1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/arch/arm/kernel/module.c
4 *
5 * Copyright (C) 2002 Russell King.
6 * Modified for nommu by Hyok S. Choi
7 *
8 * Module allocation method suggested by Andi Kleen.
9 */
10#include <linux/module.h>
11#include <linux/moduleloader.h>
12#include <linux/kernel.h>
13#include <linux/mm.h>
14#include <linux/elf.h>
15#include <linux/fs.h>
16#include <linux/string.h>
17
18#include <asm/sections.h>
19#include <asm/smp_plat.h>
20#include <asm/unwind.h>
21#include <asm/opcodes.h>
22
23bool module_init_section(const char *name)
24{
25 return strstarts(str: name, prefix: ".init") ||
26 strstarts(str: name, prefix: ".ARM.extab.init") ||
27 strstarts(str: name, prefix: ".ARM.exidx.init");
28}
29
30bool module_exit_section(const char *name)
31{
32 return strstarts(str: name, prefix: ".exit") ||
33 strstarts(str: name, prefix: ".ARM.extab.exit") ||
34 strstarts(str: name, prefix: ".ARM.exidx.exit");
35}
36
37#ifdef CONFIG_ARM_HAS_GROUP_RELOCS
38/*
39 * This implements the partitioning algorithm for group relocations as
40 * documented in the ARM AArch32 ELF psABI (IHI 0044).
41 *
42 * A single PC-relative symbol reference is divided in up to 3 add or subtract
43 * operations, where the final one could be incorporated into a load/store
44 * instruction with immediate offset. E.g.,
45 *
46 * ADD Rd, PC, #... or ADD Rd, PC, #...
47 * ADD Rd, Rd, #... ADD Rd, Rd, #...
48 * LDR Rd, [Rd, #...] ADD Rd, Rd, #...
49 *
50 * The latter has a guaranteed range of only 16 MiB (3x8 == 24 bits), so it is
51 * of limited use in the kernel. However, the ADD/ADD/LDR combo has a range of
52 * -/+ 256 MiB, (2x8 + 12 == 28 bits), which means it has sufficient range for
53 * any in-kernel symbol reference (unless module PLTs are being used).
54 *
55 * The main advantage of this approach over the typical pattern using a literal
56 * load is that literal loads may miss in the D-cache, and generally lead to
57 * lower cache efficiency for variables that are referenced often from many
58 * different places in the code.
59 */
60static u32 get_group_rem(u32 group, u32 *offset)
61{
62 u32 val = *offset;
63 u32 shift;
64 do {
65 shift = val ? (31 - __fls(val)) & ~1 : 32;
66 *offset = val;
67 if (!val)
68 break;
69 val &= 0xffffff >> shift;
70 } while (group--);
71 return shift;
72}
73#endif
74
75int
76apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
77 unsigned int relindex, struct module *module)
78{
79 Elf32_Shdr *symsec = sechdrs + symindex;
80 Elf32_Shdr *relsec = sechdrs + relindex;
81 Elf32_Shdr *dstsec = sechdrs + relsec->sh_info;
82 Elf32_Rel *rel = (void *)relsec->sh_addr;
83 unsigned int i;
84
85 for (i = 0; i < relsec->sh_size / sizeof(Elf32_Rel); i++, rel++) {
86 unsigned long loc;
87 Elf32_Sym *sym;
88 const char *symname;
89#ifdef CONFIG_ARM_HAS_GROUP_RELOCS
90 u32 shift, group = 1;
91#endif
92 s32 offset;
93 u32 tmp;
94#ifdef CONFIG_THUMB2_KERNEL
95 u32 upper, lower, sign, j1, j2;
96#endif
97
98 offset = ELF32_R_SYM(rel->r_info);
99 if (offset < 0 || offset > (symsec->sh_size / sizeof(Elf32_Sym))) {
100 pr_err("%s: section %u reloc %u: bad relocation sym offset\n",
101 module->name, relindex, i);
102 return -ENOEXEC;
103 }
104
105 sym = ((Elf32_Sym *)symsec->sh_addr) + offset;
106 symname = strtab + sym->st_name;
107
108 if (rel->r_offset < 0 || rel->r_offset > dstsec->sh_size - sizeof(u32)) {
109 pr_err("%s: section %u reloc %u sym '%s': out of bounds relocation, offset %d size %u\n",
110 module->name, relindex, i, symname,
111 rel->r_offset, dstsec->sh_size);
112 return -ENOEXEC;
113 }
114
115 loc = dstsec->sh_addr + rel->r_offset;
116
117 switch (ELF32_R_TYPE(rel->r_info)) {
118 case R_ARM_NONE:
119 /* ignore */
120 break;
121
122 case R_ARM_ABS32:
123 case R_ARM_TARGET1:
124 *(u32 *)loc += sym->st_value;
125 break;
126
127 case R_ARM_PC24:
128 case R_ARM_CALL:
129 case R_ARM_JUMP24:
130 if (sym->st_value & 3) {
131 pr_err("%s: section %u reloc %u sym '%s': unsupported interworking call (ARM -> Thumb)\n",
132 module->name, relindex, i, symname);
133 return -ENOEXEC;
134 }
135
136 offset = __mem_to_opcode_arm(*(u32 *)loc);
137 offset = (offset & 0x00ffffff) << 2;
138 offset = sign_extend32(value: offset, index: 25);
139
140 offset += sym->st_value - loc;
141
142 /*
143 * Route through a PLT entry if 'offset' exceeds the
144 * supported range. Note that 'offset + loc + 8'
145 * contains the absolute jump target, i.e.,
146 * @sym + addend, corrected for the +8 PC bias.
147 */
148 if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS) &&
149 (offset <= (s32)0xfe000000 ||
150 offset >= (s32)0x02000000))
151 offset = get_module_plt(module, loc,
152 offset + loc + 8)
153 - loc - 8;
154
155 if (offset <= (s32)0xfe000000 ||
156 offset >= (s32)0x02000000) {
157 pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n",
158 module->name, relindex, i, symname,
159 ELF32_R_TYPE(rel->r_info), loc,
160 sym->st_value);
161 return -ENOEXEC;
162 }
163
164 offset >>= 2;
165 offset &= 0x00ffffff;
166
167 *(u32 *)loc &= __opcode_to_mem_arm(0xff000000);
168 *(u32 *)loc |= __opcode_to_mem_arm(offset);
169 break;
170
171 case R_ARM_V4BX:
172 /* Preserve Rm and the condition code. Alter
173 * other bits to re-code instruction as
174 * MOV PC,Rm.
175 */
176 *(u32 *)loc &= __opcode_to_mem_arm(0xf000000f);
177 *(u32 *)loc |= __opcode_to_mem_arm(0x01a0f000);
178 break;
179
180 case R_ARM_PREL31:
181 offset = (*(s32 *)loc << 1) >> 1; /* sign extend */
182 offset += sym->st_value - loc;
183 if (offset >= 0x40000000 || offset < -0x40000000) {
184 pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n",
185 module->name, relindex, i, symname,
186 ELF32_R_TYPE(rel->r_info), loc,
187 sym->st_value);
188 return -ENOEXEC;
189 }
190 *(u32 *)loc &= 0x80000000;
191 *(u32 *)loc |= offset & 0x7fffffff;
192 break;
193
194 case R_ARM_REL32:
195 *(u32 *)loc += sym->st_value - loc;
196 break;
197
198 case R_ARM_MOVW_ABS_NC:
199 case R_ARM_MOVT_ABS:
200 case R_ARM_MOVW_PREL_NC:
201 case R_ARM_MOVT_PREL:
202 offset = tmp = __mem_to_opcode_arm(*(u32 *)loc);
203 offset = ((offset & 0xf0000) >> 4) | (offset & 0xfff);
204 offset = sign_extend32(value: offset, index: 15);
205
206 offset += sym->st_value;
207 if (ELF32_R_TYPE(rel->r_info) == R_ARM_MOVT_PREL ||
208 ELF32_R_TYPE(rel->r_info) == R_ARM_MOVW_PREL_NC)
209 offset -= loc;
210 if (ELF32_R_TYPE(rel->r_info) == R_ARM_MOVT_ABS ||
211 ELF32_R_TYPE(rel->r_info) == R_ARM_MOVT_PREL)
212 offset >>= 16;
213
214 tmp &= 0xfff0f000;
215 tmp |= ((offset & 0xf000) << 4) |
216 (offset & 0x0fff);
217
218 *(u32 *)loc = __opcode_to_mem_arm(tmp);
219 break;
220
221#ifdef CONFIG_ARM_HAS_GROUP_RELOCS
222 case R_ARM_ALU_PC_G0_NC:
223 group = 0;
224 fallthrough;
225 case R_ARM_ALU_PC_G1_NC:
226 tmp = __mem_to_opcode_arm(*(u32 *)loc);
227 offset = ror32(tmp & 0xff, (tmp & 0xf00) >> 7);
228 if (tmp & BIT(22))
229 offset = -offset;
230 offset += sym->st_value - loc;
231 if (offset < 0) {
232 offset = -offset;
233 tmp = (tmp & ~BIT(23)) | BIT(22); // SUB opcode
234 } else {
235 tmp = (tmp & ~BIT(22)) | BIT(23); // ADD opcode
236 }
237
238 shift = get_group_rem(group, &offset);
239 if (shift < 24) {
240 offset >>= 24 - shift;
241 offset |= (shift + 8) << 7;
242 }
243 *(u32 *)loc = __opcode_to_mem_arm((tmp & ~0xfff) | offset);
244 break;
245
246 case R_ARM_LDR_PC_G2:
247 tmp = __mem_to_opcode_arm(*(u32 *)loc);
248 offset = tmp & 0xfff;
249 if (~tmp & BIT(23)) // U bit cleared?
250 offset = -offset;
251 offset += sym->st_value - loc;
252 if (offset < 0) {
253 offset = -offset;
254 tmp &= ~BIT(23); // clear U bit
255 } else {
256 tmp |= BIT(23); // set U bit
257 }
258 get_group_rem(2, &offset);
259
260 if (offset > 0xfff) {
261 pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n",
262 module->name, relindex, i, symname,
263 ELF32_R_TYPE(rel->r_info), loc,
264 sym->st_value);
265 return -ENOEXEC;
266 }
267 *(u32 *)loc = __opcode_to_mem_arm((tmp & ~0xfff) | offset);
268 break;
269#endif
270#ifdef CONFIG_THUMB2_KERNEL
271 case R_ARM_THM_CALL:
272 case R_ARM_THM_JUMP24:
273 /*
274 * For function symbols, only Thumb addresses are
275 * allowed (no interworking).
276 *
277 * For non-function symbols, the destination
278 * has no specific ARM/Thumb disposition, so
279 * the branch is resolved under the assumption
280 * that interworking is not required.
281 */
282 if (ELF32_ST_TYPE(sym->st_info) == STT_FUNC &&
283 !(sym->st_value & 1)) {
284 pr_err("%s: section %u reloc %u sym '%s': unsupported interworking call (Thumb -> ARM)\n",
285 module->name, relindex, i, symname);
286 return -ENOEXEC;
287 }
288
289 upper = __mem_to_opcode_thumb16(*(u16 *)loc);
290 lower = __mem_to_opcode_thumb16(*(u16 *)(loc + 2));
291
292 /*
293 * 25 bit signed address range (Thumb-2 BL and B.W
294 * instructions):
295 * S:I1:I2:imm10:imm11:0
296 * where:
297 * S = upper[10] = offset[24]
298 * I1 = ~(J1 ^ S) = offset[23]
299 * I2 = ~(J2 ^ S) = offset[22]
300 * imm10 = upper[9:0] = offset[21:12]
301 * imm11 = lower[10:0] = offset[11:1]
302 * J1 = lower[13]
303 * J2 = lower[11]
304 */
305 sign = (upper >> 10) & 1;
306 j1 = (lower >> 13) & 1;
307 j2 = (lower >> 11) & 1;
308 offset = (sign << 24) | ((~(j1 ^ sign) & 1) << 23) |
309 ((~(j2 ^ sign) & 1) << 22) |
310 ((upper & 0x03ff) << 12) |
311 ((lower & 0x07ff) << 1);
312 offset = sign_extend32(offset, 24);
313 offset += sym->st_value - loc;
314
315 /*
316 * Route through a PLT entry if 'offset' exceeds the
317 * supported range.
318 */
319 if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS) &&
320 (offset <= (s32)0xff000000 ||
321 offset >= (s32)0x01000000))
322 offset = get_module_plt(module, loc,
323 offset + loc + 4)
324 - loc - 4;
325
326 if (offset <= (s32)0xff000000 ||
327 offset >= (s32)0x01000000) {
328 pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n",
329 module->name, relindex, i, symname,
330 ELF32_R_TYPE(rel->r_info), loc,
331 sym->st_value);
332 return -ENOEXEC;
333 }
334
335 sign = (offset >> 24) & 1;
336 j1 = sign ^ (~(offset >> 23) & 1);
337 j2 = sign ^ (~(offset >> 22) & 1);
338 upper = (u16)((upper & 0xf800) | (sign << 10) |
339 ((offset >> 12) & 0x03ff));
340 lower = (u16)((lower & 0xd000) |
341 (j1 << 13) | (j2 << 11) |
342 ((offset >> 1) & 0x07ff));
343
344 *(u16 *)loc = __opcode_to_mem_thumb16(upper);
345 *(u16 *)(loc + 2) = __opcode_to_mem_thumb16(lower);
346 break;
347
348 case R_ARM_THM_MOVW_ABS_NC:
349 case R_ARM_THM_MOVT_ABS:
350 case R_ARM_THM_MOVW_PREL_NC:
351 case R_ARM_THM_MOVT_PREL:
352 upper = __mem_to_opcode_thumb16(*(u16 *)loc);
353 lower = __mem_to_opcode_thumb16(*(u16 *)(loc + 2));
354
355 /*
356 * MOVT/MOVW instructions encoding in Thumb-2:
357 *
358 * i = upper[10]
359 * imm4 = upper[3:0]
360 * imm3 = lower[14:12]
361 * imm8 = lower[7:0]
362 *
363 * imm16 = imm4:i:imm3:imm8
364 */
365 offset = ((upper & 0x000f) << 12) |
366 ((upper & 0x0400) << 1) |
367 ((lower & 0x7000) >> 4) | (lower & 0x00ff);
368 offset = sign_extend32(offset, 15);
369 offset += sym->st_value;
370
371 if (ELF32_R_TYPE(rel->r_info) == R_ARM_THM_MOVT_PREL ||
372 ELF32_R_TYPE(rel->r_info) == R_ARM_THM_MOVW_PREL_NC)
373 offset -= loc;
374 if (ELF32_R_TYPE(rel->r_info) == R_ARM_THM_MOVT_ABS ||
375 ELF32_R_TYPE(rel->r_info) == R_ARM_THM_MOVT_PREL)
376 offset >>= 16;
377
378 upper = (u16)((upper & 0xfbf0) |
379 ((offset & 0xf000) >> 12) |
380 ((offset & 0x0800) >> 1));
381 lower = (u16)((lower & 0x8f00) |
382 ((offset & 0x0700) << 4) |
383 (offset & 0x00ff));
384 *(u16 *)loc = __opcode_to_mem_thumb16(upper);
385 *(u16 *)(loc + 2) = __opcode_to_mem_thumb16(lower);
386 break;
387#endif
388
389 default:
390 pr_err("%s: unknown relocation: %u\n",
391 module->name, ELF32_R_TYPE(rel->r_info));
392 return -ENOEXEC;
393 }
394 }
395 return 0;
396}
397
398static const Elf_Shdr *find_mod_section(const Elf32_Ehdr *hdr,
399 const Elf_Shdr *sechdrs, const char *name)
400{
401 const Elf_Shdr *s, *se;
402 const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
403
404 for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++)
405 if (strcmp(name, secstrs + s->sh_name) == 0)
406 return s;
407
408 return NULL;
409}
410
411extern void fixup_pv_table(const void *, unsigned long);
412extern void fixup_smp(const void *, unsigned long);
413
414int module_finalize(const Elf32_Ehdr *hdr, const Elf_Shdr *sechdrs,
415 struct module *mod)
416{
417 const Elf_Shdr *s = NULL;
418#ifdef CONFIG_ARM_UNWIND
419 const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
420 const Elf_Shdr *sechdrs_end = sechdrs + hdr->e_shnum;
421 struct list_head *unwind_list = &mod->arch.unwind_list;
422
423 INIT_LIST_HEAD(unwind_list);
424 mod->arch.init_table = NULL;
425
426 for (s = sechdrs; s < sechdrs_end; s++) {
427 const char *secname = secstrs + s->sh_name;
428 const char *txtname;
429 const Elf_Shdr *txt_sec;
430
431 if (!(s->sh_flags & SHF_ALLOC) ||
432 s->sh_type != ELF_SECTION_UNWIND)
433 continue;
434
435 if (!strcmp(".ARM.exidx", secname))
436 txtname = ".text";
437 else
438 txtname = secname + strlen(".ARM.exidx");
439 txt_sec = find_mod_section(hdr, sechdrs, txtname);
440
441 if (txt_sec) {
442 struct unwind_table *table =
443 unwind_table_add(s->sh_addr,
444 s->sh_size,
445 txt_sec->sh_addr,
446 txt_sec->sh_size);
447
448 list_add(&table->mod_list, unwind_list);
449
450 /* save init table for module_arch_freeing_init */
451 if (strcmp(".ARM.exidx.init.text", secname) == 0)
452 mod->arch.init_table = table;
453 }
454 }
455#endif
456#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
457 s = find_mod_section(hdr, sechdrs, ".pv_table");
458 if (s)
459 fixup_pv_table((void *)s->sh_addr, s->sh_size);
460#endif
461 s = find_mod_section(hdr, sechdrs, name: ".alt.smp.init");
462 if (s && !is_smp())
463#ifdef CONFIG_SMP_ON_UP
464 fixup_smp((void *)s->sh_addr, s->sh_size);
465#else
466 return -EINVAL;
467#endif
468 return 0;
469}
470
471void
472module_arch_cleanup(struct module *mod)
473{
474#ifdef CONFIG_ARM_UNWIND
475 struct unwind_table *tmp;
476 struct unwind_table *n;
477
478 list_for_each_entry_safe(tmp, n,
479 &mod->arch.unwind_list, mod_list) {
480 list_del(&tmp->mod_list);
481 unwind_table_del(tmp);
482 }
483 mod->arch.init_table = NULL;
484#endif
485}
486
487void __weak module_arch_freeing_init(struct module *mod)
488{
489#ifdef CONFIG_ARM_UNWIND
490 struct unwind_table *init = mod->arch.init_table;
491
492 if (init) {
493 mod->arch.init_table = NULL;
494 list_del(&init->mod_list);
495 unwind_table_del(init);
496 }
497#endif
498}
499

source code of linux/arch/arm/kernel/module.c

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