map_object.c revision 1.1
1 /* $NetBSD: map_object.c,v 1.1 1996/12/16 20:38:01 cgd 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(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( 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 caddr_t base_addr; 81 Elf_Off data_offset; 82 Elf_Addr data_vaddr; 83 Elf_Addr data_vlimit; 84 caddr_t data_addr; 85 #ifdef RTLD_LOADER 86 Elf_Addr clear_vaddr; 87 caddr_t clear_addr; 88 size_t nclear; 89 Elf_Addr bss_vaddr; 90 Elf_Addr bss_vlimit; 91 caddr_t bss_addr; 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 99 /* Make sure the file is valid */ 100 if (nbytes < sizeof(Elf_Ehdr) 101 || memcmp(Elf_e_ident, u.hdr.e_ident, Elf_e_siz) != 0) { 102 _rtld_error("%s: unrecognized file format", path); 103 return NULL; 104 } 105 /* Elf_e_ident includes class */ 106 if (u.hdr.e_ident[Elf_ei_version] != Elf_ev_current 107 || u.hdr.e_version != Elf_ev_current 108 || u.hdr.e_ident[Elf_ei_data] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) { 109 _rtld_error("%s: Unsupported file version", path); 110 return NULL; 111 } 112 if (u.hdr.e_type != Elf_et_exec && u.hdr.e_type != Elf_et_dyn) { 113 _rtld_error("%s: Unsupported file type", path); 114 return NULL; 115 } 116 switch (u.hdr.e_machine) { 117 ELFDEFNNAME(MACHDEP_ID_CASES) 118 119 default: 120 _rtld_error("%s: Unsupported machine", path); 121 return NULL; 122 } 123 124 /* 125 * We rely on the program header being in the first page. This is 126 * not strictly required by the ABI specification, but it seems to 127 * always true in practice. And, it simplifies things considerably. 128 */ 129 assert(u.hdr.e_phentsize == sizeof(Elf_Phdr)); 130 assert(u.hdr.e_phoff + u.hdr.e_phnum*sizeof(Elf_Phdr) <= PAGESIZE); 131 assert(u.hdr.e_phoff + u.hdr.e_phnum*sizeof(Elf_Phdr) <= nbytes); 132 133 /* 134 * Scan the program header entries, and save key information. 135 * 136 * We rely on there being exactly two load segments, text and data, 137 * in that order. 138 */ 139 phdr = (Elf_Phdr *) (u.buf + u.hdr.e_phoff); 140 phlimit = phdr + u.hdr.e_phnum; 141 nsegs = 0; 142 phdyn = NULL; 143 phphdr = NULL; 144 while(phdr < phlimit) { 145 switch(phdr->p_type) { 146 147 case Elf_pt_load: 148 assert(nsegs < 2); 149 segs[nsegs] = phdr; 150 ++nsegs; 151 break; 152 153 case Elf_pt_phdr: 154 phphdr = phdr; 155 break; 156 157 case Elf_pt_dynamic: 158 phdyn = phdr; 159 break; 160 } 161 162 ++phdr; 163 } 164 if (phdyn == NULL) { 165 _rtld_error("%s: not dynamically-linked", path); 166 return NULL; 167 } 168 169 assert(nsegs == 2); 170 #ifdef __i386__ 171 assert(segs[0]->p_align <= PAGESIZE); 172 assert(segs[1]->p_align <= PAGESIZE); 173 #endif 174 175 /* 176 * Map the entire address space of the object, to stake out our 177 * contiguous region, and to establish the base address for relocation. 178 */ 179 base_offset = round_down(segs[0]->p_offset); 180 base_vaddr = round_down(segs[0]->p_vaddr); 181 base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 182 mapsize = base_vlimit - base_vaddr; 183 #ifdef RTLD_LOADER 184 base_addr = u.hdr.e_type == Elf_et_exec ? (caddr_t) base_vaddr : NULL; 185 #else 186 base_addr = NULL; 187 #endif 188 189 mapbase = mmap(base_addr, mapsize, protflags(segs[0]->p_flags), 190 MAP_PRIVATE, fd, base_offset); 191 if (mapbase == (caddr_t) -1) { 192 _rtld_error("mmap of entire address space failed: %s", xstrerror(errno)); 193 return NULL; 194 } 195 if (base_addr != NULL && mapbase != base_addr) { 196 _rtld_error("mmap returned wrong address: wanted %p, got %p", base_addr, 197 mapbase); 198 munmap(mapbase, mapsize); 199 return NULL; 200 } 201 202 /* Overlay the data segment onto the proper region. */ 203 data_offset = round_down(segs[1]->p_offset); 204 data_vaddr = round_down(segs[1]->p_vaddr); 205 data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz); 206 data_addr = mapbase + (data_vaddr - base_vaddr); 207 if (mmap(data_addr, data_vlimit - data_vaddr, protflags(segs[1]->p_flags), 208 MAP_PRIVATE|MAP_FIXED, fd, data_offset) == (caddr_t) -1) { 209 _rtld_error("mmap of data failed: %s", xstrerror(errno)); 210 return NULL; 211 } 212 213 #ifdef RTLD_LOADER 214 /* Clear any BSS in the last page of the data segment. */ 215 clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz; 216 clear_addr = mapbase + (clear_vaddr - base_vaddr); 217 if ((nclear = data_vlimit - clear_vaddr) > 0) 218 memset(clear_addr, 0, nclear); 219 220 /* Overlay the BSS segment onto the proper region. */ 221 bss_vaddr = data_vlimit; 222 bss_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz); 223 bss_addr = mapbase + (bss_vaddr - base_vaddr); 224 if (bss_vlimit > bss_vaddr) { /* There is something to do */ 225 if (mmap(bss_addr, bss_vlimit - bss_vaddr, protflags(segs[1]->p_flags), 226 MAP_PRIVATE|MAP_FIXED|MAP_ANON, -1, 0) == (caddr_t) -1) { 227 _rtld_error("mmap of bss failed: %s", xstrerror(errno)); 228 return NULL; 229 } 230 } 231 #endif 232 233 obj = CNEW(Obj_Entry); 234 obj->mapbase = mapbase; 235 obj->mapsize = mapsize; 236 obj->textsize = round_up(segs[0]->p_vaddr + segs[0]->p_memsz) - base_vaddr; 237 obj->vaddrbase = base_vaddr; 238 obj->relocbase = mapbase - base_vaddr; 239 obj->dynamic = (Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr); 240 if (u.hdr.e_entry != 0) 241 obj->entry = (caddr_t) (obj->relocbase + u.hdr.e_entry); 242 if (phphdr != NULL) { 243 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phphdr->p_vaddr); 244 obj->phsize = phphdr->p_memsz; 245 } 246 247 return obj; 248 } 249 250 /* 251 * Given a set of ELF protection flags, return the corresponding protection 252 * flags for MMAP. 253 */ 254 static int 255 protflags(int elfflags) 256 { 257 int prot = 0; 258 if (elfflags & Elf_pf_r) prot |= PROT_READ; 259 #ifdef RTLD_LOADER 260 if (elfflags & Elf_pf_w) prot |= PROT_WRITE; 261 #endif 262 if (elfflags & Elf_pf_x) prot |= PROT_EXEC; 263 return prot; 264 } 265
Indexes created Tue Sep 23 07:09:52 GMT 2025