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 - 2007  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/tlbflush.h>
  21 #include <asm/kgdb.h>
  22
  23 /*
  24  * This routine handles page faults.  It determines the address,
  25  * and the problem, and then passes it off to one of the appropriate
  26  * routines.
  27  */
  28 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
  29                                         unsigned long writeaccess,
  30                                         unsigned long address)
  31 {
  32         struct task_struct *tsk;
  33         struct mm_struct *mm;
  34         struct vm_area_struct * vma;
  35         int si_code;
  36         int fault;
  37         siginfo_t info;
  38
  39         trace_hardirqs_on();
  40         local_irq_enable();
  41
  42 #ifdef CONFIG_SH_KGDB
  43         if (kgdb_nofault && kgdb_bus_err_hook)
  44                 kgdb_bus_err_hook();
  45 #endif
  46
  47         tsk = current;
  48         mm = tsk->mm;
  49         si_code = SEGV_MAPERR;
  50
  51         if (unlikely(address >= TASK_SIZE)) {
  52                 /*
  53                  * Synchronize this task's top level page-table
  54                  * with the 'reference' page table.
  55                  *
  56                  * Do _not_ use "tsk" here. We might be inside
  57                  * an interrupt in the middle of a task switch..
  58                  */
  59                 int offset = pgd_index(address);
  60                 pgd_t *pgd, *pgd_k;
  61                 pud_t *pud, *pud_k;
  62                 pmd_t *pmd, *pmd_k;
  63
  64                 pgd = get_TTB() + offset;
  65                 pgd_k = swapper_pg_dir + offset;
  66
  67                 /* This will never happen with the folded page table. */
  68                 if (!pgd_present(*pgd)) {
  69                         if (!pgd_present(*pgd_k))
  70                                 goto bad_area_nosemaphore;
  71                         set_pgd(pgd, *pgd_k);
  72                         return;
  73                 }
  74
  75                 pud = pud_offset(pgd, address);
  76                 pud_k = pud_offset(pgd_k, address);
  77                 if (pud_present(*pud) || !pud_present(*pud_k))
  78                         goto bad_area_nosemaphore;
  79                 set_pud(pud, *pud_k);
  80
  81                 pmd = pmd_offset(pud, address);
  82                 pmd_k = pmd_offset(pud_k, address);
  83                 if (pmd_present(*pmd) || !pmd_present(*pmd_k))
  84                         goto bad_area_nosemaphore;
  85                 set_pmd(pmd, *pmd_k);
  86
  87                 return;
  88         }
  89
  90         /*
  91          * If we're in an interrupt or have no user
  92          * context, we must not take the fault..
  93          */
  94         if (in_atomic() || !mm)
  95                 goto no_context;
  96
  97         down_read(&mm->mmap_sem);
  98
  99         vma = find_vma(mm, address);
 100         if (!vma)
 101                 goto bad_area;
 102         if (vma->vm_start <= address)
 103                 goto good_area;
 104         if (!(vma->vm_flags & VM_GROWSDOWN))
 105                 goto bad_area;
 106         if (expand_stack(vma, address))
 107                 goto bad_area;
 108 /*
 109  * Ok, we have a good vm_area for this memory access, so
 110  * we can handle it..
 111  */
 112 good_area:
 113         si_code = SEGV_ACCERR;
 114         if (writeaccess) {
 115                 if (!(vma->vm_flags & VM_WRITE))
 116                         goto bad_area;
 117         } else {
 118                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 119                         goto bad_area;
 120         }
 121
 122         /*
 123          * If for any reason at all we couldn't handle the fault,
 124          * make sure we exit gracefully rather than endlessly redo
 125          * the fault.
 126          */
 127 survive:
 128         fault = handle_mm_fault(mm, vma, address, writeaccess);
 129         if (unlikely(fault & VM_FAULT_ERROR)) {
 130                 if (fault & VM_FAULT_OOM)
 131                         goto out_of_memory;
 132                 else if (fault & VM_FAULT_SIGBUS)
 133                         goto do_sigbus;
 134                 BUG();
 135         }
 136         if (fault & VM_FAULT_MAJOR)
 137                 tsk->maj_flt++;
 138         else
 139                 tsk->min_flt++;
 140
 141         up_read(&mm->mmap_sem);
 142         return;
 143
 144 /*
 145  * Something tried to access memory that isn't in our memory map..
 146  * Fix it, but check if it's kernel or user first..
 147  */
 148 bad_area:
 149         up_read(&mm->mmap_sem);
 150
 151 bad_area_nosemaphore:
 152         if (user_mode(regs)) {
 153                 info.si_signo = SIGSEGV;
 154                 info.si_errno = 0;
 155                 info.si_code = si_code;
 156                 info.si_addr = (void *) address;
 157                 force_sig_info(SIGSEGV, &info, tsk);
 158                 return;
 159         }
 160
 161 no_context:
 162         /* Are we prepared to handle this kernel fault?  */
 163         if (fixup_exception(regs))
 164                 return;
 165
 166 /*
 167  * Oops. The kernel tried to access some bad page. We'll have to
 168  * terminate things with extreme prejudice.
 169  *
 170  */
 171
 172         bust_spinlocks(1);
 173
 174         if (oops_may_print()) {
 175                 __typeof__(pte_val(__pte(0))) page;
 176
 177                 if (address < PAGE_SIZE)
 178                         printk(KERN_ALERT "Unable to handle kernel NULL "
 179                                           "pointer dereference");
 180                 else
 181                         printk(KERN_ALERT "Unable to handle kernel paging "
 182                                           "request");
 183                 printk(" at virtual address %08lx\n", address);
 184                 printk(KERN_ALERT "pc = %08lx\n", regs->pc);
 185                 page = (unsigned long)get_TTB();
 186                 if (page) {
 187                         page = ((__typeof__(page) *)page)[address >> PGDIR_SHIFT];
 188                         printk(KERN_ALERT "*pde = %08lx\n", page);
 189                         if (page & _PAGE_PRESENT) {
 190                                 page &= PAGE_MASK;
 191                                 address &= 0x003ff000;
 192                                 page = ((__typeof__(page) *)
 193                                                 __va(page))[address >>
 194                                                             PAGE_SHIFT];
 195                                 printk(KERN_ALERT "*pte = %08lx\n", page);
 196                         }
 197                 }
 198         }
 199
 200         die("Oops", regs, writeaccess);
 201         bust_spinlocks(0);
 202         do_exit(SIGKILL);
 203
 204 /*
 205  * We ran out of memory, or some other thing happened to us that made
 206  * us unable to handle the page fault gracefully.
 207  */
 208 out_of_memory:
 209         up_read(&mm->mmap_sem);
 210         if (is_init(current)) {
 211                 yield();
 212                 down_read(&mm->mmap_sem);
 213                 goto survive;
 214         }
 215         printk("VM: killing process %s\n", tsk->comm);
 216         if (user_mode(regs))
 217                 do_exit(SIGKILL);
 218         goto no_context;
 219
 220 do_sigbus:
 221         up_read(&mm->mmap_sem);
 222
 223         /*
 224          * Send a sigbus, regardless of whether we were in kernel
 225          * or user mode.
 226          */
 227         info.si_signo = SIGBUS;
 228         info.si_errno = 0;
 229         info.si_code = BUS_ADRERR;
 230         info.si_addr = (void *)address;
 231         force_sig_info(SIGBUS, &info, tsk);
 232
 233         /* Kernel mode? Handle exceptions or die */
 234         if (!user_mode(regs))
 235                 goto no_context;
 236 }
 237
 238 #ifdef CONFIG_SH_STORE_QUEUES
 239 /*
 240  * This is a special case for the SH-4 store queues, as pages for this
 241  * space still need to be faulted in before it's possible to flush the
 242  * store queue cache for writeout to the remapped region.
 243  */
 244 #define P3_ADDR_MAX             (P4SEG_STORE_QUE + 0x04000000)
 245 #else
 246 #define P3_ADDR_MAX             P4SEG
 247 #endif
 248
 249 /*
 250  * Called with interrupts disabled.
 251  */
 252 asmlinkage int __kprobes __do_page_fault(struct pt_regs *regs,
 253                                          unsigned long writeaccess,
 254                                          unsigned long address)
 255 {
 256         pgd_t *pgd;
 257         pud_t *pud;
 258         pmd_t *pmd;
 259         pte_t *pte;
 260         pte_t entry;
 261         struct mm_struct *mm = current->mm;
 262         spinlock_t *ptl = NULL;
 263         int ret = 1;
 264
 265 #ifdef CONFIG_SH_KGDB
 266         if (kgdb_nofault && kgdb_bus_err_hook)
 267                 kgdb_bus_err_hook();
 268 #endif
 269
 270         /*
 271          * We don't take page faults for P1, P2, and parts of P4, these
 272          * are always mapped, whether it be due to legacy behaviour in
 273          * 29-bit mode, or due to PMB configuration in 32-bit mode.
 274          */
 275         if (address >= P3SEG && address < P3_ADDR_MAX) {
 276                 pgd = pgd_offset_k(address);
 277                 mm = NULL;
 278         } else {
 279                 if (unlikely(address >= TASK_SIZE || !mm))
 280                         return 1;
 281
 282                 pgd = pgd_offset(mm, address);
 283         }
 284
 285         pud = pud_offset(pgd, address);
 286         if (pud_none_or_clear_bad(pud))
 287                 return 1;
 288         pmd = pmd_offset(pud, address);
 289         if (pmd_none_or_clear_bad(pmd))
 290                 return 1;
 291
 292         if (mm)
 293                 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
 294         else
 295                 pte = pte_offset_kernel(pmd, address);
 296
 297         entry = *pte;
 298         if (unlikely(pte_none(entry) || pte_not_present(entry)))
 299                 goto unlock;
 300         if (unlikely(writeaccess && !pte_write(entry)))
 301                 goto unlock;
 302
 303         if (writeaccess)
 304                 entry = pte_mkdirty(entry);
 305         entry = pte_mkyoung(entry);
 306
 307 #ifdef CONFIG_CPU_SH4
 308         /*
 309          * ITLB is not affected by "ldtlb" instruction.
 310          * So, we need to flush the entry by ourselves.
 311          */
 312         local_flush_tlb_one(get_asid(), address & PAGE_MASK);
 313 #endif
 314
 315         set_pte(pte, entry);
 316         update_mmu_cache(NULL, address, entry);
 317         ret = 0;
 318 unlock:
 319         if (mm)
 320                 pte_unmap_unlock(pte, ptl);
 321         return ret;
 322 }