arch/arm64/mm/fault.c

   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 /*
 156  * Check that the permissions on the VMA allow for the fault which occurred.
 157  * If we encountered a write fault, we must have write permission, otherwise
 158  * we allow any permission.
 159  */
 160 static inline bool access_error(unsigned int esr, struct vm_area_struct *vma)
 161 {
 162         unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
 163
 164         if (esr & ESR_WRITE)
 165                 mask = VM_WRITE;
 166         if (esr & ESR_LNX_EXEC)
 167                 mask = VM_EXEC;
 168
 169         return vma->vm_flags & mask ? false : true;
 170 }
 171
 172 static int __do_page_fault(struct mm_struct *mm, unsigned long addr,
 173                            unsigned int esr, unsigned int flags,
 174                            struct task_struct *tsk)
 175 {
 176         struct vm_area_struct *vma;
 177         int fault;
 178
 179         vma = find_vma(mm, addr);
 180         fault = VM_FAULT_BADMAP;
 181         if (unlikely(!vma))
 182                 goto out;
 183         if (unlikely(vma->vm_start > addr))
 184                 goto check_stack;
 185
 186         /*
 187          * Ok, we have a good vm_area for this memory access, so we can handle
 188          * it.
 189          */
 190 good_area:
 191         if (access_error(esr, vma)) {
 192                 fault = VM_FAULT_BADACCESS;
 193                 goto out;
 194         }
 195
 196         return handle_mm_fault(mm, vma, addr & PAGE_MASK, flags);
 197
 198 check_stack:
 199         if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 200                 goto good_area;
 201 out:
 202         return fault;
 203 }
 204
 205 static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 206                                    struct pt_regs *regs)
 207 {
 208         struct task_struct *tsk;
 209         struct mm_struct *mm;
 210         int fault, sig, code;
 211         bool write = (esr & ESR_WRITE) && !(esr & ESR_CM);
 212         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
 213                 (write ? FAULT_FLAG_WRITE : 0);
 214
 215         tsk = current;
 216         mm  = tsk->mm;
 217
 218         /* Enable interrupts if they were enabled in the parent context. */
 219         if (interrupts_enabled(regs))
 220                 local_irq_enable();
 221
 222         /*
 223          * If we're in an interrupt or have no user context, we must not take
 224          * the fault.
 225          */
 226         if (in_atomic() || !mm)
 227                 goto no_context;
 228
 229         /*
 230          * As per x86, we may deadlock here. However, since the kernel only
 231          * validly references user space from well defined areas of the code,
 232          * we can bug out early if this is from code which shouldn't.
 233          */
 234         if (!down_read_trylock(&mm->mmap_sem)) {
 235                 if (!user_mode(regs) && !search_exception_tables(regs->pc))
 236                         goto no_context;
 237 retry:
 238                 down_read(&mm->mmap_sem);
 239         } else {
 240                 /*
 241                  * The above down_read_trylock() might have succeeded in which
 242                  * case, we'll have missed the might_sleep() from down_read().
 243                  */
 244                 might_sleep();
 245 #ifdef CONFIG_DEBUG_VM
 246                 if (!user_mode(regs) && !search_exception_tables(regs->pc))
 247                         goto no_context;
 248 #endif
 249         }
 250
 251         fault = __do_page_fault(mm, addr, esr, flags, tsk);
 252
 253         /*
 254          * If we need to retry but a fatal signal is pending, handle the
 255          * signal first. We do not need to release the mmap_sem because it
 256          * would already be released in __lock_page_or_retry in mm/filemap.c.
 257          */
 258         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 259                 return 0;
 260
 261         /*
 262          * Major/minor page fault accounting is only done on the initial
 263          * attempt. If we go through a retry, it is extremely likely that the
 264          * page will be found in page cache at that point.
 265          */
 266
 267         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 268         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 269                 if (fault & VM_FAULT_MAJOR) {
 270                         tsk->maj_flt++;
 271                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs,
 272                                       addr);
 273                 } else {
 274                         tsk->min_flt++;
 275                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs,
 276                                       addr);
 277                 }
 278                 if (fault & VM_FAULT_RETRY) {
 279                         /*
 280                          * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of
 281                          * starvation.
 282                          */
 283                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 284                         goto retry;
 285                 }
 286         }
 287
 288         up_read(&mm->mmap_sem);
 289
 290         /*
 291          * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
 292          */
 293         if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP |
 294                               VM_FAULT_BADACCESS))))
 295                 return 0;
 296
 297         if (fault & VM_FAULT_OOM) {
 298                 /*
 299                  * We ran out of memory, call the OOM killer, and return to
 300                  * userspace (which will retry the fault, or kill us if we got
 301                  * oom-killed).
 302                  */
 303                 pagefault_out_of_memory();
 304                 return 0;
 305         }
 306
 307         /*
 308          * If we are in kernel mode at this point, we have no context to
 309          * handle this fault with.
 310          */
 311         if (!user_mode(regs))
 312                 goto no_context;
 313
 314         if (fault & VM_FAULT_SIGBUS) {
 315                 /*
 316                  * We had some memory, but were unable to successfully fix up
 317                  * this page fault.
 318                  */
 319                 sig = SIGBUS;
 320                 code = BUS_ADRERR;
 321         } else {
 322                 /*
 323                  * Something tried to access memory that isn't in our memory
 324                  * map.
 325                  */
 326                 sig = SIGSEGV;
 327                 code = fault == VM_FAULT_BADACCESS ?
 328                         SEGV_ACCERR : SEGV_MAPERR;
 329         }
 330
 331         __do_user_fault(tsk, addr, esr, sig, code, regs);
 332         return 0;
 333
 334 no_context:
 335         __do_kernel_fault(mm, addr, esr, regs);
 336         return 0;
 337 }
 338
 339 /*
 340  * First Level Translation Fault Handler
 341  *
 342  * We enter here because the first level page table doesn't contain a valid
 343  * entry for the address.
 344  *
 345  * If the address is in kernel space (>= TASK_SIZE), then we are probably
 346  * faulting in the vmalloc() area.
 347  *
 348  * If the init_task's first level page tables contains the relevant entry, we
 349  * copy the it to this task.  If not, we send the process a signal, fixup the
 350  * exception, or oops the kernel.
 351  *
 352  * NOTE! We MUST NOT take any locks for this case. We may be in an interrupt
 353  * or a critical region, and should only copy the information from the master
 354  * page table, nothing more.
 355  */
 356 static int __kprobes do_translation_fault(unsigned long addr,
 357                                           unsigned int esr,
 358                                           struct pt_regs *regs)
 359 {
 360         if (addr < TASK_SIZE)
 361                 return do_page_fault(addr, esr, regs);
 362
 363         do_bad_area(addr, esr, regs);
 364         return 0;
 365 }
 366
 367 /*
 368  * Some section permission faults need to be handled gracefully.  They can
 369  * happen due to a __{get,put}_user during an oops.
 370  */
 371 static int do_sect_fault(unsigned long addr, unsigned int esr,
 372                          struct pt_regs *regs)
 373 {
 374         do_bad_area(addr, esr, regs);
 375         return 0;
 376 }
 377
 378 /*
 379  * This abort handler always returns "fault".
 380  */
 381 static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs)
 382 {
 383         return 1;
 384 }
 385
 386 static struct fault_info {
 387         int     (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs);
 388         int     sig;
 389         int     code;
 390         const char *name;
 391 } fault_info[] = {
 392         { do_bad,               SIGBUS,  0,             "ttbr address size fault"       },
 393         { do_bad,               SIGBUS,  0,             "level 1 address size fault"    },
 394         { do_bad,               SIGBUS,  0,             "level 2 address size fault"    },
 395         { do_bad,               SIGBUS,  0,             "level 3 address size fault"    },
 396         { do_translation_fault, SIGSEGV, SEGV_MAPERR,   "input address range fault"     },
 397         { do_translation_fault, SIGSEGV, SEGV_MAPERR,   "level 1 translation fault"     },
 398         { do_translation_fault, SIGSEGV, SEGV_MAPERR,   "level 2 translation fault"     },
 399         { do_page_fault,        SIGSEGV, SEGV_MAPERR,   "level 3 translation fault"     },
 400         { do_bad,               SIGBUS,  0,             "reserved access flag fault"    },
 401         { do_bad,               SIGSEGV, SEGV_ACCERR,   "level 1 access flag fault"     },
 402         { do_bad,               SIGSEGV, SEGV_ACCERR,   "level 2 access flag fault"     },
 403         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 3 access flag fault"     },
 404         { do_bad,               SIGBUS,  0,             "reserved permission fault"     },
 405         { do_bad,               SIGSEGV, SEGV_ACCERR,   "level 1 permission fault"      },
 406         { do_sect_fault,        SIGSEGV, SEGV_ACCERR,   "level 2 permission fault"      },
 407         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 3 permission fault"      },
 408         { do_bad,               SIGBUS,  0,             "synchronous external abort"    },
 409         { do_bad,               SIGBUS,  0,             "asynchronous external abort"   },
 410         { do_bad,               SIGBUS,  0,             "unknown 18"                    },
 411         { do_bad,               SIGBUS,  0,             "unknown 19"                    },
 412         { do_bad,               SIGBUS,  0,             "synchronous abort (translation table walk)" },
 413         { do_bad,               SIGBUS,  0,             "synchronous abort (translation table walk)" },
 414         { do_bad,               SIGBUS,  0,             "synchronous abort (translation table walk)" },
 415         { do_bad,               SIGBUS,  0,             "synchronous abort (translation table walk)" },
 416         { do_bad,               SIGBUS,  0,             "synchronous parity error"      },
 417         { do_bad,               SIGBUS,  0,             "asynchronous parity error"     },
 418         { do_bad,               SIGBUS,  0,             "unknown 26"                    },
 419         { do_bad,               SIGBUS,  0,             "unknown 27"                    },
 420         { do_bad,               SIGBUS,  0,             "synchronous parity error (translation table walk" },
 421         { do_bad,               SIGBUS,  0,             "synchronous parity error (translation table walk" },
 422         { do_bad,               SIGBUS,  0,             "synchronous parity error (translation table walk" },
 423         { do_bad,               SIGBUS,  0,             "synchronous parity error (translation table walk" },
 424         { do_bad,               SIGBUS,  0,             "unknown 32"                    },
 425         { do_bad,               SIGBUS,  BUS_ADRALN,    "alignment fault"               },
 426         { do_bad,               SIGBUS,  0,             "debug event"                   },
 427         { do_bad,               SIGBUS,  0,             "unknown 35"                    },
 428         { do_bad,               SIGBUS,  0,             "unknown 36"                    },
 429         { do_bad,               SIGBUS,  0,             "unknown 37"                    },
 430         { do_bad,               SIGBUS,  0,             "unknown 38"                    },
 431         { do_bad,               SIGBUS,  0,             "unknown 39"                    },
 432         { do_bad,               SIGBUS,  0,             "unknown 40"                    },
 433         { do_bad,               SIGBUS,  0,             "unknown 41"                    },
 434         { do_bad,               SIGBUS,  0,             "unknown 42"                    },
 435         { do_bad,               SIGBUS,  0,             "unknown 43"                    },
 436         { do_bad,               SIGBUS,  0,             "unknown 44"                    },
 437         { do_bad,               SIGBUS,  0,             "unknown 45"                    },
 438         { do_bad,               SIGBUS,  0,             "unknown 46"                    },
 439         { do_bad,               SIGBUS,  0,             "unknown 47"                    },
 440         { do_bad,               SIGBUS,  0,             "unknown 48"                    },
 441         { do_bad,               SIGBUS,  0,             "unknown 49"                    },
 442         { do_bad,               SIGBUS,  0,             "unknown 50"                    },
 443         { do_bad,               SIGBUS,  0,             "unknown 51"                    },
 444         { do_bad,               SIGBUS,  0,             "implementation fault (lockdown abort)" },
 445         { do_bad,               SIGBUS,  0,             "unknown 53"                    },
 446         { do_bad,               SIGBUS,  0,             "unknown 54"                    },
 447         { do_bad,               SIGBUS,  0,             "unknown 55"                    },
 448         { do_bad,               SIGBUS,  0,             "unknown 56"                    },
 449         { do_bad,               SIGBUS,  0,             "unknown 57"                    },
 450         { do_bad,               SIGBUS,  0,             "implementation fault (coprocessor abort)" },
 451         { do_bad,               SIGBUS,  0,             "unknown 59"                    },
 452         { do_bad,               SIGBUS,  0,             "unknown 60"                    },
 453         { do_bad,               SIGBUS,  0,             "unknown 61"                    },
 454         { do_bad,               SIGBUS,  0,             "unknown 62"                    },
 455         { do_bad,               SIGBUS,  0,             "unknown 63"                    },
 456 };
 457
 458 static const char *fault_name(unsigned int esr)
 459 {
 460         const struct fault_info *inf = fault_info + (esr & 63);
 461         return inf->name;
 462 }
 463
 464 /*
 465  * Dispatch a data abort to the relevant handler.
 466  */
 467 asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
 468                                          struct pt_regs *regs)
 469 {
 470         const struct fault_info *inf = fault_info + (esr & 63);
 471         struct siginfo info;
 472
 473         if (!inf->fn(addr, esr, regs))
 474                 return;
 475
 476         pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n",
 477                  inf->name, esr, addr);
 478
 479         info.si_signo = inf->sig;
 480         info.si_errno = 0;
 481         info.si_code  = inf->code;
 482         info.si_addr  = (void __user *)addr;
 483         arm64_notify_die("", regs, &info, esr);
 484 }
 485
 486 /*
 487  * Handle stack alignment exceptions.
 488  */
 489 asmlinkage void __exception do_sp_pc_abort(unsigned long addr,
 490                                            unsigned int esr,
 491                                            struct pt_regs *regs)
 492 {
 493         struct siginfo info;
 494
 495         info.si_signo = SIGBUS;
 496         info.si_errno = 0;
 497         info.si_code  = BUS_ADRALN;
 498         info.si_addr  = (void __user *)addr;
 499         arm64_notify_die("", regs, &info, esr);
 500 }
 501
 502 static struct fault_info debug_fault_info[] = {
 503         { do_bad,       SIGTRAP,        TRAP_HWBKPT,    "hardware breakpoint"   },
 504         { do_bad,       SIGTRAP,        TRAP_HWBKPT,    "hardware single-step"  },
 505         { do_bad,       SIGTRAP,        TRAP_HWBKPT,    "hardware watchpoint"   },
 506         { do_bad,       SIGBUS,         0,              "unknown 3"             },
 507         { do_bad,       SIGTRAP,        TRAP_BRKPT,     "aarch32 BKPT"          },
 508         { do_bad,       SIGTRAP,        0,              "aarch32 vector catch"  },
 509         { do_bad,       SIGTRAP,        TRAP_BRKPT,     "aarch64 BRK"           },
 510         { do_bad,       SIGBUS,         0,              "unknown 7"             },
 511 };
 512
 513 void __init hook_debug_fault_code(int nr,
 514                                   int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 515                                   int sig, int code, const char *name)
 516 {
 517         BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info));
 518
 519         debug_fault_info[nr].fn         = fn;
 520         debug_fault_info[nr].sig        = sig;
 521         debug_fault_info[nr].code       = code;
 522         debug_fault_info[nr].name       = name;
 523 }
 524
 525 asmlinkage int __exception do_debug_exception(unsigned long addr,
 526                                               unsigned int esr,
 527                                               struct pt_regs *regs)
 528 {
 529         const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr);
 530         struct siginfo info;
 531
 532         if (!inf->fn(addr, esr, regs))
 533                 return 1;
 534
 535         pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n",
 536                  inf->name, esr, addr);
 537
 538         info.si_signo = inf->sig;
 539         info.si_errno = 0;
 540         info.si_code  = inf->code;
 541         info.si_addr  = (void __user *)addr;
 542         arm64_notify_die("", regs, &info, esr);
 543
 544         return 0;
 545 }