2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright 1996-1998 John D. Polstra.
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 #include <sys/param.h>
43 static Elf_Ehdr *get_elf_header(int, const char *, const struct stat *,
45 static int convert_flags(int); /* Elf flags -> mmap flags */
47 int __getosreldate(void);
50 phdr_in_zero_page(const Elf_Ehdr *hdr)
52 return (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) <=
57 * Map a shared object into memory. The "fd" argument is a file descriptor,
58 * which must be open on the object and positioned at its beginning.
59 * The "path" argument is a pathname that is used only for error messages.
61 * The return value is a pointer to a newly-allocated Obj_Entry structure
62 * for the shared object. Returns NULL on failure.
65 map_object(int fd, const char *path, const struct stat *sb)
93 size_t nclear, phsize;
106 hdr = get_elf_header(fd, path, sb, &phdr);
111 * Scan the program header entries, and save key information.
112 * We expect that the loadable segments are ordered by load address.
114 phsize = hdr->e_phnum * sizeof(phdr[0]);
115 phlimit = phdr + hdr->e_phnum;
117 phdyn = phinterp = phtls = NULL;
125 segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
126 stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W;
128 while (phdr < phlimit) {
129 switch (phdr->p_type) {
136 segs[++nsegs] = phdr;
137 if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) {
138 _rtld_error("%s: PT_LOAD segment %d not page-aligned",
142 if ((segs[nsegs]->p_flags & PF_X) == PF_X) {
143 text_end = MAX(text_end,
144 round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz));
149 phdr_vaddr = phdr->p_vaddr;
150 phsize = phdr->p_memsz;
162 stack_flags = phdr->p_flags;
166 relro_page = phdr->p_vaddr;
167 relro_size = phdr->p_memsz;
171 if (phdr->p_offset > PAGE_SIZE ||
172 phdr->p_offset + phdr->p_filesz > PAGE_SIZE) {
173 note_map_len = round_page(phdr->p_offset +
174 phdr->p_filesz) - trunc_page(phdr->p_offset);
175 note_map = mmap(NULL, note_map_len, PROT_READ,
176 MAP_PRIVATE, fd, trunc_page(phdr->p_offset));
177 if (note_map == MAP_FAILED) {
178 _rtld_error("%s: error mapping PT_NOTE (%d)", path, errno);
181 note_start = (Elf_Addr)(note_map + phdr->p_offset -
182 trunc_page(phdr->p_offset));
184 note_start = (Elf_Addr)(char *)hdr + phdr->p_offset;
186 note_end = note_start + phdr->p_filesz;
193 _rtld_error("%s: object is not dynamically-linked", path);
198 _rtld_error("%s: too few PT_LOAD segments", path);
203 * Map the entire address space of the object, to stake out our
204 * contiguous region, and to establish the base address for relocation.
206 base_vaddr = trunc_page(segs[0]->p_vaddr);
207 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
208 mapsize = base_vlimit - base_vaddr;
209 base_addr = (caddr_t) base_vaddr;
210 base_flags = __getosreldate() >= P_OSREL_MAP_GUARD ? MAP_GUARD :
211 MAP_PRIVATE | MAP_ANON | MAP_NOCORE;
212 if (npagesizes > 1 && round_page(segs[0]->p_filesz) >= pagesizes[1])
213 base_flags |= MAP_ALIGNED_SUPER;
215 base_flags |= MAP_FIXED | MAP_EXCL;
217 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0);
218 if (mapbase == MAP_FAILED) {
219 _rtld_error("%s: mmap of entire address space failed: %s",
220 path, rtld_strerror(errno));
223 if (base_addr != NULL && mapbase != base_addr) {
224 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
225 path, base_addr, mapbase);
229 for (i = 0; i <= nsegs; i++) {
230 /* Overlay the segment onto the proper region. */
231 data_offset = trunc_page(segs[i]->p_offset);
232 data_vaddr = trunc_page(segs[i]->p_vaddr);
233 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz);
234 data_addr = mapbase + (data_vaddr - base_vaddr);
235 data_prot = convert_prot(segs[i]->p_flags);
236 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
237 if (data_vlimit != data_vaddr &&
238 mmap(data_addr, data_vlimit - data_vaddr, data_prot,
239 data_flags | MAP_PREFAULT_READ, fd, data_offset) == MAP_FAILED) {
240 _rtld_error("%s: mmap of data failed: %s", path,
241 rtld_strerror(errno));
246 if (segs[i]->p_filesz != segs[i]->p_memsz) {
248 /* Clear any BSS in the last page of the segment. */
249 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
250 clear_addr = mapbase + (clear_vaddr - base_vaddr);
251 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr);
253 if ((nclear = data_vlimit - clear_vaddr) > 0) {
254 /* Make sure the end of the segment is writable */
255 if ((data_prot & PROT_WRITE) == 0 && -1 ==
256 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
257 _rtld_error("%s: mprotect failed: %s", path,
258 rtld_strerror(errno));
262 memset(clear_addr, 0, nclear);
264 /* Reset the data protection back */
265 if ((data_prot & PROT_WRITE) == 0)
266 mprotect(clear_page, PAGE_SIZE, data_prot);
269 /* Overlay the BSS segment onto the proper region. */
270 bss_vaddr = data_vlimit;
271 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz);
272 bss_addr = mapbase + (bss_vaddr - base_vaddr);
273 if (bss_vlimit > bss_vaddr) { /* There is something to do */
274 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot,
275 data_flags | MAP_ANON, -1, 0) == MAP_FAILED) {
276 _rtld_error("%s: mmap of bss failed: %s", path,
277 rtld_strerror(errno));
283 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
284 (data_vlimit - data_vaddr + data_offset) >=
285 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) {
286 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
292 obj->dev = sb->st_dev;
293 obj->ino = sb->st_ino;
295 obj->mapbase = mapbase;
296 obj->mapsize = mapsize;
297 obj->vaddrbase = base_vaddr;
298 obj->relocbase = mapbase - base_vaddr;
299 obj->dynamic = (const Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr);
300 if (hdr->e_entry != 0)
301 obj->entry = (caddr_t)(obj->relocbase + hdr->e_entry);
302 if (phdr_vaddr != 0) {
303 obj->phdr = (const Elf_Phdr *)(obj->relocbase + phdr_vaddr);
305 obj->phdr = malloc(phsize);
306 if (obj->phdr == NULL) {
308 _rtld_error("%s: cannot allocate program header", path);
311 memcpy(__DECONST(char *, obj->phdr), (char *)hdr + hdr->e_phoff, phsize);
312 obj->phdr_alloc = true;
314 obj->phsize = phsize;
315 if (phinterp != NULL)
316 obj->interp = (const char *)(obj->relocbase + phinterp->p_vaddr);
318 tls_dtv_generation++;
319 obj->tlsindex = ++tls_max_index;
320 obj->tlssize = phtls->p_memsz;
321 obj->tlsalign = phtls->p_align;
322 obj->tlspoffset = phtls->p_offset;
323 obj->tlsinitsize = phtls->p_filesz;
324 obj->tlsinit = mapbase + phtls->p_vaddr;
326 obj->stack_flags = stack_flags;
327 obj->relro_page = obj->relocbase + trunc_page(relro_page);
328 obj->relro_size = round_page(relro_size);
329 if (note_start < note_end)
330 digest_notes(obj, note_start, note_end);
331 if (note_map != NULL)
332 munmap(note_map, note_map_len);
333 munmap(hdr, PAGE_SIZE);
337 munmap(mapbase, mapsize);
339 if (note_map != NULL && note_map != MAP_FAILED)
340 munmap(note_map, note_map_len);
341 if (!phdr_in_zero_page(hdr))
342 munmap(phdr, hdr->e_phnum * sizeof(phdr[0]));
343 munmap(hdr, PAGE_SIZE);
348 get_elf_header(int fd, const char *path, const struct stat *sbp,
354 /* Make sure file has enough data for the ELF header */
355 if (sbp != NULL && sbp->st_size < (off_t)sizeof(Elf_Ehdr)) {
356 _rtld_error("%s: invalid file format", path);
360 hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ,
362 if (hdr == MAP_FAILED) {
363 _rtld_error("%s: read error: %s", path, rtld_strerror(errno));
367 /* Make sure the file is valid */
369 _rtld_error("%s: invalid file format", path);
372 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
373 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
374 _rtld_error("%s: unsupported file layout", path);
377 if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
378 hdr->e_version != EV_CURRENT) {
379 _rtld_error("%s: unsupported file version", path);
382 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
383 _rtld_error("%s: unsupported file type", path);
386 if (hdr->e_machine != ELF_TARG_MACH) {
387 _rtld_error("%s: unsupported machine", path);
392 * We rely on the program header being in the first page. This is
393 * not strictly required by the ABI specification, but it seems to
394 * always true in practice. And, it simplifies things considerably.
396 if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
398 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
401 if (phdr_in_zero_page(hdr)) {
402 phdr = (Elf_Phdr *)((char *)hdr + hdr->e_phoff);
404 phdr = mmap(NULL, hdr->e_phnum * sizeof(phdr[0]),
405 PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ, fd,
407 if (phdr == MAP_FAILED) {
408 _rtld_error("%s: error mapping phdr: %s", path,
409 rtld_strerror(errno));
417 munmap(hdr, PAGE_SIZE);
422 obj_free(Obj_Entry *obj)
427 free_tls_offset(obj);
428 while (obj->needed != NULL) {
429 Needed_Entry *needed = obj->needed;
430 obj->needed = needed->next;
433 while (!STAILQ_EMPTY(&obj->names)) {
434 Name_Entry *entry = STAILQ_FIRST(&obj->names);
435 STAILQ_REMOVE_HEAD(&obj->names, link);
438 while (!STAILQ_EMPTY(&obj->dldags)) {
439 elm = STAILQ_FIRST(&obj->dldags);
440 STAILQ_REMOVE_HEAD(&obj->dldags, link);
443 while (!STAILQ_EMPTY(&obj->dagmembers)) {
444 elm = STAILQ_FIRST(&obj->dagmembers);
445 STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
450 if (obj->origin_path)
451 free(obj->origin_path);
453 free(__DECONST(void*, obj->rpath));
459 free(__DECONST(void *, obj->phdr));
468 obj = CNEW(Obj_Entry);
469 STAILQ_INIT(&obj->dldags);
470 STAILQ_INIT(&obj->dagmembers);
471 STAILQ_INIT(&obj->names);
476 * Given a set of ELF protection flags, return the corresponding protection
480 convert_prot(int elfflags)
493 convert_flags(int elfflags)
495 int flags = MAP_PRIVATE; /* All mappings are private */
498 * Readonly mappings are marked "MAP_NOCORE", because they can be
499 * reconstructed by a debugger.
501 if (!(elfflags & PF_W))