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/kprobes.h>
  22 #include <linux/perf_event.h>
  23 #include <linux/uaccess.h>
  24
  25 #include <asm/branch.h>
  26 #include <asm/mmu_context.h>
  27 #include <asm/ptrace.h>
  28 #include <asm/highmem.h>                /* For VMALLOC_END */
  29 #include <linux/kdebug.h>
  30
  31 int show_unhandled_signals = 1;
  32
  33 /*
  34  * This routine handles page faults.  It determines the address,
  35  * and the problem, and then passes it off to one of the appropriate
  36  * routines.
  37  */
  38 static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
  39         unsigned long address)
  40 {
  41         struct vm_area_struct * vma = NULL;
  42         struct task_struct *tsk = current;
  43         struct mm_struct *mm = tsk->mm;
  44         const int field = sizeof(unsigned long) * 2;
  45         siginfo_t info;
  46         int fault;
  47         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  48
  49         static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
  50
  51 #if 0
  52         printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(),
  53                current->comm, current->pid, field, address, write,
  54                field, regs->cp0_epc);
  55 #endif
  56
  57 #ifdef CONFIG_KPROBES
  58         /*
  59          * This is to notify the fault handler of the kprobes.
  60          */
  61         if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
  62                        current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
  63                 return;
  64 #endif
  65
  66         info.si_code = SEGV_MAPERR;
  67
  68         /*
  69          * We fault-in kernel-space virtual memory on-demand. The
  70          * 'reference' page table is init_mm.pgd.
  71          *
  72          * NOTE! We MUST NOT take any locks for this case. We may
  73          * be in an interrupt or a critical region, and should
  74          * only copy the information from the master page table,
  75          * nothing more.
  76          */
  77 #ifdef CONFIG_64BIT
  78 # define VMALLOC_FAULT_TARGET no_context
  79 #else
  80 # define VMALLOC_FAULT_TARGET vmalloc_fault
  81 #endif
  82
  83         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  84                 goto VMALLOC_FAULT_TARGET;
  85 #ifdef MODULE_START
  86         if (unlikely(address >= MODULE_START && address < MODULE_END))
  87                 goto VMALLOC_FAULT_TARGET;
  88 #endif
  89
  90         /*
  91          * If we're in an interrupt or have no user
  92          * context, we must not take the fault..
  93          */
  94         if (faulthandler_disabled() || !mm)
  95                 goto bad_area_nosemaphore;
  96
  97         if (user_mode(regs))
  98                 flags |= FAULT_FLAG_USER;
  99 retry:
 100         down_read(&mm->mmap_sem);
 101         vma = find_vma(mm, address);
 102         if (!vma)
 103                 goto bad_area;
 104         if (vma->vm_start <= address)
 105                 goto good_area;
 106         if (!(vma->vm_flags & VM_GROWSDOWN))
 107                 goto bad_area;
 108         if (expand_stack(vma, address))
 109                 goto bad_area;
 110 /*
 111  * Ok, we have a good vm_area for this memory access, so
 112  * we can handle it..
 113  */
 114 good_area:
 115         info.si_code = SEGV_ACCERR;
 116
 117         if (write) {
 118                 if (!(vma->vm_flags & VM_WRITE))
 119                         goto bad_area;
 120                 flags |= FAULT_FLAG_WRITE;
 121         } else {
 122                 if (cpu_has_rixi) {
 123                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 124 #if 0
 125                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 126                                           raw_smp_processor_id(),
 127                                           current->comm, current->pid,
 128                                           field, address, write,
 129                                           field, regs->cp0_epc);
 130 #endif
 131                                 goto bad_area;
 132                         }
 133                         if (!(vma->vm_flags & VM_READ) &&
 134                             exception_epc(regs) != address) {
 135 #if 0
 136                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
 137                                           raw_smp_processor_id(),
 138                                           current->comm, current->pid,
 139                                           field, address, write,
 140                                           field, regs->cp0_epc);
 141 #endif
 142                                 goto bad_area;
 143                         }
 144                 } else {
 145                         if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 146                                 goto bad_area;
 147                 }
 148         }
 149
 150         /*
 151          * If for any reason at all we couldn't handle the fault,
 152          * make sure we exit gracefully rather than endlessly redo
 153          * the fault.
 154          */
 155         fault = handle_mm_fault(vma, address, flags);
 156
 157         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 158                 return;
 159
 160         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 161         if (unlikely(fault & VM_FAULT_ERROR)) {
 162                 if (fault & VM_FAULT_OOM)
 163                         goto out_of_memory;
 164                 else if (fault & VM_FAULT_SIGSEGV)
 165                         goto bad_area;
 166                 else if (fault & VM_FAULT_SIGBUS)
 167                         goto do_sigbus;
 168                 BUG();
 169         }
 170         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 171                 if (fault & VM_FAULT_MAJOR) {
 172                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 173                                                   regs, address);
 174                         tsk->maj_flt++;
 175                 } else {
 176                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 177                                                   regs, address);
 178                         tsk->min_flt++;
 179                 }
 180                 if (fault & VM_FAULT_RETRY) {
 181                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 182                         flags |= FAULT_FLAG_TRIED;
 183
 184                         /*
 185                          * No need to up_read(&mm->mmap_sem) as we would
 186                          * have already released it in __lock_page_or_retry
 187                          * in mm/filemap.c.
 188                          */
 189
 190                         goto retry;
 191                 }
 192         }
 193
 194         up_read(&mm->mmap_sem);
 195         return;
 196
 197 /*
 198  * Something tried to access memory that isn't in our memory map..
 199  * Fix it, but check if it's kernel or user first..
 200  */
 201 bad_area:
 202         up_read(&mm->mmap_sem);
 203
 204 bad_area_nosemaphore:
 205         /* User mode accesses just cause a SIGSEGV */
 206         if (user_mode(regs)) {
 207                 tsk->thread.cp0_badvaddr = address;
 208                 tsk->thread.error_code = write;
 209                 if (show_unhandled_signals &&
 210                     unhandled_signal(tsk, SIGSEGV) &&
 211                     __ratelimit(&ratelimit_state)) {
 212                         pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n",
 213                                 tsk->comm,
 214                                 write ? "write access to" : "read access from",
 215                                 field, address);
 216                         pr_info("epc = %0*lx in", field,
 217                                 (unsigned long) regs->cp0_epc);
 218                         print_vma_addr(KERN_CONT " ", regs->cp0_epc);
 219                         pr_cont("\n");
 220                         pr_info("ra  = %0*lx in", field,
 221                                 (unsigned long) regs->regs[31]);
 222                         print_vma_addr(KERN_CONT " ", regs->regs[31]);
 223                         pr_cont("\n");
 224                 }
 225                 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
 226                 info.si_signo = SIGSEGV;
 227                 info.si_errno = 0;
 228                 /* info.si_code has been set above */
 229                 info.si_addr = (void __user *) address;
 230                 force_sig_info(SIGSEGV, &info, tsk);
 231                 return;
 232         }
 233
 234 no_context:
 235         /* Are we prepared to handle this kernel fault?  */
 236         if (fixup_exception(regs)) {
 237                 current->thread.cp0_baduaddr = address;
 238                 return;
 239         }
 240
 241         /*
 242          * Oops. The kernel tried to access some bad page. We'll have to
 243          * terminate things with extreme prejudice.
 244          */
 245         bust_spinlocks(1);
 246
 247         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 248                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 249                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 250                field,  regs->regs[31]);
 251         die("Oops", regs);
 252
 253 out_of_memory:
 254         /*
 255          * We ran out of memory, call the OOM killer, and return the userspace
 256          * (which will retry the fault, or kill us if we got oom-killed).
 257          */
 258         up_read(&mm->mmap_sem);
 259         if (!user_mode(regs))
 260                 goto no_context;
 261         pagefault_out_of_memory();
 262         return;
 263
 264 do_sigbus:
 265         up_read(&mm->mmap_sem);
 266
 267         /* Kernel mode? Handle exceptions or die */
 268         if (!user_mode(regs))
 269                 goto no_context;
 270
 271         /*
 272          * Send a sigbus, regardless of whether we were in kernel
 273          * or user mode.
 274          */
 275 #if 0
 276         printk("do_page_fault() #3: sending SIGBUS to %s for "
 277                "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 278                tsk->comm,
 279                write ? "write access to" : "read access from",
 280                field, address,
 281                field, (unsigned long) regs->cp0_epc,
 282                field, (unsigned long) regs->regs[31]);
 283 #endif
 284         current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
 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 }