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 <asm/traps.h>
  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 __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         int si_code;
  47         vm_fault_t fault;
  48         unsigned int flags = FAULT_FLAG_DEFAULT;
  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.
  61          */
  62         if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
  63                        current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
  64                 return;
  65 #endif
  66
  67         si_code = SEGV_MAPERR;
  68
  69         /*
  70          * We fault-in kernel-space virtual memory on-demand. The
  71          * 'reference' page table is init_mm.pgd.
  72          *
  73          * NOTE! We MUST NOT take any locks for this case. We may
  74          * be in an interrupt or a critical region, and should
  75          * only copy the information from the master page table,
  76          * nothing more.
  77          */
  78 #ifdef CONFIG_64BIT
  79 # define VMALLOC_FAULT_TARGET no_context
  80 #else
  81 # define VMALLOC_FAULT_TARGET vmalloc_fault
  82 #endif
  83
  84         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  85                 goto VMALLOC_FAULT_TARGET;
  86 #ifdef MODULES_VADDR
  87         if (unlikely(address >= MODULES_VADDR && address < MODULES_END))
  88                 goto VMALLOC_FAULT_TARGET;
  89 #endif
  90
  91         /*
  92          * If we're in an interrupt or have no user
  93          * context, we must not take the fault..
  94          */
  95         if (faulthandler_disabled() || !mm)
  96                 goto bad_area_nosemaphore;
  97
  98         if (user_mode(regs))
  99                 flags |= FAULT_FLAG_USER;
 100
 101         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 102 retry:
 103         vma = lock_mm_and_find_vma(mm, address, regs);
 104         if (!vma)
 105                 goto bad_area_nosemaphore;
 106 /*
 107  * Ok, we have a good vm_area for this memory access, so
 108  * we can handle it..
 109  */
 110         si_code = SEGV_ACCERR;
 111
 112         if (write) {
 113                 if (!(vma->vm_flags & VM_WRITE))
 114                         goto bad_area;
 115                 flags |= FAULT_FLAG_WRITE;
 116         } else {
 117                 if (cpu_has_rixi) {
 118                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 119 #if 0
 120                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 121                                           raw_smp_processor_id(),
 122                                           current->comm, current->pid,
 123                                           field, address, write,
 124                                           field, regs->cp0_epc);
 125 #endif
 126                                 goto bad_area;
 127                         }
 128                         if (!(vma->vm_flags & VM_READ) &&
 129                             exception_epc(regs) != address) {
 130 #if 0
 131                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
 132                                           raw_smp_processor_id(),
 133                                           current->comm, current->pid,
 134                                           field, address, write,
 135                                           field, regs->cp0_epc);
 136 #endif
 137                                 goto bad_area;
 138                         }
 139                 } else {
 140                         if (unlikely(!vma_is_accessible(vma)))
 141                                 goto bad_area;
 142                 }
 143         }
 144
 145         /*
 146          * If for any reason at all we couldn't handle the fault,
 147          * make sure we exit gracefully rather than endlessly redo
 148          * the fault.
 149          */
 150         fault = handle_mm_fault(vma, address, flags, regs);
 151
 152         if (fault_signal_pending(fault, regs)) {
 153                 if (!user_mode(regs))
 154                         goto no_context;
 155                 return;
 156         }
 157
 158         /* The fault is fully completed (including releasing mmap lock) */
 159         if (fault & VM_FAULT_COMPLETED)
 160                 return;
 161
 162         if (unlikely(fault & VM_FAULT_ERROR)) {
 163                 if (fault & VM_FAULT_OOM)
 164                         goto out_of_memory;
 165                 else if (fault & VM_FAULT_SIGSEGV)
 166                         goto bad_area;
 167                 else if (fault & VM_FAULT_SIGBUS)
 168                         goto do_sigbus;
 169                 BUG();
 170         }
 171
 172         if (fault & VM_FAULT_RETRY) {
 173                 flags |= FAULT_FLAG_TRIED;
 174
 175                 /*
 176                  * No need to mmap_read_unlock(mm) as we would
 177                  * have already released it in __lock_page_or_retry
 178                  * in mm/filemap.c.
 179                  */
 180
 181                 goto retry;
 182         }
 183
 184         mmap_read_unlock(mm);
 185         return;
 186
 187 /*
 188  * Something tried to access memory that isn't in our memory map..
 189  * Fix it, but check if it's kernel or user first..
 190  */
 191 bad_area:
 192         mmap_read_unlock(mm);
 193
 194 bad_area_nosemaphore:
 195         /* User mode accesses just cause a SIGSEGV */
 196         if (user_mode(regs)) {
 197                 tsk->thread.cp0_badvaddr = address;
 198                 tsk->thread.error_code = write;
 199                 if (show_unhandled_signals &&
 200                     unhandled_signal(tsk, SIGSEGV) &&
 201                     __ratelimit(&ratelimit_state)) {
 202                         pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n",
 203                                 tsk->comm,
 204                                 write ? "write access to" : "read access from",
 205                                 field, address);
 206                         pr_info("epc = %0*lx in", field,
 207                                 (unsigned long) regs->cp0_epc);
 208                         print_vma_addr(KERN_CONT " ", regs->cp0_epc);
 209                         pr_cont("\n");
 210                         pr_info("ra  = %0*lx in", field,
 211                                 (unsigned long) regs->regs[31]);
 212                         print_vma_addr(KERN_CONT " ", regs->regs[31]);
 213                         pr_cont("\n");
 214                 }
 215                 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
 216                 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 217                 return;
 218         }
 219
 220 no_context:
 221         /* Are we prepared to handle this kernel fault?  */
 222         if (fixup_exception(regs)) {
 223                 current->thread.cp0_baduaddr = address;
 224                 return;
 225         }
 226
 227         /*
 228          * Oops. The kernel tried to access some bad page. We'll have to
 229          * terminate things with extreme prejudice.
 230          */
 231         bust_spinlocks(1);
 232
 233         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 234                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 235                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 236                field,  regs->regs[31]);
 237         die("Oops", regs);
 238
 239 out_of_memory:
 240         /*
 241          * We ran out of memory, call the OOM killer, and return the userspace
 242          * (which will retry the fault, or kill us if we got oom-killed).
 243          */
 244         mmap_read_unlock(mm);
 245         if (!user_mode(regs))
 246                 goto no_context;
 247         pagefault_out_of_memory();
 248         return;
 249
 250 do_sigbus:
 251         mmap_read_unlock(mm);
 252
 253         /* Kernel mode? Handle exceptions or die */
 254         if (!user_mode(regs))
 255                 goto no_context;
 256
 257         /*
 258          * Send a sigbus, regardless of whether we were in kernel
 259          * or user mode.
 260          */
 261 #if 0
 262         printk("do_page_fault() #3: sending SIGBUS to %s for "
 263                "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 264                tsk->comm,
 265                write ? "write access to" : "read access from",
 266                field, address,
 267                field, (unsigned long) regs->cp0_epc,
 268                field, (unsigned long) regs->regs[31]);
 269 #endif
 270         current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
 271         tsk->thread.cp0_badvaddr = address;
 272         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
 273
 274         return;
 275 #ifndef CONFIG_64BIT
 276 vmalloc_fault:
 277         {
 278                 /*
 279                  * Synchronize this task's top level page-table
 280                  * with the 'reference' page table.
 281                  *
 282                  * Do _not_ use "tsk" here. We might be inside
 283                  * an interrupt in the middle of a task switch..
 284                  */
 285                 int offset = pgd_index(address);
 286                 pgd_t *pgd, *pgd_k;
 287                 p4d_t *p4d, *p4d_k;
 288                 pud_t *pud, *pud_k;
 289                 pmd_t *pmd, *pmd_k;
 290                 pte_t *pte_k;
 291
 292                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 293                 pgd_k = init_mm.pgd + offset;
 294
 295                 if (!pgd_present(*pgd_k))
 296                         goto no_context;
 297                 set_pgd(pgd, *pgd_k);
 298
 299                 p4d = p4d_offset(pgd, address);
 300                 p4d_k = p4d_offset(pgd_k, address);
 301                 if (!p4d_present(*p4d_k))
 302                         goto no_context;
 303
 304                 pud = pud_offset(p4d, address);
 305                 pud_k = pud_offset(p4d_k, address);
 306                 if (!pud_present(*pud_k))
 307                         goto no_context;
 308
 309                 pmd = pmd_offset(pud, address);
 310                 pmd_k = pmd_offset(pud_k, address);
 311                 if (!pmd_present(*pmd_k))
 312                         goto no_context;
 313                 set_pmd(pmd, *pmd_k);
 314
 315                 pte_k = pte_offset_kernel(pmd_k, address);
 316                 if (!pte_present(*pte_k))
 317                         goto no_context;
 318                 return;
 319         }
 320 #endif
 321 }
 322 NOKPROBE_SYMBOL(__do_page_fault);
 323
 324 asmlinkage void do_page_fault(struct pt_regs *regs,
 325         unsigned long write, unsigned long address)
 326 {
 327         enum ctx_state prev_state;
 328
 329         prev_state = exception_enter();
 330         __do_page_fault(regs, write, address);
 331         exception_exit(prev_state);
 332 }
 333 NOKPROBE_SYMBOL(do_page_fault);