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/traps.h>
  24
  25 void bad_page_fault(struct pt_regs*, unsigned long, int);
  26
  27 static void vmalloc_fault(struct pt_regs *regs, unsigned int address)
  28 {
  29 #ifdef CONFIG_MMU
  30         /* Synchronize this task's top level page-table
  31          * with the 'reference' page table.
  32          */
  33         struct mm_struct *act_mm = current->active_mm;
  34         int index = pgd_index(address);
  35         pgd_t *pgd, *pgd_k;
  36         p4d_t *p4d, *p4d_k;
  37         pud_t *pud, *pud_k;
  38         pmd_t *pmd, *pmd_k;
  39         pte_t *pte_k;
  40
  41         if (act_mm == NULL)
  42                 goto bad_page_fault;
  43
  44         pgd = act_mm->pgd + index;
  45         pgd_k = init_mm.pgd + index;
  46
  47         if (!pgd_present(*pgd_k))
  48                 goto bad_page_fault;
  49
  50         pgd_val(*pgd) = pgd_val(*pgd_k);
  51
  52         p4d = p4d_offset(pgd, address);
  53         p4d_k = p4d_offset(pgd_k, address);
  54         if (!p4d_present(*p4d) || !p4d_present(*p4d_k))
  55                 goto bad_page_fault;
  56
  57         pud = pud_offset(p4d, address);
  58         pud_k = pud_offset(p4d_k, address);
  59         if (!pud_present(*pud) || !pud_present(*pud_k))
  60                 goto bad_page_fault;
  61
  62         pmd = pmd_offset(pud, address);
  63         pmd_k = pmd_offset(pud_k, address);
  64         if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
  65                 goto bad_page_fault;
  66
  67         pmd_val(*pmd) = pmd_val(*pmd_k);
  68         pte_k = pte_offset_kernel(pmd_k, address);
  69
  70         if (!pte_present(*pte_k))
  71                 goto bad_page_fault;
  72         return;
  73
  74 bad_page_fault:
  75         bad_page_fault(regs, address, SIGKILL);
  76 #else
  77         WARN_ONCE(1, "%s in noMMU configuration\n", __func__);
  78 #endif
  79 }
  80 /*
  81  * This routine handles page faults.  It determines the address,
  82  * and the problem, and then passes it off to one of the appropriate
  83  * routines.
  84  *
  85  * Note: does not handle Miss and MultiHit.
  86  */
  87
  88 void do_page_fault(struct pt_regs *regs)
  89 {
  90         struct vm_area_struct * vma;
  91         struct mm_struct *mm = current->mm;
  92         unsigned int exccause = regs->exccause;
  93         unsigned int address = regs->excvaddr;
  94         int code;
  95
  96         int is_write, is_exec;
  97         vm_fault_t fault;
  98         unsigned int flags = FAULT_FLAG_DEFAULT;
  99
 100         code = SEGV_MAPERR;
 101
 102         /* We fault-in kernel-space virtual memory on-demand. The
 103          * 'reference' page table is init_mm.pgd.
 104          */
 105         if (address >= TASK_SIZE && !user_mode(regs)) {
 106                 vmalloc_fault(regs, address);
 107                 return;
 108         }
 109
 110         /* If we're in an interrupt or have no user
 111          * context, we must not take the fault..
 112          */
 113         if (faulthandler_disabled() || !mm) {
 114                 bad_page_fault(regs, address, SIGSEGV);
 115                 return;
 116         }
 117
 118         is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
 119         is_exec =  (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
 120                     exccause == EXCCAUSE_ITLB_MISS ||
 121                     exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
 122
 123         pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
 124                  current->comm, current->pid,
 125                  address, exccause, regs->pc,
 126                  is_write ? "w" : "", is_exec ? "x" : "");
 127
 128         if (user_mode(regs))
 129                 flags |= FAULT_FLAG_USER;
 130
 131         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 132
 133 retry:
 134         vma = lock_mm_and_find_vma(mm, address, regs);
 135         if (!vma)
 136                 goto bad_area_nosemaphore;
 137
 138         /* Ok, we have a good vm_area for this memory access, so
 139          * we can handle it..
 140          */
 141
 142         code = SEGV_ACCERR;
 143
 144         if (is_write) {
 145                 if (!(vma->vm_flags & VM_WRITE))
 146                         goto bad_area;
 147                 flags |= FAULT_FLAG_WRITE;
 148         } else if (is_exec) {
 149                 if (!(vma->vm_flags & VM_EXEC))
 150                         goto bad_area;
 151         } else  /* Allow read even from write-only pages. */
 152                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 153                         goto bad_area;
 154
 155         /* If for any reason at all we couldn't handle the fault,
 156          * make sure we exit gracefully rather than endlessly redo
 157          * the fault.
 158          */
 159         fault = handle_mm_fault(vma, address, flags, regs);
 160
 161         if (fault_signal_pending(fault, regs)) {
 162                 if (!user_mode(regs))
 163                         bad_page_fault(regs, address, SIGKILL);
 164                 return;
 165         }
 166
 167         /* The fault is fully completed (including releasing mmap lock) */
 168         if (fault & VM_FAULT_COMPLETED)
 169                 return;
 170
 171         if (unlikely(fault & VM_FAULT_ERROR)) {
 172                 if (fault & VM_FAULT_OOM)
 173                         goto out_of_memory;
 174                 else if (fault & VM_FAULT_SIGSEGV)
 175                         goto bad_area;
 176                 else if (fault & VM_FAULT_SIGBUS)
 177                         goto do_sigbus;
 178                 BUG();
 179         }
 180
 181         if (fault & VM_FAULT_RETRY) {
 182                 flags |= FAULT_FLAG_TRIED;
 183
 184                 /* No need to mmap_read_unlock(mm) as we would
 185                  * have already released it in __lock_page_or_retry
 186                  * in mm/filemap.c.
 187                  */
 188
 189                 goto retry;
 190         }
 191
 192         mmap_read_unlock(mm);
 193         return;
 194
 195         /* Something tried to access memory that isn't in our memory map..
 196          * Fix it, but check if it's kernel or user first..
 197          */
 198 bad_area:
 199         mmap_read_unlock(mm);
 200 bad_area_nosemaphore:
 201         if (user_mode(regs)) {
 202                 force_sig_fault(SIGSEGV, code, (void *) address);
 203                 return;
 204         }
 205         bad_page_fault(regs, address, SIGSEGV);
 206         return;
 207
 208
 209         /* We ran out of memory, or some other thing happened to us that made
 210          * us unable to handle the page fault gracefully.
 211          */
 212 out_of_memory:
 213         mmap_read_unlock(mm);
 214         if (!user_mode(regs))
 215                 bad_page_fault(regs, address, SIGKILL);
 216         else
 217                 pagefault_out_of_memory();
 218         return;
 219
 220 do_sigbus:
 221         mmap_read_unlock(mm);
 222
 223         /* Send a sigbus, regardless of whether we were in kernel
 224          * or user mode.
 225          */
 226         force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
 227
 228         /* Kernel mode? Handle exceptions or die */
 229         if (!user_mode(regs))
 230                 bad_page_fault(regs, address, SIGBUS);
 231         return;
 232 }
 233
 234
 235 void
 236 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 237 {
 238         extern void __noreturn die(const char*, struct pt_regs*, long);
 239         const struct exception_table_entry *entry;
 240
 241         /* Are we prepared to handle this kernel fault?  */
 242         if ((entry = search_exception_tables(regs->pc)) != NULL) {
 243                 pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
 244                          current->comm, regs->pc, entry->fixup);
 245                 regs->pc = entry->fixup;
 246                 return;
 247         }
 248
 249         /* Oops. The kernel tried to access some bad page. We'll have to
 250          * terminate things with extreme prejudice.
 251          */
 252         pr_alert("Unable to handle kernel paging request at virtual "
 253                  "address %08lx\n pc = %08lx, ra = %08lx\n",
 254                  address, regs->pc, regs->areg[0]);
 255         die("Oops", regs, sig);
 256 }