1 | /* Hardware capability support for run-time dynamic loader. |
2 | Copyright (C) 2012-2019 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 | #include <dl-hwcaps.h> |
28 | |
29 | #ifdef _DL_FIRST_PLATFORM |
30 | # define (_DL_FIRST_PLATFORM + _DL_PLATFORMS_COUNT) |
31 | #else |
32 | # define _DL_FIRST_EXTRA _DL_HWCAP_COUNT |
33 | #endif |
34 | |
35 | /* Return an array of useful/necessary hardware capability names. */ |
36 | const struct r_strlenpair * |
37 | _dl_important_hwcaps (const char *platform, size_t platform_len, size_t *sz, |
38 | size_t *max_capstrlen) |
39 | { |
40 | uint64_t hwcap_mask = GET_HWCAP_MASK(); |
41 | /* Determine how many important bits are set. */ |
42 | uint64_t masked = GLRO(dl_hwcap) & hwcap_mask; |
43 | size_t cnt = platform != NULL; |
44 | size_t n, m; |
45 | size_t total; |
46 | struct r_strlenpair *result; |
47 | struct r_strlenpair *rp; |
48 | char *cp; |
49 | |
50 | /* Count the number of bits set in the masked value. */ |
51 | for (n = 0; (~((1ULL << n) - 1) & masked) != 0; ++n) |
52 | if ((masked & (1ULL << n)) != 0) |
53 | ++cnt; |
54 | |
55 | #ifdef NEED_DL_SYSINFO_DSO |
56 | /* The system-supplied DSO can contain a note of type 2, vendor "GNU". |
57 | This gives us a list of names to treat as fake hwcap bits. */ |
58 | |
59 | const char *dsocaps = NULL; |
60 | size_t dsocapslen = 0; |
61 | if (GLRO(dl_sysinfo_map) != NULL) |
62 | { |
63 | const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr; |
64 | const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum; |
65 | for (uint_fast16_t i = 0; i < phnum; ++i) |
66 | if (phdr[i].p_type == PT_NOTE) |
67 | { |
68 | const ElfW(Addr) start = (phdr[i].p_vaddr |
69 | + GLRO(dl_sysinfo_map)->l_addr); |
70 | /* NB: Some PT_NOTE segment may have alignment value of 0 |
71 | or 1. gABI specifies that PT_NOTE segments should be |
72 | aligned to 4 bytes in 32-bit objects and to 8 bytes in |
73 | 64-bit objects. As a Linux extension, we also support |
74 | 4 byte alignment in 64-bit objects. If p_align is less |
75 | than 4, we treate alignment as 4 bytes since some note |
76 | segments have 0 or 1 byte alignment. */ |
77 | ElfW(Addr) align = phdr[i].p_align; |
78 | if (align < 4) |
79 | align = 4; |
80 | else if (align != 4 && align != 8) |
81 | continue; |
82 | /* The standard ELF note layout is exactly as the anonymous struct. |
83 | The next element is a variable length vendor name of length |
84 | VENDORLEN (with a real length rounded to ElfW(Word)), followed |
85 | by the data of length DATALEN (with a real length rounded to |
86 | ElfW(Word)). */ |
87 | const struct |
88 | { |
89 | ElfW(Word) vendorlen; |
90 | ElfW(Word) datalen; |
91 | ElfW(Word) type; |
92 | } *note = (const void *) start; |
93 | while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz) |
94 | { |
95 | /* The layout of the type 2, vendor "GNU" note is as follows: |
96 | .long <Number of capabilities enabled by this note> |
97 | .long <Capabilities mask> (as mask >> _DL_FIRST_EXTRA). |
98 | .byte <The bit number for the next capability> |
99 | .asciz <The name of the capability>. */ |
100 | if (note->type == NT_GNU_HWCAP |
101 | && note->vendorlen == sizeof "GNU" |
102 | && !memcmp ((note + 1), "GNU" , sizeof "GNU" ) |
103 | && note->datalen > 2 * sizeof (ElfW(Word)) + 2) |
104 | { |
105 | const ElfW(Word) *p |
106 | = ((const void *) note |
107 | + ELF_NOTE_DESC_OFFSET (sizeof "GNU" , align)); |
108 | cnt += *p++; |
109 | ++p; /* Skip mask word. */ |
110 | dsocaps = (const char *) p; /* Pseudo-string "<b>name" */ |
111 | dsocapslen = note->datalen - sizeof *p * 2; |
112 | break; |
113 | } |
114 | note = ((const void *) note |
115 | + ELF_NOTE_NEXT_OFFSET (note->vendorlen, |
116 | note->datalen, align)); |
117 | } |
118 | if (dsocaps != NULL) |
119 | break; |
120 | } |
121 | } |
122 | #endif |
123 | |
124 | /* For TLS enabled builds always add 'tls'. */ |
125 | ++cnt; |
126 | |
127 | /* Create temporary data structure to generate result table. */ |
128 | struct r_strlenpair temp[cnt]; |
129 | m = 0; |
130 | #ifdef NEED_DL_SYSINFO_DSO |
131 | if (dsocaps != NULL) |
132 | { |
133 | /* dsocaps points to the .asciz string, and -1 points to the mask |
134 | .long just before the string. */ |
135 | const ElfW(Word) mask = ((const ElfW(Word) *) dsocaps)[-1]; |
136 | GLRO(dl_hwcap) |= (uint64_t) mask << _DL_FIRST_EXTRA; |
137 | /* Note that we add the dsocaps to the set already chosen by the |
138 | LD_HWCAP_MASK environment variable (or default HWCAP_IMPORTANT). |
139 | So there is no way to request ignoring an OS-supplied dsocap |
140 | string and bit like you can ignore an OS-supplied HWCAP bit. */ |
141 | hwcap_mask |= (uint64_t) mask << _DL_FIRST_EXTRA; |
142 | #if HAVE_TUNABLES |
143 | TUNABLE_SET (glibc, cpu, hwcap_mask, uint64_t, hwcap_mask); |
144 | #else |
145 | GLRO(dl_hwcap_mask) = hwcap_mask; |
146 | #endif |
147 | size_t len; |
148 | for (const char *p = dsocaps; p < dsocaps + dsocapslen; p += len + 1) |
149 | { |
150 | uint_fast8_t bit = *p++; |
151 | len = strlen (p); |
152 | |
153 | /* Skip entries that are not enabled in the mask word. */ |
154 | if (__glibc_likely (mask & ((ElfW(Word)) 1 << bit))) |
155 | { |
156 | temp[m].str = p; |
157 | temp[m].len = len; |
158 | ++m; |
159 | } |
160 | else |
161 | --cnt; |
162 | } |
163 | } |
164 | #endif |
165 | for (n = 0; masked != 0; ++n) |
166 | if ((masked & (1ULL << n)) != 0) |
167 | { |
168 | temp[m].str = _dl_hwcap_string (n); |
169 | temp[m].len = strlen (temp[m].str); |
170 | masked ^= 1ULL << n; |
171 | ++m; |
172 | } |
173 | if (platform != NULL) |
174 | { |
175 | temp[m].str = platform; |
176 | temp[m].len = platform_len; |
177 | ++m; |
178 | } |
179 | |
180 | temp[m].str = "tls" ; |
181 | temp[m].len = 3; |
182 | ++m; |
183 | |
184 | assert (m == cnt); |
185 | |
186 | /* Determine the total size of all strings together. */ |
187 | if (cnt == 1) |
188 | total = temp[0].len + 1; |
189 | else |
190 | { |
191 | total = temp[0].len + temp[cnt - 1].len + 2; |
192 | if (cnt > 2) |
193 | { |
194 | total <<= 1; |
195 | for (n = 1; n + 1 < cnt; ++n) |
196 | total += temp[n].len + 1; |
197 | if (cnt > 3 |
198 | && (cnt >= sizeof (size_t) * 8 |
199 | || total + (sizeof (*result) << 3) |
200 | >= (1UL << (sizeof (size_t) * 8 - cnt + 3)))) |
201 | _dl_signal_error (ENOMEM, NULL, NULL, |
202 | N_("cannot create capability list" )); |
203 | |
204 | total <<= cnt - 3; |
205 | } |
206 | } |
207 | |
208 | /* The result structure: we use a very compressed way to store the |
209 | various combinations of capability names. */ |
210 | *sz = 1 << cnt; |
211 | result = (struct r_strlenpair *) malloc (*sz * sizeof (*result) + total); |
212 | if (result == NULL) |
213 | _dl_signal_error (ENOMEM, NULL, NULL, |
214 | N_("cannot create capability list" )); |
215 | |
216 | if (cnt == 1) |
217 | { |
218 | result[0].str = (char *) (result + *sz); |
219 | result[0].len = temp[0].len + 1; |
220 | result[1].str = (char *) (result + *sz); |
221 | result[1].len = 0; |
222 | cp = __mempcpy ((char *) (result + *sz), temp[0].str, temp[0].len); |
223 | *cp = '/'; |
224 | *sz = 2; |
225 | *max_capstrlen = result[0].len; |
226 | |
227 | return result; |
228 | } |
229 | |
230 | /* Fill in the information. This follows the following scheme |
231 | (indices from TEMP for four strings): |
232 | entry #0: 0, 1, 2, 3 binary: 1111 |
233 | #1: 0, 1, 3 1101 |
234 | #2: 0, 2, 3 1011 |
235 | #3: 0, 3 1001 |
236 | This allows the representation of all possible combinations of |
237 | capability names in the string. First generate the strings. */ |
238 | result[1].str = result[0].str = cp = (char *) (result + *sz); |
239 | #define add(idx) \ |
240 | cp = __mempcpy (__mempcpy (cp, temp[idx].str, temp[idx].len), "/", 1); |
241 | if (cnt == 2) |
242 | { |
243 | add (1); |
244 | add (0); |
245 | } |
246 | else |
247 | { |
248 | n = 1 << (cnt - 1); |
249 | do |
250 | { |
251 | n -= 2; |
252 | |
253 | /* We always add the last string. */ |
254 | add (cnt - 1); |
255 | |
256 | /* Add the strings which have the bit set in N. */ |
257 | for (m = cnt - 2; m > 0; --m) |
258 | if ((n & (1 << m)) != 0) |
259 | add (m); |
260 | |
261 | /* Always add the first string. */ |
262 | add (0); |
263 | } |
264 | while (n != 0); |
265 | } |
266 | #undef add |
267 | |
268 | /* Now we are ready to install the string pointers and length. */ |
269 | for (n = 0; n < (1UL << cnt); ++n) |
270 | result[n].len = 0; |
271 | n = cnt; |
272 | do |
273 | { |
274 | size_t mask = 1 << --n; |
275 | |
276 | rp = result; |
277 | for (m = 1 << cnt; m > 0; ++rp) |
278 | if ((--m & mask) != 0) |
279 | rp->len += temp[n].len + 1; |
280 | } |
281 | while (n != 0); |
282 | |
283 | /* The first half of the strings all include the first string. */ |
284 | n = (1 << cnt) - 2; |
285 | rp = &result[2]; |
286 | while (n != (1UL << (cnt - 1))) |
287 | { |
288 | if ((--n & 1) != 0) |
289 | rp[0].str = rp[-2].str + rp[-2].len; |
290 | else |
291 | rp[0].str = rp[-1].str; |
292 | ++rp; |
293 | } |
294 | |
295 | /* The second half starts right after the first part of the string of |
296 | the corresponding entry in the first half. */ |
297 | do |
298 | { |
299 | rp[0].str = rp[-(1 << (cnt - 1))].str + temp[cnt - 1].len + 1; |
300 | ++rp; |
301 | } |
302 | while (--n != 0); |
303 | |
304 | /* The maximum string length. */ |
305 | *max_capstrlen = result[0].len; |
306 | |
307 | return result; |
308 | } |
309 | |