Vegard Nossum | dfec072 | 2008-04-04 00:51:41 +0200 | [diff] [blame^] | 1 | /** |
| 2 | * kmemcheck - a heavyweight memory checker for the linux kernel |
| 3 | * Copyright (C) 2007, 2008 Vegard Nossum <vegardno@ifi.uio.no> |
| 4 | * (With a lot of help from Ingo Molnar and Pekka Enberg.) |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License (version 2) as |
| 8 | * published by the Free Software Foundation. |
| 9 | */ |
| 10 | |
| 11 | #include <linux/init.h> |
| 12 | #include <linux/interrupt.h> |
| 13 | #include <linux/kallsyms.h> |
| 14 | #include <linux/kernel.h> |
| 15 | #include <linux/kmemcheck.h> |
| 16 | #include <linux/mm.h> |
| 17 | #include <linux/module.h> |
| 18 | #include <linux/page-flags.h> |
| 19 | #include <linux/percpu.h> |
| 20 | #include <linux/ptrace.h> |
| 21 | #include <linux/string.h> |
| 22 | #include <linux/types.h> |
| 23 | |
| 24 | #include <asm/cacheflush.h> |
| 25 | #include <asm/kmemcheck.h> |
| 26 | #include <asm/pgtable.h> |
| 27 | #include <asm/tlbflush.h> |
| 28 | |
| 29 | #include "error.h" |
| 30 | #include "opcode.h" |
| 31 | #include "pte.h" |
| 32 | #include "shadow.h" |
| 33 | |
| 34 | #ifdef CONFIG_KMEMCHECK_DISABLED_BY_DEFAULT |
| 35 | # define KMEMCHECK_ENABLED 0 |
| 36 | #endif |
| 37 | |
| 38 | #ifdef CONFIG_KMEMCHECK_ENABLED_BY_DEFAULT |
| 39 | # define KMEMCHECK_ENABLED 1 |
| 40 | #endif |
| 41 | |
| 42 | #ifdef CONFIG_KMEMCHECK_ONESHOT_BY_DEFAULT |
| 43 | # define KMEMCHECK_ENABLED 2 |
| 44 | #endif |
| 45 | |
| 46 | int kmemcheck_enabled = KMEMCHECK_ENABLED; |
| 47 | |
| 48 | int __init kmemcheck_init(void) |
| 49 | { |
| 50 | printk(KERN_INFO "kmemcheck: \"Bugs, beware!\"\n"); |
| 51 | |
| 52 | #ifdef CONFIG_SMP |
| 53 | /* |
| 54 | * Limit SMP to use a single CPU. We rely on the fact that this code |
| 55 | * runs before SMP is set up. |
| 56 | */ |
| 57 | if (setup_max_cpus > 1) { |
| 58 | printk(KERN_INFO |
| 59 | "kmemcheck: Limiting number of CPUs to 1.\n"); |
| 60 | setup_max_cpus = 1; |
| 61 | } |
| 62 | #endif |
| 63 | |
| 64 | return 0; |
| 65 | } |
| 66 | |
| 67 | early_initcall(kmemcheck_init); |
| 68 | |
| 69 | #ifdef CONFIG_KMEMCHECK_DISABLED_BY_DEFAULT |
| 70 | int kmemcheck_enabled = 0; |
| 71 | #endif |
| 72 | |
| 73 | #ifdef CONFIG_KMEMCHECK_ENABLED_BY_DEFAULT |
| 74 | int kmemcheck_enabled = 1; |
| 75 | #endif |
| 76 | |
| 77 | #ifdef CONFIG_KMEMCHECK_ONESHOT_BY_DEFAULT |
| 78 | int kmemcheck_enabled = 2; |
| 79 | #endif |
| 80 | |
| 81 | /* |
| 82 | * We need to parse the kmemcheck= option before any memory is allocated. |
| 83 | */ |
| 84 | static int __init param_kmemcheck(char *str) |
| 85 | { |
| 86 | if (!str) |
| 87 | return -EINVAL; |
| 88 | |
| 89 | sscanf(str, "%d", &kmemcheck_enabled); |
| 90 | return 0; |
| 91 | } |
| 92 | |
| 93 | early_param("kmemcheck", param_kmemcheck); |
| 94 | |
| 95 | int kmemcheck_show_addr(unsigned long address) |
| 96 | { |
| 97 | pte_t *pte; |
| 98 | |
| 99 | pte = kmemcheck_pte_lookup(address); |
| 100 | if (!pte) |
| 101 | return 0; |
| 102 | |
| 103 | set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT)); |
| 104 | __flush_tlb_one(address); |
| 105 | return 1; |
| 106 | } |
| 107 | |
| 108 | int kmemcheck_hide_addr(unsigned long address) |
| 109 | { |
| 110 | pte_t *pte; |
| 111 | |
| 112 | pte = kmemcheck_pte_lookup(address); |
| 113 | if (!pte) |
| 114 | return 0; |
| 115 | |
| 116 | set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT)); |
| 117 | __flush_tlb_one(address); |
| 118 | return 1; |
| 119 | } |
| 120 | |
| 121 | struct kmemcheck_context { |
| 122 | bool busy; |
| 123 | int balance; |
| 124 | |
| 125 | /* |
| 126 | * There can be at most two memory operands to an instruction, but |
| 127 | * each address can cross a page boundary -- so we may need up to |
| 128 | * four addresses that must be hidden/revealed for each fault. |
| 129 | */ |
| 130 | unsigned long addr[4]; |
| 131 | unsigned long n_addrs; |
| 132 | unsigned long flags; |
| 133 | |
| 134 | /* Data size of the instruction that caused a fault. */ |
| 135 | unsigned int size; |
| 136 | }; |
| 137 | |
| 138 | static DEFINE_PER_CPU(struct kmemcheck_context, kmemcheck_context); |
| 139 | |
| 140 | bool kmemcheck_active(struct pt_regs *regs) |
| 141 | { |
| 142 | struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context); |
| 143 | |
| 144 | return data->balance > 0; |
| 145 | } |
| 146 | |
| 147 | /* Save an address that needs to be shown/hidden */ |
| 148 | static void kmemcheck_save_addr(unsigned long addr) |
| 149 | { |
| 150 | struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context); |
| 151 | |
| 152 | BUG_ON(data->n_addrs >= ARRAY_SIZE(data->addr)); |
| 153 | data->addr[data->n_addrs++] = addr; |
| 154 | } |
| 155 | |
| 156 | static unsigned int kmemcheck_show_all(void) |
| 157 | { |
| 158 | struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context); |
| 159 | unsigned int i; |
| 160 | unsigned int n; |
| 161 | |
| 162 | n = 0; |
| 163 | for (i = 0; i < data->n_addrs; ++i) |
| 164 | n += kmemcheck_show_addr(data->addr[i]); |
| 165 | |
| 166 | return n; |
| 167 | } |
| 168 | |
| 169 | static unsigned int kmemcheck_hide_all(void) |
| 170 | { |
| 171 | struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context); |
| 172 | unsigned int i; |
| 173 | unsigned int n; |
| 174 | |
| 175 | n = 0; |
| 176 | for (i = 0; i < data->n_addrs; ++i) |
| 177 | n += kmemcheck_hide_addr(data->addr[i]); |
| 178 | |
| 179 | return n; |
| 180 | } |
| 181 | |
| 182 | /* |
| 183 | * Called from the #PF handler. |
| 184 | */ |
| 185 | void kmemcheck_show(struct pt_regs *regs) |
| 186 | { |
| 187 | struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context); |
| 188 | |
| 189 | BUG_ON(!irqs_disabled()); |
| 190 | |
| 191 | if (unlikely(data->balance != 0)) { |
| 192 | kmemcheck_show_all(); |
| 193 | kmemcheck_error_save_bug(regs); |
| 194 | data->balance = 0; |
| 195 | return; |
| 196 | } |
| 197 | |
| 198 | /* |
| 199 | * None of the addresses actually belonged to kmemcheck. Note that |
| 200 | * this is not an error. |
| 201 | */ |
| 202 | if (kmemcheck_show_all() == 0) |
| 203 | return; |
| 204 | |
| 205 | ++data->balance; |
| 206 | |
| 207 | /* |
| 208 | * The IF needs to be cleared as well, so that the faulting |
| 209 | * instruction can run "uninterrupted". Otherwise, we might take |
| 210 | * an interrupt and start executing that before we've had a chance |
| 211 | * to hide the page again. |
| 212 | * |
| 213 | * NOTE: In the rare case of multiple faults, we must not override |
| 214 | * the original flags: |
| 215 | */ |
| 216 | if (!(regs->flags & X86_EFLAGS_TF)) |
| 217 | data->flags = regs->flags; |
| 218 | |
| 219 | regs->flags |= X86_EFLAGS_TF; |
| 220 | regs->flags &= ~X86_EFLAGS_IF; |
| 221 | } |
| 222 | |
| 223 | /* |
| 224 | * Called from the #DB handler. |
| 225 | */ |
| 226 | void kmemcheck_hide(struct pt_regs *regs) |
| 227 | { |
| 228 | struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context); |
| 229 | int n; |
| 230 | |
| 231 | BUG_ON(!irqs_disabled()); |
| 232 | |
| 233 | if (data->balance == 0) |
| 234 | return; |
| 235 | |
| 236 | if (unlikely(data->balance != 1)) { |
| 237 | kmemcheck_show_all(); |
| 238 | kmemcheck_error_save_bug(regs); |
| 239 | data->n_addrs = 0; |
| 240 | data->balance = 0; |
| 241 | |
| 242 | if (!(data->flags & X86_EFLAGS_TF)) |
| 243 | regs->flags &= ~X86_EFLAGS_TF; |
| 244 | if (data->flags & X86_EFLAGS_IF) |
| 245 | regs->flags |= X86_EFLAGS_IF; |
| 246 | return; |
| 247 | } |
| 248 | |
| 249 | if (kmemcheck_enabled) |
| 250 | n = kmemcheck_hide_all(); |
| 251 | else |
| 252 | n = kmemcheck_show_all(); |
| 253 | |
| 254 | if (n == 0) |
| 255 | return; |
| 256 | |
| 257 | --data->balance; |
| 258 | |
| 259 | data->n_addrs = 0; |
| 260 | |
| 261 | if (!(data->flags & X86_EFLAGS_TF)) |
| 262 | regs->flags &= ~X86_EFLAGS_TF; |
| 263 | if (data->flags & X86_EFLAGS_IF) |
| 264 | regs->flags |= X86_EFLAGS_IF; |
| 265 | } |
| 266 | |
| 267 | void kmemcheck_show_pages(struct page *p, unsigned int n) |
| 268 | { |
| 269 | unsigned int i; |
| 270 | |
| 271 | for (i = 0; i < n; ++i) { |
| 272 | unsigned long address; |
| 273 | pte_t *pte; |
| 274 | unsigned int level; |
| 275 | |
| 276 | address = (unsigned long) page_address(&p[i]); |
| 277 | pte = lookup_address(address, &level); |
| 278 | BUG_ON(!pte); |
| 279 | BUG_ON(level != PG_LEVEL_4K); |
| 280 | |
| 281 | set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT)); |
| 282 | set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_HIDDEN)); |
| 283 | __flush_tlb_one(address); |
| 284 | } |
| 285 | } |
| 286 | |
| 287 | bool kmemcheck_page_is_tracked(struct page *p) |
| 288 | { |
| 289 | /* This will also check the "hidden" flag of the PTE. */ |
| 290 | return kmemcheck_pte_lookup((unsigned long) page_address(p)); |
| 291 | } |
| 292 | |
| 293 | void kmemcheck_hide_pages(struct page *p, unsigned int n) |
| 294 | { |
| 295 | unsigned int i; |
| 296 | |
| 297 | for (i = 0; i < n; ++i) { |
| 298 | unsigned long address; |
| 299 | pte_t *pte; |
| 300 | unsigned int level; |
| 301 | |
| 302 | address = (unsigned long) page_address(&p[i]); |
| 303 | pte = lookup_address(address, &level); |
| 304 | BUG_ON(!pte); |
| 305 | BUG_ON(level != PG_LEVEL_4K); |
| 306 | |
| 307 | set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT)); |
| 308 | set_pte(pte, __pte(pte_val(*pte) | _PAGE_HIDDEN)); |
| 309 | __flush_tlb_one(address); |
| 310 | } |
| 311 | } |
| 312 | |
| 313 | /* Access may NOT cross page boundary */ |
| 314 | static void kmemcheck_read_strict(struct pt_regs *regs, |
| 315 | unsigned long addr, unsigned int size) |
| 316 | { |
| 317 | void *shadow; |
| 318 | enum kmemcheck_shadow status; |
| 319 | |
| 320 | shadow = kmemcheck_shadow_lookup(addr); |
| 321 | if (!shadow) |
| 322 | return; |
| 323 | |
| 324 | kmemcheck_save_addr(addr); |
| 325 | status = kmemcheck_shadow_test(shadow, size); |
| 326 | if (status == KMEMCHECK_SHADOW_INITIALIZED) |
| 327 | return; |
| 328 | |
| 329 | if (kmemcheck_enabled) |
| 330 | kmemcheck_error_save(status, addr, size, regs); |
| 331 | |
| 332 | if (kmemcheck_enabled == 2) |
| 333 | kmemcheck_enabled = 0; |
| 334 | |
| 335 | /* Don't warn about it again. */ |
| 336 | kmemcheck_shadow_set(shadow, size); |
| 337 | } |
| 338 | |
| 339 | /* Access may cross page boundary */ |
| 340 | static void kmemcheck_read(struct pt_regs *regs, |
| 341 | unsigned long addr, unsigned int size) |
| 342 | { |
| 343 | unsigned long page = addr & PAGE_MASK; |
| 344 | unsigned long next_addr = addr + size - 1; |
| 345 | unsigned long next_page = next_addr & PAGE_MASK; |
| 346 | |
| 347 | if (likely(page == next_page)) { |
| 348 | kmemcheck_read_strict(regs, addr, size); |
| 349 | return; |
| 350 | } |
| 351 | |
| 352 | /* |
| 353 | * What we do is basically to split the access across the |
| 354 | * two pages and handle each part separately. Yes, this means |
| 355 | * that we may now see reads that are 3 + 5 bytes, for |
| 356 | * example (and if both are uninitialized, there will be two |
| 357 | * reports), but it makes the code a lot simpler. |
| 358 | */ |
| 359 | kmemcheck_read_strict(regs, addr, next_page - addr); |
| 360 | kmemcheck_read_strict(regs, next_page, next_addr - next_page); |
| 361 | } |
| 362 | |
| 363 | static void kmemcheck_write_strict(struct pt_regs *regs, |
| 364 | unsigned long addr, unsigned int size) |
| 365 | { |
| 366 | void *shadow; |
| 367 | |
| 368 | shadow = kmemcheck_shadow_lookup(addr); |
| 369 | if (!shadow) |
| 370 | return; |
| 371 | |
| 372 | kmemcheck_save_addr(addr); |
| 373 | kmemcheck_shadow_set(shadow, size); |
| 374 | } |
| 375 | |
| 376 | static void kmemcheck_write(struct pt_regs *regs, |
| 377 | unsigned long addr, unsigned int size) |
| 378 | { |
| 379 | unsigned long page = addr & PAGE_MASK; |
| 380 | unsigned long next_addr = addr + size - 1; |
| 381 | unsigned long next_page = next_addr & PAGE_MASK; |
| 382 | |
| 383 | if (likely(page == next_page)) { |
| 384 | kmemcheck_write_strict(regs, addr, size); |
| 385 | return; |
| 386 | } |
| 387 | |
| 388 | /* See comment in kmemcheck_read(). */ |
| 389 | kmemcheck_write_strict(regs, addr, next_page - addr); |
| 390 | kmemcheck_write_strict(regs, next_page, next_addr - next_page); |
| 391 | } |
| 392 | |
| 393 | /* |
| 394 | * Copying is hard. We have two addresses, each of which may be split across |
| 395 | * a page (and each page will have different shadow addresses). |
| 396 | */ |
| 397 | static void kmemcheck_copy(struct pt_regs *regs, |
| 398 | unsigned long src_addr, unsigned long dst_addr, unsigned int size) |
| 399 | { |
| 400 | uint8_t shadow[8]; |
| 401 | enum kmemcheck_shadow status; |
| 402 | |
| 403 | unsigned long page; |
| 404 | unsigned long next_addr; |
| 405 | unsigned long next_page; |
| 406 | |
| 407 | uint8_t *x; |
| 408 | unsigned int i; |
| 409 | unsigned int n; |
| 410 | |
| 411 | BUG_ON(size > sizeof(shadow)); |
| 412 | |
| 413 | page = src_addr & PAGE_MASK; |
| 414 | next_addr = src_addr + size - 1; |
| 415 | next_page = next_addr & PAGE_MASK; |
| 416 | |
| 417 | if (likely(page == next_page)) { |
| 418 | /* Same page */ |
| 419 | x = kmemcheck_shadow_lookup(src_addr); |
| 420 | if (x) { |
| 421 | kmemcheck_save_addr(src_addr); |
| 422 | for (i = 0; i < size; ++i) |
| 423 | shadow[i] = x[i]; |
| 424 | } else { |
| 425 | for (i = 0; i < size; ++i) |
| 426 | shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; |
| 427 | } |
| 428 | } else { |
| 429 | n = next_page - src_addr; |
| 430 | BUG_ON(n > sizeof(shadow)); |
| 431 | |
| 432 | /* First page */ |
| 433 | x = kmemcheck_shadow_lookup(src_addr); |
| 434 | if (x) { |
| 435 | kmemcheck_save_addr(src_addr); |
| 436 | for (i = 0; i < n; ++i) |
| 437 | shadow[i] = x[i]; |
| 438 | } else { |
| 439 | /* Not tracked */ |
| 440 | for (i = 0; i < n; ++i) |
| 441 | shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; |
| 442 | } |
| 443 | |
| 444 | /* Second page */ |
| 445 | x = kmemcheck_shadow_lookup(next_page); |
| 446 | if (x) { |
| 447 | kmemcheck_save_addr(next_page); |
| 448 | for (i = n; i < size; ++i) |
| 449 | shadow[i] = x[i - n]; |
| 450 | } else { |
| 451 | /* Not tracked */ |
| 452 | for (i = n; i < size; ++i) |
| 453 | shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; |
| 454 | } |
| 455 | } |
| 456 | |
| 457 | page = dst_addr & PAGE_MASK; |
| 458 | next_addr = dst_addr + size - 1; |
| 459 | next_page = next_addr & PAGE_MASK; |
| 460 | |
| 461 | if (likely(page == next_page)) { |
| 462 | /* Same page */ |
| 463 | x = kmemcheck_shadow_lookup(dst_addr); |
| 464 | if (x) { |
| 465 | kmemcheck_save_addr(dst_addr); |
| 466 | for (i = 0; i < size; ++i) { |
| 467 | x[i] = shadow[i]; |
| 468 | shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; |
| 469 | } |
| 470 | } |
| 471 | } else { |
| 472 | n = next_page - dst_addr; |
| 473 | BUG_ON(n > sizeof(shadow)); |
| 474 | |
| 475 | /* First page */ |
| 476 | x = kmemcheck_shadow_lookup(dst_addr); |
| 477 | if (x) { |
| 478 | kmemcheck_save_addr(dst_addr); |
| 479 | for (i = 0; i < n; ++i) { |
| 480 | x[i] = shadow[i]; |
| 481 | shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; |
| 482 | } |
| 483 | } |
| 484 | |
| 485 | /* Second page */ |
| 486 | x = kmemcheck_shadow_lookup(next_page); |
| 487 | if (x) { |
| 488 | kmemcheck_save_addr(next_page); |
| 489 | for (i = n; i < size; ++i) { |
| 490 | x[i - n] = shadow[i]; |
| 491 | shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; |
| 492 | } |
| 493 | } |
| 494 | } |
| 495 | |
| 496 | status = kmemcheck_shadow_test(shadow, size); |
| 497 | if (status == KMEMCHECK_SHADOW_INITIALIZED) |
| 498 | return; |
| 499 | |
| 500 | if (kmemcheck_enabled) |
| 501 | kmemcheck_error_save(status, src_addr, size, regs); |
| 502 | |
| 503 | if (kmemcheck_enabled == 2) |
| 504 | kmemcheck_enabled = 0; |
| 505 | } |
| 506 | |
| 507 | enum kmemcheck_method { |
| 508 | KMEMCHECK_READ, |
| 509 | KMEMCHECK_WRITE, |
| 510 | }; |
| 511 | |
| 512 | static void kmemcheck_access(struct pt_regs *regs, |
| 513 | unsigned long fallback_address, enum kmemcheck_method fallback_method) |
| 514 | { |
| 515 | const uint8_t *insn; |
| 516 | const uint8_t *insn_primary; |
| 517 | unsigned int size; |
| 518 | |
| 519 | struct kmemcheck_context *data = &__get_cpu_var(kmemcheck_context); |
| 520 | |
| 521 | /* Recursive fault -- ouch. */ |
| 522 | if (data->busy) { |
| 523 | kmemcheck_show_addr(fallback_address); |
| 524 | kmemcheck_error_save_bug(regs); |
| 525 | return; |
| 526 | } |
| 527 | |
| 528 | data->busy = true; |
| 529 | |
| 530 | insn = (const uint8_t *) regs->ip; |
| 531 | insn_primary = kmemcheck_opcode_get_primary(insn); |
| 532 | |
| 533 | kmemcheck_opcode_decode(insn, &size); |
| 534 | |
| 535 | switch (insn_primary[0]) { |
| 536 | #ifdef CONFIG_KMEMCHECK_BITOPS_OK |
| 537 | /* AND, OR, XOR */ |
| 538 | /* |
| 539 | * Unfortunately, these instructions have to be excluded from |
| 540 | * our regular checking since they access only some (and not |
| 541 | * all) bits. This clears out "bogus" bitfield-access warnings. |
| 542 | */ |
| 543 | case 0x80: |
| 544 | case 0x81: |
| 545 | case 0x82: |
| 546 | case 0x83: |
| 547 | switch ((insn_primary[1] >> 3) & 7) { |
| 548 | /* OR */ |
| 549 | case 1: |
| 550 | /* AND */ |
| 551 | case 4: |
| 552 | /* XOR */ |
| 553 | case 6: |
| 554 | kmemcheck_write(regs, fallback_address, size); |
| 555 | goto out; |
| 556 | |
| 557 | /* ADD */ |
| 558 | case 0: |
| 559 | /* ADC */ |
| 560 | case 2: |
| 561 | /* SBB */ |
| 562 | case 3: |
| 563 | /* SUB */ |
| 564 | case 5: |
| 565 | /* CMP */ |
| 566 | case 7: |
| 567 | break; |
| 568 | } |
| 569 | break; |
| 570 | #endif |
| 571 | |
| 572 | /* MOVS, MOVSB, MOVSW, MOVSD */ |
| 573 | case 0xa4: |
| 574 | case 0xa5: |
| 575 | /* |
| 576 | * These instructions are special because they take two |
| 577 | * addresses, but we only get one page fault. |
| 578 | */ |
| 579 | kmemcheck_copy(regs, regs->si, regs->di, size); |
| 580 | goto out; |
| 581 | |
| 582 | /* CMPS, CMPSB, CMPSW, CMPSD */ |
| 583 | case 0xa6: |
| 584 | case 0xa7: |
| 585 | kmemcheck_read(regs, regs->si, size); |
| 586 | kmemcheck_read(regs, regs->di, size); |
| 587 | goto out; |
| 588 | } |
| 589 | |
| 590 | /* |
| 591 | * If the opcode isn't special in any way, we use the data from the |
| 592 | * page fault handler to determine the address and type of memory |
| 593 | * access. |
| 594 | */ |
| 595 | switch (fallback_method) { |
| 596 | case KMEMCHECK_READ: |
| 597 | kmemcheck_read(regs, fallback_address, size); |
| 598 | goto out; |
| 599 | case KMEMCHECK_WRITE: |
| 600 | kmemcheck_write(regs, fallback_address, size); |
| 601 | goto out; |
| 602 | } |
| 603 | |
| 604 | out: |
| 605 | data->busy = false; |
| 606 | } |
| 607 | |
| 608 | bool kmemcheck_fault(struct pt_regs *regs, unsigned long address, |
| 609 | unsigned long error_code) |
| 610 | { |
| 611 | pte_t *pte; |
| 612 | unsigned int level; |
| 613 | |
| 614 | /* |
| 615 | * XXX: Is it safe to assume that memory accesses from virtual 86 |
| 616 | * mode or non-kernel code segments will _never_ access kernel |
| 617 | * memory (e.g. tracked pages)? For now, we need this to avoid |
| 618 | * invoking kmemcheck for PnP BIOS calls. |
| 619 | */ |
| 620 | if (regs->flags & X86_VM_MASK) |
| 621 | return false; |
| 622 | if (regs->cs != __KERNEL_CS) |
| 623 | return false; |
| 624 | |
| 625 | pte = lookup_address(address, &level); |
| 626 | if (!pte) |
| 627 | return false; |
| 628 | if (level != PG_LEVEL_4K) |
| 629 | return false; |
| 630 | if (!pte_hidden(*pte)) |
| 631 | return false; |
| 632 | |
| 633 | if (error_code & 2) |
| 634 | kmemcheck_access(regs, address, KMEMCHECK_WRITE); |
| 635 | else |
| 636 | kmemcheck_access(regs, address, KMEMCHECK_READ); |
| 637 | |
| 638 | kmemcheck_show(regs); |
| 639 | return true; |
| 640 | } |
| 641 | |
| 642 | bool kmemcheck_trap(struct pt_regs *regs) |
| 643 | { |
| 644 | if (!kmemcheck_active(regs)) |
| 645 | return false; |
| 646 | |
| 647 | /* We're done. */ |
| 648 | kmemcheck_hide(regs); |
| 649 | return true; |
| 650 | } |