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