alpha_reloc.c revision 1.29
1/* $NetBSD: alpha_reloc.c,v 1.29 2005/12/24 20:59:30 perry 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/cdefs.h> 64#ifndef lint 65__RCSID("$NetBSD: alpha_reloc.c,v 1.29 2005/12/24 20:59:30 perry Exp $"); 66#endif /* not lint */ 67 68#include <sys/types.h> 69#include <sys/stat.h> 70#include <string.h> 71 72#include "rtld.h" 73#include "debug.h" 74 75#ifdef RTLD_DEBUG_ALPHA 76#define adbg(x) xprintf x 77#else 78#define adbg(x) /* nothing */ 79#endif 80 81void _rtld_bind_start(void); 82void _rtld_bind_start_old(void); 83void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr); 84caddr_t _rtld_bind(const Obj_Entry *, Elf_Word); 85static inline int _rtld_relocate_plt_object(const Obj_Entry *, 86 const Elf_Rela *, Elf_Addr *); 87 88void 89_rtld_setup_pltgot(const Obj_Entry *obj) 90{ 91 uint32_t word0; 92 93 /* 94 * The PLTGOT on the Alpha looks like this: 95 * 96 * PLT HEADER 97 * . 98 * . 32 bytes 99 * . 100 * PLT ENTRY #0 101 * . 102 * . 12 bytes 103 * . 104 * PLT ENTRY #1 105 * . 106 * . 12 bytes 107 * . 108 * etc. 109 * 110 * The old-format entries look like (displacements filled in 111 * by the linker): 112 * 113 * ldah $28, 0($31) # 0x279f0000 114 * lda $28, 0($28) # 0x239c0000 115 * br $31, plt0 # 0xc3e00000 116 * 117 * The new-format entries look like: 118 * 119 * br $28, plt0 # 0xc3800000 120 * # 0x00000000 121 * # 0x00000000 122 * 123 * What we do is fetch the first PLT entry and check to 124 * see the first word of it matches the first word of the 125 * old format. If so, we use a binding routine that can 126 * handle the old format, otherwise we use a binding routine 127 * that handles the new format. 128 * 129 * Note that this is done on a per-object basis, we can mix 130 * and match shared objects build with both the old and new 131 * linker. 132 */ 133 word0 = *(uint32_t *)(((char *) obj->pltgot) + 32); 134 if ((word0 & 0xffff0000) == 0x279f0000) { 135 /* Old PLT entry format. */ 136 adbg(("ALPHA: object %p has old PLT format\n", obj)); 137 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start_old; 138 obj->pltgot[3] = (Elf_Addr) obj; 139 } else { 140 /* New PLT entry format. */ 141 adbg(("ALPHA: object %p has new PLT format\n", obj)); 142 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 143 obj->pltgot[3] = (Elf_Addr) obj; 144 } 145 146 __asm volatile("imb"); 147} 148 149/* 150 * It is possible for the compiler to emit relocations for unaligned data. 151 * We handle this situation with these inlines. 152 */ 153#define RELOC_ALIGNED_P(x) \ 154 (((uintptr_t)(x) & (sizeof(void *) - 1)) == 0) 155 156static inline Elf_Addr 157load_ptr(void *where) 158{ 159 Elf_Addr res; 160 161 memcpy(&res, where, sizeof(res)); 162 163 return (res); 164} 165 166static inline void 167store_ptr(void *where, Elf_Addr val) 168{ 169 170 memcpy(where, &val, sizeof(val)); 171} 172 173void 174_rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase) 175{ 176 const Elf_Rela *rela = 0, *relalim; 177 Elf_Addr relasz = 0; 178 Elf_Addr *where; 179 180 for (; dynp->d_tag != DT_NULL; dynp++) { 181 switch (dynp->d_tag) { 182 case DT_RELA: 183 rela = (const Elf_Rela *)(relocbase + dynp->d_un.d_ptr); 184 break; 185 case DT_RELASZ: 186 relasz = dynp->d_un.d_val; 187 break; 188 } 189 } 190 relalim = (const Elf_Rela *)((caddr_t)rela + relasz); 191 for (; rela < relalim; rela++) { 192 where = (Elf_Addr *)(relocbase + rela->r_offset); 193 /* XXX For some reason I see a few GLOB_DAT relocs here. */ 194 *where += (Elf_Addr)relocbase; 195 } 196} 197 198int 199_rtld_relocate_nonplt_objects(const Obj_Entry *obj) 200{ 201 const Elf_Rela *rela; 202#define COMBRELOC 203#ifdef COMBRELOC 204 unsigned long lastsym = -1; 205#endif 206 Elf_Addr target = -1; 207 208 for (rela = obj->rela; rela < obj->relalim; rela++) { 209 Elf_Addr *where; 210 const Elf_Sym *def; 211 const Obj_Entry *defobj; 212 Elf_Addr tmp; 213 unsigned long symnum; 214 215 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 216 symnum = ELF_R_SYM(rela->r_info); 217 218 switch (ELF_R_TYPE(rela->r_info)) { 219 case R_TYPE(NONE): 220 break; 221 222 case R_TYPE(REFQUAD): 223 case R_TYPE(GLOB_DAT): 224#ifdef COMBRELOC 225 if (symnum != lastsym) { 226#endif 227 def = _rtld_find_symdef(symnum, obj, &defobj, 228 false); 229 if (def == NULL) 230 return -1; 231 target = (Elf_Addr)(defobj->relocbase + 232 def->st_value); 233#ifdef COMBRELOC 234 lastsym = symnum; 235 } 236#endif 237 238 tmp = target + rela->r_addend; 239 if (__predict_true(RELOC_ALIGNED_P(where))) { 240 if (*where != tmp) 241 *where = tmp; 242 } else { 243 if (load_ptr(where) != tmp) 244 store_ptr(where, tmp); 245 } 246 rdbg(("REFQUAD/GLOB_DAT %s in %s --> %p in %s", 247 obj->strtab + obj->symtab[symnum].st_name, 248 obj->path, (void *)tmp, defobj->path)); 249 break; 250 251 case R_TYPE(RELATIVE): 252 if (__predict_true(RELOC_ALIGNED_P(where))) 253 *where += (Elf_Addr)obj->relocbase; 254 else 255 store_ptr(where, 256 load_ptr(where) + (Elf_Addr)obj->relocbase); 257 rdbg(("RELATIVE in %s --> %p", obj->path, 258 (void *)*where)); 259 break; 260 261 case R_TYPE(COPY): 262 /* 263 * These are deferred until all other relocations have 264 * been done. All we do here is make sure that the 265 * COPY relocation is not in a shared library. They 266 * are allowed only in executable files. 267 */ 268 if (obj->isdynamic) { 269 _rtld_error( 270 "%s: Unexpected R_COPY relocation in shared library", 271 obj->path); 272 return -1; 273 } 274 rdbg(("COPY (avoid in main)")); 275 break; 276 277 default: 278 rdbg(("sym = %lu, type = %lu, offset = %p, " 279 "addend = %p, contents = %p, symbol = %s", 280 symnum, (u_long)ELF_R_TYPE(rela->r_info), 281 (void *)rela->r_offset, (void *)rela->r_addend, 282 (void *)load_ptr(where), 283 obj->strtab + obj->symtab[symnum].st_name)); 284 _rtld_error("%s: Unsupported relocation type %ld " 285 "in non-PLT relocations\n", 286 obj->path, (u_long) ELF_R_TYPE(rela->r_info)); 287 return -1; 288 } 289 } 290 return 0; 291} 292 293int 294_rtld_relocate_plt_lazy(const Obj_Entry *obj) 295{ 296 const Elf_Rela *rela; 297 298 if (!obj->relocbase) 299 return 0; 300 301 for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) { 302 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 303 304 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 305 306 /* Just relocate the GOT slots pointing into the PLT */ 307 *where += (Elf_Addr)obj->relocbase; 308 rdbg(("fixup !main in %s --> %p", obj->path, (void *)*where)); 309 } 310 311 return 0; 312} 313 314static inline int 315_rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp) 316{ 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 return -1; 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 } 480out: 481 if (tp) 482 *tp = new_value; 483 484 return 0; 485} 486 487caddr_t 488_rtld_bind(const Obj_Entry *obj, Elf_Word reloff) 489{ 490 const Elf_Rela *rela = (const Elf_Rela *)((caddr_t)obj->pltrela + reloff); 491 Elf_Addr result; 492 int err; 493 494 err = _rtld_relocate_plt_object(obj, rela, &result); 495 if (err) 496 _rtld_die(); 497 498 return (caddr_t)result; 499} 500 501int 502_rtld_relocate_plt_objects(const Obj_Entry *obj) 503{ 504 const Elf_Rela *rela; 505 506 for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) 507 if (_rtld_relocate_plt_object(obj, rela, NULL) < 0) 508 return -1; 509 510 return 0; 511} 512