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 - 2005 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/system.h>
  23 #include <asm/pgalloc.h>
  24
  25 unsigned long asid_cache = ASID_USER_FIRST;
  26 void bad_page_fault(struct pt_regs*, unsigned long, int);
  27
  28 #undef DEBUG_PAGE_FAULT
  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  * Note: does not handle Miss and MultiHit.
  36  */
  37
  38 void do_page_fault(struct pt_regs *regs)
  39 {
  40         struct vm_area_struct * vma;
  41         struct mm_struct *mm = current->mm;
  42         unsigned int exccause = regs->exccause;
  43         unsigned int address = regs->excvaddr;
  44         siginfo_t info;
  45
  46         int is_write, is_exec;
  47         int fault;
  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         down_read(&mm->mmap_sem);
  76         vma = find_vma(mm, address);
  77
  78         if (!vma)
  79                 goto bad_area;
  80         if (vma->vm_start <= address)
  81                 goto good_area;
  82         if (!(vma->vm_flags & VM_GROWSDOWN))
  83                 goto bad_area;
  84         if (expand_stack(vma, address))
  85                 goto bad_area;
  86
  87         /* Ok, we have a good vm_area for this memory access, so
  88          * we can handle it..
  89          */
  90
  91 good_area:
  92         info.si_code = SEGV_ACCERR;
  93
  94         if (is_write) {
  95                 if (!(vma->vm_flags & VM_WRITE))
  96                         goto bad_area;
  97         } else if (is_exec) {
  98                 if (!(vma->vm_flags & VM_EXEC))
  99                         goto bad_area;
 100         } else  /* Allow read even from write-only pages. */
 101                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 102                         goto bad_area;
 103
 104         /* If for any reason at all we couldn't handle the fault,
 105          * make sure we exit gracefully rather than endlessly redo
 106          * the fault.
 107          */
 108         fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
 109         if (unlikely(fault & VM_FAULT_ERROR)) {
 110                 if (fault & VM_FAULT_OOM)
 111                         goto out_of_memory;
 112                 else if (fault & VM_FAULT_SIGBUS)
 113                         goto do_sigbus;
 114                 BUG();
 115         }
 116         if (fault & VM_FAULT_MAJOR)
 117                 current->maj_flt++;
 118         else
 119                 current->min_flt++;
 120
 121         up_read(&mm->mmap_sem);
 122         return;
 123
 124         /* Something tried to access memory that isn't in our memory map..
 125          * Fix it, but check if it's kernel or user first..
 126          */
 127 bad_area:
 128         up_read(&mm->mmap_sem);
 129         if (user_mode(regs)) {
 130                 current->thread.bad_vaddr = address;
 131                 current->thread.error_code = is_write;
 132                 info.si_signo = SIGSEGV;
 133                 info.si_errno = 0;
 134                 /* info.si_code has been set above */
 135                 info.si_addr = (void *) address;
 136                 force_sig_info(SIGSEGV, &info, current);
 137                 return;
 138         }
 139         bad_page_fault(regs, address, SIGSEGV);
 140         return;
 141
 142
 143         /* We ran out of memory, or some other thing happened to us that made
 144          * us unable to handle the page fault gracefully.
 145          */
 146 out_of_memory:
 147         up_read(&mm->mmap_sem);
 148         if (!user_mode(regs))
 149                 bad_page_fault(regs, address, SIGKILL);
 150         else
 151                 pagefault_out_of_memory();
 152         return;
 153
 154 do_sigbus:
 155         up_read(&mm->mmap_sem);
 156
 157         /* Send a sigbus, regardless of whether we were in kernel
 158          * or user mode.
 159          */
 160         current->thread.bad_vaddr = address;
 161         info.si_code = SIGBUS;
 162         info.si_errno = 0;
 163         info.si_code = BUS_ADRERR;
 164         info.si_addr = (void *) address;
 165         force_sig_info(SIGBUS, &info, current);
 166
 167         /* Kernel mode? Handle exceptions or die */
 168         if (!user_mode(regs))
 169                 bad_page_fault(regs, address, SIGBUS);
 170
 171 vmalloc_fault:
 172         {
 173                 /* Synchronize this task's top level page-table
 174                  * with the 'reference' page table.
 175                  */
 176                 struct mm_struct *act_mm = current->active_mm;
 177                 int index = pgd_index(address);
 178                 pgd_t *pgd, *pgd_k;
 179                 pmd_t *pmd, *pmd_k;
 180                 pte_t *pte_k;
 181
 182                 if (act_mm == NULL)
 183                         goto bad_page_fault;
 184
 185                 pgd = act_mm->pgd + index;
 186                 pgd_k = init_mm.pgd + index;
 187
 188                 if (!pgd_present(*pgd_k))
 189                         goto bad_page_fault;
 190
 191                 pgd_val(*pgd) = pgd_val(*pgd_k);
 192
 193                 pmd = pmd_offset(pgd, address);
 194                 pmd_k = pmd_offset(pgd_k, address);
 195                 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 196                         goto bad_page_fault;
 197
 198                 pmd_val(*pmd) = pmd_val(*pmd_k);
 199                 pte_k = pte_offset_kernel(pmd_k, address);
 200
 201                 if (!pte_present(*pte_k))
 202                         goto bad_page_fault;
 203                 return;
 204         }
 205 bad_page_fault:
 206         bad_page_fault(regs, address, SIGKILL);
 207         return;
 208 }
 209
 210
 211 void
 212 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 213 {
 214         extern void die(const char*, struct pt_regs*, long);
 215         const struct exception_table_entry *entry;
 216
 217         /* Are we prepared to handle this kernel fault?  */
 218         if ((entry = search_exception_tables(regs->pc)) != NULL) {
 219 #ifdef DEBUG_PAGE_FAULT
 220                 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
 221                                 current->comm, regs->pc, entry->fixup);
 222 #endif
 223                 current->thread.bad_uaddr = address;
 224                 regs->pc = entry->fixup;
 225                 return;
 226         }
 227
 228         /* Oops. The kernel tried to access some bad page. We'll have to
 229          * terminate things with extreme prejudice.
 230          */
 231         printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
 232                "address %08lx\n pc = %08lx, ra = %08lx\n",
 233                address, regs->pc, regs->areg[0]);
 234         die("Oops", regs, sig);
 235         do_exit(sig);
 236 }
 237