1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 *
4 * Copyright (C) 2001 Rusty Russell.
5 * Copyright (C) 2003, 2004 Ralf Baechle (ralf@linux-mips.org)
6 * Copyright (C) 2005 Thiemo Seufer
7 */
8
9 #undef DEBUG
10
11 #include <linux/extable.h>
12 #include <linux/moduleloader.h>
13 #include <linux/elf.h>
14 #include <linux/mm.h>
15 #include <linux/numa.h>
16 #include <linux/slab.h>
17 #include <linux/fs.h>
18 #include <linux/string.h>
19 #include <linux/kernel.h>
20 #include <linux/spinlock.h>
21 #include <linux/jump_label.h>
22 #include <asm/jump_label.h>
23
24 struct mips_hi16 {
25 struct mips_hi16 *next;
26 Elf_Addr *addr;
27 Elf_Addr value;
28 };
29
30 static LIST_HEAD(dbe_list);
31 static DEFINE_SPINLOCK(dbe_lock);
32
33 static void apply_r_mips_32(u32 *location, u32 base, Elf_Addr v)
34 {
35 *location = base + v;
36 }
37
38 static int apply_r_mips_26(struct module *me, u32 *location, u32 base,
39 Elf_Addr v)
40 {
41 if (v % 4) {
42 pr_err("module %s: dangerous R_MIPS_26 relocation\n",
43 me->name);
44 return -ENOEXEC;
45 }
46
47 if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
48 pr_err("module %s: relocation overflow\n",
49 me->name);
50 return -ENOEXEC;
51 }
52
53 *location = (*location & ~0x03ffffff) |
54 ((base + (v >> 2)) & 0x03ffffff);
55
56 return 0;
57 }
58
59 static int apply_r_mips_hi16(struct module *me, u32 *location, Elf_Addr v,
60 bool rela)
61 {
62 struct mips_hi16 *n;
63
64 if (rela) {
65 *location = (*location & 0xffff0000) |
66 ((((long long) v + 0x8000LL) >> 16) & 0xffff);
67 return 0;
68 }
69
70 /*
71 * We cannot relocate this one now because we don't know the value of
72 * the carry we need to add. Save the information, and let LO16 do the
73 * actual relocation.
74 */
75 n = kmalloc(sizeof *n, GFP_KERNEL);
76 if (!n)
77 return -ENOMEM;
78
79 n->addr = (Elf_Addr *)location;
80 n->value = v;
81 n->next = me->arch.r_mips_hi16_list;
82 me->arch.r_mips_hi16_list = n;
83
84 return 0;
85 }
86
87 static void free_relocation_chain(struct mips_hi16 *l)
88 {
89 struct mips_hi16 *next;
90
91 while (l) {
92 next = l->next;
93 kfree(l);
94 l = next;
95 }
96 }
97
98 static int apply_r_mips_lo16(struct module *me, u32 *location,
99 u32 base, Elf_Addr v, bool rela)
100 {
101 unsigned long insnlo = base;
102 struct mips_hi16 *l;
103 Elf_Addr val, vallo;
104
105 if (rela) {
106 *location = (*location & 0xffff0000) | (v & 0xffff);
107 return 0;
108 }
109
110 /* Sign extend the addend we extract from the lo insn. */
111 vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;
112
113 if (me->arch.r_mips_hi16_list != NULL) {
114 l = me->arch.r_mips_hi16_list;
115 while (l != NULL) {
116 struct mips_hi16 *next;
117 unsigned long insn;
118
119 /*
120 * The value for the HI16 had best be the same.
121 */
122 if (v != l->value)
123 goto out_danger;
124
125 /*
126 * Do the HI16 relocation. Note that we actually don't
127 * need to know anything about the LO16 itself, except
128 * where to find the low 16 bits of the addend needed
129 * by the LO16.
130 */
131 insn = *l->addr;
132 val = ((insn & 0xffff) << 16) + vallo;
133 val += v;
134
135 /*
136 * Account for the sign extension that will happen in
137 * the low bits.
138 */
139 val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;
140
141 insn = (insn & ~0xffff) | val;
142 *l->addr = insn;
143
144 next = l->next;
145 kfree(l);
146 l = next;
147 }
148
149 me->arch.r_mips_hi16_list = NULL;
150 }
151
152 /*
153 * Ok, we're done with the HI16 relocs. Now deal with the LO16.
154 */
155 val = v + vallo;
156 insnlo = (insnlo & ~0xffff) | (val & 0xffff);
157 *location = insnlo;
158
159 return 0;
160
161 out_danger:
162 free_relocation_chain(l);
163 me->arch.r_mips_hi16_list = NULL;
164
165 pr_err("module %s: dangerous R_MIPS_LO16 relocation\n", me->name);
166
167 return -ENOEXEC;
168 }
169
170 static int apply_r_mips_pc(struct module *me, u32 *location, u32 base,
171 Elf_Addr v, unsigned int bits)
172 {
173 unsigned long mask = GENMASK(bits - 1, 0);
174 unsigned long se_bits;
175 long offset;
176
177 if (v % 4) {
178 pr_err("module %s: dangerous R_MIPS_PC%u relocation\n",
179 me->name, bits);
180 return -ENOEXEC;
181 }
182
183 /* retrieve & sign extend implicit addend if any */
184 offset = base & mask;
185 offset |= (offset & BIT(bits - 1)) ? ~mask : 0;
186
187 offset += ((long)v - (long)location) >> 2;
188
189 /* check the sign bit onwards are identical - ie. we didn't overflow */
190 se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
191 if ((offset & ~mask) != (se_bits & ~mask)) {
192 pr_err("module %s: relocation overflow\n", me->name);
193 return -ENOEXEC;
194 }
195
196 *location = (*location & ~mask) | (offset & mask);
197
198 return 0;
199 }
200
201 static int apply_r_mips_pc16(struct module *me, u32 *location, u32 base,
202 Elf_Addr v)
203 {
204 return apply_r_mips_pc(me, location, base, v, 16);
205 }
206
207 static int apply_r_mips_pc21(struct module *me, u32 *location, u32 base,
208 Elf_Addr v)
209 {
210 return apply_r_mips_pc(me, location, base, v, 21);
211 }
212
213 static int apply_r_mips_pc26(struct module *me, u32 *location, u32 base,
214 Elf_Addr v)
215 {
216 return apply_r_mips_pc(me, location, base, v, 26);
217 }
218
219 static int apply_r_mips_64(u32 *location, Elf_Addr v, bool rela)
220 {
221 if (WARN_ON(!rela))
222 return -EINVAL;
223
224 *(Elf_Addr *)location = v;
225
226 return 0;
227 }
228
229 static int apply_r_mips_higher(u32 *location, Elf_Addr v, bool rela)
230 {
231 if (WARN_ON(!rela))
232 return -EINVAL;
233
234 *location = (*location & 0xffff0000) |
235 ((((long long)v + 0x80008000LL) >> 32) & 0xffff);
236
237 return 0;
238 }
239
240 static int apply_r_mips_highest(u32 *location, Elf_Addr v, bool rela)
241 {
242 if (WARN_ON(!rela))
243 return -EINVAL;
244
245 *location = (*location & 0xffff0000) |
246 ((((long long)v + 0x800080008000LL) >> 48) & 0xffff);
247
248 return 0;
249 }
250
251 /**
252 * reloc_handler() - Apply a particular relocation to a module
253 * @type: type of the relocation to apply
254 * @me: the module to apply the reloc to
255 * @location: the address at which the reloc is to be applied
256 * @base: the existing value at location for REL-style; 0 for RELA-style
257 * @v: the value of the reloc, with addend for RELA-style
258 * @rela: indication of is this a RELA (true) or REL (false) relocation
259 *
260 * Each implemented relocation function applies a particular type of
261 * relocation to the module @me. Relocs that may be found in either REL or RELA
262 * variants can be handled by making use of the @base & @v parameters which are
263 * set to values which abstract the difference away from the particular reloc
264 * implementations.
265 *
266 * Return: 0 upon success, else -ERRNO
267 */
268 static int reloc_handler(u32 type, struct module *me, u32 *location, u32 base,
269 Elf_Addr v, bool rela)
270 {
271 switch (type) {
272 case R_MIPS_NONE:
273 break;
274 case R_MIPS_32:
275 apply_r_mips_32(location, base, v);
276 break;
277 case R_MIPS_26:
278 return apply_r_mips_26(me, location, base, v);
279 case R_MIPS_HI16:
280 return apply_r_mips_hi16(me, location, v, rela);
281 case R_MIPS_LO16:
282 return apply_r_mips_lo16(me, location, base, v, rela);
283 case R_MIPS_PC16:
284 return apply_r_mips_pc16(me, location, base, v);
285 case R_MIPS_PC21_S2:
286 return apply_r_mips_pc21(me, location, base, v);
287 case R_MIPS_PC26_S2:
288 return apply_r_mips_pc26(me, location, base, v);
289 case R_MIPS_64:
290 return apply_r_mips_64(location, v, rela);
291 case R_MIPS_HIGHER:
292 return apply_r_mips_higher(location, v, rela);
293 case R_MIPS_HIGHEST:
294 return apply_r_mips_highest(location, v, rela);
295 default:
296 pr_err("%s: Unknown relocation type %u\n", me->name, type);
297 return -EINVAL;
298 }
299
300 return 0;
301 }
302
303 static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
304 unsigned int symindex, unsigned int relsec,
305 struct module *me, bool rela)
306 {
307 union {
308 Elf_Mips_Rel *rel;
309 Elf_Mips_Rela *rela;
310 } r;
311 Elf_Sym *sym;
312 u32 *location, base;
313 unsigned int i, type;
314 Elf_Addr v;
315 int err = 0;
316 size_t reloc_sz;
317
318 pr_debug("Applying relocate section %u to %u\n", relsec,
319 sechdrs[relsec].sh_info);
320
321 r.rel = (void *)sechdrs[relsec].sh_addr;
322 reloc_sz = rela ? sizeof(*r.rela) : sizeof(*r.rel);
323 me->arch.r_mips_hi16_list = NULL;
324 for (i = 0; i < sechdrs[relsec].sh_size / reloc_sz; i++) {
325 /* This is where to make the change */
326 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
327 + r.rel->r_offset;
328 /* This is the symbol it is referring to */
329 sym = (Elf_Sym *)sechdrs[symindex].sh_addr
330 + ELF_MIPS_R_SYM(*r.rel);
331 if (sym->st_value >= -MAX_ERRNO) {
332 /* Ignore unresolved weak symbol */
333 if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
334 continue;
335 pr_warn("%s: Unknown symbol %s\n",
336 me->name, strtab + sym->st_name);
337 err = -ENOENT;
338 goto out;
339 }
340
341 type = ELF_MIPS_R_TYPE(*r.rel);
342
343 if (rela) {
344 v = sym->st_value + r.rela->r_addend;
345 base = 0;
346 r.rela = &r.rela[1];
347 } else {
348 v = sym->st_value;
349 base = *location;
350 r.rel = &r.rel[1];
351 }
352
353 err = reloc_handler(type, me, location, base, v, rela);
354 if (err)
355 goto out;
356 }
357
358 out:
359 /*
360 * Normally the hi16 list should be deallocated at this point. A
361 * malformed binary however could contain a series of R_MIPS_HI16
362 * relocations not followed by a R_MIPS_LO16 relocation, or if we hit
363 * an error processing a reloc we might have gotten here before
364 * reaching the R_MIPS_LO16. In either case, free up the list and
365 * return an error.
366 */
367 if (me->arch.r_mips_hi16_list) {
368 free_relocation_chain(me->arch.r_mips_hi16_list);
369 me->arch.r_mips_hi16_list = NULL;
370 err = err ?: -ENOEXEC;
371 }
372
373 return err;
374 }
375
376 int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
377 unsigned int symindex, unsigned int relsec,
378 struct module *me)
379 {
380 return __apply_relocate(sechdrs, strtab, symindex, relsec, me, false);
381 }
382
383 #ifdef CONFIG_MODULES_USE_ELF_RELA
384 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
385 unsigned int symindex, unsigned int relsec,
386 struct module *me)
387 {
388 return __apply_relocate(sechdrs, strtab, symindex, relsec, me, true);
389 }
390 #endif /* CONFIG_MODULES_USE_ELF_RELA */
391
392 /* Given an address, look for it in the module exception tables. */
393 const struct exception_table_entry *search_module_dbetables(unsigned long addr)
394 {
395 unsigned long flags;
396 const struct exception_table_entry *e = NULL;
397 struct mod_arch_specific *dbe;
398
399 spin_lock_irqsave(&dbe_lock, flags);
400 list_for_each_entry(dbe, &dbe_list, dbe_list) {
401 e = search_extable(dbe->dbe_start,
402 dbe->dbe_end - dbe->dbe_start, addr);
403 if (e)
404 break;
405 }
406 spin_unlock_irqrestore(&dbe_lock, flags);
407
408 /* Now, if we found one, we are running inside it now, hence
409 we cannot unload the module, hence no refcnt needed. */
410 return e;
411 }
412
413 /* Put in dbe list if necessary. */
414 int module_finalize(const Elf_Ehdr *hdr,
415 const Elf_Shdr *sechdrs,
416 struct module *me)
417 {
418 const Elf_Shdr *s;
419 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
420
421 if (IS_ENABLED(CONFIG_JUMP_LABEL))
422 jump_label_apply_nops(me);
423
424 INIT_LIST_HEAD(&me->arch.dbe_list);
425 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
426 if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)
427 continue;
428 me->arch.dbe_start = (void *)s->sh_addr;
429 me->arch.dbe_end = (void *)s->sh_addr + s->sh_size;
430 spin_lock_irq(&dbe_lock);
431 list_add(&me->arch.dbe_list, &dbe_list);
432 spin_unlock_irq(&dbe_lock);
433 }
434 return 0;
435 }
436
437 void module_arch_cleanup(struct module *mod)
438 {
439 spin_lock_irq(&dbe_lock);
440 list_del(&mod->arch.dbe_list);
441 spin_unlock_irq(&dbe_lock);
442 }
443
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