1 /* Operating system support for run-time dynamic linker. Generic Unix version.
2 Copyright (C) 1995-2021 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 /* We conditionalize the whole of this file rather than simply eliding it
20 from the static build, because other sysdeps/ versions of this file
21 might define things needed by a static build. */
22
23 #ifdef SHARED
24
25 #include <assert.h>
26 #include <elf.h>
27 #include <errno.h>
28 #include <fcntl.h>
29 #include <libintl.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #include <unistd.h>
33 #include <sys/types.h>
34 #include <sys/stat.h>
35 #include <sys/mman.h>
36 #include <ldsodefs.h>
37 #include <_itoa.h>
38 #include <fpu_control.h>
39
40 #include <entry.h>
41 #include <dl-machine.h>
42 #include <dl-procinfo.h>
43 #include <dl-osinfo.h>
44 #include <libc-internal.h>
45 #include <tls.h>
46
47 #include <dl-tunables.h>
48 #include <dl-auxv.h>
49 #include <dl-hwcap-check.h>
50
51 extern char **_environ attribute_hidden;
52 extern char _end[] attribute_hidden;
53
54 /* Protect SUID program against misuse of file descriptors. */
55 extern void __libc_check_standard_fds (void);
56
57 int __libc_enable_secure attribute_relro = 0;
58 rtld_hidden_data_def (__libc_enable_secure)
59 /* This variable contains the lowest stack address ever used. */
60 void *__libc_stack_end attribute_relro = NULL;
61 rtld_hidden_data_def(__libc_stack_end)
62 void *_dl_random attribute_relro = NULL;
63
64 #ifndef DL_FIND_ARG_COMPONENTS
65 # define DL_FIND_ARG_COMPONENTS(cookie, argc, argv, envp, auxp) \
66 do { \
67 void **_tmp; \
68 (argc) = *(long int *) cookie; \
69 (argv) = (char **) ((long int *) cookie + 1); \
70 (envp) = (argv) + (argc) + 1; \
71 for (_tmp = (void **) (envp); *_tmp; ++_tmp) \
72 continue; \
73 (auxp) = (void *) ++_tmp; \
74 } while (0)
75 #endif
76
77 #ifndef DL_STACK_END
78 # define DL_STACK_END(cookie) ((void *) (cookie))
79 #endif
80
81 ElfW(Addr)
_dl_sysdep_start(void ** start_argptr,void (* dl_main)(const ElfW (Phdr)* phdr,ElfW (Word)phnum,ElfW (Addr)* user_entry,ElfW (auxv_t)* auxv))82 _dl_sysdep_start (void **start_argptr,
83 void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
84 ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
85 {
86 const ElfW(Phdr) *phdr = NULL;
87 ElfW(Word) phnum = 0;
88 ElfW(Addr) user_entry;
89 ElfW(auxv_t) *av;
90 #ifdef HAVE_AUX_SECURE
91 # define set_seen(tag) (tag) /* Evaluate for the side effects. */
92 # define set_seen_secure() ((void) 0)
93 #else
94 uid_t uid = 0;
95 gid_t gid = 0;
96 unsigned int seen = 0;
97 # define set_seen_secure() (seen = -1)
98 # ifdef HAVE_AUX_XID
99 # define set_seen(tag) (tag) /* Evaluate for the side effects. */
100 # else
101 # define M(type) (1 << (type))
102 # define set_seen(tag) seen |= M ((tag)->a_type)
103 # endif
104 #endif
105 #ifdef NEED_DL_SYSINFO
106 uintptr_t new_sysinfo = 0;
107 #endif
108
109 __libc_stack_end = DL_STACK_END (start_argptr);
110 DL_FIND_ARG_COMPONENTS (start_argptr, _dl_argc, _dl_argv, _environ,
111 GLRO(dl_auxv));
112
113 user_entry = (ElfW(Addr)) ENTRY_POINT;
114 GLRO(dl_platform) = NULL; /* Default to nothing known about the platform. */
115
116 /* NB: Default to a constant CONSTANT_MINSIGSTKSZ. */
117 _Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ),
118 "CONSTANT_MINSIGSTKSZ is constant");
119 GLRO(dl_minsigstacksize) = CONSTANT_MINSIGSTKSZ;
120
121 for (av = GLRO(dl_auxv); av->a_type != AT_NULL; set_seen (av++))
122 switch (av->a_type)
123 {
124 case AT_PHDR:
125 phdr = (void *) av->a_un.a_val;
126 break;
127 case AT_PHNUM:
128 phnum = av->a_un.a_val;
129 break;
130 case AT_PAGESZ:
131 GLRO(dl_pagesize) = av->a_un.a_val;
132 break;
133 case AT_ENTRY:
134 user_entry = av->a_un.a_val;
135 break;
136 #ifndef HAVE_AUX_SECURE
137 case AT_UID:
138 case AT_EUID:
139 uid ^= av->a_un.a_val;
140 break;
141 case AT_GID:
142 case AT_EGID:
143 gid ^= av->a_un.a_val;
144 break;
145 #endif
146 case AT_SECURE:
147 #ifndef HAVE_AUX_SECURE
148 seen = -1;
149 #endif
150 __libc_enable_secure = av->a_un.a_val;
151 break;
152 case AT_PLATFORM:
153 GLRO(dl_platform) = (void *) av->a_un.a_val;
154 break;
155 case AT_HWCAP:
156 GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
157 break;
158 case AT_HWCAP2:
159 GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
160 break;
161 case AT_CLKTCK:
162 GLRO(dl_clktck) = av->a_un.a_val;
163 break;
164 case AT_FPUCW:
165 GLRO(dl_fpu_control) = av->a_un.a_val;
166 break;
167 #ifdef NEED_DL_SYSINFO
168 case AT_SYSINFO:
169 new_sysinfo = av->a_un.a_val;
170 break;
171 #endif
172 #ifdef NEED_DL_SYSINFO_DSO
173 case AT_SYSINFO_EHDR:
174 GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
175 break;
176 #endif
177 case AT_RANDOM:
178 _dl_random = (void *) av->a_un.a_val;
179 break;
180 case AT_MINSIGSTKSZ:
181 GLRO(dl_minsigstacksize) = av->a_un.a_val;
182 break;
183 DL_PLATFORM_AUXV
184 }
185
186 dl_hwcap_check ();
187
188 #ifndef HAVE_AUX_SECURE
189 if (seen != -1)
190 {
191 /* Fill in the values we have not gotten from the kernel through the
192 auxiliary vector. */
193 # ifndef HAVE_AUX_XID
194 # define SEE(UID, var, uid) \
195 if ((seen & M (AT_##UID)) == 0) var ^= __get##uid ()
196 SEE (UID, uid, uid);
197 SEE (EUID, uid, euid);
198 SEE (GID, gid, gid);
199 SEE (EGID, gid, egid);
200 # endif
201
202 /* If one of the two pairs of IDs does not match this is a setuid
203 or setgid run. */
204 __libc_enable_secure = uid | gid;
205 }
206 #endif
207
208 #ifndef HAVE_AUX_PAGESIZE
209 if (GLRO(dl_pagesize) == 0)
210 GLRO(dl_pagesize) = __getpagesize ();
211 #endif
212
213 #ifdef NEED_DL_SYSINFO
214 if (new_sysinfo != 0)
215 {
216 # ifdef NEED_DL_SYSINFO_DSO
217 /* Only set the sysinfo value if we also have the vsyscall DSO. */
218 if (GLRO(dl_sysinfo_dso) != 0)
219 # endif
220 GLRO(dl_sysinfo) = new_sysinfo;
221 }
222 #endif
223
224 __tunables_init (_environ);
225
226 /* Initialize DSO sorting algorithm after tunables. */
227 _dl_sort_maps_init ();
228
229 #ifdef DL_SYSDEP_INIT
230 DL_SYSDEP_INIT;
231 #endif
232
233 #ifdef DL_PLATFORM_INIT
234 DL_PLATFORM_INIT;
235 #endif
236
237 /* Determine the length of the platform name. */
238 if (GLRO(dl_platform) != NULL)
239 GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
240
241 if (__sbrk (0) == _end)
242 /* The dynamic linker was run as a program, and so the initial break
243 starts just after our bss, at &_end. The malloc in dl-minimal.c
244 will consume the rest of this page, so tell the kernel to move the
245 break up that far. When the user program examines its break, it
246 will see this new value and not clobber our data. */
247 __sbrk (GLRO(dl_pagesize)
248 - ((_end - (char *) 0) & (GLRO(dl_pagesize) - 1)));
249
250 /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
251 allocated. If necessary we are doing it ourself. If it is not
252 possible we stop the program. */
253 if (__builtin_expect (__libc_enable_secure, 0))
254 __libc_check_standard_fds ();
255
256 (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
257 return user_entry;
258 }
259
260 void
_dl_sysdep_start_cleanup(void)261 _dl_sysdep_start_cleanup (void)
262 {
263 }
264
265 void
_dl_show_auxv(void)266 _dl_show_auxv (void)
267 {
268 char buf[64];
269 ElfW(auxv_t) *av;
270
271 /* Terminate string. */
272 buf[63] = '\0';
273
274 /* The following code assumes that the AT_* values are encoded
275 starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
276 close by (otherwise the array will be too large). In case we have
277 to support a platform where these requirements are not fulfilled
278 some alternative implementation has to be used. */
279 for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
280 {
281 static const struct
282 {
283 const char label[22];
284 enum { unknown = 0, dec, hex, str, ignore } form : 8;
285 } auxvars[] =
286 {
287 [AT_EXECFD - 2] = { "EXECFD: ", dec },
288 [AT_EXECFN - 2] = { "EXECFN: ", str },
289 [AT_PHDR - 2] = { "PHDR: 0x", hex },
290 [AT_PHENT - 2] = { "PHENT: ", dec },
291 [AT_PHNUM - 2] = { "PHNUM: ", dec },
292 [AT_PAGESZ - 2] = { "PAGESZ: ", dec },
293 [AT_BASE - 2] = { "BASE: 0x", hex },
294 [AT_FLAGS - 2] = { "FLAGS: 0x", hex },
295 [AT_ENTRY - 2] = { "ENTRY: 0x", hex },
296 [AT_NOTELF - 2] = { "NOTELF: ", hex },
297 [AT_UID - 2] = { "UID: ", dec },
298 [AT_EUID - 2] = { "EUID: ", dec },
299 [AT_GID - 2] = { "GID: ", dec },
300 [AT_EGID - 2] = { "EGID: ", dec },
301 [AT_PLATFORM - 2] = { "PLATFORM: ", str },
302 [AT_HWCAP - 2] = { "HWCAP: ", hex },
303 [AT_CLKTCK - 2] = { "CLKTCK: ", dec },
304 [AT_FPUCW - 2] = { "FPUCW: ", hex },
305 [AT_DCACHEBSIZE - 2] = { "DCACHEBSIZE: 0x", hex },
306 [AT_ICACHEBSIZE - 2] = { "ICACHEBSIZE: 0x", hex },
307 [AT_UCACHEBSIZE - 2] = { "UCACHEBSIZE: 0x", hex },
308 [AT_IGNOREPPC - 2] = { "IGNOREPPC", ignore },
309 [AT_SECURE - 2] = { "SECURE: ", dec },
310 [AT_BASE_PLATFORM - 2] = { "BASE_PLATFORM: ", str },
311 [AT_SYSINFO - 2] = { "SYSINFO: 0x", hex },
312 [AT_SYSINFO_EHDR - 2] = { "SYSINFO_EHDR: 0x", hex },
313 [AT_RANDOM - 2] = { "RANDOM: 0x", hex },
314 [AT_HWCAP2 - 2] = { "HWCAP2: 0x", hex },
315 [AT_MINSIGSTKSZ - 2] = { "MINSIGSTKSZ: ", dec },
316 [AT_L1I_CACHESIZE - 2] = { "L1I_CACHESIZE: ", dec },
317 [AT_L1I_CACHEGEOMETRY - 2] = { "L1I_CACHEGEOMETRY: 0x", hex },
318 [AT_L1D_CACHESIZE - 2] = { "L1D_CACHESIZE: ", dec },
319 [AT_L1D_CACHEGEOMETRY - 2] = { "L1D_CACHEGEOMETRY: 0x", hex },
320 [AT_L2_CACHESIZE - 2] = { "L2_CACHESIZE: ", dec },
321 [AT_L2_CACHEGEOMETRY - 2] = { "L2_CACHEGEOMETRY: 0x", hex },
322 [AT_L3_CACHESIZE - 2] = { "L3_CACHESIZE: ", dec },
323 [AT_L3_CACHEGEOMETRY - 2] = { "L3_CACHEGEOMETRY: 0x", hex },
324 };
325 unsigned int idx = (unsigned int) (av->a_type - 2);
326
327 if ((unsigned int) av->a_type < 2u
328 || (idx < sizeof (auxvars) / sizeof (auxvars[0])
329 && auxvars[idx].form == ignore))
330 continue;
331
332 assert (AT_NULL == 0);
333 assert (AT_IGNORE == 1);
334
335 /* Some entries are handled in a special way per platform. */
336 if (_dl_procinfo (av->a_type, av->a_un.a_val) == 0)
337 continue;
338
339 if (idx < sizeof (auxvars) / sizeof (auxvars[0])
340 && auxvars[idx].form != unknown)
341 {
342 const char *val = (char *) av->a_un.a_val;
343
344 if (__builtin_expect (auxvars[idx].form, dec) == dec)
345 val = _itoa ((unsigned long int) av->a_un.a_val,
346 buf + sizeof buf - 1, 10, 0);
347 else if (__builtin_expect (auxvars[idx].form, hex) == hex)
348 val = _itoa ((unsigned long int) av->a_un.a_val,
349 buf + sizeof buf - 1, 16, 0);
350
351 _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
352
353 continue;
354 }
355
356 /* Unknown value: print a generic line. */
357 char buf2[17];
358 buf2[sizeof (buf2) - 1] = '\0';
359 const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
360 buf2 + sizeof buf2 - 1, 16, 0);
361 const char *val = _itoa ((unsigned long int) av->a_type,
362 buf + sizeof buf - 1, 16, 0);
363 _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
364 }
365 }
366
367 #endif
368