alpha_reloc.c revision 1.27
1/* $NetBSD: alpha_reloc.c,v 1.27 2005/08/15 10:52:42 skrll 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 76void _rtld_bind_start(void); 77void _rtld_bind_start_old(void); 78void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr); 79caddr_t _rtld_bind(const Obj_Entry *, Elf_Word); 80static inline int _rtld_relocate_plt_object(const Obj_Entry *, 81 const Elf_Rela *, Elf_Addr *); 82 83void 84_rtld_setup_pltgot(const Obj_Entry *obj) 85{ 86 uint32_t word0; 87 88 /* 89 * The PLTGOT on the Alpha looks like this: 90 * 91 * PLT HEADER 92 * . 93 * . 32 bytes 94 * . 95 * PLT ENTRY #0 96 * . 97 * . 12 bytes 98 * . 99 * PLT ENTRY #1 100 * . 101 * . 12 bytes 102 * . 103 * etc. 104 * 105 * The old-format entries look like (displacements filled in 106 * by the linker): 107 * 108 * ldah $28, 0($31) # 0x279f0000 109 * lda $28, 0($28) # 0x239c0000 110 * br $31, plt0 # 0xc3e00000 111 * 112 * The new-format entries look like: 113 * 114 * br $28, plt0 # 0xc3800000 115 * # 0x00000000 116 * # 0x00000000 117 * 118 * What we do is fetch the first PLT entry and check to 119 * see the first word of it matches the first word of the 120 * old format. If so, we use a binding routine that can 121 * handle the old format, otherwise we use a binding routine 122 * that handles the new format. 123 * 124 * Note that this is done on a per-object basis, we can mix 125 * and match shared objects build with both the old and new 126 * linker. 127 */ 128 word0 = *(uint32_t *)(((char *) obj->pltgot) + 32); 129 if ((word0 & 0xffff0000) == 0x279f0000) { 130 /* Old PLT entry format. */ 131 adbg(("ALPHA: object %p has old PLT format\n", obj)); 132 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start_old; 133 obj->pltgot[3] = (Elf_Addr) obj; 134 } else { 135 /* New PLT entry format. */ 136 adbg(("ALPHA: object %p has new PLT format\n", obj)); 137 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 138 obj->pltgot[3] = (Elf_Addr) obj; 139 } 140 141 __asm __volatile("imb"); 142} 143 144/* 145 * It is possible for the compiler to emit relocations for unaligned data. 146 * We handle this situation with these inlines. 147 */ 148#define RELOC_ALIGNED_P(x) \ 149 (((uintptr_t)(x) & (sizeof(void *) - 1)) == 0) 150 151static __inline Elf_Addr 152load_ptr(void *where) 153{ 154 Elf_Addr res; 155 156 memcpy(&res, where, sizeof(res)); 157 158 return (res); 159} 160 161static __inline void 162store_ptr(void *where, Elf_Addr val) 163{ 164 165 memcpy(where, &val, sizeof(val)); 166} 167 168void 169_rtld_relocate_nonplt_self(Elf_Dyn *dynp, 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 193int 194_rtld_relocate_nonplt_objects(const Obj_Entry *obj) 195{ 196 const Elf_Rela *rela; 197#define COMBRELOC 198#ifdef COMBRELOC 199 unsigned long lastsym = -1; 200#endif 201 Elf_Addr target = -1; 202 203 for (rela = obj->rela; rela < obj->relalim; rela++) { 204 Elf_Addr *where; 205 const Elf_Sym *def; 206 const Obj_Entry *defobj; 207 Elf_Addr tmp; 208 unsigned long symnum; 209 210 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 211 symnum = ELF_R_SYM(rela->r_info); 212 213 switch (ELF_R_TYPE(rela->r_info)) { 214 case R_TYPE(NONE): 215 break; 216 217 case R_TYPE(REFQUAD): 218 case R_TYPE(GLOB_DAT): 219#ifdef COMBRELOC 220 if (symnum != lastsym) { 221#endif 222 def = _rtld_find_symdef(symnum, obj, &defobj, 223 false); 224 if (def == NULL) 225 return -1; 226 target = (Elf_Addr)(defobj->relocbase + 227 def->st_value); 228#ifdef COMBRELOC 229 lastsym = symnum; 230 } 231#endif 232 233 tmp = target + rela->r_addend; 234 if (__predict_true(RELOC_ALIGNED_P(where))) { 235 if (*where != tmp) 236 *where = tmp; 237 } else { 238 if (load_ptr(where) != tmp) 239 store_ptr(where, tmp); 240 } 241 rdbg(("REFQUAD/GLOB_DAT %s in %s --> %p in %s", 242 obj->strtab + obj->symtab[symnum].st_name, 243 obj->path, (void *)tmp, defobj->path)); 244 break; 245 246 case R_TYPE(RELATIVE): 247 if (__predict_true(RELOC_ALIGNED_P(where))) 248 *where += (Elf_Addr)obj->relocbase; 249 else 250 store_ptr(where, 251 load_ptr(where) + (Elf_Addr)obj->relocbase); 252 rdbg(("RELATIVE in %s --> %p", obj->path, 253 (void *)*where)); 254 break; 255 256 case R_TYPE(COPY): 257 /* 258 * These are deferred until all other relocations have 259 * been done. All we do here is make sure that the 260 * COPY relocation is not in a shared library. They 261 * are allowed only in executable files. 262 */ 263 if (obj->isdynamic) { 264 _rtld_error( 265 "%s: Unexpected R_COPY relocation in shared library", 266 obj->path); 267 return -1; 268 } 269 rdbg(("COPY (avoid in main)")); 270 break; 271 272 default: 273 rdbg(("sym = %lu, type = %lu, offset = %p, " 274 "addend = %p, contents = %p, symbol = %s", 275 symnum, (u_long)ELF_R_TYPE(rela->r_info), 276 (void *)rela->r_offset, (void *)rela->r_addend, 277 (void *)load_ptr(where), 278 obj->strtab + obj->symtab[symnum].st_name)); 279 _rtld_error("%s: Unsupported relocation type %ld " 280 "in non-PLT relocations\n", 281 obj->path, (u_long) ELF_R_TYPE(rela->r_info)); 282 return -1; 283 } 284 } 285 return 0; 286} 287 288int 289_rtld_relocate_plt_lazy(const Obj_Entry *obj) 290{ 291 const Elf_Rela *rela; 292 293 if (!obj->relocbase) 294 return 0; 295 296 for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) { 297 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 298 299 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 300 301 /* Just relocate the GOT slots pointing into the PLT */ 302 *where += (Elf_Addr)obj->relocbase; 303 rdbg(("fixup !main in %s --> %p", obj->path, (void *)*where)); 304 } 305 306 return 0; 307} 308 309static inline int 310_rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp) 311{ 312 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 313 Elf_Addr new_value; 314 const Elf_Sym *def; 315 const Obj_Entry *defobj; 316 Elf_Addr stubaddr; 317 318 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 319 320 def = _rtld_find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, true); 321 if (def == NULL) 322 return -1; 323 324 new_value = (Elf_Addr)(defobj->relocbase + def->st_value); 325 rdbg(("bind now/fixup in %s --> old=%p new=%p", 326 defobj->strtab + def->st_name, (void *)*where, (void *)new_value)); 327 328 if ((stubaddr = *where) != new_value) { 329 int64_t delta, idisp; 330 uint32_t insn[3], *stubptr; 331 int insncnt; 332 Elf_Addr pc; 333 334 /* Point this GOT entry at the target. */ 335 *where = new_value; 336 337 /* 338 * Alpha shared objects may have multiple GOTs, each 339 * of which may point to this entry in the PLT. But, 340 * we only have a reference to the first GOT entry which 341 * points to this PLT entry. In order to avoid having to 342 * re-bind this call every time a non-first GOT entry is 343 * used, we will attempt to patch up the PLT entry to 344 * reference the target, rather than the binder. 345 * 346 * When the PLT stub gets control, PV contains the address 347 * of the PLT entry. Each PLT entry has room for 3 insns. 348 * If the displacement of the target from PV fits in a signed 349 * 32-bit integer, we can simply add it to PV. Otherwise, 350 * we must load the GOT entry itself into PV. 351 * 352 * Note if the shared object uses the old PLT format, then 353 * we cannot patch up the PLT safely, and so we skip it 354 * in that case[*]. 355 * 356 * [*] Actually, if we're not doing lazy-binding, then 357 * we *can* (and do) patch up this PLT entry; the PLTGOT 358 * thunk won't yet point to any binder entry point, and 359 * so this test will fail as it would for the new PLT 360 * entry format. 361 */ 362 if (obj->pltgot[2] == (Elf_Addr) &_rtld_bind_start_old) { 363 rdbg((" old PLT format")); 364 goto out; 365 } 366 367 delta = new_value - stubaddr; 368 rdbg((" stubaddr=%p, where-stubaddr=%ld, delta=%ld", 369 (void *)stubaddr, (long)where - (long)stubaddr, 370 (long)delta)); 371 insncnt = 0; 372 if ((int32_t)delta == delta) { 373 /* 374 * We can adjust PV with an LDA, LDAH sequence. 375 * 376 * First, build an LDA insn to adjust the low 16 377 * bits. 378 */ 379 insn[insncnt++] = 0x08 << 26 | 27 << 21 | 27 << 16 | 380 (delta & 0xffff); 381 rdbg((" LDA $27,%d($27)", (int16_t)delta)); 382 /* 383 * Adjust the delta to account for the effects of 384 * the LDA, including sign-extension. 385 */ 386 delta -= (int16_t)delta; 387 if (delta != 0) { 388 /* 389 * Build an LDAH instruction to adjust the 390 * high 16 bits. 391 */ 392 insn[insncnt++] = 0x09 << 26 | 27 << 21 | 393 27 << 16 | ((delta >> 16) & 0xffff); 394 rdbg((" LDAH $27,%d($27)", 395 (int16_t)(delta >> 16))); 396 } 397 } else { 398 int64_t dhigh; 399 400 /* We must load the GOT entry. */ 401 delta = (Elf_Addr)where - stubaddr; 402 403 /* 404 * If the GOT entry is too far away from the PLT 405 * entry, then we can't patch up the PLT entry. 406 * This PLT entry will have to be bound for each 407 * GOT entry except for the first one. This program 408 * will still run, albeit very slowly. It is very 409 * unlikely that this case will ever happen in 410 * practice. 411 */ 412 if ((int32_t)delta != delta) { 413 rdbg((" PLT stub too far from GOT to relocate")); 414 goto out; 415 } 416 dhigh = delta - (int16_t)delta; 417 if (dhigh != 0) { 418 /* 419 * Build an LDAH instruction to adjust the 420 * high 16 bits. 421 */ 422 insn[insncnt++] = 0x09 << 26 | 27 << 21 | 423 27 << 16 | ((dhigh >> 16) & 0xffff); 424 rdbg((" LDAH $27,%d($27)", 425 (int16_t)(dhigh >> 16))); 426 } 427 /* Build an LDQ to load the GOT entry. */ 428 insn[insncnt++] = 0x29 << 26 | 27 << 21 | 429 27 << 16 | (delta & 0xffff); 430 rdbg((" LDQ $27,%d($27)", 431 (int16_t)delta)); 432 } 433 434 /* 435 * Now, build a JMP or BR insn to jump to the target. If 436 * the displacement fits in a sign-extended 21-bit field, 437 * we can use the more efficient BR insn. Otherwise, we 438 * have to jump indirect through PV. 439 */ 440 pc = stubaddr + (4 * (insncnt + 1)); 441 idisp = (int64_t)(new_value - pc) >> 2; 442 if (-0x100000 <= idisp && idisp < 0x100000) { 443 insn[insncnt++] = 0x30 << 26 | 31 << 21 | 444 (idisp & 0x1fffff); 445 rdbg((" BR $31,%p", (void *)new_value)); 446 } else { 447 insn[insncnt++] = 0x1a << 26 | 31 << 21 | 448 27 << 16 | (idisp & 0x3fff); 449 rdbg((" JMP $31,($27),%d", 450 (int)(idisp & 0x3fff))); 451 } 452 453 /* 454 * Fill in the tail of the PLT entry first, for reentrancy. 455 * Until we have overwritten the first insn (an unconditional 456 * branch), the remaining insns have no effect. 457 */ 458 stubptr = (uint32_t *)stubaddr; 459 while (insncnt > 1) { 460 insncnt--; 461 stubptr[insncnt] = insn[insncnt]; 462 } 463 /* 464 * Commit the tail of the insn sequence to memory 465 * before overwriting the first insn. 466 */ 467 __asm __volatile("wmb" ::: "memory"); 468 stubptr[0] = insn[0]; 469 /* 470 * I-stream will be sync'd when we either return from 471 * the binder (lazy bind case) or when the PLTGOT thunk 472 * is patched up (bind-now case). 473 */ 474 } 475out: 476 if (tp) 477 *tp = new_value; 478 479 return 0; 480} 481 482caddr_t 483_rtld_bind(const Obj_Entry *obj, Elf_Word reloff) 484{ 485 const Elf_Rela *rela = (const Elf_Rela *)((caddr_t)obj->pltrela + reloff); 486 Elf_Addr result; 487 int err; 488 489 err = _rtld_relocate_plt_object(obj, rela, &result); 490 if (err) 491 _rtld_die(); 492 493 return (caddr_t)result; 494} 495 496int 497_rtld_relocate_plt_objects(const Obj_Entry *obj) 498{ 499 const Elf_Rela *rela; 500 501 for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) 502 if (_rtld_relocate_plt_object(obj, rela, NULL) < 0) 503 return -1; 504 505 return 0; 506} 507