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/mman.h>
  18 #include <linux/mm.h>
  19 #include <linux/smp.h>
  20 #include <linux/module.h>
  21 #include <linux/kprobes.h>
  22 #include <linux/perf_event.h>
  23
  24 #include <asm/branch.h>
  25 #include <asm/mmu_context.h>
  26 #include <asm/uaccess.h>
  27 #include <asm/ptrace.h>
  28 #include <asm/highmem.h>                /* For VMALLOC_END */
  29 #include <linux/kdebug.h>
  30
  31 /*
  32  * This routine handles page faults.  It determines the address,
  33  * and the problem, and then passes it off to one of the appropriate
  34  * routines.
  35  */
  36 static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
  37         unsigned long address)
  38 {
  39         struct vm_area_struct * vma = NULL;
  40         struct task_struct *tsk = current;
  41         struct mm_struct *mm = tsk->mm;
  42         const int field = sizeof(unsigned long) * 2;
  43         siginfo_t info;
  44         int fault;
  45         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
  46                                                  (write ? FAULT_FLAG_WRITE : 0);
  47
  48 #if 0
  49         printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(),
  50                current->comm, current->pid, field, address, write,
  51                field, regs->cp0_epc);
  52 #endif
  53
  54 #ifdef CONFIG_KPROBES
  55         /*
  56          * This is to notify the fault handler of the kprobes.  The
  57          * exception code is redundant as it is also carried in REGS,
  58          * but we pass it anyhow.
  59          */
  60         if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
  61                        (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP)
  62                 return;
  63 #endif
  64
  65         info.si_code = SEGV_MAPERR;
  66
  67         /*
  68          * We fault-in kernel-space virtual memory on-demand. The
  69          * 'reference' page table is init_mm.pgd.
  70          *
  71          * NOTE! We MUST NOT take any locks for this case. We may
  72          * be in an interrupt or a critical region, and should
  73          * only copy the information from the master page table,
  74          * nothing more.
  75          */
  76 #ifdef CONFIG_64BIT
  77 # define VMALLOC_FAULT_TARGET no_context
  78 #else
  79 # define VMALLOC_FAULT_TARGET vmalloc_fault
  80 #endif
  81
  82         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  83                 goto VMALLOC_FAULT_TARGET;
  84 #ifdef MODULE_START
  85         if (unlikely(address >= MODULE_START && address < MODULE_END))
  86                 goto VMALLOC_FAULT_TARGET;
  87 #endif
  88
  89         /*
  90          * If we're in an interrupt or have no user
  91          * context, we must not take the fault..
  92          */
  93         if (in_atomic() || !mm)
  94                 goto bad_area_nosemaphore;
  95
  96 retry:
  97         down_read(&mm->mmap_sem);
  98         vma = find_vma(mm, address);
  99         if (!vma)
 100                 goto bad_area;
 101         if (vma->vm_start <= address)
 102                 goto good_area;
 103         if (!(vma->vm_flags & VM_GROWSDOWN))
 104                 goto bad_area;
 105         if (expand_stack(vma, address))
 106                 goto bad_area;
 107 /*
 108  * Ok, we have a good vm_area for this memory access, so
 109  * we can handle it..
 110  */
 111 good_area:
 112         info.si_code = SEGV_ACCERR;
 113
 114         if (write) {
 115                 if (!(vma->vm_flags & VM_WRITE))
 116                         goto bad_area;
 117         } else {
 118                 if (cpu_has_rixi) {
 119                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 120 #if 0
 121                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 122                                           raw_smp_processor_id(),
 123                                           current->comm, current->pid,
 124                                           field, address, write,
 125                                           field, regs->cp0_epc);
 126 #endif
 127                                 goto bad_area;
 128                         }
 129                         if (!(vma->vm_flags & VM_READ)) {
 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 (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 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(mm, vma, address, flags);
 151
 152         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 153                 return;
 154
 155         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 156         if (unlikely(fault & VM_FAULT_ERROR)) {
 157                 if (fault & VM_FAULT_OOM)
 158                         goto out_of_memory;
 159                 else if (fault & VM_FAULT_SIGBUS)
 160                         goto do_sigbus;
 161                 BUG();
 162         }
 163         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 164                 if (fault & VM_FAULT_MAJOR) {
 165                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 166                                                   regs, address);
 167                         tsk->maj_flt++;
 168                 } else {
 169                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 170                                                   regs, address);
 171                         tsk->min_flt++;
 172                 }
 173                 if (fault & VM_FAULT_RETRY) {
 174                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 175                         flags |= FAULT_FLAG_TRIED;
 176
 177                         /*
 178                          * No need to up_read(&mm->mmap_sem) as we would
 179                          * have already released it in __lock_page_or_retry
 180                          * in mm/filemap.c.
 181                          */
 182
 183                         goto retry;
 184                 }
 185         }
 186
 187         up_read(&mm->mmap_sem);
 188         return;
 189
 190 /*
 191  * Something tried to access memory that isn't in our memory map..
 192  * Fix it, but check if it's kernel or user first..
 193  */
 194 bad_area:
 195         up_read(&mm->mmap_sem);
 196
 197 bad_area_nosemaphore:
 198         /* User mode accesses just cause a SIGSEGV */
 199         if (user_mode(regs)) {
 200                 tsk->thread.cp0_badvaddr = address;
 201                 tsk->thread.error_code = write;
 202 #if 0
 203                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 204                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 205                        tsk->comm,
 206                        write ? "write access to" : "read access from",
 207                        field, address,
 208                        field, (unsigned long) regs->cp0_epc,
 209                        field, (unsigned long) regs->regs[31]);
 210 #endif
 211                 info.si_signo = SIGSEGV;
 212                 info.si_errno = 0;
 213                 /* info.si_code has been set above */
 214                 info.si_addr = (void __user *) address;
 215                 force_sig_info(SIGSEGV, &info, tsk);
 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         up_read(&mm->mmap_sem);
 244         if (!user_mode(regs))
 245                 goto no_context;
 246         pagefault_out_of_memory();
 247         return;
 248
 249 do_sigbus:
 250         up_read(&mm->mmap_sem);
 251
 252         /* Kernel mode? Handle exceptions or die */
 253         if (!user_mode(regs))
 254                 goto no_context;
 255         else
 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         tsk->thread.cp0_badvaddr = address;
 270         info.si_signo = SIGBUS;
 271         info.si_errno = 0;
 272         info.si_code = BUS_ADRERR;
 273         info.si_addr = (void __user *) address;
 274         force_sig_info(SIGBUS, &info, tsk);
 275
 276         return;
 277 #ifndef CONFIG_64BIT
 278 vmalloc_fault:
 279         {
 280                 /*
 281                  * Synchronize this task's top level page-table
 282                  * with the 'reference' page table.
 283                  *
 284                  * Do _not_ use "tsk" here. We might be inside
 285                  * an interrupt in the middle of a task switch..
 286                  */
 287                 int offset = __pgd_offset(address);
 288                 pgd_t *pgd, *pgd_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                 pud = pud_offset(pgd, address);
 301                 pud_k = pud_offset(pgd_k, address);
 302                 if (!pud_present(*pud_k))
 303                         goto no_context;
 304
 305                 pmd = pmd_offset(pud, address);
 306                 pmd_k = pmd_offset(pud_k, address);
 307                 if (!pmd_present(*pmd_k))
 308                         goto no_context;
 309                 set_pmd(pmd, *pmd_k);
 310
 311                 pte_k = pte_offset_kernel(pmd_k, address);
 312                 if (!pte_present(*pte_k))
 313                         goto no_context;
 314                 return;
 315         }
 316 #endif
 317 }
 318
 319 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 320         unsigned long write, unsigned long address)
 321 {
 322         enum ctx_state prev_state;
 323
 324         prev_state = exception_enter();
 325         __do_page_fault(regs, write, address);
 326         exception_exit(prev_state);
 327 }