arch/sh/mm/fault.c

   1 /*
   2  * Page fault handler for SH with an MMU.
   3  *
   4  *  Copyright (C) 1999  Niibe Yutaka
   5  *  Copyright (C) 2003  Paul Mundt
   6  *
   7  *  Based on linux/arch/i386/mm/fault.c:
   8  *   Copyright (C) 1995  Linus Torvalds
   9  *
  10  * This file is subject to the terms and conditions of the GNU General Public
  11  * License.  See the file "COPYING" in the main directory of this archive
  12  * for more details.
  13  */
  14 #include <linux/kernel.h>
  15 #include <linux/mm.h>
  16 #include <linux/hardirq.h>
  17 #include <linux/kprobes.h>
  18 #include <asm/system.h>
  19 #include <asm/mmu_context.h>
  20 #include <asm/kgdb.h>
  21
  22 extern void die(const char *,struct pt_regs *,long);
  23
  24 /*
  25  * This routine handles page faults.  It determines the address,
  26  * and the problem, and then passes it off to one of the appropriate
  27  * routines.
  28  */
  29 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
  30                                         unsigned long writeaccess,
  31                                         unsigned long address)
  32 {
  33         struct task_struct *tsk;
  34         struct mm_struct *mm;
  35         struct vm_area_struct * vma;
  36         unsigned long page;
  37         int si_code;
  38         siginfo_t info;
  39
  40         trace_hardirqs_on();
  41         local_irq_enable();
  42
  43 #ifdef CONFIG_SH_KGDB
  44         if (kgdb_nofault && kgdb_bus_err_hook)
  45                 kgdb_bus_err_hook();
  46 #endif
  47
  48         tsk = current;
  49         mm = tsk->mm;
  50         si_code = SEGV_MAPERR;
  51
  52         if (unlikely(address >= TASK_SIZE)) {
  53                 /*
  54                  * Synchronize this task's top level page-table
  55                  * with the 'reference' page table.
  56                  *
  57                  * Do _not_ use "tsk" here. We might be inside
  58                  * an interrupt in the middle of a task switch..
  59                  */
  60                 int offset = pgd_index(address);
  61                 pgd_t *pgd, *pgd_k;
  62                 pud_t *pud, *pud_k;
  63                 pmd_t *pmd, *pmd_k;
  64
  65                 pgd = get_TTB() + offset;
  66                 pgd_k = swapper_pg_dir + offset;
  67
  68                 /* This will never happen with the folded page table. */
  69                 if (!pgd_present(*pgd)) {
  70                         if (!pgd_present(*pgd_k))
  71                                 goto bad_area_nosemaphore;
  72                         set_pgd(pgd, *pgd_k);
  73                         return;
  74                 }
  75
  76                 pud = pud_offset(pgd, address);
  77                 pud_k = pud_offset(pgd_k, address);
  78                 if (pud_present(*pud) || !pud_present(*pud_k))
  79                         goto bad_area_nosemaphore;
  80                 set_pud(pud, *pud_k);
  81
  82                 pmd = pmd_offset(pud, address);
  83                 pmd_k = pmd_offset(pud_k, address);
  84                 if (pmd_present(*pmd) || !pmd_present(*pmd_k))
  85                         goto bad_area_nosemaphore;
  86                 set_pmd(pmd, *pmd_k);
  87
  88                 return;
  89         }
  90
  91         /*
  92          * If we're in an interrupt or have no user
  93          * context, we must not take the fault..
  94          */
  95         if (in_atomic() || !mm)
  96                 goto no_context;
  97
  98         down_read(&mm->mmap_sem);
  99
 100         vma = find_vma(mm, address);
 101         if (!vma)
 102                 goto bad_area;
 103         if (vma->vm_start <= address)
 104                 goto good_area;
 105         if (!(vma->vm_flags & VM_GROWSDOWN))
 106                 goto bad_area;
 107         if (expand_stack(vma, address))
 108                 goto bad_area;
 109 /*
 110  * Ok, we have a good vm_area for this memory access, so
 111  * we can handle it..
 112  */
 113 good_area:
 114         si_code = SEGV_ACCERR;
 115         if (writeaccess) {
 116                 if (!(vma->vm_flags & VM_WRITE))
 117                         goto bad_area;
 118         } else {
 119                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 120                         goto bad_area;
 121         }
 122
 123         /*
 124          * If for any reason at all we couldn't handle the fault,
 125          * make sure we exit gracefully rather than endlessly redo
 126          * the fault.
 127          */
 128 survive:
 129         switch (handle_mm_fault(mm, vma, address, writeaccess)) {
 130                 case VM_FAULT_MINOR:
 131                         tsk->min_flt++;
 132                         break;
 133                 case VM_FAULT_MAJOR:
 134                         tsk->maj_flt++;
 135                         break;
 136                 case VM_FAULT_SIGBUS:
 137                         goto do_sigbus;
 138                 case VM_FAULT_OOM:
 139                         goto out_of_memory;
 140                 default:
 141                         BUG();
 142         }
 143
 144         up_read(&mm->mmap_sem);
 145         return;
 146
 147 /*
 148  * Something tried to access memory that isn't in our memory map..
 149  * Fix it, but check if it's kernel or user first..
 150  */
 151 bad_area:
 152         up_read(&mm->mmap_sem);
 153
 154 bad_area_nosemaphore:
 155         if (user_mode(regs)) {
 156                 info.si_signo = SIGSEGV;
 157                 info.si_errno = 0;
 158                 info.si_code = si_code;
 159                 info.si_addr = (void *) address;
 160                 force_sig_info(SIGSEGV, &info, tsk);
 161                 return;
 162         }
 163
 164 no_context:
 165         /* Are we prepared to handle this kernel fault?  */
 166         if (fixup_exception(regs))
 167                 return;
 168
 169 /*
 170  * Oops. The kernel tried to access some bad page. We'll have to
 171  * terminate things with extreme prejudice.
 172  *
 173  */
 174         if (address < PAGE_SIZE)
 175                 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
 176         else
 177                 printk(KERN_ALERT "Unable to handle kernel paging request");
 178         printk(" at virtual address %08lx\n", address);
 179         printk(KERN_ALERT "pc = %08lx\n", regs->pc);
 180         page = (unsigned long)get_TTB();
 181         if (page) {
 182                 page = ((unsigned long *) page)[address >> PGDIR_SHIFT];
 183                 printk(KERN_ALERT "*pde = %08lx\n", page);
 184                 if (page & _PAGE_PRESENT) {
 185                         page &= PAGE_MASK;
 186                         address &= 0x003ff000;
 187                         page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
 188                         printk(KERN_ALERT "*pte = %08lx\n", page);
 189                 }
 190         }
 191         die("Oops", regs, writeaccess);
 192         do_exit(SIGKILL);
 193
 194 /*
 195  * We ran out of memory, or some other thing happened to us that made
 196  * us unable to handle the page fault gracefully.
 197  */
 198 out_of_memory:
 199         up_read(&mm->mmap_sem);
 200         if (is_init(current)) {
 201                 yield();
 202                 down_read(&mm->mmap_sem);
 203                 goto survive;
 204         }
 205         printk("VM: killing process %s\n", tsk->comm);
 206         if (user_mode(regs))
 207                 do_exit(SIGKILL);
 208         goto no_context;
 209
 210 do_sigbus:
 211         up_read(&mm->mmap_sem);
 212
 213         /*
 214          * Send a sigbus, regardless of whether we were in kernel
 215          * or user mode.
 216          */
 217         info.si_signo = SIGBUS;
 218         info.si_errno = 0;
 219         info.si_code = BUS_ADRERR;
 220         info.si_addr = (void *)address;
 221         force_sig_info(SIGBUS, &info, tsk);
 222
 223         /* Kernel mode? Handle exceptions or die */
 224         if (!user_mode(regs))
 225                 goto no_context;
 226 }