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         int fault;
  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         down_read(&mm->mmap_sem);
  90
  91         vma = find_vma(mm, address);
  92         if (!vma)
  93                 goto bad_area;
  94         if (vma->vm_start <= address)
  95                 goto good_area;
  96         if (!(vma->vm_flags & VM_GROWSDOWN))
  97                 goto bad_area;
  98         if (expand_stack(vma, address))
  99                 goto bad_area;
 100
 101         /*
 102          * Ok, we have a good vm_area for this memory access, so we
 103          * can handle it...
 104          */
 105 good_area:
 106         code = SEGV_ACCERR;
 107         writeaccess = 0;
 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                 writeaccess = 1;
 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 survive:
 136         fault = handle_mm_fault(mm, vma, address, writeaccess);
 137         if (unlikely(fault & VM_FAULT_ERROR)) {
 138                 if (fault & VM_FAULT_OOM)
 139                         goto out_of_memory;
 140                 else if (fault & VM_FAULT_SIGBUS)
 141                         goto do_sigbus;
 142                 BUG();
 143         }
 144         if (fault & VM_FAULT_MAJOR)
 145                 tsk->maj_flt++;
 146         else
 147                 tsk->min_flt++;
 148
 149         up_read(&mm->mmap_sem);
 150         return;
 151
 152         /*
 153          * Something tried to access memory that isn't in our memory
 154          * map. Fix it, but check if it's kernel or user first...
 155          */
 156 bad_area:
 157         up_read(&mm->mmap_sem);
 158
 159         if (user_mode(regs)) {
 160                 if (exception_trace && printk_ratelimit())
 161                         printk("%s%s[%d]: segfault at %08lx pc %08lx "
 162                                "sp %08lx ecr %lu\n",
 163                                is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
 164                                tsk->comm, tsk->pid, address, regs->pc,
 165                                regs->sp, ecr);
 166                 _exception(SIGSEGV, regs, code, address);
 167                 return;
 168         }
 169
 170 no_context:
 171         /* Are we prepared to handle this kernel fault? */
 172         fixup = search_exception_tables(regs->pc);
 173         if (fixup) {
 174                 regs->pc = fixup->fixup;
 175                 return;
 176         }
 177
 178         /*
 179          * Oops. The kernel tried to access some bad page. We'll have
 180          * to terminate things with extreme prejudice.
 181          */
 182         if (address < PAGE_SIZE)
 183                 printk(KERN_ALERT
 184                        "Unable to handle kernel NULL pointer dereference");
 185         else
 186                 printk(KERN_ALERT
 187                        "Unable to handle kernel paging request");
 188         printk(" at virtual address %08lx\n", address);
 189
 190         page = sysreg_read(PTBR);
 191         printk(KERN_ALERT "ptbr = %08lx", page);
 192         if (address >= TASK_SIZE)
 193                 page = (unsigned long)swapper_pg_dir;
 194         if (page) {
 195                 page = ((unsigned long *)page)[address >> 22];
 196                 printk(" pgd = %08lx", page);
 197                 if (page & _PAGE_PRESENT) {
 198                         page &= PAGE_MASK;
 199                         address &= 0x003ff000;
 200                         page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
 201                         printk(" pte = %08lx", page);
 202                 }
 203         }
 204         printk("\n");
 205         die("Kernel access of bad area", regs, signr);
 206         return;
 207
 208         /*
 209          * We ran out of memory, or some other thing happened to us
 210          * that made us unable to handle the page fault gracefully.
 211          */
 212 out_of_memory:
 213         up_read(&mm->mmap_sem);
 214         if (is_global_init(current)) {
 215                 yield();
 216                 down_read(&mm->mmap_sem);
 217                 goto survive;
 218         }
 219         printk("VM: Killing process %s\n", tsk->comm);
 220         if (user_mode(regs))
 221                 do_group_exit(SIGKILL);
 222         goto no_context;
 223
 224 do_sigbus:
 225         up_read(&mm->mmap_sem);
 226
 227         /* Kernel mode? Handle exceptions or die */
 228         signr = SIGBUS;
 229         code = BUS_ADRERR;
 230         if (!user_mode(regs))
 231                 goto no_context;
 232
 233         if (exception_trace)
 234                 printk("%s%s[%d]: bus error at %08lx pc %08lx "
 235                        "sp %08lx ecr %lu\n",
 236                        is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
 237                        tsk->comm, tsk->pid, address, regs->pc,
 238                        regs->sp, ecr);
 239
 240         _exception(SIGBUS, regs, BUS_ADRERR, address);
 241 }
 242
 243 asmlinkage void do_bus_error(unsigned long addr, int write_access,
 244                              struct pt_regs *regs)
 245 {
 246         printk(KERN_ALERT
 247                "Bus error at physical address 0x%08lx (%s access)\n",
 248                addr, write_access ? "write" : "read");
 249         printk(KERN_INFO "DTLB dump:\n");
 250         dump_dtlb();
 251         die("Bus Error", regs, SIGKILL);
 252 }
 253
 254 /*
 255  * This functionality is currently not possible to implement because
 256  * we're using segmentation to ensure a fixed mapping of the kernel
 257  * virtual address space.
 258  *
 259  * It would be possible to implement this, but it would require us to
 260  * disable segmentation at startup and load the kernel mappings into
 261  * the TLB like any other pages. There will be lots of trickery to
 262  * avoid recursive invocation of the TLB miss handler, though...
 263  */
 264 #ifdef CONFIG_DEBUG_PAGEALLOC
 265 void kernel_map_pages(struct page *page, int numpages, int enable)
 266 {
 267
 268 }
 269 EXPORT_SYMBOL(kernel_map_pages);
 270 #endif