1 /* $NetBSD: mdreloc.c,v 1.44 2010/08/06 16:33:18 joerg 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 1.44 2010/08/06 16:33:18 joerg 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 43 #include "rtldenv.h" 44 #include "debug.h" 45 #include "rtld.h" 46 47 /* 48 * The following table holds for each relocation type: 49 * - the width in bits of the memory location the relocation 50 * applies to (not currently used) 51 * - the number of bits the relocation value must be shifted to the 52 * right (i.e. discard least significant bits) to fit into 53 * the appropriate field in the instruction word. 54 * - flags indicating whether 55 * * the relocation involves a symbol 56 * * the relocation is relative to the current position 57 * * the relocation is for a GOT entry 58 * * the relocation is relative to the load address 59 * 60 */ 61 #define _RF_S 0x80000000 /* Resolve symbol */ 62 #define _RF_A 0x40000000 /* Use addend */ 63 #define _RF_P 0x20000000 /* Location relative */ 64 #define _RF_G 0x10000000 /* GOT offset */ 65 #define _RF_B 0x08000000 /* Load address relative */ 66 #define _RF_U 0x04000000 /* Unaligned */ 67 #define _RF_SZ(s) (((s) & 0xff) << 8) /* memory target size */ 68 #define _RF_RS(s) ( (s) & 0xff) /* right shift */ 69 static const int reloc_target_flags[] = { 70 0, /* NONE */ 71 _RF_S|_RF_A| _RF_SZ(8) | _RF_RS(0), /* RELOC_8 */ 72 _RF_S|_RF_A| _RF_SZ(16) | _RF_RS(0), /* RELOC_16 */ 73 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* RELOC_32 */ 74 _RF_S|_RF_A|_RF_P| _RF_SZ(8) | _RF_RS(0), /* DISP_8 */ 75 _RF_S|_RF_A|_RF_P| _RF_SZ(16) | _RF_RS(0), /* DISP_16 */ 76 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* DISP_32 */ 77 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WDISP_30 */ 78 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WDISP_22 */ 79 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(10), /* HI22 */ 80 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 22 */ 81 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 13 */ 82 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* LO10 */ 83 _RF_G| _RF_SZ(32) | _RF_RS(0), /* GOT10 */ 84 _RF_G| _RF_SZ(32) | _RF_RS(0), /* GOT13 */ 85 _RF_G| _RF_SZ(32) | _RF_RS(10), /* GOT22 */ 86 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* PC10 */ 87 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(10), /* PC22 */ 88 _RF_A|_RF_P| _RF_SZ(32) | _RF_RS(2), /* WPLT30 */ 89 _RF_SZ(32) | _RF_RS(0), /* COPY */ 90 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* GLOB_DAT */ 91 _RF_SZ(32) | _RF_RS(0), /* JMP_SLOT */ 92 _RF_A| _RF_B| _RF_SZ(32) | _RF_RS(0), /* RELATIVE */ 93 _RF_S|_RF_A| _RF_U| _RF_SZ(32) | _RF_RS(0), /* UA_32 */ 94 }; 95 96 #ifdef RTLD_DEBUG_RELOC 97 static const char *reloc_names[] = { 98 "NONE", "RELOC_8", "RELOC_16", "RELOC_32", "DISP_8", 99 "DISP_16", "DISP_32", "WDISP_30", "WDISP_22", "HI22", 100 "22", "13", "LO10", "GOT10", "GOT13", 101 "GOT22", "PC10", "PC22", "WPLT30", "COPY", 102 "GLOB_DAT", "JMP_SLOT", "RELATIVE", "UA_32" 103 }; 104 #endif 105 106 #define RELOC_RESOLVE_SYMBOL(t) ((reloc_target_flags[t] & _RF_S) != 0) 107 #define RELOC_PC_RELATIVE(t) ((reloc_target_flags[t] & _RF_P) != 0) 108 #define RELOC_BASE_RELATIVE(t) ((reloc_target_flags[t] & _RF_B) != 0) 109 #define RELOC_UNALIGNED(t) ((reloc_target_flags[t] & _RF_U) != 0) 110 #define RELOC_USE_ADDEND(t) ((reloc_target_flags[t] & _RF_A) != 0) 111 #define RELOC_TARGET_SIZE(t) ((reloc_target_flags[t] >> 8) & 0xff) 112 #define RELOC_VALUE_RIGHTSHIFT(t) (reloc_target_flags[t] & 0xff) 113 114 static const int reloc_target_bitmask[] = { 115 #define _BM(x) (~(-(1ULL << (x)))) 116 0, /* NONE */ 117 _BM(8), _BM(16), _BM(32), /* RELOC_8, _16, _32 */ 118 _BM(8), _BM(16), _BM(32), /* DISP8, DISP16, DISP32 */ 119 _BM(30), _BM(22), /* WDISP30, WDISP22 */ 120 _BM(22), _BM(22), /* HI22, _22 */ 121 _BM(13), _BM(10), /* RELOC_13, _LO10 */ 122 _BM(10), _BM(13), _BM(22), /* GOT10, GOT13, GOT22 */ 123 _BM(10), _BM(22), /* _PC10, _PC22 */ 124 _BM(30), 0, /* _WPLT30, _COPY */ 125 -1, -1, -1, /* _GLOB_DAT, JMP_SLOT, _RELATIVE */ 126 _BM(32) /* _UA32 */ 127 #undef _BM 128 }; 129 #define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t]) 130 131 void _rtld_bind_start(void); 132 void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr); 133 caddr_t _rtld_bind(const Obj_Entry *, Elf_Word); 134 static inline int _rtld_relocate_plt_object(const Obj_Entry *, 135 const Elf_Rela *, Elf_Addr *); 136 137 void 138 _rtld_setup_pltgot(const Obj_Entry *obj) 139 { 140 /* 141 * PLTGOT is the PLT on the sparc. 142 * The first entry holds the call the dynamic linker. 143 * We construct a `call' sequence that transfers 144 * to `_rtld_bind_start()'. 145 * The second entry holds the object identification. 146 * Note: each PLT entry is three words long. 147 */ 148 #define SAVE 0x9de3bfa0 /* i.e. `save %sp,-96,%sp' */ 149 #define CALL 0x40000000 150 #define NOP 0x01000000 151 obj->pltgot[0] = SAVE; 152 obj->pltgot[1] = CALL | 153 ((Elf_Addr) &_rtld_bind_start - (Elf_Addr) &obj->pltgot[1]) >> 2; 154 obj->pltgot[2] = NOP; 155 obj->pltgot[3] = (Elf_Addr) obj; 156 } 157 158 void 159 _rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase) 160 { 161 const Elf_Rela *rela = 0, *relalim; 162 Elf_Addr relasz = 0; 163 Elf_Addr *where; 164 165 for (; dynp->d_tag != DT_NULL; dynp++) { 166 switch (dynp->d_tag) { 167 case DT_RELA: 168 rela = (const Elf_Rela *)(relocbase + dynp->d_un.d_ptr); 169 break; 170 case DT_RELASZ: 171 relasz = dynp->d_un.d_val; 172 break; 173 } 174 } 175 relalim = (const Elf_Rela *)((const uint8_t *)rela + relasz); 176 for (; rela < relalim; rela++) { 177 where = (Elf_Addr *)(relocbase + rela->r_offset); 178 *where += (Elf_Addr)(relocbase + rela->r_addend); 179 } 180 } 181 182 int 183 _rtld_relocate_nonplt_objects(Obj_Entry *obj) 184 { 185 const Elf_Rela *rela; 186 187 for (rela = obj->rela; rela < obj->relalim; rela++) { 188 Elf_Addr *where; 189 Elf_Word type, value, mask; 190 const Elf_Sym *def = NULL; 191 const Obj_Entry *defobj = NULL; 192 unsigned long symnum; 193 194 where = (Elf_Addr *) (obj->relocbase + rela->r_offset); 195 symnum = ELF_R_SYM(rela->r_info); 196 197 type = ELF_R_TYPE(rela->r_info); 198 if (type == R_TYPE(NONE)) 199 continue; 200 201 /* We do JMP_SLOTs in _rtld_bind() below */ 202 if (type == R_TYPE(JMP_SLOT)) 203 continue; 204 205 /* COPY relocs are also handled elsewhere */ 206 if (type == R_TYPE(COPY)) 207 continue; 208 209 /* 210 * We use the fact that relocation types are an `enum' 211 * Note: R_SPARC_6 is currently numerically largest. 212 */ 213 if (type > R_TYPE(6)) 214 return (-1); 215 216 value = rela->r_addend; 217 218 /* 219 * Handle relative relocs here, as an optimization. 220 */ 221 if (type == R_TYPE(RELATIVE)) { 222 *where += (Elf_Addr)(obj->relocbase + value); 223 rdbg(("RELATIVE in %s --> %p", obj->path, 224 (void *)*where)); 225 continue; 226 } 227 228 if (RELOC_RESOLVE_SYMBOL(type)) { 229 230 /* Find the symbol */ 231 def = _rtld_find_symdef(symnum, obj, &defobj, false); 232 if (def == NULL) 233 return (-1); 234 235 /* Add in the symbol's absolute address */ 236 value += (Elf_Word)(defobj->relocbase + def->st_value); 237 } 238 239 if (RELOC_PC_RELATIVE(type)) { 240 value -= (Elf_Word)where; 241 } 242 243 if (RELOC_BASE_RELATIVE(type)) { 244 /* 245 * Note that even though sparcs use `Elf_rela' 246 * exclusively we still need the implicit memory addend 247 * in relocations referring to GOT entries. 248 * Undoubtedly, someone f*cked this up in the distant 249 * past, and now we're stuck with it in the name of 250 * compatibility for all eternity.. 251 * 252 * In any case, the implicit and explicit should be 253 * mutually exclusive. We provide a check for that 254 * here. 255 */ 256 #define DIAGNOSTIC 257 #ifdef DIAGNOSTIC 258 if (value != 0 && *where != 0) { 259 xprintf("BASE_REL(%s): where=%p, *where 0x%x, " 260 "addend=0x%x, base %p\n", 261 obj->path, where, *where, 262 rela->r_addend, obj->relocbase); 263 } 264 #endif 265 value += (Elf_Word)(obj->relocbase + *where); 266 } 267 268 mask = RELOC_VALUE_BITMASK(type); 269 value >>= RELOC_VALUE_RIGHTSHIFT(type); 270 value &= mask; 271 272 if (RELOC_UNALIGNED(type)) { 273 /* Handle unaligned relocations. */ 274 Elf_Addr tmp = 0; 275 char *ptr = (char *)where; 276 int i, size = RELOC_TARGET_SIZE(type)/8; 277 278 /* Read it in one byte at a time. */ 279 for (i=0; i<size; i++) 280 tmp = (tmp << 8) | ptr[i]; 281 282 tmp &= ~mask; 283 tmp |= value; 284 285 /* Write it back out. */ 286 for (i=0; i<size; i++) 287 ptr[i] = ((tmp >> (8*i)) & 0xff); 288 #ifdef RTLD_DEBUG_RELOC 289 value = (Elf_Word)tmp; 290 #endif 291 292 } else { 293 *where &= ~mask; 294 *where |= value; 295 #ifdef RTLD_DEBUG_RELOC 296 value = (Elf_Word)*where; 297 #endif 298 } 299 #ifdef RTLD_DEBUG_RELOC 300 if (RELOC_RESOLVE_SYMBOL(type)) { 301 rdbg(("%s %s in %s --> %p in %s", reloc_names[type], 302 obj->strtab + obj->symtab[symnum].st_name, 303 obj->path, (void *)value, defobj->path)); 304 } else { 305 rdbg(("%s in %s --> %p", reloc_names[type], 306 obj->path, (void *)value)); 307 } 308 #endif 309 } 310 return (0); 311 } 312 313 int 314 _rtld_relocate_plt_lazy(const Obj_Entry *obj) 315 { 316 return (0); 317 } 318 319 caddr_t 320 _rtld_bind(const Obj_Entry *obj, Elf_Word reloff) 321 { 322 const Elf_Rela *rela = (const Elf_Rela *)((const uint8_t *)obj->pltrela + reloff); 323 Elf_Addr value; 324 int err; 325 326 value = 0; /* XXX gcc */ 327 328 err = _rtld_relocate_plt_object(obj, rela, &value); 329 if (err) 330 _rtld_die(); 331 332 return (caddr_t)value; 333 } 334 335 int 336 _rtld_relocate_plt_objects(const Obj_Entry *obj) 337 { 338 const Elf_Rela *rela = obj->pltrela; 339 340 for (; rela < obj->pltrelalim; rela++) 341 if (_rtld_relocate_plt_object(obj, rela, NULL) < 0) 342 return -1; 343 344 return 0; 345 } 346 347 static inline int 348 _rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp) 349 { 350 const Elf_Sym *def; 351 const Obj_Entry *defobj; 352 Elf_Word *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 353 Elf_Addr value; 354 unsigned long info = rela->r_info; 355 356 assert(ELF_R_TYPE(info) == R_TYPE(JMP_SLOT)); 357 358 def = _rtld_find_plt_symdef(ELF_R_SYM(info), obj, &defobj, tp != NULL); 359 if (__predict_false(def == NULL)) 360 return -1; 361 if (__predict_false(def == &_rtld_sym_zero)) 362 return 0; 363 364 value = (Elf_Addr)(defobj->relocbase + def->st_value); 365 rdbg(("bind now/fixup in %s --> new=%p", 366 defobj->strtab + def->st_name, (void *)value)); 367 368 /* 369 * At the PLT entry pointed at by `where', we now construct 370 * a direct transfer to the now fully resolved function 371 * address. The resulting code in the jump slot is: 372 * 373 * sethi %hi(roffset), %g1 374 * sethi %hi(addr), %g1 375 * jmp %g1+%lo(addr) 376 * 377 * We write the third instruction first, since that leaves the 378 * previous `b,a' at the second word in place. Hence the whole 379 * PLT slot can be atomically change to the new sequence by 380 * writing the `sethi' instruction at word 2. 381 */ 382 #define SETHI 0x03000000 383 #define JMP 0x81c06000 384 #define NOP 0x01000000 385 where[2] = JMP | (value & 0x000003ff); 386 where[1] = SETHI | ((value >> 10) & 0x003fffff); 387 __asm volatile("iflush %0+8" : : "r" (where)); 388 __asm volatile("iflush %0+4" : : "r" (where)); 389 390 if (tp) 391 *tp = value; 392 393 return 0; 394 } 395