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/signal.h>
   9 #include <linux/sched.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/kernel.h>
  12 #include <linux/errno.h>
  13 #include <linux/string.h>
  14 #include <linux/types.h>
  15 #include <linux/ptrace.h>
  16 #include <linux/mman.h>
  17 #include <linux/mm.h>
  18 #include <linux/smp.h>
  19 #include <linux/module.h>
  20 #include <linux/kprobes.h>
  21 #include <linux/perf_event.h>
  22
  23 #include <asm/branch.h>
  24 #include <asm/mmu_context.h>
  25 #include <asm/system.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 asmlinkage 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
  46 #if 0
  47         printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(),
  48                current->comm, current->pid, field, address, write,
  49                field, regs->cp0_epc);
  50 #endif
  51
  52 #ifdef CONFIG_KPROBES
  53         /*
  54          * This is to notify the fault handler of the kprobes.  The
  55          * exception code is redundant as it is also carried in REGS,
  56          * but we pass it anyhow.
  57          */
  58         if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
  59                        (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP)
  60                 return;
  61 #endif
  62
  63         info.si_code = SEGV_MAPERR;
  64
  65         /*
  66          * We fault-in kernel-space virtual memory on-demand. The
  67          * 'reference' page table is init_mm.pgd.
  68          *
  69          * NOTE! We MUST NOT take any locks for this case. We may
  70          * be in an interrupt or a critical region, and should
  71          * only copy the information from the master page table,
  72          * nothing more.
  73          */
  74 #ifdef CONFIG_64BIT
  75 # define VMALLOC_FAULT_TARGET no_context
  76 #else
  77 # define VMALLOC_FAULT_TARGET vmalloc_fault
  78 #endif
  79
  80         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  81                 goto VMALLOC_FAULT_TARGET;
  82 #ifdef MODULE_START
  83         if (unlikely(address >= MODULE_START && address < MODULE_END))
  84                 goto VMALLOC_FAULT_TARGET;
  85 #endif
  86
  87         /*
  88          * If we're in an interrupt or have no user
  89          * context, we must not take the fault..
  90          */
  91         if (in_atomic() || !mm)
  92                 goto bad_area_nosemaphore;
  93
  94         down_read(&mm->mmap_sem);
  95         vma = find_vma(mm, address);
  96         if (!vma)
  97                 goto bad_area;
  98         if (vma->vm_start <= address)
  99                 goto good_area;
 100         if (!(vma->vm_flags & VM_GROWSDOWN))
 101                 goto bad_area;
 102         if (expand_stack(vma, address))
 103                 goto bad_area;
 104 /*
 105  * Ok, we have a good vm_area for this memory access, so
 106  * we can handle it..
 107  */
 108 good_area:
 109         info.si_code = SEGV_ACCERR;
 110
 111         if (write) {
 112                 if (!(vma->vm_flags & VM_WRITE))
 113                         goto bad_area;
 114         } else {
 115                 if (kernel_uses_smartmips_rixi) {
 116                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 117 #if 0
 118                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 119                                           raw_smp_processor_id(),
 120                                           current->comm, current->pid,
 121                                           field, address, write,
 122                                           field, regs->cp0_epc);
 123 #endif
 124                                 goto bad_area;
 125                         }
 126                         if (!(vma->vm_flags & VM_READ)) {
 127 #if 0
 128                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
 129                                           raw_smp_processor_id(),
 130                                           current->comm, current->pid,
 131                                           field, address, write,
 132                                           field, regs->cp0_epc);
 133 #endif
 134                                 goto bad_area;
 135                         }
 136                 } else {
 137                         if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 138                                 goto bad_area;
 139                 }
 140         }
 141
 142         /*
 143          * If for any reason at all we couldn't handle the fault,
 144          * make sure we exit gracefully rather than endlessly redo
 145          * the fault.
 146          */
 147         fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
 148         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address);
 149         if (unlikely(fault & VM_FAULT_ERROR)) {
 150                 if (fault & VM_FAULT_OOM)
 151                         goto out_of_memory;
 152                 else if (fault & VM_FAULT_SIGBUS)
 153                         goto do_sigbus;
 154                 BUG();
 155         }
 156         if (fault & VM_FAULT_MAJOR) {
 157                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
 158                                 1, 0, regs, address);
 159                 tsk->maj_flt++;
 160         } else {
 161                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
 162                                 1, 0, regs, address);
 163                 tsk->min_flt++;
 164         }
 165
 166         up_read(&mm->mmap_sem);
 167         return;
 168
 169 /*
 170  * Something tried to access memory that isn't in our memory map..
 171  * Fix it, but check if it's kernel or user first..
 172  */
 173 bad_area:
 174         up_read(&mm->mmap_sem);
 175
 176 bad_area_nosemaphore:
 177         /* User mode accesses just cause a SIGSEGV */
 178         if (user_mode(regs)) {
 179                 tsk->thread.cp0_badvaddr = address;
 180                 tsk->thread.error_code = write;
 181 #if 0
 182                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 183                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 184                        tsk->comm,
 185                        write ? "write access to" : "read access from",
 186                        field, address,
 187                        field, (unsigned long) regs->cp0_epc,
 188                        field, (unsigned long) regs->regs[31]);
 189 #endif
 190                 info.si_signo = SIGSEGV;
 191                 info.si_errno = 0;
 192                 /* info.si_code has been set above */
 193                 info.si_addr = (void __user *) address;
 194                 force_sig_info(SIGSEGV, &info, tsk);
 195                 return;
 196         }
 197
 198 no_context:
 199         /* Are we prepared to handle this kernel fault?  */
 200         if (fixup_exception(regs)) {
 201                 current->thread.cp0_baduaddr = address;
 202                 return;
 203         }
 204
 205         /*
 206          * Oops. The kernel tried to access some bad page. We'll have to
 207          * terminate things with extreme prejudice.
 208          */
 209         bust_spinlocks(1);
 210
 211         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 212                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 213                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 214                field,  regs->regs[31]);
 215         die("Oops", regs);
 216
 217 out_of_memory:
 218         /*
 219          * We ran out of memory, call the OOM killer, and return the userspace
 220          * (which will retry the fault, or kill us if we got oom-killed).
 221          */
 222         up_read(&mm->mmap_sem);
 223         pagefault_out_of_memory();
 224         return;
 225
 226 do_sigbus:
 227         up_read(&mm->mmap_sem);
 228
 229         /* Kernel mode? Handle exceptions or die */
 230         if (!user_mode(regs))
 231                 goto no_context;
 232         else
 233         /*
 234          * Send a sigbus, regardless of whether we were in kernel
 235          * or user mode.
 236          */
 237 #if 0
 238                 printk("do_page_fault() #3: sending SIGBUS to %s for "
 239                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 240                        tsk->comm,
 241                        write ? "write access to" : "read access from",
 242                        field, address,
 243                        field, (unsigned long) regs->cp0_epc,
 244                        field, (unsigned long) regs->regs[31]);
 245 #endif
 246         tsk->thread.cp0_badvaddr = address;
 247         info.si_signo = SIGBUS;
 248         info.si_errno = 0;
 249         info.si_code = BUS_ADRERR;
 250         info.si_addr = (void __user *) address;
 251         force_sig_info(SIGBUS, &info, tsk);
 252
 253         return;
 254 #ifndef CONFIG_64BIT
 255 vmalloc_fault:
 256         {
 257                 /*
 258                  * Synchronize this task's top level page-table
 259                  * with the 'reference' page table.
 260                  *
 261                  * Do _not_ use "tsk" here. We might be inside
 262                  * an interrupt in the middle of a task switch..
 263                  */
 264                 int offset = __pgd_offset(address);
 265                 pgd_t *pgd, *pgd_k;
 266                 pud_t *pud, *pud_k;
 267                 pmd_t *pmd, *pmd_k;
 268                 pte_t *pte_k;
 269
 270                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 271                 pgd_k = init_mm.pgd + offset;
 272
 273                 if (!pgd_present(*pgd_k))
 274                         goto no_context;
 275                 set_pgd(pgd, *pgd_k);
 276
 277                 pud = pud_offset(pgd, address);
 278                 pud_k = pud_offset(pgd_k, address);
 279                 if (!pud_present(*pud_k))
 280                         goto no_context;
 281
 282                 pmd = pmd_offset(pud, address);
 283                 pmd_k = pmd_offset(pud_k, address);
 284                 if (!pmd_present(*pmd_k))
 285                         goto no_context;
 286                 set_pmd(pmd, *pmd_k);
 287
 288                 pte_k = pte_offset_kernel(pmd_k, address);
 289                 if (!pte_present(*pte_k))
 290                         goto no_context;
 291                 return;
 292         }
 293 #endif
 294 }