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         if (user_mode(regs))
  90                 flags |= FAULT_FLAG_USER;
  91 retry:
  92         down_read(&mm->mmap_sem);
  93
  94         vma = find_vma(mm, address);
  95         if (!vma)
  96                 goto bad_area;
  97         if (vma->vm_start <= address)
  98                 goto good_area;
  99         if (!(vma->vm_flags & VM_GROWSDOWN))
 100                 goto bad_area;
 101         if (expand_stack(vma, address))
 102                 goto bad_area;
 103
 104         /*
 105          * Ok, we have a good vm_area for this memory access, so we
 106          * can handle it...
 107          */
 108 good_area:
 109         code = SEGV_ACCERR;
 110
 111         switch (ecr) {
 112         case ECR_PROTECTION_X:
 113         case ECR_TLB_MISS_X:
 114                 if (!(vma->vm_flags & VM_EXEC))
 115                         goto bad_area;
 116                 break;
 117         case ECR_PROTECTION_R:
 118         case ECR_TLB_MISS_R:
 119                 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 120                         goto bad_area;
 121                 break;
 122         case ECR_PROTECTION_W:
 123         case ECR_TLB_MISS_W:
 124                 if (!(vma->vm_flags & VM_WRITE))
 125                         goto bad_area;
 126                 flags |= FAULT_FLAG_WRITE;
 127                 break;
 128         default:
 129                 panic("Unhandled case %lu in do_page_fault!", ecr);
 130         }
 131
 132         /*
 133          * If for any reason at all we couldn't handle the fault, make
 134          * sure we exit gracefully rather than endlessly redo the
 135          * fault.
 136          */
 137         fault = handle_mm_fault(mm, vma, address, flags);
 138
 139         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 140                 return;
 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_SIGBUS)
 146                         goto do_sigbus;
 147                 BUG();
 148         }
 149
 150         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 151                 if (fault & VM_FAULT_MAJOR)
 152                         tsk->maj_flt++;
 153                 else
 154                         tsk->min_flt++;
 155                 if (fault & VM_FAULT_RETRY) {
 156                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 157                         flags |= FAULT_FLAG_TRIED;
 158
 159                         /*
 160                          * No need to up_read(&mm->mmap_sem) as we would have
 161                          * already released it in __lock_page_or_retry() in
 162                          * mm/filemap.c.
 163                          */
 164                         goto retry;
 165                 }
 166         }
 167
 168         up_read(&mm->mmap_sem);
 169         return;
 170
 171         /*
 172          * Something tried to access memory that isn't in our memory
 173          * map. Fix it, but check if it's kernel or user first...
 174          */
 175 bad_area:
 176         up_read(&mm->mmap_sem);
 177
 178         if (user_mode(regs)) {
 179                 if (exception_trace && printk_ratelimit())
 180                         printk("%s%s[%d]: segfault at %08lx pc %08lx "
 181                                "sp %08lx ecr %lu\n",
 182                                is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
 183                                tsk->comm, tsk->pid, address, regs->pc,
 184                                regs->sp, ecr);
 185                 _exception(SIGSEGV, regs, code, address);
 186                 return;
 187         }
 188
 189 no_context:
 190         /* Are we prepared to handle this kernel fault? */
 191         fixup = search_exception_tables(regs->pc);
 192         if (fixup) {
 193                 regs->pc = fixup->fixup;
 194                 return;
 195         }
 196
 197         /*
 198          * Oops. The kernel tried to access some bad page. We'll have
 199          * to terminate things with extreme prejudice.
 200          */
 201         if (address < PAGE_SIZE)
 202                 printk(KERN_ALERT
 203                        "Unable to handle kernel NULL pointer dereference");
 204         else
 205                 printk(KERN_ALERT
 206                        "Unable to handle kernel paging request");
 207         printk(" at virtual address %08lx\n", address);
 208
 209         page = sysreg_read(PTBR);
 210         printk(KERN_ALERT "ptbr = %08lx", page);
 211         if (address >= TASK_SIZE)
 212                 page = (unsigned long)swapper_pg_dir;
 213         if (page) {
 214                 page = ((unsigned long *)page)[address >> 22];
 215                 printk(" pgd = %08lx", page);
 216                 if (page & _PAGE_PRESENT) {
 217                         page &= PAGE_MASK;
 218                         address &= 0x003ff000;
 219                         page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
 220                         printk(" pte = %08lx", page);
 221                 }
 222         }
 223         printk("\n");
 224         die("Kernel access of bad area", regs, signr);
 225         return;
 226
 227         /*
 228          * We ran out of memory, or some other thing happened to us
 229          * that made us unable to handle the page fault gracefully.
 230          */
 231 out_of_memory:
 232         up_read(&mm->mmap_sem);
 233         if (!user_mode(regs))
 234                 goto no_context;
 235         pagefault_out_of_memory();
 236         return;
 237
 238 do_sigbus:
 239         up_read(&mm->mmap_sem);
 240
 241         /* Kernel mode? Handle exceptions or die */
 242         signr = SIGBUS;
 243         code = BUS_ADRERR;
 244         if (!user_mode(regs))
 245                 goto no_context;
 246
 247         if (exception_trace)
 248                 printk("%s%s[%d]: bus error at %08lx pc %08lx "
 249                        "sp %08lx ecr %lu\n",
 250                        is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
 251                        tsk->comm, tsk->pid, address, regs->pc,
 252                        regs->sp, ecr);
 253
 254         _exception(SIGBUS, regs, BUS_ADRERR, address);
 255 }
 256
 257 asmlinkage void do_bus_error(unsigned long addr, int write_access,
 258                              struct pt_regs *regs)
 259 {
 260         printk(KERN_ALERT
 261                "Bus error at physical address 0x%08lx (%s access)\n",
 262                addr, write_access ? "write" : "read");
 263         printk(KERN_INFO "DTLB dump:\n");
 264         dump_dtlb();
 265         die("Bus Error", regs, SIGKILL);
 266 }