1 | /* Hardware capability support for run-time dynamic loader. |
2 | Copyright (C) 2012-2016 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 | <http://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 | |
28 | #ifdef _DL_FIRST_PLATFORM |
29 | # define _DL_FIRST_EXTRA (_DL_FIRST_PLATFORM + _DL_PLATFORMS_COUNT) |
30 | #else |
31 | # define _DL_HWCAP_COUNT |
32 | #endif |
33 | |
34 | /* Return an array of useful/necessary hardware capability names. */ |
35 | const struct r_strlenpair * |
36 | internal_function |
37 | _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz, |
38 | size_t *max_capstrlen) |
39 | { |
40 | /* Determine how many important bits are set. */ |
41 | uint64_t masked = GLRO(dl_hwcap) & GLRO(dl_hwcap_mask); |
42 | size_t cnt = platform != NULL; |
43 | size_t n, m; |
44 | size_t total; |
45 | struct r_strlenpair *result; |
46 | struct r_strlenpair *rp; |
47 | char *cp; |
48 | |
49 | /* Count the number of bits set in the masked value. */ |
50 | for (n = 0; (~((1ULL << n) - 1) & masked) != 0; ++n) |
51 | if ((masked & (1ULL << n)) != 0) |
52 | ++cnt; |
53 | |
54 | #ifdef NEED_DL_SYSINFO_DSO |
55 | /* The system-supplied DSO can contain a note of type 2, vendor "GNU". |
56 | This gives us a list of names to treat as fake hwcap bits. */ |
57 | |
58 | const char *dsocaps = NULL; |
59 | size_t dsocapslen = 0; |
60 | if (GLRO(dl_sysinfo_map) != NULL) |
61 | { |
62 | const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr; |
63 | const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum; |
64 | for (uint_fast16_t i = 0; i < phnum; ++i) |
65 | if (phdr[i].p_type == PT_NOTE) |
66 | { |
67 | const ElfW(Addr) start = (phdr[i].p_vaddr |
68 | + GLRO(dl_sysinfo_map)->l_addr); |
69 | /* The standard ELF note layout is exactly as the anonymous struct. |
70 | The next element is a variable length vendor name of length |
71 | VENDORLEN (with a real length rounded to ElfW(Word)), followed |
72 | by the data of length DATALEN (with a real length rounded to |
73 | ElfW(Word)). */ |
74 | const struct |
75 | { |
76 | ElfW(Word) vendorlen; |
77 | ElfW(Word) datalen; |
78 | ElfW(Word) type; |
79 | } *note = (const void *) start; |
80 | while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz) |
81 | { |
82 | #define ROUND(len) (((len) + sizeof (ElfW(Word)) - 1) & -sizeof (ElfW(Word))) |
83 | /* The layout of the type 2, vendor "GNU" note is as follows: |
84 | .long <Number of capabilities enabled by this note> |
85 | .long <Capabilities mask> (as mask >> _DL_FIRST_EXTRA). |
86 | .byte <The bit number for the next capability> |
87 | .asciz <The name of the capability>. */ |
88 | if (note->type == NT_GNU_HWCAP |
89 | && note->vendorlen == sizeof "GNU" |
90 | && !memcmp ((note + 1), "GNU" , sizeof "GNU" ) |
91 | && note->datalen > 2 * sizeof (ElfW(Word)) + 2) |
92 | { |
93 | const ElfW(Word) *p = ((const void *) (note + 1) |
94 | + ROUND (sizeof "GNU" )); |
95 | cnt += *p++; |
96 | ++p; /* Skip mask word. */ |
97 | dsocaps = (const char *) p; /* Pseudo-string "<b>name" */ |
98 | dsocapslen = note->datalen - sizeof *p * 2; |
99 | break; |
100 | } |
101 | note = ((const void *) (note + 1) |
102 | + ROUND (note->vendorlen) + ROUND (note->datalen)); |
103 | #undef ROUND |
104 | } |
105 | if (dsocaps != NULL) |
106 | break; |
107 | } |
108 | } |
109 | #endif |
110 | |
111 | /* For TLS enabled builds always add 'tls'. */ |
112 | ++cnt; |
113 | |
114 | /* Create temporary data structure to generate result table. */ |
115 | struct r_strlenpair temp[cnt]; |
116 | m = 0; |
117 | #ifdef NEED_DL_SYSINFO_DSO |
118 | if (dsocaps != NULL) |
119 | { |
120 | /* dsocaps points to the .asciz string, and -1 points to the mask |
121 | .long just before the string. */ |
122 | const ElfW(Word) mask = ((const ElfW(Word) *) dsocaps)[-1]; |
123 | GLRO(dl_hwcap) |= (uint64_t) mask << _DL_FIRST_EXTRA; |
124 | /* Note that we add the dsocaps to the set already chosen by the |
125 | LD_HWCAP_MASK environment variable (or default HWCAP_IMPORTANT). |
126 | So there is no way to request ignoring an OS-supplied dsocap |
127 | string and bit like you can ignore an OS-supplied HWCAP bit. */ |
128 | GLRO(dl_hwcap_mask) |= (uint64_t) mask << _DL_FIRST_EXTRA; |
129 | size_t len; |
130 | for (const char *p = dsocaps; p < dsocaps + dsocapslen; p += len + 1) |
131 | { |
132 | uint_fast8_t bit = *p++; |
133 | len = strlen (p); |
134 | |
135 | /* Skip entries that are not enabled in the mask word. */ |
136 | if (__glibc_likely (mask & ((ElfW(Word)) 1 << bit))) |
137 | { |
138 | temp[m].str = p; |
139 | temp[m].len = len; |
140 | ++m; |
141 | } |
142 | else |
143 | --cnt; |
144 | } |
145 | } |
146 | #endif |
147 | for (n = 0; masked != 0; ++n) |
148 | if ((masked & (1ULL << n)) != 0) |
149 | { |
150 | temp[m].str = _dl_hwcap_string (n); |
151 | temp[m].len = strlen (temp[m].str); |
152 | masked ^= 1ULL << n; |
153 | ++m; |
154 | } |
155 | if (platform != NULL) |
156 | { |
157 | temp[m].str = platform; |
158 | temp[m].len = platform_len; |
159 | ++m; |
160 | } |
161 | |
162 | temp[m].str = "tls" ; |
163 | temp[m].len = 3; |
164 | ++m; |
165 | |
166 | assert (m == cnt); |
167 | |
168 | /* Determine the total size of all strings together. */ |
169 | if (cnt == 1) |
170 | total = temp[0].len + 1; |
171 | else |
172 | { |
173 | total = temp[0].len + temp[cnt - 1].len + 2; |
174 | if (cnt > 2) |
175 | { |
176 | total <<= 1; |
177 | for (n = 1; n + 1 < cnt; ++n) |
178 | total += temp[n].len + 1; |
179 | if (cnt > 3 |
180 | && (cnt >= sizeof (size_t) * 8 |
181 | || total + (sizeof (*result) << 3) |
182 | >= (1UL << (sizeof (size_t) * 8 - cnt + 3)))) |
183 | _dl_signal_error (ENOMEM, NULL, NULL, |
184 | N_("cannot create capability list" )); |
185 | |
186 | total <<= cnt - 3; |
187 | } |
188 | } |
189 | |
190 | /* The result structure: we use a very compressed way to store the |
191 | various combinations of capability names. */ |
192 | *sz = 1 << cnt; |
193 | result = (struct r_strlenpair *) malloc (*sz * sizeof (*result) + total); |
194 | if (result == NULL) |
195 | _dl_signal_error (ENOMEM, NULL, NULL, |
196 | N_("cannot create capability list" )); |
197 | |
198 | if (cnt == 1) |
199 | { |
200 | result[0].str = (char *) (result + *sz); |
201 | result[0].len = temp[0].len + 1; |
202 | result[1].str = (char *) (result + *sz); |
203 | result[1].len = 0; |
204 | cp = __mempcpy ((char *) (result + *sz), temp[0].str, temp[0].len); |
205 | *cp = '/'; |
206 | *sz = 2; |
207 | *max_capstrlen = result[0].len; |
208 | |
209 | return result; |
210 | } |
211 | |
212 | /* Fill in the information. This follows the following scheme |
213 | (indices from TEMP for four strings): |
214 | entry #0: 0, 1, 2, 3 binary: 1111 |
215 | #1: 0, 1, 3 1101 |
216 | #2: 0, 2, 3 1011 |
217 | #3: 0, 3 1001 |
218 | This allows the representation of all possible combinations of |
219 | capability names in the string. First generate the strings. */ |
220 | result[1].str = result[0].str = cp = (char *) (result + *sz); |
221 | #define add(idx) \ |
222 | cp = __mempcpy (__mempcpy (cp, temp[idx].str, temp[idx].len), "/", 1); |
223 | if (cnt == 2) |
224 | { |
225 | add (1); |
226 | add (0); |
227 | } |
228 | else |
229 | { |
230 | n = 1 << (cnt - 1); |
231 | do |
232 | { |
233 | n -= 2; |
234 | |
235 | /* We always add the last string. */ |
236 | add (cnt - 1); |
237 | |
238 | /* Add the strings which have the bit set in N. */ |
239 | for (m = cnt - 2; m > 0; --m) |
240 | if ((n & (1 << m)) != 0) |
241 | add (m); |
242 | |
243 | /* Always add the first string. */ |
244 | add (0); |
245 | } |
246 | while (n != 0); |
247 | } |
248 | #undef add |
249 | |
250 | /* Now we are ready to install the string pointers and length. */ |
251 | for (n = 0; n < (1UL << cnt); ++n) |
252 | result[n].len = 0; |
253 | n = cnt; |
254 | do |
255 | { |
256 | size_t mask = 1 << --n; |
257 | |
258 | rp = result; |
259 | for (m = 1 << cnt; m > 0; ++rp) |
260 | if ((--m & mask) != 0) |
261 | rp->len += temp[n].len + 1; |
262 | } |
263 | while (n != 0); |
264 | |
265 | /* The first half of the strings all include the first string. */ |
266 | n = (1 << cnt) - 2; |
267 | rp = &result[2]; |
268 | while (n != (1UL << (cnt - 1))) |
269 | { |
270 | if ((--n & 1) != 0) |
271 | rp[0].str = rp[-2].str + rp[-2].len; |
272 | else |
273 | rp[0].str = rp[-1].str; |
274 | ++rp; |
275 | } |
276 | |
277 | /* The second half starts right after the first part of the string of |
278 | the corresponding entry in the first half. */ |
279 | do |
280 | { |
281 | rp[0].str = rp[-(1 << (cnt - 1))].str + temp[cnt - 1].len + 1; |
282 | ++rp; |
283 | } |
284 | while (--n != 0); |
285 | |
286 | /* The maximum string length. */ |
287 | *max_capstrlen = result[0].len; |
288 | |
289 | return result; |
290 | } |
291 | |