1 /* Relocate a shared object and resolve its references to other loaded objects.
2 Copyright (C) 1995-2021 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 with -1. If it fits,
43 we set MAP->l_tls_offset and return 0.
44 A portion of the surplus static TLS can be optionally used to optimize
45 dynamic TLS access (with TLSDESC or powerpc TLS optimizations).
46 If OPTIONAL is true then TLS is allocated for such optimization and
47 the caller must have a fallback in case the optional portion of surplus
48 TLS runs out. If OPTIONAL is false then the entire surplus TLS area is
49 considered and the allocation only fails if that runs out. */
51 _dl_try_allocate_static_tls (struct link_map
*map
, bool optional
)
53 /* If we've already used the variable with dynamic access, or if the
54 alignment requirements are too high, fail. */
55 if (map
->l_tls_offset
== FORCED_DYNAMIC_TLS_OFFSET
56 || map
->l_tls_align
> GLRO (dl_tls_static_align
))
63 size_t freebytes
= GLRO (dl_tls_static_size
) - GL(dl_tls_static_used
);
64 if (freebytes
< TLS_TCB_SIZE
)
66 freebytes
-= TLS_TCB_SIZE
;
68 size_t blsize
= map
->l_tls_blocksize
+ map
->l_tls_firstbyte_offset
;
69 if (freebytes
< blsize
)
72 size_t n
= (freebytes
- blsize
) / map
->l_tls_align
;
74 /* Account optional static TLS surplus usage. */
75 size_t use
= freebytes
- n
* map
->l_tls_align
- map
->l_tls_firstbyte_offset
;
76 if (optional
&& use
> GL(dl_tls_static_optional
))
79 GL(dl_tls_static_optional
) -= use
;
81 size_t offset
= GL(dl_tls_static_used
) + use
;
83 map
->l_tls_offset
= GL(dl_tls_static_used
) = offset
;
85 /* dl_tls_static_used includes the TCB at the beginning. */
86 size_t offset
= (ALIGN_UP(GL(dl_tls_static_used
)
87 - map
->l_tls_firstbyte_offset
,
89 + map
->l_tls_firstbyte_offset
);
90 size_t used
= offset
+ map
->l_tls_blocksize
;
92 if (used
> GLRO (dl_tls_static_size
))
95 /* Account optional static TLS surplus usage. */
96 size_t use
= used
- GL(dl_tls_static_used
);
97 if (optional
&& use
> GL(dl_tls_static_optional
))
100 GL(dl_tls_static_optional
) -= use
;
102 map
->l_tls_offset
= offset
;
103 map
->l_tls_firstbyte_offset
= GL(dl_tls_static_used
);
104 GL(dl_tls_static_used
) = used
;
106 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
109 /* If the object is not yet relocated we cannot initialize the
110 static TLS region. Delay it. */
111 if (map
->l_real
->l_relocated
)
114 if (__builtin_expect (THREAD_DTV()[0].counter
!= GL(dl_tls_generation
),
116 /* Update the slot information data for at least the generation of
117 the DSO we are allocating data for. */
118 (void) _dl_update_slotinfo (map
->l_tls_modid
);
121 dl_init_static_tls (map
);
124 map
->l_need_tls_init
= 1;
129 /* This function intentionally does not return any value but signals error
130 directly, as static TLS should be rare and code handling it should
131 not be inlined as much as possible. */
133 __attribute_noinline__
134 _dl_allocate_static_tls (struct link_map
*map
)
136 if (map
->l_tls_offset
== FORCED_DYNAMIC_TLS_OFFSET
137 || _dl_try_allocate_static_tls (map
, false))
139 _dl_signal_error (0, map
->l_name
, NULL
, N_("\
140 cannot allocate memory in static TLS block"));
145 /* Initialize static TLS area and DTV for current (only) thread.
146 libpthread implementations should provide their own hook
147 to handle all threads. */
149 _dl_nothread_init_static_tls (struct link_map
*map
)
152 void *dest
= (char *) THREAD_SELF
- map
->l_tls_offset
;
154 void *dest
= (char *) THREAD_SELF
+ map
->l_tls_offset
+ TLS_PRE_TCB_SIZE
;
156 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
159 /* Initialize the memory. */
160 memset (__mempcpy (dest
, map
->l_tls_initimage
, map
->l_tls_initimage_size
),
161 '\0', map
->l_tls_blocksize
- map
->l_tls_initimage_size
);
163 #endif /* !PTHREAD_IN_LIBC */
165 /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code. */
166 #define RESOLVE_MAP(l, scope, ref, version, r_type) \
167 ((ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL \
168 && __glibc_likely (!dl_symbol_visibility_binds_local_p (*ref))) \
169 ? ((__glibc_unlikely ((*ref) == l->l_lookup_cache.sym) \
170 && elf_machine_type_class (r_type) == l->l_lookup_cache.type_class) \
171 ? (bump_num_cache_relocations (), \
172 (*ref) = l->l_lookup_cache.ret, \
173 l->l_lookup_cache.value) \
175 int _tc = elf_machine_type_class (r_type); \
176 l->l_lookup_cache.type_class = _tc; \
177 l->l_lookup_cache.sym = (*ref); \
178 const struct r_found_version *v = NULL; \
179 if ((version) != NULL && (version)->hash != 0) \
181 _lr = _dl_lookup_symbol_x ((const char *) D_PTR (l, l_info[DT_STRTAB]) + (*ref)->st_name, \
182 l, (ref), scope, v, _tc, \
183 DL_LOOKUP_ADD_DEPENDENCY \
184 | DL_LOOKUP_FOR_RELOCATE, NULL); \
185 l->l_lookup_cache.ret = (*ref); \
186 l->l_lookup_cache.value = _lr; })) \
189 #include "dynamic-link.h"
192 _dl_relocate_object (struct link_map
*l
, struct r_scope_elem
*scope
[],
193 int reloc_mode
, int consider_profiling
)
200 struct textrels
*next
;
202 /* Initialize it to make the compiler happy. */
203 const char *errstring
= NULL
;
204 int lazy
= reloc_mode
& RTLD_LAZY
;
205 int skip_ifunc
= reloc_mode
& __RTLD_NOIFUNC
;
208 /* If we are auditing, install the same handlers we need for profiling. */
209 if ((reloc_mode
& __RTLD_AUDIT
) == 0)
210 consider_profiling
|= GLRO(dl_audit
) != NULL
;
212 /* Never use dynamic linker profiling for gprof profiling code. */
213 # define consider_profiling 0
219 /* If DT_BIND_NOW is set relocate all references in this object. We
220 do not do this if we are profiling, of course. */
221 // XXX Correct for auditing?
222 if (!consider_profiling
223 && __builtin_expect (l
->l_info
[DT_BIND_NOW
] != NULL
, 0))
226 if (__glibc_unlikely (GLRO(dl_debug_mask
) & DL_DEBUG_RELOC
))
227 _dl_debug_printf ("\nrelocation processing: %s%s\n",
228 DSO_FILENAME (l
->l_name
), lazy
? " (lazy)" : "");
230 /* DT_TEXTREL is now in level 2 and might phase out at some time.
231 But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
232 testing easier and therefore it will be available at all time. */
233 if (__glibc_unlikely (l
->l_info
[DT_TEXTREL
] != NULL
))
235 /* Bletch. We must make read-only segments writable
236 long enough to relocate them. */
237 const ElfW(Phdr
) *ph
;
238 for (ph
= l
->l_phdr
; ph
< &l
->l_phdr
[l
->l_phnum
]; ++ph
)
239 if (ph
->p_type
== PT_LOAD
&& (ph
->p_flags
& PF_W
) == 0)
241 struct textrels
*newp
;
243 newp
= (struct textrels
*) alloca (sizeof (*newp
));
244 newp
->len
= ALIGN_UP (ph
->p_vaddr
+ ph
->p_memsz
, GLRO(dl_pagesize
))
245 - ALIGN_DOWN (ph
->p_vaddr
, GLRO(dl_pagesize
));
246 newp
->start
= PTR_ALIGN_DOWN (ph
->p_vaddr
, GLRO(dl_pagesize
))
247 + (caddr_t
) l
->l_addr
;
250 if (ph
->p_flags
& PF_R
)
251 newp
->prot
|= PROT_READ
;
252 if (ph
->p_flags
& PF_W
)
253 newp
->prot
|= PROT_WRITE
;
254 if (ph
->p_flags
& PF_X
)
255 newp
->prot
|= PROT_EXEC
;
257 if (__mprotect (newp
->start
, newp
->len
, newp
->prot
|PROT_WRITE
) < 0)
259 errstring
= N_("cannot make segment writable for relocation");
261 _dl_signal_error (errno
, l
->l_name
, NULL
, errstring
);
264 newp
->next
= textrels
;
270 /* Do the actual relocation of the object's GOT and other data. */
272 ELF_DYNAMIC_RELOCATE (l
, scope
, lazy
, consider_profiling
, skip_ifunc
);
275 if (__glibc_unlikely (consider_profiling
)
276 && l
->l_info
[DT_PLTRELSZ
] != NULL
)
278 /* Allocate the array which will contain the already found
279 relocations. If the shared object lacks a PLT (for example
280 if it only contains lead function) the l_info[DT_PLTRELSZ]
282 size_t sizeofrel
= l
->l_info
[DT_PLTREL
]->d_un
.d_val
== DT_RELA
283 ? sizeof (ElfW(Rela
))
284 : sizeof (ElfW(Rel
));
285 size_t relcount
= l
->l_info
[DT_PLTRELSZ
]->d_un
.d_val
/ sizeofrel
;
286 l
->l_reloc_result
= calloc (sizeof (l
->l_reloc_result
[0]), relcount
);
288 if (l
->l_reloc_result
== NULL
)
291 %s: out of memory to store relocation results for %s\n");
292 _dl_fatal_printf (errstring
, RTLD_PROGNAME
, l
->l_name
);
298 /* Mark the object so we know this work has been done. */
301 /* Undo the segment protection changes. */
302 while (__builtin_expect (textrels
!= NULL
, 0))
304 if (__mprotect (textrels
->start
, textrels
->len
, textrels
->prot
) < 0)
306 errstring
= N_("cannot restore segment prot after reloc");
311 CLEAR_CACHE (textrels
->start
, textrels
->start
+ textrels
->len
);
314 textrels
= textrels
->next
;
317 /* In case we can protect the data now that the relocations are
319 if (l
->l_relro_size
!= 0)
320 _dl_protect_relro (l
);
325 _dl_protect_relro (struct link_map
*l
)
327 ElfW(Addr
) start
= ALIGN_DOWN((l
->l_addr
330 ElfW(Addr
) end
= ALIGN_DOWN((l
->l_addr
335 && __mprotect ((void *) start
, end
- start
, PROT_READ
) < 0)
337 static const char errstring
[] = N_("\
338 cannot apply additional memory protection after relocation");
339 _dl_signal_error (errno
, l
->l_name
, NULL
, errstring
);
344 __attribute_noinline__
345 _dl_reloc_bad_type (struct link_map
*map
, unsigned int type
, int plt
)
347 #define DIGIT(b) _itoa_lower_digits[(b) & 0xf];
349 /* XXX We cannot translate these messages. */
350 static const char msg
[2][32
351 #if __ELF_NATIVE_CLASS == 64
354 ] = { "unexpected reloc type 0x",
355 "unexpected PLT reloc type 0x" };
356 char msgbuf
[sizeof (msg
[0])];
359 cp
= __stpcpy (msgbuf
, msg
[plt
]);
360 #if __ELF_NATIVE_CLASS == 64
361 if (__builtin_expect(type
> 0xff, 0))
363 *cp
++ = DIGIT (type
>> 28);
364 *cp
++ = DIGIT (type
>> 24);
365 *cp
++ = DIGIT (type
>> 20);
366 *cp
++ = DIGIT (type
>> 16);
367 *cp
++ = DIGIT (type
>> 12);
368 *cp
++ = DIGIT (type
>> 8);
371 *cp
++ = DIGIT (type
>> 4);
372 *cp
++ = DIGIT (type
);
375 _dl_signal_error (0, map
->l_name
, NULL
, msgbuf
);