1 /* $OpenBSD: rtld_machine.c,v 1.4 2023/01/29 20:30:21 gnezdo Exp $ */
2
3 /*
4 * Copyright (c) 2004,2021 Dale Rahn <drahn@openbsd.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
16 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
19 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 */
28
29 #define _DYN_LOADER
30
31 #include <sys/types.h>
32 #include <sys/exec_elf.h>
33 #include <sys/syscall.h>
34 #include <sys/unistd.h>
35
36 #include <machine/reloc.h>
37
38 #include "util.h"
39 #include "resolve.h"
40
41 int64_t pcookie __attribute__((section(".openbsd.randomdata"))) __dso_hidden;
42 #define R_TYPE(x) R_RISCV_ ## x
43
44 void _dl_bind_start(void); /* XXX */
45 Elf_Addr _dl_bind(elf_object_t *object, int index);
46 #define _RF_S 0x80000000 /* Resolve symbol */
47 #define _RF_A 0x40000000 /* Use addend */
48 #define _RF_P 0x20000000 /* Location relative */
49 #define _RF_G 0x10000000 /* GOT offset */
50 #define _RF_B 0x08000000 /* Load address relative */
51 #define _RF_V 0x02000000 /* ERROR */
52 #define _RF_SZ(s) (((s) & 0xff) << 8) /* memory target size */
53 #define _RF_RS(s) ((s) & 0xff) /* right shift */
54 static const int reloc_target_flags[] = {
55 [ R_TYPE(NONE) ] = 0,
56 [ R_TYPE(32) ] =
57 _RF_V|_RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* GLOB_DAT */
58 [ R_TYPE(64) ] =
59 _RF_V|_RF_S|_RF_A| _RF_SZ(64) | _RF_RS(0), /* GLOB_DAT */
60 [ R_TYPE(JUMP_SLOT) ] =
61 _RF_V|_RF_S| _RF_SZ(64) | _RF_RS(0), /* JUMP_SLOT */
62 [ R_TYPE(RELATIVE) ] =
63 _RF_V|_RF_B|_RF_A| _RF_SZ(64) | _RF_RS(0), /* REL64 */
64 // [ R_TYPE(TLSDESC) ] = _RF_V|_RF_S,
65 [ R_TYPE(TLS_TPREL64) ] = _RF_V|_RF_S,
66 [ R_TYPE(COPY) ] =
67 _RF_V|_RF_S| _RF_SZ(32) | _RF_RS(0), /* 20 COPY */
68
69 };
70
71 #define RELOC_RESOLVE_SYMBOL(t) ((reloc_target_flags[t] & _RF_S) != 0)
72 #define RELOC_PC_RELATIVE(t) ((reloc_target_flags[t] & _RF_P) != 0)
73 #define RELOC_BASE_RELATIVE(t) ((reloc_target_flags[t] & _RF_B) != 0)
74 #define RELOC_USE_ADDEND(t) ((reloc_target_flags[t] & _RF_A) != 0)
75 #define RELOC_TARGET_SIZE(t) ((reloc_target_flags[t] >> 8) & 0xff)
76 #define RELOC_VALUE_RIGHTSHIFT(t) (reloc_target_flags[t] & 0xff)
77
78 static const Elf_Addr reloc_target_bitmask[] = {
79 #define _BM(x) (~(Elf_Addr)0 >> ((8*sizeof(reloc_target_bitmask[0])) - (x)))
80 [ R_TYPE(NONE) ] = 0,
81 [ R_TYPE(32) ] = _BM(32),
82 [ R_TYPE(64) ] = _BM(64),
83 [ R_TYPE(JUMP_SLOT) ] = _BM(64),
84 [ R_TYPE(RELATIVE) ] = _BM(64),
85 // [ R_TYPE(TLSDESC) ] = _BM(64),
86 [ R_TYPE(TLS_TPREL64) ] = _BM(64),
87 [ R_TYPE(COPY) ] = _BM(64),
88 #undef _BM
89 };
90 #define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t])
91
92
93 void _dl_reloc_plt(Elf_Word *where, Elf_Addr value, Elf_RelA *rel);
94
95 int
_dl_md_reloc(elf_object_t * object,int rel,int relsz)96 _dl_md_reloc(elf_object_t *object, int rel, int relsz)
97 {
98 long i;
99 long numrel;
100 long relrel;
101 int fails = 0;
102 Elf_Addr loff;
103 Elf_Addr prev_value = 0;
104 const Elf_Sym *prev_sym = NULL;
105 Elf_RelA *rels;
106
107 loff = object->obj_base;
108 numrel = object->Dyn.info[relsz] / sizeof(Elf_RelA);
109 relrel = rel == DT_RELA ? object->relcount : 0;
110 rels = (Elf_RelA *)(object->Dyn.info[rel]);
111
112 if (rels == NULL)
113 return 0;
114
115 if (relrel > numrel)
116 _dl_die("relcount > numrel: %ld > %ld", relrel, numrel);
117
118 /* tight loop for leading RELATIVE relocs */
119 for (i = 0; i < relrel; i++, rels++) {
120 Elf_Addr *where;
121
122 where = (Elf_Addr *)(rels->r_offset + loff);
123 *where += loff;
124 }
125 for (; i < numrel; i++, rels++) {
126 Elf_Addr *where, value, mask;
127 Elf_Word type;
128 const Elf_Sym *sym;
129 const char *symn;
130
131 type = ELF_R_TYPE(rels->r_info);
132
133 if (type >= nitems(reloc_target_flags) ||
134 (reloc_target_flags[type] & _RF_V) == 0)
135 _dl_die("bad relocation %ld %d", i, type);
136
137 if (type == R_TYPE(NONE))
138 continue;
139
140 if (type == R_TYPE(JUMP_SLOT) && rel != DT_JMPREL)
141 continue;
142
143 where = (Elf_Addr *)(rels->r_offset + loff);
144
145 if (RELOC_USE_ADDEND(type))
146 value = rels->r_addend;
147 else
148 value = 0;
149
150 sym = NULL;
151 symn = NULL;
152 if (RELOC_RESOLVE_SYMBOL(type)) {
153 sym = object->dyn.symtab;
154 sym += ELF_R_SYM(rels->r_info);
155 symn = object->dyn.strtab + sym->st_name;
156
157 if (sym->st_shndx != SHN_UNDEF &&
158 ELF_ST_BIND(sym->st_info) == STB_LOCAL) {
159 value += loff;
160 } else if (sym == prev_sym) {
161 value += prev_value;
162 } else {
163 struct sym_res sr;
164
165 sr = _dl_find_symbol(symn,
166 SYM_SEARCH_ALL|SYM_WARNNOTFOUND|
167 ((type == R_TYPE(JUMP_SLOT)) ?
168 SYM_PLT : SYM_NOTPLT), sym, object);
169 if (sr.sym == NULL) {
170 resolve_failed:
171 if (ELF_ST_BIND(sym->st_info) !=
172 STB_WEAK)
173 fails++;
174 continue;
175 }
176 prev_sym = sym;
177 prev_value = (Elf_Addr)(sr.obj->obj_base +
178 sr.sym->st_value);
179 value += prev_value;
180 }
181 }
182
183 if (type == R_TYPE(JUMP_SLOT)) {
184 /*
185 _dl_reloc_plt((Elf_Word *)where, value, rels);
186 */
187 *where = value;
188 continue;
189 }
190
191 if (type == R_TYPE(COPY)) {
192 void *dstaddr = where;
193 const void *srcaddr;
194 const Elf_Sym *dstsym = sym;
195 struct sym_res sr;
196
197 sr = _dl_find_symbol(symn,
198 SYM_SEARCH_OTHER|SYM_WARNNOTFOUND|SYM_NOTPLT,
199 dstsym, object);
200 if (sr.sym == NULL)
201 goto resolve_failed;
202
203 srcaddr = (void *)(sr.obj->obj_base + sr.sym->st_value);
204 _dl_bcopy(srcaddr, dstaddr, dstsym->st_size);
205 continue;
206 }
207
208 if (RELOC_PC_RELATIVE(type))
209 value -= (Elf_Addr)where;
210 if (RELOC_BASE_RELATIVE(type))
211 value += loff;
212
213 mask = RELOC_VALUE_BITMASK(type);
214 value >>= RELOC_VALUE_RIGHTSHIFT(type);
215 value &= mask;
216
217 *where &= ~mask;
218 *where |= value;
219 }
220
221 return fails;
222 }
223
224 /*
225 * Relocate the Global Offset Table (GOT).
226 * This is done by calling _dl_md_reloc on DT_JMPREL for DL_BIND_NOW,
227 * otherwise the lazy binding plt initialization is performed.
228 */
229 int
_dl_md_reloc_got(elf_object_t * object,int lazy)230 _dl_md_reloc_got(elf_object_t *object, int lazy)
231 {
232 int fails = 0;
233 Elf_Addr *pltgot = (Elf_Addr *)object->Dyn.info[DT_PLTGOT];
234 int i, num;
235 Elf_RelA *rel;
236
237 if (object->Dyn.info[DT_PLTREL] != DT_RELA)
238 return 0;
239
240 if (!lazy) {
241 fails = _dl_md_reloc(object, DT_JMPREL, DT_PLTRELSZ);
242 } else {
243 rel = (Elf_RelA *)(object->Dyn.info[DT_JMPREL]);
244 num = (object->Dyn.info[DT_PLTRELSZ]);
245
246 for (i = 0; i < num/sizeof(Elf_RelA); i++, rel++) {
247 Elf_Addr *where;
248 where = (Elf_Addr *)(rel->r_offset + object->obj_base);
249 *where += object->obj_base;
250 }
251
252 pltgot[0] = (Elf_Addr)_dl_bind_start;
253 pltgot[1] = (Elf_Addr)object;
254 }
255
256 return fails;
257 }
258
259 Elf_Addr
_dl_bind(elf_object_t * object,int relidx)260 _dl_bind(elf_object_t *object, int relidx)
261 {
262 Elf_RelA *rel;
263 const Elf_Sym *sym;
264 const char *symn;
265 struct sym_res sr;
266 int64_t cookie = pcookie;
267 struct {
268 struct __kbind param;
269 Elf_Addr newval;
270 } buf;
271
272 rel = ((Elf_RelA *)object->Dyn.info[DT_JMPREL]) + (relidx);
273
274 sym = object->dyn.symtab;
275 sym += ELF_R_SYM(rel->r_info);
276 symn = object->dyn.strtab + sym->st_name;
277
278 sr = _dl_find_symbol(symn, SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT,
279 sym, object);
280 if (sr.sym == NULL)
281 _dl_die("lazy binding failed!");
282
283 buf.newval = sr.obj->obj_base + sr.sym->st_value;
284
285 if (sr.obj->traced && _dl_trace_plt(sr.obj, symn))
286 return buf.newval;
287
288 buf.param.kb_addr = (Elf_Word *)(object->obj_base + rel->r_offset);
289 buf.param.kb_size = sizeof(Elf_Addr);
290
291 /* directly code the syscall, so that it's actually inline here */
292 {
293 register long syscall_num __asm("t0") = SYS_kbind;
294 register void *arg1 __asm("a0") = &buf;
295 register long arg2 __asm("a1") = sizeof(buf);
296 register long arg3 __asm("a2") = cookie;
297
298 __asm volatile("ecall" : "+r" (arg1), "+r" (arg2)
299 : "r" (syscall_num), "r" (arg3)
300 : "cc", "memory");
301 }
302
303 return buf.newval;
304 }
305