kernel/arch/sh/mm/fault.c

   1 /*
   2  * Page fault handler for SH with an MMU.
   3  *
   4  *  Copyright (C) 1999  Niibe Yutaka
   5  *  Copyright (C) 2003 - 2012  Paul Mundt
   6  *
   7  *  Based on linux/arch/i386/mm/fault.c:
   8  *   Copyright (C) 1995  Linus Torvalds
   9  *
  10  * This file is subject to the terms and conditions of the GNU General Public
  11  * License.  See the file "COPYING" in the main directory of this archive
  12  * for more details.
  13  */
  14 #include <linux/kernel.h>
  15 #include <linux/mm.h>
  16 #include <linux/hardirq.h>
  17 #include <linux/kprobes.h>
  18 #include <linux/perf_event.h>
  19 #include <linux/kdebug.h>
  20 #include <linux/uaccess.h>
  21 #include <asm/io_trapped.h>
  22 #include <asm/mmu_context.h>
  23 #include <asm/tlbflush.h>
  24 #include <asm/traps.h>
  25
  26 static inline int notify_page_fault(struct pt_regs *regs, int trap)
  27 {
  28         int ret = 0;
  29
  30         if (kprobes_built_in() && !user_mode(regs)) {
  31                 preempt_disable();
  32                 if (kprobe_running() && kprobe_fault_handler(regs, trap))
  33                         ret = 1;
  34                 preempt_enable();
  35         }
  36
  37         return ret;
  38 }
  39
  40 static void
  41 force_sig_info_fault(int si_signo, int si_code, unsigned long address,
  42                      struct task_struct *tsk)
  43 {
  44         siginfo_t info;
  45
  46         info.si_signo   = si_signo;
  47         info.si_errno   = 0;
  48         info.si_code    = si_code;
  49         info.si_addr    = (void __user *)address;
  50
  51         force_sig_info(si_signo, &info, tsk);
  52 }
  53
  54 /*
  55  * This is useful to dump out the page tables associated with
  56  * 'addr' in mm 'mm'.
  57  */
  58 static void show_pte(struct mm_struct *mm, unsigned long addr)
  59 {
  60         pgd_t *pgd;
  61
  62         if (mm) {
  63                 pgd = mm->pgd;
  64         } else {
  65                 pgd = get_TTB();
  66
  67                 if (unlikely(!pgd))
  68                         pgd = swapper_pg_dir;
  69         }
  70
  71         printk(KERN_ALERT "pgd = %p\n", pgd);
  72         pgd += pgd_index(addr);
  73         printk(KERN_ALERT "[%08lx] *pgd=%0*Lx", addr,
  74                (u32)(sizeof(*pgd) * 2), (u64)pgd_val(*pgd));
  75
  76         do {
  77                 pud_t *pud;
  78                 pmd_t *pmd;
  79                 pte_t *pte;
  80
  81                 if (pgd_none(*pgd))
  82                         break;
  83
  84                 if (pgd_bad(*pgd)) {
  85                         printk("(bad)");
  86                         break;
  87                 }
  88
  89                 pud = pud_offset(pgd, addr);
  90                 if (PTRS_PER_PUD != 1)
  91                         printk(", *pud=%0*Lx", (u32)(sizeof(*pud) * 2),
  92                                (u64)pud_val(*pud));
  93
  94                 if (pud_none(*pud))
  95                         break;
  96
  97                 if (pud_bad(*pud)) {
  98                         printk("(bad)");
  99                         break;
 100                 }
 101
 102                 pmd = pmd_offset(pud, addr);
 103                 if (PTRS_PER_PMD != 1)
 104                         printk(", *pmd=%0*Lx", (u32)(sizeof(*pmd) * 2),
 105                                (u64)pmd_val(*pmd));
 106
 107                 if (pmd_none(*pmd))
 108                         break;
 109
 110                 if (pmd_bad(*pmd)) {
 111                         printk("(bad)");
 112                         break;
 113                 }
 114
 115                 /* We must not map this if we have highmem enabled */
 116                 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
 117                         break;
 118
 119                 pte = pte_offset_kernel(pmd, addr);
 120                 printk(", *pte=%0*Lx", (u32)(sizeof(*pte) * 2),
 121                        (u64)pte_val(*pte));
 122         } while (0);
 123
 124         printk("\n");
 125 }
 126
 127 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
 128 {
 129         unsigned index = pgd_index(address);
 130         pgd_t *pgd_k;
 131         pud_t *pud, *pud_k;
 132         pmd_t *pmd, *pmd_k;
 133
 134         pgd += index;
 135         pgd_k = init_mm.pgd + index;
 136
 137         if (!pgd_present(*pgd_k))
 138                 return NULL;
 139
 140         pud = pud_offset(pgd, address);
 141         pud_k = pud_offset(pgd_k, address);
 142         if (!pud_present(*pud_k))
 143                 return NULL;
 144
 145         if (!pud_present(*pud))
 146             set_pud(pud, *pud_k);
 147
 148         pmd = pmd_offset(pud, address);
 149         pmd_k = pmd_offset(pud_k, address);
 150         if (!pmd_present(*pmd_k))
 151                 return NULL;
 152
 153         if (!pmd_present(*pmd))
 154                 set_pmd(pmd, *pmd_k);
 155         else {
 156                 /*
 157                  * The page tables are fully synchronised so there must
 158                  * be another reason for the fault. Return NULL here to
 159                  * signal that we have not taken care of the fault.
 160                  */
 161                 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
 162                 return NULL;
 163         }
 164
 165         return pmd_k;
 166 }
 167
 168 #ifdef CONFIG_SH_STORE_QUEUES
 169 #define __FAULT_ADDR_LIMIT      P3_ADDR_MAX
 170 #else
 171 #define __FAULT_ADDR_LIMIT      VMALLOC_END
 172 #endif
 173
 174 /*
 175  * Handle a fault on the vmalloc or module mapping area
 176  */
 177 static noinline int vmalloc_fault(unsigned long address)
 178 {
 179         pgd_t *pgd_k;
 180         pmd_t *pmd_k;
 181         pte_t *pte_k;
 182
 183         /* Make sure we are in vmalloc/module/P3 area: */
 184         if (!(address >= VMALLOC_START && address < __FAULT_ADDR_LIMIT))
 185                 return -1;
 186
 187         /*
 188          * Synchronize this task's top level page-table
 189          * with the 'reference' page table.
 190          *
 191          * Do _not_ use "current" here. We might be inside
 192          * an interrupt in the middle of a task switch..
 193          */
 194         pgd_k = get_TTB();
 195         pmd_k = vmalloc_sync_one(pgd_k, address);
 196         if (!pmd_k)
 197                 return -1;
 198
 199         pte_k = pte_offset_kernel(pmd_k, address);
 200         if (!pte_present(*pte_k))
 201                 return -1;
 202
 203         return 0;
 204 }
 205
 206 static void
 207 show_fault_oops(struct pt_regs *regs, unsigned long address)
 208 {
 209         if (!oops_may_print())
 210                 return;
 211
 212         printk(KERN_ALERT "BUG: unable to handle kernel ");
 213         if (address < PAGE_SIZE)
 214                 printk(KERN_CONT "NULL pointer dereference");
 215         else
 216                 printk(KERN_CONT "paging request");
 217
 218         printk(KERN_CONT " at %08lx\n", address);
 219         printk(KERN_ALERT "PC:");
 220         printk_address(regs->pc, 1);
 221
 222         show_pte(NULL, address);
 223 }
 224
 225 static noinline void
 226 no_context(struct pt_regs *regs, unsigned long error_code,
 227            unsigned long address)
 228 {
 229         /* Are we prepared to handle this kernel fault?  */
 230         if (fixup_exception(regs))
 231                 return;
 232
 233         if (handle_trapped_io(regs, address))
 234                 return;
 235
 236         /*
 237          * Oops. The kernel tried to access some bad page. We'll have to
 238          * terminate things with extreme prejudice.
 239          */
 240         bust_spinlocks(1);
 241
 242         show_fault_oops(regs, address);
 243
 244         die("Oops", regs, error_code);
 245         bust_spinlocks(0);
 246         do_exit(SIGKILL);
 247 }
 248
 249 static void
 250 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 251                        unsigned long address, int si_code)
 252 {
 253         struct task_struct *tsk = current;
 254
 255         /* User mode accesses just cause a SIGSEGV */
 256         if (user_mode(regs)) {
 257                 /*
 258                  * It's possible to have interrupts off here:
 259                  */
 260                 local_irq_enable();
 261
 262                 force_sig_info_fault(SIGSEGV, si_code, address, tsk);
 263
 264                 return;
 265         }
 266
 267         no_context(regs, error_code, address);
 268 }
 269
 270 static noinline void
 271 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 272                      unsigned long address)
 273 {
 274         __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
 275 }
 276
 277 static void
 278 __bad_area(struct pt_regs *regs, unsigned long error_code,
 279            unsigned long address, int si_code)
 280 {
 281         struct mm_struct *mm = current->mm;
 282
 283         /*
 284          * Something tried to access memory that isn't in our memory map..
 285          * Fix it, but check if it's kernel or user first..
 286          */
 287         up_read(&mm->mmap_sem);
 288
 289         __bad_area_nosemaphore(regs, error_code, address, si_code);
 290 }
 291
 292 static noinline void
 293 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 294 {
 295         __bad_area(regs, error_code, address, SEGV_MAPERR);
 296 }
 297
 298 static noinline void
 299 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
 300                       unsigned long address)
 301 {
 302         __bad_area(regs, error_code, address, SEGV_ACCERR);
 303 }
 304
 305 static void
 306 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 307 {
 308         struct task_struct *tsk = current;
 309         struct mm_struct *mm = tsk->mm;
 310
 311         up_read(&mm->mmap_sem);
 312
 313         /* Kernel mode? Handle exceptions or die: */
 314         if (!user_mode(regs))
 315                 no_context(regs, error_code, address);
 316
 317         force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
 318 }
 319
 320 static noinline int
 321 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 322                unsigned long address, unsigned int fault)
 323 {
 324         /*
 325          * Pagefault was interrupted by SIGKILL. We have no reason to
 326          * continue pagefault.
 327          */
 328         if (fatal_signal_pending(current)) {
 329                 if (!(fault & VM_FAULT_RETRY))
 330                         up_read(&current->mm->mmap_sem);
 331                 if (!user_mode(regs))
 332                         no_context(regs, error_code, address);
 333                 return 1;
 334         }
 335
 336         if (!(fault & VM_FAULT_ERROR))
 337                 return 0;
 338
 339         if (fault & VM_FAULT_OOM) {
 340                 /* Kernel mode? Handle exceptions or die: */
 341                 if (!user_mode(regs)) {
 342                         up_read(&current->mm->mmap_sem);
 343                         no_context(regs, error_code, address);
 344                         return 1;
 345                 }
 346                 up_read(&current->mm->mmap_sem);
 347
 348                 /*
 349                  * We ran out of memory, call the OOM killer, and return the
 350                  * userspace (which will retry the fault, or kill us if we got
 351                  * oom-killed):
 352                  */
 353                 pagefault_out_of_memory();
 354         } else {
 355                 if (fault & VM_FAULT_SIGBUS)
 356                         do_sigbus(regs, error_code, address);
 357                 else if (fault & VM_FAULT_SIGSEGV)
 358                         bad_area(regs, error_code, address);
 359                 else
 360                         BUG();
 361         }
 362
 363         return 1;
 364 }
 365
 366 static inline int access_error(int error_code, struct vm_area_struct *vma)
 367 {
 368         if (error_code & FAULT_CODE_WRITE) {
 369                 /* write, present and write, not present: */
 370                 if (unlikely(!(vma->vm_flags & VM_WRITE)))
 371                         return 1;
 372                 return 0;
 373         }
 374
 375         /* ITLB miss on NX page */
 376         if (unlikely((error_code & FAULT_CODE_ITLB) &&
 377                      !(vma->vm_flags & VM_EXEC)))
 378                 return 1;
 379
 380         /* read, not present: */
 381         if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
 382                 return 1;
 383
 384         return 0;
 385 }
 386
 387 static int fault_in_kernel_space(unsigned long address)
 388 {
 389         return address >= TASK_SIZE;
 390 }
 391
 392 /*
 393  * This routine handles page faults.  It determines the address,
 394  * and the problem, and then passes it off to one of the appropriate
 395  * routines.
 396  */
 397 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 398                                         unsigned long error_code,
 399                                         unsigned long address)
 400 {
 401         unsigned long vec;
 402         struct task_struct *tsk;
 403         struct mm_struct *mm;
 404         struct vm_area_struct * vma;
 405         int fault;
 406         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 407
 408         tsk = current;
 409         mm = tsk->mm;
 410         vec = lookup_exception_vector();
 411
 412         /*
 413          * We fault-in kernel-space virtual memory on-demand. The
 414          * 'reference' page table is init_mm.pgd.
 415          *
 416          * NOTE! We MUST NOT take any locks for this case. We may
 417          * be in an interrupt or a critical region, and should
 418          * only copy the information from the master page table,
 419          * nothing more.
 420          */
 421         if (unlikely(fault_in_kernel_space(address))) {
 422                 if (vmalloc_fault(address) >= 0)
 423                         return;
 424                 if (notify_page_fault(regs, vec))
 425                         return;
 426
 427                 bad_area_nosemaphore(regs, error_code, address);
 428                 return;
 429         }
 430
 431         if (unlikely(notify_page_fault(regs, vec)))
 432                 return;
 433
 434         /* Only enable interrupts if they were on before the fault */
 435         if ((regs->sr & SR_IMASK) != SR_IMASK)
 436                 local_irq_enable();
 437
 438         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 439
 440         /*
 441          * If we're in an interrupt, have no user context or are running
 442          * with pagefaults disabled then we must not take the fault:
 443          */
 444         if (unlikely(faulthandler_disabled() || !mm)) {
 445                 bad_area_nosemaphore(regs, error_code, address);
 446                 return;
 447         }
 448
 449 retry:
 450         down_read(&mm->mmap_sem);
 451
 452         vma = find_vma(mm, address);
 453         if (unlikely(!vma)) {
 454                 bad_area(regs, error_code, address);
 455                 return;
 456         }
 457         if (likely(vma->vm_start <= address))
 458                 goto good_area;
 459         if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
 460                 bad_area(regs, error_code, address);
 461                 return;
 462         }
 463         if (unlikely(expand_stack(vma, address))) {
 464                 bad_area(regs, error_code, address);
 465                 return;
 466         }
 467
 468         /*
 469          * Ok, we have a good vm_area for this memory access, so
 470          * we can handle it..
 471          */
 472 good_area:
 473         if (unlikely(access_error(error_code, vma))) {
 474                 bad_area_access_error(regs, error_code, address);
 475                 return;
 476         }
 477
 478         set_thread_fault_code(error_code);
 479
 480         if (user_mode(regs))
 481                 flags |= FAULT_FLAG_USER;
 482         if (error_code & FAULT_CODE_WRITE)
 483                 flags |= FAULT_FLAG_WRITE;
 484
 485         /*
 486          * If for any reason at all we couldn't handle the fault,
 487          * make sure we exit gracefully rather than endlessly redo
 488          * the fault.
 489          */
 490         fault = handle_mm_fault(mm, vma, address, flags);
 491
 492         if (unlikely(fault & (VM_FAULT_RETRY | VM_FAULT_ERROR)))
 493                 if (mm_fault_error(regs, error_code, address, fault))
 494                         return;
 495
 496         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 497                 if (fault & VM_FAULT_MAJOR) {
 498                         tsk->maj_flt++;
 499                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 500                                       regs, address);
 501                 } else {
 502                         tsk->min_flt++;
 503                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 504                                       regs, address);
 505                 }
 506                 if (fault & VM_FAULT_RETRY) {
 507                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 508                         flags |= FAULT_FLAG_TRIED;
 509
 510                         /*
 511                          * No need to up_read(&mm->mmap_sem) as we would
 512                          * have already released it in __lock_page_or_retry
 513                          * in mm/filemap.c.
 514                          */
 515                         goto retry;
 516                 }
 517         }
 518
 519         up_read(&mm->mmap_sem);
 520 }