1 /* 2 * Based on arch/arm/mm/fault.c 3 * 4 * Copyright (C) 1995 Linus Torvalds 5 * Copyright (C) 1995-2004 Russell King 6 * Copyright (C) 2012 ARM Ltd. 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License version 2 as 10 * published by the Free Software Foundation. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program. If not, see <http://www.gnu.org/licenses/>. 19 */ 20 21 #include <linux/module.h> 22 #include <linux/signal.h> 23 #include <linux/mm.h> 24 #include <linux/hardirq.h> 25 #include <linux/init.h> 26 #include <linux/kprobes.h> 27 #include <linux/uaccess.h> 28 #include <linux/page-flags.h> 29 #include <linux/sched.h> 30 #include <linux/highmem.h> 31 #include <linux/perf_event.h> 32 33 #include <asm/exception.h> 34 #include <asm/debug-monitors.h> 35 #include <asm/esr.h> 36 #include <asm/system_misc.h> 37 #include <asm/pgtable.h> 38 #include <asm/tlbflush.h> 39 40 static const char *fault_name(unsigned int esr); 41 42 /* 43 * Dump out the page tables associated with 'addr' in mm 'mm'. 44 */ 45 void show_pte(struct mm_struct *mm, unsigned long addr) 46 { 47 pgd_t *pgd; 48 49 if (!mm) 50 mm = &init_mm; 51 52 pr_alert("pgd = %p\n", mm->pgd); 53 pgd = pgd_offset(mm, addr); 54 pr_alert("[%08lx] *pgd=%016llx", addr, pgd_val(*pgd)); 55 56 do { 57 pud_t *pud; 58 pmd_t *pmd; 59 pte_t *pte; 60 61 if (pgd_none(*pgd) || pgd_bad(*pgd)) 62 break; 63 64 pud = pud_offset(pgd, addr); 65 printk(", *pud=%016llx", pud_val(*pud)); 66 if (pud_none(*pud) || pud_bad(*pud)) 67 break; 68 69 pmd = pmd_offset(pud, addr); 70 printk(", *pmd=%016llx", pmd_val(*pmd)); 71 if (pmd_none(*pmd) || pmd_bad(*pmd)) 72 break; 73 74 pte = pte_offset_map(pmd, addr); 75 printk(", *pte=%016llx", pte_val(*pte)); 76 pte_unmap(pte); 77 } while(0); 78 79 printk("\n"); 80 } 81 82 /* 83 * The kernel tried to access some page that wasn't present. 84 */ 85 static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr, 86 unsigned int esr, struct pt_regs *regs) 87 { 88 /* 89 * Are we prepared to handle this kernel fault? 90 */ 91 if (fixup_exception(regs)) 92 return; 93 94 /* 95 * No handler, we'll have to terminate things with extreme prejudice. 96 */ 97 bust_spinlocks(1); 98 pr_alert("Unable to handle kernel %s at virtual address %08lx\n", 99 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 100 "paging request", addr); 101 102 show_pte(mm, addr); 103 die("Oops", regs, esr); 104 bust_spinlocks(0); 105 do_exit(SIGKILL); 106 } 107 108 /* 109 * Something tried to access memory that isn't in our memory map. User mode 110 * accesses just cause a SIGSEGV 111 */ 112 static void __do_user_fault(struct task_struct *tsk, unsigned long addr, 113 unsigned int esr, unsigned int sig, int code, 114 struct pt_regs *regs) 115 { 116 struct siginfo si; 117 118 if (show_unhandled_signals && unhandled_signal(tsk, sig) && 119 printk_ratelimit()) { 120 pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n", 121 tsk->comm, task_pid_nr(tsk), fault_name(esr), sig, 122 addr, esr); 123 show_pte(tsk->mm, addr); 124 show_regs(regs); 125 } 126 127 tsk->thread.fault_address = addr; 128 tsk->thread.fault_code = esr; 129 si.si_signo = sig; 130 si.si_errno = 0; 131 si.si_code = code; 132 si.si_addr = (void __user *)addr; 133 force_sig_info(sig, &si, tsk); 134 } 135 136 static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs) 137 { 138 struct task_struct *tsk = current; 139 struct mm_struct *mm = tsk->active_mm; 140 141 /* 142 * If we are in kernel mode at this point, we have no context to 143 * handle this fault with. 144 */ 145 if (user_mode(regs)) 146 __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs); 147 else 148 __do_kernel_fault(mm, addr, esr, regs); 149 } 150 151 #define VM_FAULT_BADMAP 0x010000 152 #define VM_FAULT_BADACCESS 0x020000 153 154 #define ESR_LNX_EXEC (1 << 24) 155 156 static int __do_page_fault(struct mm_struct *mm, unsigned long addr, 157 unsigned int mm_flags, unsigned long vm_flags, 158 struct task_struct *tsk) 159 { 160 struct vm_area_struct *vma; 161 int fault; 162 163 vma = find_vma(mm, addr); 164 fault = VM_FAULT_BADMAP; 165 if (unlikely(!vma)) 166 goto out; 167 if (unlikely(vma->vm_start > addr)) 168 goto check_stack; 169 170 /* 171 * Ok, we have a good vm_area for this memory access, so we can handle 172 * it. 173 */ 174 good_area: 175 /* 176 * Check that the permissions on the VMA allow for the fault which 177 * occurred. If we encountered a write or exec fault, we must have 178 * appropriate permissions, otherwise we allow any permission. 179 */ 180 if (!(vma->vm_flags & vm_flags)) { 181 fault = VM_FAULT_BADACCESS; 182 goto out; 183 } 184 185 return handle_mm_fault(mm, vma, addr & PAGE_MASK, mm_flags); 186 187 check_stack: 188 if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) 189 goto good_area; 190 out: 191 return fault; 192 } 193 194 static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 195 struct pt_regs *regs) 196 { 197 struct task_struct *tsk; 198 struct mm_struct *mm; 199 int fault, sig, code; 200 unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC; 201 unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 202 203 tsk = current; 204 mm = tsk->mm; 205 206 /* Enable interrupts if they were enabled in the parent context. */ 207 if (interrupts_enabled(regs)) 208 local_irq_enable(); 209 210 /* 211 * If we're in an interrupt or have no user context, we must not take 212 * the fault. 213 */ 214 if (in_atomic() || !mm) 215 goto no_context; 216 217 if (user_mode(regs)) 218 mm_flags |= FAULT_FLAG_USER; 219 220 if (esr & ESR_LNX_EXEC) { 221 vm_flags = VM_EXEC; 222 } else if ((esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM)) { 223 vm_flags = VM_WRITE; 224 mm_flags |= FAULT_FLAG_WRITE; 225 } 226 227 /* 228 * As per x86, we may deadlock here. However, since the kernel only 229 * validly references user space from well defined areas of the code, 230 * we can bug out early if this is from code which shouldn't. 231 */ 232 if (!down_read_trylock(&mm->mmap_sem)) { 233 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 234 goto no_context; 235 retry: 236 down_read(&mm->mmap_sem); 237 } else { 238 /* 239 * The above down_read_trylock() might have succeeded in which 240 * case, we'll have missed the might_sleep() from down_read(). 241 */ 242 might_sleep(); 243 #ifdef CONFIG_DEBUG_VM 244 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 245 goto no_context; 246 #endif 247 } 248 249 fault = __do_page_fault(mm, addr, mm_flags, vm_flags, tsk); 250 251 /* 252 * If we need to retry but a fatal signal is pending, handle the 253 * signal first. We do not need to release the mmap_sem because it 254 * would already be released in __lock_page_or_retry in mm/filemap.c. 255 */ 256 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 257 return 0; 258 259 /* 260 * Major/minor page fault accounting is only done on the initial 261 * attempt. If we go through a retry, it is extremely likely that the 262 * page will be found in page cache at that point. 263 */ 264 265 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 266 if (mm_flags & FAULT_FLAG_ALLOW_RETRY) { 267 if (fault & VM_FAULT_MAJOR) { 268 tsk->maj_flt++; 269 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, 270 addr); 271 } else { 272 tsk->min_flt++; 273 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, 274 addr); 275 } 276 if (fault & VM_FAULT_RETRY) { 277 /* 278 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of 279 * starvation. 280 */ 281 mm_flags &= ~FAULT_FLAG_ALLOW_RETRY; 282 goto retry; 283 } 284 } 285 286 up_read(&mm->mmap_sem); 287 288 /* 289 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR 290 */ 291 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | 292 VM_FAULT_BADACCESS)))) 293 return 0; 294 295 /* 296 * If we are in kernel mode at this point, we have no context to 297 * handle this fault with. 298 */ 299 if (!user_mode(regs)) 300 goto no_context; 301 302 if (fault & VM_FAULT_OOM) { 303 /* 304 * We ran out of memory, call the OOM killer, and return to 305 * userspace (which will retry the fault, or kill us if we got 306 * oom-killed). 307 */ 308 pagefault_out_of_memory(); 309 return 0; 310 } 311 312 if (fault & VM_FAULT_SIGBUS) { 313 /* 314 * We had some memory, but were unable to successfully fix up 315 * this page fault. 316 */ 317 sig = SIGBUS; 318 code = BUS_ADRERR; 319 } else { 320 /* 321 * Something tried to access memory that isn't in our memory 322 * map. 323 */ 324 sig = SIGSEGV; 325 code = fault == VM_FAULT_BADACCESS ? 326 SEGV_ACCERR : SEGV_MAPERR; 327 } 328 329 __do_user_fault(tsk, addr, esr, sig, code, regs); 330 return 0; 331 332 no_context: 333 __do_kernel_fault(mm, addr, esr, regs); 334 return 0; 335 } 336 337 /* 338 * First Level Translation Fault Handler 339 * 340 * We enter here because the first level page table doesn't contain a valid 341 * entry for the address. 342 * 343 * If the address is in kernel space (>= TASK_SIZE), then we are probably 344 * faulting in the vmalloc() area. 345 * 346 * If the init_task's first level page tables contains the relevant entry, we 347 * copy the it to this task. If not, we send the process a signal, fixup the 348 * exception, or oops the kernel. 349 * 350 * NOTE! We MUST NOT take any locks for this case. We may be in an interrupt 351 * or a critical region, and should only copy the information from the master 352 * page table, nothing more. 353 */ 354 static int __kprobes do_translation_fault(unsigned long addr, 355 unsigned int esr, 356 struct pt_regs *regs) 357 { 358 if (addr < TASK_SIZE) 359 return do_page_fault(addr, esr, regs); 360 361 do_bad_area(addr, esr, regs); 362 return 0; 363 } 364 365 /* 366 * This abort handler always returns "fault". 367 */ 368 static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs) 369 { 370 return 1; 371 } 372 373 static struct fault_info { 374 int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs); 375 int sig; 376 int code; 377 const char *name; 378 } fault_info[] = { 379 { do_bad, SIGBUS, 0, "ttbr address size fault" }, 380 { do_bad, SIGBUS, 0, "level 1 address size fault" }, 381 { do_bad, SIGBUS, 0, "level 2 address size fault" }, 382 { do_bad, SIGBUS, 0, "level 3 address size fault" }, 383 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 0 translation fault" }, 384 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" }, 385 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" }, 386 { do_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" }, 387 { do_bad, SIGBUS, 0, "reserved access flag fault" }, 388 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" }, 389 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" }, 390 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 access flag fault" }, 391 { do_bad, SIGBUS, 0, "reserved permission fault" }, 392 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" }, 393 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" }, 394 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" }, 395 { do_bad, SIGBUS, 0, "synchronous external abort" }, 396 { do_bad, SIGBUS, 0, "asynchronous external abort" }, 397 { do_bad, SIGBUS, 0, "unknown 18" }, 398 { do_bad, SIGBUS, 0, "unknown 19" }, 399 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 400 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 401 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 402 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 403 { do_bad, SIGBUS, 0, "synchronous parity error" }, 404 { do_bad, SIGBUS, 0, "asynchronous parity error" }, 405 { do_bad, SIGBUS, 0, "unknown 26" }, 406 { do_bad, SIGBUS, 0, "unknown 27" }, 407 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 408 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 409 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 410 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 411 { do_bad, SIGBUS, 0, "unknown 32" }, 412 { do_bad, SIGBUS, BUS_ADRALN, "alignment fault" }, 413 { do_bad, SIGBUS, 0, "debug event" }, 414 { do_bad, SIGBUS, 0, "unknown 35" }, 415 { do_bad, SIGBUS, 0, "unknown 36" }, 416 { do_bad, SIGBUS, 0, "unknown 37" }, 417 { do_bad, SIGBUS, 0, "unknown 38" }, 418 { do_bad, SIGBUS, 0, "unknown 39" }, 419 { do_bad, SIGBUS, 0, "unknown 40" }, 420 { do_bad, SIGBUS, 0, "unknown 41" }, 421 { do_bad, SIGBUS, 0, "unknown 42" }, 422 { do_bad, SIGBUS, 0, "unknown 43" }, 423 { do_bad, SIGBUS, 0, "unknown 44" }, 424 { do_bad, SIGBUS, 0, "unknown 45" }, 425 { do_bad, SIGBUS, 0, "unknown 46" }, 426 { do_bad, SIGBUS, 0, "unknown 47" }, 427 { do_bad, SIGBUS, 0, "unknown 48" }, 428 { do_bad, SIGBUS, 0, "unknown 49" }, 429 { do_bad, SIGBUS, 0, "unknown 50" }, 430 { do_bad, SIGBUS, 0, "unknown 51" }, 431 { do_bad, SIGBUS, 0, "implementation fault (lockdown abort)" }, 432 { do_bad, SIGBUS, 0, "unknown 53" }, 433 { do_bad, SIGBUS, 0, "unknown 54" }, 434 { do_bad, SIGBUS, 0, "unknown 55" }, 435 { do_bad, SIGBUS, 0, "unknown 56" }, 436 { do_bad, SIGBUS, 0, "unknown 57" }, 437 { do_bad, SIGBUS, 0, "implementation fault (coprocessor abort)" }, 438 { do_bad, SIGBUS, 0, "unknown 59" }, 439 { do_bad, SIGBUS, 0, "unknown 60" }, 440 { do_bad, SIGBUS, 0, "unknown 61" }, 441 { do_bad, SIGBUS, 0, "unknown 62" }, 442 { do_bad, SIGBUS, 0, "unknown 63" }, 443 }; 444 445 static const char *fault_name(unsigned int esr) 446 { 447 const struct fault_info *inf = fault_info + (esr & 63); 448 return inf->name; 449 } 450 451 /* 452 * Dispatch a data abort to the relevant handler. 453 */ 454 asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr, 455 struct pt_regs *regs) 456 { 457 const struct fault_info *inf = fault_info + (esr & 63); 458 struct siginfo info; 459 460 if (!inf->fn(addr, esr, regs)) 461 return; 462 463 pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n", 464 inf->name, esr, addr); 465 466 info.si_signo = inf->sig; 467 info.si_errno = 0; 468 info.si_code = inf->code; 469 info.si_addr = (void __user *)addr; 470 arm64_notify_die("", regs, &info, esr); 471 } 472 473 /* 474 * Handle stack alignment exceptions. 475 */ 476 asmlinkage void __exception do_sp_pc_abort(unsigned long addr, 477 unsigned int esr, 478 struct pt_regs *regs) 479 { 480 struct siginfo info; 481 482 info.si_signo = SIGBUS; 483 info.si_errno = 0; 484 info.si_code = BUS_ADRALN; 485 info.si_addr = (void __user *)addr; 486 arm64_notify_die("", regs, &info, esr); 487 } 488 489 static struct fault_info debug_fault_info[] = { 490 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware breakpoint" }, 491 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware single-step" }, 492 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware watchpoint" }, 493 { do_bad, SIGBUS, 0, "unknown 3" }, 494 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch32 BKPT" }, 495 { do_bad, SIGTRAP, 0, "aarch32 vector catch" }, 496 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch64 BRK" }, 497 { do_bad, SIGBUS, 0, "unknown 7" }, 498 }; 499 500 void __init hook_debug_fault_code(int nr, 501 int (*fn)(unsigned long, unsigned int, struct pt_regs *), 502 int sig, int code, const char *name) 503 { 504 BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info)); 505 506 debug_fault_info[nr].fn = fn; 507 debug_fault_info[nr].sig = sig; 508 debug_fault_info[nr].code = code; 509 debug_fault_info[nr].name = name; 510 } 511 512 asmlinkage int __exception do_debug_exception(unsigned long addr, 513 unsigned int esr, 514 struct pt_regs *regs) 515 { 516 const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr); 517 struct siginfo info; 518 519 if (!inf->fn(addr, esr, regs)) 520 return 1; 521 522 pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n", 523 inf->name, esr, addr); 524 525 info.si_signo = inf->sig; 526 info.si_errno = 0; 527 info.si_code = inf->code; 528 info.si_addr = (void __user *)addr; 529 arm64_notify_die("", regs, &info, 0); 530 531 return 0; 532 } 533