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/extable.h>
  17 #include <linux/hardirq.h>
  18 #include <linux/perf_event.h>
  19 #include <linux/uaccess.h>
  20 #include <asm/mmu_context.h>
  21 #include <asm/cacheflush.h>
  22 #include <asm/hardirq.h>
  23 #include <asm/pgalloc.h>
  24
  25 DEFINE_PER_CPU(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         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  49
  50         info.si_code = SEGV_MAPERR;
  51
  52         /* We fault-in kernel-space virtual memory on-demand. The
  53          * 'reference' page table is init_mm.pgd.
  54          */
  55         if (address >= TASK_SIZE && !user_mode(regs))
  56                 goto vmalloc_fault;
  57
  58         /* If we're in an interrupt or have no user
  59          * context, we must not take the fault..
  60          */
  61         if (faulthandler_disabled() || !mm) {
  62                 bad_page_fault(regs, address, SIGSEGV);
  63                 return;
  64         }
  65
  66         is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
  67         is_exec =  (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
  68                     exccause == EXCCAUSE_ITLB_MISS ||
  69                     exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
  70
  71 #ifdef DEBUG_PAGE_FAULT
  72         printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid,
  73                address, exccause, regs->pc, is_write? "w":"", is_exec? "x":"");
  74 #endif
  75
  76         if (user_mode(regs))
  77                 flags |= FAULT_FLAG_USER;
  78 retry:
  79         down_read(&mm->mmap_sem);
  80         vma = find_vma(mm, address);
  81
  82         if (!vma)
  83                 goto bad_area;
  84         if (vma->vm_start <= address)
  85                 goto good_area;
  86         if (!(vma->vm_flags & VM_GROWSDOWN))
  87                 goto bad_area;
  88         if (expand_stack(vma, address))
  89                 goto bad_area;
  90
  91         /* Ok, we have a good vm_area for this memory access, so
  92          * we can handle it..
  93          */
  94
  95 good_area:
  96         info.si_code = SEGV_ACCERR;
  97
  98         if (is_write) {
  99                 if (!(vma->vm_flags & VM_WRITE))
 100                         goto bad_area;
 101                 flags |= FAULT_FLAG_WRITE;
 102         } else if (is_exec) {
 103                 if (!(vma->vm_flags & VM_EXEC))
 104                         goto bad_area;
 105         } else  /* Allow read even from write-only pages. */
 106                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 107                         goto bad_area;
 108
 109         /* If for any reason at all we couldn't handle the fault,
 110          * make sure we exit gracefully rather than endlessly redo
 111          * the fault.
 112          */
 113         fault = handle_mm_fault(vma, address, flags);
 114
 115         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 116                 return;
 117
 118         if (unlikely(fault & VM_FAULT_ERROR)) {
 119                 if (fault & VM_FAULT_OOM)
 120                         goto out_of_memory;
 121                 else if (fault & VM_FAULT_SIGSEGV)
 122                         goto bad_area;
 123                 else if (fault & VM_FAULT_SIGBUS)
 124                         goto do_sigbus;
 125                 BUG();
 126         }
 127         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 128                 if (fault & VM_FAULT_MAJOR)
 129                         current->maj_flt++;
 130                 else
 131                         current->min_flt++;
 132                 if (fault & VM_FAULT_RETRY) {
 133                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 134                         flags |= FAULT_FLAG_TRIED;
 135
 136                          /* No need to up_read(&mm->mmap_sem) as we would
 137                          * have already released it in __lock_page_or_retry
 138                          * in mm/filemap.c.
 139                          */
 140
 141                         goto retry;
 142                 }
 143         }
 144
 145         up_read(&mm->mmap_sem);
 146         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 147         if (flags & VM_FAULT_MAJOR)
 148                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
 149         else
 150                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
 151
 152         return;
 153
 154         /* Something tried to access memory that isn't in our memory map..
 155          * Fix it, but check if it's kernel or user first..
 156          */
 157 bad_area:
 158         up_read(&mm->mmap_sem);
 159         if (user_mode(regs)) {
 160                 current->thread.bad_vaddr = address;
 161                 current->thread.error_code = is_write;
 162                 info.si_signo = SIGSEGV;
 163                 info.si_errno = 0;
 164                 /* info.si_code has been set above */
 165                 info.si_addr = (void *) address;
 166                 force_sig_info(SIGSEGV, &info, current);
 167                 return;
 168         }
 169         bad_page_fault(regs, address, SIGSEGV);
 170         return;
 171
 172
 173         /* We ran out of memory, or some other thing happened to us that made
 174          * us unable to handle the page fault gracefully.
 175          */
 176 out_of_memory:
 177         up_read(&mm->mmap_sem);
 178         if (!user_mode(regs))
 179                 bad_page_fault(regs, address, SIGKILL);
 180         else
 181                 pagefault_out_of_memory();
 182         return;
 183
 184 do_sigbus:
 185         up_read(&mm->mmap_sem);
 186
 187         /* Send a sigbus, regardless of whether we were in kernel
 188          * or user mode.
 189          */
 190         current->thread.bad_vaddr = address;
 191         info.si_code = SIGBUS;
 192         info.si_errno = 0;
 193         info.si_code = BUS_ADRERR;
 194         info.si_addr = (void *) address;
 195         force_sig_info(SIGBUS, &info, current);
 196
 197         /* Kernel mode? Handle exceptions or die */
 198         if (!user_mode(regs))
 199                 bad_page_fault(regs, address, SIGBUS);
 200         return;
 201
 202 vmalloc_fault:
 203         {
 204                 /* Synchronize this task's top level page-table
 205                  * with the 'reference' page table.
 206                  */
 207                 struct mm_struct *act_mm = current->active_mm;
 208                 int index = pgd_index(address);
 209                 pgd_t *pgd, *pgd_k;
 210                 pmd_t *pmd, *pmd_k;
 211                 pte_t *pte_k;
 212
 213                 if (act_mm == NULL)
 214                         goto bad_page_fault;
 215
 216                 pgd = act_mm->pgd + index;
 217                 pgd_k = init_mm.pgd + index;
 218
 219                 if (!pgd_present(*pgd_k))
 220                         goto bad_page_fault;
 221
 222                 pgd_val(*pgd) = pgd_val(*pgd_k);
 223
 224                 pmd = pmd_offset(pgd, address);
 225                 pmd_k = pmd_offset(pgd_k, address);
 226                 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 227                         goto bad_page_fault;
 228
 229                 pmd_val(*pmd) = pmd_val(*pmd_k);
 230                 pte_k = pte_offset_kernel(pmd_k, address);
 231
 232                 if (!pte_present(*pte_k))
 233                         goto bad_page_fault;
 234                 return;
 235         }
 236 bad_page_fault:
 237         bad_page_fault(regs, address, SIGKILL);
 238         return;
 239 }
 240
 241
 242 void
 243 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 244 {
 245         extern void die(const char*, struct pt_regs*, long);
 246         const struct exception_table_entry *entry;
 247
 248         /* Are we prepared to handle this kernel fault?  */
 249         if ((entry = search_exception_tables(regs->pc)) != NULL) {
 250 #ifdef DEBUG_PAGE_FAULT
 251                 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
 252                                 current->comm, regs->pc, entry->fixup);
 253 #endif
 254                 current->thread.bad_uaddr = address;
 255                 regs->pc = entry->fixup;
 256                 return;
 257         }
 258
 259         /* Oops. The kernel tried to access some bad page. We'll have to
 260          * terminate things with extreme prejudice.
 261          */
 262         printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
 263                "address %08lx\n pc = %08lx, ra = %08lx\n",
 264                address, regs->pc, regs->areg[0]);
 265         die("Oops", regs, sig);
 266         do_exit(sig);
 267 }