1/* Operating system support for run-time dynamic linker. Generic Unix version.
2 Copyright (C) 1995-2019 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/* 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
49extern char **_environ attribute_hidden;
50extern char _end[] attribute_hidden;
51
52/* Protect SUID program against misuse of file descriptors. */
53extern void __libc_check_standard_fds (void);
54
55#ifdef NEED_DL_BASE_ADDR
56ElfW(Addr) _dl_base_addr;
57#endif
58int __libc_enable_secure attribute_relro = 0;
59rtld_hidden_data_def (__libc_enable_secure)
60int __libc_multiple_libcs = 0; /* Defining this here avoids the inclusion
61 of init-first. */
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 for (av = GLRO(dl_auxv); av->a_type != AT_NULL; set_seen (av++))
120 switch (av->a_type)
121 {
122 case AT_PHDR:
123 phdr = (void *) av->a_un.a_val;
124 break;
125 case AT_PHNUM:
126 phnum = av->a_un.a_val;
127 break;
128 case AT_PAGESZ:
129 GLRO(dl_pagesize) = av->a_un.a_val;
130 break;
131 case AT_ENTRY:
132 user_entry = av->a_un.a_val;
133 break;
134#ifdef NEED_DL_BASE_ADDR
135 case AT_BASE:
136 _dl_base_addr = av->a_un.a_val;
137 break;
138#endif
139#ifndef HAVE_AUX_SECURE
140 case AT_UID:
141 case AT_EUID:
142 uid ^= av->a_un.a_val;
143 break;
144 case AT_GID:
145 case AT_EGID:
146 gid ^= av->a_un.a_val;
147 break;
148#endif
149 case AT_SECURE:
150#ifndef HAVE_AUX_SECURE
151 seen = -1;
152#endif
153 __libc_enable_secure = av->a_un.a_val;
154 break;
155 case AT_PLATFORM:
156 GLRO(dl_platform) = (void *) av->a_un.a_val;
157 break;
158 case AT_HWCAP:
159 GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
160 break;
161 case AT_HWCAP2:
162 GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
163 break;
164 case AT_CLKTCK:
165 GLRO(dl_clktck) = av->a_un.a_val;
166 break;
167 case AT_FPUCW:
168 GLRO(dl_fpu_control) = av->a_un.a_val;
169 break;
170#ifdef NEED_DL_SYSINFO
171 case AT_SYSINFO:
172 new_sysinfo = av->a_un.a_val;
173 break;
174#endif
175#ifdef NEED_DL_SYSINFO_DSO
176 case AT_SYSINFO_EHDR:
177 GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
178 break;
179#endif
180 case AT_RANDOM:
181 _dl_random = (void *) av->a_un.a_val;
182 break;
183#ifdef DL_PLATFORM_AUXV
184 DL_PLATFORM_AUXV
185#endif
186 }
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#ifdef DL_SYSDEP_INIT
227 DL_SYSDEP_INIT;
228#endif
229
230#ifdef DL_PLATFORM_INIT
231 DL_PLATFORM_INIT;
232#endif
233
234 /* Determine the length of the platform name. */
235 if (GLRO(dl_platform) != NULL)
236 GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
237
238 if (__sbrk (0) == _end)
239 /* The dynamic linker was run as a program, and so the initial break
240 starts just after our bss, at &_end. The malloc in dl-minimal.c
241 will consume the rest of this page, so tell the kernel to move the
242 break up that far. When the user program examines its break, it
243 will see this new value and not clobber our data. */
244 __sbrk (GLRO(dl_pagesize)
245 - ((_end - (char *) 0) & (GLRO(dl_pagesize) - 1)));
246
247 /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
248 allocated. If necessary we are doing it ourself. If it is not
249 possible we stop the program. */
250 if (__builtin_expect (__libc_enable_secure, 0))
251 __libc_check_standard_fds ();
252
253 (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
254 return user_entry;
255}
256
257void
258_dl_sysdep_start_cleanup (void)
259{
260}
261
262void
263_dl_show_auxv (void)
264{
265 char buf[64];
266 ElfW(auxv_t) *av;
267
268 /* Terminate string. */
269 buf[63] = '\0';
270
271 /* The following code assumes that the AT_* values are encoded
272 starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
273 close by (otherwise the array will be too large). In case we have
274 to support a platform where these requirements are not fulfilled
275 some alternative implementation has to be used. */
276 for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
277 {
278 static const struct
279 {
280 const char label[22];
281 enum { unknown = 0, dec, hex, str, ignore } form : 8;
282 } auxvars[] =
283 {
284 [AT_EXECFD - 2] = { "EXECFD: ", dec },
285 [AT_EXECFN - 2] = { "EXECFN: ", str },
286 [AT_PHDR - 2] = { "PHDR: 0x", hex },
287 [AT_PHENT - 2] = { "PHENT: ", dec },
288 [AT_PHNUM - 2] = { "PHNUM: ", dec },
289 [AT_PAGESZ - 2] = { "PAGESZ: ", dec },
290 [AT_BASE - 2] = { "BASE: 0x", hex },
291 [AT_FLAGS - 2] = { "FLAGS: 0x", hex },
292 [AT_ENTRY - 2] = { "ENTRY: 0x", hex },
293 [AT_NOTELF - 2] = { "NOTELF: ", hex },
294 [AT_UID - 2] = { "UID: ", dec },
295 [AT_EUID - 2] = { "EUID: ", dec },
296 [AT_GID - 2] = { "GID: ", dec },
297 [AT_EGID - 2] = { "EGID: ", dec },
298 [AT_PLATFORM - 2] = { "PLATFORM: ", str },
299 [AT_HWCAP - 2] = { "HWCAP: ", hex },
300 [AT_CLKTCK - 2] = { "CLKTCK: ", dec },
301 [AT_FPUCW - 2] = { "FPUCW: ", hex },
302 [AT_DCACHEBSIZE - 2] = { "DCACHEBSIZE: 0x", hex },
303 [AT_ICACHEBSIZE - 2] = { "ICACHEBSIZE: 0x", hex },
304 [AT_UCACHEBSIZE - 2] = { "UCACHEBSIZE: 0x", hex },
305 [AT_IGNOREPPC - 2] = { "IGNOREPPC", ignore },
306 [AT_SECURE - 2] = { "SECURE: ", dec },
307 [AT_BASE_PLATFORM - 2] = { "BASE_PLATFORM: ", str },
308 [AT_SYSINFO - 2] = { "SYSINFO: 0x", hex },
309 [AT_SYSINFO_EHDR - 2] = { "SYSINFO_EHDR: 0x", hex },
310 [AT_RANDOM - 2] = { "RANDOM: 0x", hex },
311 [AT_HWCAP2 - 2] = { "HWCAP2: 0x", hex },
312 [AT_L1I_CACHESIZE - 2] = { "L1I_CACHESIZE: ", dec },
313 [AT_L1I_CACHEGEOMETRY - 2] = { "L1I_CACHEGEOMETRY: 0x", hex },
314 [AT_L1D_CACHESIZE - 2] = { "L1D_CACHESIZE: ", dec },
315 [AT_L1D_CACHEGEOMETRY - 2] = { "L1D_CACHEGEOMETRY: 0x", hex },
316 [AT_L2_CACHESIZE - 2] = { "L2_CACHESIZE: ", dec },
317 [AT_L2_CACHEGEOMETRY - 2] = { "L2_CACHEGEOMETRY: 0x", hex },
318 [AT_L3_CACHESIZE - 2] = { "L3_CACHESIZE: ", dec },
319 [AT_L3_CACHEGEOMETRY - 2] = { "L3_CACHEGEOMETRY: 0x", hex },
320 };
321 unsigned int idx = (unsigned int) (av->a_type - 2);
322
323 if ((unsigned int) av->a_type < 2u
324 || (idx < sizeof (auxvars) / sizeof (auxvars[0])
325 && auxvars[idx].form == ignore))
326 continue;
327
328 assert (AT_NULL == 0);
329 assert (AT_IGNORE == 1);
330
331 if (av->a_type == AT_HWCAP || av->a_type == AT_HWCAP2
332 || AT_L1I_CACHEGEOMETRY || AT_L1D_CACHEGEOMETRY
333 || AT_L2_CACHEGEOMETRY || AT_L3_CACHEGEOMETRY)
334 {
335 /* These 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
340 if (idx < sizeof (auxvars) / sizeof (auxvars[0])
341 && auxvars[idx].form != unknown)
342 {
343 const char *val = (char *) av->a_un.a_val;
344
345 if (__builtin_expect (auxvars[idx].form, dec) == dec)
346 val = _itoa ((unsigned long int) av->a_un.a_val,
347 buf + sizeof buf - 1, 10, 0);
348 else if (__builtin_expect (auxvars[idx].form, hex) == hex)
349 val = _itoa ((unsigned long int) av->a_un.a_val,
350 buf + sizeof buf - 1, 16, 0);
351
352 _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
353
354 continue;
355 }
356
357 /* Unknown value: print a generic line. */
358 char buf2[17];
359 buf2[sizeof (buf2) - 1] = '\0';
360 const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
361 buf2 + sizeof buf2 - 1, 16, 0);
362 const char *val = _itoa ((unsigned long int) av->a_type,
363 buf + sizeof buf - 1, 16, 0);
364 _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
365 }
366}
367
368#endif
369