 /* Fill in the glibc-hwcaps subdirectories. */
199 {
200 struct copy_hwcaps target;
201 target.next_pair = overall_result;
202 target.next_string = (char *) (overall_result + *sz);
203 copy_hwcaps (&target, glibc_hwcaps_prepend, -1, NULL);
204 copy_hwcaps (&target, _dl_hwcaps_subdirs,
205 hwcaps_subdirs_active, glibc_hwcaps_mask);
206
207 /* Append an empty entry for the base directory itself. */
208 target.next_pair->str = target.next_string;
209 target.next_pair->len = 0;
210 }
211
212 /* The maximum string length. */
213 *max_capstrlen = hwcaps_counts.maximum_length;
214
215 return overall_result;
216 }