arch/metag/mm/fault.c

   1 /*
   2  *  Meta page fault handling.
   3  *
   4  *  Copyright (C) 2005-2012 Imagination Technologies Ltd.
   5  */
   6
   7 #include <linux/mman.h>
   8 #include <linux/mm.h>
   9 #include <linux/kernel.h>
  10 #include <linux/ptrace.h>
  11 #include <linux/sched/debug.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/uaccess.h>
  14
  15 #include <asm/tlbflush.h>
  16 #include <asm/mmu.h>
  17 #include <asm/traps.h>
  18
  19 /* Clear any pending catch buffer state. */
  20 static void clear_cbuf_entry(struct pt_regs *regs, unsigned long addr,
  21                              unsigned int trapno)
  22 {
  23         PTBICTXEXTCB0 cbuf = regs->extcb0;
  24
  25         switch (trapno) {
  26                 /* Instruction fetch faults leave no catch buffer state. */
  27         case TBIXXF_SIGNUM_IGF:
  28         case TBIXXF_SIGNUM_IPF:
  29                 return;
  30         default:
  31                 if (cbuf[0].CBAddr == addr) {
  32                         cbuf[0].CBAddr = 0;
  33                         cbuf[0].CBFlags &= ~TXCATCH0_FAULT_BITS;
  34
  35                         /* And, as this is the ONLY catch entry, we
  36                          * need to clear the cbuf bit from the context!
  37                          */
  38                         regs->ctx.SaveMask &= ~(TBICTX_CBUF_BIT |
  39                                                 TBICTX_XCBF_BIT);
  40
  41                         return;
  42                 }
  43                 pr_err("Failed to clear cbuf entry!\n");
  44         }
  45 }
  46
  47 int show_unhandled_signals = 1;
  48
  49 int do_page_fault(struct pt_regs *regs, unsigned long address,
  50                   unsigned int write_access, unsigned int trapno)
  51 {
  52         struct task_struct *tsk;
  53         struct mm_struct *mm;
  54         struct vm_area_struct *vma, *prev_vma;
  55         siginfo_t info;
  56         int fault;
  57         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  58
  59         tsk = current;
  60
  61         if ((address >= VMALLOC_START) && (address < VMALLOC_END)) {
  62                 /*
  63                  * Synchronize this task's top level page-table
  64                  * with the 'reference' page table.
  65                  *
  66                  * Do _not_ use "tsk" here. We might be inside
  67                  * an interrupt in the middle of a task switch..
  68                  */
  69                 int offset = pgd_index(address);
  70                 pgd_t *pgd, *pgd_k;
  71                 pud_t *pud, *pud_k;
  72                 pmd_t *pmd, *pmd_k;
  73                 pte_t *pte_k;
  74
  75                 pgd = ((pgd_t *)mmu_get_base()) + offset;
  76                 pgd_k = swapper_pg_dir + offset;
  77
  78                 /* This will never happen with the folded page table. */
  79                 if (!pgd_present(*pgd)) {
  80                         if (!pgd_present(*pgd_k))
  81                                 goto bad_area_nosemaphore;
  82                         set_pgd(pgd, *pgd_k);
  83                         return 0;
  84                 }
  85
  86                 pud = pud_offset(pgd, address);
  87                 pud_k = pud_offset(pgd_k, address);
  88                 if (!pud_present(*pud_k))
  89                         goto bad_area_nosemaphore;
  90                 set_pud(pud, *pud_k);
  91
  92                 pmd = pmd_offset(pud, address);
  93                 pmd_k = pmd_offset(pud_k, address);
  94                 if (!pmd_present(*pmd_k))
  95                         goto bad_area_nosemaphore;
  96                 set_pmd(pmd, *pmd_k);
  97
  98                 pte_k = pte_offset_kernel(pmd_k, address);
  99                 if (!pte_present(*pte_k))
 100                         goto bad_area_nosemaphore;
 101
 102                 /* May only be needed on Chorus2 */
 103                 flush_tlb_all();
 104                 return 0;
 105         }
 106
 107         mm = tsk->mm;
 108
 109         if (faulthandler_disabled() || !mm)
 110                 goto no_context;
 111
 112         if (user_mode(regs))
 113                 flags |= FAULT_FLAG_USER;
 114 retry:
 115         down_read(&mm->mmap_sem);
 116
 117         vma = find_vma_prev(mm, address, &prev_vma);
 118
 119         if (!vma || address < vma->vm_start)
 120                 goto check_expansion;
 121
 122 good_area:
 123         if (write_access) {
 124                 if (!(vma->vm_flags & VM_WRITE))
 125                         goto bad_area;
 126                 flags |= FAULT_FLAG_WRITE;
 127         } else {
 128                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 129                         goto bad_area;
 130         }
 131
 132         /*
 133          * If for any reason at all we couldn't handle the fault,
 134          * make sure we exit gracefully rather than endlessly redo
 135          * the fault.
 136          */
 137         fault = handle_mm_fault(vma, address, flags);
 138
 139         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 140                 return 0;
 141
 142         if (unlikely(fault & VM_FAULT_ERROR)) {
 143                 if (fault & VM_FAULT_OOM)
 144                         goto out_of_memory;
 145                 else if (fault & VM_FAULT_SIGSEGV)
 146                         goto bad_area;
 147                 else if (fault & VM_FAULT_SIGBUS)
 148                         goto do_sigbus;
 149                 BUG();
 150         }
 151         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 152                 if (fault & VM_FAULT_MAJOR)
 153                         tsk->maj_flt++;
 154                 else
 155                         tsk->min_flt++;
 156                 if (fault & VM_FAULT_RETRY) {
 157                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 158                         flags |= FAULT_FLAG_TRIED;
 159
 160                         /*
 161                          * No need to up_read(&mm->mmap_sem) as we would
 162                          * have already released it in __lock_page_or_retry
 163                          * in mm/filemap.c.
 164                          */
 165
 166                         goto retry;
 167                 }
 168         }
 169
 170         up_read(&mm->mmap_sem);
 171         return 0;
 172
 173 check_expansion:
 174         vma = prev_vma;
 175         if (vma && (expand_stack(vma, address) == 0))
 176                 goto good_area;
 177
 178 bad_area:
 179         up_read(&mm->mmap_sem);
 180
 181 bad_area_nosemaphore:
 182         if (user_mode(regs)) {
 183                 info.si_signo = SIGSEGV;
 184                 info.si_errno = 0;
 185                 info.si_code = SEGV_MAPERR;
 186                 info.si_addr = (__force void __user *)address;
 187                 info.si_trapno = trapno;
 188
 189                 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
 190                     printk_ratelimit()) {
 191                         printk("%s%s[%d]: segfault at %lx pc %08x sp %08x write %d trap %#x (%s)",
 192                                task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
 193                                tsk->comm, task_pid_nr(tsk), address,
 194                                regs->ctx.CurrPC, regs->ctx.AX[0].U0,
 195                                write_access, trapno, trap_name(trapno));
 196                         print_vma_addr(" in ", regs->ctx.CurrPC);
 197                         print_vma_addr(" rtp in ", regs->ctx.DX[4].U1);
 198                         printk("\n");
 199                         show_regs(regs);
 200                 }
 201                 force_sig_info(SIGSEGV, &info, tsk);
 202                 return 1;
 203         }
 204         goto no_context;
 205
 206 do_sigbus:
 207         up_read(&mm->mmap_sem);
 208
 209         /*
 210          * Send a sigbus, regardless of whether we were in kernel
 211          * or user mode.
 212          */
 213         info.si_signo = SIGBUS;
 214         info.si_errno = 0;
 215         info.si_code = BUS_ADRERR;
 216         info.si_addr = (__force void __user *)address;
 217         info.si_trapno = trapno;
 218         force_sig_info(SIGBUS, &info, tsk);
 219
 220         /* Kernel mode? Handle exceptions or die */
 221         if (!user_mode(regs))
 222                 goto no_context;
 223
 224         return 1;
 225
 226         /*
 227          * We ran out of memory, or some other thing happened to us that made
 228          * us unable to handle the page fault gracefully.
 229          */
 230 out_of_memory:
 231         up_read(&mm->mmap_sem);
 232         if (user_mode(regs)) {
 233                 pagefault_out_of_memory();
 234                 return 1;
 235         }
 236
 237 no_context:
 238         /* Are we prepared to handle this kernel fault?  */
 239         if (fixup_exception(regs)) {
 240                 clear_cbuf_entry(regs, address, trapno);
 241                 return 1;
 242         }
 243
 244         die("Oops", regs, (write_access << 15) | trapno, address);
 245         do_exit(SIGKILL);
 246 }