2 * Copyright 1996-1998 John D. Polstra.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 #include <sys/param.h>
41 static Elf_Ehdr *get_elf_header (int, const char *);
42 static int convert_prot(int); /* Elf flags -> mmap protection */
43 static int convert_flags(int); /* Elf flags -> mmap flags */
46 * Map a shared object into memory. The "fd" argument is a file descriptor,
47 * which must be open on the object and positioned at its beginning.
48 * The "path" argument is a pathname that is used only for error messages.
50 * The return value is a pointer to a newly-allocated Obj_Entry structure
51 * for the shared object. Returns NULL on failure.
54 map_object(int fd, const char *path, const struct stat *sb)
82 size_t nclear, phsize;
90 hdr = get_elf_header(fd, path);
95 * Scan the program header entries, and save key information.
97 * We expect that the loadable segments are ordered by load address.
99 phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff);
100 phsize = hdr->e_phnum * sizeof (phdr[0]);
101 phlimit = phdr + hdr->e_phnum;
103 phdyn = phinterp = phtls = NULL;
107 segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
108 stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W;
109 while (phdr < phlimit) {
110 switch (phdr->p_type) {
117 segs[++nsegs] = phdr;
118 if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) {
119 _rtld_error("%s: PT_LOAD segment %d not page-aligned",
126 phdr_vaddr = phdr->p_vaddr;
127 phsize = phdr->p_memsz;
139 stack_flags = phdr->p_flags;
143 relro_page = phdr->p_vaddr;
144 relro_size = phdr->p_memsz;
151 _rtld_error("%s: object is not dynamically-linked", path);
156 _rtld_error("%s: too few PT_LOAD segments", path);
161 * Map the entire address space of the object, to stake out our
162 * contiguous region, and to establish the base address for relocation.
164 base_offset = trunc_page(segs[0]->p_offset);
165 base_vaddr = trunc_page(segs[0]->p_vaddr);
166 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
167 mapsize = base_vlimit - base_vaddr;
168 base_addr = hdr->e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL;
170 mapbase = mmap(base_addr, mapsize, PROT_NONE, MAP_ANON | MAP_PRIVATE |
172 if (mapbase == (caddr_t) -1) {
173 _rtld_error("%s: mmap of entire address space failed: %s",
174 path, rtld_strerror(errno));
177 if (base_addr != NULL && mapbase != base_addr) {
178 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
179 path, base_addr, mapbase);
180 munmap(mapbase, mapsize);
184 for (i = 0; i <= nsegs; i++) {
185 /* Overlay the segment onto the proper region. */
186 data_offset = trunc_page(segs[i]->p_offset);
187 data_vaddr = trunc_page(segs[i]->p_vaddr);
188 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz);
189 data_addr = mapbase + (data_vaddr - base_vaddr);
190 data_prot = convert_prot(segs[i]->p_flags);
191 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
192 if (mmap(data_addr, data_vlimit - data_vaddr, data_prot,
193 data_flags, fd, data_offset) == (caddr_t) -1) {
194 _rtld_error("%s: mmap of data failed: %s", path,
195 rtld_strerror(errno));
200 if (segs[i]->p_filesz != segs[i]->p_memsz) {
202 /* Clear any BSS in the last page of the segment. */
203 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
204 clear_addr = mapbase + (clear_vaddr - base_vaddr);
205 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr);
207 if ((nclear = data_vlimit - clear_vaddr) > 0) {
208 /* Make sure the end of the segment is writable */
209 if ((data_prot & PROT_WRITE) == 0 && -1 ==
210 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
211 _rtld_error("%s: mprotect failed: %s", path,
212 rtld_strerror(errno));
216 memset(clear_addr, 0, nclear);
219 * reset the data protection back, enable the segment to be
220 * coredumped since we modified it.
222 if ((data_prot & PROT_WRITE) == 0) {
223 madvise(clear_page, PAGE_SIZE, MADV_CORE);
224 mprotect(clear_page, PAGE_SIZE, data_prot);
228 /* Overlay the BSS segment onto the proper region. */
229 bss_vaddr = data_vlimit;
230 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz);
231 bss_addr = mapbase + (bss_vaddr - base_vaddr);
232 if (bss_vlimit > bss_vaddr) { /* There is something to do */
233 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot,
234 data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) {
235 _rtld_error("%s: mmap of bss failed: %s", path,
236 rtld_strerror(errno));
242 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
243 (data_vlimit - data_vaddr + data_offset) >=
244 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) {
245 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
251 obj->dev = sb->st_dev;
252 obj->ino = sb->st_ino;
254 obj->mapbase = mapbase;
255 obj->mapsize = mapsize;
256 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
258 obj->vaddrbase = base_vaddr;
259 obj->relocbase = mapbase - base_vaddr;
260 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
261 if (hdr->e_entry != 0)
262 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry);
263 if (phdr_vaddr != 0) {
264 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr);
266 obj->phdr = malloc(phsize);
267 if (obj->phdr == NULL) {
269 _rtld_error("%s: cannot allocate program header", path);
272 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize);
273 obj->phdr_alloc = true;
275 obj->phsize = phsize;
276 if (phinterp != NULL)
277 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr);
279 tls_dtv_generation++;
280 obj->tlsindex = ++tls_max_index;
281 obj->tlssize = phtls->p_memsz;
282 obj->tlsalign = phtls->p_align;
283 obj->tlsinitsize = phtls->p_filesz;
284 obj->tlsinit = mapbase + phtls->p_vaddr;
286 obj->stack_flags = stack_flags;
288 obj->relro_page = obj->relocbase + trunc_page(relro_page);
289 obj->relro_size = round_page(relro_size);
295 get_elf_header (int fd, const char *path)
303 if ((nbytes = pread(fd, u.buf, PAGE_SIZE, 0)) == -1) {
304 _rtld_error("%s: read error: %s", path, rtld_strerror(errno));
308 /* Make sure the file is valid */
309 if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) {
310 _rtld_error("%s: invalid file format", path);
313 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS
314 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) {
315 _rtld_error("%s: unsupported file layout", path);
318 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT
319 || u.hdr.e_version != EV_CURRENT) {
320 _rtld_error("%s: unsupported file version", path);
323 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) {
324 _rtld_error("%s: unsupported file type", path);
327 if (u.hdr.e_machine != ELF_TARG_MACH) {
328 _rtld_error("%s: unsupported machine", path);
333 * We rely on the program header being in the first page. This is
334 * not strictly required by the ABI specification, but it seems to
335 * always true in practice. And, it simplifies things considerably.
337 if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) {
339 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
342 if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) {
343 _rtld_error("%s: program header too large", path);
351 obj_free(Obj_Entry *obj)
356 free_tls_offset(obj);
357 while (obj->needed != NULL) {
358 Needed_Entry *needed = obj->needed;
359 obj->needed = needed->next;
362 while (!STAILQ_EMPTY(&obj->names)) {
363 Name_Entry *entry = STAILQ_FIRST(&obj->names);
364 STAILQ_REMOVE_HEAD(&obj->names, link);
367 while (!STAILQ_EMPTY(&obj->dldags)) {
368 elm = STAILQ_FIRST(&obj->dldags);
369 STAILQ_REMOVE_HEAD(&obj->dldags, link);
372 while (!STAILQ_EMPTY(&obj->dagmembers)) {
373 elm = STAILQ_FIRST(&obj->dagmembers);
374 STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
379 if (obj->origin_path)
380 free(obj->origin_path);
388 free((void *)obj->phdr);
397 obj = CNEW(Obj_Entry);
398 STAILQ_INIT(&obj->dldags);
399 STAILQ_INIT(&obj->dagmembers);
400 STAILQ_INIT(&obj->names);
405 * Given a set of ELF protection flags, return the corresponding protection
409 convert_prot(int elfflags)
422 convert_flags(int elfflags)
424 int flags = MAP_PRIVATE; /* All mappings are private */
427 * Readonly mappings are marked "MAP_NOCORE", because they can be
428 * reconstructed by a debugger.
430 if (!(elfflags & PF_W))