1 /* $NetBSD: alpha_reloc.c,v 1.23 2002/10/03 20:39:22 mycroft Exp $ */ 2 3 /* 4 * Copyright (c) 2001 Wasabi Systems, Inc. 5 * All rights reserved. 6 * 7 * Written by Jason R. Thorpe for Wasabi Systems, Inc. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. All advertising materials mentioning features or use of this software 18 * must display the following acknowledgement: 19 * This product includes software developed for the NetBSD Project by 20 * Wasabi Systems, Inc. 21 * 4. The name of Wasabi Systems, Inc. may not be used to endorse 22 * or promote products derived from this software without specific prior 23 * written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC 29 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35 * POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38 /* 39 * Copyright 1996, 1997, 1998, 1999 John D. Polstra. 40 * All rights reserved. 41 * 42 * Redistribution and use in source and binary forms, with or without 43 * modification, are permitted provided that the following conditions 44 * are met: 45 * 1. Redistributions of source code must retain the above copyright 46 * notice, this list of conditions and the following disclaimer. 47 * 2. Redistributions in binary form must reproduce the above copyright 48 * notice, this list of conditions and the following disclaimer in the 49 * documentation and/or other materials provided with the distribution. 50 * 51 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 52 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 53 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 54 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 55 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 56 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 57 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 58 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 59 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 60 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 61 */ 62 63 #include <sys/types.h> 64 #include <sys/stat.h> 65 #include <string.h> 66 67 #include "rtld.h" 68 #include "debug.h" 69 70 #ifdef RTLD_DEBUG_ALPHA 71 #define adbg(x) xprintf x 72 #else 73 #define adbg(x) /* nothing */ 74 #endif 75 76 void _rtld_bind_start(void); 77 void _rtld_bind_start_old(void); 78 void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr); 79 caddr_t _rtld_bind __P((const Obj_Entry *, Elf_Word)); 80 81 void 82 _rtld_setup_pltgot(const Obj_Entry *obj) 83 { 84 uint32_t word0; 85 86 /* 87 * The PLTGOT on the Alpha looks like this: 88 * 89 * PLT HEADER 90 * . 91 * . 32 bytes 92 * . 93 * PLT ENTRY #0 94 * . 95 * . 12 bytes 96 * . 97 * PLT ENTRY #1 98 * . 99 * . 12 bytes 100 * . 101 * etc. 102 * 103 * The old-format entries look like (displacements filled in 104 * by the linker): 105 * 106 * ldah $28, 0($31) # 0x279f0000 107 * lda $28, 0($28) # 0x239c0000 108 * br $31, plt0 # 0xc3e00000 109 * 110 * The new-format entries look like: 111 * 112 * br $28, plt0 # 0xc3800000 113 * # 0x00000000 114 * # 0x00000000 115 * 116 * What we do is fetch the first PLT entry and check to 117 * see the first word of it matches the first word of the 118 * old format. If so, we use a binding routine that can 119 * handle the old format, otherwise we use a binding routine 120 * that handles the new format. 121 * 122 * Note that this is done on a per-object basis, we can mix 123 * and match shared objects build with both the old and new 124 * linker. 125 */ 126 word0 = *(uint32_t *)(((char *) obj->pltgot) + 32); 127 if ((word0 & 0xffff0000) == 0x279f0000) { 128 /* Old PLT entry format. */ 129 adbg(("ALPHA: object %p has old PLT format\n", obj)); 130 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start_old; 131 obj->pltgot[3] = (Elf_Addr) obj; 132 } else { 133 /* New PLT entry format. */ 134 adbg(("ALPHA: object %p has new PLT format\n", obj)); 135 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 136 obj->pltgot[3] = (Elf_Addr) obj; 137 } 138 139 __asm __volatile("imb"); 140 } 141 142 /* 143 * It is possible for the compiler to emit relocations for unaligned data. 144 * We handle this situation with these inlines. 145 */ 146 #define RELOC_ALIGNED_P(x) \ 147 (((uintptr_t)(x) & (sizeof(void *) - 1)) == 0) 148 149 static __inline Elf_Addr 150 load_ptr(void *where) 151 { 152 Elf_Addr res; 153 154 memcpy(&res, where, sizeof(res)); 155 156 return (res); 157 } 158 159 static __inline void 160 store_ptr(void *where, Elf_Addr val) 161 { 162 163 memcpy(where, &val, sizeof(val)); 164 } 165 166 void 167 _rtld_relocate_nonplt_self(dynp, relocbase) 168 Elf_Dyn *dynp; 169 Elf_Addr relocbase; 170 { 171 const Elf_Rela *rela = 0, *relalim; 172 Elf_Addr relasz = 0; 173 Elf_Addr *where; 174 175 for (; dynp->d_tag != DT_NULL; dynp++) { 176 switch (dynp->d_tag) { 177 case DT_RELA: 178 rela = (const Elf_Rela *)(relocbase + dynp->d_un.d_ptr); 179 break; 180 case DT_RELASZ: 181 relasz = dynp->d_un.d_val; 182 break; 183 } 184 } 185 relalim = (const Elf_Rela *)((caddr_t)rela + relasz); 186 for (; rela < relalim; rela++) { 187 where = (Elf_Addr *)(relocbase + rela->r_offset); 188 /* XXX For some reason I see a few GLOB_DAT relocs here. */ 189 *where += (Elf_Addr)relocbase; 190 } 191 } 192 193 int 194 _rtld_relocate_nonplt_objects(obj) 195 const Obj_Entry *obj; 196 { 197 const Elf_Rela *rela; 198 #define COMBRELOC 199 #ifdef COMBRELOC 200 unsigned long lastsym = -1; 201 #endif 202 Elf_Addr target; 203 204 for (rela = obj->rela; rela < obj->relalim; rela++) { 205 Elf_Addr *where; 206 const Elf_Sym *def; 207 const Obj_Entry *defobj; 208 Elf_Addr tmp; 209 unsigned long symnum; 210 211 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 212 symnum = ELF_R_SYM(rela->r_info); 213 214 switch (ELF_R_TYPE(rela->r_info)) { 215 case R_TYPE(NONE): 216 break; 217 218 case R_TYPE(REFQUAD): 219 case R_TYPE(GLOB_DAT): 220 #ifdef COMBRELOC 221 if (symnum != lastsym) { 222 #endif 223 def = _rtld_find_symdef(symnum, obj, &defobj, 224 false); 225 if (def == NULL) 226 return -1; 227 target = (Elf_Addr)(defobj->relocbase + 228 def->st_value); 229 #ifdef COMBRELOC 230 lastsym = symnum; 231 } 232 #endif 233 234 tmp = target + rela->r_addend; 235 if (__predict_true(RELOC_ALIGNED_P(where))) { 236 if (*where != tmp) 237 *where = tmp; 238 } else { 239 if (load_ptr(where) != tmp) 240 store_ptr(where, tmp); 241 } 242 rdbg(("REFQUAD/GLOB_DAT %s in %s --> %p in %s", 243 obj->strtab + obj->symtab[symnum].st_name, 244 obj->path, (void *)tmp, defobj->path)); 245 break; 246 247 case R_TYPE(RELATIVE): 248 if (__predict_true(RELOC_ALIGNED_P(where))) 249 *where += (Elf_Addr)obj->relocbase; 250 else 251 store_ptr(where, 252 load_ptr(where) + (Elf_Addr)obj->relocbase); 253 rdbg(("RELATIVE in %s --> %p", obj->path, 254 (void *)*where)); 255 break; 256 257 case R_TYPE(COPY): 258 /* 259 * These are deferred until all other relocations have 260 * been done. All we do here is make sure that the 261 * COPY relocation is not in a shared library. They 262 * are allowed only in executable files. 263 */ 264 if (obj->isdynamic) { 265 _rtld_error( 266 "%s: Unexpected R_COPY relocation in shared library", 267 obj->path); 268 return -1; 269 } 270 rdbg(("COPY (avoid in main)")); 271 break; 272 273 default: 274 rdbg(("sym = %lu, type = %lu, offset = %p, " 275 "addend = %p, contents = %p, symbol = %s", 276 symnum, (u_long)ELF_R_TYPE(rela->r_info), 277 (void *)rela->r_offset, (void *)rela->r_addend, 278 (void *)load_ptr(where), 279 obj->strtab + obj->symtab[symnum].st_name)); 280 _rtld_error("%s: Unsupported relocation type %ld " 281 "in non-PLT relocations\n", 282 obj->path, (u_long) ELF_R_TYPE(rela->r_info)); 283 return -1; 284 } 285 } 286 return 0; 287 } 288 289 int 290 _rtld_relocate_plt_lazy(obj) 291 const Obj_Entry *obj; 292 { 293 const Elf_Rela *rela; 294 295 if (!obj->relocbase) 296 return 0; 297 298 for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) { 299 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 300 301 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 302 303 /* Just relocate the GOT slots pointing into the PLT */ 304 *where += (Elf_Addr)obj->relocbase; 305 rdbg(("fixup !main in %s --> %p", obj->path, (void *)*where)); 306 } 307 308 return 0; 309 } 310 311 caddr_t 312 _rtld_bind(obj, reloff) 313 const Obj_Entry *obj; 314 Elf_Word reloff; 315 { 316 const Elf_Rela *rela = (const Elf_Rela *)((caddr_t)obj->pltrela + reloff); 317 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 318 Elf_Addr new_value; 319 const Elf_Sym *def; 320 const Obj_Entry *defobj; 321 Elf_Addr stubaddr; 322 323 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 324 325 def = _rtld_find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, true); 326 if (def == NULL) 327 _rtld_die(); 328 329 new_value = (Elf_Addr)(defobj->relocbase + def->st_value); 330 rdbg(("bind now/fixup in %s --> old=%p new=%p", 331 defobj->strtab + def->st_name, (void *)*where, (void *)new_value)); 332 333 if ((stubaddr = *where) != new_value) { 334 int64_t delta, idisp; 335 uint32_t insn[3], *stubptr; 336 int insncnt; 337 Elf_Addr pc; 338 339 /* Point this GOT entry at the target. */ 340 *where = new_value; 341 342 /* 343 * Alpha shared objects may have multiple GOTs, each 344 * of which may point to this entry in the PLT. But, 345 * we only have a reference to the first GOT entry which 346 * points to this PLT entry. In order to avoid having to 347 * re-bind this call every time a non-first GOT entry is 348 * used, we will attempt to patch up the PLT entry to 349 * reference the target, rather than the binder. 350 * 351 * When the PLT stub gets control, PV contains the address 352 * of the PLT entry. Each PLT entry has room for 3 insns. 353 * If the displacement of the target from PV fits in a signed 354 * 32-bit integer, we can simply add it to PV. Otherwise, 355 * we must load the GOT entry itself into PV. 356 * 357 * Note if the shared object uses the old PLT format, then 358 * we cannot patch up the PLT safely, and so we skip it 359 * in that case[*]. 360 * 361 * [*] Actually, if we're not doing lazy-binding, then 362 * we *can* (and do) patch up this PLT entry; the PLTGOT 363 * thunk won't yet point to any binder entry point, and 364 * so this test will fail as it would for the new PLT 365 * entry format. 366 */ 367 if (obj->pltgot[2] == (Elf_Addr) &_rtld_bind_start_old) { 368 rdbg((" old PLT format")); 369 goto out; 370 } 371 372 delta = new_value - stubaddr; 373 rdbg((" stubaddr=%p, where-stubaddr=%ld, delta=%ld", 374 (void *)stubaddr, (long)where - (long)stubaddr, 375 (long)delta)); 376 insncnt = 0; 377 if ((int32_t)delta == delta) { 378 /* 379 * We can adjust PV with an LDA, LDAH sequence. 380 * 381 * First, build an LDA insn to adjust the low 16 382 * bits. 383 */ 384 insn[insncnt++] = 0x08 << 26 | 27 << 21 | 27 << 16 | 385 (delta & 0xffff); 386 rdbg((" LDA $27,%d($27)", (int16_t)delta)); 387 /* 388 * Adjust the delta to account for the effects of 389 * the LDA, including sign-extension. 390 */ 391 delta -= (int16_t)delta; 392 if (delta != 0) { 393 /* 394 * Build an LDAH instruction to adjust the 395 * high 16 bits. 396 */ 397 insn[insncnt++] = 0x09 << 26 | 27 << 21 | 398 27 << 16 | ((delta >> 16) & 0xffff); 399 rdbg((" LDAH $27,%d($27)", 400 (int16_t)(delta >> 16))); 401 } 402 } else { 403 int64_t dhigh; 404 405 /* We must load the GOT entry. */ 406 delta = (Elf_Addr)where - stubaddr; 407 408 /* 409 * If the GOT entry is too far away from the PLT 410 * entry, then we can't patch up the PLT entry. 411 * This PLT entry will have to be bound for each 412 * GOT entry except for the first one. This program 413 * will still run, albeit very slowly. It is very 414 * unlikely that this case will ever happen in 415 * practice. 416 */ 417 if ((int32_t)delta != delta) { 418 rdbg((" PLT stub too far from GOT to relocate")); 419 goto out; 420 } 421 dhigh = delta - (int16_t)delta; 422 if (dhigh != 0) { 423 /* 424 * Build an LDAH instruction to adjust the 425 * high 16 bits. 426 */ 427 insn[insncnt++] = 0x09 << 26 | 27 << 21 | 428 27 << 16 | ((dhigh >> 16) & 0xffff); 429 rdbg((" LDAH $27,%d($27)", 430 (int16_t)(dhigh >> 16))); 431 } 432 /* Build an LDQ to load the GOT entry. */ 433 insn[insncnt++] = 0x29 << 26 | 27 << 21 | 434 27 << 16 | (delta & 0xffff); 435 rdbg((" LDQ $27,%d($27)", 436 (int16_t)delta)); 437 } 438 439 /* 440 * Now, build a JMP or BR insn to jump to the target. If 441 * the displacement fits in a sign-extended 21-bit field, 442 * we can use the more efficient BR insn. Otherwise, we 443 * have to jump indirect through PV. 444 */ 445 pc = stubaddr + (4 * (insncnt + 1)); 446 idisp = (int64_t)(new_value - pc) >> 2; 447 if (-0x100000 <= idisp && idisp < 0x100000) { 448 insn[insncnt++] = 0x30 << 26 | 31 << 21 | 449 (idisp & 0x1fffff); 450 rdbg((" BR $31,%p", (void *)new_value)); 451 } else { 452 insn[insncnt++] = 0x1a << 26 | 31 << 21 | 453 27 << 16 | (idisp & 0x3fff); 454 rdbg((" JMP $31,($27),%d", 455 (int)(idisp & 0x3fff))); 456 } 457 458 /* 459 * Fill in the tail of the PLT entry first, for reentrancy. 460 * Until we have overwritten the first insn (an unconditional 461 * branch), the remaining insns have no effect. 462 */ 463 stubptr = (uint32_t *)stubaddr; 464 while (insncnt > 1) { 465 insncnt--; 466 stubptr[insncnt] = insn[insncnt]; 467 } 468 /* 469 * Commit the tail of the insn sequence to memory 470 * before overwriting the first insn. 471 */ 472 __asm __volatile("wmb" ::: "memory"); 473 stubptr[0] = insn[0]; 474 /* 475 * I-stream will be sync'd when we either return from 476 * the binder (lazy bind case) or when the PLTGOT thunk 477 * is patched up (bind-now case). 478 */ 479 } 480 481 out: 482 return (caddr_t)new_value; 483 } 484