1/* Operating system support for run-time dynamic linker. Generic Unix version.
2 Copyright (C) 1995-2020 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
50extern char **_environ attribute_hidden;
51extern char _end[] attribute_hidden;
52
53/* Protect SUID program against misuse of file descriptors. */
54extern void __libc_check_standard_fds (void);
55
56#ifdef NEED_DL_BASE_ADDR
57ElfW(Addr) _dl_base_addr;
58#endif
59int __libc_enable_secure attribute_relro = 0;
60rtld_hidden_data_def (__libc_enable_secure)
61int __libc_multiple_libcs = 0; /* Defining this here avoids the inclusion
62 of init-first. */
63/* This variable contains the lowest stack address ever used. */
64void *__libc_stack_end attribute_relro = NULL;
65rtld_hidden_data_def(__libc_stack_end)
66void *_dl_random attribute_relro = NULL;
67
68#ifndef DL_FIND_ARG_COMPONENTS
69# define DL_FIND_ARG_COMPONENTS(cookie, argc, argv, envp, auxp) \
70 do { \
71 void **_tmp; \
72 (argc) = *(long int *) cookie; \
73 (argv) = (char **) ((long int *) cookie + 1); \
74 (envp) = (argv) + (argc) + 1; \
75 for (_tmp = (void **) (envp); *_tmp; ++_tmp) \
76 continue; \
77 (auxp) = (void *) ++_tmp; \
78 } while (0)
79#endif
80
81#ifndef DL_STACK_END
82# define DL_STACK_END(cookie) ((void *) (cookie))
83#endif
84
85ElfW(Addr)
86_dl_sysdep_start (void **start_argptr,
87 void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
88 ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
89{
90 const ElfW(Phdr) *phdr = NULL;
91 ElfW(Word) phnum = 0;
92 ElfW(Addr) user_entry;
93 ElfW(auxv_t) *av;
94#ifdef HAVE_AUX_SECURE
95# define set_seen(tag) (tag) /* Evaluate for the side effects. */
96# define set_seen_secure() ((void) 0)
97#else
98 uid_t uid = 0;
99 gid_t gid = 0;
100 unsigned int seen = 0;
101# define set_seen_secure() (seen = -1)
102# ifdef HAVE_AUX_XID
103# define set_seen(tag) (tag) /* Evaluate for the side effects. */
104# else
105# define M(type) (1 << (type))
106# define set_seen(tag) seen |= M ((tag)->a_type)
107# endif
108#endif
109#ifdef NEED_DL_SYSINFO
110 uintptr_t new_sysinfo = 0;
111#endif
112
113 __libc_stack_end = DL_STACK_END (start_argptr);
114 DL_FIND_ARG_COMPONENTS (start_argptr, _dl_argc, _dl_argv, _environ,
115 GLRO(dl_auxv));
116
117 user_entry = (ElfW(Addr)) ENTRY_POINT;
118 GLRO(dl_platform) = NULL; /* Default to nothing known about the platform. */
119
120 for (av = GLRO(dl_auxv); av->a_type != AT_NULL; set_seen (av++))
121 switch (av->a_type)
122 {
123 case AT_PHDR:
124 phdr = (void *) av->a_un.a_val;
125 break;
126 case AT_PHNUM:
127 phnum = av->a_un.a_val;
128 break;
129 case AT_PAGESZ:
130 GLRO(dl_pagesize) = av->a_un.a_val;
131 break;
132 case AT_ENTRY:
133 user_entry = av->a_un.a_val;
134 break;
135#ifdef NEED_DL_BASE_ADDR
136 case AT_BASE:
137 _dl_base_addr = av->a_un.a_val;
138 break;
139#endif
140#ifndef HAVE_AUX_SECURE
141 case AT_UID:
142 case AT_EUID:
143 uid ^= av->a_un.a_val;
144 break;
145 case AT_GID:
146 case AT_EGID:
147 gid ^= av->a_un.a_val;
148 break;
149#endif
150 case AT_SECURE:
151#ifndef HAVE_AUX_SECURE
152 seen = -1;
153#endif
154 __libc_enable_secure = av->a_un.a_val;
155 break;
156 case AT_PLATFORM:
157 GLRO(dl_platform) = (void *) av->a_un.a_val;
158 break;
159 case AT_HWCAP:
160 GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
161 break;
162 case AT_HWCAP2:
163 GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
164 break;
165 case AT_CLKTCK:
166 GLRO(dl_clktck) = av->a_un.a_val;
167 break;
168 case AT_FPUCW:
169 GLRO(dl_fpu_control) = av->a_un.a_val;
170 break;
171#ifdef NEED_DL_SYSINFO
172 case AT_SYSINFO:
173 new_sysinfo = av->a_un.a_val;
174 break;
175#endif
176#ifdef NEED_DL_SYSINFO_DSO
177 case AT_SYSINFO_EHDR:
178 GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
179 break;
180#endif
181 case AT_RANDOM:
182 _dl_random = (void *) av->a_un.a_val;
183 break;
184 DL_PLATFORM_AUXV
185 }
186
187#ifndef HAVE_AUX_SECURE
188 if (seen != -1)
189 {
190 /* Fill in the values we have not gotten from the kernel through the
191 auxiliary vector. */
192# ifndef HAVE_AUX_XID
193# define SEE(UID, var, uid) \
194 if ((seen & M (AT_##UID)) == 0) var ^= __get##uid ()
195 SEE (UID, uid, uid);
196 SEE (EUID, uid, euid);
197 SEE (GID, gid, gid);
198 SEE (EGID, gid, egid);
199# endif
200
201 /* If one of the two pairs of IDs does not match this is a setuid
202 or setgid run. */
203 __libc_enable_secure = uid | gid;
204 }
205#endif
206
207#ifndef HAVE_AUX_PAGESIZE
208 if (GLRO(dl_pagesize) == 0)
209 GLRO(dl_pagesize) = __getpagesize ();
210#endif
211
212#ifdef NEED_DL_SYSINFO
213 if (new_sysinfo != 0)
214 {
215# ifdef NEED_DL_SYSINFO_DSO
216 /* Only set the sysinfo value if we also have the vsyscall DSO. */
217 if (GLRO(dl_sysinfo_dso) != 0)
218# endif
219 GLRO(dl_sysinfo) = new_sysinfo;
220 }
221#endif
222
223 __tunables_init (_environ);
224
225#ifdef DL_SYSDEP_INIT
226 DL_SYSDEP_INIT;
227#endif
228
229#ifdef DL_PLATFORM_INIT
230 DL_PLATFORM_INIT;
231#endif
232
233 /* Determine the length of the platform name. */
234 if (GLRO(dl_platform) != NULL)
235 GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
236
237 if (__sbrk (0) == _end)
238 /* The dynamic linker was run as a program, and so the initial break
239 starts just after our bss, at &_end. The malloc in dl-minimal.c
240 will consume the rest of this page, so tell the kernel to move the
241 break up that far. When the user program examines its break, it
242 will see this new value and not clobber our data. */
243 __sbrk (GLRO(dl_pagesize)
244 - ((_end - (char *) 0) & (GLRO(dl_pagesize) - 1)));
245
246 /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
247 allocated. If necessary we are doing it ourself. If it is not
248 possible we stop the program. */
249 if (__builtin_expect (__libc_enable_secure, 0))
250 __libc_check_standard_fds ();
251
252 (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
253 return user_entry;
254}
255
256void
257_dl_sysdep_start_cleanup (void)
258{
259}
260
261void
262_dl_show_auxv (void)
263{
264 char buf[64];
265 ElfW(auxv_t) *av;
266
267 /* Terminate string. */
268 buf[63] = '\0';
269
270 /* The following code assumes that the AT_* values are encoded
271 starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
272 close by (otherwise the array will be too large). In case we have
273 to support a platform where these requirements are not fulfilled
274 some alternative implementation has to be used. */
275 for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
276 {
277 static const struct
278 {
279 const char label[22];
280 enum { unknown = 0, dec, hex, str, ignore } form : 8;
281 } auxvars[] =
282 {
283 [AT_EXECFD - 2] = { "EXECFD: ", dec },
284 [AT_EXECFN - 2] = { "EXECFN: ", str },
285 [AT_PHDR - 2] = { "PHDR: 0x", hex },
286 [AT_PHENT - 2] = { "PHENT: ", dec },
287 [AT_PHNUM - 2] = { "PHNUM: ", dec },
288 [AT_PAGESZ - 2] = { "PAGESZ: ", dec },
289 [AT_BASE - 2] = { "BASE: 0x", hex },
290 [AT_FLAGS - 2] = { "FLAGS: 0x", hex },
291 [AT_ENTRY - 2] = { "ENTRY: 0x", hex },
292 [AT_NOTELF - 2] = { "NOTELF: ", hex },
293 [AT_UID - 2] = { "UID: ", dec },
294 [AT_EUID - 2] = { "EUID: ", dec },
295 [AT_GID - 2] = { "GID: ", dec },
296 [AT_EGID - 2] = { "EGID: ", dec },
297 [AT_PLATFORM - 2] = { "PLATFORM: ", str },
298 [AT_HWCAP - 2] = { "HWCAP: ", hex },
299 [AT_CLKTCK - 2] = { "CLKTCK: ", dec },
300 [AT_FPUCW - 2] = { "FPUCW: ", hex },
301 [AT_DCACHEBSIZE - 2] = { "DCACHEBSIZE: 0x", hex },
302 [AT_ICACHEBSIZE - 2] = { "ICACHEBSIZE: 0x", hex },
303 [AT_UCACHEBSIZE - 2] = { "UCACHEBSIZE: 0x", hex },
304 [AT_IGNOREPPC - 2] = { "IGNOREPPC", ignore },
305 [AT_SECURE - 2] = { "SECURE: ", dec },
306 [AT_BASE_PLATFORM - 2] = { "BASE_PLATFORM: ", str },
307 [AT_SYSINFO - 2] = { "SYSINFO: 0x", hex },
308 [AT_SYSINFO_EHDR - 2] = { "SYSINFO_EHDR: 0x", hex },
309 [AT_RANDOM - 2] = { "RANDOM: 0x", hex },
310 [AT_HWCAP2 - 2] = { "HWCAP2: 0x", hex },
311 [AT_L1I_CACHESIZE - 2] = { "L1I_CACHESIZE: ", dec },
312 [AT_L1I_CACHEGEOMETRY - 2] = { "L1I_CACHEGEOMETRY: 0x", hex },
313 [AT_L1D_CACHESIZE - 2] = { "L1D_CACHESIZE: ", dec },
314 [AT_L1D_CACHEGEOMETRY - 2] = { "L1D_CACHEGEOMETRY: 0x", hex },
315 [AT_L2_CACHESIZE - 2] = { "L2_CACHESIZE: ", dec },
316 [AT_L2_CACHEGEOMETRY - 2] = { "L2_CACHEGEOMETRY: 0x", hex },
317 [AT_L3_CACHESIZE - 2] = { "L3_CACHESIZE: ", dec },
318 [AT_L3_CACHEGEOMETRY - 2] = { "L3_CACHEGEOMETRY: 0x", hex },
319 };
320 unsigned int idx = (unsigned int) (av->a_type - 2);
321
322 if ((unsigned int) av->a_type < 2u
323 || (idx < sizeof (auxvars) / sizeof (auxvars[0])
324 && auxvars[idx].form == ignore))
325 continue;
326
327 assert (AT_NULL == 0);
328 assert (AT_IGNORE == 1);
329
330 /* Some entries are handled in a special way per platform. */
331 if (_dl_procinfo (av->a_type, av->a_un.a_val) == 0)
332 continue;
333
334 if (idx < sizeof (auxvars) / sizeof (auxvars[0])
335 && auxvars[idx].form != unknown)
336 {
337 const char *val = (char *) av->a_un.a_val;
338
339 if (__builtin_expect (auxvars[idx].form, dec) == dec)
340 val = _itoa ((unsigned long int) av->a_un.a_val,
341 buf + sizeof buf - 1, 10, 0);
342 else if (__builtin_expect (auxvars[idx].form, hex) == hex)
343 val = _itoa ((unsigned long int) av->a_un.a_val,
344 buf + sizeof buf - 1, 16, 0);
345
346 _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
347
348 continue;
349 }
350
351 /* Unknown value: print a generic line. */
352 char buf2[17];
353 buf2[sizeof (buf2) - 1] = '\0';
354 const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
355 buf2 + sizeof buf2 - 1, 16, 0);
356 const char *val = _itoa ((unsigned long int) av->a_type,
357 buf + sizeof buf - 1, 16, 0);
358 _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
359 }
360}
361
362#endif
363