1/*-
2 * Copyright 1996-1998 John D. Polstra.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
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.
13 *
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.
24 *
25 * $FreeBSD$
26 */
27
28#include <sys/param.h>
29#include <sys/mman.h>
30#include <sys/stat.h>
31
32#include <errno.h>
33#include <stddef.h>
34#include <stdlib.h>
35#include <string.h>
36#include <unistd.h>
37
38#include "debug.h"
39#include "rtld.h"
40
41static Elf_Ehdr *get_elf_header(int, const char *);
42static int convert_prot(int);	/* Elf flags -> mmap protection */
43static int convert_flags(int); /* Elf flags -> mmap flags */
44
45/*
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.
49 *
50 * The return value is a pointer to a newly-allocated Obj_Entry structure
51 * for the shared object.  Returns NULL on failure.
52 */
53Obj_Entry *
54map_object(int fd, const char *path, const struct stat *sb)
55{
56    Obj_Entry *obj;
57    Elf_Ehdr *hdr;
58    int i;
59    Elf_Phdr *phdr;
60    Elf_Phdr *phlimit;
61    Elf_Phdr **segs;
62    int nsegs;
63    Elf_Phdr *phdyn;
64    Elf_Phdr *phinterp;
65    Elf_Phdr *phtls;
66    caddr_t mapbase;
67    size_t mapsize;
68    Elf_Addr base_vaddr;
69    Elf_Addr base_vlimit;
70    caddr_t base_addr;
71    Elf_Off data_offset;
72    Elf_Addr data_vaddr;
73    Elf_Addr data_vlimit;
74    caddr_t data_addr;
75    int data_prot;
76    int data_flags;
77    Elf_Addr clear_vaddr;
78    caddr_t clear_addr;
79    caddr_t clear_page;
80    Elf_Addr phdr_vaddr;
81    size_t nclear, phsize;
82    Elf_Addr bss_vaddr;
83    Elf_Addr bss_vlimit;
84    caddr_t bss_addr;
85    Elf_Word stack_flags;
86    Elf_Addr relro_page;
87    size_t relro_size;
88    Elf_Addr note_start;
89    Elf_Addr note_end;
90
91    hdr = get_elf_header(fd, path);
92    if (hdr == NULL)
93	return (NULL);
94
95    /*
96     * Scan the program header entries, and save key information.
97     *
98     * We expect that the loadable segments are ordered by load address.
99     */
100    phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff);
101    phsize  = hdr->e_phnum * sizeof (phdr[0]);
102    phlimit = phdr + hdr->e_phnum;
103    nsegs = -1;
104    phdyn = phinterp = phtls = NULL;
105    phdr_vaddr = 0;
106    relro_page = 0;
107    relro_size = 0;
108    note_start = 0;
109    note_end = 0;
110    segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
111    stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W;
112    while (phdr < phlimit) {
113	switch (phdr->p_type) {
114
115	case PT_INTERP:
116	    phinterp = phdr;
117	    break;
118
119	case PT_LOAD:
120	    segs[++nsegs] = phdr;
121    	    if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) {
122		_rtld_error("%s: PT_LOAD segment %d not page-aligned",
123		    path, nsegs);
124		goto error;
125	    }
126	    break;
127
128	case PT_PHDR:
129	    phdr_vaddr = phdr->p_vaddr;
130	    phsize = phdr->p_memsz;
131	    break;
132
133	case PT_DYNAMIC:
134	    phdyn = phdr;
135	    break;
136
137	case PT_TLS:
138	    phtls = phdr;
139	    break;
140
141	case PT_GNU_STACK:
142	    stack_flags = phdr->p_flags;
143	    break;
144
145	case PT_GNU_RELRO:
146	    relro_page = phdr->p_vaddr;
147	    relro_size = phdr->p_memsz;
148	    break;
149
150	case PT_NOTE:
151	    if (phdr->p_offset > PAGE_SIZE ||
152	      phdr->p_offset + phdr->p_filesz > PAGE_SIZE)
153		break;
154	    note_start = (Elf_Addr)(char *)hdr + phdr->p_offset;
155	    note_end = note_start + phdr->p_filesz;
156	    break;
157	}
158
159	++phdr;
160    }
161    if (phdyn == NULL) {
162	_rtld_error("%s: object is not dynamically-linked", path);
163	goto error;
164    }
165
166    if (nsegs < 0) {
167	_rtld_error("%s: too few PT_LOAD segments", path);
168	goto error;
169    }
170
171    /*
172     * Map the entire address space of the object, to stake out our
173     * contiguous region, and to establish the base address for relocation.
174     */
175    base_vaddr = trunc_page(segs[0]->p_vaddr);
176    base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
177    mapsize = base_vlimit - base_vaddr;
178    base_addr = (caddr_t) base_vaddr;
179
180    mapbase = mmap(base_addr, mapsize, PROT_NONE, MAP_ANON | MAP_PRIVATE |
181      MAP_NOCORE, -1, 0);
182    if (mapbase == (caddr_t) -1) {
183	_rtld_error("%s: mmap of entire address space failed: %s",
184	  path, rtld_strerror(errno));
185	goto error;
186    }
187    if (base_addr != NULL && mapbase != base_addr) {
188	_rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
189	  path, base_addr, mapbase);
190	goto error1;
191    }
192
193    for (i = 0; i <= nsegs; i++) {
194	/* Overlay the segment onto the proper region. */
195	data_offset = trunc_page(segs[i]->p_offset);
196	data_vaddr = trunc_page(segs[i]->p_vaddr);
197	data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz);
198	data_addr = mapbase + (data_vaddr - base_vaddr);
199	data_prot = convert_prot(segs[i]->p_flags);
200	data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
201	if (mmap(data_addr, data_vlimit - data_vaddr, data_prot,
202	  data_flags | MAP_PREFAULT_READ, fd, data_offset) == (caddr_t) -1) {
203	    _rtld_error("%s: mmap of data failed: %s", path,
204		rtld_strerror(errno));
205	    goto error1;
206	}
207
208	/* Do BSS setup */
209	if (segs[i]->p_filesz != segs[i]->p_memsz) {
210
211	    /* Clear any BSS in the last page of the segment. */
212	    clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
213	    clear_addr = mapbase + (clear_vaddr - base_vaddr);
214	    clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr);
215
216	    if ((nclear = data_vlimit - clear_vaddr) > 0) {
217		/* Make sure the end of the segment is writable */
218		if ((data_prot & PROT_WRITE) == 0 && -1 ==
219		     mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
220			_rtld_error("%s: mprotect failed: %s", path,
221			    rtld_strerror(errno));
222			goto error1;
223		}
224
225		memset(clear_addr, 0, nclear);
226
227		/* Reset the data protection back */
228		if ((data_prot & PROT_WRITE) == 0)
229		    mprotect(clear_page, PAGE_SIZE, data_prot);
230	    }
231
232	    /* Overlay the BSS segment onto the proper region. */
233	    bss_vaddr = data_vlimit;
234	    bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz);
235	    bss_addr = mapbase +  (bss_vaddr - base_vaddr);
236	    if (bss_vlimit > bss_vaddr) {	/* There is something to do */
237		if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot,
238		    data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) {
239		    _rtld_error("%s: mmap of bss failed: %s", path,
240			rtld_strerror(errno));
241		    goto error1;
242		}
243	    }
244	}
245
246	if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
247	  (data_vlimit - data_vaddr + data_offset) >=
248	  (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) {
249	    phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
250	}
251    }
252
253    obj = obj_new();
254    if (sb != NULL) {
255	obj->dev = sb->st_dev;
256	obj->ino = sb->st_ino;
257    }
258    obj->mapbase = mapbase;
259    obj->mapsize = mapsize;
260    obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
261      base_vaddr;
262    obj->vaddrbase = base_vaddr;
263    obj->relocbase = mapbase - base_vaddr;
264    obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
265    if (hdr->e_entry != 0)
266	obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry);
267    if (phdr_vaddr != 0) {
268	obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr);
269    } else {
270	obj->phdr = malloc(phsize);
271	if (obj->phdr == NULL) {
272	    obj_free(obj);
273	    _rtld_error("%s: cannot allocate program header", path);
274	    goto error1;
275	}
276	memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize);
277	obj->phdr_alloc = true;
278    }
279    obj->phsize = phsize;
280    if (phinterp != NULL)
281	obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr);
282    if (phtls != NULL) {
283	tls_dtv_generation++;
284	obj->tlsindex = ++tls_max_index;
285	obj->tlssize = phtls->p_memsz;
286	obj->tlsalign = phtls->p_align;
287	obj->tlsinitsize = phtls->p_filesz;
288	obj->tlsinit = mapbase + phtls->p_vaddr;
289    }
290    obj->stack_flags = stack_flags;
291    obj->relro_page = obj->relocbase + trunc_page(relro_page);
292    obj->relro_size = round_page(relro_size);
293    if (note_start < note_end)
294	digest_notes(obj, note_start, note_end);
295    munmap(hdr, PAGE_SIZE);
296    return (obj);
297
298error1:
299    munmap(mapbase, mapsize);
300error:
301    munmap(hdr, PAGE_SIZE);
302    return (NULL);
303}
304
305static Elf_Ehdr *
306get_elf_header(int fd, const char *path)
307{
308	Elf_Ehdr *hdr;
309
310	hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_PREFAULT_READ,
311	    fd, 0);
312	if (hdr == (Elf_Ehdr *)MAP_FAILED) {
313		_rtld_error("%s: read error: %s", path, rtld_strerror(errno));
314		return (NULL);
315	}
316
317	/* Make sure the file is valid */
318	if (!IS_ELF(*hdr)) {
319		_rtld_error("%s: invalid file format", path);
320		goto error;
321	}
322	if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
323	    hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
324		_rtld_error("%s: unsupported file layout", path);
325		goto error;
326	}
327	if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
328	    hdr->e_version != EV_CURRENT) {
329		_rtld_error("%s: unsupported file version", path);
330		goto error;
331	}
332	if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
333		_rtld_error("%s: unsupported file type", path);
334		goto error;
335	}
336	if (hdr->e_machine != ELF_TARG_MACH) {
337		_rtld_error("%s: unsupported machine", path);
338		goto error;
339	}
340
341	/*
342	 * We rely on the program header being in the first page.  This is
343	 * not strictly required by the ABI specification, but it seems to
344	 * always true in practice.  And, it simplifies things considerably.
345	 */
346	if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
347		_rtld_error(
348	    "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
349		goto error;
350	}
351	if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) >
352	    (size_t)PAGE_SIZE) {
353		_rtld_error("%s: program header too large", path);
354		goto error;
355	}
356	return (hdr);
357
358error:
359	munmap(hdr, PAGE_SIZE);
360	return (NULL);
361}
362
363void
364obj_free(Obj_Entry *obj)
365{
366    Objlist_Entry *elm;
367
368    if (obj->tls_done)
369	free_tls_offset(obj);
370    while (obj->needed != NULL) {
371	Needed_Entry *needed = obj->needed;
372	obj->needed = needed->next;
373	free(needed);
374    }
375    while (!STAILQ_EMPTY(&obj->names)) {
376	Name_Entry *entry = STAILQ_FIRST(&obj->names);
377	STAILQ_REMOVE_HEAD(&obj->names, link);
378	free(entry);
379    }
380    while (!STAILQ_EMPTY(&obj->dldags)) {
381	elm = STAILQ_FIRST(&obj->dldags);
382	STAILQ_REMOVE_HEAD(&obj->dldags, link);
383	free(elm);
384    }
385    while (!STAILQ_EMPTY(&obj->dagmembers)) {
386	elm = STAILQ_FIRST(&obj->dagmembers);
387	STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
388	free(elm);
389    }
390    if (obj->vertab)
391	free(obj->vertab);
392    if (obj->origin_path)
393	free(obj->origin_path);
394    if (obj->z_origin)
395	free(obj->rpath);
396    if (obj->priv)
397	free(obj->priv);
398    if (obj->path)
399	free(obj->path);
400    if (obj->phdr_alloc)
401	free((void *)obj->phdr);
402    free(obj);
403}
404
405Obj_Entry *
406obj_new(void)
407{
408    Obj_Entry *obj;
409
410    obj = CNEW(Obj_Entry);
411    STAILQ_INIT(&obj->dldags);
412    STAILQ_INIT(&obj->dagmembers);
413    STAILQ_INIT(&obj->names);
414    return obj;
415}
416
417/*
418 * Given a set of ELF protection flags, return the corresponding protection
419 * flags for MMAP.
420 */
421static int
422convert_prot(int elfflags)
423{
424    int prot = 0;
425    if (elfflags & PF_R)
426	prot |= PROT_READ;
427    if (elfflags & PF_W)
428	prot |= PROT_WRITE;
429    if (elfflags & PF_X)
430	prot |= PROT_EXEC;
431    return prot;
432}
433
434static int
435convert_flags(int elfflags)
436{
437    int flags = MAP_PRIVATE; /* All mappings are private */
438
439    /*
440     * Readonly mappings are marked "MAP_NOCORE", because they can be
441     * reconstructed by a debugger.
442     */
443    if (!(elfflags & PF_W))
444	flags |= MAP_NOCORE;
445    return flags;
446}
447