arch/avr32/mm/fault.c

   1 /*
   2  * Copyright (C) 2004-2006 Atmel Corporation
   3  *
   4  * Based on linux/arch/sh/mm/fault.c:
   5  *   Copyright (C) 1999  Niibe Yutaka
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/mm.h>
  13 #include <linux/module.h>
  14 #include <linux/pagemap.h>
  15 #include <linux/kdebug.h>
  16 #include <linux/kprobes.h>
  17
  18 #include <asm/mmu_context.h>
  19 #include <asm/sysreg.h>
  20 #include <asm/tlb.h>
  21 #include <asm/uaccess.h>
  22
  23 #ifdef CONFIG_KPROBES
  24 static inline int notify_page_fault(struct pt_regs *regs, int trap)
  25 {
  26         int ret = 0;
  27
  28         if (!user_mode(regs)) {
  29                 if (kprobe_running() && kprobe_fault_handler(regs, trap))
  30                         ret = 1;
  31         }
  32
  33         return ret;
  34 }
  35 #else
  36 static inline int notify_page_fault(struct pt_regs *regs, int trap)
  37 {
  38         return 0;
  39 }
  40 #endif
  41
  42 int exception_trace = 1;
  43
  44 /*
  45  * This routine handles page faults. It determines the address and the
  46  * problem, and then passes it off to one of the appropriate routines.
  47  *
  48  * ecr is the Exception Cause Register. Possible values are:
  49  *   6:  Protection fault (instruction access)
  50  *   15: Protection fault (read access)
  51  *   16: Protection fault (write access)
  52  *   20: Page not found (instruction access)
  53  *   24: Page not found (read access)
  54  *   28: Page not found (write access)
  55  */
  56 asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
  57 {
  58         struct task_struct *tsk;
  59         struct mm_struct *mm;
  60         struct vm_area_struct *vma;
  61         const struct exception_table_entry *fixup;
  62         unsigned long address;
  63         unsigned long page;
  64         long signr;
  65         int code;
  66         int fault;
  67         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  68
  69         if (notify_page_fault(regs, ecr))
  70                 return;
  71
  72         address = sysreg_read(TLBEAR);
  73
  74         tsk = current;
  75         mm = tsk->mm;
  76
  77         signr = SIGSEGV;
  78         code = SEGV_MAPERR;
  79
  80         /*
  81          * If we're in an interrupt or have no user context, we must
  82          * not take the fault...
  83          */
  84         if (in_atomic() || !mm || regs->sr & SYSREG_BIT(GM))
  85                 goto no_context;
  86
  87         local_irq_enable();
  88
  89 retry:
  90         down_read(&mm->mmap_sem);
  91
  92         vma = find_vma(mm, address);
  93         if (!vma)
  94                 goto bad_area;
  95         if (vma->vm_start <= address)
  96                 goto good_area;
  97         if (!(vma->vm_flags & VM_GROWSDOWN))
  98                 goto bad_area;
  99         if (expand_stack(vma, address))
 100                 goto bad_area;
 101
 102         /*
 103          * Ok, we have a good vm_area for this memory access, so we
 104          * can handle it...
 105          */
 106 good_area:
 107         code = SEGV_ACCERR;
 108
 109         switch (ecr) {
 110         case ECR_PROTECTION_X:
 111         case ECR_TLB_MISS_X:
 112                 if (!(vma->vm_flags & VM_EXEC))
 113                         goto bad_area;
 114                 break;
 115         case ECR_PROTECTION_R:
 116         case ECR_TLB_MISS_R:
 117                 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 118                         goto bad_area;
 119                 break;
 120         case ECR_PROTECTION_W:
 121         case ECR_TLB_MISS_W:
 122                 if (!(vma->vm_flags & VM_WRITE))
 123                         goto bad_area;
 124                 flags |= FAULT_FLAG_WRITE;
 125                 break;
 126         default:
 127                 panic("Unhandled case %lu in do_page_fault!", ecr);
 128         }
 129
 130         /*
 131          * If for any reason at all we couldn't handle the fault, make
 132          * sure we exit gracefully rather than endlessly redo the
 133          * fault.
 134          */
 135         fault = handle_mm_fault(mm, vma, address, flags);
 136
 137         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 138                 return;
 139
 140         if (unlikely(fault & VM_FAULT_ERROR)) {
 141                 if (fault & VM_FAULT_OOM)
 142                         goto out_of_memory;
 143                 else if (fault & VM_FAULT_SIGBUS)
 144                         goto do_sigbus;
 145                 BUG();
 146         }
 147
 148         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 149                 if (fault & VM_FAULT_MAJOR)
 150                         tsk->maj_flt++;
 151                 else
 152                         tsk->min_flt++;
 153                 if (fault & VM_FAULT_RETRY) {
 154                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 155                         flags |= FAULT_FLAG_TRIED;
 156
 157                         /*
 158                          * No need to up_read(&mm->mmap_sem) as we would have
 159                          * already released it in __lock_page_or_retry() in
 160                          * mm/filemap.c.
 161                          */
 162                         goto retry;
 163                 }
 164         }
 165
 166         up_read(&mm->mmap_sem);
 167         return;
 168
 169         /*
 170          * Something tried to access memory that isn't in our memory
 171          * map. Fix it, but check if it's kernel or user first...
 172          */
 173 bad_area:
 174         up_read(&mm->mmap_sem);
 175
 176         if (user_mode(regs)) {
 177                 if (exception_trace && printk_ratelimit())
 178                         printk("%s%s[%d]: segfault at %08lx pc %08lx "
 179                                "sp %08lx ecr %lu\n",
 180                                is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
 181                                tsk->comm, tsk->pid, address, regs->pc,
 182                                regs->sp, ecr);
 183                 _exception(SIGSEGV, regs, code, address);
 184                 return;
 185         }
 186
 187 no_context:
 188         /* Are we prepared to handle this kernel fault? */
 189         fixup = search_exception_tables(regs->pc);
 190         if (fixup) {
 191                 regs->pc = fixup->fixup;
 192                 return;
 193         }
 194
 195         /*
 196          * Oops. The kernel tried to access some bad page. We'll have
 197          * to terminate things with extreme prejudice.
 198          */
 199         if (address < PAGE_SIZE)
 200                 printk(KERN_ALERT
 201                        "Unable to handle kernel NULL pointer dereference");
 202         else
 203                 printk(KERN_ALERT
 204                        "Unable to handle kernel paging request");
 205         printk(" at virtual address %08lx\n", address);
 206
 207         page = sysreg_read(PTBR);
 208         printk(KERN_ALERT "ptbr = %08lx", page);
 209         if (address >= TASK_SIZE)
 210                 page = (unsigned long)swapper_pg_dir;
 211         if (page) {
 212                 page = ((unsigned long *)page)[address >> 22];
 213                 printk(" pgd = %08lx", page);
 214                 if (page & _PAGE_PRESENT) {
 215                         page &= PAGE_MASK;
 216                         address &= 0x003ff000;
 217                         page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
 218                         printk(" pte = %08lx", page);
 219                 }
 220         }
 221         printk("\n");
 222         die("Kernel access of bad area", regs, signr);
 223         return;
 224
 225         /*
 226          * We ran out of memory, or some other thing happened to us
 227          * that made us unable to handle the page fault gracefully.
 228          */
 229 out_of_memory:
 230         up_read(&mm->mmap_sem);
 231         pagefault_out_of_memory();
 232         if (!user_mode(regs))
 233                 goto no_context;
 234         return;
 235
 236 do_sigbus:
 237         up_read(&mm->mmap_sem);
 238
 239         /* Kernel mode? Handle exceptions or die */
 240         signr = SIGBUS;
 241         code = BUS_ADRERR;
 242         if (!user_mode(regs))
 243                 goto no_context;
 244
 245         if (exception_trace)
 246                 printk("%s%s[%d]: bus error at %08lx pc %08lx "
 247                        "sp %08lx ecr %lu\n",
 248                        is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
 249                        tsk->comm, tsk->pid, address, regs->pc,
 250                        regs->sp, ecr);
 251
 252         _exception(SIGBUS, regs, BUS_ADRERR, address);
 253 }
 254
 255 asmlinkage void do_bus_error(unsigned long addr, int write_access,
 256                              struct pt_regs *regs)
 257 {
 258         printk(KERN_ALERT
 259                "Bus error at physical address 0x%08lx (%s access)\n",
 260                addr, write_access ? "write" : "read");
 261         printk(KERN_INFO "DTLB dump:\n");
 262         dump_dtlb();
 263         die("Bus Error", regs, SIGKILL);
 264 }