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
  47 #if 0
  48         printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(),
  49                current->comm, current->pid, field, address, write,
  50                field, regs->cp0_epc);
  51 #endif
  52
  53 #ifdef CONFIG_KPROBES
  54         /*
  55          * This is to notify the fault handler of the kprobes.  The
  56          * exception code is redundant as it is also carried in REGS,
  57          * but we pass it anyhow.
  58          */
  59         if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
  60                        (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP)
  61                 return;
  62 #endif
  63
  64         info.si_code = SEGV_MAPERR;
  65
  66         /*
  67          * We fault-in kernel-space virtual memory on-demand. The
  68          * 'reference' page table is init_mm.pgd.
  69          *
  70          * NOTE! We MUST NOT take any locks for this case. We may
  71          * be in an interrupt or a critical region, and should
  72          * only copy the information from the master page table,
  73          * nothing more.
  74          */
  75 #ifdef CONFIG_64BIT
  76 # define VMALLOC_FAULT_TARGET no_context
  77 #else
  78 # define VMALLOC_FAULT_TARGET vmalloc_fault
  79 #endif
  80
  81         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  82                 goto VMALLOC_FAULT_TARGET;
  83 #ifdef MODULE_START
  84         if (unlikely(address >= MODULE_START && address < MODULE_END))
  85                 goto VMALLOC_FAULT_TARGET;
  86 #endif
  87
  88         /*
  89          * If we're in an interrupt or have no user
  90          * context, we must not take the fault..
  91          */
  92         if (in_atomic() || !mm)
  93                 goto bad_area_nosemaphore;
  94
  95         if (user_mode(regs))
  96                 flags |= FAULT_FLAG_USER;
  97 retry:
  98         down_read(&mm->mmap_sem);
  99         vma = find_vma(mm, address);
 100         if (!vma)
 101                 goto bad_area;
 102         if (vma->vm_start <= address)
 103                 goto good_area;
 104         if (!(vma->vm_flags & VM_GROWSDOWN))
 105                 goto bad_area;
 106         if (expand_stack(vma, address))
 107                 goto bad_area;
 108 /*
 109  * Ok, we have a good vm_area for this memory access, so
 110  * we can handle it..
 111  */
 112 good_area:
 113         info.si_code = SEGV_ACCERR;
 114
 115         if (write) {
 116                 if (!(vma->vm_flags & VM_WRITE))
 117                         goto bad_area;
 118                 flags |= FAULT_FLAG_WRITE;
 119         } else {
 120                 if (cpu_has_rixi) {
 121                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 122 #if 0
 123                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 124                                           raw_smp_processor_id(),
 125                                           current->comm, current->pid,
 126                                           field, address, write,
 127                                           field, regs->cp0_epc);
 128 #endif
 129                                 goto bad_area;
 130                         }
 131                         if (!(vma->vm_flags & VM_READ)) {
 132 #if 0
 133                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
 134                                           raw_smp_processor_id(),
 135                                           current->comm, current->pid,
 136                                           field, address, write,
 137                                           field, regs->cp0_epc);
 138 #endif
 139                                 goto bad_area;
 140                         }
 141                 } else {
 142                         if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 143                                 goto bad_area;
 144                 }
 145         }
 146
 147         /*
 148          * If for any reason at all we couldn't handle the fault,
 149          * make sure we exit gracefully rather than endlessly redo
 150          * the fault.
 151          */
 152         fault = handle_mm_fault(mm, vma, address, flags);
 153
 154         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 155                 return;
 156
 157         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 158         if (unlikely(fault & VM_FAULT_ERROR)) {
 159                 if (fault & VM_FAULT_OOM)
 160                         goto out_of_memory;
 161                 else if (fault & VM_FAULT_SIGSEGV)
 162                         goto bad_area;
 163                 else if (fault & VM_FAULT_SIGBUS)
 164                         goto do_sigbus;
 165                 BUG();
 166         }
 167         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 168                 if (fault & VM_FAULT_MAJOR) {
 169                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 170                                                   regs, address);
 171                         tsk->maj_flt++;
 172                 } else {
 173                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 174                                                   regs, address);
 175                         tsk->min_flt++;
 176                 }
 177                 if (fault & VM_FAULT_RETRY) {
 178                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 179                         flags |= FAULT_FLAG_TRIED;
 180
 181                         /*
 182                          * No need to up_read(&mm->mmap_sem) as we would
 183                          * have already released it in __lock_page_or_retry
 184                          * in mm/filemap.c.
 185                          */
 186
 187                         goto retry;
 188                 }
 189         }
 190
 191         up_read(&mm->mmap_sem);
 192         return;
 193
 194 /*
 195  * Something tried to access memory that isn't in our memory map..
 196  * Fix it, but check if it's kernel or user first..
 197  */
 198 bad_area:
 199         up_read(&mm->mmap_sem);
 200
 201 bad_area_nosemaphore:
 202         /* User mode accesses just cause a SIGSEGV */
 203         if (user_mode(regs)) {
 204                 tsk->thread.cp0_badvaddr = address;
 205                 tsk->thread.error_code = write;
 206 #if 0
 207                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 208                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 209                        tsk->comm,
 210                        write ? "write access to" : "read access from",
 211                        field, address,
 212                        field, (unsigned long) regs->cp0_epc,
 213                        field, (unsigned long) regs->regs[31]);
 214 #endif
 215                 info.si_signo = SIGSEGV;
 216                 info.si_errno = 0;
 217                 /* info.si_code has been set above */
 218                 info.si_addr = (void __user *) address;
 219                 force_sig_info(SIGSEGV, &info, tsk);
 220                 return;
 221         }
 222
 223 no_context:
 224         /* Are we prepared to handle this kernel fault?  */
 225         if (fixup_exception(regs)) {
 226                 current->thread.cp0_baduaddr = address;
 227                 return;
 228         }
 229
 230         /*
 231          * Oops. The kernel tried to access some bad page. We'll have to
 232          * terminate things with extreme prejudice.
 233          */
 234         bust_spinlocks(1);
 235
 236         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 237                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 238                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 239                field,  regs->regs[31]);
 240         die("Oops", regs);
 241
 242 out_of_memory:
 243         /*
 244          * We ran out of memory, call the OOM killer, and return the userspace
 245          * (which will retry the fault, or kill us if we got oom-killed).
 246          */
 247         up_read(&mm->mmap_sem);
 248         if (!user_mode(regs))
 249                 goto no_context;
 250         pagefault_out_of_memory();
 251         return;
 252
 253 do_sigbus:
 254         up_read(&mm->mmap_sem);
 255
 256         /* Kernel mode? Handle exceptions or die */
 257         if (!user_mode(regs))
 258                 goto no_context;
 259         else
 260         /*
 261          * Send a sigbus, regardless of whether we were in kernel
 262          * or user mode.
 263          */
 264 #if 0
 265                 printk("do_page_fault() #3: sending SIGBUS to %s for "
 266                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 267                        tsk->comm,
 268                        write ? "write access to" : "read access from",
 269                        field, address,
 270                        field, (unsigned long) regs->cp0_epc,
 271                        field, (unsigned long) regs->regs[31]);
 272 #endif
 273         tsk->thread.cp0_badvaddr = address;
 274         info.si_signo = SIGBUS;
 275         info.si_errno = 0;
 276         info.si_code = BUS_ADRERR;
 277         info.si_addr = (void __user *) address;
 278         force_sig_info(SIGBUS, &info, tsk);
 279
 280         return;
 281 #ifndef CONFIG_64BIT
 282 vmalloc_fault:
 283         {
 284                 /*
 285                  * Synchronize this task's top level page-table
 286                  * with the 'reference' page table.
 287                  *
 288                  * Do _not_ use "tsk" here. We might be inside
 289                  * an interrupt in the middle of a task switch..
 290                  */
 291                 int offset = __pgd_offset(address);
 292                 pgd_t *pgd, *pgd_k;
 293                 pud_t *pud, *pud_k;
 294                 pmd_t *pmd, *pmd_k;
 295                 pte_t *pte_k;
 296
 297                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 298                 pgd_k = init_mm.pgd + offset;
 299
 300                 if (!pgd_present(*pgd_k))
 301                         goto no_context;
 302                 set_pgd(pgd, *pgd_k);
 303
 304                 pud = pud_offset(pgd, address);
 305                 pud_k = pud_offset(pgd_k, address);
 306                 if (!pud_present(*pud_k))
 307                         goto no_context;
 308
 309                 pmd = pmd_offset(pud, address);
 310                 pmd_k = pmd_offset(pud_k, address);
 311                 if (!pmd_present(*pmd_k))
 312                         goto no_context;
 313                 set_pmd(pmd, *pmd_k);
 314
 315                 pte_k = pte_offset_kernel(pmd_k, address);
 316                 if (!pte_present(*pte_k))
 317                         goto no_context;
 318                 return;
 319         }
 320 #endif
 321 }
 322
 323 asmlinkage void __kprobes 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 }