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 <asm/mmu_context.h>
  18 #include <asm/cacheflush.h>
  19 #include <asm/hardirq.h>
  20 #include <asm/uaccess.h>
  21 #include <asm/system.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
  48         info.si_code = SEGV_MAPERR;
  49
  50         /* We fault-in kernel-space virtual memory on-demand. The
  51          * 'reference' page table is init_mm.pgd.
  52          */
  53         if (address >= TASK_SIZE && !user_mode(regs))
  54                 goto vmalloc_fault;
  55
  56         /* If we're in an interrupt or have no user
  57          * context, we must not take the fault..
  58          */
  59         if (in_atomic() || !mm) {
  60                 bad_page_fault(regs, address, SIGSEGV);
  61                 return;
  62         }
  63
  64         is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
  65         is_exec =  (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
  66                     exccause == EXCCAUSE_ITLB_MISS ||
  67                     exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
  68
  69 #ifdef DEBUG_PAGE_FAULT
  70         printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid,
  71                address, exccause, regs->pc, is_write? "w":"", is_exec? "x":"");
  72 #endif
  73
  74         down_read(&mm->mmap_sem);
  75         vma = find_vma(mm, address);
  76
  77         if (!vma)
  78                 goto bad_area;
  79         if (vma->vm_start <= address)
  80                 goto good_area;
  81         if (!(vma->vm_flags & VM_GROWSDOWN))
  82                 goto bad_area;
  83         if (expand_stack(vma, address))
  84                 goto bad_area;
  85
  86         /* Ok, we have a good vm_area for this memory access, so
  87          * we can handle it..
  88          */
  89
  90 good_area:
  91         info.si_code = SEGV_ACCERR;
  92
  93         if (is_write) {
  94                 if (!(vma->vm_flags & VM_WRITE))
  95                         goto bad_area;
  96         } else if (is_exec) {
  97                 if (!(vma->vm_flags & VM_EXEC))
  98                         goto bad_area;
  99         } else  /* Allow read even from write-only pages. */
 100                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 101                         goto bad_area;
 102
 103         /* If for any reason at all we couldn't handle the fault,
 104          * make sure we exit gracefully rather than endlessly redo
 105          * the fault.
 106          */
 107 survive:
 108         fault = handle_mm_fault(mm, vma, address, is_write);
 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 (is_global_init(current)) {
 149                 yield();
 150                 down_read(&mm->mmap_sem);
 151                 goto survive;
 152         }
 153         printk("VM: killing process %s\n", current->comm);
 154         if (user_mode(regs))
 155                 do_group_exit(SIGKILL);
 156         bad_page_fault(regs, address, SIGKILL);
 157         return;
 158
 159 do_sigbus:
 160         up_read(&mm->mmap_sem);
 161
 162         /* Send a sigbus, regardless of whether we were in kernel
 163          * or user mode.
 164          */
 165         current->thread.bad_vaddr = address;
 166         info.si_code = SIGBUS;
 167         info.si_errno = 0;
 168         info.si_code = BUS_ADRERR;
 169         info.si_addr = (void *) address;
 170         force_sig_info(SIGBUS, &info, current);
 171
 172         /* Kernel mode? Handle exceptions or die */
 173         if (!user_mode(regs))
 174                 bad_page_fault(regs, address, SIGBUS);
 175
 176 vmalloc_fault:
 177         {
 178                 /* Synchronize this task's top level page-table
 179                  * with the 'reference' page table.
 180                  */
 181                 struct mm_struct *act_mm = current->active_mm;
 182                 int index = pgd_index(address);
 183                 pgd_t *pgd, *pgd_k;
 184                 pmd_t *pmd, *pmd_k;
 185                 pte_t *pte_k;
 186
 187                 if (act_mm == NULL)
 188                         goto bad_page_fault;
 189
 190                 pgd = act_mm->pgd + index;
 191                 pgd_k = init_mm.pgd + index;
 192
 193                 if (!pgd_present(*pgd_k))
 194                         goto bad_page_fault;
 195
 196                 pgd_val(*pgd) = pgd_val(*pgd_k);
 197
 198                 pmd = pmd_offset(pgd, address);
 199                 pmd_k = pmd_offset(pgd_k, address);
 200                 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 201                         goto bad_page_fault;
 202
 203                 pmd_val(*pmd) = pmd_val(*pmd_k);
 204                 pte_k = pte_offset_kernel(pmd_k, address);
 205
 206                 if (!pte_present(*pte_k))
 207                         goto bad_page_fault;
 208                 return;
 209         }
 210 bad_page_fault:
 211         bad_page_fault(regs, address, SIGKILL);
 212         return;
 213 }
 214
 215
 216 void
 217 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 218 {
 219         extern void die(const char*, struct pt_regs*, long);
 220         const struct exception_table_entry *entry;
 221
 222         /* Are we prepared to handle this kernel fault?  */
 223         if ((entry = search_exception_tables(regs->pc)) != NULL) {
 224 #ifdef DEBUG_PAGE_FAULT
 225                 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
 226                                 current->comm, regs->pc, entry->fixup);
 227 #endif
 228                 current->thread.bad_uaddr = address;
 229                 regs->pc = entry->fixup;
 230                 return;
 231         }
 232
 233         /* Oops. The kernel tried to access some bad page. We'll have to
 234          * terminate things with extreme prejudice.
 235          */
 236         printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
 237                "address %08lx\n pc = %08lx, ra = %08lx\n",
 238                address, regs->pc, regs->areg[0]);
 239         die("Oops", regs, sig);
 240         do_exit(sig);
 241 }
 242