map_object.c revision 1.5
1 /* $NetBSD: map_object.c,v 1.5 1999/08/06 22:33:49 thorpej Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt (at) 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 <string.h> 37 #include <unistd.h> 38 #include <sys/types.h> 39 #include <sys/mman.h> 40 41 #include "rtld.h" 42 43 #define CONCAT(x,y) __CONCAT(x,y) 44 #define ELFNAME(x) CONCAT(elf,CONCAT(ELFSIZE,CONCAT(_,x))) 45 #define ELFNAME2(x,y) CONCAT(x,CONCAT(_elf,CONCAT(ELFSIZE,CONCAT(_,y)))) 46 #define ELFNAMEEND(x) CONCAT(x,CONCAT(_elf,ELFSIZE)) 47 #define ELFDEFNNAME(x) CONCAT(ELF,CONCAT(ELFSIZE,CONCAT(_,x))) 48 49 static int protflags __P((int)); /* Elf flags -> mmap protection */ 50 51 /* 52 * Map a shared object into memory. The argument is a file descriptor, 53 * which must be open on the object and positioned at its beginning. 54 * 55 * The return value is a pointer to a newly-allocated Obj_Entry structure 56 * for the shared object. Returns NULL on failure. 57 */ 58 Obj_Entry * 59 _rtld_map_object(path, fd) 60 const char *path; 61 int fd; 62 { 63 Obj_Entry *obj; 64 union { 65 Elf_Ehdr hdr; 66 char buf[PAGESIZE]; 67 } u; 68 int nbytes; 69 Elf_Phdr *phdr; 70 Elf_Phdr *phlimit; 71 Elf_Phdr *segs[2]; 72 int nsegs; 73 Elf_Phdr *phdyn; 74 Elf_Phdr *phphdr; 75 caddr_t mapbase; 76 size_t mapsize; 77 Elf_Off base_offset; 78 Elf_Addr base_vaddr; 79 Elf_Addr base_vlimit; 80 Elf_Addr text_vlimit; 81 caddr_t base_addr; 82 Elf_Off data_offset; 83 Elf_Addr data_vaddr; 84 Elf_Addr data_vlimit; 85 caddr_t data_addr; 86 caddr_t gap_addr; 87 size_t gap_size; 88 #ifdef RTLD_LOADER 89 Elf_Addr clear_vaddr; 90 caddr_t clear_addr; 91 size_t nclear; 92 #endif 93 94 if ((nbytes = read(fd, u.buf, PAGESIZE)) == -1) { 95 _rtld_error("%s: read error: %s", path, xstrerror(errno)); 96 return NULL; 97 } 98 /* Make sure the file is valid */ 99 if (nbytes < sizeof(Elf_Ehdr) || 100 memcmp(Elf_e_ident, u.hdr.e_ident, Elf_e_siz) != 0) { 101 _rtld_error("%s: unrecognized file format", path); 102 return NULL; 103 } 104 /* Elf_e_ident includes class */ 105 if (u.hdr.e_ident[Elf_ei_version] != Elf_ev_current || 106 u.hdr.e_version != Elf_ev_current || 107 u.hdr.e_ident[Elf_ei_data] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 108 _rtld_error("%s: Unsupported file version", path); 109 return NULL; 110 } 111 if (u.hdr.e_type != Elf_et_exec && u.hdr.e_type != Elf_et_dyn) { 112 _rtld_error("%s: Unsupported file type", path); 113 return NULL; 114 } 115 switch (u.hdr.e_machine) { 116 ELFDEFNNAME(MACHDEP_ID_CASES) 117 default: 118 _rtld_error("%s: Unsupported machine", path); 119 return NULL; 120 } 121 122 /* 123 * We rely on the program header being in the first page. This is 124 * not strictly required by the ABI specification, but it seems to 125 * always true in practice. And, it simplifies things considerably. 126 */ 127 assert(u.hdr.e_phentsize == sizeof(Elf_Phdr)); 128 assert(u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) <= PAGESIZE); 129 assert(u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) <= nbytes); 130 131 /* 132 * Scan the program header entries, and save key information. 133 * 134 * We rely on there being exactly two load segments, text and data, 135 * in that order. 136 */ 137 phdr = (Elf_Phdr *) (u.buf + u.hdr.e_phoff); 138 phlimit = phdr + u.hdr.e_phnum; 139 nsegs = 0; 140 phdyn = NULL; 141 phphdr = NULL; 142 while (phdr < phlimit) { 143 switch (phdr->p_type) { 144 145 case Elf_pt_load: 146 #ifdef __mips__ 147 /* NetBSD/pmax 1.1 elf toolchain peculiarity */ 148 if (nsegs >= 2) { 149 _rtld_error("%s: too many sections\n", path); 150 return NULL; 151 } 152 #endif 153 assert(nsegs < 2); 154 segs[nsegs] = phdr; 155 ++nsegs; 156 break; 157 158 case Elf_pt_phdr: 159 phphdr = phdr; 160 break; 161 162 case Elf_pt_dynamic: 163 phdyn = phdr; 164 break; 165 } 166 167 ++phdr; 168 } 169 if (phdyn == NULL) { 170 _rtld_error("%s: not dynamically-linked", path); 171 return NULL; 172 } 173 assert(nsegs == 2); 174 #ifdef __i386__ 175 assert(segs[0]->p_align <= PAGESIZE); 176 assert(segs[1]->p_align <= PAGESIZE); 177 #endif 178 179 /* 180 * Map the entire address space of the object as an anonymous 181 * region to stake out our contiguous region and establish a 182 * base for relocation. 183 * 184 * We map it using the data/BSS protection, then overlay bits 185 * of the file over the top, and unmap the gaps left by padding 186 * to alignment. 187 */ 188 base_offset = round_down(segs[0]->p_offset); 189 base_vaddr = round_down(segs[0]->p_vaddr); 190 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 191 mapsize = base_vlimit - base_vaddr; 192 #ifdef RTLD_LOADER 193 base_addr = u.hdr.e_type == Elf_et_exec ? (caddr_t) base_vaddr : NULL; 194 #else 195 base_addr = NULL; 196 #endif 197 198 mapbase = mmap(base_addr, mapsize, protflags(segs[1]->p_flags), 199 MAP_ANON | MAP_PRIVATE, -1, (off_t) 0); 200 if (mapbase == MAP_FAILED) { 201 _rtld_error("mmap of entire address space failed: %s", 202 xstrerror(errno)); 203 return NULL; 204 } 205 if (base_addr != NULL && mapbase != base_addr) { 206 _rtld_error("mmap returned wrong address: wanted %p, got %p", 207 base_addr, mapbase); 208 munmap(mapbase, mapsize); 209 return NULL; 210 } 211 base_addr = mapbase; 212 213 /* Overlay the text segment onto the proper region. */ 214 text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz); 215 if (mmap(base_addr, text_vlimit - base_vaddr, 216 protflags(segs[0]->p_flags), MAP_FILE | MAP_PRIVATE | MAP_FIXED, 217 fd, base_offset) == MAP_FAILED) { 218 _rtld_error("mmap of text failed: %s", xstrerror(errno)); 219 return NULL; 220 } 221 222 /* Overlay the data segment onto the proper region. */ 223 data_offset = round_down(segs[1]->p_offset); 224 data_vaddr = round_down(segs[1]->p_vaddr); 225 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 226 data_addr = mapbase + (data_vaddr - base_vaddr); 227 if (mmap(data_addr, data_vlimit - data_vaddr, 228 protflags(segs[1]->p_flags), MAP_FILE | MAP_PRIVATE | MAP_FIXED, 229 fd, data_offset) == MAP_FAILED) { 230 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 231 return NULL; 232 } 233 234 /* Unmap the gap between the text and data. */ 235 gap_addr = base_addr + round_up(text_vlimit - base_vaddr); 236 gap_size = data_addr - gap_addr; 237 if (gap_size != 0 && munmap(gap_addr, gap_size) == -1) { 238 _rtld_error("munmap of text -> data gap failed: %s", 239 xstrerror(errno)); 240 return NULL; 241 } 242 243 #ifdef RTLD_LOADER 244 /* Clear any BSS in the last page of the data segment. */ 245 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 246 clear_addr = mapbase + (clear_vaddr - base_vaddr); 247 if ((nclear = data_vlimit - clear_vaddr) > 0) 248 memset(clear_addr, 0, nclear); 249 250 /* Non-file portion of BSS mapped above. */ 251 #endif 252 253 obj = CNEW(Obj_Entry); 254 obj->mapbase = mapbase; 255 obj->mapsize = mapsize; 256 obj->textsize = round_up(segs[0]->p_vaddr + segs[0]->p_memsz) - 257 base_vaddr; 258 obj->vaddrbase = base_vaddr; 259 obj->relocbase = mapbase - base_vaddr; 260 obj->dynamic = (Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr); 261 if (u.hdr.e_entry != 0) 262 obj->entry = (caddr_t)(obj->relocbase + u.hdr.e_entry); 263 if (phphdr != NULL) { 264 obj->phdr = (const Elf_Phdr *) 265 (obj->relocbase + phphdr->p_vaddr); 266 obj->phsize = phphdr->p_memsz; 267 } 268 return obj; 269 } 270 271 /* 272 * Given a set of ELF protection flags, return the corresponding protection 273 * flags for MMAP. 274 */ 275 static int 276 protflags(elfflags) 277 int elfflags; 278 { 279 int prot = 0; 280 if (elfflags & Elf_pf_r) 281 prot |= PROT_READ; 282 #ifdef RTLD_LOADER 283 if (elfflags & Elf_pf_w) 284 prot |= PROT_WRITE; 285 #endif 286 if (elfflags & Elf_pf_x) 287 prot |= PROT_EXEC; 288 return prot; 289 } 290
Indexes created Wed Sep 24 05:09:52 GMT 2025