1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright 1996-1998 John D. Polstra.
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
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.
15  *
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.
26  *
27  * $FreeBSD$
28  */
29 
30 #include <sys/param.h>
31 #include <sys/mman.h>
32 #include <sys/stat.h>
33 
34 #include <errno.h>
35 #include <stddef.h>
36 #include <stdlib.h>
37 #include <string.h>
38 #include <unistd.h>
39 
40 #include "debug.h"
41 #include "rtld.h"
42 
43 static Elf_Ehdr *get_elf_header(int, const char *, const struct stat *);
44 static int convert_flags(int); /* Elf flags -> mmap flags */
45 
46 int __getosreldate(void);
47 
48 /*
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.
52  *
53  * The return value is a pointer to a newly-allocated Obj_Entry structure
54  * for the shared object.  Returns NULL on failure.
55  */
56 Obj_Entry *
57 map_object(int fd, const char *path, const struct stat *sb)
58 {
59     Obj_Entry *obj;
60     Elf_Ehdr *hdr;
61     int i;
62     Elf_Phdr *phdr;
63     Elf_Phdr *phlimit;
64     Elf_Phdr **segs;
65     int nsegs;
66     Elf_Phdr *phdyn;
67     Elf_Phdr *phinterp;
68     Elf_Phdr *phtls;
69     caddr_t mapbase;
70     size_t mapsize;
71     Elf_Addr base_vaddr;
72     Elf_Addr base_vlimit;
73     caddr_t base_addr;
74     int base_flags;
75     Elf_Off data_offset;
76     Elf_Addr data_vaddr;
77     Elf_Addr data_vlimit;
78     caddr_t data_addr;
79     int data_prot;
80     int data_flags;
81     Elf_Addr clear_vaddr;
82     caddr_t clear_addr;
83     caddr_t clear_page;
84     Elf_Addr phdr_vaddr;
85     size_t nclear, phsize;
86     Elf_Addr bss_vaddr;
87     Elf_Addr bss_vlimit;
88     caddr_t bss_addr;
89     Elf_Word stack_flags;
90     Elf_Addr relro_page;
91     size_t relro_size;
92     Elf_Addr note_start;
93     Elf_Addr note_end;
94     char *note_map;
95     size_t note_map_len;
96 
97     hdr = get_elf_header(fd, path, sb);
98     if (hdr == NULL)
99 	return (NULL);
100 
101     /*
102      * Scan the program header entries, and save key information.
103      *
104      * We expect that the loadable segments are ordered by load address.
105      */
106     phdr = (Elf_Phdr *)((char *)hdr + hdr->e_phoff);
107     phsize  = hdr->e_phnum * sizeof (phdr[0]);
108     phlimit = phdr + hdr->e_phnum;
109     nsegs = -1;
110     phdyn = phinterp = phtls = NULL;
111     phdr_vaddr = 0;
112     relro_page = 0;
113     relro_size = 0;
114     note_start = 0;
115     note_end = 0;
116     note_map = NULL;
117     note_map_len = 0;
118     segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
119     stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W;
120     while (phdr < phlimit) {
121 	switch (phdr->p_type) {
122 
123 	case PT_INTERP:
124 	    phinterp = phdr;
125 	    break;
126 
127 	case PT_LOAD:
128 	    segs[++nsegs] = phdr;
129     	    if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) {
130 		_rtld_error("%s: PT_LOAD segment %d not page-aligned",
131 		    path, nsegs);
132 		goto error;
133 	    }
134 	    break;
135 
136 	case PT_PHDR:
137 	    phdr_vaddr = phdr->p_vaddr;
138 	    phsize = phdr->p_memsz;
139 	    break;
140 
141 	case PT_DYNAMIC:
142 	    phdyn = phdr;
143 	    break;
144 
145 	case PT_TLS:
146 	    phtls = phdr;
147 	    break;
148 
149 	case PT_GNU_STACK:
150 	    stack_flags = phdr->p_flags;
151 	    break;
152 
153 	case PT_GNU_RELRO:
154 	    relro_page = phdr->p_vaddr;
155 	    relro_size = phdr->p_memsz;
156 	    break;
157 
158 	case PT_NOTE:
159 	    if (phdr->p_offset > PAGE_SIZE ||
160 	      phdr->p_offset + phdr->p_filesz > PAGE_SIZE) {
161 		note_map_len = round_page(phdr->p_offset +
162 		  phdr->p_filesz) - trunc_page(phdr->p_offset);
163 		note_map = mmap(NULL, note_map_len, PROT_READ,
164 		  MAP_PRIVATE, fd, trunc_page(phdr->p_offset));
165 		if (note_map == MAP_FAILED) {
166 		    _rtld_error("%s: error mapping PT_NOTE (%d)", path, errno);
167 		    goto error;
168 		}
169 		note_start = (Elf_Addr)(note_map + phdr->p_offset -
170 		  trunc_page(phdr->p_offset));
171 	    } else {
172 		note_start = (Elf_Addr)(char *)hdr + phdr->p_offset;
173 	    }
174 	    note_end = note_start + phdr->p_filesz;
175 	    break;
176 	}
177 
178 	++phdr;
179     }
180     if (phdyn == NULL) {
181 	_rtld_error("%s: object is not dynamically-linked", path);
182 	goto error;
183     }
184 
185     if (nsegs < 0) {
186 	_rtld_error("%s: too few PT_LOAD segments", path);
187 	goto error;
188     }
189 
190     /*
191      * Map the entire address space of the object, to stake out our
192      * contiguous region, and to establish the base address for relocation.
193      */
194     base_vaddr = trunc_page(segs[0]->p_vaddr);
195     base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
196     mapsize = base_vlimit - base_vaddr;
197     base_addr = (caddr_t) base_vaddr;
198     base_flags = __getosreldate() >= P_OSREL_MAP_GUARD ? MAP_GUARD :
199 	MAP_PRIVATE | MAP_ANON | MAP_NOCORE;
200     if (npagesizes > 1 && round_page(segs[0]->p_filesz) >= pagesizes[1])
201 	base_flags |= MAP_ALIGNED_SUPER;
202     if (base_vaddr != 0)
203 	base_flags |= MAP_FIXED | MAP_EXCL;
204 
205     mapbase = mmap(base_addr, mapsize, PROT_NONE, base_flags, -1, 0);
206     if (mapbase == (caddr_t) -1) {
207 	_rtld_error("%s: mmap of entire address space failed: %s",
208 	  path, rtld_strerror(errno));
209 	goto error;
210     }
211     if (base_addr != NULL && mapbase != base_addr) {
212 	_rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
213 	  path, base_addr, mapbase);
214 	goto error1;
215     }
216 
217     for (i = 0; i <= nsegs; i++) {
218 	/* Overlay the segment onto the proper region. */
219 	data_offset = trunc_page(segs[i]->p_offset);
220 	data_vaddr = trunc_page(segs[i]->p_vaddr);
221 	data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz);
222 	data_addr = mapbase + (data_vaddr - base_vaddr);
223 	data_prot = convert_prot(segs[i]->p_flags);
224 	data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
225 	if (mmap(data_addr, data_vlimit - data_vaddr, data_prot,
226 	  data_flags | MAP_PREFAULT_READ, fd, data_offset) == (caddr_t) -1) {
227 	    _rtld_error("%s: mmap of data failed: %s", path,
228 		rtld_strerror(errno));
229 	    goto error1;
230 	}
231 
232 	/* Do BSS setup */
233 	if (segs[i]->p_filesz != segs[i]->p_memsz) {
234 
235 	    /* Clear any BSS in the last page of the segment. */
236 	    clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
237 	    clear_addr = mapbase + (clear_vaddr - base_vaddr);
238 	    clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr);
239 
240 	    if ((nclear = data_vlimit - clear_vaddr) > 0) {
241 		/* Make sure the end of the segment is writable */
242 		if ((data_prot & PROT_WRITE) == 0 && -1 ==
243 		     mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
244 			_rtld_error("%s: mprotect failed: %s", path,
245 			    rtld_strerror(errno));
246 			goto error1;
247 		}
248 
249 		memset(clear_addr, 0, nclear);
250 
251 		/* Reset the data protection back */
252 		if ((data_prot & PROT_WRITE) == 0)
253 		    mprotect(clear_page, PAGE_SIZE, data_prot);
254 	    }
255 
256 	    /* Overlay the BSS segment onto the proper region. */
257 	    bss_vaddr = data_vlimit;
258 	    bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz);
259 	    bss_addr = mapbase +  (bss_vaddr - base_vaddr);
260 	    if (bss_vlimit > bss_vaddr) {	/* There is something to do */
261 		if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot,
262 		    data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) {
263 		    _rtld_error("%s: mmap of bss failed: %s", path,
264 			rtld_strerror(errno));
265 		    goto error1;
266 		}
267 	    }
268 	}
269 
270 	if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
271 	  (data_vlimit - data_vaddr + data_offset) >=
272 	  (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) {
273 	    phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
274 	}
275     }
276 
277     obj = obj_new();
278     if (sb != NULL) {
279 	obj->dev = sb->st_dev;
280 	obj->ino = sb->st_ino;
281     }
282     obj->mapbase = mapbase;
283     obj->mapsize = mapsize;
284     obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
285       base_vaddr;
286     obj->vaddrbase = base_vaddr;
287     obj->relocbase = mapbase - base_vaddr;
288     obj->dynamic = (const Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr);
289     if (hdr->e_entry != 0)
290 	obj->entry = (caddr_t)(obj->relocbase + hdr->e_entry);
291     if (phdr_vaddr != 0) {
292 	obj->phdr = (const Elf_Phdr *)(obj->relocbase + phdr_vaddr);
293     } else {
294 	obj->phdr = malloc(phsize);
295 	if (obj->phdr == NULL) {
296 	    obj_free(obj);
297 	    _rtld_error("%s: cannot allocate program header", path);
298 	    goto error1;
299 	}
300 	memcpy(__DECONST(char *, obj->phdr), (char *)hdr + hdr->e_phoff, phsize);
301 	obj->phdr_alloc = true;
302     }
303     obj->phsize = phsize;
304     if (phinterp != NULL)
305 	obj->interp = (const char *)(obj->relocbase + phinterp->p_vaddr);
306     if (phtls != NULL) {
307 	tls_dtv_generation++;
308 	obj->tlsindex = ++tls_max_index;
309 	obj->tlssize = phtls->p_memsz;
310 	obj->tlsalign = phtls->p_align;
311 	obj->tlsinitsize = phtls->p_filesz;
312 	obj->tlsinit = mapbase + phtls->p_vaddr;
313     }
314     obj->stack_flags = stack_flags;
315     obj->relro_page = obj->relocbase + trunc_page(relro_page);
316     obj->relro_size = round_page(relro_size);
317     if (note_start < note_end)
318 	digest_notes(obj, note_start, note_end);
319     if (note_map != NULL)
320 	munmap(note_map, note_map_len);
321     munmap(hdr, PAGE_SIZE);
322     return (obj);
323 
324 error1:
325     munmap(mapbase, mapsize);
326 error:
327     if (note_map != NULL && note_map != MAP_FAILED)
328 	munmap(note_map, note_map_len);
329     munmap(hdr, PAGE_SIZE);
330     return (NULL);
331 }
332 
333 static Elf_Ehdr *
334 get_elf_header(int fd, const char *path, const struct stat *sbp)
335 {
336 	Elf_Ehdr *hdr;
337 
338 	/* Make sure file has enough data for the ELF header */
339 	if (sbp != NULL && sbp->st_size < (off_t)sizeof(Elf_Ehdr)) {
340 		_rtld_error("%s: invalid file format", path);
341 		return (NULL);
342 	}
343 
344 	hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ,
345 	    fd, 0);
346 	if (hdr == (Elf_Ehdr *)MAP_FAILED) {
347 		_rtld_error("%s: read error: %s", path, rtld_strerror(errno));
348 		return (NULL);
349 	}
350 
351 	/* Make sure the file is valid */
352 	if (!IS_ELF(*hdr)) {
353 		_rtld_error("%s: invalid file format", path);
354 		goto error;
355 	}
356 	if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
357 	    hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
358 		_rtld_error("%s: unsupported file layout", path);
359 		goto error;
360 	}
361 	if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
362 	    hdr->e_version != EV_CURRENT) {
363 		_rtld_error("%s: unsupported file version", path);
364 		goto error;
365 	}
366 	if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
367 		_rtld_error("%s: unsupported file type", path);
368 		goto error;
369 	}
370 	if (hdr->e_machine != ELF_TARG_MACH) {
371 		_rtld_error("%s: unsupported machine", path);
372 		goto error;
373 	}
374 
375 	/*
376 	 * We rely on the program header being in the first page.  This is
377 	 * not strictly required by the ABI specification, but it seems to
378 	 * always true in practice.  And, it simplifies things considerably.
379 	 */
380 	if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
381 		_rtld_error(
382 	    "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
383 		goto error;
384 	}
385 	if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) >
386 	    (size_t)PAGE_SIZE) {
387 		_rtld_error("%s: program header too large", path);
388 		goto error;
389 	}
390 	return (hdr);
391 
392 error:
393 	munmap(hdr, PAGE_SIZE);
394 	return (NULL);
395 }
396 
397 void
398 obj_free(Obj_Entry *obj)
399 {
400     Objlist_Entry *elm;
401 
402     if (obj->tls_done)
403 	free_tls_offset(obj);
404     while (obj->needed != NULL) {
405 	Needed_Entry *needed = obj->needed;
406 	obj->needed = needed->next;
407 	free(needed);
408     }
409     while (!STAILQ_EMPTY(&obj->names)) {
410 	Name_Entry *entry = STAILQ_FIRST(&obj->names);
411 	STAILQ_REMOVE_HEAD(&obj->names, link);
412 	free(entry);
413     }
414     while (!STAILQ_EMPTY(&obj->dldags)) {
415 	elm = STAILQ_FIRST(&obj->dldags);
416 	STAILQ_REMOVE_HEAD(&obj->dldags, link);
417 	free(elm);
418     }
419     while (!STAILQ_EMPTY(&obj->dagmembers)) {
420 	elm = STAILQ_FIRST(&obj->dagmembers);
421 	STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
422 	free(elm);
423     }
424     if (obj->vertab)
425 	free(obj->vertab);
426     if (obj->origin_path)
427 	free(obj->origin_path);
428     if (obj->z_origin)
429 	free(__DECONST(void*, obj->rpath));
430     if (obj->priv)
431 	free(obj->priv);
432     if (obj->path)
433 	free(obj->path);
434     if (obj->phdr_alloc)
435 	free(__DECONST(void *, obj->phdr));
436     free(obj);
437 }
438 
439 Obj_Entry *
440 obj_new(void)
441 {
442     Obj_Entry *obj;
443 
444     obj = CNEW(Obj_Entry);
445     STAILQ_INIT(&obj->dldags);
446     STAILQ_INIT(&obj->dagmembers);
447     STAILQ_INIT(&obj->names);
448     return obj;
449 }
450 
451 /*
452  * Given a set of ELF protection flags, return the corresponding protection
453  * flags for MMAP.
454  */
455 int
456 convert_prot(int elfflags)
457 {
458     int prot = 0;
459     if (elfflags & PF_R)
460 	prot |= PROT_READ;
461     if (elfflags & PF_W)
462 	prot |= PROT_WRITE;
463     if (elfflags & PF_X)
464 	prot |= PROT_EXEC;
465     return prot;
466 }
467 
468 static int
469 convert_flags(int elfflags)
470 {
471     int flags = MAP_PRIVATE; /* All mappings are private */
472 
473     /*
474      * Readonly mappings are marked "MAP_NOCORE", because they can be
475      * reconstructed by a debugger.
476      */
477     if (!(elfflags & PF_W))
478 	flags |= MAP_NOCORE;
479     return flags;
480 }
481