| 1 | /* |
| 2 | * Copyright (C) 1995 Linus Torvalds |
| 3 | * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. |
| 4 | * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar |
| 5 | */ |
| 6 | #include <linux/sched.h> /* test_thread_flag(), ... */ |
| 7 | #include <linux/kdebug.h> /* oops_begin/end, ... */ |
| 8 | #include <linux/module.h> /* search_exception_table */ |
| 9 | #include <linux/bootmem.h> /* max_low_pfn */ |
| 10 | #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */ |
| 11 | #include <linux/mmiotrace.h> /* kmmio_handler, ... */ |
| 12 | #include <linux/perf_event.h> /* perf_sw_event */ |
| 13 | #include <linux/hugetlb.h> /* hstate_index_to_shift */ |
| 14 | #include <linux/prefetch.h> /* prefetchw */ |
| 15 | #include <linux/context_tracking.h> /* exception_enter(), ... */ |
| 16 | #include <linux/uaccess.h> /* faulthandler_disabled() */ |
| 17 | |
| 18 | #include <asm/cpufeature.h> /* boot_cpu_has, ... */ |
| 19 | #include <asm/traps.h> /* dotraplinkage, ... */ |
| 20 | #include <asm/pgalloc.h> /* pgd_*(), ... */ |
| 21 | #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */ |
| 22 | #include <asm/fixmap.h> /* VSYSCALL_ADDR */ |
| 23 | #include <asm/vsyscall.h> /* emulate_vsyscall */ |
| 24 | #include <asm/vm86.h> /* struct vm86 */ |
| 25 | #include <asm/mmu_context.h> /* vma_pkey() */ |
| 26 | |
| 27 | #define CREATE_TRACE_POINTS |
| 28 | #include <asm/trace/exceptions.h> |
| 29 | |
| 30 | /* |
| 31 | * Page fault error code bits: |
| 32 | * |
| 33 | * bit 0 == 0: no page found 1: protection fault |
| 34 | * bit 1 == 0: read access 1: write access |
| 35 | * bit 2 == 0: kernel-mode access 1: user-mode access |
| 36 | * bit 3 == 1: use of reserved bit detected |
| 37 | * bit 4 == 1: fault was an instruction fetch |
| 38 | * bit 5 == 1: protection keys block access |
| 39 | */ |
| 40 | enum x86_pf_error_code { |
| 41 | |
| 42 | PF_PROT = 1 << 0, |
| 43 | PF_WRITE = 1 << 1, |
| 44 | PF_USER = 1 << 2, |
| 45 | PF_RSVD = 1 << 3, |
| 46 | PF_INSTR = 1 << 4, |
| 47 | PF_PK = 1 << 5, |
| 48 | }; |
| 49 | |
| 50 | /* |
| 51 | * Returns 0 if mmiotrace is disabled, or if the fault is not |
| 52 | * handled by mmiotrace: |
| 53 | */ |
| 54 | static nokprobe_inline int |
| 55 | kmmio_fault(struct pt_regs *regs, unsigned long addr) |
| 56 | { |
| 57 | if (unlikely(is_kmmio_active())) |
| 58 | if (kmmio_handler(regs, addr) == 1) |
| 59 | return -1; |
| 60 | return 0; |
| 61 | } |
| 62 | |
| 63 | static nokprobe_inline int kprobes_fault(struct pt_regs *regs) |
| 64 | { |
| 65 | int ret = 0; |
| 66 | |
| 67 | /* kprobe_running() needs smp_processor_id() */ |
| 68 | if (kprobes_built_in() && !user_mode(regs)) { |
| 69 | preempt_disable(); |
| 70 | if (kprobe_running() && kprobe_fault_handler(regs, 14)) |
| 71 | ret = 1; |
| 72 | preempt_enable(); |
| 73 | } |
| 74 | |
| 75 | return ret; |
| 76 | } |
| 77 | |
| 78 | /* |
| 79 | * Prefetch quirks: |
| 80 | * |
| 81 | * 32-bit mode: |
| 82 | * |
| 83 | * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. |
| 84 | * Check that here and ignore it. |
| 85 | * |
| 86 | * 64-bit mode: |
| 87 | * |
| 88 | * Sometimes the CPU reports invalid exceptions on prefetch. |
| 89 | * Check that here and ignore it. |
| 90 | * |
| 91 | * Opcode checker based on code by Richard Brunner. |
| 92 | */ |
| 93 | static inline int |
| 94 | check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, |
| 95 | unsigned char opcode, int *prefetch) |
| 96 | { |
| 97 | unsigned char instr_hi = opcode & 0xf0; |
| 98 | unsigned char instr_lo = opcode & 0x0f; |
| 99 | |
| 100 | switch (instr_hi) { |
| 101 | case 0x20: |
| 102 | case 0x30: |
| 103 | /* |
| 104 | * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. |
| 105 | * In X86_64 long mode, the CPU will signal invalid |
| 106 | * opcode if some of these prefixes are present so |
| 107 | * X86_64 will never get here anyway |
| 108 | */ |
| 109 | return ((instr_lo & 7) == 0x6); |
| 110 | #ifdef CONFIG_X86_64 |
| 111 | case 0x40: |
| 112 | /* |
| 113 | * In AMD64 long mode 0x40..0x4F are valid REX prefixes |
| 114 | * Need to figure out under what instruction mode the |
| 115 | * instruction was issued. Could check the LDT for lm, |
| 116 | * but for now it's good enough to assume that long |
| 117 | * mode only uses well known segments or kernel. |
| 118 | */ |
| 119 | return (!user_mode(regs) || user_64bit_mode(regs)); |
| 120 | #endif |
| 121 | case 0x60: |
| 122 | /* 0x64 thru 0x67 are valid prefixes in all modes. */ |
| 123 | return (instr_lo & 0xC) == 0x4; |
| 124 | case 0xF0: |
| 125 | /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ |
| 126 | return !instr_lo || (instr_lo>>1) == 1; |
| 127 | case 0x00: |
| 128 | /* Prefetch instruction is 0x0F0D or 0x0F18 */ |
| 129 | if (probe_kernel_address(instr, opcode)) |
| 130 | return 0; |
| 131 | |
| 132 | *prefetch = (instr_lo == 0xF) && |
| 133 | (opcode == 0x0D || opcode == 0x18); |
| 134 | return 0; |
| 135 | default: |
| 136 | return 0; |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | static int |
| 141 | is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) |
| 142 | { |
| 143 | unsigned char *max_instr; |
| 144 | unsigned char *instr; |
| 145 | int prefetch = 0; |
| 146 | |
| 147 | /* |
| 148 | * If it was a exec (instruction fetch) fault on NX page, then |
| 149 | * do not ignore the fault: |
| 150 | */ |
| 151 | if (error_code & PF_INSTR) |
| 152 | return 0; |
| 153 | |
| 154 | instr = (void *)convert_ip_to_linear(current, regs); |
| 155 | max_instr = instr + 15; |
| 156 | |
| 157 | if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) |
| 158 | return 0; |
| 159 | |
| 160 | while (instr < max_instr) { |
| 161 | unsigned char opcode; |
| 162 | |
| 163 | if (probe_kernel_address(instr, opcode)) |
| 164 | break; |
| 165 | |
| 166 | instr++; |
| 167 | |
| 168 | if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) |
| 169 | break; |
| 170 | } |
| 171 | return prefetch; |
| 172 | } |
| 173 | |
| 174 | /* |
| 175 | * A protection key fault means that the PKRU value did not allow |
| 176 | * access to some PTE. Userspace can figure out what PKRU was |
| 177 | * from the XSAVE state, and this function fills out a field in |
| 178 | * siginfo so userspace can discover which protection key was set |
| 179 | * on the PTE. |
| 180 | * |
| 181 | * If we get here, we know that the hardware signaled a PF_PK |
| 182 | * fault and that there was a VMA once we got in the fault |
| 183 | * handler. It does *not* guarantee that the VMA we find here |
| 184 | * was the one that we faulted on. |
| 185 | * |
| 186 | * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); |
| 187 | * 2. T1 : set PKRU to deny access to pkey=4, touches page |
| 188 | * 3. T1 : faults... |
| 189 | * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); |
| 190 | * 5. T1 : enters fault handler, takes mmap_sem, etc... |
| 191 | * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really |
| 192 | * faulted on a pte with its pkey=4. |
| 193 | */ |
| 194 | static void fill_sig_info_pkey(int si_code, siginfo_t *info, |
| 195 | struct vm_area_struct *vma) |
| 196 | { |
| 197 | /* This is effectively an #ifdef */ |
| 198 | if (!boot_cpu_has(X86_FEATURE_OSPKE)) |
| 199 | return; |
| 200 | |
| 201 | /* Fault not from Protection Keys: nothing to do */ |
| 202 | if (si_code != SEGV_PKUERR) |
| 203 | return; |
| 204 | /* |
| 205 | * force_sig_info_fault() is called from a number of |
| 206 | * contexts, some of which have a VMA and some of which |
| 207 | * do not. The PF_PK handing happens after we have a |
| 208 | * valid VMA, so we should never reach this without a |
| 209 | * valid VMA. |
| 210 | */ |
| 211 | if (!vma) { |
| 212 | WARN_ONCE(1, "PKU fault with no VMA passed in"); |
| 213 | info->si_pkey = 0; |
| 214 | return; |
| 215 | } |
| 216 | /* |
| 217 | * si_pkey should be thought of as a strong hint, but not |
| 218 | * absolutely guranteed to be 100% accurate because of |
| 219 | * the race explained above. |
| 220 | */ |
| 221 | info->si_pkey = vma_pkey(vma); |
| 222 | } |
| 223 | |
| 224 | static void |
| 225 | force_sig_info_fault(int si_signo, int si_code, unsigned long address, |
| 226 | struct task_struct *tsk, struct vm_area_struct *vma, |
| 227 | int fault) |
| 228 | { |
| 229 | unsigned lsb = 0; |
| 230 | siginfo_t info; |
| 231 | |
| 232 | info.si_signo = si_signo; |
| 233 | info.si_errno = 0; |
| 234 | info.si_code = si_code; |
| 235 | info.si_addr = (void __user *)address; |
| 236 | if (fault & VM_FAULT_HWPOISON_LARGE) |
| 237 | lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); |
| 238 | if (fault & VM_FAULT_HWPOISON) |
| 239 | lsb = PAGE_SHIFT; |
| 240 | info.si_addr_lsb = lsb; |
| 241 | |
| 242 | fill_sig_info_pkey(si_code, &info, vma); |
| 243 | |
| 244 | force_sig_info(si_signo, &info, tsk); |
| 245 | } |
| 246 | |
| 247 | DEFINE_SPINLOCK(pgd_lock); |
| 248 | LIST_HEAD(pgd_list); |
| 249 | |
| 250 | #ifdef CONFIG_X86_32 |
| 251 | static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) |
| 252 | { |
| 253 | unsigned index = pgd_index(address); |
| 254 | pgd_t *pgd_k; |
| 255 | pud_t *pud, *pud_k; |
| 256 | pmd_t *pmd, *pmd_k; |
| 257 | |
| 258 | pgd += index; |
| 259 | pgd_k = init_mm.pgd + index; |
| 260 | |
| 261 | if (!pgd_present(*pgd_k)) |
| 262 | return NULL; |
| 263 | |
| 264 | /* |
| 265 | * set_pgd(pgd, *pgd_k); here would be useless on PAE |
| 266 | * and redundant with the set_pmd() on non-PAE. As would |
| 267 | * set_pud. |
| 268 | */ |
| 269 | pud = pud_offset(pgd, address); |
| 270 | pud_k = pud_offset(pgd_k, address); |
| 271 | if (!pud_present(*pud_k)) |
| 272 | return NULL; |
| 273 | |
| 274 | pmd = pmd_offset(pud, address); |
| 275 | pmd_k = pmd_offset(pud_k, address); |
| 276 | if (!pmd_present(*pmd_k)) |
| 277 | return NULL; |
| 278 | |
| 279 | if (!pmd_present(*pmd)) |
| 280 | set_pmd(pmd, *pmd_k); |
| 281 | else |
| 282 | BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); |
| 283 | |
| 284 | return pmd_k; |
| 285 | } |
| 286 | |
| 287 | void vmalloc_sync_all(void) |
| 288 | { |
| 289 | unsigned long address; |
| 290 | |
| 291 | if (SHARED_KERNEL_PMD) |
| 292 | return; |
| 293 | |
| 294 | for (address = VMALLOC_START & PMD_MASK; |
| 295 | address >= TASK_SIZE && address < FIXADDR_TOP; |
| 296 | address += PMD_SIZE) { |
| 297 | struct page *page; |
| 298 | |
| 299 | spin_lock(&pgd_lock); |
| 300 | list_for_each_entry(page, &pgd_list, lru) { |
| 301 | spinlock_t *pgt_lock; |
| 302 | pmd_t *ret; |
| 303 | |
| 304 | /* the pgt_lock only for Xen */ |
| 305 | pgt_lock = &pgd_page_get_mm(page)->page_table_lock; |
| 306 | |
| 307 | spin_lock(pgt_lock); |
| 308 | ret = vmalloc_sync_one(page_address(page), address); |
| 309 | spin_unlock(pgt_lock); |
| 310 | |
| 311 | if (!ret) |
| 312 | break; |
| 313 | } |
| 314 | spin_unlock(&pgd_lock); |
| 315 | } |
| 316 | } |
| 317 | |
| 318 | /* |
| 319 | * 32-bit: |
| 320 | * |
| 321 | * Handle a fault on the vmalloc or module mapping area |
| 322 | */ |
| 323 | static noinline int vmalloc_fault(unsigned long address) |
| 324 | { |
| 325 | unsigned long pgd_paddr; |
| 326 | pmd_t *pmd_k; |
| 327 | pte_t *pte_k; |
| 328 | |
| 329 | /* Make sure we are in vmalloc area: */ |
| 330 | if (!(address >= VMALLOC_START && address < VMALLOC_END)) |
| 331 | return -1; |
| 332 | |
| 333 | WARN_ON_ONCE(in_nmi()); |
| 334 | |
| 335 | /* |
| 336 | * Synchronize this task's top level page-table |
| 337 | * with the 'reference' page table. |
| 338 | * |
| 339 | * Do _not_ use "current" here. We might be inside |
| 340 | * an interrupt in the middle of a task switch.. |
| 341 | */ |
| 342 | pgd_paddr = read_cr3(); |
| 343 | pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); |
| 344 | if (!pmd_k) |
| 345 | return -1; |
| 346 | |
| 347 | pte_k = pte_offset_kernel(pmd_k, address); |
| 348 | if (!pte_present(*pte_k)) |
| 349 | return -1; |
| 350 | |
| 351 | return 0; |
| 352 | } |
| 353 | NOKPROBE_SYMBOL(vmalloc_fault); |
| 354 | |
| 355 | /* |
| 356 | * Did it hit the DOS screen memory VA from vm86 mode? |
| 357 | */ |
| 358 | static inline void |
| 359 | check_v8086_mode(struct pt_regs *regs, unsigned long address, |
| 360 | struct task_struct *tsk) |
| 361 | { |
| 362 | #ifdef CONFIG_VM86 |
| 363 | unsigned long bit; |
| 364 | |
| 365 | if (!v8086_mode(regs) || !tsk->thread.vm86) |
| 366 | return; |
| 367 | |
| 368 | bit = (address - 0xA0000) >> PAGE_SHIFT; |
| 369 | if (bit < 32) |
| 370 | tsk->thread.vm86->screen_bitmap |= 1 << bit; |
| 371 | #endif |
| 372 | } |
| 373 | |
| 374 | static bool low_pfn(unsigned long pfn) |
| 375 | { |
| 376 | return pfn < max_low_pfn; |
| 377 | } |
| 378 | |
| 379 | static void dump_pagetable(unsigned long address) |
| 380 | { |
| 381 | pgd_t *base = __va(read_cr3()); |
| 382 | pgd_t *pgd = &base[pgd_index(address)]; |
| 383 | pmd_t *pmd; |
| 384 | pte_t *pte; |
| 385 | |
| 386 | #ifdef CONFIG_X86_PAE |
| 387 | printk("*pdpt = %016Lx ", pgd_val(*pgd)); |
| 388 | if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) |
| 389 | goto out; |
| 390 | #endif |
| 391 | pmd = pmd_offset(pud_offset(pgd, address), address); |
| 392 | printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); |
| 393 | |
| 394 | /* |
| 395 | * We must not directly access the pte in the highpte |
| 396 | * case if the page table is located in highmem. |
| 397 | * And let's rather not kmap-atomic the pte, just in case |
| 398 | * it's allocated already: |
| 399 | */ |
| 400 | if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) |
| 401 | goto out; |
| 402 | |
| 403 | pte = pte_offset_kernel(pmd, address); |
| 404 | printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); |
| 405 | out: |
| 406 | printk("\n"); |
| 407 | } |
| 408 | |
| 409 | #else /* CONFIG_X86_64: */ |
| 410 | |
| 411 | void vmalloc_sync_all(void) |
| 412 | { |
| 413 | sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END, 0); |
| 414 | } |
| 415 | |
| 416 | /* |
| 417 | * 64-bit: |
| 418 | * |
| 419 | * Handle a fault on the vmalloc area |
| 420 | * |
| 421 | * This assumes no large pages in there. |
| 422 | */ |
| 423 | static noinline int vmalloc_fault(unsigned long address) |
| 424 | { |
| 425 | pgd_t *pgd, *pgd_ref; |
| 426 | pud_t *pud, *pud_ref; |
| 427 | pmd_t *pmd, *pmd_ref; |
| 428 | pte_t *pte, *pte_ref; |
| 429 | |
| 430 | /* Make sure we are in vmalloc area: */ |
| 431 | if (!(address >= VMALLOC_START && address < VMALLOC_END)) |
| 432 | return -1; |
| 433 | |
| 434 | WARN_ON_ONCE(in_nmi()); |
| 435 | |
| 436 | /* |
| 437 | * Copy kernel mappings over when needed. This can also |
| 438 | * happen within a race in page table update. In the later |
| 439 | * case just flush: |
| 440 | */ |
| 441 | pgd = pgd_offset(current->active_mm, address); |
| 442 | pgd_ref = pgd_offset_k(address); |
| 443 | if (pgd_none(*pgd_ref)) |
| 444 | return -1; |
| 445 | |
| 446 | if (pgd_none(*pgd)) { |
| 447 | set_pgd(pgd, *pgd_ref); |
| 448 | arch_flush_lazy_mmu_mode(); |
| 449 | } else { |
| 450 | BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); |
| 451 | } |
| 452 | |
| 453 | /* |
| 454 | * Below here mismatches are bugs because these lower tables |
| 455 | * are shared: |
| 456 | */ |
| 457 | |
| 458 | pud = pud_offset(pgd, address); |
| 459 | pud_ref = pud_offset(pgd_ref, address); |
| 460 | if (pud_none(*pud_ref)) |
| 461 | return -1; |
| 462 | |
| 463 | if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref)) |
| 464 | BUG(); |
| 465 | |
| 466 | pmd = pmd_offset(pud, address); |
| 467 | pmd_ref = pmd_offset(pud_ref, address); |
| 468 | if (pmd_none(*pmd_ref)) |
| 469 | return -1; |
| 470 | |
| 471 | if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref)) |
| 472 | BUG(); |
| 473 | |
| 474 | pte_ref = pte_offset_kernel(pmd_ref, address); |
| 475 | if (!pte_present(*pte_ref)) |
| 476 | return -1; |
| 477 | |
| 478 | pte = pte_offset_kernel(pmd, address); |
| 479 | |
| 480 | /* |
| 481 | * Don't use pte_page here, because the mappings can point |
| 482 | * outside mem_map, and the NUMA hash lookup cannot handle |
| 483 | * that: |
| 484 | */ |
| 485 | if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) |
| 486 | BUG(); |
| 487 | |
| 488 | return 0; |
| 489 | } |
| 490 | NOKPROBE_SYMBOL(vmalloc_fault); |
| 491 | |
| 492 | #ifdef CONFIG_CPU_SUP_AMD |
| 493 | static const char errata93_warning[] = |
| 494 | KERN_ERR |
| 495 | "******* Your BIOS seems to not contain a fix for K8 errata #93\n" |
| 496 | "******* Working around it, but it may cause SEGVs or burn power.\n" |
| 497 | "******* Please consider a BIOS update.\n" |
| 498 | "******* Disabling USB legacy in the BIOS may also help.\n"; |
| 499 | #endif |
| 500 | |
| 501 | /* |
| 502 | * No vm86 mode in 64-bit mode: |
| 503 | */ |
| 504 | static inline void |
| 505 | check_v8086_mode(struct pt_regs *regs, unsigned long address, |
| 506 | struct task_struct *tsk) |
| 507 | { |
| 508 | } |
| 509 | |
| 510 | static int bad_address(void *p) |
| 511 | { |
| 512 | unsigned long dummy; |
| 513 | |
| 514 | return probe_kernel_address((unsigned long *)p, dummy); |
| 515 | } |
| 516 | |
| 517 | static void dump_pagetable(unsigned long address) |
| 518 | { |
| 519 | pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK); |
| 520 | pgd_t *pgd = base + pgd_index(address); |
| 521 | pud_t *pud; |
| 522 | pmd_t *pmd; |
| 523 | pte_t *pte; |
| 524 | |
| 525 | if (bad_address(pgd)) |
| 526 | goto bad; |
| 527 | |
| 528 | printk("PGD %lx ", pgd_val(*pgd)); |
| 529 | |
| 530 | if (!pgd_present(*pgd)) |
| 531 | goto out; |
| 532 | |
| 533 | pud = pud_offset(pgd, address); |
| 534 | if (bad_address(pud)) |
| 535 | goto bad; |
| 536 | |
| 537 | printk("PUD %lx ", pud_val(*pud)); |
| 538 | if (!pud_present(*pud) || pud_large(*pud)) |
| 539 | goto out; |
| 540 | |
| 541 | pmd = pmd_offset(pud, address); |
| 542 | if (bad_address(pmd)) |
| 543 | goto bad; |
| 544 | |
| 545 | printk("PMD %lx ", pmd_val(*pmd)); |
| 546 | if (!pmd_present(*pmd) || pmd_large(*pmd)) |
| 547 | goto out; |
| 548 | |
| 549 | pte = pte_offset_kernel(pmd, address); |
| 550 | if (bad_address(pte)) |
| 551 | goto bad; |
| 552 | |
| 553 | printk("PTE %lx", pte_val(*pte)); |
| 554 | out: |
| 555 | printk("\n"); |
| 556 | return; |
| 557 | bad: |
| 558 | printk("BAD\n"); |
| 559 | } |
| 560 | |
| 561 | #endif /* CONFIG_X86_64 */ |
| 562 | |
| 563 | /* |
| 564 | * Workaround for K8 erratum #93 & buggy BIOS. |
| 565 | * |
| 566 | * BIOS SMM functions are required to use a specific workaround |
| 567 | * to avoid corruption of the 64bit RIP register on C stepping K8. |
| 568 | * |
| 569 | * A lot of BIOS that didn't get tested properly miss this. |
| 570 | * |
| 571 | * The OS sees this as a page fault with the upper 32bits of RIP cleared. |
| 572 | * Try to work around it here. |
| 573 | * |
| 574 | * Note we only handle faults in kernel here. |
| 575 | * Does nothing on 32-bit. |
| 576 | */ |
| 577 | static int is_errata93(struct pt_regs *regs, unsigned long address) |
| 578 | { |
| 579 | #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) |
| 580 | if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD |
| 581 | || boot_cpu_data.x86 != 0xf) |
| 582 | return 0; |
| 583 | |
| 584 | if (address != regs->ip) |
| 585 | return 0; |
| 586 | |
| 587 | if ((address >> 32) != 0) |
| 588 | return 0; |
| 589 | |
| 590 | address |= 0xffffffffUL << 32; |
| 591 | if ((address >= (u64)_stext && address <= (u64)_etext) || |
| 592 | (address >= MODULES_VADDR && address <= MODULES_END)) { |
| 593 | printk_once(errata93_warning); |
| 594 | regs->ip = address; |
| 595 | return 1; |
| 596 | } |
| 597 | #endif |
| 598 | return 0; |
| 599 | } |
| 600 | |
| 601 | /* |
| 602 | * Work around K8 erratum #100 K8 in compat mode occasionally jumps |
| 603 | * to illegal addresses >4GB. |
| 604 | * |
| 605 | * We catch this in the page fault handler because these addresses |
| 606 | * are not reachable. Just detect this case and return. Any code |
| 607 | * segment in LDT is compatibility mode. |
| 608 | */ |
| 609 | static int is_errata100(struct pt_regs *regs, unsigned long address) |
| 610 | { |
| 611 | #ifdef CONFIG_X86_64 |
| 612 | if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) |
| 613 | return 1; |
| 614 | #endif |
| 615 | return 0; |
| 616 | } |
| 617 | |
| 618 | static int is_f00f_bug(struct pt_regs *regs, unsigned long address) |
| 619 | { |
| 620 | #ifdef CONFIG_X86_F00F_BUG |
| 621 | unsigned long nr; |
| 622 | |
| 623 | /* |
| 624 | * Pentium F0 0F C7 C8 bug workaround: |
| 625 | */ |
| 626 | if (boot_cpu_has_bug(X86_BUG_F00F)) { |
| 627 | nr = (address - idt_descr.address) >> 3; |
| 628 | |
| 629 | if (nr == 6) { |
| 630 | do_invalid_op(regs, 0); |
| 631 | return 1; |
| 632 | } |
| 633 | } |
| 634 | #endif |
| 635 | return 0; |
| 636 | } |
| 637 | |
| 638 | static const char nx_warning[] = KERN_CRIT |
| 639 | "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n"; |
| 640 | static const char smep_warning[] = KERN_CRIT |
| 641 | "unable to execute userspace code (SMEP?) (uid: %d)\n"; |
| 642 | |
| 643 | static void |
| 644 | show_fault_oops(struct pt_regs *regs, unsigned long error_code, |
| 645 | unsigned long address) |
| 646 | { |
| 647 | if (!oops_may_print()) |
| 648 | return; |
| 649 | |
| 650 | if (error_code & PF_INSTR) { |
| 651 | unsigned int level; |
| 652 | pgd_t *pgd; |
| 653 | pte_t *pte; |
| 654 | |
| 655 | pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK); |
| 656 | pgd += pgd_index(address); |
| 657 | |
| 658 | pte = lookup_address_in_pgd(pgd, address, &level); |
| 659 | |
| 660 | if (pte && pte_present(*pte) && !pte_exec(*pte)) |
| 661 | printk(nx_warning, from_kuid(&init_user_ns, current_uid())); |
| 662 | if (pte && pte_present(*pte) && pte_exec(*pte) && |
| 663 | (pgd_flags(*pgd) & _PAGE_USER) && |
| 664 | (__read_cr4() & X86_CR4_SMEP)) |
| 665 | printk(smep_warning, from_kuid(&init_user_ns, current_uid())); |
| 666 | } |
| 667 | |
| 668 | printk(KERN_ALERT "BUG: unable to handle kernel "); |
| 669 | if (address < PAGE_SIZE) |
| 670 | printk(KERN_CONT "NULL pointer dereference"); |
| 671 | else |
| 672 | printk(KERN_CONT "paging request"); |
| 673 | |
| 674 | printk(KERN_CONT " at %p\n", (void *) address); |
| 675 | printk(KERN_ALERT "IP:"); |
| 676 | printk_address(regs->ip); |
| 677 | |
| 678 | dump_pagetable(address); |
| 679 | } |
| 680 | |
| 681 | static noinline void |
| 682 | pgtable_bad(struct pt_regs *regs, unsigned long error_code, |
| 683 | unsigned long address) |
| 684 | { |
| 685 | struct task_struct *tsk; |
| 686 | unsigned long flags; |
| 687 | int sig; |
| 688 | |
| 689 | flags = oops_begin(); |
| 690 | tsk = current; |
| 691 | sig = SIGKILL; |
| 692 | |
| 693 | printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", |
| 694 | tsk->comm, address); |
| 695 | dump_pagetable(address); |
| 696 | |
| 697 | tsk->thread.cr2 = address; |
| 698 | tsk->thread.trap_nr = X86_TRAP_PF; |
| 699 | tsk->thread.error_code = error_code; |
| 700 | |
| 701 | if (__die("Bad pagetable", regs, error_code)) |
| 702 | sig = 0; |
| 703 | |
| 704 | oops_end(flags, regs, sig); |
| 705 | } |
| 706 | |
| 707 | static noinline void |
| 708 | no_context(struct pt_regs *regs, unsigned long error_code, |
| 709 | unsigned long address, int signal, int si_code) |
| 710 | { |
| 711 | struct task_struct *tsk = current; |
| 712 | unsigned long flags; |
| 713 | int sig; |
| 714 | /* No context means no VMA to pass down */ |
| 715 | struct vm_area_struct *vma = NULL; |
| 716 | |
| 717 | /* Are we prepared to handle this kernel fault? */ |
| 718 | if (fixup_exception(regs)) { |
| 719 | /* |
| 720 | * Any interrupt that takes a fault gets the fixup. This makes |
| 721 | * the below recursive fault logic only apply to a faults from |
| 722 | * task context. |
| 723 | */ |
| 724 | if (in_interrupt()) |
| 725 | return; |
| 726 | |
| 727 | /* |
| 728 | * Per the above we're !in_interrupt(), aka. task context. |
| 729 | * |
| 730 | * In this case we need to make sure we're not recursively |
| 731 | * faulting through the emulate_vsyscall() logic. |
| 732 | */ |
| 733 | if (current_thread_info()->sig_on_uaccess_error && signal) { |
| 734 | tsk->thread.trap_nr = X86_TRAP_PF; |
| 735 | tsk->thread.error_code = error_code | PF_USER; |
| 736 | tsk->thread.cr2 = address; |
| 737 | |
| 738 | /* XXX: hwpoison faults will set the wrong code. */ |
| 739 | force_sig_info_fault(signal, si_code, address, |
| 740 | tsk, vma, 0); |
| 741 | } |
| 742 | |
| 743 | /* |
| 744 | * Barring that, we can do the fixup and be happy. |
| 745 | */ |
| 746 | return; |
| 747 | } |
| 748 | |
| 749 | /* |
| 750 | * 32-bit: |
| 751 | * |
| 752 | * Valid to do another page fault here, because if this fault |
| 753 | * had been triggered by is_prefetch fixup_exception would have |
| 754 | * handled it. |
| 755 | * |
| 756 | * 64-bit: |
| 757 | * |
| 758 | * Hall of shame of CPU/BIOS bugs. |
| 759 | */ |
| 760 | if (is_prefetch(regs, error_code, address)) |
| 761 | return; |
| 762 | |
| 763 | if (is_errata93(regs, address)) |
| 764 | return; |
| 765 | |
| 766 | /* |
| 767 | * Oops. The kernel tried to access some bad page. We'll have to |
| 768 | * terminate things with extreme prejudice: |
| 769 | */ |
| 770 | flags = oops_begin(); |
| 771 | |
| 772 | show_fault_oops(regs, error_code, address); |
| 773 | |
| 774 | if (task_stack_end_corrupted(tsk)) |
| 775 | printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); |
| 776 | |
| 777 | tsk->thread.cr2 = address; |
| 778 | tsk->thread.trap_nr = X86_TRAP_PF; |
| 779 | tsk->thread.error_code = error_code; |
| 780 | |
| 781 | sig = SIGKILL; |
| 782 | if (__die("Oops", regs, error_code)) |
| 783 | sig = 0; |
| 784 | |
| 785 | /* Executive summary in case the body of the oops scrolled away */ |
| 786 | printk(KERN_DEFAULT "CR2: %016lx\n", address); |
| 787 | |
| 788 | oops_end(flags, regs, sig); |
| 789 | } |
| 790 | |
| 791 | /* |
| 792 | * Print out info about fatal segfaults, if the show_unhandled_signals |
| 793 | * sysctl is set: |
| 794 | */ |
| 795 | static inline void |
| 796 | show_signal_msg(struct pt_regs *regs, unsigned long error_code, |
| 797 | unsigned long address, struct task_struct *tsk) |
| 798 | { |
| 799 | if (!unhandled_signal(tsk, SIGSEGV)) |
| 800 | return; |
| 801 | |
| 802 | if (!printk_ratelimit()) |
| 803 | return; |
| 804 | |
| 805 | printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx", |
| 806 | task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, |
| 807 | tsk->comm, task_pid_nr(tsk), address, |
| 808 | (void *)regs->ip, (void *)regs->sp, error_code); |
| 809 | |
| 810 | print_vma_addr(KERN_CONT " in ", regs->ip); |
| 811 | |
| 812 | printk(KERN_CONT "\n"); |
| 813 | } |
| 814 | |
| 815 | static void |
| 816 | __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, |
| 817 | unsigned long address, struct vm_area_struct *vma, |
| 818 | int si_code) |
| 819 | { |
| 820 | struct task_struct *tsk = current; |
| 821 | |
| 822 | /* User mode accesses just cause a SIGSEGV */ |
| 823 | if (error_code & PF_USER) { |
| 824 | /* |
| 825 | * It's possible to have interrupts off here: |
| 826 | */ |
| 827 | local_irq_enable(); |
| 828 | |
| 829 | /* |
| 830 | * Valid to do another page fault here because this one came |
| 831 | * from user space: |
| 832 | */ |
| 833 | if (is_prefetch(regs, error_code, address)) |
| 834 | return; |
| 835 | |
| 836 | if (is_errata100(regs, address)) |
| 837 | return; |
| 838 | |
| 839 | #ifdef CONFIG_X86_64 |
| 840 | /* |
| 841 | * Instruction fetch faults in the vsyscall page might need |
| 842 | * emulation. |
| 843 | */ |
| 844 | if (unlikely((error_code & PF_INSTR) && |
| 845 | ((address & ~0xfff) == VSYSCALL_ADDR))) { |
| 846 | if (emulate_vsyscall(regs, address)) |
| 847 | return; |
| 848 | } |
| 849 | #endif |
| 850 | /* Kernel addresses are always protection faults: */ |
| 851 | if (address >= TASK_SIZE) |
| 852 | error_code |= PF_PROT; |
| 853 | |
| 854 | if (likely(show_unhandled_signals)) |
| 855 | show_signal_msg(regs, error_code, address, tsk); |
| 856 | |
| 857 | tsk->thread.cr2 = address; |
| 858 | tsk->thread.error_code = error_code; |
| 859 | tsk->thread.trap_nr = X86_TRAP_PF; |
| 860 | |
| 861 | force_sig_info_fault(SIGSEGV, si_code, address, tsk, vma, 0); |
| 862 | |
| 863 | return; |
| 864 | } |
| 865 | |
| 866 | if (is_f00f_bug(regs, address)) |
| 867 | return; |
| 868 | |
| 869 | no_context(regs, error_code, address, SIGSEGV, si_code); |
| 870 | } |
| 871 | |
| 872 | static noinline void |
| 873 | bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, |
| 874 | unsigned long address, struct vm_area_struct *vma) |
| 875 | { |
| 876 | __bad_area_nosemaphore(regs, error_code, address, vma, SEGV_MAPERR); |
| 877 | } |
| 878 | |
| 879 | static void |
| 880 | __bad_area(struct pt_regs *regs, unsigned long error_code, |
| 881 | unsigned long address, struct vm_area_struct *vma, int si_code) |
| 882 | { |
| 883 | struct mm_struct *mm = current->mm; |
| 884 | |
| 885 | /* |
| 886 | * Something tried to access memory that isn't in our memory map.. |
| 887 | * Fix it, but check if it's kernel or user first.. |
| 888 | */ |
| 889 | up_read(&mm->mmap_sem); |
| 890 | |
| 891 | __bad_area_nosemaphore(regs, error_code, address, vma, si_code); |
| 892 | } |
| 893 | |
| 894 | static noinline void |
| 895 | bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) |
| 896 | { |
| 897 | __bad_area(regs, error_code, address, NULL, SEGV_MAPERR); |
| 898 | } |
| 899 | |
| 900 | static inline bool bad_area_access_from_pkeys(unsigned long error_code, |
| 901 | struct vm_area_struct *vma) |
| 902 | { |
| 903 | if (!boot_cpu_has(X86_FEATURE_OSPKE)) |
| 904 | return false; |
| 905 | if (error_code & PF_PK) |
| 906 | return true; |
| 907 | return false; |
| 908 | } |
| 909 | |
| 910 | static noinline void |
| 911 | bad_area_access_error(struct pt_regs *regs, unsigned long error_code, |
| 912 | unsigned long address, struct vm_area_struct *vma) |
| 913 | { |
| 914 | /* |
| 915 | * This OSPKE check is not strictly necessary at runtime. |
| 916 | * But, doing it this way allows compiler optimizations |
| 917 | * if pkeys are compiled out. |
| 918 | */ |
| 919 | if (bad_area_access_from_pkeys(error_code, vma)) |
| 920 | __bad_area(regs, error_code, address, vma, SEGV_PKUERR); |
| 921 | else |
| 922 | __bad_area(regs, error_code, address, vma, SEGV_ACCERR); |
| 923 | } |
| 924 | |
| 925 | static void |
| 926 | do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, |
| 927 | struct vm_area_struct *vma, unsigned int fault) |
| 928 | { |
| 929 | struct task_struct *tsk = current; |
| 930 | int code = BUS_ADRERR; |
| 931 | |
| 932 | /* Kernel mode? Handle exceptions or die: */ |
| 933 | if (!(error_code & PF_USER)) { |
| 934 | no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); |
| 935 | return; |
| 936 | } |
| 937 | |
| 938 | /* User-space => ok to do another page fault: */ |
| 939 | if (is_prefetch(regs, error_code, address)) |
| 940 | return; |
| 941 | |
| 942 | tsk->thread.cr2 = address; |
| 943 | tsk->thread.error_code = error_code; |
| 944 | tsk->thread.trap_nr = X86_TRAP_PF; |
| 945 | |
| 946 | #ifdef CONFIG_MEMORY_FAILURE |
| 947 | if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { |
| 948 | printk(KERN_ERR |
| 949 | "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", |
| 950 | tsk->comm, tsk->pid, address); |
| 951 | code = BUS_MCEERR_AR; |
| 952 | } |
| 953 | #endif |
| 954 | force_sig_info_fault(SIGBUS, code, address, tsk, vma, fault); |
| 955 | } |
| 956 | |
| 957 | static noinline void |
| 958 | mm_fault_error(struct pt_regs *regs, unsigned long error_code, |
| 959 | unsigned long address, struct vm_area_struct *vma, |
| 960 | unsigned int fault) |
| 961 | { |
| 962 | if (fatal_signal_pending(current) && !(error_code & PF_USER)) { |
| 963 | no_context(regs, error_code, address, 0, 0); |
| 964 | return; |
| 965 | } |
| 966 | |
| 967 | if (fault & VM_FAULT_OOM) { |
| 968 | /* Kernel mode? Handle exceptions or die: */ |
| 969 | if (!(error_code & PF_USER)) { |
| 970 | no_context(regs, error_code, address, |
| 971 | SIGSEGV, SEGV_MAPERR); |
| 972 | return; |
| 973 | } |
| 974 | |
| 975 | /* |
| 976 | * We ran out of memory, call the OOM killer, and return the |
| 977 | * userspace (which will retry the fault, or kill us if we got |
| 978 | * oom-killed): |
| 979 | */ |
| 980 | pagefault_out_of_memory(); |
| 981 | } else { |
| 982 | if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| |
| 983 | VM_FAULT_HWPOISON_LARGE)) |
| 984 | do_sigbus(regs, error_code, address, vma, fault); |
| 985 | else if (fault & VM_FAULT_SIGSEGV) |
| 986 | bad_area_nosemaphore(regs, error_code, address, vma); |
| 987 | else |
| 988 | BUG(); |
| 989 | } |
| 990 | } |
| 991 | |
| 992 | static int spurious_fault_check(unsigned long error_code, pte_t *pte) |
| 993 | { |
| 994 | if ((error_code & PF_WRITE) && !pte_write(*pte)) |
| 995 | return 0; |
| 996 | |
| 997 | if ((error_code & PF_INSTR) && !pte_exec(*pte)) |
| 998 | return 0; |
| 999 | /* |
| 1000 | * Note: We do not do lazy flushing on protection key |
| 1001 | * changes, so no spurious fault will ever set PF_PK. |
| 1002 | */ |
| 1003 | if ((error_code & PF_PK)) |
| 1004 | return 1; |
| 1005 | |
| 1006 | return 1; |
| 1007 | } |
| 1008 | |
| 1009 | /* |
| 1010 | * Handle a spurious fault caused by a stale TLB entry. |
| 1011 | * |
| 1012 | * This allows us to lazily refresh the TLB when increasing the |
| 1013 | * permissions of a kernel page (RO -> RW or NX -> X). Doing it |
| 1014 | * eagerly is very expensive since that implies doing a full |
| 1015 | * cross-processor TLB flush, even if no stale TLB entries exist |
| 1016 | * on other processors. |
| 1017 | * |
| 1018 | * Spurious faults may only occur if the TLB contains an entry with |
| 1019 | * fewer permission than the page table entry. Non-present (P = 0) |
| 1020 | * and reserved bit (R = 1) faults are never spurious. |
| 1021 | * |
| 1022 | * There are no security implications to leaving a stale TLB when |
| 1023 | * increasing the permissions on a page. |
| 1024 | * |
| 1025 | * Returns non-zero if a spurious fault was handled, zero otherwise. |
| 1026 | * |
| 1027 | * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 |
| 1028 | * (Optional Invalidation). |
| 1029 | */ |
| 1030 | static noinline int |
| 1031 | spurious_fault(unsigned long error_code, unsigned long address) |
| 1032 | { |
| 1033 | pgd_t *pgd; |
| 1034 | pud_t *pud; |
| 1035 | pmd_t *pmd; |
| 1036 | pte_t *pte; |
| 1037 | int ret; |
| 1038 | |
| 1039 | /* |
| 1040 | * Only writes to RO or instruction fetches from NX may cause |
| 1041 | * spurious faults. |
| 1042 | * |
| 1043 | * These could be from user or supervisor accesses but the TLB |
| 1044 | * is only lazily flushed after a kernel mapping protection |
| 1045 | * change, so user accesses are not expected to cause spurious |
| 1046 | * faults. |
| 1047 | */ |
| 1048 | if (error_code != (PF_WRITE | PF_PROT) |
| 1049 | && error_code != (PF_INSTR | PF_PROT)) |
| 1050 | return 0; |
| 1051 | |
| 1052 | pgd = init_mm.pgd + pgd_index(address); |
| 1053 | if (!pgd_present(*pgd)) |
| 1054 | return 0; |
| 1055 | |
| 1056 | pud = pud_offset(pgd, address); |
| 1057 | if (!pud_present(*pud)) |
| 1058 | return 0; |
| 1059 | |
| 1060 | if (pud_large(*pud)) |
| 1061 | return spurious_fault_check(error_code, (pte_t *) pud); |
| 1062 | |
| 1063 | pmd = pmd_offset(pud, address); |
| 1064 | if (!pmd_present(*pmd)) |
| 1065 | return 0; |
| 1066 | |
| 1067 | if (pmd_large(*pmd)) |
| 1068 | return spurious_fault_check(error_code, (pte_t *) pmd); |
| 1069 | |
| 1070 | pte = pte_offset_kernel(pmd, address); |
| 1071 | if (!pte_present(*pte)) |
| 1072 | return 0; |
| 1073 | |
| 1074 | ret = spurious_fault_check(error_code, pte); |
| 1075 | if (!ret) |
| 1076 | return 0; |
| 1077 | |
| 1078 | /* |
| 1079 | * Make sure we have permissions in PMD. |
| 1080 | * If not, then there's a bug in the page tables: |
| 1081 | */ |
| 1082 | ret = spurious_fault_check(error_code, (pte_t *) pmd); |
| 1083 | WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); |
| 1084 | |
| 1085 | return ret; |
| 1086 | } |
| 1087 | NOKPROBE_SYMBOL(spurious_fault); |
| 1088 | |
| 1089 | int show_unhandled_signals = 1; |
| 1090 | |
| 1091 | static inline int |
| 1092 | access_error(unsigned long error_code, struct vm_area_struct *vma) |
| 1093 | { |
| 1094 | /* |
| 1095 | * Access or read was blocked by protection keys. We do |
| 1096 | * this check before any others because we do not want |
| 1097 | * to, for instance, confuse a protection-key-denied |
| 1098 | * write with one for which we should do a COW. |
| 1099 | */ |
| 1100 | if (error_code & PF_PK) |
| 1101 | return 1; |
| 1102 | |
| 1103 | if (error_code & PF_WRITE) { |
| 1104 | /* write, present and write, not present: */ |
| 1105 | if (unlikely(!(vma->vm_flags & VM_WRITE))) |
| 1106 | return 1; |
| 1107 | return 0; |
| 1108 | } |
| 1109 | |
| 1110 | /* read, present: */ |
| 1111 | if (unlikely(error_code & PF_PROT)) |
| 1112 | return 1; |
| 1113 | |
| 1114 | /* read, not present: */ |
| 1115 | if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) |
| 1116 | return 1; |
| 1117 | |
| 1118 | return 0; |
| 1119 | } |
| 1120 | |
| 1121 | static int fault_in_kernel_space(unsigned long address) |
| 1122 | { |
| 1123 | return address >= TASK_SIZE_MAX; |
| 1124 | } |
| 1125 | |
| 1126 | static inline bool smap_violation(int error_code, struct pt_regs *regs) |
| 1127 | { |
| 1128 | if (!IS_ENABLED(CONFIG_X86_SMAP)) |
| 1129 | return false; |
| 1130 | |
| 1131 | if (!static_cpu_has(X86_FEATURE_SMAP)) |
| 1132 | return false; |
| 1133 | |
| 1134 | if (error_code & PF_USER) |
| 1135 | return false; |
| 1136 | |
| 1137 | if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC)) |
| 1138 | return false; |
| 1139 | |
| 1140 | return true; |
| 1141 | } |
| 1142 | |
| 1143 | /* |
| 1144 | * This routine handles page faults. It determines the address, |
| 1145 | * and the problem, and then passes it off to one of the appropriate |
| 1146 | * routines. |
| 1147 | * |
| 1148 | * This function must have noinline because both callers |
| 1149 | * {,trace_}do_page_fault() have notrace on. Having this an actual function |
| 1150 | * guarantees there's a function trace entry. |
| 1151 | */ |
| 1152 | static noinline void |
| 1153 | __do_page_fault(struct pt_regs *regs, unsigned long error_code, |
| 1154 | unsigned long address) |
| 1155 | { |
| 1156 | struct vm_area_struct *vma; |
| 1157 | struct task_struct *tsk; |
| 1158 | struct mm_struct *mm; |
| 1159 | int fault, major = 0; |
| 1160 | unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; |
| 1161 | |
| 1162 | tsk = current; |
| 1163 | mm = tsk->mm; |
| 1164 | |
| 1165 | /* |
| 1166 | * Detect and handle instructions that would cause a page fault for |
| 1167 | * both a tracked kernel page and a userspace page. |
| 1168 | */ |
| 1169 | if (kmemcheck_active(regs)) |
| 1170 | kmemcheck_hide(regs); |
| 1171 | prefetchw(&mm->mmap_sem); |
| 1172 | |
| 1173 | if (unlikely(kmmio_fault(regs, address))) |
| 1174 | return; |
| 1175 | |
| 1176 | /* |
| 1177 | * We fault-in kernel-space virtual memory on-demand. The |
| 1178 | * 'reference' page table is init_mm.pgd. |
| 1179 | * |
| 1180 | * NOTE! We MUST NOT take any locks for this case. We may |
| 1181 | * be in an interrupt or a critical region, and should |
| 1182 | * only copy the information from the master page table, |
| 1183 | * nothing more. |
| 1184 | * |
| 1185 | * This verifies that the fault happens in kernel space |
| 1186 | * (error_code & 4) == 0, and that the fault was not a |
| 1187 | * protection error (error_code & 9) == 0. |
| 1188 | */ |
| 1189 | if (unlikely(fault_in_kernel_space(address))) { |
| 1190 | if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) { |
| 1191 | if (vmalloc_fault(address) >= 0) |
| 1192 | return; |
| 1193 | |
| 1194 | if (kmemcheck_fault(regs, address, error_code)) |
| 1195 | return; |
| 1196 | } |
| 1197 | |
| 1198 | /* Can handle a stale RO->RW TLB: */ |
| 1199 | if (spurious_fault(error_code, address)) |
| 1200 | return; |
| 1201 | |
| 1202 | /* kprobes don't want to hook the spurious faults: */ |
| 1203 | if (kprobes_fault(regs)) |
| 1204 | return; |
| 1205 | /* |
| 1206 | * Don't take the mm semaphore here. If we fixup a prefetch |
| 1207 | * fault we could otherwise deadlock: |
| 1208 | */ |
| 1209 | bad_area_nosemaphore(regs, error_code, address, NULL); |
| 1210 | |
| 1211 | return; |
| 1212 | } |
| 1213 | |
| 1214 | /* kprobes don't want to hook the spurious faults: */ |
| 1215 | if (unlikely(kprobes_fault(regs))) |
| 1216 | return; |
| 1217 | |
| 1218 | if (unlikely(error_code & PF_RSVD)) |
| 1219 | pgtable_bad(regs, error_code, address); |
| 1220 | |
| 1221 | if (unlikely(smap_violation(error_code, regs))) { |
| 1222 | bad_area_nosemaphore(regs, error_code, address, NULL); |
| 1223 | return; |
| 1224 | } |
| 1225 | |
| 1226 | /* |
| 1227 | * If we're in an interrupt, have no user context or are running |
| 1228 | * in a region with pagefaults disabled then we must not take the fault |
| 1229 | */ |
| 1230 | if (unlikely(faulthandler_disabled() || !mm)) { |
| 1231 | bad_area_nosemaphore(regs, error_code, address, NULL); |
| 1232 | return; |
| 1233 | } |
| 1234 | |
| 1235 | /* |
| 1236 | * It's safe to allow irq's after cr2 has been saved and the |
| 1237 | * vmalloc fault has been handled. |
| 1238 | * |
| 1239 | * User-mode registers count as a user access even for any |
| 1240 | * potential system fault or CPU buglet: |
| 1241 | */ |
| 1242 | if (user_mode(regs)) { |
| 1243 | local_irq_enable(); |
| 1244 | error_code |= PF_USER; |
| 1245 | flags |= FAULT_FLAG_USER; |
| 1246 | } else { |
| 1247 | if (regs->flags & X86_EFLAGS_IF) |
| 1248 | local_irq_enable(); |
| 1249 | } |
| 1250 | |
| 1251 | perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); |
| 1252 | |
| 1253 | if (error_code & PF_WRITE) |
| 1254 | flags |= FAULT_FLAG_WRITE; |
| 1255 | |
| 1256 | /* |
| 1257 | * When running in the kernel we expect faults to occur only to |
| 1258 | * addresses in user space. All other faults represent errors in |
| 1259 | * the kernel and should generate an OOPS. Unfortunately, in the |
| 1260 | * case of an erroneous fault occurring in a code path which already |
| 1261 | * holds mmap_sem we will deadlock attempting to validate the fault |
| 1262 | * against the address space. Luckily the kernel only validly |
| 1263 | * references user space from well defined areas of code, which are |
| 1264 | * listed in the exceptions table. |
| 1265 | * |
| 1266 | * As the vast majority of faults will be valid we will only perform |
| 1267 | * the source reference check when there is a possibility of a |
| 1268 | * deadlock. Attempt to lock the address space, if we cannot we then |
| 1269 | * validate the source. If this is invalid we can skip the address |
| 1270 | * space check, thus avoiding the deadlock: |
| 1271 | */ |
| 1272 | if (unlikely(!down_read_trylock(&mm->mmap_sem))) { |
| 1273 | if ((error_code & PF_USER) == 0 && |
| 1274 | !search_exception_tables(regs->ip)) { |
| 1275 | bad_area_nosemaphore(regs, error_code, address, NULL); |
| 1276 | return; |
| 1277 | } |
| 1278 | retry: |
| 1279 | down_read(&mm->mmap_sem); |
| 1280 | } else { |
| 1281 | /* |
| 1282 | * The above down_read_trylock() might have succeeded in |
| 1283 | * which case we'll have missed the might_sleep() from |
| 1284 | * down_read(): |
| 1285 | */ |
| 1286 | might_sleep(); |
| 1287 | } |
| 1288 | |
| 1289 | vma = find_vma(mm, address); |
| 1290 | if (unlikely(!vma)) { |
| 1291 | bad_area(regs, error_code, address); |
| 1292 | return; |
| 1293 | } |
| 1294 | if (likely(vma->vm_start <= address)) |
| 1295 | goto good_area; |
| 1296 | if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { |
| 1297 | bad_area(regs, error_code, address); |
| 1298 | return; |
| 1299 | } |
| 1300 | if (error_code & PF_USER) { |
| 1301 | /* |
| 1302 | * Accessing the stack below %sp is always a bug. |
| 1303 | * The large cushion allows instructions like enter |
| 1304 | * and pusha to work. ("enter $65535, $31" pushes |
| 1305 | * 32 pointers and then decrements %sp by 65535.) |
| 1306 | */ |
| 1307 | if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { |
| 1308 | bad_area(regs, error_code, address); |
| 1309 | return; |
| 1310 | } |
| 1311 | } |
| 1312 | if (unlikely(expand_stack(vma, address))) { |
| 1313 | bad_area(regs, error_code, address); |
| 1314 | return; |
| 1315 | } |
| 1316 | |
| 1317 | /* |
| 1318 | * Ok, we have a good vm_area for this memory access, so |
| 1319 | * we can handle it.. |
| 1320 | */ |
| 1321 | good_area: |
| 1322 | if (unlikely(access_error(error_code, vma))) { |
| 1323 | bad_area_access_error(regs, error_code, address, vma); |
| 1324 | return; |
| 1325 | } |
| 1326 | |
| 1327 | /* |
| 1328 | * If for any reason at all we couldn't handle the fault, |
| 1329 | * make sure we exit gracefully rather than endlessly redo |
| 1330 | * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if |
| 1331 | * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked. |
| 1332 | */ |
| 1333 | fault = handle_mm_fault(mm, vma, address, flags); |
| 1334 | major |= fault & VM_FAULT_MAJOR; |
| 1335 | |
| 1336 | /* |
| 1337 | * If we need to retry the mmap_sem has already been released, |
| 1338 | * and if there is a fatal signal pending there is no guarantee |
| 1339 | * that we made any progress. Handle this case first. |
| 1340 | */ |
| 1341 | if (unlikely(fault & VM_FAULT_RETRY)) { |
| 1342 | /* Retry at most once */ |
| 1343 | if (flags & FAULT_FLAG_ALLOW_RETRY) { |
| 1344 | flags &= ~FAULT_FLAG_ALLOW_RETRY; |
| 1345 | flags |= FAULT_FLAG_TRIED; |
| 1346 | if (!fatal_signal_pending(tsk)) |
| 1347 | goto retry; |
| 1348 | } |
| 1349 | |
| 1350 | /* User mode? Just return to handle the fatal exception */ |
| 1351 | if (flags & FAULT_FLAG_USER) |
| 1352 | return; |
| 1353 | |
| 1354 | /* Not returning to user mode? Handle exceptions or die: */ |
| 1355 | no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); |
| 1356 | return; |
| 1357 | } |
| 1358 | |
| 1359 | up_read(&mm->mmap_sem); |
| 1360 | if (unlikely(fault & VM_FAULT_ERROR)) { |
| 1361 | mm_fault_error(regs, error_code, address, vma, fault); |
| 1362 | return; |
| 1363 | } |
| 1364 | |
| 1365 | /* |
| 1366 | * Major/minor page fault accounting. If any of the events |
| 1367 | * returned VM_FAULT_MAJOR, we account it as a major fault. |
| 1368 | */ |
| 1369 | if (major) { |
| 1370 | tsk->maj_flt++; |
| 1371 | perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); |
| 1372 | } else { |
| 1373 | tsk->min_flt++; |
| 1374 | perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); |
| 1375 | } |
| 1376 | |
| 1377 | check_v8086_mode(regs, address, tsk); |
| 1378 | } |
| 1379 | NOKPROBE_SYMBOL(__do_page_fault); |
| 1380 | |
| 1381 | dotraplinkage void notrace |
| 1382 | do_page_fault(struct pt_regs *regs, unsigned long error_code) |
| 1383 | { |
| 1384 | unsigned long address = read_cr2(); /* Get the faulting address */ |
| 1385 | enum ctx_state prev_state; |
| 1386 | |
| 1387 | /* |
| 1388 | * We must have this function tagged with __kprobes, notrace and call |
| 1389 | * read_cr2() before calling anything else. To avoid calling any kind |
| 1390 | * of tracing machinery before we've observed the CR2 value. |
| 1391 | * |
| 1392 | * exception_{enter,exit}() contain all sorts of tracepoints. |
| 1393 | */ |
| 1394 | |
| 1395 | prev_state = exception_enter(); |
| 1396 | __do_page_fault(regs, error_code, address); |
| 1397 | exception_exit(prev_state); |
| 1398 | } |
| 1399 | NOKPROBE_SYMBOL(do_page_fault); |
| 1400 | |
| 1401 | #ifdef CONFIG_TRACING |
| 1402 | static nokprobe_inline void |
| 1403 | trace_page_fault_entries(unsigned long address, struct pt_regs *regs, |
| 1404 | unsigned long error_code) |
| 1405 | { |
| 1406 | if (user_mode(regs)) |
| 1407 | trace_page_fault_user(address, regs, error_code); |
| 1408 | else |
| 1409 | trace_page_fault_kernel(address, regs, error_code); |
| 1410 | } |
| 1411 | |
| 1412 | dotraplinkage void notrace |
| 1413 | trace_do_page_fault(struct pt_regs *regs, unsigned long error_code) |
| 1414 | { |
| 1415 | /* |
| 1416 | * The exception_enter and tracepoint processing could |
| 1417 | * trigger another page faults (user space callchain |
| 1418 | * reading) and destroy the original cr2 value, so read |
| 1419 | * the faulting address now. |
| 1420 | */ |
| 1421 | unsigned long address = read_cr2(); |
| 1422 | enum ctx_state prev_state; |
| 1423 | |
| 1424 | prev_state = exception_enter(); |
| 1425 | trace_page_fault_entries(address, regs, error_code); |
| 1426 | __do_page_fault(regs, error_code, address); |
| 1427 | exception_exit(prev_state); |
| 1428 | } |
| 1429 | NOKPROBE_SYMBOL(trace_do_page_fault); |
| 1430 | #endif /* CONFIG_TRACING */ |