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 *);
44 static int convert_flags(int); /* Elf flags -> mmap flags */
46 int __getosreldate(void);
49 * Map a shared object into memory. The "fd" argument is a file descriptor,
50 * which must be open on the object and positioned at its beginning.
51 * The "path" argument is a pathname that is used only for error messages.
53 * The return value is a pointer to a newly-allocated Obj_Entry structure
54 * for the shared object. Returns NULL on failure.
57 map_object(int fd, const char *path, const struct stat *sb)
85 size_t nclear, phsize;
97 hdr = get_elf_header(fd, path, sb);
102 * Scan the program header entries, and save key information.
104 * We expect that the loadable segments are ordered by load address.
106 phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff);
107 phsize = hdr->e_phnum * sizeof (phdr[0]);
108 phlimit = phdr + hdr->e_phnum;
110 phdyn = phinterp = phtls = NULL;
117 segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
118 stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W;
119 while (phdr < phlimit) {
120 switch (phdr->p_type) {
127 segs[++nsegs] = phdr;
128 if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) {
129 _rtld_error("%s: PT_LOAD segment %d not page-aligned",
136 phdr_vaddr = phdr->p_vaddr;
137 phsize = phdr->p_memsz;
149 stack_flags = phdr->p_flags;
153 relro_page = phdr->p_vaddr;
154 relro_size = phdr->p_memsz;
158 if (phdr->p_offset > PAGE_SIZE ||
159 phdr->p_offset + phdr->p_filesz > PAGE_SIZE) {
160 note_map_len = round_page(phdr->p_offset +
161 phdr->p_filesz) - trunc_page(phdr->p_offset);
162 note_map = mmap(NULL, note_map_len, PROT_READ,
163 MAP_PRIVATE, fd, trunc_page(phdr->p_offset));
164 if (note_map == MAP_FAILED) {
165 _rtld_error("%s: error mapping PT_NOTE (%d)", path, errno);
168 note_start = (Elf_Addr)(note_map + phdr->p_offset -
169 trunc_page(phdr->p_offset));
171 note_start = (Elf_Addr)(char *)hdr + phdr->p_offset;
173 note_end = note_start + phdr->p_filesz;
180 _rtld_error("%s: object is not dynamically-linked", path);
185 _rtld_error("%s: too few PT_LOAD segments", path);
190 * Map the entire address space of the object, to stake out our
191 * contiguous region, and to establish the base address for relocation.
193 base_vaddr = trunc_page(segs[0]->p_vaddr);
194 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
195 mapsize = base_vlimit - base_vaddr;
196 base_addr = (caddr_t) base_vaddr;
197 base_flags = __getosreldate() >= P_OSREL_MAP_GUARD ? MAP_GUARD :
198 MAP_PRIVATE | MAP_ANON | MAP_NOCORE;
199 if (npagesizes > 1 && round_page(segs[0]->p_filesz) >= pagesizes[1])
200 base_flags |= MAP_ALIGNED_SUPER;
202 base_flags |= MAP_FIXED | MAP_EXCL;
204 mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0);
205 if (mapbase == (caddr_t) -1) {
206 _rtld_error("%s: mmap of entire address space failed: %s",
207 path, rtld_strerror(errno));
210 if (base_addr != NULL && mapbase != base_addr) {
211 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
212 path, base_addr, mapbase);
216 for (i = 0; i <= nsegs; i++) {
217 /* Overlay the segment onto the proper region. */
218 data_offset = trunc_page(segs[i]->p_offset);
219 data_vaddr = trunc_page(segs[i]->p_vaddr);
220 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz);
221 data_addr = mapbase + (data_vaddr - base_vaddr);
222 data_prot = convert_prot(segs[i]->p_flags);
223 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
224 if (mmap(data_addr, data_vlimit - data_vaddr, data_prot,
225 data_flags | MAP_PREFAULT_READ, fd, data_offset) == (caddr_t) -1) {
226 _rtld_error("%s: mmap of data failed: %s", path,
227 rtld_strerror(errno));
232 if (segs[i]->p_filesz != segs[i]->p_memsz) {
234 /* Clear any BSS in the last page of the segment. */
235 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
236 clear_addr = mapbase + (clear_vaddr - base_vaddr);
237 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr);
239 if ((nclear = data_vlimit - clear_vaddr) > 0) {
240 /* Make sure the end of the segment is writable */
241 if ((data_prot & PROT_WRITE) == 0 && -1 ==
242 mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
243 _rtld_error("%s: mprotect failed: %s", path,
244 rtld_strerror(errno));
248 memset(clear_addr, 0, nclear);
250 /* Reset the data protection back */
251 if ((data_prot & PROT_WRITE) == 0)
252 mprotect(clear_page, PAGE_SIZE, data_prot);
255 /* Overlay the BSS segment onto the proper region. */
256 bss_vaddr = data_vlimit;
257 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz);
258 bss_addr = mapbase + (bss_vaddr - base_vaddr);
259 if (bss_vlimit > bss_vaddr) { /* There is something to do */
260 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot,
261 data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) {
262 _rtld_error("%s: mmap of bss failed: %s", path,
263 rtld_strerror(errno));
269 if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
270 (data_vlimit - data_vaddr + data_offset) >=
271 (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) {
272 phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
278 obj->dev = sb->st_dev;
279 obj->ino = sb->st_ino;
281 obj->mapbase = mapbase;
282 obj->mapsize = mapsize;
283 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
285 obj->vaddrbase = base_vaddr;
286 obj->relocbase = mapbase - base_vaddr;
287 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
288 if (hdr->e_entry != 0)
289 obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry);
290 if (phdr_vaddr != 0) {
291 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr);
293 obj->phdr = malloc(phsize);
294 if (obj->phdr == NULL) {
296 _rtld_error("%s: cannot allocate program header", path);
299 memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize);
300 obj->phdr_alloc = true;
302 obj->phsize = phsize;
303 if (phinterp != NULL)
304 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr);
306 tls_dtv_generation++;
307 obj->tlsindex = ++tls_max_index;
308 obj->tlssize = phtls->p_memsz;
309 obj->tlsalign = phtls->p_align;
310 obj->tlsinitsize = phtls->p_filesz;
311 obj->tlsinit = mapbase + phtls->p_vaddr;
313 obj->stack_flags = stack_flags;
314 obj->relro_page = obj->relocbase + trunc_page(relro_page);
315 obj->relro_size = round_page(relro_size);
316 if (note_start < note_end)
317 digest_notes(obj, note_start, note_end);
318 if (note_map != NULL)
319 munmap(note_map, note_map_len);
320 munmap(hdr, PAGE_SIZE);
324 munmap(mapbase, mapsize);
326 if (note_map != NULL && note_map != MAP_FAILED)
327 munmap(note_map, note_map_len);
328 munmap(hdr, PAGE_SIZE);
333 get_elf_header(int fd, const char *path, const struct stat *sbp)
337 /* Make sure file has enough data for the ELF header */
338 if (sbp != NULL && sbp->st_size < sizeof(Elf_Ehdr)) {
339 _rtld_error("%s: invalid file format", path);
343 hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ,
345 if (hdr == (Elf_Ehdr *)MAP_FAILED) {
346 _rtld_error("%s: read error: %s", path, rtld_strerror(errno));
350 /* Make sure the file is valid */
352 _rtld_error("%s: invalid file format", path);
355 if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
356 hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
357 _rtld_error("%s: unsupported file layout", path);
360 if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
361 hdr->e_version != EV_CURRENT) {
362 _rtld_error("%s: unsupported file version", path);
365 if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
366 _rtld_error("%s: unsupported file type", path);
369 if (hdr->e_machine != ELF_TARG_MACH) {
370 _rtld_error("%s: unsupported machine", path);
375 * We rely on the program header being in the first page. This is
376 * not strictly required by the ABI specification, but it seems to
377 * always true in practice. And, it simplifies things considerably.
379 if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
381 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
384 if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) >
386 _rtld_error("%s: program header too large", path);
392 munmap(hdr, PAGE_SIZE);
397 obj_free(Obj_Entry *obj)
402 free_tls_offset(obj);
403 while (obj->needed != NULL) {
404 Needed_Entry *needed = obj->needed;
405 obj->needed = needed->next;
408 while (!STAILQ_EMPTY(&obj->names)) {
409 Name_Entry *entry = STAILQ_FIRST(&obj->names);
410 STAILQ_REMOVE_HEAD(&obj->names, link);
413 while (!STAILQ_EMPTY(&obj->dldags)) {
414 elm = STAILQ_FIRST(&obj->dldags);
415 STAILQ_REMOVE_HEAD(&obj->dldags, link);
418 while (!STAILQ_EMPTY(&obj->dagmembers)) {
419 elm = STAILQ_FIRST(&obj->dagmembers);
420 STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
425 if (obj->origin_path)
426 free(obj->origin_path);
434 free((void *)obj->phdr);
443 obj = CNEW(Obj_Entry);
444 STAILQ_INIT(&obj->dldags);
445 STAILQ_INIT(&obj->dagmembers);
446 STAILQ_INIT(&obj->names);
451 * Given a set of ELF protection flags, return the corresponding protection
455 convert_prot(int elfflags)
468 convert_flags(int elfflags)
470 int flags = MAP_PRIVATE; /* All mappings are private */
473 * Readonly mappings are marked "MAP_NOCORE", because they can be
474 * reconstructed by a debugger.
476 if (!(elfflags & PF_W))