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_FIRST_VERSION;
  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         siginfo_t info;
  42
  43         int is_write, is_exec;
  44
  45         info.si_code = SEGV_MAPERR;
  46
  47         /* We fault-in kernel-space virtual memory on-demand. The
  48          * 'reference' page table is init_mm.pgd.
  49          */
  50         if (address >= TASK_SIZE && !user_mode(regs))
  51                 goto vmalloc_fault;
  52
  53         /* If we're in an interrupt or have no user
  54          * context, we must not take the fault..
  55          */
  56         if (in_atomic() || !mm) {
  57                 bad_page_fault(regs, address, SIGSEGV);
  58                 return;
  59         }
  60
  61         is_write = (exccause == XCHAL_EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
  62         is_exec =  (exccause == XCHAL_EXCCAUSE_ITLB_PRIVILEGE ||
  63                     exccause == XCHAL_EXCCAUSE_ITLB_MISS ||
  64                     exccause == XCHAL_EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
  65
  66 #if 0
  67         printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid,
  68                address, exccause, regs->pc, is_write? "w":"", is_exec? "x":"");
  69 #endif
  70
  71         down_read(&mm->mmap_sem);
  72         vma = find_vma(mm, address);
  73
  74         if (!vma)
  75                 goto bad_area;
  76         if (vma->vm_start <= address)
  77                 goto good_area;
  78         if (!(vma->vm_flags & VM_GROWSDOWN))
  79                 goto bad_area;
  80         if (expand_stack(vma, address))
  81                 goto bad_area;
  82
  83         /* Ok, we have a good vm_area for this memory access, so
  84          * we can handle it..
  85          */
  86
  87 good_area:
  88         info.si_code = SEGV_ACCERR;
  89
  90         if (is_write) {
  91                 if (!(vma->vm_flags & VM_WRITE))
  92                         goto bad_area;
  93         } else if (is_exec) {
  94                 if (!(vma->vm_flags & VM_EXEC))
  95                         goto bad_area;
  96         } else  /* Allow read even from write-only pages. */
  97                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
  98                         goto bad_area;
  99
 100         /* If for any reason at all we couldn't handle the fault,
 101          * make sure we exit gracefully rather than endlessly redo
 102          * the fault.
 103          */
 104 survive:
 105         switch (handle_mm_fault(mm, vma, address, is_write)) {
 106         case VM_FAULT_MINOR:
 107                 current->min_flt++;
 108                 break;
 109         case VM_FAULT_MAJOR:
 110                 current->maj_flt++;
 111                 break;
 112         case VM_FAULT_SIGBUS:
 113                 goto do_sigbus;
 114         case VM_FAULT_OOM:
 115                 goto out_of_memory;
 116         default:
 117                 BUG();
 118         }
 119
 120         up_read(&mm->mmap_sem);
 121         return;
 122
 123         /* Something tried to access memory that isn't in our memory map..
 124          * Fix it, but check if it's kernel or user first..
 125          */
 126 bad_area:
 127         up_read(&mm->mmap_sem);
 128         if (user_mode(regs)) {
 129                 current->thread.bad_vaddr = address;
 130                 current->thread.error_code = is_write;
 131                 info.si_signo = SIGSEGV;
 132                 info.si_errno = 0;
 133                 /* info.si_code has been set above */
 134                 info.si_addr = (void *) address;
 135                 force_sig_info(SIGSEGV, &info, current);
 136                 return;
 137         }
 138         bad_page_fault(regs, address, SIGSEGV);
 139         return;
 140
 141
 142         /* We ran out of memory, or some other thing happened to us that made
 143          * us unable to handle the page fault gracefully.
 144          */
 145 out_of_memory:
 146         up_read(&mm->mmap_sem);
 147         if (current->pid == 1) {
 148                 yield();
 149                 down_read(&mm->mmap_sem);
 150                 goto survive;
 151         }
 152         printk("VM: killing process %s\n", current->comm);
 153         if (user_mode(regs))
 154                 do_exit(SIGKILL);
 155         bad_page_fault(regs, address, SIGKILL);
 156         return;
 157
 158 do_sigbus:
 159         up_read(&mm->mmap_sem);
 160
 161         /* Send a sigbus, regardless of whether we were in kernel
 162          * or user mode.
 163          */
 164         current->thread.bad_vaddr = address;
 165         info.si_code = SIGBUS;
 166         info.si_errno = 0;
 167         info.si_code = BUS_ADRERR;
 168         info.si_addr = (void *) address;
 169         force_sig_info(SIGBUS, &info, current);
 170
 171         /* Kernel mode? Handle exceptions or die */
 172         if (!user_mode(regs))
 173                 bad_page_fault(regs, address, SIGBUS);
 174
 175 vmalloc_fault:
 176         {
 177                 /* Synchronize this task's top level page-table
 178                  * with the 'reference' page table.
 179                  */
 180                 struct mm_struct *act_mm = current->active_mm;
 181                 int index = pgd_index(address);
 182                 pgd_t *pgd, *pgd_k;
 183                 pmd_t *pmd, *pmd_k;
 184                 pte_t *pte_k;
 185
 186                 if (act_mm == NULL)
 187                         goto bad_page_fault;
 188
 189                 pgd = act_mm->pgd + index;
 190                 pgd_k = init_mm.pgd + index;
 191
 192                 if (!pgd_present(*pgd_k))
 193                         goto bad_page_fault;
 194
 195                 pgd_val(*pgd) = pgd_val(*pgd_k);
 196
 197                 pmd = pmd_offset(pgd, address);
 198                 pmd_k = pmd_offset(pgd_k, address);
 199                 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 200                         goto bad_page_fault;
 201
 202                 pmd_val(*pmd) = pmd_val(*pmd_k);
 203                 pte_k = pte_offset_kernel(pmd_k, address);
 204
 205                 if (!pte_present(*pte_k))
 206                         goto bad_page_fault;
 207                 return;
 208         }
 209 bad_page_fault:
 210         bad_page_fault(regs, address, SIGKILL);
 211         return;
 212 }
 213
 214
 215 void
 216 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 217 {
 218         extern void die(const char*, struct pt_regs*, long);
 219         const struct exception_table_entry *entry;
 220
 221         /* Are we prepared to handle this kernel fault?  */
 222         if ((entry = search_exception_tables(regs->pc)) != NULL) {
 223 #if 1
 224                 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
 225                                 current->comm, regs->pc, entry->fixup);
 226 #endif
 227                 current->thread.bad_uaddr = address;
 228                 regs->pc = entry->fixup;
 229                 return;
 230         }
 231
 232         /* Oops. The kernel tried to access some bad page. We'll have to
 233          * terminate things with extreme prejudice.
 234          */
 235         printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
 236                "address %08lx\n pc = %08lx, ra = %08lx\n",
 237                address, regs->pc, regs->areg[0]);
 238         die("Oops", regs, sig);
 239         do_exit(sig);
 240 }
 241