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
  16 #include <asm/kdebug.h>
  17 #include <asm/mmu_context.h>
  18 #include <asm/sysreg.h>
  19 #include <asm/tlb.h>
  20 #include <asm/uaccess.h>
  21
  22 #ifdef CONFIG_KPROBES
  23 ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
  24
  25 /* Hook to register for page fault notifications */
  26 int register_page_fault_notifier(struct notifier_block *nb)
  27 {
  28         return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
  29 }
  30
  31 int unregister_page_fault_notifier(struct notifier_block *nb)
  32 {
  33         return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
  34 }
  35
  36 static inline int notify_page_fault(enum die_val val, struct pt_regs *regs,
  37                                     int trap, int sig)
  38 {
  39         struct die_args args = {
  40                 .regs = regs,
  41                 .trapnr = trap,
  42         };
  43         return atomic_notifier_call_chain(&notify_page_fault_chain, val, &args);
  44 }
  45 #else
  46 static inline int notify_page_fault(enum die_val val, struct pt_regs *regs,
  47                                     int trap, int sig)
  48 {
  49         return NOTIFY_DONE;
  50 }
  51 #endif
  52
  53 int exception_trace = 1;
  54
  55 /*
  56  * This routine handles page faults. It determines the address and the
  57  * problem, and then passes it off to one of the appropriate routines.
  58  *
  59  * ecr is the Exception Cause Register. Possible values are:
  60  *   6:  Protection fault (instruction access)
  61  *   15: Protection fault (read access)
  62  *   16: Protection fault (write access)
  63  *   20: Page not found (instruction access)
  64  *   24: Page not found (read access)
  65  *   28: Page not found (write access)
  66  */
  67 asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
  68 {
  69         struct task_struct *tsk;
  70         struct mm_struct *mm;
  71         struct vm_area_struct *vma;
  72         const struct exception_table_entry *fixup;
  73         unsigned long address;
  74         unsigned long page;
  75         int writeaccess;
  76         long signr;
  77         int code;
  78
  79         if (notify_page_fault(DIE_PAGE_FAULT, regs,
  80                               ecr, SIGSEGV) == NOTIFY_STOP)
  81                 return;
  82
  83         address = sysreg_read(TLBEAR);
  84
  85         tsk = current;
  86         mm = tsk->mm;
  87
  88         signr = SIGSEGV;
  89         code = SEGV_MAPERR;
  90
  91         /*
  92          * If we're in an interrupt or have no user context, we must
  93          * not take the fault...
  94          */
  95         if (in_atomic() || !mm || regs->sr & SYSREG_BIT(GM))
  96                 goto no_context;
  97
  98         local_irq_enable();
  99
 100         down_read(&mm->mmap_sem);
 101
 102         vma = find_vma(mm, address);
 103         if (!vma)
 104                 goto bad_area;
 105         if (vma->vm_start <= address)
 106                 goto good_area;
 107         if (!(vma->vm_flags & VM_GROWSDOWN))
 108                 goto bad_area;
 109         if (expand_stack(vma, address))
 110                 goto bad_area;
 111
 112         /*
 113          * Ok, we have a good vm_area for this memory access, so we
 114          * can handle it...
 115          */
 116 good_area:
 117         code = SEGV_ACCERR;
 118         writeaccess = 0;
 119
 120         switch (ecr) {
 121         case ECR_PROTECTION_X:
 122         case ECR_TLB_MISS_X:
 123                 if (!(vma->vm_flags & VM_EXEC))
 124                         goto bad_area;
 125                 break;
 126         case ECR_PROTECTION_R:
 127         case ECR_TLB_MISS_R:
 128                 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 129                         goto bad_area;
 130                 break;
 131         case ECR_PROTECTION_W:
 132         case ECR_TLB_MISS_W:
 133                 if (!(vma->vm_flags & VM_WRITE))
 134                         goto bad_area;
 135                 writeaccess = 1;
 136                 break;
 137         default:
 138                 panic("Unhandled case %lu in do_page_fault!", ecr);
 139         }
 140
 141         /*
 142          * If for any reason at all we couldn't handle the fault, make
 143          * sure we exit gracefully rather than endlessly redo the
 144          * fault.
 145          */
 146 survive:
 147         switch (handle_mm_fault(mm, vma, address, writeaccess)) {
 148         case VM_FAULT_MINOR:
 149                 tsk->min_flt++;
 150                 break;
 151         case VM_FAULT_MAJOR:
 152                 tsk->maj_flt++;
 153                 break;
 154         case VM_FAULT_SIGBUS:
 155                 goto do_sigbus;
 156         case VM_FAULT_OOM:
 157                 goto out_of_memory;
 158         default:
 159                 BUG();
 160         }
 161
 162         up_read(&mm->mmap_sem);
 163         return;
 164
 165         /*
 166          * Something tried to access memory that isn't in our memory
 167          * map. Fix it, but check if it's kernel or user first...
 168          */
 169 bad_area:
 170         up_read(&mm->mmap_sem);
 171
 172         if (user_mode(regs)) {
 173                 if (exception_trace)
 174                         printk("%s%s[%d]: segfault at %08lx pc %08lx "
 175                                "sp %08lx ecr %lu\n",
 176                                is_init(tsk) ? KERN_EMERG : KERN_INFO,
 177                                tsk->comm, tsk->pid, address, regs->pc,
 178                                regs->sp, ecr);
 179                 _exception(SIGSEGV, regs, code, address);
 180                 return;
 181         }
 182
 183 no_context:
 184         /* Are we prepared to handle this kernel fault? */
 185         fixup = search_exception_tables(regs->pc);
 186         if (fixup) {
 187                 regs->pc = fixup->fixup;
 188                 return;
 189         }
 190
 191         /*
 192          * Oops. The kernel tried to access some bad page. We'll have
 193          * to terminate things with extreme prejudice.
 194          */
 195         if (address < PAGE_SIZE)
 196                 printk(KERN_ALERT
 197                        "Unable to handle kernel NULL pointer dereference");
 198         else
 199                 printk(KERN_ALERT
 200                        "Unable to handle kernel paging request");
 201         printk(" at virtual address %08lx\n", address);
 202
 203         page = sysreg_read(PTBR);
 204         printk(KERN_ALERT "ptbr = %08lx", page);
 205         if (page) {
 206                 page = ((unsigned long *)page)[address >> 22];
 207                 printk(" pgd = %08lx", page);
 208                 if (page & _PAGE_PRESENT) {
 209                         page &= PAGE_MASK;
 210                         address &= 0x003ff000;
 211                         page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
 212                         printk(" pte = %08lx", page);
 213                 }
 214         }
 215         printk("\n");
 216         die("Kernel access of bad area", regs, signr);
 217         return;
 218
 219         /*
 220          * We ran out of memory, or some other thing happened to us
 221          * that made us unable to handle the page fault gracefully.
 222          */
 223 out_of_memory:
 224         up_read(&mm->mmap_sem);
 225         if (is_init(current)) {
 226                 yield();
 227                 down_read(&mm->mmap_sem);
 228                 goto survive;
 229         }
 230         printk("VM: Killing process %s\n", tsk->comm);
 231         if (user_mode(regs))
 232                 do_exit(SIGKILL);
 233         goto no_context;
 234
 235 do_sigbus:
 236         up_read(&mm->mmap_sem);
 237
 238         /* Kernel mode? Handle exceptions or die */
 239         signr = SIGBUS;
 240         code = BUS_ADRERR;
 241         if (!user_mode(regs))
 242                 goto no_context;
 243
 244         if (exception_trace)
 245                 printk("%s%s[%d]: bus error at %08lx pc %08lx "
 246                        "sp %08lx ecr %lu\n",
 247                        is_init(tsk) ? KERN_EMERG : KERN_INFO,
 248                        tsk->comm, tsk->pid, address, regs->pc,
 249                        regs->sp, ecr);
 250
 251         _exception(SIGBUS, regs, BUS_ADRERR, address);
 252 }
 253
 254 asmlinkage void do_bus_error(unsigned long addr, int write_access,
 255                              struct pt_regs *regs)
 256 {
 257         printk(KERN_ALERT
 258                "Bus error at physical address 0x%08lx (%s access)\n",
 259                addr, write_access ? "write" : "read");
 260         printk(KERN_INFO "DTLB dump:\n");
 261         dump_dtlb();
 262         die("Bus Error", regs, SIGKILL);
 263 }
 264
 265 /*
 266  * This functionality is currently not possible to implement because
 267  * we're using segmentation to ensure a fixed mapping of the kernel
 268  * virtual address space.
 269  *
 270  * It would be possible to implement this, but it would require us to
 271  * disable segmentation at startup and load the kernel mappings into
 272  * the TLB like any other pages. There will be lots of trickery to
 273  * avoid recursive invocation of the TLB miss handler, though...
 274  */
 275 #ifdef CONFIG_DEBUG_PAGEALLOC
 276 void kernel_map_pages(struct page *page, int numpages, int enable)
 277 {
 278
 279 }
 280 EXPORT_SYMBOL(kernel_map_pages);
 281 #endif