reloc.c revision 1.119
1 /* $NetBSD: reloc.c,v 1.119 2025/04/18 02:16:16 riastradh Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt (at) 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 /* 35 * Dynamic linker for ELF. 36 * 37 * John Polstra <jdp (at) polstra.com>. 38 */ 39 40 #include <sys/cdefs.h> 41 #ifndef lint 42 __RCSID("$NetBSD: reloc.c,v 1.119 2025/04/18 02:16:16 riastradh Exp $"); 43 #endif /* not lint */ 44 45 #include <err.h> 46 #include <errno.h> 47 #include <fcntl.h> 48 #include <stdarg.h> 49 #include <stdio.h> 50 #include <stdlib.h> 51 #include <string.h> 52 #include <unistd.h> 53 #include <sys/types.h> 54 #include <sys/mman.h> 55 #include <sys/bitops.h> 56 #include <dirent.h> 57 58 #include "debug.h" 59 #include "hash.h" 60 #include "rtld.h" 61 62 #ifndef RTLD_INHIBIT_COPY_RELOCS 63 static int _rtld_do_copy_relocation(const Obj_Entry *, const Elf_Rela *); 64 65 static int 66 _rtld_do_copy_relocation(const Obj_Entry *dstobj, const Elf_Rela *rela) 67 { 68 void *dstaddr = (void *)(dstobj->relocbase + rela->r_offset); 69 const Elf_Sym *dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 70 const char *name = dstobj->strtab + dstsym->st_name; 71 Elf_Hash hash; 72 size_t size = dstsym->st_size; 73 const void *srcaddr; 74 const Elf_Sym *srcsym = NULL; 75 Obj_Entry *srcobj; 76 77 hash.sysv = _rtld_sysv_hash(name); 78 hash.gnu = _rtld_gnu_hash(name); 79 80 if (__predict_false(size == 0)) { 81 #if defined(__powerpc__) && !defined(__LP64) /* PR port-macppc/47464 */ 82 if (strcmp(name, "_SDA_BASE_") == 0 83 || strcmp(name, "_SDA2_BASE_") == 0) 84 { 85 rdbg(("COPY %s %s --> ignoring old binutils bug", 86 dstobj->path, name)); 87 return 0; 88 } 89 #endif 90 #if 0 /* shall we warn? */ 91 xwarnx("%s: zero size COPY relocation for \"%s\"", 92 dstobj->path, name); 93 #endif 94 } 95 96 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) { 97 srcsym = _rtld_symlook_obj(name, &hash, srcobj, 0, 98 _rtld_fetch_ventry(dstobj, ELF_R_SYM(rela->r_info))); 99 if (srcsym != NULL) 100 break; 101 } 102 103 if (srcobj == NULL) { 104 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 105 " relocation in %s", name, dstobj->path); 106 return (-1); 107 } 108 srcaddr = (const void *)(srcobj->relocbase + srcsym->st_value); 109 rdbg(("COPY %s %s %s --> src=%p dst=%p size %ld", 110 dstobj->path, srcobj->path, name, srcaddr, 111 (void *)dstaddr, (long)size)); 112 (void)memcpy(dstaddr, srcaddr, size); 113 return (0); 114 } 115 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 116 117 118 /* 119 * Process the special R_xxx_COPY relocations in the main program. These 120 * copy data from a shared object into a region in the main program's BSS 121 * segment. 122 * 123 * Returns 0 on success, -1 on failure. 124 */ 125 int 126 _rtld_do_copy_relocations(const Obj_Entry *dstobj) 127 { 128 #ifndef RTLD_INHIBIT_COPY_RELOCS 129 130 /* COPY relocations are invalid elsewhere */ 131 assert(!dstobj->isdynamic); 132 133 if (dstobj->rel != NULL) { 134 const Elf_Rel *rel; 135 for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) { 136 if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) { 137 Elf_Rela ourrela; 138 ourrela.r_info = rel->r_info; 139 ourrela.r_offset = rel->r_offset; 140 ourrela.r_addend = 0; 141 if (_rtld_do_copy_relocation(dstobj, 142 &ourrela) < 0) 143 return (-1); 144 } 145 } 146 } 147 if (dstobj->rela != NULL) { 148 const Elf_Rela *rela; 149 for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) { 150 if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) { 151 if (_rtld_do_copy_relocation(dstobj, rela) < 0) 152 return (-1); 153 } 154 } 155 } 156 #ifdef GNU_RELRO 157 /* 158 * If the main program is lazily bound (default -- whether or 159 * not LD_BINDNOW is set in the calling environment), we are 160 * now done writing to anything covered by RELRO and we can 161 * safely make it read-only. There may still be ifunc 162 * resolution to do later; it will happen in a read/write 163 * segment and will not be made read-only. 164 * 165 * But if the main program is eagerly bound (i.e., the object 166 * has DF_1_NOW set in DT_FLAGS_1, whether or not LD_BIND_NOW 167 * is set in the calling environment), we delay protecting the 168 * RELRO region as read-only until we have resolved ifuncs -- 169 * at which point we will make the ifunc resolution read-only 170 * too. 171 */ 172 if (!dstobj->z_now && _rtld_relro(dstobj, true) == -1) 173 return -1; 174 #endif 175 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 176 177 return (0); 178 } 179 180 /* 181 * Relocate newly-loaded shared objects. The argument is a pointer to 182 * the Obj_Entry for the first such object. All objects from the first 183 * to the end of the list of objects are relocated. Returns 0 on success, 184 * or -1 on failure. 185 */ 186 int 187 _rtld_relocate_objects(Obj_Entry *first, bool bind_now) 188 { 189 Obj_Entry *obj; 190 int ok = 1; 191 192 for (obj = first; obj != NULL; obj = obj->next) { 193 if ((!obj->sysv_hash && !obj->gnu_hash) || 194 obj->symtab == NULL || obj->strtab == NULL) { 195 _rtld_error("%s: Shared object has no run-time" 196 " symbol table", obj->path); 197 return -1; 198 } 199 if (obj->nbuckets == UINT32_MAX) { 200 _rtld_error("%s: Symbol table too large", obj->path); 201 return -1; 202 } 203 rdbg((" relocating %s (%ld/%ld rel/rela, %ld/%ld plt rel/rela)", 204 obj->path, 205 (long)(obj->rellim - obj->rel), 206 (long)(obj->relalim - obj->rela), 207 (long)(obj->pltrellim - obj->pltrel), 208 (long)(obj->pltrelalim - obj->pltrela))); 209 210 if (obj->textrel) { 211 xwarnx("%s: text relocations", obj->path); 212 /* 213 * There are relocations to the write-protected text 214 * segment. 215 */ 216 if (mprotect(obj->mapbase, obj->textsize, 217 PROT_READ | PROT_WRITE) == -1) { 218 _rtld_error("%s: Cannot write-enable text " 219 "segment: %s", obj->path, xstrerror(errno)); 220 return -1; 221 } 222 } 223 dbg(("doing non-PLT relocations")); 224 if (_rtld_relocate_nonplt_objects(obj) < 0) 225 ok = 0; 226 if (obj->textrel) { /* Re-protected the text segment. */ 227 if (mprotect(obj->mapbase, obj->textsize, 228 PROT_READ | PROT_EXEC) == -1) { 229 _rtld_error("%s: Cannot write-protect text " 230 "segment: %s", obj->path, xstrerror(errno)); 231 return -1; 232 } 233 } 234 dbg(("doing lazy PLT binding")); 235 if (_rtld_relocate_plt_lazy(obj) < 0) 236 ok = 0; 237 if (obj->z_now || bind_now) { 238 dbg(("doing immediate PLT binding")); 239 if (_rtld_relocate_plt_objects(obj) < 0) 240 ok = 0; 241 } 242 if (!ok) 243 return -1; 244 245 dbg(("fixing up PLTGOT")); 246 /* Set the special PLTGOT entries. */ 247 if (obj->pltgot != NULL) 248 _rtld_setup_pltgot(obj); 249 #ifdef GNU_RELRO 250 if (_rtld_relro(obj, false) == -1) 251 return -1; 252 #endif 253 } 254 return 0; 255 } 256 257 Elf_Addr 258 _rtld_resolve_ifunc(const Obj_Entry *obj, const Elf_Sym *def) 259 { 260 Elf_Addr target; 261 262 _rtld_shared_exit(); 263 target = _rtld_resolve_ifunc2(obj, 264 (Elf_Addr)obj->relocbase + def->st_value); 265 _rtld_shared_enter(); 266 return target; 267 } 268 269 Elf_Addr 270 _rtld_resolve_ifunc2(const Obj_Entry *obj, Elf_Addr addr) 271 { 272 Elf_Addr target; 273 274 target = _rtld_call_function_addr(obj, addr); 275 276 return target; 277 } 278 279 #if \ 280 !defined(RTLD_COMMON_CALL_IFUNC_RELA) && \ 281 !defined(RTLD_COMMON_CALL_IFUNC_REL) && \ 282 !defined(RTLD_ARCH_CALL_IFUNC) 283 void 284 _rtld_call_ifunc(Obj_Entry *obj, sigset_t *mask, u_int cur_objgen) 285 { 286 } 287 #endif 288 289 #ifdef RTLD_COMMON_CALL_IFUNC_RELA 290 # ifdef __sparc__ 291 # include <machine/elf_support.h> 292 # endif 293 294 void 295 _rtld_call_ifunc(Obj_Entry *obj, sigset_t *mask, u_int cur_objgen) 296 { 297 const Elf_Rela *rela; 298 Elf_Addr *where; 299 #ifdef __sparc__ 300 Elf_Word *where2; 301 #endif 302 Elf_Addr target; 303 304 while (obj->ifunc_remaining > 0 && _rtld_objgen == cur_objgen) { 305 rela = obj->pltrelalim - obj->ifunc_remaining--; 306 #ifdef __sparc__ 307 #define PLT_IRELATIVE R_TYPE(JMP_IREL) 308 #else 309 #define PLT_IRELATIVE R_TYPE(IRELATIVE) 310 #endif 311 if (ELF_R_TYPE(rela->r_info) != PLT_IRELATIVE) 312 continue; 313 #ifdef __sparc__ 314 where2 = (Elf_Word *)(obj->relocbase + rela->r_offset); 315 #else 316 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 317 #endif 318 target = (Elf_Addr)(obj->relocbase + rela->r_addend); 319 _rtld_exclusive_exit(mask); 320 target = _rtld_resolve_ifunc2(obj, target); 321 _rtld_exclusive_enter(mask); 322 #ifdef __sparc__ 323 sparc_write_branch(where2 + 1, (void *)target); 324 #else 325 if (*where != target) 326 *where = target; 327 #endif 328 } 329 330 while (obj->ifunc_remaining_nonplt > 0 && _rtld_objgen == cur_objgen) { 331 rela = obj->relalim - obj->ifunc_remaining_nonplt--; 332 if (ELF_R_TYPE(rela->r_info) != R_TYPE(IRELATIVE)) 333 continue; 334 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 335 target = (Elf_Addr)(obj->relocbase + rela->r_addend); 336 _rtld_exclusive_exit(mask); 337 target = _rtld_resolve_ifunc2(obj, target); 338 _rtld_exclusive_enter(mask); 339 if (*where != target) 340 *where = target; 341 } 342 } 343 #endif 344 345 #ifdef RTLD_COMMON_CALL_IFUNC_REL 346 void 347 _rtld_call_ifunc(Obj_Entry *obj, sigset_t *mask, u_int cur_objgen) 348 { 349 const Elf_Rel *rel; 350 Elf_Addr *where, target; 351 352 while (obj->ifunc_remaining > 0 && _rtld_objgen == cur_objgen) { 353 rel = obj->pltrellim - obj->ifunc_remaining; 354 --obj->ifunc_remaining; 355 if (ELF_R_TYPE(rel->r_info) == R_TYPE(IRELATIVE)) { 356 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 357 _rtld_exclusive_exit(mask); 358 target = _rtld_resolve_ifunc2(obj, *where); 359 _rtld_exclusive_enter(mask); 360 if (*where != target) 361 *where = target; 362 } 363 } 364 365 while (obj->ifunc_remaining_nonplt > 0 && _rtld_objgen == cur_objgen) { 366 rel = obj->rellim - obj->ifunc_remaining_nonplt--; 367 if (ELF_R_TYPE(rel->r_info) == R_TYPE(IRELATIVE)) { 368 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 369 _rtld_exclusive_exit(mask); 370 target = _rtld_resolve_ifunc2(obj, *where); 371 _rtld_exclusive_enter(mask); 372 if (*where != target) 373 *where = target; 374 } 375 } 376 } 377 #endif 378
Indexes created Tue Sep 30 11:09:46 GMT 2025