linux/arch/avr32/mm/fault.c
<<
>>
Prefs
   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
  24static 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
  36static inline int notify_page_fault(struct pt_regs *regs, int trap)
  37{
  38        return 0;
  39}
  40#endif
  41
  42int 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 */
  56asmlinkage 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         */
 105good_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         */
 135survive:
 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         */
 156bad_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
 170no_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         */
 212out_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
 224do_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
 243asmlinkage 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
 265void kernel_map_pages(struct page *page, int numpages, int enable)
 266{
 267
 268}
 269EXPORT_SYMBOL(kernel_map_pages);
 270#endif
 271