1 /* $NetBSD: rtld.h,v 1.150 2025/05/02 23:04:31 riastradh Exp $ */
2
3 /*
4 * Copyright 1996 John D. Polstra.
5 * Copyright 1996 Matt Thomas <matt@3am-software.com>
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by John Polstra.
19 * 4. The name of the author may not be used to endorse or promote products
20 * derived from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34 #ifndef RTLD_H
35 #define RTLD_H
36
37 #include <dlfcn.h>
38 #include <signal.h>
39 #include <stdbool.h>
40 #include <stddef.h>
41 #include <sys/param.h>
42 #include <sys/types.h>
43 #include <sys/queue.h>
44 #include <sys/exec_elf.h>
45 #include <sys/tls.h>
46 #include "rtldenv.h"
47 #include "link.h"
48
49 #if defined(_RTLD_SOURCE)
50
51 #if defined(__ARM_EABI__) && !defined(__ARM_DWARF_EH__)
52 #include "unwind.h"
53 #endif
54
55 #ifndef RTLD_DEFAULT_LIBRARY_PATH
56 #define RTLD_DEFAULT_LIBRARY_PATH "/usr/lib"
57 #endif
58 #define _PATH_LD_HINTS "/etc/ld.so.conf"
59
60 extern size_t _rtld_pagesz;
61
62 #define round_down(x) ((x) & ~(_rtld_pagesz - 1))
63 #define round_up(x) round_down((x) + _rtld_pagesz - 1)
64
65 #define NEW(type) ((type *) xmalloc(sizeof(type)))
66 #define CNEW(type) ((type *) xcalloc(sizeof(type)))
67
68 /*
69 * Fill in a DoneList with an allocation large enough to hold all of
70 * the currently-loaded objects. Keep this in a macro since it calls
71 * alloca and we want that to occur within the scope of the caller.
72 * Callers must be built with -Wno-stack-protector.
73 */
74 #define _rtld_donelist_init(dlp) \
75 ((dlp)->num_alloc = _rtld_objcount, \
76 (dlp)->objs = alloca((dlp)->num_alloc * sizeof((dlp)->objs[0])), \
77 assert((dlp)->objs != NULL), \
78 (dlp)->num_used = 0)
79
80
81 typedef struct Struct_Elf_Hash {
82 unsigned long sysv;
83 unsigned long gnu;
84 } Elf_Hash;
85 #endif /* _RTLD_SOURCE */
86
87 /*
88 * C++ has mandated the use of the following keywords for its new boolean
89 * type. We might as well follow their lead.
90 */
91 struct Struct_Obj_Entry;
92
93 typedef struct Struct_Objlist_Entry {
94 SIMPLEQ_ENTRY(Struct_Objlist_Entry) link;
95 struct Struct_Obj_Entry *obj;
96 } Objlist_Entry;
97
98 typedef SIMPLEQ_HEAD(Struct_Objlist, Struct_Objlist_Entry) Objlist;
99
100 typedef struct Struct_Name_Entry {
101 SIMPLEQ_ENTRY(Struct_Name_Entry) link;
102 char name[1];
103 } Name_Entry;
104
105 typedef struct Struct_Needed_Entry {
106 struct Struct_Needed_Entry *next;
107 struct Struct_Obj_Entry *obj;
108 unsigned long name; /* Offset of name in string table */
109 } Needed_Entry;
110
111 typedef struct _rtld_search_path_t {
112 struct _rtld_search_path_t *sp_next;
113 const char *sp_path;
114 size_t sp_pathlen;
115 } Search_Path;
116
117 typedef struct Struct_Ver_Entry {
118 Elf_Word hash;
119 u_int flags;
120 const char *name;
121 const char *file;
122 } Ver_Entry;
123
124 /* Ver_Entry.flags */
125 #define VER_INFO_HIDDEN 0x01
126
127 #define RTLD_MAX_ENTRY 10
128 #define RTLD_MAX_LIBRARY 4
129 #define RTLD_MAX_CTL 2
130 typedef struct _rtld_library_xform_t {
131 struct _rtld_library_xform_t *next;
132 char *name;
133 const char *ctlname;
134 struct {
135 char *value;
136 char *library[RTLD_MAX_LIBRARY];
137 } entry[RTLD_MAX_ENTRY];
138 } Library_Xform;
139
140 /*
141 * Shared object descriptor.
142 *
143 * Items marked with "(%)" are dynamically allocated, and must be freed
144 * when the structure is destroyed.
145 */
146
147 typedef void (*fptr_t)(void);
148
149 typedef struct Struct_Obj_Entry {
150 struct Struct_Obj_Entry *next;
151 char *path; /* Pathname of underlying file (%) */
152 int refcount;
153 int dl_refcount; /* Number of times loaded by dlopen */
154
155 /* These items are computed by map_object() or by digest_phdr(). */
156 caddr_t mapbase; /* Base address of mapped region */
157 size_t mapsize; /* Size of mapped region in bytes */
158 size_t textsize; /* Size of text segment in bytes */
159 Elf_Addr vaddrbase; /* Base address in shared object file */
160 caddr_t relocbase; /* Reloc const = mapbase - *vaddrbase */
161 Elf_Dyn *dynamic; /* Dynamic section */
162 caddr_t entry; /* Entry point */
163 const Elf_Phdr *phdr; /* Program header (may be xmalloc'ed) */
164 size_t phsize; /* Size of program header in bytes */
165
166 /* Items from the dynamic section. */
167 Elf_Addr *pltgot; /* PLTGOT table */
168 const Elf_Rel *rel; /* Relocation entries */
169 const Elf_Rel *rellim; /* Limit of Relocation entries */
170 const Elf_Rela *rela; /* Relocation entries */
171 const Elf_Rela *relalim; /* Limit of Relocation entries */
172 const Elf_Relr *relr; /* Relative relocations */
173 const Elf_Relr *relrlim; /* Limit of relative relocations */
174 const Elf_Rel *pltrel; /* PLT relocation entries */
175 const Elf_Rel *pltrellim; /* Limit of PLT relocation entries */
176 const Elf_Rela *pltrela; /* PLT relocation entries */
177 const Elf_Rela *pltrelalim; /* Limit of PLT relocation entries */
178 const Elf_Sym *symtab; /* Symbol table */
179 const char *strtab; /* String table */
180 unsigned long strsize; /* Size in bytes of string table */
181 #if defined(__mips__) || defined(__riscv__)
182 Elf_Word local_gotno; /* Number of local GOT entries */
183 Elf_Word symtabno; /* Number of dynamic symbols */
184 Elf_Word gotsym; /* First dynamic symbol in GOT */
185 #endif
186
187 /* SysV Hash fields */
188 const Elf_Symindx *buckets; /* Hash table buckets array */
189 unsigned long unused1; /* Used to be nbuckets */
190 const Elf_Symindx *chains; /* Hash table chain array */
191 unsigned long nchains; /* Number of chains */
192
193 Search_Path *rpaths; /* Search path specified in object */
194 Needed_Entry *needed; /* Shared objects needed by this (%) */
195
196 fptr_t init; /* Initialization function to call */
197 fptr_t fini; /* Termination function to call */
198
199 u_int32_t mainprog:1, /* True if this is the main program */
200 rtld:1, /* True if this is the dynamic linker */
201 textrel:1, /* True if there are relocations to
202 * text seg */
203 symbolic:1, /* True if generated with
204 * "-Bsymbolic" */
205 printed:1, /* True if ldd has printed it */
206 isdynamic:1, /* True if this is a pure PIC object */
207 mainref:1, /* True if on _rtld_list_main */
208 globalref:1, /* True if on _rtld_list_global */
209 init_done:1, /* True if .init has been added */
210 init_called:1, /* True if .init function has been
211 * called */
212 fini_called:1, /* True if .fini function has been
213 * called */
214 z_now:1, /* True if object's symbols should be
215 bound immediately */
216 z_nodelete:1, /* True if object should never be
217 unloaded */
218 z_initfirst:1, /* True if object's .init/.fini take
219 * priority over others */
220 z_noopen:1, /* True if object should never be
221 dlopen'ed */
222 phdr_loaded:1, /* Phdr is loaded and doesn't need to
223 * be freed. */
224 #ifdef __alpha__
225 secureplt:1, /* True if PLT is read-only format */
226 #endif
227 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
228 tls_static:1, /* True if static TLS offset
229 * has been allocated */
230 tls_dynamic:1, /* True if any non-static DTV entry
231 * has been allocated */
232 #endif
233 ref_nodel:1, /* Refcount increased to prevent dlclose */
234 sysv_hash:1, /* SysV Hash available */
235 gnu_hash:1; /* GNU Hash available */
236
237 struct link_map linkmap; /* for the debugger */
238
239 /* These items are computed by map_object() or by digest_phdr(). */
240 const char *interp; /* Pathname of the interpreter, if any */
241 Objlist dldags; /* Object belongs to these dlopened DAGs (%) */
242 Objlist dagmembers; /* DAG has these members (%) */
243 dev_t dev; /* Object's filesystem's device */
244 ino_t ino; /* Object's inode number */
245
246 void *ehdr;
247
248 /* SysV Hash fields */
249 uint32_t nbuckets; /* Number of buckets */
250 uint32_t nbuckets_m; /* Precomputed for fast remainder */
251 uint8_t nbuckets_s1;
252 uint8_t nbuckets_s2;
253
254 /* GNU Hash fields */
255 const uint32_t *buckets_gnu; /* Hash table buckets array */
256 uint32_t nbuckets_gnu; /* Number of GNU hash buckets */
257 uint32_t nbuckets_m_gnu; /* Precomputed for fast remainder */
258 uint8_t nbuckets_s1_gnu;
259 uint8_t nbuckets_s2_gnu;
260 const uint32_t *chains_gnu; /* Hash table chain array */
261 #define nchains_gnu nchains /* Number of symbols, shared with SysV Hash */
262 const Elf_Addr *bloom_gnu;
263 uint32_t symndx_gnu; /* First accessible symbol on dynsym table */
264 uint32_t mask_bm_gnu; /* Bloom filter words - 1 (bitmask) */
265 uint32_t shift2_gnu; /* Bloom filter shift count */
266
267 size_t pathlen; /* Pathname length */
268 SIMPLEQ_HEAD(, Struct_Name_Entry) names; /* List of names for this
269 * object we know about. */
270
271 #ifdef __powerpc__
272 #ifdef _LP64
273 Elf_Addr glink; /* global linkage */
274 #else
275 Elf_Addr *gotptr; /* GOT table (secure-plt only) */
276 #endif
277 #endif
278
279 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
280 /* Thread Local Storage support for this module */
281 size_t tlsindex; /* Index in DTV */
282 void *tlsinit; /* Base address of TLS init block */
283 size_t tlsinitsize; /* Size of TLS init block */
284 size_t tlssize; /* Size of TLS block */
285 size_t tlsoffset; /* Offset in the static TLS block */
286 size_t tlsalign; /* Needed alignment for static TLS */
287 #endif
288
289 #ifdef GNU_RELRO
290 /* relocation readonly */
291 void *relro_page;
292 size_t relro_size;
293 #endif
294
295 /* symbol versioning */
296 const Elf_Verneed *verneed; /* Required versions. */
297 Elf_Word verneednum; /* Number of entries in verneed table */
298 const Elf_Verdef *verdef; /* Provided versions. */
299 Elf_Word verdefnum; /* Number of entries in verdef table */
300 const Elf_Versym *versyms; /* Symbol versions table */
301
302 Ver_Entry *vertab; /* Versions required/defined by this
303 * object */
304 int vertabnum; /* Number of entries in vertab */
305
306 /* init_array/fini_array */
307 fptr_t *init_array; /* start of init array */
308 size_t init_arraysz; /* # of entries in it */
309 fptr_t *fini_array; /* start of fini array */
310 size_t fini_arraysz; /* # of entries in it */
311 /* IRELATIVE relocations */
312 size_t ifunc_remaining;
313 #if \
314 defined(__aarch64__) || \
315 defined(__arm__) || \
316 defined(__i386__) || \
317 defined(__powerpc__) || \
318 defined(__sparc__) || \
319 defined(__x86_64__)
320 #define IFUNC_NONPLT
321 /* On SPARC, the PLT variant is called JMP_IREL and counted above. */
322 size_t ifunc_remaining_nonplt;
323 #endif
324 size_t cxa_refcount; /* For TLS destructors. */
325 #ifdef __ARM_EABI__
326 void *exidx_start;
327 size_t exidx_sz;
328 #endif
329 } Obj_Entry;
330
331 typedef struct Struct_DoneList {
332 const Obj_Entry **objs; /* Array of object pointers */
333 unsigned int num_alloc; /* Allocated size of the array */
334 unsigned int num_used; /* Number of array slots used */
335 } DoneList;
336
337
338 #if defined(_RTLD_SOURCE)
339
340 extern struct r_debug _rtld_debug;
341 extern Search_Path *_rtld_default_paths;
342 extern Obj_Entry *_rtld_objlist;
343 extern Obj_Entry **_rtld_objtail;
344 extern u_int _rtld_objcount;
345 extern u_int _rtld_objloads;
346 extern const uintptr_t _rtld_compat_obj[];
347 extern Obj_Entry *_rtld_objmain;
348 extern Obj_Entry _rtld_objself;
349 extern Search_Path *_rtld_paths;
350 extern Library_Xform *_rtld_xforms;
351 extern bool _rtld_trust;
352 extern Objlist _rtld_list_global;
353 extern Objlist _rtld_list_main;
354 extern Elf_Sym _rtld_sym_zero;
355 extern u_int _rtld_objgen;
356
357 #define RTLD_MODEMASK 0x3
358
359 /* Flags to be passed into _rtld_symlook_ family of functions. */
360 #define SYMLOOK_IN_PLT 0x01 /* Lookup for PLT symbol */
361 #define SYMLOOK_DLSYM 0x02 /* Return newest versioned symbol.
362 Used by dlsym. */
363
364 /* Flags for _rtld_load_object() and friends. */
365 #define _RTLD_GLOBAL 0x01 /* Add object to global DAG. */
366 #define _RTLD_MAIN 0x02
367 #define _RTLD_NOLOAD 0x04 /* dlopen() specified RTLD_NOLOAD. */
368 #define _RTLD_DLOPEN 0x08 /* Load_object() called from dlopen(). */
369
370 /* Preallocation for static TLS model */
371 #define RTLD_STATIC_TLS_RESERVATION 64
372
373 /* rtld.c */
374 __dso_public char *dlerror(void);
375 __dso_public void *dlopen(const char *, int);
376 __dso_public void *dlsym(void *, const char *);
377 __dso_public int dlclose(void *);
378 __dso_public int dladdr(const void *, Dl_info *);
379 __dso_public int dlinfo(void *, int, void *);
380 __dso_public int dl_iterate_phdr(int (*)(struct dl_phdr_info *, size_t, void *),
381 void *);
382
383 __dso_public void *_dlauxinfo(void) __pure;
384 __dso_public void __dl_cxa_refcount(void *addr, ssize_t delta);
385
386 __dso_public pid_t __locked_fork(int *);
387
388 #if defined(__ARM_EABI__) && !defined(__ARM_DWARF_EH__)
389 /*
390 * This is used by libgcc to find the start and length of the exception table
391 * associated with a PC.
392 */
393 __dso_public _Unwind_Ptr __gnu_Unwind_Find_exidx(_Unwind_Ptr, int *);
394 #endif
395
396 /* These aren't exported */
397 void _rtld_error(const char *, ...) __printflike(1,2);
398 void _rtld_die(void) __dead;
399 void *_rtld_objmain_sym(const char *);
400 __dso_public void _rtld_debug_state(void) __noinline;
401 void _rtld_linkmap_add(Obj_Entry *);
402 void _rtld_linkmap_delete(Obj_Entry *);
403 void _rtld_objlist_push_head(Objlist *, Obj_Entry *);
404 void _rtld_objlist_push_tail(Objlist *, Obj_Entry *);
405 Objlist_Entry *_rtld_objlist_find(Objlist *, const Obj_Entry *);
406 void _rtld_ref_dag(Obj_Entry *);
407
408 void _rtld_shared_enter(void);
409 void _rtld_shared_exit(void);
410 void _rtld_exclusive_enter(sigset_t *);
411 void _rtld_exclusive_exit(sigset_t *);
412
413 int _rtld_relro(const Obj_Entry *, bool);
414
415 /* expand.c */
416 size_t _rtld_expand_path(char *, size_t, const char *, const char *,\
417 const char *);
418
419 /* headers.c */
420 void _rtld_digest_dynamic(const char *, Obj_Entry *);
421 Obj_Entry *_rtld_digest_phdr(const Elf_Phdr *, int, caddr_t);
422
423 /* load.c */
424 Obj_Entry *_rtld_load_object(const char *, int);
425 int _rtld_load_needed_objects(Obj_Entry *, int);
426 int _rtld_preload(const char *);
427
428 #define OBJ_ERR (Obj_Entry *)(-1)
429 /* path.c */
430 void _rtld_add_paths(const char *, Search_Path **, const char *);
431 void _rtld_process_hints(const char *, Search_Path **, Library_Xform **,
432 const char *);
433 int _rtld_sysctl(const char *, void *, size_t *);
434
435 /* reloc.c */
436 int _rtld_do_copy_relocations(const Obj_Entry *);
437 int _rtld_relocate_objects(Obj_Entry *, bool);
438 int _rtld_relocate_nonplt_objects(Obj_Entry *);
439 int _rtld_relocate_plt_lazy(Obj_Entry *);
440 int _rtld_relocate_plt_objects(const Obj_Entry *);
441 void _rtld_setup_pltgot(const Obj_Entry *);
442 Elf_Addr _rtld_resolve_ifunc(const Obj_Entry *, const Elf_Sym *);
443 Elf_Addr _rtld_resolve_ifunc2(const Obj_Entry *, Elf_Addr);
444
445 void _rtld_call_ifunc(Obj_Entry *, sigset_t *, u_int);
446
447 /* search.c */
448 Obj_Entry *_rtld_load_library(const char *, const Obj_Entry *, int);
449
450 /* symbol.c */
451 const Elf_Sym *_rtld_symlook_obj(const char *, Elf_Hash *,
452 const Obj_Entry *, u_int, const Ver_Entry *);
453 const Elf_Sym *_rtld_find_symdef(unsigned long, const Obj_Entry *,
454 const Obj_Entry **, u_int);
455 const Elf_Sym *_rtld_find_plt_symdef(unsigned long, const Obj_Entry *,
456 const Obj_Entry **, bool);
457
458 const Elf_Sym *_rtld_symlook_list(const char *, Elf_Hash *,
459 const Objlist *, const Obj_Entry **, u_int, const Ver_Entry *, DoneList *);
460 const Elf_Sym *_rtld_symlook_default(const char *, Elf_Hash *,
461 const Obj_Entry *, const Obj_Entry **, u_int, const Ver_Entry *);
462 const Elf_Sym *_rtld_symlook_needed(const char *, Elf_Hash *,
463 const Needed_Entry *, const Obj_Entry **, u_int, const Ver_Entry *,
464 DoneList *, DoneList *);
465
466 /* symver.c */
467 void _rtld_object_add_name(Obj_Entry *, const char *);
468 int _rtld_object_match_name(const Obj_Entry *, const char *);
469 int _rtld_verify_object_versions(Obj_Entry *);
470
471 static __inline const Ver_Entry *
_rtld_fetch_ventry(const Obj_Entry * obj,unsigned long symnum)472 _rtld_fetch_ventry(const Obj_Entry *obj, unsigned long symnum)
473 {
474 Elf_Half vernum;
475
476 if (obj->vertab) {
477 vernum = VER_NDX(obj->versyms[symnum].vs_vers);
478 if (vernum >= obj->vertabnum) {
479 _rtld_error("%s: symbol %s has wrong verneed value %d",
480 obj->path, &obj->strtab[symnum], vernum);
481 } else if (obj->vertab[vernum].hash) {
482 return &obj->vertab[vernum];
483 }
484 }
485 return NULL;
486 }
487
488 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
489 /* tls.c */
490 void *_rtld_tls_get_addr(void *, size_t, size_t);
491 void _rtld_tls_initial_allocation(void);
492 int _rtld_tls_offset_allocate(Obj_Entry *);
493 void _rtld_tls_offset_free(Obj_Entry *);
494
495 extern size_t _rtld_tls_dtv_generation;
496 extern size_t _rtld_tls_max_index;
497
498 __dso_public extern void *__tls_get_addr(void *);
499 #ifdef __i386__
500 __dso_public extern void *___tls_get_addr(void *)
501 __attribute__((__regparm__(1)));
502 #endif
503 #endif
504
505 /* map_object.c */
506 struct stat;
507 Obj_Entry *_rtld_map_object(const char *, int, const struct stat *);
508 void _rtld_obj_free(Obj_Entry *);
509 Obj_Entry *_rtld_obj_new(void);
510
511 #ifdef RTLD_LOADER
512 /* function descriptors */
513 #ifdef __HAVE_FUNCTION_DESCRIPTORS
514 Elf_Addr _rtld_function_descriptor_alloc(const Obj_Entry *,
515 const Elf_Sym *, Elf_Addr);
516 const void *_rtld_function_descriptor_function(const void *);
517
518 Elf_Addr _rtld_call_function_addr(const Obj_Entry *, Elf_Addr);
519 #else
520 static inline Elf_Addr
_rtld_call_function_addr(const Obj_Entry * obj,Elf_Addr addr)521 _rtld_call_function_addr(const Obj_Entry *obj, Elf_Addr addr)
522 {
523 return ((Elf_Addr(*)(void))addr)();
524 }
525 #endif /* __HAVE_FUNCTION_DESCRIPTORS */
526 #endif /* RTLD_LOADER */
527
528 #endif /* _RTLD_SOURCE */
529
530 #endif /* RTLD_H */
531