1 /* $NetBSD: mdreloc.c,v 1.36 2023/06/04 01:24:58 joerg Exp $ */
2
3 #include <sys/cdefs.h>
4 #ifndef lint
5 __RCSID("$NetBSD: mdreloc.c,v 1.36 2023/06/04 01:24:58 joerg Exp $");
6 #endif /* not lint */
7
8 #include <sys/types.h>
9 #include <sys/tls.h>
10
11 #include "debug.h"
12 #include "rtld.h"
13
14 void _rtld_bind_start(void);
15 void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
16 caddr_t _rtld_bind(const Obj_Entry *, Elf_Word);
17 static inline int _rtld_relocate_plt_object(const Obj_Entry *,
18 const Elf_Rela *, Elf_Addr *);
19
20 void
_rtld_setup_pltgot(const Obj_Entry * obj)21 _rtld_setup_pltgot(const Obj_Entry *obj)
22 {
23 obj->pltgot[1] = (Elf_Addr) obj;
24 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
25 }
26
27 void
_rtld_relocate_nonplt_self(Elf_Dyn * dynp,Elf_Addr relocbase)28 _rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
29 {
30 const Elf_Rela *rela = 0, *relalim;
31 Elf_Addr relasz = 0;
32 Elf_Addr *where;
33
34 for (; dynp->d_tag != DT_NULL; dynp++) {
35 switch (dynp->d_tag) {
36 case DT_RELA:
37 rela = (const Elf_Rela *)(relocbase + dynp->d_un.d_ptr);
38 break;
39 case DT_RELASZ:
40 relasz = dynp->d_un.d_val;
41 break;
42 }
43 }
44 relalim = (const Elf_Rela *)((const uint8_t *)rela + relasz);
45 for (; rela < relalim; rela++) {
46 where = (Elf_Addr *)(relocbase + rela->r_offset);
47 *where = (Elf_Addr)(relocbase + rela->r_addend);
48 }
49 }
50
51 int
_rtld_relocate_nonplt_objects(Obj_Entry * obj)52 _rtld_relocate_nonplt_objects(Obj_Entry *obj)
53 {
54 const Elf_Rela *rela;
55 const Elf_Sym *def = NULL;
56 const Obj_Entry *defobj = NULL;
57 unsigned long last_symnum = ULONG_MAX;
58
59 for (rela = obj->rela; rela < obj->relalim; rela++) {
60 Elf_Addr *where;
61 Elf_Addr tmp;
62 unsigned long symnum;
63
64 where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
65
66 switch (ELF_R_TYPE(rela->r_info)) {
67 case R_TYPE(GOT32):
68 case R_TYPE(REL32):
69 case R_TYPE(DIR32):
70 case R_TYPE(GLOB_DAT):
71 case R_TYPE(TLS_DTPOFF32):
72 case R_TYPE(TLS_DTPMOD32):
73 case R_TYPE(TLS_TPOFF32):
74 symnum = ELF_R_SYM(rela->r_info);
75 if (last_symnum != symnum) {
76 last_symnum = symnum;
77 def = _rtld_find_symdef(symnum, obj, &defobj,
78 false);
79 if (def == NULL)
80 return -1;
81 }
82 break;
83 default:
84 break;
85 }
86
87 switch (ELF_R_TYPE(rela->r_info)) {
88 case R_TYPE(NONE):
89 break;
90
91 #if 1 /* XXX should not occur */
92 case R_TYPE(GOT32):
93 tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
94 rela->r_addend);
95 if (*where != tmp)
96 *where = tmp;
97 rdbg(("GOT32 %s in %s --> %p in %s",
98 obj->strtab + obj->symtab[symnum].st_name,
99 obj->path, (void *)*where, defobj->path));
100 break;
101
102 case R_TYPE(REL32):
103 tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
104 rela->r_addend) - (Elf_Addr)where;
105 if (*where != tmp)
106 *where = tmp;
107 rdbg(("PC32 %s in %s --> %p in %s",
108 obj->strtab + obj->symtab[symnum].st_name,
109 obj->path, (void *)*where, defobj->path));
110 break;
111 #endif
112
113 case R_TYPE(DIR32):
114 tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
115 rela->r_addend);
116 if (*where != tmp)
117 *where = tmp;
118 rdbg(("32 %s in %s --> %p in %s",
119 obj->strtab + obj->symtab[symnum].st_name,
120 obj->path, (void *)*where, defobj->path));
121 break;
122
123 case R_TYPE(GLOB_DAT):
124 tmp = (Elf_Addr)(defobj->relocbase + def->st_value) +
125 rela->r_addend;
126 if (*where != tmp)
127 *where = tmp;
128 rdbg(("GLOB_DAT %s in %s --> %p in %s",
129 obj->strtab + obj->symtab[symnum].st_name,
130 obj->path, (void *)*where, defobj->path));
131 break;
132
133 case R_TYPE(RELATIVE):
134 if (rela->r_addend)
135 *where = (Elf_Addr)obj->relocbase + rela->r_addend;
136 else
137 *where += (Elf_Addr)obj->relocbase;
138 rdbg(("RELATIVE in %s --> %p", obj->path,
139 (void *)*where));
140 break;
141
142 case R_TYPE(COPY):
143 /*
144 * These are deferred until all other relocations have
145 * been done. All we do here is make sure that the
146 * COPY relocation is not in a shared library. They
147 * are allowed only in executable files.
148 */
149 if (obj->isdynamic) {
150 _rtld_error(
151 "%s: Unexpected R_COPY relocation in shared library",
152 obj->path);
153 return -1;
154 }
155 rdbg(("COPY (avoid in main)"));
156 break;
157
158 case R_TYPE(TLS_DTPOFF32):
159 *where = (Elf_Addr)(def->st_value);
160
161 rdbg(("TLS_DTPOFF32 %s in %s --> %p",
162 obj->strtab + obj->symtab[symnum].st_name,
163 obj->path, (void *)*where));
164
165 break;
166 case R_TYPE(TLS_DTPMOD32):
167 *where = (Elf_Addr)(defobj->tlsindex);
168
169 rdbg(("TLS_DTPMOD32 %s in %s --> %p",
170 obj->strtab + obj->symtab[symnum].st_name,
171 obj->path, (void *)*where));
172
173 break;
174
175 case R_TYPE(TLS_TPOFF32):
176 if (!defobj->tls_static &&
177 _rtld_tls_offset_allocate(__UNCONST(defobj)))
178 return -1;
179
180 *where = (Elf_Addr)def->st_value +
181 rela->r_addend + defobj->tlsoffset +
182 sizeof(struct tls_tcb);
183
184 rdbg(("TLS_TPOFF32 %s in %s --> %p",
185 obj->strtab + obj->symtab[symnum].st_name,
186 obj->path, (void *)*where));
187 break;
188
189 default:
190 rdbg(("sym = %lu, type = %lu, offset = %p, "
191 "addend = %p, contents = %p, symbol = %s",
192 (u_long)ELF_R_SYM(rela->r_info),
193 (u_long)ELF_R_TYPE(rela->r_info),
194 (void *)rela->r_offset, (void *)rela->r_addend,
195 (void *)*where,
196 obj->strtab + obj->symtab[symnum].st_name));
197 _rtld_error("%s: Unsupported relocation type %ld "
198 "in non-PLT relocations",
199 obj->path, (u_long) ELF_R_TYPE(rela->r_info));
200 return -1;
201 }
202 }
203 return 0;
204 }
205
206 int
_rtld_relocate_plt_lazy(Obj_Entry * obj)207 _rtld_relocate_plt_lazy(Obj_Entry *obj)
208 {
209 const Elf_Rela *rela;
210
211 if (!obj->relocbase)
212 return 0;
213
214 for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) {
215 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
216
217 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT));
218
219 /* Just relocate the GOT slots pointing into the PLT */
220 *where += (Elf_Addr)obj->relocbase;
221 rdbg(("fixup !main in %s --> %p", obj->path, (void *)*where));
222 }
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 new_value;
232 int err;
233
234 new_value = 0; /* XXX gcc */
235
236 _rtld_shared_enter();
237 err = _rtld_relocate_plt_object(obj, rela, &new_value);
238 if (err)
239 _rtld_die();
240 _rtld_shared_exit();
241
242 return (caddr_t)new_value;
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 = obj->pltrela;
249
250 for (; rela < obj->pltrelalim; rela++)
251 if (_rtld_relocate_plt_object(obj, rela, NULL) < 0)
252 return -1;
253
254 return 0;
255 }
256
257 static inline int
_rtld_relocate_plt_object(const Obj_Entry * obj,const Elf_Rela * rela,Elf_Addr * tp)258 _rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp)
259 {
260 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
261 Elf_Addr new_value;
262 const Elf_Sym *def;
263 const Obj_Entry *defobj;
264 unsigned long info = rela->r_info;
265
266 assert(ELF_R_TYPE(info) == R_TYPE(JMP_SLOT));
267
268 def = _rtld_find_plt_symdef(ELF_R_SYM(info), obj, &defobj, tp != NULL);
269 if (__predict_false(def == NULL))
270 return -1;
271 if (__predict_false(def == &_rtld_sym_zero))
272 return 0;
273
274 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
275 if (tp == NULL)
276 return 0;
277 new_value = _rtld_resolve_ifunc(defobj, def);
278 } else {
279 new_value = (Elf_Addr)(defobj->relocbase + def->st_value);
280 }
281 rdbg(("bind now/fixup in %s --> old=%p new=%p",
282 defobj->strtab + def->st_name, (void *)*where, (void *)new_value));
283 if (*where != new_value)
284 *where = new_value;
285
286 if (tp)
287 *tp = new_value;
288
289 return 0;
290 }
291