1 /* Relocate a shared object and resolve its references to other loaded objects.
2 Copyright (C) 1995-2023 Free Software Foundation, Inc.
3 Copyright The GNU Toolchain Authors.
4 This file is part of the GNU C Library.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <https://www.gnu.org/licenses/>. */
19
20 #include <errno.h>
21 #include <libintl.h>
22 #include <stdlib.h>
23 #include <unistd.h>
24 #include <ldsodefs.h>
25 #include <sys/mman.h>
26 #include <sys/param.h>
27 #include <sys/types.h>
28 #include <_itoa.h>
29 #include <libc-pointer-arith.h>
30 #include "dynamic-link.h"
31
32 /* Statistics function. */
33 #ifdef SHARED
34 # define bump_num_cache_relocations() ++GL(dl_num_cache_relocations)
35 #else
36 # define bump_num_cache_relocations() ((void) 0)
37 #endif
38
39
40 /* We are trying to perform a static TLS relocation in MAP, but it was
41 dynamically loaded. This can only work if there is enough surplus in
42 the static TLS area already allocated for each running thread. If this
43 object's TLS segment is too big to fit, we fail with -1. If it fits,
44 we set MAP->l_tls_offset and return 0.
45 A portion of the surplus static TLS can be optionally used to optimize
46 dynamic TLS access (with TLSDESC or powerpc TLS optimizations).
47 If OPTIONAL is true then TLS is allocated for such optimization and
48 the caller must have a fallback in case the optional portion of surplus
49 TLS runs out. If OPTIONAL is false then the entire surplus TLS area is
50 considered and the allocation only fails if that runs out. */
51 int
52 _dl_try_allocate_static_tls (struct link_map *map, bool optional)
53 {
54 /* If we've already used the variable with dynamic access, or if the
55 alignment requirements are too high, fail. */
56 if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
57 || map->l_tls_align > GLRO (dl_tls_static_align))
58 {
59 fail:
60 return -1;
61 }
62
63 #if TLS_TCB_AT_TP
64 size_t freebytes = GLRO (dl_tls_static_size) - GL(dl_tls_static_used);
65 if (freebytes < TLS_TCB_SIZE)
66 goto fail;
67 freebytes -= TLS_TCB_SIZE;
68
69 size_t blsize = map->l_tls_blocksize + map->l_tls_firstbyte_offset;
70 if (freebytes < blsize)
71 goto fail;
72
73 size_t n = (freebytes - blsize) / map->l_tls_align;
74
75 /* Account optional static TLS surplus usage. */
76 size_t use = freebytes - n * map->l_tls_align - map->l_tls_firstbyte_offset;
77 if (optional && use > GL(dl_tls_static_optional))
78 goto fail;
79 else if (optional)
80 GL(dl_tls_static_optional) -= use;
81
82 size_t offset = GL(dl_tls_static_used) + use;
83
84 map->l_tls_offset = GL(dl_tls_static_used) = offset;
85 #elif TLS_DTV_AT_TP
86 /* dl_tls_static_used includes the TCB at the beginning. */
87 size_t offset = (ALIGN_UP(GL(dl_tls_static_used)
88 - map->l_tls_firstbyte_offset,
89 map->l_tls_align)
90 + map->l_tls_firstbyte_offset);
91 size_t used = offset + map->l_tls_blocksize;
92
93 if (used > GLRO (dl_tls_static_size))
94 goto fail;
95
96 /* Account optional static TLS surplus usage. */
97 size_t use = used - GL(dl_tls_static_used);
98 if (optional && use > GL(dl_tls_static_optional))
99 goto fail;
100 else if (optional)
101 GL(dl_tls_static_optional) -= use;
102
103 map->l_tls_offset = offset;
104 map->l_tls_firstbyte_offset = GL(dl_tls_static_used);
105 GL(dl_tls_static_used) = used;
106 #else
107 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
108 #endif
109
110 /* If the object is not yet relocated we cannot initialize the
111 static TLS region. Delay it. */
112 if (map->l_real->l_relocated)
113 {
114 #ifdef SHARED
115 if (__builtin_expect (THREAD_DTV()[0].counter != GL(dl_tls_generation),
116 0))
117 /* Update the slot information data for at least the generation of
118 the DSO we are allocating data for. */
119 (void) _dl_update_slotinfo (map->l_tls_modid);
120 #endif
121
122 dl_init_static_tls (map);
123 }
124 else
125 map->l_need_tls_init = 1;
126
127 return 0;
128 }
129
130 /* This function intentionally does not return any value but signals error
131 directly, as static TLS should be rare and code handling it should
132 not be inlined as much as possible. */
133 void
134 __attribute_noinline__
135 _dl_allocate_static_tls (struct link_map *map)
136 {
137 if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
138 || _dl_try_allocate_static_tls (map, false))
139 {
140 _dl_signal_error (0, map->l_name, NULL, N_("\
141 cannot allocate memory in static TLS block"));
142 }
143 }
144
145 #if !PTHREAD_IN_LIBC
146 /* Initialize static TLS area and DTV for current (only) thread.
147 libpthread implementations should provide their own hook
148 to handle all threads. */
149 void
150 _dl_nothread_init_static_tls (struct link_map *map)
151 {
152 #if TLS_TCB_AT_TP
153 void *dest = (char *) THREAD_SELF - map->l_tls_offset;
154 #elif TLS_DTV_AT_TP
155 void *dest = (char *) THREAD_SELF + map->l_tls_offset + TLS_PRE_TCB_SIZE;
156 #else
157 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
158 #endif
159
160 /* Initialize the memory. */
161 memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
162 '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
163 }
164 #endif /* !PTHREAD_IN_LIBC */
165
166 static __always_inline lookup_t
167 resolve_map (lookup_t l, struct r_scope_elem *scope[], const ElfW(Sym) **ref,
168 const struct r_found_version *version, unsigned long int r_type)
169 {
170 if (ELFW(ST_BIND) ((*ref)->st_info) == STB_LOCAL
171 || __glibc_unlikely (dl_symbol_visibility_binds_local_p (*ref)))
172 return l;
173
174 if (__glibc_unlikely (*ref == l->l_lookup_cache.sym)
175 && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class)
176 {
177 bump_num_cache_relocations ();
178 *ref = l->l_lookup_cache.ret;
179 }
180 else
181 {
182 const int tc = elf_machine_type_class (r_type);
183 l->l_lookup_cache.type_class = tc;
184 l->l_lookup_cache.sym = *ref;
185 const char *undef_name
186 = (const char *) D_PTR (l, l_info[DT_STRTAB]) + (*ref)->st_name;
187 const struct r_found_version *v = NULL;
188 if (version != NULL && version->hash != 0)
189 v = version;
190 lookup_t lr = _dl_lookup_symbol_x (
191 undef_name, l, ref, scope, v, tc,
192 DL_LOOKUP_ADD_DEPENDENCY | DL_LOOKUP_FOR_RELOCATE, NULL);
193 l->l_lookup_cache.ret = *ref;
194 l->l_lookup_cache.value = lr;
195 }
196 return l->l_lookup_cache.value;
197 }
198
199 /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code. */
200 #define RESOLVE_MAP resolve_map
201
202 #include "dynamic-link.h"
203
204 void
205 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
206 int reloc_mode, int consider_profiling)
207 {
208 struct textrels
209 {
210 caddr_t start;
211 size_t len;
212 int prot;
213 struct textrels *next;
214 } *textrels = NULL;
215 /* Initialize it to make the compiler happy. */
216 const char *errstring = NULL;
217 int lazy = reloc_mode & RTLD_LAZY;
218 int skip_ifunc = reloc_mode & __RTLD_NOIFUNC;
219
220 #ifdef SHARED
221 bool consider_symbind = false;
222 /* If we are auditing, install the same handlers we need for profiling. */
223 if ((reloc_mode & __RTLD_AUDIT) == 0)
224 {
225 struct audit_ifaces *afct = GLRO(dl_audit);
226 for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
227 {
228 /* Profiling is needed only if PLT hooks are provided. */
229 if (afct->ARCH_LA_PLTENTER != NULL
230 || afct->ARCH_LA_PLTEXIT != NULL)
231 consider_profiling = 1;
232 if (afct->symbind != NULL)
233 consider_symbind = true;
234
235 afct = afct->next;
236 }
237 }
238 #elif defined PROF
239 /* Never use dynamic linker profiling for gprof profiling code. */
240 # define consider_profiling 0
241 #else
242 # define consider_symbind 0
243 #endif
244
245 if (l->l_relocated)
246 return;
247
248 /* If DT_BIND_NOW is set relocate all references in this object. We
249 do not do this if we are profiling, of course. */
250 // XXX Correct for auditing?
251 if (!consider_profiling
252 && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
253 lazy = 0;
254
255 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_RELOC))
256 _dl_debug_printf ("\nrelocation processing: %s%s\n",
257 DSO_FILENAME (l->l_name), lazy ? " (lazy)" : "");
258
259 /* DT_TEXTREL is now in level 2 and might phase out at some time.
260 But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
261 testing easier and therefore it will be available at all time. */
262 if (__glibc_unlikely (l->l_info[DT_TEXTREL] != NULL))
263 {
264 /* Bletch. We must make read-only segments writable
265 long enough to relocate them. */
266 const ElfW(Phdr) *ph;
267 for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
268 if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
269 {
270 struct textrels *newp;
271
272 newp = (struct textrels *) alloca (sizeof (*newp));
273 newp->len = ALIGN_UP (ph->p_vaddr + ph->p_memsz, GLRO(dl_pagesize))
274 - ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize));
275 newp->start = PTR_ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize))
276 + (caddr_t) l->l_addr;
277
278 newp->prot = 0;
279 if (ph->p_flags & PF_R)
280 newp->prot |= PROT_READ;
281 if (ph->p_flags & PF_W)
282 newp->prot |= PROT_WRITE;
283 if (ph->p_flags & PF_X)
284 newp->prot |= PROT_EXEC;
285
286 if (__mprotect (newp->start, newp->len, newp->prot|PROT_WRITE) < 0)
287 {
288 errstring = N_("cannot make segment writable for relocation");
289 call_error:
290 _dl_signal_error (errno, l->l_name, NULL, errstring);
291 }
292
293 newp->next = textrels;
294 textrels = newp;
295 }
296 }
297
298 {
299 /* Do the actual relocation of the object's GOT and other data. */
300
301 ELF_DYNAMIC_RELOCATE (l, scope, lazy, consider_profiling, skip_ifunc);
302
303 #ifndef PROF
304 if ((consider_profiling || consider_symbind)
305 && l->l_info[DT_PLTRELSZ] != NULL)
306 {
307 /* Allocate the array which will contain the already found
308 relocations. If the shared object lacks a PLT (for example
309 if it only contains lead function) the l_info[DT_PLTRELSZ]
310 will be NULL. */
311 size_t sizeofrel = l->l_info[DT_PLTREL]->d_un.d_val == DT_RELA
312 ? sizeof (ElfW(Rela))
313 : sizeof (ElfW(Rel));
314 size_t relcount = l->l_info[DT_PLTRELSZ]->d_un.d_val / sizeofrel;
315 l->l_reloc_result = calloc (sizeof (l->l_reloc_result[0]), relcount);
316
317 if (l->l_reloc_result == NULL)
318 {
319 errstring = N_("\
320 %s: out of memory to store relocation results for %s\n");
321 _dl_fatal_printf (errstring, RTLD_PROGNAME, l->l_name);
322 }
323 }
324 #endif
325 }
326
327 /* Mark the object so we know this work has been done. */
328 l->l_relocated = 1;
329
330 /* Undo the segment protection changes. */
331 while (__builtin_expect (textrels != NULL, 0))
332 {
333 if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
334 {
335 errstring = N_("cannot restore segment prot after reloc");
336 goto call_error;
337 }
338
339 #ifdef CLEAR_CACHE
340 CLEAR_CACHE (textrels->start, textrels->start + textrels->len);
341 #endif
342
343 textrels = textrels->next;
344 }
345
346 /* In case we can protect the data now that the relocations are
347 done, do it. */
348 if (l->l_relro_size != 0)
349 _dl_protect_relro (l);
350 }
351
352
353 void
354 _dl_protect_relro (struct link_map *l)
355 {
356 ElfW(Addr) start = ALIGN_DOWN((l->l_addr
357 + l->l_relro_addr),
358 GLRO(dl_pagesize));
359 ElfW(Addr) end = ALIGN_DOWN((l->l_addr
360 + l->l_relro_addr
361 + l->l_relro_size),
362 GLRO(dl_pagesize));
363 if (start != end
364 && __mprotect ((void *) start, end - start, PROT_READ) < 0)
365 {
366 static const char errstring[] = N_("\
367 cannot apply additional memory protection after relocation");
368 _dl_signal_error (errno, l->l_name, NULL, errstring);
369 }
370 }
371
372 void
373 __attribute_noinline__
374 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
375 {
376 #define DIGIT(b) _itoa_lower_digits[(b) & 0xf];
377
378 /* XXX We cannot translate these messages. */
379 static const char msg[2][32
380 #if __ELF_NATIVE_CLASS == 64
381 + 6
382 #endif
383 ] = { "unexpected reloc type 0x",
384 "unexpected PLT reloc type 0x" };
385 char msgbuf[sizeof (msg[0])];
386 char *cp;
387
388 cp = __stpcpy (msgbuf, msg[plt]);
389 #if __ELF_NATIVE_CLASS == 64
390 if (__builtin_expect(type > 0xff, 0))
391 {
392 *cp++ = DIGIT (type >> 28);
393 *cp++ = DIGIT (type >> 24);
394 *cp++ = DIGIT (type >> 20);
395 *cp++ = DIGIT (type >> 16);
396 *cp++ = DIGIT (type >> 12);
397 *cp++ = DIGIT (type >> 8);
398 }
399 #endif
400 *cp++ = DIGIT (type >> 4);
401 *cp++ = DIGIT (type);
402 *cp = '\0';
403
404 _dl_signal_error (0, map->l_name, NULL, msgbuf);
405 }