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 __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         int si_code;
  46         vm_fault_t fault;
  47         unsigned int flags = FAULT_FLAG_DEFAULT;
  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         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
 100         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 101 retry:
 102         vma = lock_mm_and_find_vma(mm, address, regs);
 103         if (!vma)
 104                 goto bad_area_nosemaphore;
 105 /*
 106  * Ok, we have a good vm_area for this memory access, so
 107  * we can handle it..
 108  */
 109         si_code = SEGV_ACCERR;
 110
 111         if (write) {
 112                 if (!(vma->vm_flags & VM_WRITE))
 113                         goto bad_area;
 114                 flags |= FAULT_FLAG_WRITE;
 115         } else {
 116                 if (cpu_has_rixi) {
 117                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 118 #if 0
 119                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 120                                           raw_smp_processor_id(),
 121                                           current->comm, current->pid,
 122                                           field, address, write,
 123                                           field, regs->cp0_epc);
 124 #endif
 125                                 goto bad_area;
 126                         }
 127                         if (!(vma->vm_flags & VM_READ) &&
 128                             exception_epc(regs) != address) {
 129 #if 0
 130                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
 131                                           raw_smp_processor_id(),
 132                                           current->comm, current->pid,
 133                                           field, address, write,
 134                                           field, regs->cp0_epc);
 135 #endif
 136                                 goto bad_area;
 137                         }
 138                 } else {
 139                         if (unlikely(!vma_is_accessible(vma)))
 140                                 goto bad_area;
 141                 }
 142         }
 143
 144         /*
 145          * If for any reason at all we couldn't handle the fault,
 146          * make sure we exit gracefully rather than endlessly redo
 147          * the fault.
 148          */
 149         fault = handle_mm_fault(vma, address, flags, regs);
 150
 151         if (fault_signal_pending(fault, regs)) {
 152                 if (!user_mode(regs))
 153                         goto no_context;
 154                 return;
 155         }
 156
 157         /* The fault is fully completed (including releasing mmap lock) */
 158         if (fault & VM_FAULT_COMPLETED)
 159                 return;
 160
 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
 171         if (fault & VM_FAULT_RETRY) {
 172                 flags |= FAULT_FLAG_TRIED;
 173
 174                 /*
 175                  * No need to mmap_read_unlock(mm) as we would
 176                  * have already released it in __lock_page_or_retry
 177                  * in mm/filemap.c.
 178                  */
 179
 180                 goto retry;
 181         }
 182
 183         mmap_read_unlock(mm);
 184         return;
 185
 186 /*
 187  * Something tried to access memory that isn't in our memory map..
 188  * Fix it, but check if it's kernel or user first..
 189  */
 190 bad_area:
 191         mmap_read_unlock(mm);
 192
 193 bad_area_nosemaphore:
 194         /* User mode accesses just cause a SIGSEGV */
 195         if (user_mode(regs)) {
 196                 tsk->thread.cp0_badvaddr = address;
 197                 tsk->thread.error_code = write;
 198                 if (show_unhandled_signals &&
 199                     unhandled_signal(tsk, SIGSEGV) &&
 200                     __ratelimit(&ratelimit_state)) {
 201                         pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n",
 202                                 tsk->comm,
 203                                 write ? "write access to" : "read access from",
 204                                 field, address);
 205                         pr_info("epc = %0*lx in", field,
 206                                 (unsigned long) regs->cp0_epc);
 207                         print_vma_addr(KERN_CONT " ", regs->cp0_epc);
 208                         pr_cont("\n");
 209                         pr_info("ra  = %0*lx in", field,
 210                                 (unsigned long) regs->regs[31]);
 211                         print_vma_addr(KERN_CONT " ", regs->regs[31]);
 212                         pr_cont("\n");
 213                 }
 214                 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
 215                 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 216                 return;
 217         }
 218
 219 no_context:
 220         /* Are we prepared to handle this kernel fault?  */
 221         if (fixup_exception(regs)) {
 222                 current->thread.cp0_baduaddr = address;
 223                 return;
 224         }
 225
 226         /*
 227          * Oops. The kernel tried to access some bad page. We'll have to
 228          * terminate things with extreme prejudice.
 229          */
 230         bust_spinlocks(1);
 231
 232         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 233                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 234                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 235                field,  regs->regs[31]);
 236         die("Oops", regs);
 237
 238 out_of_memory:
 239         /*
 240          * We ran out of memory, call the OOM killer, and return the userspace
 241          * (which will retry the fault, or kill us if we got oom-killed).
 242          */
 243         mmap_read_unlock(mm);
 244         if (!user_mode(regs))
 245                 goto no_context;
 246         pagefault_out_of_memory();
 247         return;
 248
 249 do_sigbus:
 250         mmap_read_unlock(mm);
 251
 252         /* Kernel mode? Handle exceptions or die */
 253         if (!user_mode(regs))
 254                 goto no_context;
 255
 256         /*
 257          * Send a sigbus, regardless of whether we were in kernel
 258          * or user mode.
 259          */
 260 #if 0
 261         printk("do_page_fault() #3: sending SIGBUS to %s for "
 262                "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 263                tsk->comm,
 264                write ? "write access to" : "read access from",
 265                field, address,
 266                field, (unsigned long) regs->cp0_epc,
 267                field, (unsigned long) regs->regs[31]);
 268 #endif
 269         current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
 270         tsk->thread.cp0_badvaddr = address;
 271         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
 272
 273         return;
 274 #ifndef CONFIG_64BIT
 275 vmalloc_fault:
 276         {
 277                 /*
 278                  * Synchronize this task's top level page-table
 279                  * with the 'reference' page table.
 280                  *
 281                  * Do _not_ use "tsk" here. We might be inside
 282                  * an interrupt in the middle of a task switch..
 283                  */
 284                 int offset = pgd_index(address);
 285                 pgd_t *pgd, *pgd_k;
 286                 p4d_t *p4d, *p4d_k;
 287                 pud_t *pud, *pud_k;
 288                 pmd_t *pmd, *pmd_k;
 289                 pte_t *pte_k;
 290
 291                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 292                 pgd_k = init_mm.pgd + offset;
 293
 294                 if (!pgd_present(*pgd_k))
 295                         goto no_context;
 296                 set_pgd(pgd, *pgd_k);
 297
 298                 p4d = p4d_offset(pgd, address);
 299                 p4d_k = p4d_offset(pgd_k, address);
 300                 if (!p4d_present(*p4d_k))
 301                         goto no_context;
 302
 303                 pud = pud_offset(p4d, address);
 304                 pud_k = pud_offset(p4d_k, address);
 305                 if (!pud_present(*pud_k))
 306                         goto no_context;
 307
 308                 pmd = pmd_offset(pud, address);
 309                 pmd_k = pmd_offset(pud_k, address);
 310                 if (!pmd_present(*pmd_k))
 311                         goto no_context;
 312                 set_pmd(pmd, *pmd_k);
 313
 314                 pte_k = pte_offset_kernel(pmd_k, address);
 315                 if (!pte_present(*pte_k))
 316                         goto no_context;
 317                 return;
 318         }
 319 #endif
 320 }
 321 NOKPROBE_SYMBOL(__do_page_fault);
 322
 323 asmlinkage void do_page_fault(struct pt_regs *regs,
 324         unsigned long write, unsigned long address)
 325 {
 326         enum ctx_state prev_state;
 327
 328         prev_state = exception_enter();
 329         __do_page_fault(regs, write, address);
 330         exception_exit(prev_state);
 331 }
 332 NOKPROBE_SYMBOL(do_page_fault);