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/uaccess.h>
  26 #include <asm/ptrace.h>
  27 #include <asm/highmem.h>                /* For VMALLOC_END */
  28 #include <linux/kdebug.h>
  29
  30 /*
  31  * This routine handles page faults.  It determines the address,
  32  * and the problem, and then passes it off to one of the appropriate
  33  * routines.
  34  */
  35 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs, unsigned long write,
  36                               unsigned long address)
  37 {
  38         struct vm_area_struct * vma = NULL;
  39         struct task_struct *tsk = current;
  40         struct mm_struct *mm = tsk->mm;
  41         const int field = sizeof(unsigned long) * 2;
  42         siginfo_t info;
  43         int fault;
  44         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  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         if (user_mode(regs))
  95                 flags |= FAULT_FLAG_USER;
  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                 flags |= FAULT_FLAG_WRITE;
 118         } else {
 119                 if (cpu_has_rixi) {
 120                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 121 #if 0
 122                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 123                                           raw_smp_processor_id(),
 124                                           current->comm, current->pid,
 125                                           field, address, write,
 126                                           field, regs->cp0_epc);
 127 #endif
 128                                 goto bad_area;
 129                         }
 130                         if (!(vma->vm_flags & VM_READ)) {
 131 #if 0
 132                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
 133                                           raw_smp_processor_id(),
 134                                           current->comm, current->pid,
 135                                           field, address, write,
 136                                           field, regs->cp0_epc);
 137 #endif
 138                                 goto bad_area;
 139                         }
 140                 } else {
 141                         if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 142                                 goto bad_area;
 143                 }
 144         }
 145
 146         /*
 147          * If for any reason at all we couldn't handle the fault,
 148          * make sure we exit gracefully rather than endlessly redo
 149          * the fault.
 150          */
 151         fault = handle_mm_fault(mm, vma, address, flags);
 152
 153         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 154                 return;
 155
 156         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 157         if (unlikely(fault & VM_FAULT_ERROR)) {
 158                 if (fault & VM_FAULT_OOM)
 159                         goto out_of_memory;
 160                 else if (fault & VM_FAULT_SIGBUS)
 161                         goto do_sigbus;
 162                 BUG();
 163         }
 164         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 165                 if (fault & VM_FAULT_MAJOR) {
 166                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 167                                                   regs, address);
 168                         tsk->maj_flt++;
 169                 } else {
 170                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 171                                                   regs, address);
 172                         tsk->min_flt++;
 173                 }
 174                 if (fault & VM_FAULT_RETRY) {
 175                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 176                         flags |= FAULT_FLAG_TRIED;
 177
 178                         /*
 179                          * No need to up_read(&mm->mmap_sem) as we would
 180                          * have already released it in __lock_page_or_retry
 181                          * in mm/filemap.c.
 182                          */
 183
 184                         goto retry;
 185                 }
 186         }
 187
 188         up_read(&mm->mmap_sem);
 189         return;
 190
 191 /*
 192  * Something tried to access memory that isn't in our memory map..
 193  * Fix it, but check if it's kernel or user first..
 194  */
 195 bad_area:
 196         up_read(&mm->mmap_sem);
 197
 198 bad_area_nosemaphore:
 199         /* User mode accesses just cause a SIGSEGV */
 200         if (user_mode(regs)) {
 201                 tsk->thread.cp0_badvaddr = address;
 202                 tsk->thread.error_code = write;
 203 #if 0
 204                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 205                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 206                        tsk->comm,
 207                        write ? "write access to" : "read access from",
 208                        field, address,
 209                        field, (unsigned long) regs->cp0_epc,
 210                        field, (unsigned long) regs->regs[31]);
 211 #endif
 212                 info.si_signo = SIGSEGV;
 213                 info.si_errno = 0;
 214                 /* info.si_code has been set above */
 215                 info.si_addr = (void __user *) address;
 216                 force_sig_info(SIGSEGV, &info, tsk);
 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         up_read(&mm->mmap_sem);
 245         if (!user_mode(regs))
 246                 goto no_context;
 247         pagefault_out_of_memory();
 248         return;
 249
 250 do_sigbus:
 251         up_read(&mm->mmap_sem);
 252
 253         /* Kernel mode? Handle exceptions or die */
 254         if (!user_mode(regs))
 255                 goto no_context;
 256         else
 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         tsk->thread.cp0_badvaddr = address;
 271         info.si_signo = SIGBUS;
 272         info.si_errno = 0;
 273         info.si_code = BUS_ADRERR;
 274         info.si_addr = (void __user *) address;
 275         force_sig_info(SIGBUS, &info, tsk);
 276
 277         return;
 278 #ifndef CONFIG_64BIT
 279 vmalloc_fault:
 280         {
 281                 /*
 282                  * Synchronize this task's top level page-table
 283                  * with the 'reference' page table.
 284                  *
 285                  * Do _not_ use "tsk" here. We might be inside
 286                  * an interrupt in the middle of a task switch..
 287                  */
 288                 int offset = __pgd_offset(address);
 289                 pgd_t *pgd, *pgd_k;
 290                 pud_t *pud, *pud_k;
 291                 pmd_t *pmd, *pmd_k;
 292                 pte_t *pte_k;
 293
 294                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 295                 pgd_k = init_mm.pgd + offset;
 296
 297                 if (!pgd_present(*pgd_k))
 298                         goto no_context;
 299                 set_pgd(pgd, *pgd_k);
 300
 301                 pud = pud_offset(pgd, address);
 302                 pud_k = pud_offset(pgd_k, address);
 303                 if (!pud_present(*pud_k))
 304                         goto no_context;
 305
 306                 pmd = pmd_offset(pud, address);
 307                 pmd_k = pmd_offset(pud_k, address);
 308                 if (!pmd_present(*pmd_k))
 309                         goto no_context;
 310                 set_pmd(pmd, *pmd_k);
 311
 312                 pte_k = pte_offset_kernel(pmd_k, address);
 313                 if (!pte_present(*pte_k))
 314                         goto no_context;
 315                 return;
 316         }
 317 #endif
 318 }