arch/openrisc/mm/fault.c

   1 /*
   2  * OpenRISC fault.c
   3  *
   4  * Linux architectural port borrowing liberally from similar works of
   5  * others.  All original copyrights apply as per the original source
   6  * declaration.
   7  *
   8  * Modifications for the OpenRISC architecture:
   9  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
  10  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  11  *
  12  *      This program is free software; you can redistribute it and/or
  13  *      modify it under the terms of the GNU General Public License
  14  *      as published by the Free Software Foundation; either version
  15  *      2 of the License, or (at your option) any later version.
  16  */
  17
  18 #include <linux/mm.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/module.h>
  21 #include <linux/sched.h>
  22
  23 #include <asm/uaccess.h>
  24 #include <asm/siginfo.h>
  25 #include <asm/signal.h>
  26
  27 #define NUM_TLB_ENTRIES 64
  28 #define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))
  29
  30 unsigned long pte_misses;       /* updated by do_page_fault() */
  31 unsigned long pte_errors;       /* updated by do_page_fault() */
  32
  33 /* __PHX__ :: - check the vmalloc_fault in do_page_fault()
  34  *            - also look into include/asm-or32/mmu_context.h
  35  */
  36 volatile pgd_t *current_pgd;
  37
  38 extern void die(char *, struct pt_regs *, long);
  39
  40 /*
  41  * This routine handles page faults.  It determines the address,
  42  * and the problem, and then passes it off to one of the appropriate
  43  * routines.
  44  *
  45  * If this routine detects a bad access, it returns 1, otherwise it
  46  * returns 0.
  47  */
  48
  49 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
  50                               unsigned long vector, int write_acc)
  51 {
  52         struct task_struct *tsk;
  53         struct mm_struct *mm;
  54         struct vm_area_struct *vma;
  55         siginfo_t info;
  56         int fault;
  57         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  58
  59         tsk = current;
  60
  61         /*
  62          * We fault-in kernel-space virtual memory on-demand. The
  63          * 'reference' page table is init_mm.pgd.
  64          *
  65          * NOTE! We MUST NOT take any locks for this case. We may
  66          * be in an interrupt or a critical region, and should
  67          * only copy the information from the master page table,
  68          * nothing more.
  69          *
  70          * NOTE2: This is done so that, when updating the vmalloc
  71          * mappings we don't have to walk all processes pgdirs and
  72          * add the high mappings all at once. Instead we do it as they
  73          * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
  74          * bit set so sometimes the TLB can use a lingering entry.
  75          *
  76          * This verifies that the fault happens in kernel space
  77          * and that the fault was not a protection error.
  78          */
  79
  80         if (address >= VMALLOC_START &&
  81             (vector != 0x300 && vector != 0x400) &&
  82             !user_mode(regs))
  83                 goto vmalloc_fault;
  84
  85         /* If exceptions were enabled, we can reenable them here */
  86         if (user_mode(regs)) {
  87                 /* Exception was in userspace: reenable interrupts */
  88                 local_irq_enable();
  89                 flags |= FAULT_FLAG_USER;
  90         } else {
  91                 /* If exception was in a syscall, then IRQ's may have
  92                  * been enabled or disabled.  If they were enabled,
  93                  * reenable them.
  94                  */
  95                 if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
  96                         local_irq_enable();
  97         }
  98
  99         mm = tsk->mm;
 100         info.si_code = SEGV_MAPERR;
 101
 102         /*
 103          * If we're in an interrupt or have no user
 104          * context, we must not take the fault..
 105          */
 106
 107         if (in_interrupt() || !mm)
 108                 goto no_context;
 109
 110 retry:
 111         down_read(&mm->mmap_sem);
 112         vma = find_vma(mm, address);
 113
 114         if (!vma)
 115                 goto bad_area;
 116
 117         if (vma->vm_start <= address)
 118                 goto good_area;
 119
 120         if (!(vma->vm_flags & VM_GROWSDOWN))
 121                 goto bad_area;
 122
 123         if (user_mode(regs)) {
 124                 /*
 125                  * accessing the stack below usp is always a bug.
 126                  * we get page-aligned addresses so we can only check
 127                  * if we're within a page from usp, but that might be
 128                  * enough to catch brutal errors at least.
 129                  */
 130                 if (address + PAGE_SIZE < regs->sp)
 131                         goto bad_area;
 132         }
 133         if (expand_stack(vma, address))
 134                 goto bad_area;
 135
 136         /*
 137          * Ok, we have a good vm_area for this memory access, so
 138          * we can handle it..
 139          */
 140
 141 good_area:
 142         info.si_code = SEGV_ACCERR;
 143
 144         /* first do some preliminary protection checks */
 145
 146         if (write_acc) {
 147                 if (!(vma->vm_flags & VM_WRITE))
 148                         goto bad_area;
 149                 flags |= FAULT_FLAG_WRITE;
 150         } else {
 151                 /* not present */
 152                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 153                         goto bad_area;
 154         }
 155
 156         /* are we trying to execute nonexecutable area */
 157         if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))
 158                 goto bad_area;
 159
 160         /*
 161          * If for any reason at all we couldn't handle the fault,
 162          * make sure we exit gracefully rather than endlessly redo
 163          * the fault.
 164          */
 165
 166         fault = handle_mm_fault(mm, vma, address, flags);
 167
 168         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 169                 return;
 170
 171         if (unlikely(fault & VM_FAULT_ERROR)) {
 172                 if (fault & VM_FAULT_OOM)
 173                         goto out_of_memory;
 174                 else if (fault & VM_FAULT_SIGSEGV)
 175                         goto bad_area;
 176                 else if (fault & VM_FAULT_SIGBUS)
 177                         goto do_sigbus;
 178                 BUG();
 179         }
 180
 181         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 182                 /*RGD modeled on Cris */
 183                 if (fault & VM_FAULT_MAJOR)
 184                         tsk->maj_flt++;
 185                 else
 186                         tsk->min_flt++;
 187                 if (fault & VM_FAULT_RETRY) {
 188                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 189                         flags |= FAULT_FLAG_TRIED;
 190
 191                          /* No need to up_read(&mm->mmap_sem) as we would
 192                          * have already released it in __lock_page_or_retry
 193                          * in mm/filemap.c.
 194                          */
 195
 196                         goto retry;
 197                 }
 198         }
 199
 200         up_read(&mm->mmap_sem);
 201         return;
 202
 203         /*
 204          * Something tried to access memory that isn't in our memory map..
 205          * Fix it, but check if it's kernel or user first..
 206          */
 207
 208 bad_area:
 209         up_read(&mm->mmap_sem);
 210
 211 bad_area_nosemaphore:
 212
 213         /* User mode accesses just cause a SIGSEGV */
 214
 215         if (user_mode(regs)) {
 216                 info.si_signo = SIGSEGV;
 217                 info.si_errno = 0;
 218                 /* info.si_code has been set above */
 219                 info.si_addr = (void *)address;
 220                 force_sig_info(SIGSEGV, &info, tsk);
 221                 return;
 222         }
 223
 224 no_context:
 225
 226         /* Are we prepared to handle this kernel fault?
 227          *
 228          * (The kernel has valid exception-points in the source
 229          *  when it acesses user-memory. When it fails in one
 230          *  of those points, we find it in a table and do a jump
 231          *  to some fixup code that loads an appropriate error
 232          *  code)
 233          */
 234
 235         {
 236                 const struct exception_table_entry *entry;
 237
 238                 __asm__ __volatile__("l.nop 42");
 239
 240                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
 241                         /* Adjust the instruction pointer in the stackframe */
 242                         regs->pc = entry->fixup;
 243                         return;
 244                 }
 245         }
 246
 247         /*
 248          * Oops. The kernel tried to access some bad page. We'll have to
 249          * terminate things with extreme prejudice.
 250          */
 251
 252         if ((unsigned long)(address) < PAGE_SIZE)
 253                 printk(KERN_ALERT
 254                        "Unable to handle kernel NULL pointer dereference");
 255         else
 256                 printk(KERN_ALERT "Unable to handle kernel access");
 257         printk(" at virtual address 0x%08lx\n", address);
 258
 259         die("Oops", regs, write_acc);
 260
 261         do_exit(SIGKILL);
 262
 263         /*
 264          * We ran out of memory, or some other thing happened to us that made
 265          * us unable to handle the page fault gracefully.
 266          */
 267
 268 out_of_memory:
 269         __asm__ __volatile__("l.nop 42");
 270         __asm__ __volatile__("l.nop 1");
 271
 272         up_read(&mm->mmap_sem);
 273         if (!user_mode(regs))
 274                 goto no_context;
 275         pagefault_out_of_memory();
 276         return;
 277
 278 do_sigbus:
 279         up_read(&mm->mmap_sem);
 280
 281         /*
 282          * Send a sigbus, regardless of whether we were in kernel
 283          * or user mode.
 284          */
 285         info.si_signo = SIGBUS;
 286         info.si_errno = 0;
 287         info.si_code = BUS_ADRERR;
 288         info.si_addr = (void *)address;
 289         force_sig_info(SIGBUS, &info, tsk);
 290
 291         /* Kernel mode? Handle exceptions or die */
 292         if (!user_mode(regs))
 293                 goto no_context;
 294         return;
 295
 296 vmalloc_fault:
 297         {
 298                 /*
 299                  * Synchronize this task's top level page-table
 300                  * with the 'reference' page table.
 301                  *
 302                  * Use current_pgd instead of tsk->active_mm->pgd
 303                  * since the latter might be unavailable if this
 304                  * code is executed in a misfortunately run irq
 305                  * (like inside schedule() between switch_mm and
 306                  *  switch_to...).
 307                  */
 308
 309                 int offset = pgd_index(address);
 310                 pgd_t *pgd, *pgd_k;
 311                 pud_t *pud, *pud_k;
 312                 pmd_t *pmd, *pmd_k;
 313                 pte_t *pte_k;
 314
 315 /*
 316                 phx_warn("do_page_fault(): vmalloc_fault will not work, "
 317                          "since current_pgd assign a proper value somewhere\n"
 318                          "anyhow we don't need this at the moment\n");
 319
 320                 phx_mmu("vmalloc_fault");
 321 */
 322                 pgd = (pgd_t *)current_pgd + offset;
 323                 pgd_k = init_mm.pgd + offset;
 324
 325                 /* Since we're two-level, we don't need to do both
 326                  * set_pgd and set_pmd (they do the same thing). If
 327                  * we go three-level at some point, do the right thing
 328                  * with pgd_present and set_pgd here.
 329                  *
 330                  * Also, since the vmalloc area is global, we don't
 331                  * need to copy individual PTE's, it is enough to
 332                  * copy the pgd pointer into the pte page of the
 333                  * root task. If that is there, we'll find our pte if
 334                  * it exists.
 335                  */
 336
 337                 pud = pud_offset(pgd, address);
 338                 pud_k = pud_offset(pgd_k, address);
 339                 if (!pud_present(*pud_k))
 340                         goto no_context;
 341
 342                 pmd = pmd_offset(pud, address);
 343                 pmd_k = pmd_offset(pud_k, address);
 344
 345                 if (!pmd_present(*pmd_k))
 346                         goto bad_area_nosemaphore;
 347
 348                 set_pmd(pmd, *pmd_k);
 349
 350                 /* Make sure the actual PTE exists as well to
 351                  * catch kernel vmalloc-area accesses to non-mapped
 352                  * addresses. If we don't do this, this will just
 353                  * silently loop forever.
 354                  */
 355
 356                 pte_k = pte_offset_kernel(pmd_k, address);
 357                 if (!pte_present(*pte_k))
 358                         goto no_context;
 359
 360                 return;
 361         }
 362 }