aboutsummaryrefslogtreecommitdiff
path: root/elf/dl-hwcaps.c
blob: 75a27d694451f71cd98666ac52a1c1a42944a72a (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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
/* Hardware capability support for run-time dynamic loader.
   Copyright (C) 2012-2024 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/>.  */

#include <assert.h>
#include <elf.h>
#include <errno.h>
#include <libintl.h>
#include <unistd.h>
#include <ldsodefs.h>

#include <dl-procinfo.h>
#include <dl-hwcaps.h>

/* This is the result of counting the substrings in a colon-separated
   hwcaps string.  */
struct hwcaps_counts
{
  /* Number of substrings.  */
  size_t count;

  /* Sum of the individual substring lengths (without separators or
     null terminators).  */
  size_t total_length;

  /* Maximum length of an individual substring.  */
  size_t maximum_length;
};

/* Update *COUNTS according to the contents of HWCAPS.  Skip over
   entries whose bit is not set in MASK.  */
static void
update_hwcaps_counts (struct hwcaps_counts *counts, const char *hwcaps,
		      uint32_t bitmask, const char *mask)
{
  struct dl_hwcaps_split_masked sp;
  _dl_hwcaps_split_masked_init (&sp, hwcaps, bitmask, mask);
  while (_dl_hwcaps_split_masked (&sp))
    {
      ++counts->count;
      counts->total_length += sp.split.length;
      if (sp.split.length > counts->maximum_length)
	counts->maximum_length = sp.split.length;
    }
}

/* State for copy_hwcaps.  Must be initialized to point to
   the storage areas for the array and the strings themselves.  */
struct copy_hwcaps
{
  struct r_strlenpair *next_pair;
  char *next_string;
};

/* Copy HWCAPS into the string pairs and strings, advancing *TARGET.
   Skip over entries whose bit is not set in MASK.  */
static void
copy_hwcaps (struct copy_hwcaps *target, const char *hwcaps,
	     uint32_t bitmask, const char *mask)
{
  struct dl_hwcaps_split_masked sp;
  _dl_hwcaps_split_masked_init (&sp, hwcaps, bitmask, mask);
  while (_dl_hwcaps_split_masked (&sp))
    {
      target->next_pair->str = target->next_string;
      char *slash = __mempcpy (__mempcpy (target->next_string,
					  GLIBC_HWCAPS_PREFIX,
					  strlen (GLIBC_HWCAPS_PREFIX)),
			       sp.split.segment, sp.split.length);
      *slash = '/';
      target->next_pair->len
	= strlen (GLIBC_HWCAPS_PREFIX) + sp.split.length + 1;
      ++target->next_pair;
      target->next_string = slash + 1;
    }
}

struct dl_hwcaps_priority *_dl_hwcaps_priorities;
uint32_t _dl_hwcaps_priorities_length;

/* Allocate _dl_hwcaps_priorities and fill it with data.  */
static void
compute_priorities (size_t total_count, const char *prepend,
		    uint32_t bitmask, const char *mask)
{
  _dl_hwcaps_priorities = malloc (total_count
				  * sizeof (*_dl_hwcaps_priorities));
  if (_dl_hwcaps_priorities == NULL)
    _dl_signal_error (ENOMEM, NULL, NULL,
		      N_("cannot create HWCAP priorities"));
  _dl_hwcaps_priorities_length = total_count;

  /* First the prepended subdirectories.  */
  size_t i = 0;
  {
    struct dl_hwcaps_split sp;
    _dl_hwcaps_split_init (&sp, prepend);
    while (_dl_hwcaps_split (&sp))
      {
	_dl_hwcaps_priorities[i].name = sp.segment;
	_dl_hwcaps_priorities[i].name_length = sp.length;
	_dl_hwcaps_priorities[i].priority = i + 1;
	++i;
      }
  }

  /* Then the built-in subdirectories that are actually active.  */
  {
    struct dl_hwcaps_split_masked sp;
    _dl_hwcaps_split_masked_init (&sp, _dl_hwcaps_subdirs, bitmask, mask);
    while (_dl_hwcaps_split_masked (&sp))
      {
	_dl_hwcaps_priorities[i].name = sp.split.segment;
	_dl_hwcaps_priorities[i].name_length = sp.split.length;
	_dl_hwcaps_priorities[i].priority = i + 1;
	++i;
      }
  }
  assert (i == total_count);
}

/* Sort the _dl_hwcaps_priorities array by name.  */
static void
sort_priorities_by_name (void)
{
  /* Insertion sort.  There is no need to link qsort into the dynamic
     loader for such a short array.  */
  for (size_t i = 1; i < _dl_hwcaps_priorities_length; ++i)
    for (size_t j = i; j > 0; --j)
      {
	struct dl_hwcaps_priority *previous = _dl_hwcaps_priorities + j - 1;
	struct dl_hwcaps_priority *current = _dl_hwcaps_priorities + j;

	/* Bail out if current is greater or equal to the previous
	   value.  */
	uint32_t to_compare;
	if (current->name_length < previous->name_length)
	  to_compare = current->name_length;
	else
	  to_compare = previous->name_length;
	int cmp = memcmp (current->name, previous->name, to_compare);
	if (cmp > 0
	    || (cmp == 0 && current->name_length >= previous->name_length))
	  break;

	/* Swap *previous and *current.  */
	struct dl_hwcaps_priority tmp = *previous;
	*previous = *current;
	*current = tmp;
      }
}

/* Return an array of useful/necessary hardware capability names.  */
const struct r_strlenpair *
_dl_important_hwcaps (const char *glibc_hwcaps_prepend,
		      const char *glibc_hwcaps_mask,
		      size_t *sz, size_t *max_capstrlen)
{
  /* glibc-hwcaps subdirectories.  */
  uint32_t hwcaps_subdirs_active = _dl_hwcaps_subdirs_active ();
  struct hwcaps_counts hwcaps_counts =  { 0, };
  update_hwcaps_counts (&hwcaps_counts, glibc_hwcaps_prepend, -1, NULL);
  update_hwcaps_counts (&hwcaps_counts, _dl_hwcaps_subdirs,
			hwcaps_subdirs_active, glibc_hwcaps_mask);
  compute_priorities (hwcaps_counts.count, glibc_hwcaps_prepend,
		      hwcaps_subdirs_active, glibc_hwcaps_mask);
  sort_priorities_by_name ();

  /* Each hwcaps subdirectory has a GLIBC_HWCAPS_PREFIX string prefix
     and a "/" suffix once stored in the result.  */
  hwcaps_counts.maximum_length += strlen (GLIBC_HWCAPS_PREFIX) + 1;
  size_t total = (hwcaps_counts.count * (strlen (GLIBC_HWCAPS_PREFIX) + 1)
		  + hwcaps_counts.total_length);

  *sz = hwcaps_counts.count + 1;

  /* This is the overall result.  */
  struct r_strlenpair *overall_result
    = malloc (*sz * sizeof (*overall_result) + total);
  if (overall_result == NULL)
    _dl_signal_error (ENOMEM, NULL, NULL,
		      N_("cannot create capability list"));

  /* Fill in the glibc-hwcaps subdirectories.  */
  {
    struct copy_hwcaps target;
    target.next_pair = overall_result;
    target.next_string = (char *) (overall_result + *sz);
    copy_hwcaps (&target, glibc_hwcaps_prepend, -1, NULL);
    copy_hwcaps (&target, _dl_hwcaps_subdirs,
		 hwcaps_subdirs_active, glibc_hwcaps_mask);

    /* Append an empty entry for the base directory itself.  */
    target.next_pair->str = target.next_string;
    target.next_pair->len = 0;
  }

  /* The maximum string length.  */
  *max_capstrlen = hwcaps_counts.maximum_length;

  return overall_result;
}