arch/sh/mm/fault_32.c

   1 /*
   2  * Page fault handler for SH with an MMU.
   3  *
   4  *  Copyright (C) 1999  Niibe Yutaka
   5  *  Copyright (C) 2003 - 2009  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 <asm/io_trapped.h>
  20 #include <asm/system.h>
  21 #include <asm/mmu_context.h>
  22 #include <asm/tlbflush.h>
  23
  24 static inline int notify_page_fault(struct pt_regs *regs, int trap)
  25 {
  26         int ret = 0;
  27
  28         if (kprobes_built_in() && !user_mode(regs)) {
  29                 preempt_disable();
  30                 if (kprobe_running() && kprobe_fault_handler(regs, trap))
  31                         ret = 1;
  32                 preempt_enable();
  33         }
  34
  35         return ret;
  36 }
  37
  38 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
  39 {
  40         unsigned index = pgd_index(address);
  41         pgd_t *pgd_k;
  42         pud_t *pud, *pud_k;
  43         pmd_t *pmd, *pmd_k;
  44
  45         pgd += index;
  46         pgd_k = init_mm.pgd + index;
  47
  48         if (!pgd_present(*pgd_k))
  49                 return NULL;
  50
  51         pud = pud_offset(pgd, address);
  52         pud_k = pud_offset(pgd_k, address);
  53         if (!pud_present(*pud_k))
  54                 return NULL;
  55
  56         if (!pud_present(*pud))
  57             set_pud(pud, *pud_k);
  58
  59         pmd = pmd_offset(pud, address);
  60         pmd_k = pmd_offset(pud_k, address);
  61         if (!pmd_present(*pmd_k))
  62                 return NULL;
  63
  64         if (!pmd_present(*pmd))
  65                 set_pmd(pmd, *pmd_k);
  66         else {
  67                 /*
  68                  * The page tables are fully synchronised so there must
  69                  * be another reason for the fault. Return NULL here to
  70                  * signal that we have not taken care of the fault.
  71                  */
  72                 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
  73                 return NULL;
  74         }
  75
  76         return pmd_k;
  77 }
  78
  79 /*
  80  * Handle a fault on the vmalloc or module mapping area
  81  */
  82 static noinline int vmalloc_fault(unsigned long address)
  83 {
  84         pgd_t *pgd_k;
  85         pmd_t *pmd_k;
  86         pte_t *pte_k;
  87
  88         /* Make sure we are in vmalloc/module/P3 area: */
  89         if (!(address >= VMALLOC_START && address < P3_ADDR_MAX))
  90                 return -1;
  91
  92         /*
  93          * Synchronize this task's top level page-table
  94          * with the 'reference' page table.
  95          *
  96          * Do _not_ use "current" here. We might be inside
  97          * an interrupt in the middle of a task switch..
  98          */
  99         pgd_k = get_TTB();
 100         pmd_k = vmalloc_sync_one(pgd_k, address);
 101         if (!pmd_k)
 102                 return -1;
 103
 104         pte_k = pte_offset_kernel(pmd_k, address);
 105         if (!pte_present(*pte_k))
 106                 return -1;
 107
 108         return 0;
 109 }
 110
 111 static int fault_in_kernel_space(unsigned long address)
 112 {
 113         return address >= TASK_SIZE;
 114 }
 115
 116 /*
 117  * This routine handles page faults.  It determines the address,
 118  * and the problem, and then passes it off to one of the appropriate
 119  * routines.
 120  */
 121 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 122                                         unsigned long writeaccess,
 123                                         unsigned long address)
 124 {
 125         unsigned long vec;
 126         struct task_struct *tsk;
 127         struct mm_struct *mm;
 128         struct vm_area_struct * vma;
 129         int si_code;
 130         int fault;
 131         siginfo_t info;
 132
 133         tsk = current;
 134         mm = tsk->mm;
 135         si_code = SEGV_MAPERR;
 136         vec = lookup_exception_vector();
 137
 138         /*
 139          * We fault-in kernel-space virtual memory on-demand. The
 140          * 'reference' page table is init_mm.pgd.
 141          *
 142          * NOTE! We MUST NOT take any locks for this case. We may
 143          * be in an interrupt or a critical region, and should
 144          * only copy the information from the master page table,
 145          * nothing more.
 146          */
 147         if (unlikely(fault_in_kernel_space(address))) {
 148                 if (vmalloc_fault(address) >= 0)
 149                         return;
 150                 if (notify_page_fault(regs, vec))
 151                         return;
 152
 153                 goto bad_area_nosemaphore;
 154         }
 155
 156         if (unlikely(notify_page_fault(regs, vec)))
 157                 return;
 158
 159         /* Only enable interrupts if they were on before the fault */
 160         if ((regs->sr & SR_IMASK) != SR_IMASK)
 161                 local_irq_enable();
 162
 163         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address);
 164
 165         /*
 166          * If we're in an interrupt, have no user context or are running
 167          * in an atomic region then we must not take the fault:
 168          */
 169         if (in_atomic() || !mm)
 170                 goto no_context;
 171
 172         down_read(&mm->mmap_sem);
 173
 174         vma = find_vma(mm, address);
 175         if (!vma)
 176                 goto bad_area;
 177         if (vma->vm_start <= address)
 178                 goto good_area;
 179         if (!(vma->vm_flags & VM_GROWSDOWN))
 180                 goto bad_area;
 181         if (expand_stack(vma, address))
 182                 goto bad_area;
 183
 184         /*
 185          * Ok, we have a good vm_area for this memory access, so
 186          * we can handle it..
 187          */
 188 good_area:
 189         si_code = SEGV_ACCERR;
 190         if (writeaccess) {
 191                 if (!(vma->vm_flags & VM_WRITE))
 192                         goto bad_area;
 193         } else {
 194                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 195                         goto bad_area;
 196         }
 197
 198         /*
 199          * If for any reason at all we couldn't handle the fault,
 200          * make sure we exit gracefully rather than endlessly redo
 201          * the fault.
 202          */
 203 survive:
 204         fault = handle_mm_fault(mm, vma, address, writeaccess ? FAULT_FLAG_WRITE : 0);
 205         if (unlikely(fault & VM_FAULT_ERROR)) {
 206                 if (fault & VM_FAULT_OOM)
 207                         goto out_of_memory;
 208                 else if (fault & VM_FAULT_SIGBUS)
 209                         goto do_sigbus;
 210                 BUG();
 211         }
 212         if (fault & VM_FAULT_MAJOR) {
 213                 tsk->maj_flt++;
 214                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0,
 215                                      regs, address);
 216         } else {
 217                 tsk->min_flt++;
 218                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0,
 219                                      regs, address);
 220         }
 221
 222         up_read(&mm->mmap_sem);
 223         return;
 224
 225         /*
 226          * Something tried to access memory that isn't in our memory map..
 227          * Fix it, but check if it's kernel or user first..
 228          */
 229 bad_area:
 230         up_read(&mm->mmap_sem);
 231
 232 bad_area_nosemaphore:
 233         if (user_mode(regs)) {
 234                 info.si_signo = SIGSEGV;
 235                 info.si_errno = 0;
 236                 info.si_code = si_code;
 237                 info.si_addr = (void *) address;
 238                 force_sig_info(SIGSEGV, &info, tsk);
 239                 return;
 240         }
 241
 242 no_context:
 243         /* Are we prepared to handle this kernel fault?  */
 244         if (fixup_exception(regs))
 245                 return;
 246
 247         if (handle_trapped_io(regs, address))
 248                 return;
 249 /*
 250  * Oops. The kernel tried to access some bad page. We'll have to
 251  * terminate things with extreme prejudice.
 252  *
 253  */
 254
 255         bust_spinlocks(1);
 256
 257         if (oops_may_print()) {
 258                 unsigned long page;
 259
 260                 if (address < PAGE_SIZE)
 261                         printk(KERN_ALERT "Unable to handle kernel NULL "
 262                                           "pointer dereference");
 263                 else
 264                         printk(KERN_ALERT "Unable to handle kernel paging "
 265                                           "request");
 266                 printk(" at virtual address %08lx\n", address);
 267                 printk(KERN_ALERT "pc = %08lx\n", regs->pc);
 268                 page = (unsigned long)get_TTB();
 269                 if (page) {
 270                         page = ((__typeof__(page) *)page)[address >> PGDIR_SHIFT];
 271                         printk(KERN_ALERT "*pde = %08lx\n", page);
 272                         if (page & _PAGE_PRESENT) {
 273                                 page &= PAGE_MASK;
 274                                 address &= 0x003ff000;
 275                                 page = ((__typeof__(page) *)
 276                                                 __va(page))[address >>
 277                                                             PAGE_SHIFT];
 278                                 printk(KERN_ALERT "*pte = %08lx\n", page);
 279                         }
 280                 }
 281         }
 282
 283         die("Oops", regs, writeaccess);
 284         bust_spinlocks(0);
 285         do_exit(SIGKILL);
 286
 287 /*
 288  * We ran out of memory, or some other thing happened to us that made
 289  * us unable to handle the page fault gracefully.
 290  */
 291 out_of_memory:
 292         up_read(&mm->mmap_sem);
 293         if (is_global_init(current)) {
 294                 yield();
 295                 down_read(&mm->mmap_sem);
 296                 goto survive;
 297         }
 298         printk("VM: killing process %s\n", tsk->comm);
 299         if (user_mode(regs))
 300                 do_group_exit(SIGKILL);
 301         goto no_context;
 302
 303 do_sigbus:
 304         up_read(&mm->mmap_sem);
 305
 306         /*
 307          * Send a sigbus, regardless of whether we were in kernel
 308          * or user mode.
 309          */
 310         info.si_signo = SIGBUS;
 311         info.si_errno = 0;
 312         info.si_code = BUS_ADRERR;
 313         info.si_addr = (void *)address;
 314         force_sig_info(SIGBUS, &info, tsk);
 315
 316         /* Kernel mode? Handle exceptions or die */
 317         if (!user_mode(regs))
 318                 goto no_context;
 319 }
 320
 321 /*
 322  * Called with interrupts disabled.
 323  */
 324 asmlinkage int __kprobes
 325 handle_tlbmiss(struct pt_regs *regs, unsigned long writeaccess,
 326                unsigned long address)
 327 {
 328         pgd_t *pgd;
 329         pud_t *pud;
 330         pmd_t *pmd;
 331         pte_t *pte;
 332         pte_t entry;
 333
 334         /*
 335          * We don't take page faults for P1, P2, and parts of P4, these
 336          * are always mapped, whether it be due to legacy behaviour in
 337          * 29-bit mode, or due to PMB configuration in 32-bit mode.
 338          */
 339         if (address >= P3SEG && address < P3_ADDR_MAX) {
 340                 pgd = pgd_offset_k(address);
 341         } else {
 342                 if (unlikely(address >= TASK_SIZE || !current->mm))
 343                         return 1;
 344
 345                 pgd = pgd_offset(current->mm, address);
 346         }
 347
 348         pud = pud_offset(pgd, address);
 349         if (pud_none_or_clear_bad(pud))
 350                 return 1;
 351         pmd = pmd_offset(pud, address);
 352         if (pmd_none_or_clear_bad(pmd))
 353                 return 1;
 354         pte = pte_offset_kernel(pmd, address);
 355         entry = *pte;
 356         if (unlikely(pte_none(entry) || pte_not_present(entry)))
 357                 return 1;
 358         if (unlikely(writeaccess && !pte_write(entry)))
 359                 return 1;
 360
 361         if (writeaccess)
 362                 entry = pte_mkdirty(entry);
 363         entry = pte_mkyoung(entry);
 364
 365         set_pte(pte, entry);
 366
 367 #if defined(CONFIG_CPU_SH4) && !defined(CONFIG_SMP)
 368         /*
 369          * SH-4 does not set MMUCR.RC to the corresponding TLB entry in
 370          * the case of an initial page write exception, so we need to
 371          * flush it in order to avoid potential TLB entry duplication.
 372          */
 373         if (writeaccess == 2)
 374                 local_flush_tlb_one(get_asid(), address & PAGE_MASK);
 375 #endif
 376
 377         update_mmu_cache(NULL, address, entry);
 378
 379         return 0;
 380 }