arch/xtensa/mm/fault.c

   1 // TODO VM_EXEC flag work-around, cache aliasing
   2 /*
   3  * arch/xtensa/mm/fault.c
   4  *
   5  * This file is subject to the terms and conditions of the GNU General Public
   6  * License.  See the file "COPYING" in the main directory of this archive
   7  * for more details.
   8  *
   9  * Copyright (C) 2001 - 2010 Tensilica Inc.
  10  *
  11  * Chris Zankel <chris@zankel.net>
  12  * Joe Taylor   <joe@tensilica.com, joetylr@yahoo.com>
  13  */
  14
  15 #include <linux/mm.h>
  16 #include <linux/extable.h>
  17 #include <linux/hardirq.h>
  18 #include <linux/perf_event.h>
  19 #include <linux/uaccess.h>
  20 #include <asm/mmu_context.h>
  21 #include <asm/cacheflush.h>
  22 #include <asm/hardirq.h>
  23
  24 DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
  25 void bad_page_fault(struct pt_regs*, unsigned long, int);
  26
  27 /*
  28  * This routine handles page faults.  It determines the address,
  29  * and the problem, and then passes it off to one of the appropriate
  30  * routines.
  31  *
  32  * Note: does not handle Miss and MultiHit.
  33  */
  34
  35 void do_page_fault(struct pt_regs *regs)
  36 {
  37         struct vm_area_struct * vma;
  38         struct mm_struct *mm = current->mm;
  39         unsigned int exccause = regs->exccause;
  40         unsigned int address = regs->excvaddr;
  41         int code;
  42
  43         int is_write, is_exec;
  44         vm_fault_t fault;
  45         unsigned int flags = FAULT_FLAG_DEFAULT;
  46
  47         code = SEGV_MAPERR;
  48
  49         /* We fault-in kernel-space virtual memory on-demand. The
  50          * 'reference' page table is init_mm.pgd.
  51          */
  52         if (address >= TASK_SIZE && !user_mode(regs))
  53                 goto vmalloc_fault;
  54
  55         /* If we're in an interrupt or have no user
  56          * context, we must not take the fault..
  57          */
  58         if (faulthandler_disabled() || !mm) {
  59                 bad_page_fault(regs, address, SIGSEGV);
  60                 return;
  61         }
  62
  63         is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
  64         is_exec =  (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
  65                     exccause == EXCCAUSE_ITLB_MISS ||
  66                     exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
  67
  68         pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
  69                  current->comm, current->pid,
  70                  address, exccause, regs->pc,
  71                  is_write ? "w" : "", is_exec ? "x" : "");
  72
  73         if (user_mode(regs))
  74                 flags |= FAULT_FLAG_USER;
  75
  76         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
  77
  78 retry:
  79         mmap_read_lock(mm);
  80         vma = find_vma(mm, address);
  81
  82         if (!vma)
  83                 goto bad_area;
  84         if (vma->vm_start <= address)
  85                 goto good_area;
  86         if (!(vma->vm_flags & VM_GROWSDOWN))
  87                 goto bad_area;
  88         if (expand_stack(vma, address))
  89                 goto bad_area;
  90
  91         /* Ok, we have a good vm_area for this memory access, so
  92          * we can handle it..
  93          */
  94
  95 good_area:
  96         code = SEGV_ACCERR;
  97
  98         if (is_write) {
  99                 if (!(vma->vm_flags & VM_WRITE))
 100                         goto bad_area;
 101                 flags |= FAULT_FLAG_WRITE;
 102         } else if (is_exec) {
 103                 if (!(vma->vm_flags & VM_EXEC))
 104                         goto bad_area;
 105         } else  /* Allow read even from write-only pages. */
 106                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 107                         goto bad_area;
 108
 109         /* If for any reason at all we couldn't handle the fault,
 110          * make sure we exit gracefully rather than endlessly redo
 111          * the fault.
 112          */
 113         fault = handle_mm_fault(vma, address, flags, regs);
 114
 115         if (fault_signal_pending(fault, regs))
 116                 return;
 117
 118         if (unlikely(fault & VM_FAULT_ERROR)) {
 119                 if (fault & VM_FAULT_OOM)
 120                         goto out_of_memory;
 121                 else if (fault & VM_FAULT_SIGSEGV)
 122                         goto bad_area;
 123                 else if (fault & VM_FAULT_SIGBUS)
 124                         goto do_sigbus;
 125                 BUG();
 126         }
 127         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 128                 if (fault & VM_FAULT_RETRY) {
 129                         flags |= FAULT_FLAG_TRIED;
 130
 131                          /* No need to mmap_read_unlock(mm) as we would
 132                          * have already released it in __lock_page_or_retry
 133                          * in mm/filemap.c.
 134                          */
 135
 136                         goto retry;
 137                 }
 138         }
 139
 140         mmap_read_unlock(mm);
 141         return;
 142
 143         /* Something tried to access memory that isn't in our memory map..
 144          * Fix it, but check if it's kernel or user first..
 145          */
 146 bad_area:
 147         mmap_read_unlock(mm);
 148         if (user_mode(regs)) {
 149                 current->thread.bad_vaddr = address;
 150                 current->thread.error_code = is_write;
 151                 force_sig_fault(SIGSEGV, code, (void *) address);
 152                 return;
 153         }
 154         bad_page_fault(regs, address, SIGSEGV);
 155         return;
 156
 157
 158         /* We ran out of memory, or some other thing happened to us that made
 159          * us unable to handle the page fault gracefully.
 160          */
 161 out_of_memory:
 162         mmap_read_unlock(mm);
 163         if (!user_mode(regs))
 164                 bad_page_fault(regs, address, SIGKILL);
 165         else
 166                 pagefault_out_of_memory();
 167         return;
 168
 169 do_sigbus:
 170         mmap_read_unlock(mm);
 171
 172         /* Send a sigbus, regardless of whether we were in kernel
 173          * or user mode.
 174          */
 175         current->thread.bad_vaddr = address;
 176         force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
 177
 178         /* Kernel mode? Handle exceptions or die */
 179         if (!user_mode(regs))
 180                 bad_page_fault(regs, address, SIGBUS);
 181         return;
 182
 183 vmalloc_fault:
 184         {
 185                 /* Synchronize this task's top level page-table
 186                  * with the 'reference' page table.
 187                  */
 188                 struct mm_struct *act_mm = current->active_mm;
 189                 int index = pgd_index(address);
 190                 pgd_t *pgd, *pgd_k;
 191                 p4d_t *p4d, *p4d_k;
 192                 pud_t *pud, *pud_k;
 193                 pmd_t *pmd, *pmd_k;
 194                 pte_t *pte_k;
 195
 196                 if (act_mm == NULL)
 197                         goto bad_page_fault;
 198
 199                 pgd = act_mm->pgd + index;
 200                 pgd_k = init_mm.pgd + index;
 201
 202                 if (!pgd_present(*pgd_k))
 203                         goto bad_page_fault;
 204
 205                 pgd_val(*pgd) = pgd_val(*pgd_k);
 206
 207                 p4d = p4d_offset(pgd, address);
 208                 p4d_k = p4d_offset(pgd_k, address);
 209                 if (!p4d_present(*p4d) || !p4d_present(*p4d_k))
 210                         goto bad_page_fault;
 211
 212                 pud = pud_offset(p4d, address);
 213                 pud_k = pud_offset(p4d_k, address);
 214                 if (!pud_present(*pud) || !pud_present(*pud_k))
 215                         goto bad_page_fault;
 216
 217                 pmd = pmd_offset(pud, address);
 218                 pmd_k = pmd_offset(pud_k, address);
 219                 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 220                         goto bad_page_fault;
 221
 222                 pmd_val(*pmd) = pmd_val(*pmd_k);
 223                 pte_k = pte_offset_kernel(pmd_k, address);
 224
 225                 if (!pte_present(*pte_k))
 226                         goto bad_page_fault;
 227                 return;
 228         }
 229 bad_page_fault:
 230         bad_page_fault(regs, address, SIGKILL);
 231         return;
 232 }
 233
 234
 235 void
 236 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 237 {
 238         extern void die(const char*, struct pt_regs*, long);
 239         const struct exception_table_entry *entry;
 240
 241         /* Are we prepared to handle this kernel fault?  */
 242         if ((entry = search_exception_tables(regs->pc)) != NULL) {
 243                 pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
 244                          current->comm, regs->pc, entry->fixup);
 245                 current->thread.bad_uaddr = address;
 246                 regs->pc = entry->fixup;
 247                 return;
 248         }
 249
 250         /* Oops. The kernel tried to access some bad page. We'll have to
 251          * terminate things with extreme prejudice.
 252          */
 253         pr_alert("Unable to handle kernel paging request at virtual "
 254                  "address %08lx\n pc = %08lx, ra = %08lx\n",
 255                  address, regs->pc, regs->areg[0]);
 256         die("Oops", regs, sig);
 257         do_exit(sig);
 258 }