LXR linux/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
  24DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
  25void 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
  35void 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        int code;
  42
  43        int is_write, is_exec;
  44        vm_fault_t fault;
  45        unsigned int flags = FAULT_FLAG_DEFAULT;
  46
  47        code = SEGV_MAPERR;
  48
  49        /* We fault-in kernel-space virtual memory on-demand. The
  50         * 'reference' page table is init_mm.pgd.
  51         */
  52        if (address >= TASK_SIZE && !user_mode(regs))
  53                goto vmalloc_fault;
  54
  55        /* If we're in an interrupt or have no user
  56         * context, we must not take the fault..
  57         */
  58        if (faulthandler_disabled() || !mm) {
  59                bad_page_fault(regs, address, SIGSEGV);
  60                return;
  61        }
  62
  63        is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
  64        is_exec =  (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
  65                    exccause == EXCCAUSE_ITLB_MISS ||
  66                    exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
  67
  68        pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
  69                 current->comm, current->pid,
  70                 address, exccause, regs->pc,
  71                 is_write ? "w" : "", is_exec ? "x" : "");
  72
  73        if (user_mode(regs))
  74                flags |= FAULT_FLAG_USER;
  75
  76        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
  77
  78retry:
  79        mmap_read_lock(mm);
  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
  95good_area:
  96        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, regs);
 114
 115        if (fault_signal_pending(fault, regs)) {
 116                if (!user_mode(regs))
 117                        goto bad_page_fault;
 118                return;
 119        }
 120
 121        if (unlikely(fault & VM_FAULT_ERROR)) {
 122                if (fault & VM_FAULT_OOM)
 123                        goto out_of_memory;
 124                else if (fault & VM_FAULT_SIGSEGV)
 125                        goto bad_area;
 126                else if (fault & VM_FAULT_SIGBUS)
 127                        goto do_sigbus;
 128                BUG();
 129        }
 130        if (flags & FAULT_FLAG_ALLOW_RETRY) {
 131                if (fault & VM_FAULT_RETRY) {
 132                        flags |= FAULT_FLAG_TRIED;
 133
 134                         /* No need to mmap_read_unlock(mm) as we would
 135                         * have already released it in __lock_page_or_retry
 136                         * in mm/filemap.c.
 137                         */
 138
 139                        goto retry;
 140                }
 141        }
 142
 143        mmap_read_unlock(mm);
 144        return;
 145
 146        /* Something tried to access memory that isn't in our memory map..
 147         * Fix it, but check if it's kernel or user first..
 148         */
 149bad_area:
 150        mmap_read_unlock(mm);
 151        if (user_mode(regs)) {
 152                current->thread.bad_vaddr = address;
 153                current->thread.error_code = is_write;
 154                force_sig_fault(SIGSEGV, code, (void *) address);
 155                return;
 156        }
 157        bad_page_fault(regs, address, SIGSEGV);
 158        return;
 159
 160
 161        /* We ran out of memory, or some other thing happened to us that made
 162         * us unable to handle the page fault gracefully.
 163         */
 164out_of_memory:
 165        mmap_read_unlock(mm);
 166        if (!user_mode(regs))
 167                bad_page_fault(regs, address, SIGKILL);
 168        else
 169                pagefault_out_of_memory();
 170        return;
 171
 172do_sigbus:
 173        mmap_read_unlock(mm);
 174
 175        /* Send a sigbus, regardless of whether we were in kernel
 176         * or user mode.
 177         */
 178        current->thread.bad_vaddr = address;
 179        force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
 180
 181        /* Kernel mode? Handle exceptions or die */
 182        if (!user_mode(regs))
 183                bad_page_fault(regs, address, SIGBUS);
 184        return;
 185
 186vmalloc_fault:
 187        {
 188                /* Synchronize this task's top level page-table
 189                 * with the 'reference' page table.
 190                 */
 191                struct mm_struct *act_mm = current->active_mm;
 192                int index = pgd_index(address);
 193                pgd_t *pgd, *pgd_k;
 194                p4d_t *p4d, *p4d_k;
 195                pud_t *pud, *pud_k;
 196                pmd_t *pmd, *pmd_k;
 197                pte_t *pte_k;
 198
 199                if (act_mm == NULL)
 200                        goto bad_page_fault;
 201
 202                pgd = act_mm->pgd + index;
 203                pgd_k = init_mm.pgd + index;
 204
 205                if (!pgd_present(*pgd_k))
 206                        goto bad_page_fault;
 207
 208                pgd_val(*pgd) = pgd_val(*pgd_k);
 209
 210                p4d = p4d_offset(pgd, address);
 211                p4d_k = p4d_offset(pgd_k, address);
 212                if (!p4d_present(*p4d) || !p4d_present(*p4d_k))
 213                        goto bad_page_fault;
 214
 215                pud = pud_offset(p4d, address);
 216                pud_k = pud_offset(p4d_k, address);
 217                if (!pud_present(*pud) || !pud_present(*pud_k))
 218                        goto bad_page_fault;
 219
 220                pmd = pmd_offset(pud, address);
 221                pmd_k = pmd_offset(pud_k, address);
 222                if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
 223                        goto bad_page_fault;
 224
 225                pmd_val(*pmd) = pmd_val(*pmd_k);
 226                pte_k = pte_offset_kernel(pmd_k, address);
 227
 228                if (!pte_present(*pte_k))
 229                        goto bad_page_fault;
 230                return;
 231        }
 232bad_page_fault:
 233        bad_page_fault(regs, address, SIGKILL);
 234        return;
 235}
 236
 237
 238void
 239bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 240{
 241        extern void die(const char*, struct pt_regs*, long);
 242        const struct exception_table_entry *entry;
 243
 244        /* Are we prepared to handle this kernel fault?  */
 245        if ((entry = search_exception_tables(regs->pc)) != NULL) {
 246                pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
 247                         current->comm, regs->pc, entry->fixup);
 248                current->thread.bad_uaddr = address;
 249                regs->pc = entry->fixup;
 250                return;
 251        }
 252
 253        /* Oops. The kernel tried to access some bad page. We'll have to
 254         * terminate things with extreme prejudice.
 255         */
 256        pr_alert("Unable to handle kernel paging request at virtual "
 257                 "address %08lx\n pc = %08lx, ra = %08lx\n",
 258                 address, regs->pc, regs->areg[0]);
 259        die("Oops", regs, sig);
 260        do_exit(sig);
 261}
 262