arch/mips/mm/fault.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1995 - 2000 by Ralf Baechle
   7  */
   8 #include <linux/context_tracking.h>
   9 #include <linux/signal.h>
  10 #include <linux/sched.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/kernel.h>
  13 #include <linux/errno.h>
  14 #include <linux/string.h>
  15 #include <linux/types.h>
  16 #include <linux/ptrace.h>
  17 #include <linux/ratelimit.h>
  18 #include <linux/mman.h>
  19 #include <linux/mm.h>
  20 #include <linux/smp.h>
  21 #include <linux/module.h>
  22 #include <linux/kprobes.h>
  23 #include <linux/perf_event.h>
  24 #include <linux/uaccess.h>
  25
  26 #include <asm/branch.h>
  27 #include <asm/mmu_context.h>
  28 #include <asm/ptrace.h>
  29 #include <asm/highmem.h>                /* For VMALLOC_END */
  30 #include <linux/kdebug.h>
  31
  32 int show_unhandled_signals = 1;
  33
  34 /*
  35  * This routine handles page faults.  It determines the address,
  36  * and the problem, and then passes it off to one of the appropriate
  37  * routines.
  38  */
  39 static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
  40         unsigned long address)
  41 {
  42         struct vm_area_struct * vma = NULL;
  43         struct task_struct *tsk = current;
  44         struct mm_struct *mm = tsk->mm;
  45         const int field = sizeof(unsigned long) * 2;
  46         siginfo_t info;
  47         int fault;
  48         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  49
  50         static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
  51
  52 #if 0
  53         printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(),
  54                current->comm, current->pid, field, address, write,
  55                field, regs->cp0_epc);
  56 #endif
  57
  58 #ifdef CONFIG_KPROBES
  59         /*
  60          * This is to notify the fault handler of the kprobes.  The
  61          * exception code is redundant as it is also carried in REGS,
  62          * but we pass it anyhow.
  63          */
  64         if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
  65                        (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP)
  66                 return;
  67 #endif
  68
  69         info.si_code = SEGV_MAPERR;
  70
  71         /*
  72          * We fault-in kernel-space virtual memory on-demand. The
  73          * 'reference' page table is init_mm.pgd.
  74          *
  75          * NOTE! We MUST NOT take any locks for this case. We may
  76          * be in an interrupt or a critical region, and should
  77          * only copy the information from the master page table,
  78          * nothing more.
  79          */
  80 #ifdef CONFIG_64BIT
  81 # define VMALLOC_FAULT_TARGET no_context
  82 #else
  83 # define VMALLOC_FAULT_TARGET vmalloc_fault
  84 #endif
  85
  86         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  87                 goto VMALLOC_FAULT_TARGET;
  88 #ifdef MODULE_START
  89         if (unlikely(address >= MODULE_START && address < MODULE_END))
  90                 goto VMALLOC_FAULT_TARGET;
  91 #endif
  92
  93         /*
  94          * If we're in an interrupt or have no user
  95          * context, we must not take the fault..
  96          */
  97         if (faulthandler_disabled() || !mm)
  98                 goto bad_area_nosemaphore;
  99
 100         if (user_mode(regs))
 101                 flags |= FAULT_FLAG_USER;
 102 retry:
 103         down_read(&mm->mmap_sem);
 104         vma = find_vma(mm, address);
 105         if (!vma)
 106                 goto bad_area;
 107         if (vma->vm_start <= address)
 108                 goto good_area;
 109         if (!(vma->vm_flags & VM_GROWSDOWN))
 110                 goto bad_area;
 111         if (expand_stack(vma, address))
 112                 goto bad_area;
 113 /*
 114  * Ok, we have a good vm_area for this memory access, so
 115  * we can handle it..
 116  */
 117 good_area:
 118         info.si_code = SEGV_ACCERR;
 119
 120         if (write) {
 121                 if (!(vma->vm_flags & VM_WRITE))
 122                         goto bad_area;
 123                 flags |= FAULT_FLAG_WRITE;
 124         } else {
 125                 if (cpu_has_rixi) {
 126                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 127 #if 0
 128                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 129                                           raw_smp_processor_id(),
 130                                           current->comm, current->pid,
 131                                           field, address, write,
 132                                           field, regs->cp0_epc);
 133 #endif
 134                                 goto bad_area;
 135                         }
 136                         if (!(vma->vm_flags & VM_READ) &&
 137                             exception_epc(regs) != address) {
 138 #if 0
 139                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
 140                                           raw_smp_processor_id(),
 141                                           current->comm, current->pid,
 142                                           field, address, write,
 143                                           field, regs->cp0_epc);
 144 #endif
 145                                 goto bad_area;
 146                         }
 147                 } else {
 148                         if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 149                                 goto bad_area;
 150                 }
 151         }
 152
 153         /*
 154          * If for any reason at all we couldn't handle the fault,
 155          * make sure we exit gracefully rather than endlessly redo
 156          * the fault.
 157          */
 158         fault = handle_mm_fault(mm, vma, address, flags);
 159
 160         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 161                 return;
 162
 163         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 164         if (unlikely(fault & VM_FAULT_ERROR)) {
 165                 if (fault & VM_FAULT_OOM)
 166                         goto out_of_memory;
 167                 else if (fault & VM_FAULT_SIGSEGV)
 168                         goto bad_area;
 169                 else if (fault & VM_FAULT_SIGBUS)
 170                         goto do_sigbus;
 171                 BUG();
 172         }
 173         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 174                 if (fault & VM_FAULT_MAJOR) {
 175                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 176                                                   regs, address);
 177                         tsk->maj_flt++;
 178                 } else {
 179                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 180                                                   regs, address);
 181                         tsk->min_flt++;
 182                 }
 183                 if (fault & VM_FAULT_RETRY) {
 184                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 185                         flags |= FAULT_FLAG_TRIED;
 186
 187                         /*
 188                          * No need to up_read(&mm->mmap_sem) as we would
 189                          * have already released it in __lock_page_or_retry
 190                          * in mm/filemap.c.
 191                          */
 192
 193                         goto retry;
 194                 }
 195         }
 196
 197         up_read(&mm->mmap_sem);
 198         return;
 199
 200 /*
 201  * Something tried to access memory that isn't in our memory map..
 202  * Fix it, but check if it's kernel or user first..
 203  */
 204 bad_area:
 205         up_read(&mm->mmap_sem);
 206
 207 bad_area_nosemaphore:
 208         /* User mode accesses just cause a SIGSEGV */
 209         if (user_mode(regs)) {
 210                 tsk->thread.cp0_badvaddr = address;
 211                 tsk->thread.error_code = write;
 212                 if (show_unhandled_signals &&
 213                     unhandled_signal(tsk, SIGSEGV) &&
 214                     __ratelimit(&ratelimit_state)) {
 215                         pr_info("\ndo_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx",
 216                                 tsk->comm,
 217                                 write ? "write access to" : "read access from",
 218                                 field, address);
 219                         pr_info("epc = %0*lx in", field,
 220                                 (unsigned long) regs->cp0_epc);
 221                         print_vma_addr(" ", regs->cp0_epc);
 222                         pr_info("ra  = %0*lx in", field,
 223                                 (unsigned long) regs->regs[31]);
 224                         print_vma_addr(" ", regs->regs[31]);
 225                         pr_info("\n");
 226                 }
 227                 info.si_signo = SIGSEGV;
 228                 info.si_errno = 0;
 229                 /* info.si_code has been set above */
 230                 info.si_addr = (void __user *) address;
 231                 force_sig_info(SIGSEGV, &info, tsk);
 232                 return;
 233         }
 234
 235 no_context:
 236         /* Are we prepared to handle this kernel fault?  */
 237         if (fixup_exception(regs)) {
 238                 current->thread.cp0_baduaddr = address;
 239                 return;
 240         }
 241
 242         /*
 243          * Oops. The kernel tried to access some bad page. We'll have to
 244          * terminate things with extreme prejudice.
 245          */
 246         bust_spinlocks(1);
 247
 248         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 249                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 250                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 251                field,  regs->regs[31]);
 252         die("Oops", regs);
 253
 254 out_of_memory:
 255         /*
 256          * We ran out of memory, call the OOM killer, and return the userspace
 257          * (which will retry the fault, or kill us if we got oom-killed).
 258          */
 259         up_read(&mm->mmap_sem);
 260         if (!user_mode(regs))
 261                 goto no_context;
 262         pagefault_out_of_memory();
 263         return;
 264
 265 do_sigbus:
 266         up_read(&mm->mmap_sem);
 267
 268         /* Kernel mode? Handle exceptions or die */
 269         if (!user_mode(regs))
 270                 goto no_context;
 271         else
 272         /*
 273          * Send a sigbus, regardless of whether we were in kernel
 274          * or user mode.
 275          */
 276 #if 0
 277                 printk("do_page_fault() #3: sending SIGBUS to %s for "
 278                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 279                        tsk->comm,
 280                        write ? "write access to" : "read access from",
 281                        field, address,
 282                        field, (unsigned long) regs->cp0_epc,
 283                        field, (unsigned long) regs->regs[31]);
 284 #endif
 285         tsk->thread.cp0_badvaddr = address;
 286         info.si_signo = SIGBUS;
 287         info.si_errno = 0;
 288         info.si_code = BUS_ADRERR;
 289         info.si_addr = (void __user *) address;
 290         force_sig_info(SIGBUS, &info, tsk);
 291
 292         return;
 293 #ifndef CONFIG_64BIT
 294 vmalloc_fault:
 295         {
 296                 /*
 297                  * Synchronize this task's top level page-table
 298                  * with the 'reference' page table.
 299                  *
 300                  * Do _not_ use "tsk" here. We might be inside
 301                  * an interrupt in the middle of a task switch..
 302                  */
 303                 int offset = __pgd_offset(address);
 304                 pgd_t *pgd, *pgd_k;
 305                 pud_t *pud, *pud_k;
 306                 pmd_t *pmd, *pmd_k;
 307                 pte_t *pte_k;
 308
 309                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 310                 pgd_k = init_mm.pgd + offset;
 311
 312                 if (!pgd_present(*pgd_k))
 313                         goto no_context;
 314                 set_pgd(pgd, *pgd_k);
 315
 316                 pud = pud_offset(pgd, address);
 317                 pud_k = pud_offset(pgd_k, address);
 318                 if (!pud_present(*pud_k))
 319                         goto no_context;
 320
 321                 pmd = pmd_offset(pud, address);
 322                 pmd_k = pmd_offset(pud_k, address);
 323                 if (!pmd_present(*pmd_k))
 324                         goto no_context;
 325                 set_pmd(pmd, *pmd_k);
 326
 327                 pte_k = pte_offset_kernel(pmd_k, address);
 328                 if (!pte_present(*pte_k))
 329                         goto no_context;
 330                 return;
 331         }
 332 #endif
 333 }
 334
 335 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 336         unsigned long write, unsigned long address)
 337 {
 338         enum ctx_state prev_state;
 339
 340         prev_state = exception_enter();
 341         __do_page_fault(regs, write, address);
 342         exception_exit(prev_state);
 343 }