1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * AArch64 loadable module support.
4 *
5 * Copyright (C) 2012 ARM Limited
6 *
7 * Author: Will Deacon <will.deacon@arm.com>
8 */
9
10 #define pr_fmt(fmt) "Modules: " fmt
11
12 #include <linux/bitops.h>
13 #include <linux/elf.h>
14 #include <linux/ftrace.h>
15 #include <linux/gfp.h>
16 #include <linux/kasan.h>
17 #include <linux/kernel.h>
18 #include <linux/mm.h>
19 #include <linux/moduleloader.h>
20 #include <linux/random.h>
21 #include <linux/scs.h>
22 #include <linux/vmalloc.h>
23
24 #include <asm/alternative.h>
25 #include <asm/insn.h>
26 #include <asm/scs.h>
27 #include <asm/sections.h>
28
29 static u64 module_direct_base __ro_after_init = 0;
30 static u64 module_plt_base __ro_after_init = 0;
31
32 /*
33 * Choose a random page-aligned base address for a window of 'size' bytes which
34 * entirely contains the interval [start, end - 1].
35 */
random_bounding_box(u64 size,u64 start,u64 end)36 static u64 __init random_bounding_box(u64 size, u64 start, u64 end)
37 {
38 u64 max_pgoff, pgoff;
39
40 if ((end - start) >= size)
41 return 0;
42
43 max_pgoff = (size - (end - start)) / PAGE_SIZE;
44 pgoff = get_random_u32_inclusive(0, max_pgoff);
45
46 return start - pgoff * PAGE_SIZE;
47 }
48
49 /*
50 * Modules may directly reference data and text anywhere within the kernel
51 * image and other modules. References using PREL32 relocations have a +/-2G
52 * range, and so we need to ensure that the entire kernel image and all modules
53 * fall within a 2G window such that these are always within range.
54 *
55 * Modules may directly branch to functions and code within the kernel text,
56 * and to functions and code within other modules. These branches will use
57 * CALL26/JUMP26 relocations with a +/-128M range. Without PLTs, we must ensure
58 * that the entire kernel text and all module text falls within a 128M window
59 * such that these are always within range. With PLTs, we can expand this to a
60 * 2G window.
61 *
62 * We chose the 128M region to surround the entire kernel image (rather than
63 * just the text) as using the same bounds for the 128M and 2G regions ensures
64 * by construction that we never select a 128M region that is not a subset of
65 * the 2G region. For very large and unusual kernel configurations this means
66 * we may fall back to PLTs where they could have been avoided, but this keeps
67 * the logic significantly simpler.
68 */
module_init_limits(void)69 static int __init module_init_limits(void)
70 {
71 u64 kernel_end = (u64)_end;
72 u64 kernel_start = (u64)_text;
73 u64 kernel_size = kernel_end - kernel_start;
74
75 /*
76 * The default modules region is placed immediately below the kernel
77 * image, and is large enough to use the full 2G relocation range.
78 */
79 BUILD_BUG_ON(KIMAGE_VADDR != MODULES_END);
80 BUILD_BUG_ON(MODULES_VSIZE < SZ_2G);
81
82 if (!kaslr_enabled()) {
83 if (kernel_size < SZ_128M)
84 module_direct_base = kernel_end - SZ_128M;
85 if (kernel_size < SZ_2G)
86 module_plt_base = kernel_end - SZ_2G;
87 } else {
88 u64 min = kernel_start;
89 u64 max = kernel_end;
90
91 if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
92 pr_info("2G module region forced by RANDOMIZE_MODULE_REGION_FULL\n");
93 } else {
94 module_direct_base = random_bounding_box(SZ_128M, min, max);
95 if (module_direct_base) {
96 min = module_direct_base;
97 max = module_direct_base + SZ_128M;
98 }
99 }
100
101 module_plt_base = random_bounding_box(SZ_2G, min, max);
102 }
103
104 pr_info("%llu pages in range for non-PLT usage",
105 module_direct_base ? (SZ_128M - kernel_size) / PAGE_SIZE : 0);
106 pr_info("%llu pages in range for PLT usage",
107 module_plt_base ? (SZ_2G - kernel_size) / PAGE_SIZE : 0);
108
109 return 0;
110 }
111 subsys_initcall(module_init_limits);
112
module_alloc(unsigned long size)113 void *module_alloc(unsigned long size)
114 {
115 void *p = NULL;
116
117 /*
118 * Where possible, prefer to allocate within direct branch range of the
119 * kernel such that no PLTs are necessary.
120 */
121 if (module_direct_base) {
122 p = __vmalloc_node_range(size, MODULE_ALIGN,
123 module_direct_base,
124 module_direct_base + SZ_128M,
125 GFP_KERNEL | __GFP_NOWARN,
126 PAGE_KERNEL, 0, NUMA_NO_NODE,
127 __builtin_return_address(0));
128 }
129
130 if (!p && module_plt_base) {
131 p = __vmalloc_node_range(size, MODULE_ALIGN,
132 module_plt_base,
133 module_plt_base + SZ_2G,
134 GFP_KERNEL | __GFP_NOWARN,
135 PAGE_KERNEL, 0, NUMA_NO_NODE,
136 __builtin_return_address(0));
137 }
138
139 if (!p) {
140 pr_warn_ratelimited("%s: unable to allocate memory\n",
141 __func__);
142 }
143
144 if (p && (kasan_alloc_module_shadow(p, size, GFP_KERNEL) < 0)) {
145 vfree(p);
146 return NULL;
147 }
148
149 /* Memory is intended to be executable, reset the pointer tag. */
150 return kasan_reset_tag(p);
151 }
152
153 enum aarch64_reloc_op {
154 RELOC_OP_NONE,
155 RELOC_OP_ABS,
156 RELOC_OP_PREL,
157 RELOC_OP_PAGE,
158 };
159
do_reloc(enum aarch64_reloc_op reloc_op,__le32 * place,u64 val)160 static u64 do_reloc(enum aarch64_reloc_op reloc_op, __le32 *place, u64 val)
161 {
162 switch (reloc_op) {
163 case RELOC_OP_ABS:
164 return val;
165 case RELOC_OP_PREL:
166 return val - (u64)place;
167 case RELOC_OP_PAGE:
168 return (val & ~0xfff) - ((u64)place & ~0xfff);
169 case RELOC_OP_NONE:
170 return 0;
171 }
172
173 pr_err("do_reloc: unknown relocation operation %d\n", reloc_op);
174 return 0;
175 }
176
reloc_data(enum aarch64_reloc_op op,void * place,u64 val,int len)177 static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len)
178 {
179 s64 sval = do_reloc(op, place, val);
180
181 /*
182 * The ELF psABI for AArch64 documents the 16-bit and 32-bit place
183 * relative and absolute relocations as having a range of [-2^15, 2^16)
184 * or [-2^31, 2^32), respectively. However, in order to be able to
185 * detect overflows reliably, we have to choose whether we interpret
186 * such quantities as signed or as unsigned, and stick with it.
187 * The way we organize our address space requires a signed
188 * interpretation of 32-bit relative references, so let's use that
189 * for all R_AARCH64_PRELxx relocations. This means our upper
190 * bound for overflow detection should be Sxx_MAX rather than Uxx_MAX.
191 */
192
193 switch (len) {
194 case 16:
195 *(s16 *)place = sval;
196 switch (op) {
197 case RELOC_OP_ABS:
198 if (sval < 0 || sval > U16_MAX)
199 return -ERANGE;
200 break;
201 case RELOC_OP_PREL:
202 if (sval < S16_MIN || sval > S16_MAX)
203 return -ERANGE;
204 break;
205 default:
206 pr_err("Invalid 16-bit data relocation (%d)\n", op);
207 return 0;
208 }
209 break;
210 case 32:
211 *(s32 *)place = sval;
212 switch (op) {
213 case RELOC_OP_ABS:
214 if (sval < 0 || sval > U32_MAX)
215 return -ERANGE;
216 break;
217 case RELOC_OP_PREL:
218 if (sval < S32_MIN || sval > S32_MAX)
219 return -ERANGE;
220 break;
221 default:
222 pr_err("Invalid 32-bit data relocation (%d)\n", op);
223 return 0;
224 }
225 break;
226 case 64:
227 *(s64 *)place = sval;
228 break;
229 default:
230 pr_err("Invalid length (%d) for data relocation\n", len);
231 return 0;
232 }
233 return 0;
234 }
235
236 enum aarch64_insn_movw_imm_type {
237 AARCH64_INSN_IMM_MOVNZ,
238 AARCH64_INSN_IMM_MOVKZ,
239 };
240
reloc_insn_movw(enum aarch64_reloc_op op,__le32 * place,u64 val,int lsb,enum aarch64_insn_movw_imm_type imm_type)241 static int reloc_insn_movw(enum aarch64_reloc_op op, __le32 *place, u64 val,
242 int lsb, enum aarch64_insn_movw_imm_type imm_type)
243 {
244 u64 imm;
245 s64 sval;
246 u32 insn = le32_to_cpu(*place);
247
248 sval = do_reloc(op, place, val);
249 imm = sval >> lsb;
250
251 if (imm_type == AARCH64_INSN_IMM_MOVNZ) {
252 /*
253 * For signed MOVW relocations, we have to manipulate the
254 * instruction encoding depending on whether or not the
255 * immediate is less than zero.
256 */
257 insn &= ~(3 << 29);
258 if (sval >= 0) {
259 /* >=0: Set the instruction to MOVZ (opcode 10b). */
260 insn |= 2 << 29;
261 } else {
262 /*
263 * <0: Set the instruction to MOVN (opcode 00b).
264 * Since we've masked the opcode already, we
265 * don't need to do anything other than
266 * inverting the new immediate field.
267 */
268 imm = ~imm;
269 }
270 }
271
272 /* Update the instruction with the new encoding. */
273 insn = aarch64_insn_encode_immediate(AARCH64_INSN_IMM_16, insn, imm);
274 *place = cpu_to_le32(insn);
275
276 if (imm > U16_MAX)
277 return -ERANGE;
278
279 return 0;
280 }
281
reloc_insn_imm(enum aarch64_reloc_op op,__le32 * place,u64 val,int lsb,int len,enum aarch64_insn_imm_type imm_type)282 static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 *place, u64 val,
283 int lsb, int len, enum aarch64_insn_imm_type imm_type)
284 {
285 u64 imm, imm_mask;
286 s64 sval;
287 u32 insn = le32_to_cpu(*place);
288
289 /* Calculate the relocation value. */
290 sval = do_reloc(op, place, val);
291 sval >>= lsb;
292
293 /* Extract the value bits and shift them to bit 0. */
294 imm_mask = (BIT(lsb + len) - 1) >> lsb;
295 imm = sval & imm_mask;
296
297 /* Update the instruction's immediate field. */
298 insn = aarch64_insn_encode_immediate(imm_type, insn, imm);
299 *place = cpu_to_le32(insn);
300
301 /*
302 * Extract the upper value bits (including the sign bit) and
303 * shift them to bit 0.
304 */
305 sval = (s64)(sval & ~(imm_mask >> 1)) >> (len - 1);
306
307 /*
308 * Overflow has occurred if the upper bits are not all equal to
309 * the sign bit of the value.
310 */
311 if ((u64)(sval + 1) >= 2)
312 return -ERANGE;
313
314 return 0;
315 }
316
reloc_insn_adrp(struct module * mod,Elf64_Shdr * sechdrs,__le32 * place,u64 val)317 static int reloc_insn_adrp(struct module *mod, Elf64_Shdr *sechdrs,
318 __le32 *place, u64 val)
319 {
320 u32 insn;
321
322 if (!is_forbidden_offset_for_adrp(place))
323 return reloc_insn_imm(RELOC_OP_PAGE, place, val, 12, 21,
324 AARCH64_INSN_IMM_ADR);
325
326 /* patch ADRP to ADR if it is in range */
327 if (!reloc_insn_imm(RELOC_OP_PREL, place, val & ~0xfff, 0, 21,
328 AARCH64_INSN_IMM_ADR)) {
329 insn = le32_to_cpu(*place);
330 insn &= ~BIT(31);
331 } else {
332 /* out of range for ADR -> emit a veneer */
333 val = module_emit_veneer_for_adrp(mod, sechdrs, place, val & ~0xfff);
334 if (!val)
335 return -ENOEXEC;
336 insn = aarch64_insn_gen_branch_imm((u64)place, val,
337 AARCH64_INSN_BRANCH_NOLINK);
338 }
339
340 *place = cpu_to_le32(insn);
341 return 0;
342 }
343
apply_relocate_add(Elf64_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * me)344 int apply_relocate_add(Elf64_Shdr *sechdrs,
345 const char *strtab,
346 unsigned int symindex,
347 unsigned int relsec,
348 struct module *me)
349 {
350 unsigned int i;
351 int ovf;
352 bool overflow_check;
353 Elf64_Sym *sym;
354 void *loc;
355 u64 val;
356 Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
357
358 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
359 /* loc corresponds to P in the AArch64 ELF document. */
360 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
361 + rel[i].r_offset;
362
363 /* sym is the ELF symbol we're referring to. */
364 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
365 + ELF64_R_SYM(rel[i].r_info);
366
367 /* val corresponds to (S + A) in the AArch64 ELF document. */
368 val = sym->st_value + rel[i].r_addend;
369
370 /* Check for overflow by default. */
371 overflow_check = true;
372
373 /* Perform the static relocation. */
374 switch (ELF64_R_TYPE(rel[i].r_info)) {
375 /* Null relocations. */
376 case R_ARM_NONE:
377 case R_AARCH64_NONE:
378 ovf = 0;
379 break;
380
381 /* Data relocations. */
382 case R_AARCH64_ABS64:
383 overflow_check = false;
384 ovf = reloc_data(RELOC_OP_ABS, loc, val, 64);
385 break;
386 case R_AARCH64_ABS32:
387 ovf = reloc_data(RELOC_OP_ABS, loc, val, 32);
388 break;
389 case R_AARCH64_ABS16:
390 ovf = reloc_data(RELOC_OP_ABS, loc, val, 16);
391 break;
392 case R_AARCH64_PREL64:
393 overflow_check = false;
394 ovf = reloc_data(RELOC_OP_PREL, loc, val, 64);
395 break;
396 case R_AARCH64_PREL32:
397 ovf = reloc_data(RELOC_OP_PREL, loc, val, 32);
398 break;
399 case R_AARCH64_PREL16:
400 ovf = reloc_data(RELOC_OP_PREL, loc, val, 16);
401 break;
402
403 /* MOVW instruction relocations. */
404 case R_AARCH64_MOVW_UABS_G0_NC:
405 overflow_check = false;
406 fallthrough;
407 case R_AARCH64_MOVW_UABS_G0:
408 ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
409 AARCH64_INSN_IMM_MOVKZ);
410 break;
411 case R_AARCH64_MOVW_UABS_G1_NC:
412 overflow_check = false;
413 fallthrough;
414 case R_AARCH64_MOVW_UABS_G1:
415 ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
416 AARCH64_INSN_IMM_MOVKZ);
417 break;
418 case R_AARCH64_MOVW_UABS_G2_NC:
419 overflow_check = false;
420 fallthrough;
421 case R_AARCH64_MOVW_UABS_G2:
422 ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
423 AARCH64_INSN_IMM_MOVKZ);
424 break;
425 case R_AARCH64_MOVW_UABS_G3:
426 /* We're using the top bits so we can't overflow. */
427 overflow_check = false;
428 ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 48,
429 AARCH64_INSN_IMM_MOVKZ);
430 break;
431 case R_AARCH64_MOVW_SABS_G0:
432 ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
433 AARCH64_INSN_IMM_MOVNZ);
434 break;
435 case R_AARCH64_MOVW_SABS_G1:
436 ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
437 AARCH64_INSN_IMM_MOVNZ);
438 break;
439 case R_AARCH64_MOVW_SABS_G2:
440 ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
441 AARCH64_INSN_IMM_MOVNZ);
442 break;
443 case R_AARCH64_MOVW_PREL_G0_NC:
444 overflow_check = false;
445 ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
446 AARCH64_INSN_IMM_MOVKZ);
447 break;
448 case R_AARCH64_MOVW_PREL_G0:
449 ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
450 AARCH64_INSN_IMM_MOVNZ);
451 break;
452 case R_AARCH64_MOVW_PREL_G1_NC:
453 overflow_check = false;
454 ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
455 AARCH64_INSN_IMM_MOVKZ);
456 break;
457 case R_AARCH64_MOVW_PREL_G1:
458 ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
459 AARCH64_INSN_IMM_MOVNZ);
460 break;
461 case R_AARCH64_MOVW_PREL_G2_NC:
462 overflow_check = false;
463 ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
464 AARCH64_INSN_IMM_MOVKZ);
465 break;
466 case R_AARCH64_MOVW_PREL_G2:
467 ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
468 AARCH64_INSN_IMM_MOVNZ);
469 break;
470 case R_AARCH64_MOVW_PREL_G3:
471 /* We're using the top bits so we can't overflow. */
472 overflow_check = false;
473 ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 48,
474 AARCH64_INSN_IMM_MOVNZ);
475 break;
476
477 /* Immediate instruction relocations. */
478 case R_AARCH64_LD_PREL_LO19:
479 ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
480 AARCH64_INSN_IMM_19);
481 break;
482 case R_AARCH64_ADR_PREL_LO21:
483 ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 0, 21,
484 AARCH64_INSN_IMM_ADR);
485 break;
486 case R_AARCH64_ADR_PREL_PG_HI21_NC:
487 overflow_check = false;
488 fallthrough;
489 case R_AARCH64_ADR_PREL_PG_HI21:
490 ovf = reloc_insn_adrp(me, sechdrs, loc, val);
491 if (ovf && ovf != -ERANGE)
492 return ovf;
493 break;
494 case R_AARCH64_ADD_ABS_LO12_NC:
495 case R_AARCH64_LDST8_ABS_LO12_NC:
496 overflow_check = false;
497 ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 0, 12,
498 AARCH64_INSN_IMM_12);
499 break;
500 case R_AARCH64_LDST16_ABS_LO12_NC:
501 overflow_check = false;
502 ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 1, 11,
503 AARCH64_INSN_IMM_12);
504 break;
505 case R_AARCH64_LDST32_ABS_LO12_NC:
506 overflow_check = false;
507 ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 2, 10,
508 AARCH64_INSN_IMM_12);
509 break;
510 case R_AARCH64_LDST64_ABS_LO12_NC:
511 overflow_check = false;
512 ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 3, 9,
513 AARCH64_INSN_IMM_12);
514 break;
515 case R_AARCH64_LDST128_ABS_LO12_NC:
516 overflow_check = false;
517 ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 4, 8,
518 AARCH64_INSN_IMM_12);
519 break;
520 case R_AARCH64_TSTBR14:
521 ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 14,
522 AARCH64_INSN_IMM_14);
523 break;
524 case R_AARCH64_CONDBR19:
525 ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
526 AARCH64_INSN_IMM_19);
527 break;
528 case R_AARCH64_JUMP26:
529 case R_AARCH64_CALL26:
530 ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26,
531 AARCH64_INSN_IMM_26);
532 if (ovf == -ERANGE) {
533 val = module_emit_plt_entry(me, sechdrs, loc, &rel[i], sym);
534 if (!val)
535 return -ENOEXEC;
536 ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2,
537 26, AARCH64_INSN_IMM_26);
538 }
539 break;
540
541 default:
542 pr_err("module %s: unsupported RELA relocation: %llu\n",
543 me->name, ELF64_R_TYPE(rel[i].r_info));
544 return -ENOEXEC;
545 }
546
547 if (overflow_check && ovf == -ERANGE)
548 goto overflow;
549
550 }
551
552 return 0;
553
554 overflow:
555 pr_err("module %s: overflow in relocation type %d val %Lx\n",
556 me->name, (int)ELF64_R_TYPE(rel[i].r_info), val);
557 return -ENOEXEC;
558 }
559
__init_plt(struct plt_entry * plt,unsigned long addr)560 static inline void __init_plt(struct plt_entry *plt, unsigned long addr)
561 {
562 *plt = get_plt_entry(addr, plt);
563 }
564
module_init_ftrace_plt(const Elf_Ehdr * hdr,const Elf_Shdr * sechdrs,struct module * mod)565 static int module_init_ftrace_plt(const Elf_Ehdr *hdr,
566 const Elf_Shdr *sechdrs,
567 struct module *mod)
568 {
569 #if defined(CONFIG_DYNAMIC_FTRACE)
570 const Elf_Shdr *s;
571 struct plt_entry *plts;
572
573 s = find_section(hdr, sechdrs, ".text.ftrace_trampoline");
574 if (!s)
575 return -ENOEXEC;
576
577 plts = (void *)s->sh_addr;
578
579 __init_plt(&plts[FTRACE_PLT_IDX], FTRACE_ADDR);
580
581 mod->arch.ftrace_trampolines = plts;
582 #endif
583 return 0;
584 }
585
module_finalize(const Elf_Ehdr * hdr,const Elf_Shdr * sechdrs,struct module * me)586 int module_finalize(const Elf_Ehdr *hdr,
587 const Elf_Shdr *sechdrs,
588 struct module *me)
589 {
590 const Elf_Shdr *s;
591 s = find_section(hdr, sechdrs, ".altinstructions");
592 if (s)
593 apply_alternatives_module((void *)s->sh_addr, s->sh_size);
594
595 if (scs_is_dynamic()) {
596 s = find_section(hdr, sechdrs, ".init.eh_frame");
597 if (s)
598 scs_patch((void *)s->sh_addr, s->sh_size);
599 }
600
601 return module_init_ftrace_plt(hdr, sechdrs, me);
602 }
603