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/cpufeature.h>
  34 #include <asm/exception.h>
  35 #include <asm/debug-monitors.h>
  36 #include <asm/esr.h>
  37 #include <asm/sysreg.h>
  38 #include <asm/system_misc.h>
  39 #include <asm/pgtable.h>
  40 #include <asm/tlbflush.h>
  41
  42 static const char *fault_name(unsigned int esr);
  43
  44 /*
  45  * Dump out the page tables associated with 'addr' in mm 'mm'.
  46  */
  47 void show_pte(struct mm_struct *mm, unsigned long addr)
  48 {
  49         pgd_t *pgd;
  50
  51         if (!mm)
  52                 mm = &init_mm;
  53
  54         pr_alert("pgd = %p\n", mm->pgd);
  55         pgd = pgd_offset(mm, addr);
  56         pr_alert("[%08lx] *pgd=%016llx", addr, pgd_val(*pgd));
  57
  58         do {
  59                 pud_t *pud;
  60                 pmd_t *pmd;
  61                 pte_t *pte;
  62
  63                 if (pgd_none(*pgd) || pgd_bad(*pgd))
  64                         break;
  65
  66                 pud = pud_offset(pgd, addr);
  67                 printk(", *pud=%016llx", pud_val(*pud));
  68                 if (pud_none(*pud) || pud_bad(*pud))
  69                         break;
  70
  71                 pmd = pmd_offset(pud, addr);
  72                 printk(", *pmd=%016llx", pmd_val(*pmd));
  73                 if (pmd_none(*pmd) || pmd_bad(*pmd))
  74                         break;
  75
  76                 pte = pte_offset_map(pmd, addr);
  77                 printk(", *pte=%016llx", pte_val(*pte));
  78                 pte_unmap(pte);
  79         } while(0);
  80
  81         printk("\n");
  82 }
  83
  84 /*
  85  * The kernel tried to access some page that wasn't present.
  86  */
  87 static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr,
  88                               unsigned int esr, struct pt_regs *regs)
  89 {
  90         /*
  91          * Are we prepared to handle this kernel fault?
  92          */
  93         if (fixup_exception(regs))
  94                 return;
  95
  96         /*
  97          * No handler, we'll have to terminate things with extreme prejudice.
  98          */
  99         bust_spinlocks(1);
 100         pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
 101                  (addr < PAGE_SIZE) ? "NULL pointer dereference" :
 102                  "paging request", addr);
 103
 104         show_pte(mm, addr);
 105         die("Oops", regs, esr);
 106         bust_spinlocks(0);
 107         do_exit(SIGKILL);
 108 }
 109
 110 /*
 111  * Something tried to access memory that isn't in our memory map. User mode
 112  * accesses just cause a SIGSEGV
 113  */
 114 static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
 115                             unsigned int esr, unsigned int sig, int code,
 116                             struct pt_regs *regs)
 117 {
 118         struct siginfo si;
 119
 120         if (unhandled_signal(tsk, sig) && show_unhandled_signals_ratelimited()) {
 121                 pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n",
 122                         tsk->comm, task_pid_nr(tsk), fault_name(esr), sig,
 123                         addr, esr);
 124                 show_pte(tsk->mm, addr);
 125                 show_regs(regs);
 126         }
 127
 128         tsk->thread.fault_address = addr;
 129         tsk->thread.fault_code = esr;
 130         si.si_signo = sig;
 131         si.si_errno = 0;
 132         si.si_code = code;
 133         si.si_addr = (void __user *)addr;
 134         force_sig_info(sig, &si, tsk);
 135 }
 136
 137 static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs)
 138 {
 139         struct task_struct *tsk = current;
 140         struct mm_struct *mm = tsk->active_mm;
 141
 142         /*
 143          * If we are in kernel mode at this point, we have no context to
 144          * handle this fault with.
 145          */
 146         if (user_mode(regs))
 147                 __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs);
 148         else
 149                 __do_kernel_fault(mm, addr, esr, regs);
 150 }
 151
 152 #define VM_FAULT_BADMAP         0x010000
 153 #define VM_FAULT_BADACCESS      0x020000
 154
 155 #define ESR_LNX_EXEC            (1 << 24)
 156
 157 static int __do_page_fault(struct mm_struct *mm, unsigned long addr,
 158                            unsigned int mm_flags, unsigned long vm_flags,
 159                            struct task_struct *tsk)
 160 {
 161         struct vm_area_struct *vma;
 162         int fault;
 163
 164         vma = find_vma(mm, addr);
 165         fault = VM_FAULT_BADMAP;
 166         if (unlikely(!vma))
 167                 goto out;
 168         if (unlikely(vma->vm_start > addr))
 169                 goto check_stack;
 170
 171         /*
 172          * Ok, we have a good vm_area for this memory access, so we can handle
 173          * it.
 174          */
 175 good_area:
 176         /*
 177          * Check that the permissions on the VMA allow for the fault which
 178          * occurred. If we encountered a write or exec fault, we must have
 179          * appropriate permissions, otherwise we allow any permission.
 180          */
 181         if (!(vma->vm_flags & vm_flags)) {
 182                 fault = VM_FAULT_BADACCESS;
 183                 goto out;
 184         }
 185
 186         return handle_mm_fault(mm, vma, addr & PAGE_MASK, mm_flags);
 187
 188 check_stack:
 189         if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 190                 goto good_area;
 191 out:
 192         return fault;
 193 }
 194
 195 static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 196                                    struct pt_regs *regs)
 197 {
 198         struct task_struct *tsk;
 199         struct mm_struct *mm;
 200         int fault, sig, code;
 201         unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC;
 202         unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 203
 204         tsk = current;
 205         mm  = tsk->mm;
 206
 207         /* Enable interrupts if they were enabled in the parent context. */
 208         if (interrupts_enabled(regs))
 209                 local_irq_enable();
 210
 211         /*
 212          * If we're in an interrupt or have no user context, we must not take
 213          * the fault.
 214          */
 215         if (faulthandler_disabled() || !mm)
 216                 goto no_context;
 217
 218         if (user_mode(regs))
 219                 mm_flags |= FAULT_FLAG_USER;
 220
 221         if (esr & ESR_LNX_EXEC) {
 222                 vm_flags = VM_EXEC;
 223         } else if ((esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM)) {
 224                 vm_flags = VM_WRITE;
 225                 mm_flags |= FAULT_FLAG_WRITE;
 226         }
 227
 228         /*
 229          * PAN bit set implies the fault happened in kernel space, but not
 230          * in the arch's user access functions.
 231          */
 232         if (IS_ENABLED(CONFIG_ARM64_PAN) && (regs->pstate & PSR_PAN_BIT))
 233                 goto no_context;
 234
 235         /*
 236          * As per x86, we may deadlock here. However, since the kernel only
 237          * validly references user space from well defined areas of the code,
 238          * we can bug out early if this is from code which shouldn't.
 239          */
 240         if (!down_read_trylock(&mm->mmap_sem)) {
 241                 if (!user_mode(regs) && !search_exception_tables(regs->pc))
 242                         goto no_context;
 243 retry:
 244                 down_read(&mm->mmap_sem);
 245         } else {
 246                 /*
 247                  * The above down_read_trylock() might have succeeded in which
 248                  * case, we'll have missed the might_sleep() from down_read().
 249                  */
 250                 might_sleep();
 251 #ifdef CONFIG_DEBUG_VM
 252                 if (!user_mode(regs) && !search_exception_tables(regs->pc))
 253                         goto no_context;
 254 #endif
 255         }
 256
 257         fault = __do_page_fault(mm, addr, mm_flags, vm_flags, tsk);
 258
 259         /*
 260          * If we need to retry but a fatal signal is pending, handle the
 261          * signal first. We do not need to release the mmap_sem because it
 262          * would already be released in __lock_page_or_retry in mm/filemap.c.
 263          */
 264         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 265                 return 0;
 266
 267         /*
 268          * Major/minor page fault accounting is only done on the initial
 269          * attempt. If we go through a retry, it is extremely likely that the
 270          * page will be found in page cache at that point.
 271          */
 272
 273         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 274         if (mm_flags & FAULT_FLAG_ALLOW_RETRY) {
 275                 if (fault & VM_FAULT_MAJOR) {
 276                         tsk->maj_flt++;
 277                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs,
 278                                       addr);
 279                 } else {
 280                         tsk->min_flt++;
 281                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs,
 282                                       addr);
 283                 }
 284                 if (fault & VM_FAULT_RETRY) {
 285                         /*
 286                          * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of
 287                          * starvation.
 288                          */
 289                         mm_flags &= ~FAULT_FLAG_ALLOW_RETRY;
 290                         mm_flags |= FAULT_FLAG_TRIED;
 291                         goto retry;
 292                 }
 293         }
 294
 295         up_read(&mm->mmap_sem);
 296
 297         /*
 298          * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
 299          */
 300         if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP |
 301                               VM_FAULT_BADACCESS))))
 302                 return 0;
 303
 304         /*
 305          * If we are in kernel mode at this point, we have no context to
 306          * handle this fault with.
 307          */
 308         if (!user_mode(regs))
 309                 goto no_context;
 310
 311         if (fault & VM_FAULT_OOM) {
 312                 /*
 313                  * We ran out of memory, call the OOM killer, and return to
 314                  * userspace (which will retry the fault, or kill us if we got
 315                  * oom-killed).
 316                  */
 317                 pagefault_out_of_memory();
 318                 return 0;
 319         }
 320
 321         if (fault & VM_FAULT_SIGBUS) {
 322                 /*
 323                  * We had some memory, but were unable to successfully fix up
 324                  * this page fault.
 325                  */
 326                 sig = SIGBUS;
 327                 code = BUS_ADRERR;
 328         } else {
 329                 /*
 330                  * Something tried to access memory that isn't in our memory
 331                  * map.
 332                  */
 333                 sig = SIGSEGV;
 334                 code = fault == VM_FAULT_BADACCESS ?
 335                         SEGV_ACCERR : SEGV_MAPERR;
 336         }
 337
 338         __do_user_fault(tsk, addr, esr, sig, code, regs);
 339         return 0;
 340
 341 no_context:
 342         __do_kernel_fault(mm, addr, esr, regs);
 343         return 0;
 344 }
 345
 346 /*
 347  * First Level Translation Fault Handler
 348  *
 349  * We enter here because the first level page table doesn't contain a valid
 350  * entry for the address.
 351  *
 352  * If the address is in kernel space (>= TASK_SIZE), then we are probably
 353  * faulting in the vmalloc() area.
 354  *
 355  * If the init_task's first level page tables contains the relevant entry, we
 356  * copy the it to this task.  If not, we send the process a signal, fixup the
 357  * exception, or oops the kernel.
 358  *
 359  * NOTE! We MUST NOT take any locks for this case. We may be in an interrupt
 360  * or a critical region, and should only copy the information from the master
 361  * page table, nothing more.
 362  */
 363 static int __kprobes do_translation_fault(unsigned long addr,
 364                                           unsigned int esr,
 365                                           struct pt_regs *regs)
 366 {
 367         if (addr < TASK_SIZE)
 368                 return do_page_fault(addr, esr, regs);
 369
 370         do_bad_area(addr, esr, regs);
 371         return 0;
 372 }
 373
 374 /*
 375  * This abort handler always returns "fault".
 376  */
 377 static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs)
 378 {
 379         return 1;
 380 }
 381
 382 static struct fault_info {
 383         int     (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs);
 384         int     sig;
 385         int     code;
 386         const char *name;
 387 } fault_info[] = {
 388         { do_bad,               SIGBUS,  0,             "ttbr address size fault"       },
 389         { do_bad,               SIGBUS,  0,             "level 1 address size fault"    },
 390         { do_bad,               SIGBUS,  0,             "level 2 address size fault"    },
 391         { do_bad,               SIGBUS,  0,             "level 3 address size fault"    },
 392         { do_translation_fault, SIGSEGV, SEGV_MAPERR,   "level 0 translation fault"     },
 393         { do_translation_fault, SIGSEGV, SEGV_MAPERR,   "level 1 translation fault"     },
 394         { do_translation_fault, SIGSEGV, SEGV_MAPERR,   "level 2 translation fault"     },
 395         { do_page_fault,        SIGSEGV, SEGV_MAPERR,   "level 3 translation fault"     },
 396         { do_bad,               SIGBUS,  0,             "unknown 8"                     },
 397         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 1 access flag fault"     },
 398         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 2 access flag fault"     },
 399         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 3 access flag fault"     },
 400         { do_bad,               SIGBUS,  0,             "unknown 12"                    },
 401         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 1 permission fault"      },
 402         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 2 permission fault"      },
 403         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 3 permission fault"      },
 404         { do_bad,               SIGBUS,  0,             "synchronous external abort"    },
 405         { do_bad,               SIGBUS,  0,             "unknown 17"                    },
 406         { do_bad,               SIGBUS,  0,             "unknown 18"                    },
 407         { do_bad,               SIGBUS,  0,             "unknown 19"                    },
 408         { do_bad,               SIGBUS,  0,             "synchronous abort (translation table walk)" },
 409         { do_bad,               SIGBUS,  0,             "synchronous abort (translation table walk)" },
 410         { do_bad,               SIGBUS,  0,             "synchronous abort (translation table walk)" },
 411         { do_bad,               SIGBUS,  0,             "synchronous abort (translation table walk)" },
 412         { do_bad,               SIGBUS,  0,             "synchronous parity error"      },
 413         { do_bad,               SIGBUS,  0,             "unknown 25"                    },
 414         { do_bad,               SIGBUS,  0,             "unknown 26"                    },
 415         { do_bad,               SIGBUS,  0,             "unknown 27"                    },
 416         { do_bad,               SIGBUS,  0,             "synchronous parity error (translation table walk)" },
 417         { do_bad,               SIGBUS,  0,             "synchronous parity error (translation table walk)" },
 418         { do_bad,               SIGBUS,  0,             "synchronous parity error (translation table walk)" },
 419         { do_bad,               SIGBUS,  0,             "synchronous parity error (translation table walk)" },
 420         { do_bad,               SIGBUS,  0,             "unknown 32"                    },
 421         { do_bad,               SIGBUS,  BUS_ADRALN,    "alignment fault"               },
 422         { do_bad,               SIGBUS,  0,             "unknown 34"                    },
 423         { do_bad,               SIGBUS,  0,             "unknown 35"                    },
 424         { do_bad,               SIGBUS,  0,             "unknown 36"                    },
 425         { do_bad,               SIGBUS,  0,             "unknown 37"                    },
 426         { do_bad,               SIGBUS,  0,             "unknown 38"                    },
 427         { do_bad,               SIGBUS,  0,             "unknown 39"                    },
 428         { do_bad,               SIGBUS,  0,             "unknown 40"                    },
 429         { do_bad,               SIGBUS,  0,             "unknown 41"                    },
 430         { do_bad,               SIGBUS,  0,             "unknown 42"                    },
 431         { do_bad,               SIGBUS,  0,             "unknown 43"                    },
 432         { do_bad,               SIGBUS,  0,             "unknown 44"                    },
 433         { do_bad,               SIGBUS,  0,             "unknown 45"                    },
 434         { do_bad,               SIGBUS,  0,             "unknown 46"                    },
 435         { do_bad,               SIGBUS,  0,             "unknown 47"                    },
 436         { do_bad,               SIGBUS,  0,             "TLB conflict abort"            },
 437         { do_bad,               SIGBUS,  0,             "unknown 49"                    },
 438         { do_bad,               SIGBUS,  0,             "unknown 50"                    },
 439         { do_bad,               SIGBUS,  0,             "unknown 51"                    },
 440         { do_bad,               SIGBUS,  0,             "implementation fault (lockdown abort)" },
 441         { do_bad,               SIGBUS,  0,             "implementation fault (unsupported exclusive)" },
 442         { do_bad,               SIGBUS,  0,             "unknown 54"                    },
 443         { do_bad,               SIGBUS,  0,             "unknown 55"                    },
 444         { do_bad,               SIGBUS,  0,             "unknown 56"                    },
 445         { do_bad,               SIGBUS,  0,             "unknown 57"                    },
 446         { do_bad,               SIGBUS,  0,             "unknown 58"                    },
 447         { do_bad,               SIGBUS,  0,             "unknown 59"                    },
 448         { do_bad,               SIGBUS,  0,             "unknown 60"                    },
 449         { do_bad,               SIGBUS,  0,             "section domain fault"          },
 450         { do_bad,               SIGBUS,  0,             "page domain fault"             },
 451         { do_bad,               SIGBUS,  0,             "unknown 63"                    },
 452 };
 453
 454 static const char *fault_name(unsigned int esr)
 455 {
 456         const struct fault_info *inf = fault_info + (esr & 63);
 457         return inf->name;
 458 }
 459
 460 /*
 461  * Dispatch a data abort to the relevant handler.
 462  */
 463 asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
 464                                          struct pt_regs *regs)
 465 {
 466         const struct fault_info *inf = fault_info + (esr & 63);
 467         struct siginfo info;
 468
 469         if (!inf->fn(addr, esr, regs))
 470                 return;
 471
 472         pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n",
 473                  inf->name, esr, addr);
 474
 475         info.si_signo = inf->sig;
 476         info.si_errno = 0;
 477         info.si_code  = inf->code;
 478         info.si_addr  = (void __user *)addr;
 479         arm64_notify_die("", regs, &info, esr);
 480 }
 481
 482 /*
 483  * Handle stack alignment exceptions.
 484  */
 485 asmlinkage void __exception do_sp_pc_abort(unsigned long addr,
 486                                            unsigned int esr,
 487                                            struct pt_regs *regs)
 488 {
 489         struct siginfo info;
 490         struct task_struct *tsk = current;
 491
 492         if (show_unhandled_signals && unhandled_signal(tsk, SIGBUS))
 493                 pr_info_ratelimited("%s[%d]: %s exception: pc=%p sp=%p\n",
 494                                     tsk->comm, task_pid_nr(tsk),
 495                                     esr_get_class_string(esr), (void *)regs->pc,
 496                                     (void *)regs->sp);
 497
 498         info.si_signo = SIGBUS;
 499         info.si_errno = 0;
 500         info.si_code  = BUS_ADRALN;
 501         info.si_addr  = (void __user *)addr;
 502         arm64_notify_die("Oops - SP/PC alignment exception", regs, &info, esr);
 503 }
 504
 505 int __init early_brk64(unsigned long addr, unsigned int esr,
 506                        struct pt_regs *regs);
 507
 508 /*
 509  * __refdata because early_brk64 is __init, but the reference to it is
 510  * clobbered at arch_initcall time.
 511  * See traps.c and debug-monitors.c:debug_traps_init().
 512  */
 513 static struct fault_info __refdata debug_fault_info[] = {
 514         { do_bad,       SIGTRAP,        TRAP_HWBKPT,    "hardware breakpoint"   },
 515         { do_bad,       SIGTRAP,        TRAP_HWBKPT,    "hardware single-step"  },
 516         { do_bad,       SIGTRAP,        TRAP_HWBKPT,    "hardware watchpoint"   },
 517         { do_bad,       SIGBUS,         0,              "unknown 3"             },
 518         { do_bad,       SIGTRAP,        TRAP_BRKPT,     "aarch32 BKPT"          },
 519         { do_bad,       SIGTRAP,        0,              "aarch32 vector catch"  },
 520         { early_brk64,  SIGTRAP,        TRAP_BRKPT,     "aarch64 BRK"           },
 521         { do_bad,       SIGBUS,         0,              "unknown 7"             },
 522 };
 523
 524 void __init hook_debug_fault_code(int nr,
 525                                   int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 526                                   int sig, int code, const char *name)
 527 {
 528         BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info));
 529
 530         debug_fault_info[nr].fn         = fn;
 531         debug_fault_info[nr].sig        = sig;
 532         debug_fault_info[nr].code       = code;
 533         debug_fault_info[nr].name       = name;
 534 }
 535
 536 asmlinkage int __exception do_debug_exception(unsigned long addr,
 537                                               unsigned int esr,
 538                                               struct pt_regs *regs)
 539 {
 540         const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr);
 541         struct siginfo info;
 542
 543         if (!inf->fn(addr, esr, regs))
 544                 return 1;
 545
 546         pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n",
 547                  inf->name, esr, addr);
 548
 549         info.si_signo = inf->sig;
 550         info.si_errno = 0;
 551         info.si_code  = inf->code;
 552         info.si_addr  = (void __user *)addr;
 553         arm64_notify_die("", regs, &info, 0);
 554
 555         return 0;
 556 }
 557
 558 #ifdef CONFIG_ARM64_PAN
 559 void cpu_enable_pan(void *__unused)
 560 {
 561         config_sctlr_el1(SCTLR_EL1_SPAN, 0);
 562 }
 563 #endif /* CONFIG_ARM64_PAN */