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
51extern char **_environ attribute_hidden;
52extern char _end[] attribute_hidden;
53
54/* Protect SUID program against misuse of file descriptors. */
55extern void __libc_check_standard_fds (void);
56
57#ifdef NEED_DL_BASE_ADDR
58ElfW(Addr) _dl_base_addr;
59#endif
60int __libc_enable_secure attribute_relro = 0;
61rtld_hidden_data_def (__libc_enable_secure)
62/* This variable contains the lowest stack address ever used. */
63void *__libc_stack_end attribute_relro = NULL;
64rtld_hidden_data_def(__libc_stack_end)
65void *_dl_random attribute_relro = NULL;
66
67#ifndef DL_FIND_ARG_COMPONENTS
68# define DL_FIND_ARG_COMPONENTS(cookie, argc, argv, envp, auxp) \
69 do { \
70 void **_tmp; \
71 (argc) = *(long int *) cookie; \
72 (argv) = (char **) ((long int *) cookie + 1); \
73 (envp) = (argv) + (argc) + 1; \
74 for (_tmp = (void **) (envp); *_tmp; ++_tmp) \
75 continue; \
76 (auxp) = (void *) ++_tmp; \
77 } while (0)
78#endif
79
80#ifndef DL_STACK_END
81# define DL_STACK_END(cookie) ((void *) (cookie))
82#endif
83
84ElfW(Addr)
85_dl_sysdep_start (void **start_argptr,
86 void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
87 ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
88{
89 const ElfW(Phdr) *phdr = NULL;
90 ElfW(Word) phnum = 0;
91 ElfW(Addr) user_entry;
92 ElfW(auxv_t) *av;
93#ifdef HAVE_AUX_SECURE
94# define set_seen(tag) (tag) /* Evaluate for the side effects. */
95# define set_seen_secure() ((void) 0)
96#else
97 uid_t uid = 0;
98 gid_t gid = 0;
99 unsigned int seen = 0;
100# define set_seen_secure() (seen = -1)
101# ifdef HAVE_AUX_XID
102# define set_seen(tag) (tag) /* Evaluate for the side effects. */
103# else
104# define M(type) (1 << (type))
105# define set_seen(tag) seen |= M ((tag)->a_type)
106# endif
107#endif
108#ifdef NEED_DL_SYSINFO
109 uintptr_t new_sysinfo = 0;
110#endif
111
112 __libc_stack_end = DL_STACK_END (start_argptr);
113 DL_FIND_ARG_COMPONENTS (start_argptr, _dl_argc, _dl_argv, _environ,
114 GLRO(dl_auxv));
115
116 user_entry = (ElfW(Addr)) ENTRY_POINT;
117 GLRO(dl_platform) = NULL; /* Default to nothing known about the platform. */
118
119 /* NB: Default to a constant CONSTANT_MINSIGSTKSZ. */
120 _Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ),
121 "CONSTANT_MINSIGSTKSZ is constant");
122 GLRO(dl_minsigstacksize) = CONSTANT_MINSIGSTKSZ;
123
124 for (av = GLRO(dl_auxv); av->a_type != AT_NULL; set_seen (av++))
125 switch (av->a_type)
126 {
127 case AT_PHDR:
128 phdr = (void *) av->a_un.a_val;
129 break;
130 case AT_PHNUM:
131 phnum = av->a_un.a_val;
132 break;
133 case AT_PAGESZ:
134 GLRO(dl_pagesize) = av->a_un.a_val;
135 break;
136 case AT_ENTRY:
137 user_entry = av->a_un.a_val;
138 break;
139#ifdef NEED_DL_BASE_ADDR
140 case AT_BASE:
141 _dl_base_addr = av->a_un.a_val;
142 break;
143#endif
144#ifndef HAVE_AUX_SECURE
145 case AT_UID:
146 case AT_EUID:
147 uid ^= av->a_un.a_val;
148 break;
149 case AT_GID:
150 case AT_EGID:
151 gid ^= av->a_un.a_val;
152 break;
153#endif
154 case AT_SECURE:
155#ifndef HAVE_AUX_SECURE
156 seen = -1;
157#endif
158 __libc_enable_secure = av->a_un.a_val;
159 break;
160 case AT_PLATFORM:
161 GLRO(dl_platform) = (void *) av->a_un.a_val;
162 break;
163 case AT_HWCAP:
164 GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
165 break;
166 case AT_HWCAP2:
167 GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
168 break;
169 case AT_CLKTCK:
170 GLRO(dl_clktck) = av->a_un.a_val;
171 break;
172 case AT_FPUCW:
173 GLRO(dl_fpu_control) = av->a_un.a_val;
174 break;
175#ifdef NEED_DL_SYSINFO
176 case AT_SYSINFO:
177 new_sysinfo = av->a_un.a_val;
178 break;
179#endif
180#ifdef NEED_DL_SYSINFO_DSO
181 case AT_SYSINFO_EHDR:
182 GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
183 break;
184#endif
185 case AT_RANDOM:
186 _dl_random = (void *) av->a_un.a_val;
187 break;
188 case AT_MINSIGSTKSZ:
189 GLRO(dl_minsigstacksize) = av->a_un.a_val;
190 break;
191 DL_PLATFORM_AUXV
192 }
193
194 dl_hwcap_check ();
195
196#ifndef HAVE_AUX_SECURE
197 if (seen != -1)
198 {
199 /* Fill in the values we have not gotten from the kernel through the
200 auxiliary vector. */
201# ifndef HAVE_AUX_XID
202# define SEE(UID, var, uid) \
203 if ((seen & M (AT_##UID)) == 0) var ^= __get##uid ()
204 SEE (UID, uid, uid);
205 SEE (EUID, uid, euid);
206 SEE (GID, gid, gid);
207 SEE (EGID, gid, egid);
208# endif
209
210 /* If one of the two pairs of IDs does not match this is a setuid
211 or setgid run. */
212 __libc_enable_secure = uid | gid;
213 }
214#endif
215
216#ifndef HAVE_AUX_PAGESIZE
217 if (GLRO(dl_pagesize) == 0)
218 GLRO(dl_pagesize) = __getpagesize ();
219#endif
220
221#ifdef NEED_DL_SYSINFO
222 if (new_sysinfo != 0)
223 {
224# ifdef NEED_DL_SYSINFO_DSO
225 /* Only set the sysinfo value if we also have the vsyscall DSO. */
226 if (GLRO(dl_sysinfo_dso) != 0)
227# endif
228 GLRO(dl_sysinfo) = new_sysinfo;
229 }
230#endif
231
232 __tunables_init (_environ);
233
234#ifdef DL_SYSDEP_INIT
235 DL_SYSDEP_INIT;
236#endif
237
238#ifdef DL_PLATFORM_INIT
239 DL_PLATFORM_INIT;
240#endif
241
242 /* Determine the length of the platform name. */
243 if (GLRO(dl_platform) != NULL)
244 GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
245
246 if (__sbrk (0) == _end)
247 /* The dynamic linker was run as a program, and so the initial break
248 starts just after our bss, at &_end. The malloc in dl-minimal.c
249 will consume the rest of this page, so tell the kernel to move the
250 break up that far. When the user program examines its break, it
251 will see this new value and not clobber our data. */
252 __sbrk (GLRO(dl_pagesize)
253 - ((_end - (char *) 0) & (GLRO(dl_pagesize) - 1)));
254
255 /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
256 allocated. If necessary we are doing it ourself. If it is not
257 possible we stop the program. */
258 if (__builtin_expect (__libc_enable_secure, 0))
259 __libc_check_standard_fds ();
260
261 (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
262 return user_entry;
263}
264
265void
266_dl_sysdep_start_cleanup (void)
267{
268}
269
270void
271_dl_show_auxv (void)
272{
273 char buf[64];
274 ElfW(auxv_t) *av;
275
276 /* Terminate string. */
277 buf[63] = '\0';
278
279 /* The following code assumes that the AT_* values are encoded
280 starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
281 close by (otherwise the array will be too large). In case we have
282 to support a platform where these requirements are not fulfilled
283 some alternative implementation has to be used. */
284 for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
285 {
286 static const struct
287 {
288 const char label[22];
289 enum { unknown = 0, dec, hex, str, ignore } form : 8;
290 } auxvars[] =
291 {
292 [AT_EXECFD - 2] = { "EXECFD: ", dec },
293 [AT_EXECFN - 2] = { "EXECFN: ", str },
294 [AT_PHDR - 2] = { "PHDR: 0x", hex },
295 [AT_PHENT - 2] = { "PHENT: ", dec },
296 [AT_PHNUM - 2] = { "PHNUM: ", dec },
297 [AT_PAGESZ - 2] = { "PAGESZ: ", dec },
298 [AT_BASE - 2] = { "BASE: 0x", hex },
299 [AT_FLAGS - 2] = { "FLAGS: 0x", hex },
300 [AT_ENTRY - 2] = { "ENTRY: 0x", hex },
301 [AT_NOTELF - 2] = { "NOTELF: ", hex },
302 [AT_UID - 2] = { "UID: ", dec },
303 [AT_EUID - 2] = { "EUID: ", dec },
304 [AT_GID - 2] = { "GID: ", dec },
305 [AT_EGID - 2] = { "EGID: ", dec },
306 [AT_PLATFORM - 2] = { "PLATFORM: ", str },
307 [AT_HWCAP - 2] = { "HWCAP: ", hex },
308 [AT_CLKTCK - 2] = { "CLKTCK: ", dec },
309 [AT_FPUCW - 2] = { "FPUCW: ", hex },
310 [AT_DCACHEBSIZE - 2] = { "DCACHEBSIZE: 0x", hex },
311 [AT_ICACHEBSIZE - 2] = { "ICACHEBSIZE: 0x", hex },
312 [AT_UCACHEBSIZE - 2] = { "UCACHEBSIZE: 0x", hex },
313 [AT_IGNOREPPC - 2] = { "IGNOREPPC", ignore },
314 [AT_SECURE - 2] = { "SECURE: ", dec },
315 [AT_BASE_PLATFORM - 2] = { "BASE_PLATFORM: ", str },
316 [AT_SYSINFO - 2] = { "SYSINFO: 0x", hex },
317 [AT_SYSINFO_EHDR - 2] = { "SYSINFO_EHDR: 0x", hex },
318 [AT_RANDOM - 2] = { "RANDOM: 0x", hex },
319 [AT_HWCAP2 - 2] = { "HWCAP2: 0x", hex },
320 [AT_MINSIGSTKSZ - 2] = { "MINSIGSTKSZ ", dec },
321 [AT_L1I_CACHESIZE - 2] = { "L1I_CACHESIZE: ", dec },
322 [AT_L1I_CACHEGEOMETRY - 2] = { "L1I_CACHEGEOMETRY: 0x", hex },
323 [AT_L1D_CACHESIZE - 2] = { "L1D_CACHESIZE: ", dec },
324 [AT_L1D_CACHEGEOMETRY - 2] = { "L1D_CACHEGEOMETRY: 0x", hex },
325 [AT_L2_CACHESIZE - 2] = { "L2_CACHESIZE: ", dec },
326 [AT_L2_CACHEGEOMETRY - 2] = { "L2_CACHEGEOMETRY: 0x", hex },
327 [AT_L3_CACHESIZE - 2] = { "L3_CACHESIZE: ", dec },
328 [AT_L3_CACHEGEOMETRY - 2] = { "L3_CACHEGEOMETRY: 0x", hex },
329 };
330 unsigned int idx = (unsigned int) (av->a_type - 2);
331
332 if ((unsigned int) av->a_type < 2u
333 || (idx < sizeof (auxvars) / sizeof (auxvars[0])
334 && auxvars[idx].form == ignore))
335 continue;
336
337 assert (AT_NULL == 0);
338 assert (AT_IGNORE == 1);
339
340 /* Some entries are handled in a special way per platform. */
341 if (_dl_procinfo (av->a_type, av->a_un.a_val) == 0)
342 continue;
343
344 if (idx < sizeof (auxvars) / sizeof (auxvars[0])
345 && auxvars[idx].form != unknown)
346 {
347 const char *val = (char *) av->a_un.a_val;
348
349 if (__builtin_expect (auxvars[idx].form, dec) == dec)
350 val = _itoa ((unsigned long int) av->a_un.a_val,
351 buf + sizeof buf - 1, 10, 0);
352 else if (__builtin_expect (auxvars[idx].form, hex) == hex)
353 val = _itoa ((unsigned long int) av->a_un.a_val,
354 buf + sizeof buf - 1, 16, 0);
355
356 _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
357
358 continue;
359 }
360
361 /* Unknown value: print a generic line. */
362 char buf2[17];
363 buf2[sizeof (buf2) - 1] = '\0';
364 const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
365 buf2 + sizeof buf2 - 1, 16, 0);
366 const char *val = _itoa ((unsigned long int) av->a_type,
367 buf + sizeof buf - 1, 16, 0);
368 _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
369 }
370}
371
372#endif
373