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 survive:
 109         fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
 110         if (unlikely(fault & VM_FAULT_ERROR)) {
 111                 if (fault & VM_FAULT_OOM)
 112                         goto out_of_memory;
 113                 else if (fault & VM_FAULT_SIGBUS)
 114                         goto do_sigbus;
 115                 BUG();
 116         }
 117         if (fault & VM_FAULT_MAJOR)
 118                 current->maj_flt++;
 119         else
 120                 current->min_flt++;
 121
 122         up_read(&mm->mmap_sem);
 123         return;
 124
 125         /* Something tried to access memory that isn't in our memory map..
 126          * Fix it, but check if it's kernel or user first..
 127          */
 128 bad_area:
 129         up_read(&mm->mmap_sem);
 130         if (user_mode(regs)) {
 131                 current->thread.bad_vaddr = address;
 132                 current->thread.error_code = is_write;
 133                 info.si_signo = SIGSEGV;
 134                 info.si_errno = 0;
 135                 /* info.si_code has been set above */
 136                 info.si_addr = (void *) address;
 137                 force_sig_info(SIGSEGV, &info, current);
 138                 return;
 139         }
 140         bad_page_fault(regs, address, SIGSEGV);
 141         return;
 142
 143
 144         /* We ran out of memory, or some other thing happened to us that made
 145          * us unable to handle the page fault gracefully.
 146          */
 147 out_of_memory:
 148         up_read(&mm->mmap_sem);
 149         if (is_global_init(current)) {
 150                 yield();
 151                 down_read(&mm->mmap_sem);
 152                 goto survive;
 153         }
 154         printk("VM: killing process %s\n", current->comm);
 155         if (user_mode(regs))
 156                 do_group_exit(SIGKILL);
 157         bad_page_fault(regs, address, SIGKILL);
 158         return;
 159
 160 do_sigbus:
 161         up_read(&mm->mmap_sem);
 162
 163         /* Send a sigbus, regardless of whether we were in kernel
 164          * or user mode.
 165          */
 166         current->thread.bad_vaddr = address;
 167         info.si_code = SIGBUS;
 168         info.si_errno = 0;
 169         info.si_code = BUS_ADRERR;
 170         info.si_addr = (void *) address;
 171         force_sig_info(SIGBUS, &info, current);
 172
 173         /* Kernel mode? Handle exceptions or die */
 174         if (!user_mode(regs))
 175                 bad_page_fault(regs, address, SIGBUS);
 176
 177 vmalloc_fault:
 178         {
 179                 /* Synchronize this task's top level page-table
 180                  * with the 'reference' page table.
 181                  */
 182                 struct mm_struct *act_mm = current->active_mm;
 183                 int index = pgd_index(address);
 184                 pgd_t *pgd, *pgd_k;
 185                 pmd_t *pmd, *pmd_k;
 186                 pte_t *pte_k;
 187
 188                 if (act_mm == NULL)
 189                         goto bad_page_fault;
 190
 191                 pgd = act_mm->pgd + index;
 192                 pgd_k = init_mm.pgd + index;
 193
 194                 if (!pgd_present(*pgd_k))
 195                         goto bad_page_fault;
 196
 197                 pgd_val(*pgd) = pgd_val(*pgd_k);
 198
 199                 pmd = pmd_offset(pgd, address);
 200                 pmd_k = pmd_offset(pgd_k, address);
 201                 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 202                         goto bad_page_fault;
 203
 204                 pmd_val(*pmd) = pmd_val(*pmd_k);
 205                 pte_k = pte_offset_kernel(pmd_k, address);
 206
 207                 if (!pte_present(*pte_k))
 208                         goto bad_page_fault;
 209                 return;
 210         }
 211 bad_page_fault:
 212         bad_page_fault(regs, address, SIGKILL);
 213         return;
 214 }
 215
 216
 217 void
 218 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 219 {
 220         extern void die(const char*, struct pt_regs*, long);
 221         const struct exception_table_entry *entry;
 222
 223         /* Are we prepared to handle this kernel fault?  */
 224         if ((entry = search_exception_tables(regs->pc)) != NULL) {
 225 #ifdef DEBUG_PAGE_FAULT
 226                 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
 227                                 current->comm, regs->pc, entry->fixup);
 228 #endif
 229                 current->thread.bad_uaddr = address;
 230                 regs->pc = entry->fixup;
 231                 return;
 232         }
 233
 234         /* Oops. The kernel tried to access some bad page. We'll have to
 235          * terminate things with extreme prejudice.
 236          */
 237         printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
 238                "address %08lx\n pc = %08lx, ra = %08lx\n",
 239                address, regs->pc, regs->areg[0]);
 240         die("Oops", regs, sig);
 241         do_exit(sig);
 242 }
 243