1 /* $NetBSD: mdreloc.c,v 1.43 2010/01/13 20:17:22 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 1999, 2002 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Paul Kranenburg and by Charles M. Hannum. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 #ifndef lint 34 __RCSID("$NetBSD: mdreloc.c,v 1.43 2010/01/13 20:17:22 christos Exp $"); 35 #endif /* not lint */ 36 37 #include <errno.h> 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <string.h> 41 #include <unistd.h> 42 #include <sys/stat.h> 43 44 #include "rtldenv.h" 45 #include "debug.h" 46 #include "rtld.h" 47 48 /* 49 * The following table holds for each relocation type: 50 * - the width in bits of the memory location the relocation 51 * applies to (not currently used) 52 * - the number of bits the relocation value must be shifted to the 53 * right (i.e. discard least significant bits) to fit into 54 * the appropriate field in the instruction word. 55 * - flags indicating whether 56 * * the relocation involves a symbol 57 * * the relocation is relative to the current position 58 * * the relocation is for a GOT entry 59 * * the relocation is relative to the load address 60 * 61 */ 62 #define _RF_S 0x80000000 /* Resolve symbol */ 63 #define _RF_A 0x40000000 /* Use addend */ 64 #define _RF_P 0x20000000 /* Location relative */ 65 #define _RF_G 0x10000000 /* GOT offset */ 66 #define _RF_B 0x08000000 /* Load address relative */ 67 #define _RF_U 0x04000000 /* Unaligned */ 68 #define _RF_SZ(s) (((s) & 0xff) << 8) /* memory target size */ 69 #define _RF_RS(s) ( (s) & 0xff) /* right shift */ 70 static const int reloc_target_flags[] = { 71 0, /* NONE */ 72 _RF_S|_RF_A| _RF_SZ(8) | _RF_RS(0), /* RELOC_8 */ 73 _RF_S|_RF_A| _RF_SZ(16) | _RF_RS(0), /* RELOC_16 */ 74 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* RELOC_32 */ 75 _RF_S|_RF_A|_RF_P| _RF_SZ(8) | _RF_RS(0), /* DISP_8 */ 76 _RF_S|_RF_A|_RF_P| _RF_SZ(16) | _RF_RS(0), /* DISP_16 */ 77 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* DISP_32 */ 78 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WDISP_30 */ 79 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WDISP_22 */ 80 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(10), /* HI22 */ 81 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 22 */ 82 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 13 */ 83 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* LO10 */ 84 _RF_G| _RF_SZ(32) | _RF_RS(0), /* GOT10 */ 85 _RF_G| _RF_SZ(32) | _RF_RS(0), /* GOT13 */ 86 _RF_G| _RF_SZ(32) | _RF_RS(10), /* GOT22 */ 87 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* PC10 */ 88 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(10), /* PC22 */ 89 _RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WPLT30 */ 90 _RF_SZ(32) | _RF_RS(0), /* COPY */ 91 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* GLOB_DAT */ 92 _RF_SZ(32) | _RF_RS(0), /* JMP_SLOT */ 93 _RF_A| _RF_B| _RF_SZ(32) | _RF_RS(0), /* RELATIVE */ 94 _RF_S|_RF_A| _RF_U| _RF_SZ(32) | _RF_RS(0), /* UA_32 */ 95 }; 96 97 #ifdef RTLD_DEBUG_RELOC 98 static const char *reloc_names[] = { 99 "NONE", "RELOC_8", "RELOC_16", "RELOC_32", "DISP_8", 100 "DISP_16", "DISP_32", "WDISP_30", "WDISP_22", "HI22", 101 "22", "13", "LO10", "GOT10", "GOT13", 102 "GOT22", "PC10", "PC22", "WPLT30", "COPY", 103 "GLOB_DAT", "JMP_SLOT", "RELATIVE", "UA_32" 104 }; 105 #endif 106 107 #define RELOC_RESOLVE_SYMBOL(t) ((reloc_target_flags[t] & _RF_S) != 0) 108 #define RELOC_PC_RELATIVE(t) ((reloc_target_flags[t] & _RF_P) != 0) 109 #define RELOC_BASE_RELATIVE(t) ((reloc_target_flags[t] & _RF_B) != 0) 110 #define RELOC_UNALIGNED(t) ((reloc_target_flags[t] & _RF_U) != 0) 111 #define RELOC_USE_ADDEND(t) ((reloc_target_flags[t] & _RF_A) != 0) 112 #define RELOC_TARGET_SIZE(t) ((reloc_target_flags[t] >> 8) & 0xff) 113 #define RELOC_VALUE_RIGHTSHIFT(t) (reloc_target_flags[t] & 0xff) 114 115 static const int reloc_target_bitmask[] = { 116 #define _BM(x) (~(-(1ULL << (x)))) 117 0, /* NONE */ 118 _BM(8), _BM(16), _BM(32), /* RELOC_8, _16, _32 */ 119 _BM(8), _BM(16), _BM(32), /* DISP8, DISP16, DISP32 */ 120 _BM(30), _BM(22), /* WDISP30, WDISP22 */ 121 _BM(22), _BM(22), /* HI22, _22 */ 122 _BM(13), _BM(10), /* RELOC_13, _LO10 */ 123 _BM(10), _BM(13), _BM(22), /* GOT10, GOT13, GOT22 */ 124 _BM(10), _BM(22), /* _PC10, _PC22 */ 125 _BM(30), 0, /* _WPLT30, _COPY */ 126 -1, -1, -1, /* _GLOB_DAT, JMP_SLOT, _RELATIVE */ 127 _BM(32) /* _UA32 */ 128 #undef _BM 129 }; 130 #define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t]) 131 132 void _rtld_bind_start(void); 133 void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr); 134 caddr_t _rtld_bind(const Obj_Entry *, Elf_Word); 135 static inline int _rtld_relocate_plt_object(const Obj_Entry *, 136 const Elf_Rela *, Elf_Addr *); 137 138 void 139 _rtld_setup_pltgot(const Obj_Entry *obj) 140 { 141 /* 142 * PLTGOT is the PLT on the sparc. 143 * The first entry holds the call the dynamic linker. 144 * We construct a `call' sequence that transfers 145 * to `_rtld_bind_start()'. 146 * The second entry holds the object identification. 147 * Note: each PLT entry is three words long. 148 */ 149 #define SAVE 0x9de3bfa0 /* i.e. `save %sp,-96,%sp' */ 150 #define CALL 0x40000000 151 #define NOP 0x01000000 152 obj->pltgot[0] = SAVE; 153 obj->pltgot[1] = CALL | 154 ((Elf_Addr) &_rtld_bind_start - (Elf_Addr) &obj->pltgot[1]) >> 2; 155 obj->pltgot[2] = NOP; 156 obj->pltgot[3] = (Elf_Addr) obj; 157 } 158 159 void 160 _rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase) 161 { 162 const Elf_Rela *rela = 0, *relalim; 163 Elf_Addr relasz = 0; 164 Elf_Addr *where; 165 166 for (; dynp->d_tag != DT_NULL; dynp++) { 167 switch (dynp->d_tag) { 168 case DT_RELA: 169 rela = (const Elf_Rela *)(relocbase + dynp->d_un.d_ptr); 170 break; 171 case DT_RELASZ: 172 relasz = dynp->d_un.d_val; 173 break; 174 } 175 } 176 relalim = (const Elf_Rela *)((const uint8_t *)rela + relasz); 177 for (; rela < relalim; rela++) { 178 where = (Elf_Addr *)(relocbase + rela->r_offset); 179 *where += (Elf_Addr)(relocbase + rela->r_addend); 180 } 181 } 182 183 int 184 _rtld_relocate_nonplt_objects(const Obj_Entry *obj) 185 { 186 const Elf_Rela *rela; 187 188 for (rela = obj->rela; rela < obj->relalim; rela++) { 189 Elf_Addr *where; 190 Elf_Word type, value, mask; 191 const Elf_Sym *def = NULL; 192 const Obj_Entry *defobj = NULL; 193 unsigned long symnum; 194 195 where = (Elf_Addr *) (obj->relocbase + rela->r_offset); 196 symnum = ELF_R_SYM(rela->r_info); 197 198 type = ELF_R_TYPE(rela->r_info); 199 if (type == R_TYPE(NONE)) 200 continue; 201 202 /* We do JMP_SLOTs in _rtld_bind() below */ 203 if (type == R_TYPE(JMP_SLOT)) 204 continue; 205 206 /* COPY relocs are also handled elsewhere */ 207 if (type == R_TYPE(COPY)) 208 continue; 209 210 /* 211 * We use the fact that relocation types are an `enum' 212 * Note: R_SPARC_6 is currently numerically largest. 213 */ 214 if (type > R_TYPE(6)) 215 return (-1); 216 217 value = rela->r_addend; 218 219 /* 220 * Handle relative relocs here, as an optimization. 221 */ 222 if (type == R_TYPE(RELATIVE)) { 223 *where += (Elf_Addr)(obj->relocbase + value); 224 rdbg(("RELATIVE in %s --> %p", obj->path, 225 (void *)*where)); 226 continue; 227 } 228 229 if (RELOC_RESOLVE_SYMBOL(type)) { 230 231 /* Find the symbol */ 232 def = _rtld_find_symdef(symnum, obj, &defobj, false); 233 if (def == NULL) 234 return (-1); 235 236 /* Add in the symbol's absolute address */ 237 value += (Elf_Word)(defobj->relocbase + def->st_value); 238 } 239 240 if (RELOC_PC_RELATIVE(type)) { 241 value -= (Elf_Word)where; 242 } 243 244 if (RELOC_BASE_RELATIVE(type)) { 245 /* 246 * Note that even though sparcs use `Elf_rela' 247 * exclusively we still need the implicit memory addend 248 * in relocations referring to GOT entries. 249 * Undoubtedly, someone f*cked this up in the distant 250 * past, and now we're stuck with it in the name of 251 * compatibility for all eternity.. 252 * 253 * In any case, the implicit and explicit should be 254 * mutually exclusive. We provide a check for that 255 * here. 256 */ 257 #define DIAGNOSTIC 258 #ifdef DIAGNOSTIC 259 if (value != 0 && *where != 0) { 260 xprintf("BASE_REL(%s): where=%p, *where 0x%x, " 261 "addend=0x%x, base %p\n", 262 obj->path, where, *where, 263 rela->r_addend, obj->relocbase); 264 } 265 #endif 266 value += (Elf_Word)(obj->relocbase + *where); 267 } 268 269 mask = RELOC_VALUE_BITMASK(type); 270 value >>= RELOC_VALUE_RIGHTSHIFT(type); 271 value &= mask; 272 273 if (RELOC_UNALIGNED(type)) { 274 /* Handle unaligned relocations. */ 275 Elf_Addr tmp = 0; 276 char *ptr = (char *)where; 277 int i, size = RELOC_TARGET_SIZE(type)/8; 278 279 /* Read it in one byte at a time. */ 280 for (i=0; i<size; i++) 281 tmp = (tmp << 8) | ptr[i]; 282 283 tmp &= ~mask; 284 tmp |= value; 285 286 /* Write it back out. */ 287 for (i=0; i<size; i++) 288 ptr[i] = ((tmp >> (8*i)) & 0xff); 289 #ifdef RTLD_DEBUG_RELOC 290 value = (Elf_Word)tmp; 291 #endif 292 293 } else { 294 *where &= ~mask; 295 *where |= value; 296 #ifdef RTLD_DEBUG_RELOC 297 value = (Elf_Word)*where; 298 #endif 299 } 300 #ifdef RTLD_DEBUG_RELOC 301 if (RELOC_RESOLVE_SYMBOL(type)) { 302 rdbg(("%s %s in %s --> %p in %s", reloc_names[type], 303 obj->strtab + obj->symtab[symnum].st_name, 304 obj->path, (void *)value, defobj->path)); 305 } else { 306 rdbg(("%s in %s --> %p", reloc_names[type], 307 obj->path, (void *)value)); 308 } 309 #endif 310 } 311 return (0); 312 } 313 314 int 315 _rtld_relocate_plt_lazy(const Obj_Entry *obj) 316 { 317 return (0); 318 } 319 320 caddr_t 321 _rtld_bind(const Obj_Entry *obj, Elf_Word reloff) 322 { 323 const Elf_Rela *rela = (const Elf_Rela *)((const uint8_t *)obj->pltrela + reloff); 324 Elf_Addr value; 325 int err; 326 327 value = 0; /* XXX gcc */ 328 329 err = _rtld_relocate_plt_object(obj, rela, &value); 330 if (err) 331 _rtld_die(); 332 333 return (caddr_t)value; 334 } 335 336 int 337 _rtld_relocate_plt_objects(const Obj_Entry *obj) 338 { 339 const Elf_Rela *rela = obj->pltrela; 340 341 for (; rela < obj->pltrelalim; rela++) 342 if (_rtld_relocate_plt_object(obj, rela, NULL) < 0) 343 return -1; 344 345 return 0; 346 } 347 348 static inline int 349 _rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp) 350 { 351 const Elf_Sym *def; 352 const Obj_Entry *defobj; 353 Elf_Word *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 354 Elf_Addr value; 355 unsigned long info = rela->r_info; 356 357 assert(ELF_R_TYPE(info) == R_TYPE(JMP_SLOT)); 358 359 def = _rtld_find_plt_symdef(ELF_R_SYM(info), obj, &defobj, tp != NULL); 360 if (__predict_false(def == NULL)) 361 return -1; 362 if (__predict_false(def == &_rtld_sym_zero)) 363 return 0; 364 365 value = (Elf_Addr)(defobj->relocbase + def->st_value); 366 rdbg(("bind now/fixup in %s --> new=%p", 367 defobj->strtab + def->st_name, (void *)value)); 368 369 /* 370 * At the PLT entry pointed at by `where', we now construct 371 * a direct transfer to the now fully resolved function 372 * address. The resulting code in the jump slot is: 373 * 374 * sethi %hi(roffset), %g1 375 * sethi %hi(addr), %g1 376 * jmp %g1+%lo(addr) 377 * 378 * We write the third instruction first, since that leaves the 379 * previous `b,a' at the second word in place. Hence the whole 380 * PLT slot can be atomically change to the new sequence by 381 * writing the `sethi' instruction at word 2. 382 */ 383 #define SETHI 0x03000000 384 #define JMP 0x81c06000 385 #define NOP 0x01000000 386 where[2] = JMP | (value & 0x000003ff); 387 where[1] = SETHI | ((value >> 10) & 0x003fffff); 388 __asm volatile("iflush %0+8" : : "r" (where)); 389 __asm volatile("iflush %0+4" : : "r" (where)); 390 391 if (tp) 392 *tp = value; 393 394 return 0; 395 } 396