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Linux/arch/mips/kernel/module.c

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  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/vmalloc.h>
 17 #include <linux/slab.h>
 18 #include <linux/fs.h>
 19 #include <linux/string.h>
 20 #include <linux/kernel.h>
 21 #include <linux/spinlock.h>
 22 #include <linux/jump_label.h>
 23 
 24 #include <asm/pgtable.h>        /* MODULE_START */
 25 
 26 struct mips_hi16 {
 27         struct mips_hi16 *next;
 28         Elf_Addr *addr;
 29         Elf_Addr value;
 30 };
 31 
 32 static LIST_HEAD(dbe_list);
 33 static DEFINE_SPINLOCK(dbe_lock);
 34 
 35 #ifdef MODULE_START
 36 void *module_alloc(unsigned long size)
 37 {
 38         return __vmalloc_node_range(size, 1, MODULE_START, MODULE_END,
 39                                 GFP_KERNEL, PAGE_KERNEL, 0, NUMA_NO_NODE,
 40                                 __builtin_return_address(0));
 41 }
 42 #endif
 43 
 44 static int apply_r_mips_none(struct module *me, u32 *location,
 45                              u32 base, Elf_Addr v, bool rela)
 46 {
 47         return 0;
 48 }
 49 
 50 static int apply_r_mips_32(struct module *me, u32 *location,
 51                            u32 base, Elf_Addr v, bool rela)
 52 {
 53         *location = base + v;
 54 
 55         return 0;
 56 }
 57 
 58 static int apply_r_mips_26(struct module *me, u32 *location,
 59                            u32 base, Elf_Addr v, bool rela)
 60 {
 61         if (v % 4) {
 62                 pr_err("module %s: dangerous R_MIPS_26 relocation\n",
 63                        me->name);
 64                 return -ENOEXEC;
 65         }
 66 
 67         if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
 68                 pr_err("module %s: relocation overflow\n",
 69                        me->name);
 70                 return -ENOEXEC;
 71         }
 72 
 73         *location = (*location & ~0x03ffffff) |
 74                     ((base + (v >> 2)) & 0x03ffffff);
 75 
 76         return 0;
 77 }
 78 
 79 static int apply_r_mips_hi16(struct module *me, u32 *location,
 80                              u32 base, Elf_Addr v, bool rela)
 81 {
 82         struct mips_hi16 *n;
 83 
 84         if (rela) {
 85                 *location = (*location & 0xffff0000) |
 86                             ((((long long) v + 0x8000LL) >> 16) & 0xffff);
 87                 return 0;
 88         }
 89 
 90         /*
 91          * We cannot relocate this one now because we don't know the value of
 92          * the carry we need to add.  Save the information, and let LO16 do the
 93          * actual relocation.
 94          */
 95         n = kmalloc(sizeof *n, GFP_KERNEL);
 96         if (!n)
 97                 return -ENOMEM;
 98 
 99         n->addr = (Elf_Addr *)location;
100         n->value = v;
101         n->next = me->arch.r_mips_hi16_list;
102         me->arch.r_mips_hi16_list = n;
103 
104         return 0;
105 }
106 
107 static void free_relocation_chain(struct mips_hi16 *l)
108 {
109         struct mips_hi16 *next;
110 
111         while (l) {
112                 next = l->next;
113                 kfree(l);
114                 l = next;
115         }
116 }
117 
118 static int apply_r_mips_lo16(struct module *me, u32 *location,
119                              u32 base, Elf_Addr v, bool rela)
120 {
121         unsigned long insnlo = base;
122         struct mips_hi16 *l;
123         Elf_Addr val, vallo;
124 
125         if (rela) {
126                 *location = (*location & 0xffff0000) | (v & 0xffff);
127                 return 0;
128         }
129 
130         /* Sign extend the addend we extract from the lo insn.  */
131         vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;
132 
133         if (me->arch.r_mips_hi16_list != NULL) {
134                 l = me->arch.r_mips_hi16_list;
135                 while (l != NULL) {
136                         struct mips_hi16 *next;
137                         unsigned long insn;
138 
139                         /*
140                          * The value for the HI16 had best be the same.
141                          */
142                         if (v != l->value)
143                                 goto out_danger;
144 
145                         /*
146                          * Do the HI16 relocation.  Note that we actually don't
147                          * need to know anything about the LO16 itself, except
148                          * where to find the low 16 bits of the addend needed
149                          * by the LO16.
150                          */
151                         insn = *l->addr;
152                         val = ((insn & 0xffff) << 16) + vallo;
153                         val += v;
154 
155                         /*
156                          * Account for the sign extension that will happen in
157                          * the low bits.
158                          */
159                         val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;
160 
161                         insn = (insn & ~0xffff) | val;
162                         *l->addr = insn;
163 
164                         next = l->next;
165                         kfree(l);
166                         l = next;
167                 }
168 
169                 me->arch.r_mips_hi16_list = NULL;
170         }
171 
172         /*
173          * Ok, we're done with the HI16 relocs.  Now deal with the LO16.
174          */
175         val = v + vallo;
176         insnlo = (insnlo & ~0xffff) | (val & 0xffff);
177         *location = insnlo;
178 
179         return 0;
180 
181 out_danger:
182         free_relocation_chain(l);
183         me->arch.r_mips_hi16_list = NULL;
184 
185         pr_err("module %s: dangerous R_MIPS_LO16 relocation\n", me->name);
186 
187         return -ENOEXEC;
188 }
189 
190 static int apply_r_mips_pc(struct module *me, u32 *location, u32 base,
191                            Elf_Addr v, unsigned int bits)
192 {
193         unsigned long mask = GENMASK(bits - 1, 0);
194         unsigned long se_bits;
195         long offset;
196 
197         if (v % 4) {
198                 pr_err("module %s: dangerous R_MIPS_PC%u relocation\n",
199                        me->name, bits);
200                 return -ENOEXEC;
201         }
202 
203         /* retrieve & sign extend implicit addend if any */
204         offset = base & mask;
205         offset |= (offset & BIT(bits - 1)) ? ~mask : 0;
206 
207         offset += ((long)v - (long)location) >> 2;
208 
209         /* check the sign bit onwards are identical - ie. we didn't overflow */
210         se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
211         if ((offset & ~mask) != (se_bits & ~mask)) {
212                 pr_err("module %s: relocation overflow\n", me->name);
213                 return -ENOEXEC;
214         }
215 
216         *location = (*location & ~mask) | (offset & mask);
217 
218         return 0;
219 }
220 
221 static int apply_r_mips_pc16(struct module *me, u32 *location,
222                              u32 base, Elf_Addr v, bool rela)
223 {
224         return apply_r_mips_pc(me, location, base, v, 16);
225 }
226 
227 static int apply_r_mips_pc21(struct module *me, u32 *location,
228                              u32 base, Elf_Addr v, bool rela)
229 {
230         return apply_r_mips_pc(me, location, base, v, 21);
231 }
232 
233 static int apply_r_mips_pc26(struct module *me, u32 *location,
234                              u32 base, Elf_Addr v, bool rela)
235 {
236         return apply_r_mips_pc(me, location, base, v, 26);
237 }
238 
239 static int apply_r_mips_64(struct module *me, u32 *location,
240                            u32 base, Elf_Addr v, bool rela)
241 {
242         if (WARN_ON(!rela))
243                 return -EINVAL;
244 
245         *(Elf_Addr *)location = v;
246 
247         return 0;
248 }
249 
250 static int apply_r_mips_higher(struct module *me, u32 *location,
251                                u32 base, Elf_Addr v, bool rela)
252 {
253         if (WARN_ON(!rela))
254                 return -EINVAL;
255 
256         *location = (*location & 0xffff0000) |
257                     ((((long long)v + 0x80008000LL) >> 32) & 0xffff);
258 
259         return 0;
260 }
261 
262 static int apply_r_mips_highest(struct module *me, u32 *location,
263                                 u32 base, Elf_Addr v, bool rela)
264 {
265         if (WARN_ON(!rela))
266                 return -EINVAL;
267 
268         *location = (*location & 0xffff0000) |
269                     ((((long long)v + 0x800080008000LL) >> 48) & 0xffff);
270 
271         return 0;
272 }
273 
274 /**
275  * reloc_handler() - Apply a particular relocation to a module
276  * @me: the module to apply the reloc to
277  * @location: the address at which the reloc is to be applied
278  * @base: the existing value at location for REL-style; 0 for RELA-style
279  * @v: the value of the reloc, with addend for RELA-style
280  *
281  * Each implemented reloc_handler function applies a particular type of
282  * relocation to the module @me. Relocs that may be found in either REL or RELA
283  * variants can be handled by making use of the @base & @v parameters which are
284  * set to values which abstract the difference away from the particular reloc
285  * implementations.
286  *
287  * Return: 0 upon success, else -ERRNO
288  */
289 typedef int (*reloc_handler)(struct module *me, u32 *location,
290                              u32 base, Elf_Addr v, bool rela);
291 
292 /* The handlers for known reloc types */
293 static reloc_handler reloc_handlers[] = {
294         [R_MIPS_NONE]           = apply_r_mips_none,
295         [R_MIPS_32]             = apply_r_mips_32,
296         [R_MIPS_26]             = apply_r_mips_26,
297         [R_MIPS_HI16]           = apply_r_mips_hi16,
298         [R_MIPS_LO16]           = apply_r_mips_lo16,
299         [R_MIPS_PC16]           = apply_r_mips_pc16,
300         [R_MIPS_64]             = apply_r_mips_64,
301         [R_MIPS_HIGHER]         = apply_r_mips_higher,
302         [R_MIPS_HIGHEST]        = apply_r_mips_highest,
303         [R_MIPS_PC21_S2]        = apply_r_mips_pc21,
304         [R_MIPS_PC26_S2]        = apply_r_mips_pc26,
305 };
306 
307 static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
308                             unsigned int symindex, unsigned int relsec,
309                             struct module *me, bool rela)
310 {
311         union {
312                 Elf_Mips_Rel *rel;
313                 Elf_Mips_Rela *rela;
314         } r;
315         reloc_handler handler;
316         Elf_Sym *sym;
317         u32 *location, base;
318         unsigned int i, type;
319         Elf_Addr v;
320         int err = 0;
321         size_t reloc_sz;
322 
323         pr_debug("Applying relocate section %u to %u\n", relsec,
324                sechdrs[relsec].sh_info);
325 
326         r.rel = (void *)sechdrs[relsec].sh_addr;
327         reloc_sz = rela ? sizeof(*r.rela) : sizeof(*r.rel);
328         me->arch.r_mips_hi16_list = NULL;
329         for (i = 0; i < sechdrs[relsec].sh_size / reloc_sz; i++) {
330                 /* This is where to make the change */
331                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
332                         + r.rel->r_offset;
333                 /* This is the symbol it is referring to */
334                 sym = (Elf_Sym *)sechdrs[symindex].sh_addr
335                         + ELF_MIPS_R_SYM(*r.rel);
336                 if (sym->st_value >= -MAX_ERRNO) {
337                         /* Ignore unresolved weak symbol */
338                         if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
339                                 continue;
340                         pr_warn("%s: Unknown symbol %s\n",
341                                 me->name, strtab + sym->st_name);
342                         err = -ENOENT;
343                         goto out;
344                 }
345 
346                 type = ELF_MIPS_R_TYPE(*r.rel);
347                 if (type < ARRAY_SIZE(reloc_handlers))
348                         handler = reloc_handlers[type];
349                 else
350                         handler = NULL;
351 
352                 if (!handler) {
353                         pr_err("%s: Unknown relocation type %u\n",
354                                me->name, type);
355                         err = -EINVAL;
356                         goto out;
357                 }
358 
359                 if (rela) {
360                         v = sym->st_value + r.rela->r_addend;
361                         base = 0;
362                         r.rela = &r.rela[1];
363                 } else {
364                         v = sym->st_value;
365                         base = *location;
366                         r.rel = &r.rel[1];
367                 }
368 
369                 err = handler(me, location, base, v, rela);
370                 if (err)
371                         goto out;
372         }
373 
374 out:
375         /*
376          * Normally the hi16 list should be deallocated at this point. A
377          * malformed binary however could contain a series of R_MIPS_HI16
378          * relocations not followed by a R_MIPS_LO16 relocation, or if we hit
379          * an error processing a reloc we might have gotten here before
380          * reaching the R_MIPS_LO16. In either case, free up the list and
381          * return an error.
382          */
383         if (me->arch.r_mips_hi16_list) {
384                 free_relocation_chain(me->arch.r_mips_hi16_list);
385                 me->arch.r_mips_hi16_list = NULL;
386                 err = err ?: -ENOEXEC;
387         }
388 
389         return err;
390 }
391 
392 int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
393                    unsigned int symindex, unsigned int relsec,
394                    struct module *me)
395 {
396         return __apply_relocate(sechdrs, strtab, symindex, relsec, me, false);
397 }
398 
399 #ifdef CONFIG_MODULES_USE_ELF_RELA
400 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
401                        unsigned int symindex, unsigned int relsec,
402                        struct module *me)
403 {
404         return __apply_relocate(sechdrs, strtab, symindex, relsec, me, true);
405 }
406 #endif /* CONFIG_MODULES_USE_ELF_RELA */
407 
408 /* Given an address, look for it in the module exception tables. */
409 const struct exception_table_entry *search_module_dbetables(unsigned long addr)
410 {
411         unsigned long flags;
412         const struct exception_table_entry *e = NULL;
413         struct mod_arch_specific *dbe;
414 
415         spin_lock_irqsave(&dbe_lock, flags);
416         list_for_each_entry(dbe, &dbe_list, dbe_list) {
417                 e = search_extable(dbe->dbe_start,
418                                    dbe->dbe_end - dbe->dbe_start, addr);
419                 if (e)
420                         break;
421         }
422         spin_unlock_irqrestore(&dbe_lock, flags);
423 
424         /* Now, if we found one, we are running inside it now, hence
425            we cannot unload the module, hence no refcnt needed. */
426         return e;
427 }
428 
429 /* Put in dbe list if necessary. */
430 int module_finalize(const Elf_Ehdr *hdr,
431                     const Elf_Shdr *sechdrs,
432                     struct module *me)
433 {
434         const Elf_Shdr *s;
435         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
436 
437         /* Make jump label nops. */
438         jump_label_apply_nops(me);
439 
440         INIT_LIST_HEAD(&me->arch.dbe_list);
441         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
442                 if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)
443                         continue;
444                 me->arch.dbe_start = (void *)s->sh_addr;
445                 me->arch.dbe_end = (void *)s->sh_addr + s->sh_size;
446                 spin_lock_irq(&dbe_lock);
447                 list_add(&me->arch.dbe_list, &dbe_list);
448                 spin_unlock_irq(&dbe_lock);
449         }
450         return 0;
451 }
452 
453 void module_arch_cleanup(struct module *mod)
454 {
455         spin_lock_irq(&dbe_lock);
456         list_del(&mod->arch.dbe_list);
457         spin_unlock_irq(&dbe_lock);
458 }
459 

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