1 /* $NetBSD: map_object.c,v 1.12 2000/11/26 05:22:15 mycroft Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt@3am-software.com> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by John Polstra. 19 * 4. The name of the author may not be used to endorse or promote products 20 * derived from this software without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 */ 33 34 #include <errno.h> 35 #include <stddef.h> 36 #include <stdlib.h> 37 #include <string.h> 38 #include <unistd.h> 39 #include <sys/stat.h> 40 #include <sys/types.h> 41 #include <sys/mman.h> 42 43 #include "rtld.h" 44 45 static int protflags __P((int)); /* Elf flags -> mmap protection */ 46 47 /* 48 * Map a shared object into memory. The argument is a file descriptor, 49 * which must be open on the object and positioned at its beginning. 50 * 51 * The return value is a pointer to a newly-allocated Obj_Entry structure 52 * for the shared object. Returns NULL on failure. 53 */ 54 Obj_Entry * 55 _rtld_map_object(path, fd, sb) 56 const char *path; 57 int fd; 58 const struct stat *sb; 59 { 60 Obj_Entry *obj; 61 union { 62 Elf_Ehdr hdr; 63 char buf[PAGESIZE]; 64 } u; 65 int nbytes; 66 Elf_Phdr *phdr; 67 Elf_Phdr *phlimit; 68 Elf_Phdr *segs[2]; 69 int nsegs; 70 Elf_Phdr *phdyn; 71 Elf_Phdr *phphdr; 72 Elf_Phdr *phinterp; 73 caddr_t mapbase; 74 size_t mapsize; 75 Elf_Off base_offset; 76 Elf_Addr base_vaddr; 77 Elf_Addr base_vlimit; 78 Elf_Addr text_vlimit; 79 caddr_t base_addr; 80 Elf_Off data_offset; 81 Elf_Addr data_vaddr; 82 Elf_Addr data_vlimit; 83 caddr_t data_addr; 84 caddr_t gap_addr; 85 size_t gap_size; 86 #ifdef RTLD_LOADER 87 Elf_Addr clear_vaddr; 88 caddr_t clear_addr; 89 size_t nclear; 90 #endif 91 92 if ((nbytes = read(fd, u.buf, PAGESIZE)) == -1) { 93 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 94 return NULL; 95 } 96 /* Make sure the file is valid */ 97 if (nbytes < sizeof(Elf_Ehdr) || 98 memcmp(ELFMAG, u.hdr.e_ident, SELFMAG) != 0 || 99 u.hdr.e_ident[EI_CLASS] != ELFCLASS) { 100 _rtld_error("%s: unrecognized file format", path); 101 return NULL; 102 } 103 /* Elf_e_ident includes class */ 104 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT || 105 u.hdr.e_version != EV_CURRENT || 106 u.hdr.e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 107 _rtld_error("%s: Unsupported file version", path); 108 return NULL; 109 } 110 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) { 111 _rtld_error("%s: Unsupported file type", path); 112 return NULL; 113 } 114 switch (u.hdr.e_machine) { 115 ELFDEFNNAME(MACHDEP_ID_CASES) 116 default: 117 _rtld_error("%s: Unsupported machine", path); 118 return NULL; 119 } 120 121 /* 122 * We rely on the program header being in the first page. This is 123 * not strictly required by the ABI specification, but it seems to 124 * always true in practice. And, it simplifies things considerably. 125 */ 126 assert(u.hdr.e_phentsize == sizeof(Elf_Phdr)); 127 assert(u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) <= PAGESIZE); 128 assert(u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) <= nbytes); 129 130 /* 131 * Scan the program header entries, and save key information. 132 * 133 * We rely on there being exactly two load segments, text and data, 134 * in that order. 135 */ 136 phdr = (Elf_Phdr *) (u.buf + u.hdr.e_phoff); 137 phlimit = phdr + u.hdr.e_phnum; 138 nsegs = 0; 139 phdyn = phphdr = phinterp = NULL; 140 while (phdr < phlimit) { 141 switch (phdr->p_type) { 142 case PT_INTERP: 143 phinterp = phdr; 144 break; 145 146 case PT_LOAD: 147 if (nsegs < 2) 148 segs[nsegs] = phdr; 149 ++nsegs; 150 break; 151 152 case PT_PHDR: 153 phphdr = phdr; 154 break; 155 156 case PT_DYNAMIC: 157 phdyn = phdr; 158 break; 159 } 160 161 ++phdr; 162 } 163 if (phdyn == NULL) { 164 _rtld_error("%s: not dynamically linked", path); 165 return NULL; 166 } 167 if (nsegs != 2) { 168 _rtld_error("%s: wrong number of segments (%d != 2)", path, 169 nsegs); 170 return NULL; 171 } 172 #ifdef __i386__ 173 assert(segs[0]->p_align <= PAGESIZE); 174 assert(segs[1]->p_align <= PAGESIZE); 175 #endif 176 177 /* 178 * Map the entire address space of the object as a file 179 * region to stake out our contiguous region and establish a 180 * base for relocation. We use a file mapping so that 181 * the kernel will give us whatever alignment is appropriate 182 * for the platform we're running on. 183 * 184 * We map it using the text protection, map the data segment 185 * into the right place, then map an anon segment for the bss 186 * and unmap the gaps left by padding to alignment. 187 */ 188 189 base_offset = round_down(segs[0]->p_offset); 190 base_vaddr = round_down(segs[0]->p_vaddr); 191 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 192 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 193 mapsize = base_vlimit - base_vaddr; 194 195 #ifdef RTLD_LOADER 196 base_addr = u.hdr.e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL; 197 #else 198 base_addr = NULL; 199 #endif 200 201 mapbase = mmap(base_addr, mapsize, protflags(segs[0]->p_flags), 202 MAP_FILE | MAP_PRIVATE, fd, base_offset); 203 if (mapbase == MAP_FAILED) { 204 _rtld_error("mmap of entire address space failed: %s", 205 xstrerror(errno)); 206 return NULL; 207 } 208 209 base_addr = mapbase; 210 211 /* Overlay the data segment onto the proper region. */ 212 data_offset = round_down(segs[1]->p_offset); 213 data_vaddr = round_down(segs[1]->p_vaddr); 214 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 215 data_addr = mapbase + (data_vaddr - base_vaddr); 216 if (mmap(data_addr, data_vlimit - data_vaddr, 217 protflags(segs[1]->p_flags), 218 MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) 219 == MAP_FAILED) { 220 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 221 munmap(mapbase, mapsize); 222 return NULL; 223 } 224 225 /* Overlay the bss segment onto the proper region. */ 226 if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit, 227 protflags(segs[1]->p_flags), 228 MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) 229 == MAP_FAILED) { 230 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 231 munmap(mapbase, mapsize); 232 return NULL; 233 } 234 235 /* Unmap the gap between the text and data. */ 236 gap_addr = base_addr + round_up(text_vlimit - base_vaddr); 237 gap_size = data_addr - gap_addr; 238 if (gap_size != 0 && munmap(gap_addr, gap_size) == -1) { 239 _rtld_error("munmap of text -> data gap failed: %s", 240 xstrerror(errno)); 241 munmap(mapbase, mapsize); 242 return NULL; 243 } 244 245 #ifdef RTLD_LOADER 246 /* Clear any BSS in the last page of the data segment. */ 247 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 248 clear_addr = mapbase + (clear_vaddr - base_vaddr); 249 if ((nclear = data_vlimit - clear_vaddr) > 0) 250 memset(clear_addr, 0, nclear); 251 252 /* Non-file portion of BSS mapped above. */ 253 #endif 254 255 obj = _rtld_obj_new(); 256 if (sb != NULL) { 257 obj->dev = sb->st_dev; 258 obj->ino = sb->st_ino; 259 } 260 obj->mapbase = mapbase; 261 obj->mapsize = mapsize; 262 obj->textsize = round_up(segs[0]->p_vaddr + segs[0]->p_memsz) - 263 base_vaddr; 264 obj->vaddrbase = base_vaddr; 265 obj->relocbase = mapbase - base_vaddr; 266 obj->dynamic = (Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr); 267 if (u.hdr.e_entry != 0) 268 obj->entry = (caddr_t)(obj->relocbase + u.hdr.e_entry); 269 if (phphdr != NULL) { 270 obj->phdr = (const Elf_Phdr *) 271 (obj->relocbase + phphdr->p_vaddr); 272 obj->phsize = phphdr->p_memsz; 273 } 274 if (phinterp != NULL) 275 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr); 276 277 return obj; 278 } 279 280 void 281 _rtld_obj_free(obj) 282 Obj_Entry *obj; 283 { 284 Objlist_Entry *elm; 285 286 free(obj->path); 287 while (obj->needed != NULL) { 288 Needed_Entry *needed = obj->needed; 289 obj->needed = needed->next; 290 free(needed); 291 } 292 while (SIMPLEQ_FIRST(&obj->dldags) != NULL) { 293 elm = SIMPLEQ_FIRST(&obj->dldags); 294 SIMPLEQ_REMOVE_HEAD(&obj->dldags, elm, link); 295 free(elm); 296 } 297 while (SIMPLEQ_FIRST(&obj->dagmembers) != NULL) { 298 elm = SIMPLEQ_FIRST(&obj->dagmembers); 299 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, elm, link); 300 free(elm); 301 } 302 free(obj); 303 } 304 305 Obj_Entry * 306 _rtld_obj_new(void) 307 { 308 Obj_Entry *obj; 309 310 obj = CNEW(Obj_Entry); 311 SIMPLEQ_INIT(&obj->dldags); 312 SIMPLEQ_INIT(&obj->dagmembers); 313 return obj; 314 } 315 316 /* 317 * Given a set of ELF protection flags, return the corresponding protection 318 * flags for MMAP. 319 */ 320 static int 321 protflags(elfflags) 322 int elfflags; 323 { 324 int prot = 0; 325 if (elfflags & PF_R) 326 prot |= PROT_READ; 327 #ifdef RTLD_LOADER 328 if (elfflags & PF_W) 329 prot |= PROT_WRITE; 330 #endif 331 if (elfflags & PF_X) 332 prot |= PROT_EXEC; 333 return prot; 334 } 335