1/* Relocate a shared object and resolve its references to other loaded objects.
2 Copyright (C) 1995-2017 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 <errno.h>
20#include <libintl.h>
21#include <stdlib.h>
22#include <unistd.h>
23#include <ldsodefs.h>
24#include <sys/mman.h>
25#include <sys/param.h>
26#include <sys/types.h>
27#include <_itoa.h>
28#include <libc-pointer-arith.h>
29#include "dynamic-link.h"
30
31/* Statistics function. */
32#ifdef SHARED
33# define bump_num_cache_relocations() ++GL(dl_num_cache_relocations)
34#else
35# define bump_num_cache_relocations() ((void) 0)
36#endif
37
38
39/* We are trying to perform a static TLS relocation in MAP, but it was
40 dynamically loaded. This can only work if there is enough surplus in
41 the static TLS area already allocated for each running thread. If this
42 object's TLS segment is too big to fit, we fail. If it fits,
43 we set MAP->l_tls_offset and return.
44 This function intentionally does not return any value but signals error
45 directly, as static TLS should be rare and code handling it should
46 not be inlined as much as possible. */
47int
48internal_function
49_dl_try_allocate_static_tls (struct link_map *map)
50{
51 /* If we've already used the variable with dynamic access, or if the
52 alignment requirements are too high, fail. */
53 if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
54 || map->l_tls_align > GL(dl_tls_static_align))
55 {
56 fail:
57 return -1;
58 }
59
60#if TLS_TCB_AT_TP
61 size_t freebytes = GL(dl_tls_static_size) - GL(dl_tls_static_used);
62 if (freebytes < TLS_TCB_SIZE)
63 goto fail;
64 freebytes -= TLS_TCB_SIZE;
65
66 size_t blsize = map->l_tls_blocksize + map->l_tls_firstbyte_offset;
67 if (freebytes < blsize)
68 goto fail;
69
70 size_t n = (freebytes - blsize) / map->l_tls_align;
71
72 size_t offset = GL(dl_tls_static_used) + (freebytes - n * map->l_tls_align
73 - map->l_tls_firstbyte_offset);
74
75 map->l_tls_offset = GL(dl_tls_static_used) = offset;
76#elif TLS_DTV_AT_TP
77 /* dl_tls_static_used includes the TCB at the beginning. */
78 size_t offset = (ALIGN_UP(GL(dl_tls_static_used)
79 - map->l_tls_firstbyte_offset,
80 map->l_tls_align)
81 + map->l_tls_firstbyte_offset);
82 size_t used = offset + map->l_tls_blocksize;
83
84 if (used > GL(dl_tls_static_size))
85 goto fail;
86
87 map->l_tls_offset = offset;
88 map->l_tls_firstbyte_offset = GL(dl_tls_static_used);
89 GL(dl_tls_static_used) = used;
90#else
91# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
92#endif
93
94 /* If the object is not yet relocated we cannot initialize the
95 static TLS region. Delay it. */
96 if (map->l_real->l_relocated)
97 {
98#ifdef SHARED
99 if (__builtin_expect (THREAD_DTV()[0].counter != GL(dl_tls_generation),
100 0))
101 /* Update the slot information data for at least the generation of
102 the DSO we are allocating data for. */
103 (void) _dl_update_slotinfo (map->l_tls_modid);
104#endif
105
106 GL(dl_init_static_tls) (map);
107 }
108 else
109 map->l_need_tls_init = 1;
110
111 return 0;
112}
113
114void
115internal_function __attribute_noinline__
116_dl_allocate_static_tls (struct link_map *map)
117{
118 if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
119 || _dl_try_allocate_static_tls (map))
120 {
121 _dl_signal_error (0, map->l_name, NULL, N_("\
122cannot allocate memory in static TLS block"));
123 }
124}
125
126/* Initialize static TLS area and DTV for current (only) thread.
127 libpthread implementations should provide their own hook
128 to handle all threads. */
129void
130_dl_nothread_init_static_tls (struct link_map *map)
131{
132#if TLS_TCB_AT_TP
133 void *dest = (char *) THREAD_SELF - map->l_tls_offset;
134#elif TLS_DTV_AT_TP
135 void *dest = (char *) THREAD_SELF + map->l_tls_offset + TLS_PRE_TCB_SIZE;
136#else
137# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
138#endif
139
140 /* Initialize the memory. */
141 memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
142 '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
143}
144
145
146void
147_dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
148 int reloc_mode, int consider_profiling)
149{
150 struct textrels
151 {
152 caddr_t start;
153 size_t len;
154 int prot;
155 struct textrels *next;
156 } *textrels = NULL;
157 /* Initialize it to make the compiler happy. */
158 const char *errstring = NULL;
159 int lazy = reloc_mode & RTLD_LAZY;
160 int skip_ifunc = reloc_mode & __RTLD_NOIFUNC;
161
162#ifdef SHARED
163 /* If we are auditing, install the same handlers we need for profiling. */
164 if ((reloc_mode & __RTLD_AUDIT) == 0)
165 consider_profiling |= GLRO(dl_audit) != NULL;
166#elif defined PROF
167 /* Never use dynamic linker profiling for gprof profiling code. */
168# define consider_profiling 0
169#endif
170
171 if (l->l_relocated)
172 return;
173
174 /* If DT_BIND_NOW is set relocate all references in this object. We
175 do not do this if we are profiling, of course. */
176 // XXX Correct for auditing?
177 if (!consider_profiling
178 && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
179 lazy = 0;
180
181 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_RELOC))
182 _dl_debug_printf ("\nrelocation processing: %s%s\n",
183 DSO_FILENAME (l->l_name), lazy ? " (lazy)" : "");
184
185 /* DT_TEXTREL is now in level 2 and might phase out at some time.
186 But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
187 testing easier and therefore it will be available at all time. */
188 if (__glibc_unlikely (l->l_info[DT_TEXTREL] != NULL))
189 {
190 /* Bletch. We must make read-only segments writable
191 long enough to relocate them. */
192 const ElfW(Phdr) *ph;
193 for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
194 if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
195 {
196 struct textrels *newp;
197
198 newp = (struct textrels *) alloca (sizeof (*newp));
199 newp->len = ALIGN_UP (ph->p_vaddr + ph->p_memsz, GLRO(dl_pagesize))
200 - ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize));
201 newp->start = PTR_ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize))
202 + (caddr_t) l->l_addr;
203
204 if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
205 {
206 errstring = N_("cannot make segment writable for relocation");
207 call_error:
208 _dl_signal_error (errno, l->l_name, NULL, errstring);
209 }
210
211#if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
212 newp->prot = (PF_TO_PROT
213 >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
214#else
215 newp->prot = 0;
216 if (ph->p_flags & PF_R)
217 newp->prot |= PROT_READ;
218 if (ph->p_flags & PF_W)
219 newp->prot |= PROT_WRITE;
220 if (ph->p_flags & PF_X)
221 newp->prot |= PROT_EXEC;
222#endif
223 newp->next = textrels;
224 textrels = newp;
225 }
226 }
227
228 {
229 /* Do the actual relocation of the object's GOT and other data. */
230
231 /* String table object symbols. */
232 const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
233
234 /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code. */
235#define RESOLVE_MAP(ref, version, r_type) \
236 ((ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL \
237 && __glibc_likely (!dl_symbol_visibility_binds_local_p (*ref))) \
238 ? ((__builtin_expect ((*ref) == l->l_lookup_cache.sym, 0) \
239 && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class) \
240 ? (bump_num_cache_relocations (), \
241 (*ref) = l->l_lookup_cache.ret, \
242 l->l_lookup_cache.value) \
243 : ({ lookup_t _lr; \
244 int _tc = elf_machine_type_class (r_type); \
245 l->l_lookup_cache.type_class = _tc; \
246 l->l_lookup_cache.sym = (*ref); \
247 const struct r_found_version *v = NULL; \
248 if ((version) != NULL && (version)->hash != 0) \
249 v = (version); \
250 _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref), \
251 scope, v, _tc, \
252 DL_LOOKUP_ADD_DEPENDENCY, NULL); \
253 l->l_lookup_cache.ret = (*ref); \
254 l->l_lookup_cache.value = _lr; })) \
255 : l)
256
257#include "dynamic-link.h"
258
259 ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling, skip_ifunc);
260
261#ifndef PROF
262 if (__glibc_unlikely (consider_profiling)
263 && l->l_info[DT_PLTRELSZ] != NULL)
264 {
265 /* Allocate the array which will contain the already found
266 relocations. If the shared object lacks a PLT (for example
267 if it only contains lead function) the l_info[DT_PLTRELSZ]
268 will be NULL. */
269 size_t sizeofrel = l->l_info[DT_PLTREL]->d_un.d_val == DT_RELA
270 ? sizeof (ElfW(Rela))
271 : sizeof (ElfW(Rel));
272 size_t relcount = l->l_info[DT_PLTRELSZ]->d_un.d_val / sizeofrel;
273 l->l_reloc_result = calloc (sizeof (l->l_reloc_result[0]), relcount);
274
275 if (l->l_reloc_result == NULL)
276 {
277 errstring = N_("\
278%s: out of memory to store relocation results for %s\n");
279 _dl_fatal_printf (errstring, RTLD_PROGNAME, l->l_name);
280 }
281 }
282#endif
283 }
284
285 /* Mark the object so we know this work has been done. */
286 l->l_relocated = 1;
287
288 /* Undo the segment protection changes. */
289 while (__builtin_expect (textrels != NULL, 0))
290 {
291 if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
292 {
293 errstring = N_("cannot restore segment prot after reloc");
294 goto call_error;
295 }
296
297#ifdef CLEAR_CACHE
298 CLEAR_CACHE (textrels->start, textrels->start + textrels->len);
299#endif
300
301 textrels = textrels->next;
302 }
303
304 /* In case we can protect the data now that the relocations are
305 done, do it. */
306 if (l->l_relro_size != 0)
307 _dl_protect_relro (l);
308}
309
310
311void internal_function
312_dl_protect_relro (struct link_map *l)
313{
314 ElfW(Addr) start = ALIGN_DOWN((l->l_addr
315 + l->l_relro_addr),
316 GLRO(dl_pagesize));
317 ElfW(Addr) end = ALIGN_DOWN((l->l_addr
318 + l->l_relro_addr
319 + l->l_relro_size),
320 GLRO(dl_pagesize));
321 if (start != end
322 && __mprotect ((void *) start, end - start, PROT_READ) < 0)
323 {
324 static const char errstring[] = N_("\
325cannot apply additional memory protection after relocation");
326 _dl_signal_error (errno, l->l_name, NULL, errstring);
327 }
328}
329
330void
331internal_function __attribute_noinline__
332_dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
333{
334#define DIGIT(b) _itoa_lower_digits[(b) & 0xf];
335
336 /* XXX We cannot translate these messages. */
337 static const char msg[2][32
338#if __ELF_NATIVE_CLASS == 64
339 + 6
340#endif
341 ] = { "unexpected reloc type 0x",
342 "unexpected PLT reloc type 0x" };
343 char msgbuf[sizeof (msg[0])];
344 char *cp;
345
346 cp = __stpcpy (msgbuf, msg[plt]);
347#if __ELF_NATIVE_CLASS == 64
348 if (__builtin_expect(type > 0xff, 0))
349 {
350 *cp++ = DIGIT (type >> 28);
351 *cp++ = DIGIT (type >> 24);
352 *cp++ = DIGIT (type >> 20);
353 *cp++ = DIGIT (type >> 16);
354 *cp++ = DIGIT (type >> 12);
355 *cp++ = DIGIT (type >> 8);
356 }
357#endif
358 *cp++ = DIGIT (type >> 4);
359 *cp++ = DIGIT (type);
360 *cp = '\0';
361
362 _dl_signal_error (0, map->l_name, NULL, msgbuf);
363}
364