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         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         mmap_read_lock(mm);
 103         vma = find_vma(mm, address);
 104         if (!vma)
 105                 goto bad_area;
 106         if (vma->vm_start <= address)
 107                 goto good_area;
 108         if (!(vma->vm_flags & VM_GROWSDOWN))
 109                 goto bad_area;
 110         if (expand_stack(vma, address))
 111                 goto bad_area;
 112 /*
 113  * Ok, we have a good vm_area for this memory access, so
 114  * we can handle it..
 115  */
 116 good_area:
 117         si_code = SEGV_ACCERR;
 118
 119         if (write) {
 120                 if (!(vma->vm_flags & VM_WRITE))
 121                         goto bad_area;
 122                 flags |= FAULT_FLAG_WRITE;
 123         } else {
 124                 if (cpu_has_rixi) {
 125                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 126 #if 0
 127                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 128                                           raw_smp_processor_id(),
 129                                           current->comm, current->pid,
 130                                           field, address, write,
 131                                           field, regs->cp0_epc);
 132 #endif
 133                                 goto bad_area;
 134                         }
 135                         if (!(vma->vm_flags & VM_READ) &&
 136                             exception_epc(regs) != address) {
 137 #if 0
 138                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
 139                                           raw_smp_processor_id(),
 140                                           current->comm, current->pid,
 141                                           field, address, write,
 142                                           field, regs->cp0_epc);
 143 #endif
 144                                 goto bad_area;
 145                         }
 146                 } else {
 147                         if (unlikely(!vma_is_accessible(vma)))
 148                                 goto bad_area;
 149                 }
 150         }
 151
 152         /*
 153          * If for any reason at all we couldn't handle the fault,
 154          * make sure we exit gracefully rather than endlessly redo
 155          * the fault.
 156          */
 157         fault = handle_mm_fault(vma, address, flags, regs);
 158
 159         if (fault_signal_pending(fault, regs))
 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         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 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
 185         mmap_read_unlock(mm);
 186         return;
 187
 188 /*
 189  * Something tried to access memory that isn't in our memory map..
 190  * Fix it, but check if it's kernel or user first..
 191  */
 192 bad_area:
 193         mmap_read_unlock(mm);
 194
 195 bad_area_nosemaphore:
 196         /* User mode accesses just cause a SIGSEGV */
 197         if (user_mode(regs)) {
 198                 tsk->thread.cp0_badvaddr = address;
 199                 tsk->thread.error_code = write;
 200                 if (show_unhandled_signals &&
 201                     unhandled_signal(tsk, SIGSEGV) &&
 202                     __ratelimit(&ratelimit_state)) {
 203                         pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n",
 204                                 tsk->comm,
 205                                 write ? "write access to" : "read access from",
 206                                 field, address);
 207                         pr_info("epc = %0*lx in", field,
 208                                 (unsigned long) regs->cp0_epc);
 209                         print_vma_addr(KERN_CONT " ", regs->cp0_epc);
 210                         pr_cont("\n");
 211                         pr_info("ra  = %0*lx in", field,
 212                                 (unsigned long) regs->regs[31]);
 213                         print_vma_addr(KERN_CONT " ", regs->regs[31]);
 214                         pr_cont("\n");
 215                 }
 216                 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
 217                 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 218                 return;
 219         }
 220
 221 no_context:
 222         /* Are we prepared to handle this kernel fault?  */
 223         if (fixup_exception(regs)) {
 224                 current->thread.cp0_baduaddr = address;
 225                 return;
 226         }
 227
 228         /*
 229          * Oops. The kernel tried to access some bad page. We'll have to
 230          * terminate things with extreme prejudice.
 231          */
 232         bust_spinlocks(1);
 233
 234         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 235                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 236                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 237                field,  regs->regs[31]);
 238         die("Oops", regs);
 239
 240 out_of_memory:
 241         /*
 242          * We ran out of memory, call the OOM killer, and return the userspace
 243          * (which will retry the fault, or kill us if we got oom-killed).
 244          */
 245         mmap_read_unlock(mm);
 246         if (!user_mode(regs))
 247                 goto no_context;
 248         pagefault_out_of_memory();
 249         return;
 250
 251 do_sigbus:
 252         mmap_read_unlock(mm);
 253
 254         /* Kernel mode? Handle exceptions or die */
 255         if (!user_mode(regs))
 256                 goto no_context;
 257
 258         /*
 259          * Send a sigbus, regardless of whether we were in kernel
 260          * or user mode.
 261          */
 262 #if 0
 263         printk("do_page_fault() #3: sending SIGBUS to %s for "
 264                "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 265                tsk->comm,
 266                write ? "write access to" : "read access from",
 267                field, address,
 268                field, (unsigned long) regs->cp0_epc,
 269                field, (unsigned long) regs->regs[31]);
 270 #endif
 271         current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
 272         tsk->thread.cp0_badvaddr = address;
 273         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
 274
 275         return;
 276 #ifndef CONFIG_64BIT
 277 vmalloc_fault:
 278         {
 279                 /*
 280                  * Synchronize this task's top level page-table
 281                  * with the 'reference' page table.
 282                  *
 283                  * Do _not_ use "tsk" here. We might be inside
 284                  * an interrupt in the middle of a task switch..
 285                  */
 286                 int offset = pgd_index(address);
 287                 pgd_t *pgd, *pgd_k;
 288                 p4d_t *p4d, *p4d_k;
 289                 pud_t *pud, *pud_k;
 290                 pmd_t *pmd, *pmd_k;
 291                 pte_t *pte_k;
 292
 293                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 294                 pgd_k = init_mm.pgd + offset;
 295
 296                 if (!pgd_present(*pgd_k))
 297                         goto no_context;
 298                 set_pgd(pgd, *pgd_k);
 299
 300                 p4d = p4d_offset(pgd, address);
 301                 p4d_k = p4d_offset(pgd_k, address);
 302                 if (!p4d_present(*p4d_k))
 303                         goto no_context;
 304
 305                 pud = pud_offset(p4d, address);
 306                 pud_k = pud_offset(p4d_k, address);
 307                 if (!pud_present(*pud_k))
 308                         goto no_context;
 309
 310                 pmd = pmd_offset(pud, address);
 311                 pmd_k = pmd_offset(pud_k, address);
 312                 if (!pmd_present(*pmd_k))
 313                         goto no_context;
 314                 set_pmd(pmd, *pmd_k);
 315
 316                 pte_k = pte_offset_kernel(pmd_k, address);
 317                 if (!pte_present(*pte_k))
 318                         goto no_context;
 319                 return;
 320         }
 321 #endif
 322 }
 323
 324 asmlinkage void __kprobes 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 }