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 if (pud_none(*pud) || pud_bad(*pud)) 66 break; 67 68 pmd = pmd_offset(pud, addr); 69 printk(", *pmd=%016llx", pmd_val(*pmd)); 70 if (pmd_none(*pmd) || pmd_bad(*pmd)) 71 break; 72 73 pte = pte_offset_map(pmd, addr); 74 printk(", *pte=%016llx", pte_val(*pte)); 75 pte_unmap(pte); 76 } while(0); 77 78 printk("\n"); 79 } 80 81 /* 82 * The kernel tried to access some page that wasn't present. 83 */ 84 static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr, 85 unsigned int esr, struct pt_regs *regs) 86 { 87 /* 88 * Are we prepared to handle this kernel fault? 89 */ 90 if (fixup_exception(regs)) 91 return; 92 93 /* 94 * No handler, we'll have to terminate things with extreme prejudice. 95 */ 96 bust_spinlocks(1); 97 pr_alert("Unable to handle kernel %s at virtual address %08lx\n", 98 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 99 "paging request", addr); 100 101 show_pte(mm, addr); 102 die("Oops", regs, esr); 103 bust_spinlocks(0); 104 do_exit(SIGKILL); 105 } 106 107 /* 108 * Something tried to access memory that isn't in our memory map. User mode 109 * accesses just cause a SIGSEGV 110 */ 111 static void __do_user_fault(struct task_struct *tsk, unsigned long addr, 112 unsigned int esr, unsigned int sig, int code, 113 struct pt_regs *regs) 114 { 115 struct siginfo si; 116 117 if (show_unhandled_signals && unhandled_signal(tsk, sig) && 118 printk_ratelimit()) { 119 pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n", 120 tsk->comm, task_pid_nr(tsk), fault_name(esr), sig, 121 addr, esr); 122 show_pte(tsk->mm, addr); 123 show_regs(regs); 124 } 125 126 tsk->thread.fault_address = addr; 127 tsk->thread.fault_code = esr; 128 si.si_signo = sig; 129 si.si_errno = 0; 130 si.si_code = code; 131 si.si_addr = (void __user *)addr; 132 force_sig_info(sig, &si, tsk); 133 } 134 135 static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs) 136 { 137 struct task_struct *tsk = current; 138 struct mm_struct *mm = tsk->active_mm; 139 140 /* 141 * If we are in kernel mode at this point, we have no context to 142 * handle this fault with. 143 */ 144 if (user_mode(regs)) 145 __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs); 146 else 147 __do_kernel_fault(mm, addr, esr, regs); 148 } 149 150 #define VM_FAULT_BADMAP 0x010000 151 #define VM_FAULT_BADACCESS 0x020000 152 153 #define ESR_LNX_EXEC (1 << 24) 154 155 static int __do_page_fault(struct mm_struct *mm, unsigned long addr, 156 unsigned int mm_flags, unsigned long vm_flags, 157 struct task_struct *tsk) 158 { 159 struct vm_area_struct *vma; 160 int fault; 161 162 vma = find_vma(mm, addr); 163 fault = VM_FAULT_BADMAP; 164 if (unlikely(!vma)) 165 goto out; 166 if (unlikely(vma->vm_start > addr)) 167 goto check_stack; 168 169 /* 170 * Ok, we have a good vm_area for this memory access, so we can handle 171 * it. 172 */ 173 good_area: 174 /* 175 * Check that the permissions on the VMA allow for the fault which 176 * occurred. If we encountered a write or exec fault, we must have 177 * appropriate permissions, otherwise we allow any permission. 178 */ 179 if (!(vma->vm_flags & vm_flags)) { 180 fault = VM_FAULT_BADACCESS; 181 goto out; 182 } 183 184 return handle_mm_fault(mm, vma, addr & PAGE_MASK, mm_flags); 185 186 check_stack: 187 if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) 188 goto good_area; 189 out: 190 return fault; 191 } 192 193 static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 194 struct pt_regs *regs) 195 { 196 struct task_struct *tsk; 197 struct mm_struct *mm; 198 int fault, sig, code; 199 unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC; 200 unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 201 202 tsk = current; 203 mm = tsk->mm; 204 205 /* Enable interrupts if they were enabled in the parent context. */ 206 if (interrupts_enabled(regs)) 207 local_irq_enable(); 208 209 /* 210 * If we're in an interrupt or have no user context, we must not take 211 * the fault. 212 */ 213 if (in_atomic() || !mm) 214 goto no_context; 215 216 if (user_mode(regs)) 217 mm_flags |= FAULT_FLAG_USER; 218 219 if (esr & ESR_LNX_EXEC) { 220 vm_flags = VM_EXEC; 221 } else if ((esr & ESR_EL1_WRITE) && !(esr & ESR_EL1_CM)) { 222 vm_flags = VM_WRITE; 223 mm_flags |= FAULT_FLAG_WRITE; 224 } 225 226 /* 227 * As per x86, we may deadlock here. However, since the kernel only 228 * validly references user space from well defined areas of the code, 229 * we can bug out early if this is from code which shouldn't. 230 */ 231 if (!down_read_trylock(&mm->mmap_sem)) { 232 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 233 goto no_context; 234 retry: 235 down_read(&mm->mmap_sem); 236 } else { 237 /* 238 * The above down_read_trylock() might have succeeded in which 239 * case, we'll have missed the might_sleep() from down_read(). 240 */ 241 might_sleep(); 242 #ifdef CONFIG_DEBUG_VM 243 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 244 goto no_context; 245 #endif 246 } 247 248 fault = __do_page_fault(mm, addr, mm_flags, vm_flags, tsk); 249 250 /* 251 * If we need to retry but a fatal signal is pending, handle the 252 * signal first. We do not need to release the mmap_sem because it 253 * would already be released in __lock_page_or_retry in mm/filemap.c. 254 */ 255 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 256 return 0; 257 258 /* 259 * Major/minor page fault accounting is only done on the initial 260 * attempt. If we go through a retry, it is extremely likely that the 261 * page will be found in page cache at that point. 262 */ 263 264 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 265 if (mm_flags & FAULT_FLAG_ALLOW_RETRY) { 266 if (fault & VM_FAULT_MAJOR) { 267 tsk->maj_flt++; 268 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, 269 addr); 270 } else { 271 tsk->min_flt++; 272 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, 273 addr); 274 } 275 if (fault & VM_FAULT_RETRY) { 276 /* 277 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of 278 * starvation. 279 */ 280 mm_flags &= ~FAULT_FLAG_ALLOW_RETRY; 281 goto retry; 282 } 283 } 284 285 up_read(&mm->mmap_sem); 286 287 /* 288 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR 289 */ 290 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | 291 VM_FAULT_BADACCESS)))) 292 return 0; 293 294 /* 295 * If we are in kernel mode at this point, we have no context to 296 * handle this fault with. 297 */ 298 if (!user_mode(regs)) 299 goto no_context; 300 301 if (fault & VM_FAULT_OOM) { 302 /* 303 * We ran out of memory, call the OOM killer, and return to 304 * userspace (which will retry the fault, or kill us if we got 305 * oom-killed). 306 */ 307 pagefault_out_of_memory(); 308 return 0; 309 } 310 311 if (fault & VM_FAULT_SIGBUS) { 312 /* 313 * We had some memory, but were unable to successfully fix up 314 * this page fault. 315 */ 316 sig = SIGBUS; 317 code = BUS_ADRERR; 318 } else { 319 /* 320 * Something tried to access memory that isn't in our memory 321 * map. 322 */ 323 sig = SIGSEGV; 324 code = fault == VM_FAULT_BADACCESS ? 325 SEGV_ACCERR : SEGV_MAPERR; 326 } 327 328 __do_user_fault(tsk, addr, esr, sig, code, regs); 329 return 0; 330 331 no_context: 332 __do_kernel_fault(mm, addr, esr, regs); 333 return 0; 334 } 335 336 /* 337 * First Level Translation Fault Handler 338 * 339 * We enter here because the first level page table doesn't contain a valid 340 * entry for the address. 341 * 342 * If the address is in kernel space (>= TASK_SIZE), then we are probably 343 * faulting in the vmalloc() area. 344 * 345 * If the init_task's first level page tables contains the relevant entry, we 346 * copy the it to this task. If not, we send the process a signal, fixup the 347 * exception, or oops the kernel. 348 * 349 * NOTE! We MUST NOT take any locks for this case. We may be in an interrupt 350 * or a critical region, and should only copy the information from the master 351 * page table, nothing more. 352 */ 353 static int __kprobes do_translation_fault(unsigned long addr, 354 unsigned int esr, 355 struct pt_regs *regs) 356 { 357 if (addr < TASK_SIZE) 358 return do_page_fault(addr, esr, regs); 359 360 do_bad_area(addr, esr, regs); 361 return 0; 362 } 363 364 /* 365 * This abort handler always returns "fault". 366 */ 367 static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs) 368 { 369 return 1; 370 } 371 372 static struct fault_info { 373 int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs); 374 int sig; 375 int code; 376 const char *name; 377 } fault_info[] = { 378 { do_bad, SIGBUS, 0, "ttbr address size fault" }, 379 { do_bad, SIGBUS, 0, "level 1 address size fault" }, 380 { do_bad, SIGBUS, 0, "level 2 address size fault" }, 381 { do_bad, SIGBUS, 0, "level 3 address size fault" }, 382 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "input address range fault" }, 383 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" }, 384 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" }, 385 { do_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" }, 386 { do_bad, SIGBUS, 0, "reserved access flag fault" }, 387 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" }, 388 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" }, 389 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 access flag fault" }, 390 { do_bad, SIGBUS, 0, "reserved permission fault" }, 391 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" }, 392 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" }, 393 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" }, 394 { do_bad, SIGBUS, 0, "synchronous external abort" }, 395 { do_bad, SIGBUS, 0, "asynchronous external abort" }, 396 { do_bad, SIGBUS, 0, "unknown 18" }, 397 { do_bad, SIGBUS, 0, "unknown 19" }, 398 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 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 parity error" }, 403 { do_bad, SIGBUS, 0, "asynchronous parity error" }, 404 { do_bad, SIGBUS, 0, "unknown 26" }, 405 { do_bad, SIGBUS, 0, "unknown 27" }, 406 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 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, "unknown 32" }, 411 { do_bad, SIGBUS, BUS_ADRALN, "alignment fault" }, 412 { do_bad, SIGBUS, 0, "debug event" }, 413 { do_bad, SIGBUS, 0, "unknown 35" }, 414 { do_bad, SIGBUS, 0, "unknown 36" }, 415 { do_bad, SIGBUS, 0, "unknown 37" }, 416 { do_bad, SIGBUS, 0, "unknown 38" }, 417 { do_bad, SIGBUS, 0, "unknown 39" }, 418 { do_bad, SIGBUS, 0, "unknown 40" }, 419 { do_bad, SIGBUS, 0, "unknown 41" }, 420 { do_bad, SIGBUS, 0, "unknown 42" }, 421 { do_bad, SIGBUS, 0, "unknown 43" }, 422 { do_bad, SIGBUS, 0, "unknown 44" }, 423 { do_bad, SIGBUS, 0, "unknown 45" }, 424 { do_bad, SIGBUS, 0, "unknown 46" }, 425 { do_bad, SIGBUS, 0, "unknown 47" }, 426 { do_bad, SIGBUS, 0, "unknown 48" }, 427 { do_bad, SIGBUS, 0, "unknown 49" }, 428 { do_bad, SIGBUS, 0, "unknown 50" }, 429 { do_bad, SIGBUS, 0, "unknown 51" }, 430 { do_bad, SIGBUS, 0, "implementation fault (lockdown abort)" }, 431 { do_bad, SIGBUS, 0, "unknown 53" }, 432 { do_bad, SIGBUS, 0, "unknown 54" }, 433 { do_bad, SIGBUS, 0, "unknown 55" }, 434 { do_bad, SIGBUS, 0, "unknown 56" }, 435 { do_bad, SIGBUS, 0, "unknown 57" }, 436 { do_bad, SIGBUS, 0, "implementation fault (coprocessor abort)" }, 437 { do_bad, SIGBUS, 0, "unknown 59" }, 438 { do_bad, SIGBUS, 0, "unknown 60" }, 439 { do_bad, SIGBUS, 0, "unknown 61" }, 440 { do_bad, SIGBUS, 0, "unknown 62" }, 441 { do_bad, SIGBUS, 0, "unknown 63" }, 442 }; 443 444 static const char *fault_name(unsigned int esr) 445 { 446 const struct fault_info *inf = fault_info + (esr & 63); 447 return inf->name; 448 } 449 450 /* 451 * Dispatch a data abort to the relevant handler. 452 */ 453 asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr, 454 struct pt_regs *regs) 455 { 456 const struct fault_info *inf = fault_info + (esr & 63); 457 struct siginfo info; 458 459 if (!inf->fn(addr, esr, regs)) 460 return; 461 462 pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n", 463 inf->name, esr, addr); 464 465 info.si_signo = inf->sig; 466 info.si_errno = 0; 467 info.si_code = inf->code; 468 info.si_addr = (void __user *)addr; 469 arm64_notify_die("", regs, &info, esr); 470 } 471 472 /* 473 * Handle stack alignment exceptions. 474 */ 475 asmlinkage void __exception do_sp_pc_abort(unsigned long addr, 476 unsigned int esr, 477 struct pt_regs *regs) 478 { 479 struct siginfo info; 480 481 info.si_signo = SIGBUS; 482 info.si_errno = 0; 483 info.si_code = BUS_ADRALN; 484 info.si_addr = (void __user *)addr; 485 arm64_notify_die("", regs, &info, esr); 486 } 487 488 static struct fault_info debug_fault_info[] = { 489 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware breakpoint" }, 490 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware single-step" }, 491 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware watchpoint" }, 492 { do_bad, SIGBUS, 0, "unknown 3" }, 493 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch32 BKPT" }, 494 { do_bad, SIGTRAP, 0, "aarch32 vector catch" }, 495 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch64 BRK" }, 496 { do_bad, SIGBUS, 0, "unknown 7" }, 497 }; 498 499 void __init hook_debug_fault_code(int nr, 500 int (*fn)(unsigned long, unsigned int, struct pt_regs *), 501 int sig, int code, const char *name) 502 { 503 BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info)); 504 505 debug_fault_info[nr].fn = fn; 506 debug_fault_info[nr].sig = sig; 507 debug_fault_info[nr].code = code; 508 debug_fault_info[nr].name = name; 509 } 510 511 asmlinkage int __exception do_debug_exception(unsigned long addr, 512 unsigned int esr, 513 struct pt_regs *regs) 514 { 515 const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr); 516 struct siginfo info; 517 518 if (!inf->fn(addr, esr, regs)) 519 return 1; 520 521 pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n", 522 inf->name, esr, addr); 523 524 info.si_signo = inf->sig; 525 info.si_errno = 0; 526 info.si_code = inf->code; 527 info.si_addr = (void __user *)addr; 528 arm64_notify_die("", regs, &info, 0); 529 530 return 0; 531 } 532