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