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         int writeaccess;
  65         long signr;
  66         int code;
  67
  68         if (notify_page_fault(regs, ecr))
  69                 return;
  70
  71         address = sysreg_read(TLBEAR);
  72
  73         tsk = current;
  74         mm = tsk->mm;
  75
  76         signr = SIGSEGV;
  77         code = SEGV_MAPERR;
  78
  79         /*
  80          * If we're in an interrupt or have no user context, we must
  81          * not take the fault...
  82          */
  83         if (in_atomic() || !mm || regs->sr & SYSREG_BIT(GM))
  84                 goto no_context;
  85
  86         local_irq_enable();
  87
  88         down_read(&mm->mmap_sem);
  89
  90         vma = find_vma(mm, address);
  91         if (!vma)
  92                 goto bad_area;
  93         if (vma->vm_start <= address)
  94                 goto good_area;
  95         if (!(vma->vm_flags & VM_GROWSDOWN))
  96                 goto bad_area;
  97         if (expand_stack(vma, address))
  98                 goto bad_area;
  99
 100         /*
 101          * Ok, we have a good vm_area for this memory access, so we
 102          * can handle it...
 103          */
 104 good_area:
 105         code = SEGV_ACCERR;
 106         writeaccess = 0;
 107
 108         switch (ecr) {
 109         case ECR_PROTECTION_X:
 110         case ECR_TLB_MISS_X:
 111                 if (!(vma->vm_flags & VM_EXEC))
 112                         goto bad_area;
 113                 break;
 114         case ECR_PROTECTION_R:
 115         case ECR_TLB_MISS_R:
 116                 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 117                         goto bad_area;
 118                 break;
 119         case ECR_PROTECTION_W:
 120         case ECR_TLB_MISS_W:
 121                 if (!(vma->vm_flags & VM_WRITE))
 122                         goto bad_area;
 123                 writeaccess = 1;
 124                 break;
 125         default:
 126                 panic("Unhandled case %lu in do_page_fault!", ecr);
 127         }
 128
 129         /*
 130          * If for any reason at all we couldn't handle the fault, make
 131          * sure we exit gracefully rather than endlessly redo the
 132          * fault.
 133          */
 134 survive:
 135         switch (handle_mm_fault(mm, vma, address, writeaccess)) {
 136         case VM_FAULT_MINOR:
 137                 tsk->min_flt++;
 138                 break;
 139         case VM_FAULT_MAJOR:
 140                 tsk->maj_flt++;
 141                 break;
 142         case VM_FAULT_SIGBUS:
 143                 goto do_sigbus;
 144         case VM_FAULT_OOM:
 145                 goto out_of_memory;
 146         default:
 147                 BUG();
 148         }
 149
 150         up_read(&mm->mmap_sem);
 151         return;
 152
 153         /*
 154          * Something tried to access memory that isn't in our memory
 155          * map. Fix it, but check if it's kernel or user first...
 156          */
 157 bad_area:
 158         up_read(&mm->mmap_sem);
 159
 160         if (user_mode(regs)) {
 161                 if (exception_trace && printk_ratelimit())
 162                         printk("%s%s[%d]: segfault at %08lx pc %08lx "
 163                                "sp %08lx ecr %lu\n",
 164                                is_init(tsk) ? KERN_EMERG : KERN_INFO,
 165                                tsk->comm, tsk->pid, address, regs->pc,
 166                                regs->sp, ecr);
 167                 _exception(SIGSEGV, regs, code, address);
 168                 return;
 169         }
 170
 171 no_context:
 172         /* Are we prepared to handle this kernel fault? */
 173         fixup = search_exception_tables(regs->pc);
 174         if (fixup) {
 175                 regs->pc = fixup->fixup;
 176                 return;
 177         }
 178
 179         /*
 180          * Oops. The kernel tried to access some bad page. We'll have
 181          * to terminate things with extreme prejudice.
 182          */
 183         if (address < PAGE_SIZE)
 184                 printk(KERN_ALERT
 185                        "Unable to handle kernel NULL pointer dereference");
 186         else
 187                 printk(KERN_ALERT
 188                        "Unable to handle kernel paging request");
 189         printk(" at virtual address %08lx\n", address);
 190
 191         page = sysreg_read(PTBR);
 192         printk(KERN_ALERT "ptbr = %08lx", page);
 193         if (page) {
 194                 page = ((unsigned long *)page)[address >> 22];
 195                 printk(" pgd = %08lx", page);
 196                 if (page & _PAGE_PRESENT) {
 197                         page &= PAGE_MASK;
 198                         address &= 0x003ff000;
 199                         page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
 200                         printk(" pte = %08lx", page);
 201                 }
 202         }
 203         printk("\n");
 204         die("Kernel access of bad area", regs, signr);
 205         return;
 206
 207         /*
 208          * We ran out of memory, or some other thing happened to us
 209          * that made us unable to handle the page fault gracefully.
 210          */
 211 out_of_memory:
 212         up_read(&mm->mmap_sem);
 213         if (is_init(current)) {
 214                 yield();
 215                 down_read(&mm->mmap_sem);
 216                 goto survive;
 217         }
 218         printk("VM: Killing process %s\n", tsk->comm);
 219         if (user_mode(regs))
 220                 do_exit(SIGKILL);
 221         goto no_context;
 222
 223 do_sigbus:
 224         up_read(&mm->mmap_sem);
 225
 226         /* Kernel mode? Handle exceptions or die */
 227         signr = SIGBUS;
 228         code = BUS_ADRERR;
 229         if (!user_mode(regs))
 230                 goto no_context;
 231
 232         if (exception_trace)
 233                 printk("%s%s[%d]: bus error at %08lx pc %08lx "
 234                        "sp %08lx ecr %lu\n",
 235                        is_init(tsk) ? KERN_EMERG : KERN_INFO,
 236                        tsk->comm, tsk->pid, address, regs->pc,
 237                        regs->sp, ecr);
 238
 239         _exception(SIGBUS, regs, BUS_ADRERR, address);
 240 }
 241
 242 asmlinkage void do_bus_error(unsigned long addr, int write_access,
 243                              struct pt_regs *regs)
 244 {
 245         printk(KERN_ALERT
 246                "Bus error at physical address 0x%08lx (%s access)\n",
 247                addr, write_access ? "write" : "read");
 248         printk(KERN_INFO "DTLB dump:\n");
 249         dump_dtlb();
 250         die("Bus Error", regs, SIGKILL);
 251 }
 252
 253 /*
 254  * This functionality is currently not possible to implement because
 255  * we're using segmentation to ensure a fixed mapping of the kernel
 256  * virtual address space.
 257  *
 258  * It would be possible to implement this, but it would require us to
 259  * disable segmentation at startup and load the kernel mappings into
 260  * the TLB like any other pages. There will be lots of trickery to
 261  * avoid recursive invocation of the TLB miss handler, though...
 262  */
 263 #ifdef CONFIG_DEBUG_PAGEALLOC
 264 void kernel_map_pages(struct page *page, int numpages, int enable)
 265 {
 266
 267 }
 268 EXPORT_SYMBOL(kernel_map_pages);
 269 #endif