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