reloc.c revision 112242 
1/*-
2 * Copyright 1996, 1997, 1998, 1999 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: head/libexec/rtld-elf/i386/reloc.c 112242 2003-03-14 21:10:13Z kan $
26 */
27
28/*
29 * Dynamic linker for ELF.
30 *
31 * John Polstra <jdp@polstra.com>.
32 */
33
34#include <sys/param.h>
35#include <sys/mman.h>
36
37#include <dlfcn.h>
38#include <err.h>
39#include <errno.h>
40#include <fcntl.h>
41#include <stdarg.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include <string.h>
45#include <unistd.h>
46
47#include "debug.h"
48#include "rtld.h"
49
50/*
51 * Process the special R_386_COPY relocations in the main program.  These
52 * copy data from a shared object into a region in the main program's BSS
53 * segment.
54 *
55 * Returns 0 on success, -1 on failure.
56 */
57int
58do_copy_relocations(Obj_Entry *dstobj)
59{
60    const Elf_Rel *rellim;
61    const Elf_Rel *rel;
62
63    assert(dstobj->mainprog);	/* COPY relocations are invalid elsewhere */
64
65    rellim = (const Elf_Rel *) ((caddr_t) dstobj->rel + dstobj->relsize);
66    for (rel = dstobj->rel;  rel < rellim;  rel++) {
67	if (ELF_R_TYPE(rel->r_info) == R_386_COPY) {
68	    void *dstaddr;
69	    const Elf_Sym *dstsym;
70	    const char *name;
71	    unsigned long hash;
72	    size_t size;
73	    const void *srcaddr;
74	    const Elf_Sym *srcsym;
75	    Obj_Entry *srcobj;
76
77	    dstaddr = (void *) (dstobj->relocbase + rel->r_offset);
78	    dstsym = dstobj->symtab + ELF_R_SYM(rel->r_info);
79	    name = dstobj->strtab + dstsym->st_name;
80	    hash = elf_hash(name);
81	    size = dstsym->st_size;
82
83	    for (srcobj = dstobj->next;  srcobj != NULL;  srcobj = srcobj->next)
84		if ((srcsym = symlook_obj(name, hash, srcobj, false)) != NULL)
85		    break;
86
87	    if (srcobj == NULL) {
88		_rtld_error("Undefined symbol \"%s\" referenced from COPY"
89		  " relocation in %s", name, dstobj->path);
90		return -1;
91	    }
92
93	    srcaddr = (const void *) (srcobj->relocbase + srcsym->st_value);
94	    memcpy(dstaddr, srcaddr, size);
95	}
96    }
97
98    return 0;
99}
100
101/* Initialize the special GOT entries. */
102void
103init_pltgot(Obj_Entry *obj)
104{
105    if (obj->pltgot != NULL) {
106	obj->pltgot[1] = (Elf_Addr) obj;
107	obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
108    }
109}
110
111/* Process the non-PLT relocations. */
112int
113reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld)
114{
115	const Elf_Rel *rellim;
116	const Elf_Rel *rel;
117	SymCache *cache;
118	int bytes = obj->nchains * sizeof(SymCache);
119	int r = -1;
120
121	/*
122	 * The dynamic loader may be called from a thread, we have
123	 * limited amounts of stack available so we cannot use alloca().
124	 */
125	cache = mmap(NULL, bytes, PROT_READ|PROT_WRITE, MAP_ANON, -1, 0);
126	if (cache == MAP_FAILED)
127	    cache = NULL;
128
129	rellim = (const Elf_Rel *) ((caddr_t) obj->rel + obj->relsize);
130	for (rel = obj->rel;  rel < rellim;  rel++) {
131	    Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rel->r_offset);
132
133	    switch (ELF_R_TYPE(rel->r_info)) {
134
135	    case R_386_NONE:
136		break;
137
138	    case R_386_32:
139		{
140		    const Elf_Sym *def;
141		    const Obj_Entry *defobj;
142
143		    def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
144		      false, cache);
145		    if (def == NULL)
146			goto done;
147
148		    *where += (Elf_Addr) (defobj->relocbase + def->st_value);
149		}
150		break;
151
152	    case R_386_PC32:
153		/*
154		 * I don't think the dynamic linker should ever see this
155		 * type of relocation.  But the binutils-2.6 tools sometimes
156		 * generate it.
157		 */
158		{
159		    const Elf_Sym *def;
160		    const Obj_Entry *defobj;
161
162		    def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
163		      false, cache);
164		    if (def == NULL)
165			goto done;
166
167		    *where +=
168		      (Elf_Addr) (defobj->relocbase + def->st_value) -
169		      (Elf_Addr) where;
170		}
171		break;
172
173	    case R_386_COPY:
174		/*
175		 * These are deferred until all other relocations have
176		 * been done.  All we do here is make sure that the COPY
177		 * relocation is not in a shared library.  They are allowed
178		 * only in executable files.
179		 */
180		if (!obj->mainprog) {
181		    _rtld_error("%s: Unexpected R_386_COPY relocation"
182		      " in shared library", obj->path);
183		    goto done;
184		}
185		break;
186
187	    case R_386_GLOB_DAT:
188		{
189		    const Elf_Sym *def;
190		    const Obj_Entry *defobj;
191
192		    def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
193		      false, cache);
194		    if (def == NULL)
195			goto done;
196
197		    *where = (Elf_Addr) (defobj->relocbase + def->st_value);
198		}
199		break;
200
201	    case R_386_RELATIVE:
202		*where += (Elf_Addr) obj->relocbase;
203		break;
204
205	    default:
206		_rtld_error("%s: Unsupported relocation type %d"
207		  " in non-PLT relocations\n", obj->path,
208		  ELF_R_TYPE(rel->r_info));
209		goto done;
210	    }
211	}
212	r = 0;
213done:
214	if (cache)
215	    munmap(cache, bytes);
216	return(r);
217}
218
219/* Process the PLT relocations. */
220int
221reloc_plt(Obj_Entry *obj)
222{
223    const Elf_Rel *rellim;
224    const Elf_Rel *rel;
225
226    rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize);
227    for (rel = obj->pltrel;  rel < rellim;  rel++) {
228	Elf_Addr *where;
229
230	assert(ELF_R_TYPE(rel->r_info) == R_386_JMP_SLOT);
231
232	/* Relocate the GOT slot pointing into the PLT. */
233	where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
234	*where += (Elf_Addr)obj->relocbase;
235    }
236    return 0;
237}
238
239/* Relocate the jump slots in an object. */
240int
241reloc_jmpslots(Obj_Entry *obj)
242{
243    const Elf_Rel *rellim;
244    const Elf_Rel *rel;
245
246    if (obj->jmpslots_done)
247	return 0;
248    rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize);
249    for (rel = obj->pltrel;  rel < rellim;  rel++) {
250	Elf_Addr *where, target;
251	const Elf_Sym *def;
252	const Obj_Entry *defobj;
253
254	assert(ELF_R_TYPE(rel->r_info) == R_386_JMP_SLOT);
255	where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
256	def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL);
257	if (def == NULL)
258	    return -1;
259	target = (Elf_Addr)(defobj->relocbase + def->st_value);
260	reloc_jmpslot(where, target, defobj, obj, rel);
261    }
262    obj->jmpslots_done = true;
263    return 0;
264}
265