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/module.h>
  17 #include <linux/hardirq.h>
  18 #include <asm/mmu_context.h>
  19 #include <asm/cacheflush.h>
  20 #include <asm/hardirq.h>
  21 #include <asm/uaccess.h>
  22 #include <asm/pgalloc.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 #undef DEBUG_PAGE_FAULT
  28
  29 /*
  30  * This routine handles page faults.  It determines the address,
  31  * and the problem, and then passes it off to one of the appropriate
  32  * routines.
  33  *
  34  * Note: does not handle Miss and MultiHit.
  35  */
  36
  37 void do_page_fault(struct pt_regs *regs)
  38 {
  39         struct vm_area_struct * vma;
  40         struct mm_struct *mm = current->mm;
  41         unsigned int exccause = regs->exccause;
  42         unsigned int address = regs->excvaddr;
  43         siginfo_t info;
  44
  45         int is_write, is_exec;
  46         int fault;
  47         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  48
  49         info.si_code = SEGV_MAPERR;
  50
  51         /* We fault-in kernel-space virtual memory on-demand. The
  52          * 'reference' page table is init_mm.pgd.
  53          */
  54         if (address >= TASK_SIZE && !user_mode(regs))
  55                 goto vmalloc_fault;
  56
  57         /* If we're in an interrupt or have no user
  58          * context, we must not take the fault..
  59          */
  60         if (in_atomic() || !mm) {
  61                 bad_page_fault(regs, address, SIGSEGV);
  62                 return;
  63         }
  64
  65         is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
  66         is_exec =  (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
  67                     exccause == EXCCAUSE_ITLB_MISS ||
  68                     exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
  69
  70 #ifdef DEBUG_PAGE_FAULT
  71         printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid,
  72                address, exccause, regs->pc, is_write? "w":"", is_exec? "x":"");
  73 #endif
  74
  75         if (user_mode(regs))
  76                 flags |= FAULT_FLAG_USER;
  77 retry:
  78         down_read(&mm->mmap_sem);
  79         vma = find_vma(mm, address);
  80
  81         if (!vma)
  82                 goto bad_area;
  83         if (vma->vm_start <= address)
  84                 goto good_area;
  85         if (!(vma->vm_flags & VM_GROWSDOWN))
  86                 goto bad_area;
  87         if (expand_stack(vma, address))
  88                 goto bad_area;
  89
  90         /* Ok, we have a good vm_area for this memory access, so
  91          * we can handle it..
  92          */
  93
  94 good_area:
  95         info.si_code = SEGV_ACCERR;
  96
  97         if (is_write) {
  98                 if (!(vma->vm_flags & VM_WRITE))
  99                         goto bad_area;
 100                 flags |= FAULT_FLAG_WRITE;
 101         } else if (is_exec) {
 102                 if (!(vma->vm_flags & VM_EXEC))
 103                         goto bad_area;
 104         } else  /* Allow read even from write-only pages. */
 105                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 106                         goto bad_area;
 107
 108         /* If for any reason at all we couldn't handle the fault,
 109          * make sure we exit gracefully rather than endlessly redo
 110          * the fault.
 111          */
 112         fault = handle_mm_fault(mm, vma, address, flags);
 113
 114         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 115                 return;
 116
 117         if (unlikely(fault & VM_FAULT_ERROR)) {
 118                 if (fault & VM_FAULT_OOM)
 119                         goto out_of_memory;
 120                 else if (fault & VM_FAULT_SIGSEGV)
 121                         goto bad_area;
 122                 else if (fault & VM_FAULT_SIGBUS)
 123                         goto do_sigbus;
 124                 BUG();
 125         }
 126         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 127                 if (fault & VM_FAULT_MAJOR)
 128                         current->maj_flt++;
 129                 else
 130                         current->min_flt++;
 131                 if (fault & VM_FAULT_RETRY) {
 132                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 133                         flags |= FAULT_FLAG_TRIED;
 134
 135                          /* No need to up_read(&mm->mmap_sem) as we would
 136                          * have already released it in __lock_page_or_retry
 137                          * in mm/filemap.c.
 138                          */
 139
 140                         goto retry;
 141                 }
 142         }
 143
 144         up_read(&mm->mmap_sem);
 145         return;
 146
 147         /* Something tried to access memory that isn't in our memory map..
 148          * Fix it, but check if it's kernel or user first..
 149          */
 150 bad_area:
 151         up_read(&mm->mmap_sem);
 152         if (user_mode(regs)) {
 153                 current->thread.bad_vaddr = address;
 154                 current->thread.error_code = is_write;
 155                 info.si_signo = SIGSEGV;
 156                 info.si_errno = 0;
 157                 /* info.si_code has been set above */
 158                 info.si_addr = (void *) address;
 159                 force_sig_info(SIGSEGV, &info, current);
 160                 return;
 161         }
 162         bad_page_fault(regs, address, SIGSEGV);
 163         return;
 164
 165
 166         /* We ran out of memory, or some other thing happened to us that made
 167          * us unable to handle the page fault gracefully.
 168          */
 169 out_of_memory:
 170         up_read(&mm->mmap_sem);
 171         if (!user_mode(regs))
 172                 bad_page_fault(regs, address, SIGKILL);
 173         else
 174                 pagefault_out_of_memory();
 175         return;
 176
 177 do_sigbus:
 178         up_read(&mm->mmap_sem);
 179
 180         /* Send a sigbus, regardless of whether we were in kernel
 181          * or user mode.
 182          */
 183         current->thread.bad_vaddr = address;
 184         info.si_code = SIGBUS;
 185         info.si_errno = 0;
 186         info.si_code = BUS_ADRERR;
 187         info.si_addr = (void *) address;
 188         force_sig_info(SIGBUS, &info, current);
 189
 190         /* Kernel mode? Handle exceptions or die */
 191         if (!user_mode(regs))
 192                 bad_page_fault(regs, address, SIGBUS);
 193         return;
 194
 195 vmalloc_fault:
 196         {
 197                 /* Synchronize this task's top level page-table
 198                  * with the 'reference' page table.
 199                  */
 200                 struct mm_struct *act_mm = current->active_mm;
 201                 int index = pgd_index(address);
 202                 pgd_t *pgd, *pgd_k;
 203                 pmd_t *pmd, *pmd_k;
 204                 pte_t *pte_k;
 205
 206                 if (act_mm == NULL)
 207                         goto bad_page_fault;
 208
 209                 pgd = act_mm->pgd + index;
 210                 pgd_k = init_mm.pgd + index;
 211
 212                 if (!pgd_present(*pgd_k))
 213                         goto bad_page_fault;
 214
 215                 pgd_val(*pgd) = pgd_val(*pgd_k);
 216
 217                 pmd = pmd_offset(pgd, address);
 218                 pmd_k = pmd_offset(pgd_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 #ifdef DEBUG_PAGE_FAULT
 244                 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
 245                                 current->comm, regs->pc, entry->fixup);
 246 #endif
 247                 current->thread.bad_uaddr = address;
 248                 regs->pc = entry->fixup;
 249                 return;
 250         }
 251
 252         /* Oops. The kernel tried to access some bad page. We'll have to
 253          * terminate things with extreme prejudice.
 254          */
 255         printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
 256                "address %08lx\n pc = %08lx, ra = %08lx\n",
 257                address, regs->pc, regs->areg[0]);
 258         die("Oops", regs, sig);
 259         do_exit(sig);
 260 }