1 /* Relocate a shared object and resolve its references to other loaded objects.
2 Copyright (C) 1995-2020 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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.
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.
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/>. */
25 #include <sys/param.h>
26 #include <sys/types.h>
28 #include <libc-pointer-arith.h>
29 #include "dynamic-link.h"
31 /* Statistics function. */
33 # define bump_num_cache_relocations() ++GL(dl_num_cache_relocations)
35 # define bump_num_cache_relocations() ((void) 0)
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. */
48 _dl_try_allocate_static_tls (struct link_map *map)
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))
60 size_t freebytes = GL(dl_tls_static_size) - GL(dl_tls_static_used);
61 if (freebytes < TLS_TCB_SIZE)
63 freebytes -= TLS_TCB_SIZE;
65 size_t blsize = map->l_tls_blocksize + map->l_tls_firstbyte_offset;
66 if (freebytes < blsize)
69 size_t n = (freebytes - blsize) / map->l_tls_align;
71 size_t offset = GL(dl_tls_static_used) + (freebytes - n * map->l_tls_align
72 - map->l_tls_firstbyte_offset);
74 map->l_tls_offset = GL(dl_tls_static_used) = offset;
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,
80 + map->l_tls_firstbyte_offset);
81 size_t used = offset + map->l_tls_blocksize;
83 if (used > GL(dl_tls_static_size))
86 map->l_tls_offset = offset;
87 map->l_tls_firstbyte_offset = GL(dl_tls_static_used);
88 GL(dl_tls_static_used) = used;
90 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
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)
98 if (__builtin_expect (THREAD_DTV()[0].counter != GL(dl_tls_generation),
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);
105 GL(dl_init_static_tls) (map);
108 map->l_need_tls_init = 1;
114 __attribute_noinline__
115 _dl_allocate_static_tls (struct link_map *map)
117 if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
118 || _dl_try_allocate_static_tls (map))
120 _dl_signal_error (0, map->l_name, NULL, N_("\
121 cannot allocate memory in static TLS block"));
125 /* Initialize static TLS area and DTV for current (only) thread.
126 libpthread implementations should provide their own hook
127 to handle all threads. */
129 _dl_nothread_init_static_tls (struct link_map *map)
132 void *dest = (char *) THREAD_SELF - map->l_tls_offset;
134 void *dest = (char *) THREAD_SELF + map->l_tls_offset + TLS_PRE_TCB_SIZE;
136 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
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);
146 _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
147 int reloc_mode, int consider_profiling)
154 struct textrels *next;
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;
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;
166 /* Never use dynamic linker profiling for gprof profiling code. */
167 # define consider_profiling 0
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))
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)" : "");
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))
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)
195 struct textrels *newp;
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;
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;
211 if (__mprotect (newp->start, newp->len, newp->prot|PROT_WRITE) < 0)
213 errstring = N_("cannot make segment writable for relocation");
215 _dl_signal_error (errno, l->l_name, NULL, errstring);
218 newp->next = textrels;
224 /* Do the actual relocation of the object's GOT and other data. */
226 /* String table object symbols. */
227 const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
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) \
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) \
245 _lr = _dl_lookup_symbol_x (strtab + (*ref)->st_name, l, (ref), \
247 DL_LOOKUP_ADD_DEPENDENCY \
248 | DL_LOOKUP_FOR_RELOCATE, NULL); \
249 l->l_lookup_cache.ret = (*ref); \
250 l->l_lookup_cache.value = _lr; })) \
253 #include "dynamic-link.h"
255 ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling, skip_ifunc);
258 if (__glibc_unlikely (consider_profiling)
259 && l->l_info[DT_PLTRELSZ] != NULL)
261 /* Allocate the array which will contain the already found
262 relocations. If the shared object lacks a PLT (for example
263 if it only contains lead function) the l_info[DT_PLTRELSZ]
265 size_t sizeofrel = l->l_info[DT_PLTREL]->d_un.d_val == DT_RELA
266 ? sizeof (ElfW(Rela))
267 : sizeof (ElfW(Rel));
268 size_t relcount = l->l_info[DT_PLTRELSZ]->d_un.d_val / sizeofrel;
269 l->l_reloc_result = calloc (sizeof (l->l_reloc_result[0]), relcount);
271 if (l->l_reloc_result == NULL)
274 %s: out of memory to store relocation results for %s\n");
275 _dl_fatal_printf (errstring, RTLD_PROGNAME, l->l_name);
281 /* Mark the object so we know this work has been done. */
284 /* Undo the segment protection changes. */
285 while (__builtin_expect (textrels != NULL, 0))
287 if (__mprotect (textrels->start, textrels->len, textrels->prot) < 0)
289 errstring = N_("cannot restore segment prot after reloc");
294 CLEAR_CACHE (textrels->start, textrels->start + textrels->len);
297 textrels = textrels->next;
300 /* In case we can protect the data now that the relocations are
302 if (l->l_relro_size != 0)
303 _dl_protect_relro (l);
308 _dl_protect_relro (struct link_map *l)
310 ElfW(Addr) start = ALIGN_DOWN((l->l_addr
313 ElfW(Addr) end = ALIGN_DOWN((l->l_addr
318 && __mprotect ((void *) start, end - start, PROT_READ) < 0)
320 static const char errstring[] = N_("\
321 cannot apply additional memory protection after relocation");
322 _dl_signal_error (errno, l->l_name, NULL, errstring);
327 __attribute_noinline__
328 _dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
330 #define DIGIT(b) _itoa_lower_digits[(b) & 0xf];
332 /* XXX We cannot translate these messages. */
333 static const char msg[2][32
334 #if __ELF_NATIVE_CLASS == 64
337 ] = { "unexpected reloc type 0x",
338 "unexpected PLT reloc type 0x" };
339 char msgbuf[sizeof (msg[0])];
342 cp = __stpcpy (msgbuf, msg[plt]);
343 #if __ELF_NATIVE_CLASS == 64
344 if (__builtin_expect(type > 0xff, 0))
346 *cp++ = DIGIT (type >> 28);
347 *cp++ = DIGIT (type >> 24);
348 *cp++ = DIGIT (type >> 20);
349 *cp++ = DIGIT (type >> 16);
350 *cp++ = DIGIT (type >> 12);
351 *cp++ = DIGIT (type >> 8);
354 *cp++ = DIGIT (type >> 4);
355 *cp++ = DIGIT (type);
358 _dl_signal_error (0, map->l_name, NULL, msgbuf);