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/sched/signal.h>
  17 #include <linux/hardirq.h>
  18 #include <linux/kprobes.h>
  19 #include <linux/perf_event.h>
  20 #include <linux/kdebug.h>
  21 #include <linux/uaccess.h>
  22 #include <asm/io_trapped.h>
  23 #include <asm/mmu_context.h>
  24 #include <asm/tlbflush.h>
  25 #include <asm/traps.h>
  26
  27 static void
  28 force_sig_info_fault(int si_signo, int si_code, unsigned long address)
  29 {
  30         force_sig_fault(si_signo, si_code, (void __user *)address);
  31 }
  32
  33 /*
  34  * This is useful to dump out the page tables associated with
  35  * 'addr' in mm 'mm'.
  36  */
  37 static void show_pte(struct mm_struct *mm, unsigned long addr)
  38 {
  39         pgd_t *pgd;
  40
  41         if (mm) {
  42                 pgd = mm->pgd;
  43         } else {
  44                 pgd = get_TTB();
  45
  46                 if (unlikely(!pgd))
  47                         pgd = swapper_pg_dir;
  48         }
  49
  50         pr_alert("pgd = %p\n", pgd);
  51         pgd += pgd_index(addr);
  52         pr_alert("[%08lx] *pgd=%0*llx", addr, (u32)(sizeof(*pgd) * 2),
  53                  (u64)pgd_val(*pgd));
  54
  55         do {
  56                 p4d_t *p4d;
  57                 pud_t *pud;
  58                 pmd_t *pmd;
  59                 pte_t *pte;
  60
  61                 if (pgd_none(*pgd))
  62                         break;
  63
  64                 if (pgd_bad(*pgd)) {
  65                         pr_cont("(bad)");
  66                         break;
  67                 }
  68
  69                 p4d = p4d_offset(pgd, addr);
  70                 if (PTRS_PER_P4D != 1)
  71                         pr_cont(", *p4d=%0*Lx", (u32)(sizeof(*p4d) * 2),
  72                                 (u64)p4d_val(*p4d));
  73
  74                 if (p4d_none(*p4d))
  75                         break;
  76
  77                 if (p4d_bad(*p4d)) {
  78                         pr_cont("(bad)");
  79                         break;
  80                 }
  81
  82                 pud = pud_offset(p4d, addr);
  83                 if (PTRS_PER_PUD != 1)
  84                         pr_cont(", *pud=%0*llx", (u32)(sizeof(*pud) * 2),
  85                                 (u64)pud_val(*pud));
  86
  87                 if (pud_none(*pud))
  88                         break;
  89
  90                 if (pud_bad(*pud)) {
  91                         pr_cont("(bad)");
  92                         break;
  93                 }
  94
  95                 pmd = pmd_offset(pud, addr);
  96                 if (PTRS_PER_PMD != 1)
  97                         pr_cont(", *pmd=%0*llx", (u32)(sizeof(*pmd) * 2),
  98                                 (u64)pmd_val(*pmd));
  99
 100                 if (pmd_none(*pmd))
 101                         break;
 102
 103                 if (pmd_bad(*pmd)) {
 104                         pr_cont("(bad)");
 105                         break;
 106                 }
 107
 108                 /* We must not map this if we have highmem enabled */
 109                 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
 110                         break;
 111
 112                 pte = pte_offset_kernel(pmd, addr);
 113                 pr_cont(", *pte=%0*llx", (u32)(sizeof(*pte) * 2),
 114                         (u64)pte_val(*pte));
 115         } while (0);
 116
 117         pr_cont("\n");
 118 }
 119
 120 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
 121 {
 122         unsigned index = pgd_index(address);
 123         pgd_t *pgd_k;
 124         p4d_t *p4d, *p4d_k;
 125         pud_t *pud, *pud_k;
 126         pmd_t *pmd, *pmd_k;
 127
 128         pgd += index;
 129         pgd_k = init_mm.pgd + index;
 130
 131         if (!pgd_present(*pgd_k))
 132                 return NULL;
 133
 134         p4d = p4d_offset(pgd, address);
 135         p4d_k = p4d_offset(pgd_k, address);
 136         if (!p4d_present(*p4d_k))
 137                 return NULL;
 138
 139         pud = pud_offset(p4d, address);
 140         pud_k = pud_offset(p4d_k, address);
 141         if (!pud_present(*pud_k))
 142                 return NULL;
 143
 144         if (!pud_present(*pud))
 145             set_pud(pud, *pud_k);
 146
 147         pmd = pmd_offset(pud, address);
 148         pmd_k = pmd_offset(pud_k, address);
 149         if (!pmd_present(*pmd_k))
 150                 return NULL;
 151
 152         if (!pmd_present(*pmd))
 153                 set_pmd(pmd, *pmd_k);
 154         else {
 155                 /*
 156                  * The page tables are fully synchronised so there must
 157                  * be another reason for the fault. Return NULL here to
 158                  * signal that we have not taken care of the fault.
 159                  */
 160                 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
 161                 return NULL;
 162         }
 163
 164         return pmd_k;
 165 }
 166
 167 #ifdef CONFIG_SH_STORE_QUEUES
 168 #define __FAULT_ADDR_LIMIT      P3_ADDR_MAX
 169 #else
 170 #define __FAULT_ADDR_LIMIT      VMALLOC_END
 171 #endif
 172
 173 /*
 174  * Handle a fault on the vmalloc or module mapping area
 175  */
 176 static noinline int vmalloc_fault(unsigned long address)
 177 {
 178         pgd_t *pgd_k;
 179         pmd_t *pmd_k;
 180         pte_t *pte_k;
 181
 182         /* Make sure we are in vmalloc/module/P3 area: */
 183         if (!(address >= VMALLOC_START && address < __FAULT_ADDR_LIMIT))
 184                 return -1;
 185
 186         /*
 187          * Synchronize this task's top level page-table
 188          * with the 'reference' page table.
 189          *
 190          * Do _not_ use "current" here. We might be inside
 191          * an interrupt in the middle of a task switch..
 192          */
 193         pgd_k = get_TTB();
 194         pmd_k = vmalloc_sync_one(pgd_k, address);
 195         if (!pmd_k)
 196                 return -1;
 197
 198         pte_k = pte_offset_kernel(pmd_k, address);
 199         if (!pte_present(*pte_k))
 200                 return -1;
 201
 202         return 0;
 203 }
 204
 205 static void
 206 show_fault_oops(struct pt_regs *regs, unsigned long address)
 207 {
 208         if (!oops_may_print())
 209                 return;
 210
 211         pr_alert("BUG: unable to handle kernel %s at %08lx\n",
 212                  address < PAGE_SIZE ? "NULL pointer dereference"
 213                                      : "paging request",
 214                  address);
 215         pr_alert("PC:");
 216         printk_address(regs->pc, 1);
 217
 218         show_pte(NULL, address);
 219 }
 220
 221 static noinline void
 222 no_context(struct pt_regs *regs, unsigned long error_code,
 223            unsigned long address)
 224 {
 225         /* Are we prepared to handle this kernel fault?  */
 226         if (fixup_exception(regs))
 227                 return;
 228
 229         if (handle_trapped_io(regs, address))
 230                 return;
 231
 232         /*
 233          * Oops. The kernel tried to access some bad page. We'll have to
 234          * terminate things with extreme prejudice.
 235          */
 236         bust_spinlocks(1);
 237
 238         show_fault_oops(regs, address);
 239
 240         die("Oops", regs, error_code);
 241 }
 242
 243 static void
 244 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 245                        unsigned long address, int si_code)
 246 {
 247         /* User mode accesses just cause a SIGSEGV */
 248         if (user_mode(regs)) {
 249                 /*
 250                  * It's possible to have interrupts off here:
 251                  */
 252                 local_irq_enable();
 253
 254                 force_sig_info_fault(SIGSEGV, si_code, address);
 255
 256                 return;
 257         }
 258
 259         no_context(regs, error_code, address);
 260 }
 261
 262 static noinline void
 263 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 264                      unsigned long address)
 265 {
 266         __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
 267 }
 268
 269 static void
 270 __bad_area(struct pt_regs *regs, unsigned long error_code,
 271            unsigned long address, int si_code)
 272 {
 273         struct mm_struct *mm = current->mm;
 274
 275         /*
 276          * Something tried to access memory that isn't in our memory map..
 277          * Fix it, but check if it's kernel or user first..
 278          */
 279         mmap_read_unlock(mm);
 280
 281         __bad_area_nosemaphore(regs, error_code, address, si_code);
 282 }
 283
 284 static noinline void
 285 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 286 {
 287         __bad_area(regs, error_code, address, SEGV_MAPERR);
 288 }
 289
 290 static noinline void
 291 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
 292                       unsigned long address)
 293 {
 294         __bad_area(regs, error_code, address, SEGV_ACCERR);
 295 }
 296
 297 static void
 298 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 299 {
 300         struct task_struct *tsk = current;
 301         struct mm_struct *mm = tsk->mm;
 302
 303         mmap_read_unlock(mm);
 304
 305         /* Kernel mode? Handle exceptions or die: */
 306         if (!user_mode(regs))
 307                 no_context(regs, error_code, address);
 308
 309         force_sig_info_fault(SIGBUS, BUS_ADRERR, address);
 310 }
 311
 312 static noinline int
 313 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 314                unsigned long address, vm_fault_t fault)
 315 {
 316         /*
 317          * Pagefault was interrupted by SIGKILL. We have no reason to
 318          * continue pagefault.
 319          */
 320         if (fault_signal_pending(fault, regs)) {
 321                 if (!user_mode(regs))
 322                         no_context(regs, error_code, address);
 323                 return 1;
 324         }
 325
 326         /* Release mmap_lock first if necessary */
 327         if (!(fault & VM_FAULT_RETRY))
 328                 mmap_read_unlock(current->mm);
 329
 330         if (!(fault & VM_FAULT_ERROR))
 331                 return 0;
 332
 333         if (fault & VM_FAULT_OOM) {
 334                 /* Kernel mode? Handle exceptions or die: */
 335                 if (!user_mode(regs)) {
 336                         no_context(regs, error_code, address);
 337                         return 1;
 338                 }
 339
 340                 /*
 341                  * We ran out of memory, call the OOM killer, and return the
 342                  * userspace (which will retry the fault, or kill us if we got
 343                  * oom-killed):
 344                  */
 345                 pagefault_out_of_memory();
 346         } else {
 347                 if (fault & VM_FAULT_SIGBUS)
 348                         do_sigbus(regs, error_code, address);
 349                 else if (fault & VM_FAULT_SIGSEGV)
 350                         bad_area(regs, error_code, address);
 351                 else
 352                         BUG();
 353         }
 354
 355         return 1;
 356 }
 357
 358 static inline int access_error(int error_code, struct vm_area_struct *vma)
 359 {
 360         if (error_code & FAULT_CODE_WRITE) {
 361                 /* write, present and write, not present: */
 362                 if (unlikely(!(vma->vm_flags & VM_WRITE)))
 363                         return 1;
 364                 return 0;
 365         }
 366
 367         /* ITLB miss on NX page */
 368         if (unlikely((error_code & FAULT_CODE_ITLB) &&
 369                      !(vma->vm_flags & VM_EXEC)))
 370                 return 1;
 371
 372         /* read, not present: */
 373         if (unlikely(!vma_is_accessible(vma)))
 374                 return 1;
 375
 376         return 0;
 377 }
 378
 379 static int fault_in_kernel_space(unsigned long address)
 380 {
 381         return address >= TASK_SIZE;
 382 }
 383
 384 /*
 385  * This routine handles page faults.  It determines the address,
 386  * and the problem, and then passes it off to one of the appropriate
 387  * routines.
 388  */
 389 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 390                                         unsigned long error_code,
 391                                         unsigned long address)
 392 {
 393         unsigned long vec;
 394         struct task_struct *tsk;
 395         struct mm_struct *mm;
 396         struct vm_area_struct * vma;
 397         vm_fault_t fault;
 398         unsigned int flags = FAULT_FLAG_DEFAULT;
 399
 400         tsk = current;
 401         mm = tsk->mm;
 402         vec = lookup_exception_vector();
 403
 404         /*
 405          * We fault-in kernel-space virtual memory on-demand. The
 406          * 'reference' page table is init_mm.pgd.
 407          *
 408          * NOTE! We MUST NOT take any locks for this case. We may
 409          * be in an interrupt or a critical region, and should
 410          * only copy the information from the master page table,
 411          * nothing more.
 412          */
 413         if (unlikely(fault_in_kernel_space(address))) {
 414                 if (vmalloc_fault(address) >= 0)
 415                         return;
 416                 if (kprobe_page_fault(regs, vec))
 417                         return;
 418
 419                 bad_area_nosemaphore(regs, error_code, address);
 420                 return;
 421         }
 422
 423         if (unlikely(kprobe_page_fault(regs, vec)))
 424                 return;
 425
 426         /* Only enable interrupts if they were on before the fault */
 427         if ((regs->sr & SR_IMASK) != SR_IMASK)
 428                 local_irq_enable();
 429
 430         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 431
 432         /*
 433          * If we're in an interrupt, have no user context or are running
 434          * with pagefaults disabled then we must not take the fault:
 435          */
 436         if (unlikely(faulthandler_disabled() || !mm)) {
 437                 bad_area_nosemaphore(regs, error_code, address);
 438                 return;
 439         }
 440
 441 retry:
 442         vma = lock_mm_and_find_vma(mm, address, regs);
 443         if (unlikely(!vma)) {
 444                 bad_area_nosemaphore(regs, error_code, address);
 445                 return;
 446         }
 447
 448         /*
 449          * Ok, we have a good vm_area for this memory access, so
 450          * we can handle it..
 451          */
 452         if (unlikely(access_error(error_code, vma))) {
 453                 bad_area_access_error(regs, error_code, address);
 454                 return;
 455         }
 456
 457         set_thread_fault_code(error_code);
 458
 459         if (user_mode(regs))
 460                 flags |= FAULT_FLAG_USER;
 461         if (error_code & FAULT_CODE_WRITE)
 462                 flags |= FAULT_FLAG_WRITE;
 463
 464         /*
 465          * If for any reason at all we couldn't handle the fault,
 466          * make sure we exit gracefully rather than endlessly redo
 467          * the fault.
 468          */
 469         fault = handle_mm_fault(vma, address, flags, regs);
 470
 471         if (unlikely(fault & (VM_FAULT_RETRY | VM_FAULT_ERROR)))
 472                 if (mm_fault_error(regs, error_code, address, fault))
 473                         return;
 474
 475         /* The fault is fully completed (including releasing mmap lock) */
 476         if (fault & VM_FAULT_COMPLETED)
 477                 return;
 478
 479         if (fault & VM_FAULT_RETRY) {
 480                 flags |= FAULT_FLAG_TRIED;
 481
 482                 /*
 483                  * No need to mmap_read_unlock(mm) as we would
 484                  * have already released it in __lock_page_or_retry
 485                  * in mm/filemap.c.
 486                  */
 487                 goto retry;
 488         }
 489
 490         mmap_read_unlock(mm);
 491 }