1 /* $NetBSD: mdreloc.c,v 1.35 2025/04/16 18:01:01 riastradh Exp $ */
2
3 /*
4 * Copyright 1996 John D. Polstra.
5 * Copyright 1996 Matt Thomas <matt@3am-software.com>
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by John Polstra.
19 * 4. The name of the author may not be used to endorse or promote products
20 * derived from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34 #include <sys/cdefs.h>
35 #ifndef lint
36 __RCSID("$NetBSD: mdreloc.c,v 1.35 2025/04/16 18:01:01 riastradh Exp $");
37 #endif /* not lint */
38
39 #include <sys/types.h>
40
41 #include "debug.h"
42 #include "rtld.h"
43
44 void _rtld_bind_start(void);
45 void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
46 caddr_t _rtld_bind(const Obj_Entry *, Elf_Word);
47 static inline int _rtld_relocate_plt_object(const Obj_Entry *,
48 const Elf_Rela *, Elf_Addr *);
49
50 void
_rtld_setup_pltgot(const Obj_Entry * obj)51 _rtld_setup_pltgot(const Obj_Entry *obj)
52 {
53 obj->pltgot[1] = (Elf_Addr) obj;
54 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
55 }
56
57 void
_rtld_relocate_nonplt_self(Elf_Dyn * dynp,Elf_Addr relocbase)58 _rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
59 {
60 const Elf_Rela *rela = 0, *relalim;
61 Elf_Addr relasz = 0;
62 Elf_Addr *where;
63
64 for (; dynp->d_tag != DT_NULL; dynp++) {
65 switch (dynp->d_tag) {
66 case DT_RELA:
67 rela = (const Elf_Rela *)(relocbase + dynp->d_un.d_ptr);
68 break;
69 case DT_RELASZ:
70 relasz = dynp->d_un.d_val;
71 break;
72 }
73 }
74 relalim = (const Elf_Rela *)((const uint8_t *)rela + relasz);
75 for (; rela < relalim; rela++) {
76 where = (Elf_Addr *)(relocbase + rela->r_offset);
77 *where = (Elf_Addr)(relocbase + rela->r_addend);
78 }
79 }
80
81 int
_rtld_relocate_nonplt_objects(Obj_Entry * obj)82 _rtld_relocate_nonplt_objects(Obj_Entry *obj)
83 {
84 const Elf_Rela *rela;
85 const Elf_Sym *def = NULL;
86 const Obj_Entry *defobj = NULL;
87 unsigned long last_symnum = ULONG_MAX;
88
89 for (rela = obj->rela; rela < obj->relalim; rela++) {
90 Elf_Addr *where;
91 Elf_Addr tmp;
92 unsigned long symnum;
93
94 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
95
96 switch (ELF_R_TYPE(rela->r_info)) {
97 case R_TYPE(32): /* word32 S + A */
98 case R_TYPE(GLOB_DAT): /* word32 S + A */
99 symnum = ELF_R_SYM(rela->r_info);
100 if (last_symnum != symnum) {
101 last_symnum = symnum;
102 def = _rtld_find_symdef(symnum, obj, &defobj,
103 false);
104 if (def == NULL)
105 return -1;
106 }
107 break;
108
109 default:
110 break;
111 }
112
113 switch (ELF_R_TYPE(rela->r_info)) {
114 case R_TYPE(NONE):
115 break;
116
117 case R_TYPE(32): /* word32 S + A */
118 case R_TYPE(GLOB_DAT): /* word32 S + A */
119 tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
120 rela->r_addend);
121
122 if (*where != tmp)
123 *where = tmp;
124 rdbg(("32/GLOB_DAT %s in %s --> %p in %s",
125 obj->strtab + obj->symtab[symnum].st_name,
126 obj->path, (void *)*where, defobj->path));
127 break;
128
129 case R_TYPE(RELATIVE): /* word32 B + A */
130 tmp = (Elf_Addr)(obj->relocbase + rela->r_addend);
131 if (*where != tmp)
132 *where = tmp;
133 rdbg(("RELATIVE in %s --> %p", obj->path,
134 (void *)*where));
135 break;
136
137 case R_TYPE(COPY):
138 /*
139 * These are deferred until all other relocations have
140 * been done. All we do here is make sure that the
141 * COPY relocation is not in a shared library. They
142 * are allowed only in executable files.
143 */
144 if (obj->isdynamic) {
145 _rtld_error(
146 "%s: Unexpected R_COPY relocation in shared library",
147 obj->path);
148 return -1;
149 }
150 rdbg(("COPY (avoid in main)"));
151 break;
152
153 default:
154 rdbg(("sym = %lu, type = %lu, offset = %p, "
155 "addend = %p, contents = %p",
156 (u_long)ELF_R_SYM(rela->r_info),
157 (u_long)ELF_R_TYPE(rela->r_info),
158 (void *)rela->r_offset, (void *)rela->r_addend,
159 (void *)*where));
160 _rtld_error("%s: Unsupported relocation type %ld "
161 "in non-PLT relocations",
162 obj->path, (u_long) ELF_R_TYPE(rela->r_info));
163 return -1;
164 }
165 }
166 return 0;
167 }
168
169 int
_rtld_relocate_plt_lazy(Obj_Entry * obj)170 _rtld_relocate_plt_lazy(Obj_Entry *obj)
171 {
172 const Elf_Rela *rela;
173
174 if (!obj->relocbase)
175 return 0;
176
177 for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) {
178 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
179
180 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT));
181
182 /* Just relocate the GOT slots pointing into the PLT */
183 *where += (Elf_Addr)obj->relocbase;
184 rdbg(("lazy fixup pltgot %p in %s --> %p", where, obj->path,
185 (void *)*where));
186 }
187
188 return 0;
189 }
190
191 static inline int
_rtld_relocate_plt_object(const Obj_Entry * obj,const Elf_Rela * rela,Elf_Addr * tp)192 _rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp)
193 {
194 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
195 Elf_Addr new_value;
196 const Elf_Sym *def;
197 const Obj_Entry *defobj;
198 unsigned long info = rela->r_info;
199
200 assert(ELF_R_TYPE(info) == R_TYPE(JMP_SLOT));
201
202 def = _rtld_find_plt_symdef(ELF_R_SYM(info), obj, &defobj, tp != NULL);
203 if (__predict_false(def == NULL))
204 return -1;
205 if (__predict_false(def == &_rtld_sym_zero))
206 return 0;
207
208 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
209 if (tp == NULL)
210 return 0;
211 new_value = _rtld_resolve_ifunc(defobj, def);
212 } else {
213 new_value = (Elf_Addr)(defobj->relocbase + def->st_value +
214 rela->r_addend);
215 }
216 rdbg(("bind now/fixup pltgot %p in %s --> old=%p new=%p", where,
217 defobj->strtab + def->st_name, (void *)*where, (void *)new_value));
218 if (*where != new_value)
219 *where = new_value;
220
221 if (tp)
222 *tp = new_value - rela->r_addend;
223
224 return 0;
225 }
226
227 caddr_t
_rtld_bind(const Obj_Entry * obj,Elf_Word reloff)228 _rtld_bind(const Obj_Entry *obj, Elf_Word reloff)
229 {
230 const Elf_Rela *rela = (const Elf_Rela *)((const uint8_t *)obj->pltrela + reloff);
231 Elf_Addr result;
232 int err;
233
234 result = 0; /* XXX gcc */
235
236 _rtld_shared_enter();
237 err = _rtld_relocate_plt_object(obj, rela, &result);
238 if (err)
239 _rtld_die();
240 _rtld_shared_exit();
241
242 return (caddr_t)result;
243 }
244
245 int
_rtld_relocate_plt_objects(const Obj_Entry * obj)246 _rtld_relocate_plt_objects(const Obj_Entry *obj)
247 {
248 const Elf_Rela *rela;
249
250 for (rela = obj->pltrela; rela < obj->pltrelalim; rela++)
251 if (_rtld_relocate_plt_object(obj, rela, NULL) < 0)
252 return -1;
253
254 return 0;
255 }
256