Optimize out an unneeded bzero().
[dragonfly.git] / libexec / rtld-elf / map_object.c
CommitLineData
984263bc
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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: src/libexec/rtld-elf/map_object.c,v 1.7.2.2 2002/12/28 19:49:41 dillon Exp $
1de703da 26 * $DragonFly: src/libexec/rtld-elf/map_object.c,v 1.2 2003/06/17 04:27:08 dillon Exp $
984263bc
MD
27 */
28
29#include <sys/param.h>
30#include <sys/mman.h>
31#include <sys/stat.h>
32
33#include <errno.h>
34#include <stddef.h>
35#include <stdlib.h>
36#include <string.h>
37#include <unistd.h>
38
39#include "rtld.h"
40
41static int convert_prot(int); /* Elf flags -> mmap protection */
42static int convert_flags(int); /* Elf flags -> mmap flags */
43
44/*
45 * Map a shared object into memory. The "fd" argument is a file descriptor,
46 * which must be open on the object and positioned at its beginning.
47 * The "path" argument is a pathname that is used only for error messages.
48 *
49 * The return value is a pointer to a newly-allocated Obj_Entry structure
50 * for the shared object. Returns NULL on failure.
51 */
52Obj_Entry *
53map_object(int fd, const char *path, const struct stat *sb)
54{
55 Obj_Entry *obj;
56 union {
57 Elf_Ehdr hdr;
58 char buf[PAGE_SIZE];
59 } u;
60 int nbytes, i;
61 Elf_Phdr *phdr;
62 Elf_Phdr *phlimit;
63 Elf_Phdr **segs;
64 int nsegs;
65 Elf_Phdr *phdyn;
66 Elf_Phdr *phphdr;
67 Elf_Phdr *phinterp;
68 caddr_t mapbase;
69 size_t mapsize;
70 Elf_Off base_offset;
71 Elf_Addr base_vaddr;
72 Elf_Addr base_vlimit;
73 caddr_t base_addr;
74 Elf_Off data_offset;
75 Elf_Addr data_vaddr;
76 Elf_Addr data_vlimit;
77 caddr_t data_addr;
78 int data_prot;
79 int data_flags;
80 Elf_Addr clear_vaddr;
81 caddr_t clear_addr;
82 caddr_t clear_page;
83 size_t nclear;
84 Elf_Addr bss_vaddr;
85 Elf_Addr bss_vlimit;
86 caddr_t bss_addr;
87
88 if ((nbytes = read(fd, u.buf, PAGE_SIZE)) == -1) {
89 _rtld_error("%s: read error: %s", path, strerror(errno));
90 return NULL;
91 }
92
93 /* Make sure the file is valid */
94 if (nbytes < sizeof(Elf_Ehdr)
95 || u.hdr.e_ident[EI_MAG0] != ELFMAG0
96 || u.hdr.e_ident[EI_MAG1] != ELFMAG1
97 || u.hdr.e_ident[EI_MAG2] != ELFMAG2
98 || u.hdr.e_ident[EI_MAG3] != ELFMAG3) {
99 _rtld_error("%s: invalid file format", path);
100 return NULL;
101 }
102 if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS
103 || u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) {
104 _rtld_error("%s: unsupported file layout", path);
105 return NULL;
106 }
107 if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT
108 || u.hdr.e_version != EV_CURRENT) {
109 _rtld_error("%s: unsupported file version", path);
110 return NULL;
111 }
112 if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) {
113 _rtld_error("%s: unsupported file type", path);
114 return NULL;
115 }
116 if (u.hdr.e_machine != ELF_TARG_MACH) {
117 _rtld_error("%s: unsupported machine", path);
118 return NULL;
119 }
120
121 /*
122 * We rely on the program header being in the first page. This is
123 * not strictly required by the ABI specification, but it seems to
124 * always true in practice. And, it simplifies things considerably.
125 */
126 if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) {
127 _rtld_error(
128 "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
129 return NULL;
130 }
131 if (u.hdr.e_phoff + u.hdr.e_phnum*sizeof(Elf_Phdr) > nbytes) {
132 _rtld_error("%s: program header too large", path);
133 return NULL;
134 }
135
136 /*
137 * Scan the program header entries, and save key information.
138 *
139 * We rely on there being exactly two load segments, text and data,
140 * in that order.
141 */
142 phdr = (Elf_Phdr *) (u.buf + u.hdr.e_phoff);
143 phlimit = phdr + u.hdr.e_phnum;
144 nsegs = -1;
145 phdyn = phphdr = phinterp = NULL;
146 segs = alloca(sizeof(segs[0]) * u.hdr.e_phnum);
147 while (phdr < phlimit) {
148 switch (phdr->p_type) {
149
150 case PT_INTERP:
151 phinterp = phdr;
152 break;
153
154 case PT_LOAD:
155 segs[++nsegs] = phdr;
156 if (segs[nsegs]->p_align < PAGE_SIZE) {
157 _rtld_error("%s: PT_LOAD segment %d not page-aligned",
158 path, nsegs);
159 return NULL;
160 }
161 break;
162
163 case PT_PHDR:
164 phphdr = phdr;
165 break;
166
167 case PT_DYNAMIC:
168 phdyn = phdr;
169 break;
170 }
171
172 ++phdr;
173 }
174 if (phdyn == NULL) {
175 _rtld_error("%s: object is not dynamically-linked", path);
176 return NULL;
177 }
178
179 if (nsegs < 0) {
180 _rtld_error("%s: too few PT_LOAD segments", path);
181 return NULL;
182 }
183
184 /*
185 * Map the entire address space of the object, to stake out our
186 * contiguous region, and to establish the base address for relocation.
187 */
188 base_offset = trunc_page(segs[0]->p_offset);
189 base_vaddr = trunc_page(segs[0]->p_vaddr);
190 base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
191 mapsize = base_vlimit - base_vaddr;
192 base_addr = u.hdr.e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL;
193
194 mapbase = mmap(base_addr, mapsize, convert_prot(segs[0]->p_flags),
195 convert_flags(segs[0]->p_flags), fd, base_offset);
196 if (mapbase == (caddr_t) -1) {
197 _rtld_error("%s: mmap of entire address space failed: %s",
198 path, strerror(errno));
199 return NULL;
200 }
201 if (base_addr != NULL && mapbase != base_addr) {
202 _rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
203 path, base_addr, mapbase);
204 munmap(mapbase, mapsize);
205 return NULL;
206 }
207
208 for (i = 0; i <= nsegs; i++) {
209 /* Overlay the segment onto the proper region. */
210 data_offset = trunc_page(segs[i]->p_offset);
211 data_vaddr = trunc_page(segs[i]->p_vaddr);
212 data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz);
213 data_addr = mapbase + (data_vaddr - base_vaddr);
214 data_prot = convert_prot(segs[i]->p_flags);
215 data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
216 /* Do not call mmap on the first segment - this is redundant */
217 if (i && mmap(data_addr, data_vlimit - data_vaddr, data_prot,
218 data_flags, fd, data_offset) == (caddr_t) -1) {
219 _rtld_error("%s: mmap of data failed: %s", path, strerror(errno));
220 return NULL;
221 }
222
223 /* Clear any BSS in the last page of the segment. */
224 clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
225 clear_addr = mapbase + (clear_vaddr - base_vaddr);
226 clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr);
227 if ((nclear = data_vlimit - clear_vaddr) > 0) {
228 /* Make sure the end of the segment is writable */
229 if ((data_prot & PROT_WRITE) == 0 &&
230 -1 == mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
231 _rtld_error("%s: mprotect failed: %s", path,
232 strerror(errno));
233 return NULL;
234 }
235
236 memset(clear_addr, 0, nclear);
237
238 /* Reset the data protection back */
239 if ((data_prot & PROT_WRITE) == 0)
240 mprotect(clear_page, PAGE_SIZE, data_prot);
241 }
242
243 /* Overlay the BSS segment onto the proper region. */
244 bss_vaddr = data_vlimit;
245 bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz);
246 bss_addr = mapbase + (bss_vaddr - base_vaddr);
247 if (bss_vlimit > bss_vaddr) { /* There is something to do */
248 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot,
249 MAP_PRIVATE|MAP_FIXED|MAP_ANON, -1, 0) == (caddr_t) -1) {
250 _rtld_error("%s: mmap of bss failed: %s", path,
251 strerror(errno));
252 return NULL;
253 }
254 }
255 }
256
257 obj = obj_new();
258 if (sb != NULL) {
259 obj->dev = sb->st_dev;
260 obj->ino = sb->st_ino;
261 }
262 obj->mapbase = mapbase;
263 obj->mapsize = mapsize;
264 obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
265 base_vaddr;
266 obj->vaddrbase = base_vaddr;
267 obj->relocbase = mapbase - base_vaddr;
268 obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
269 if (u.hdr.e_entry != 0)
270 obj->entry = (caddr_t) (obj->relocbase + u.hdr.e_entry);
271 if (phphdr != NULL) {
272 obj->phdr = (const Elf_Phdr *) (obj->relocbase + phphdr->p_vaddr);
273 obj->phsize = phphdr->p_memsz;
274 }
275 if (phinterp != NULL)
276 obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr);
277
278 return obj;
279}
280
281void
282obj_free(Obj_Entry *obj)
283{
284 Objlist_Entry *elm;
285
286 free(obj->path);
287 while (obj->needed != NULL) {
288 Needed_Entry *needed = obj->needed;
289 obj->needed = needed->next;
290 free(needed);
291 }
292 while (!STAILQ_EMPTY(&obj->dldags)) {
293 elm = STAILQ_FIRST(&obj->dldags);
294 STAILQ_REMOVE_HEAD(&obj->dldags, link);
295 free(elm);
296 }
297 while (!STAILQ_EMPTY(&obj->dagmembers)) {
298 elm = STAILQ_FIRST(&obj->dagmembers);
299 STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
300 free(elm);
301 }
302 free(obj);
303}
304
305Obj_Entry *
306obj_new(void)
307{
308 Obj_Entry *obj;
309
310 obj = CNEW(Obj_Entry);
311 STAILQ_INIT(&obj->dldags);
312 STAILQ_INIT(&obj->dagmembers);
313 return obj;
314}
315
316/*
317 * Given a set of ELF protection flags, return the corresponding protection
318 * flags for MMAP.
319 */
320static int
321convert_prot(int elfflags)
322{
323 int prot = 0;
324 if (elfflags & PF_R)
325 prot |= PROT_READ;
326 if (elfflags & PF_W)
327 prot |= PROT_WRITE;
328 if (elfflags & PF_X)
329 prot |= PROT_EXEC;
330 return prot;
331}
332
333static int
334convert_flags(int elfflags)
335{
336 int flags = MAP_PRIVATE; /* All mappings are private */
337
338 /*
339 * Readonly mappings are marked "MAP_NOCORE", because they can be
340 * reconstructed by a debugger.
341 */
342 if (!(elfflags & PF_W))
343 flags |= MAP_NOCORE;
344 return flags;
345}