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 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 retry:
  76         down_read(&mm->mmap_sem);
  77         vma = find_vma(mm, address);
  78
  79         if (!vma)
  80                 goto bad_area;
  81         if (vma->vm_start <= address)
  82                 goto good_area;
  83         if (!(vma->vm_flags & VM_GROWSDOWN))
  84                 goto bad_area;
  85         if (expand_stack(vma, address))
  86                 goto bad_area;
  87
  88         /* Ok, we have a good vm_area for this memory access, so
  89          * we can handle it..
  90          */
  91
  92 good_area:
  93         info.si_code = SEGV_ACCERR;
  94
  95         if (is_write) {
  96                 if (!(vma->vm_flags & VM_WRITE))
  97                         goto bad_area;
  98                 flags |= FAULT_FLAG_WRITE;
  99         } else if (is_exec) {
 100                 if (!(vma->vm_flags & VM_EXEC))
 101                         goto bad_area;
 102         } else  /* Allow read even from write-only pages. */
 103                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 104                         goto bad_area;
 105
 106         /* If for any reason at all we couldn't handle the fault,
 107          * make sure we exit gracefully rather than endlessly redo
 108          * the fault.
 109          */
 110         fault = handle_mm_fault(mm, vma, address, flags);
 111
 112         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 113                 return;
 114
 115         if (unlikely(fault & VM_FAULT_ERROR)) {
 116                 if (fault & VM_FAULT_OOM)
 117                         goto out_of_memory;
 118                 else if (fault & VM_FAULT_SIGBUS)
 119                         goto do_sigbus;
 120                 BUG();
 121         }
 122         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 123                 if (fault & VM_FAULT_MAJOR)
 124                         current->maj_flt++;
 125                 else
 126                         current->min_flt++;
 127                 if (fault & VM_FAULT_RETRY) {
 128                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 129                         flags |= FAULT_FLAG_TRIED;
 130
 131                          /* No need to up_read(&mm->mmap_sem) 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         up_read(&mm->mmap_sem);
 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         up_read(&mm->mmap_sem);
 148         if (user_mode(regs)) {
 149                 current->thread.bad_vaddr = address;
 150                 current->thread.error_code = is_write;
 151                 info.si_signo = SIGSEGV;
 152                 info.si_errno = 0;
 153                 /* info.si_code has been set above */
 154                 info.si_addr = (void *) address;
 155                 force_sig_info(SIGSEGV, &info, current);
 156                 return;
 157         }
 158         bad_page_fault(regs, address, SIGSEGV);
 159         return;
 160
 161
 162         /* We ran out of memory, or some other thing happened to us that made
 163          * us unable to handle the page fault gracefully.
 164          */
 165 out_of_memory:
 166         up_read(&mm->mmap_sem);
 167         if (!user_mode(regs))
 168                 bad_page_fault(regs, address, SIGKILL);
 169         else
 170                 pagefault_out_of_memory();
 171         return;
 172
 173 do_sigbus:
 174         up_read(&mm->mmap_sem);
 175
 176         /* Send a sigbus, regardless of whether we were in kernel
 177          * or user mode.
 178          */
 179         current->thread.bad_vaddr = address;
 180         info.si_code = SIGBUS;
 181         info.si_errno = 0;
 182         info.si_code = BUS_ADRERR;
 183         info.si_addr = (void *) address;
 184         force_sig_info(SIGBUS, &info, current);
 185
 186         /* Kernel mode? Handle exceptions or die */
 187         if (!user_mode(regs))
 188                 bad_page_fault(regs, address, SIGBUS);
 189         return;
 190
 191 vmalloc_fault:
 192         {
 193                 /* Synchronize this task's top level page-table
 194                  * with the 'reference' page table.
 195                  */
 196                 struct mm_struct *act_mm = current->active_mm;
 197                 int index = pgd_index(address);
 198                 pgd_t *pgd, *pgd_k;
 199                 pmd_t *pmd, *pmd_k;
 200                 pte_t *pte_k;
 201
 202                 if (act_mm == NULL)
 203                         goto bad_page_fault;
 204
 205                 pgd = act_mm->pgd + index;
 206                 pgd_k = init_mm.pgd + index;
 207
 208                 if (!pgd_present(*pgd_k))
 209                         goto bad_page_fault;
 210
 211                 pgd_val(*pgd) = pgd_val(*pgd_k);
 212
 213                 pmd = pmd_offset(pgd, address);
 214                 pmd_k = pmd_offset(pgd_k, address);
 215                 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 216                         goto bad_page_fault;
 217
 218                 pmd_val(*pmd) = pmd_val(*pmd_k);
 219                 pte_k = pte_offset_kernel(pmd_k, address);
 220
 221                 if (!pte_present(*pte_k))
 222                         goto bad_page_fault;
 223                 return;
 224         }
 225 bad_page_fault:
 226         bad_page_fault(regs, address, SIGKILL);
 227         return;
 228 }
 229
 230
 231 void
 232 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 233 {
 234         extern void die(const char*, struct pt_regs*, long);
 235         const struct exception_table_entry *entry;
 236
 237         /* Are we prepared to handle this kernel fault?  */
 238         if ((entry = search_exception_tables(regs->pc)) != NULL) {
 239 #ifdef DEBUG_PAGE_FAULT
 240                 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
 241                                 current->comm, regs->pc, entry->fixup);
 242 #endif
 243                 current->thread.bad_uaddr = address;
 244                 regs->pc = entry->fixup;
 245                 return;
 246         }
 247
 248         /* Oops. The kernel tried to access some bad page. We'll have to
 249          * terminate things with extreme prejudice.
 250          */
 251         printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
 252                "address %08lx\n pc = %08lx, ra = %08lx\n",
 253                address, regs->pc, regs->areg[0]);
 254         die("Oops", regs, sig);
 255         do_exit(sig);
 256 }