arch/openrisc/mm/fault.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * OpenRISC fault.c
   4  *
   5  * Linux architectural port borrowing liberally from similar works of
   6  * others.  All original copyrights apply as per the original source
   7  * declaration.
   8  *
   9  * Modifications for the OpenRISC architecture:
  10  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
  11  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  12  */
  13
  14 #include <linux/mm.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/extable.h>
  17 #include <linux/sched/signal.h>
  18 #include <linux/perf_event.h>
  19
  20 #include <linux/uaccess.h>
  21 #include <asm/siginfo.h>
  22 #include <asm/signal.h>
  23
  24 #define NUM_TLB_ENTRIES 64
  25 #define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))
  26
  27 unsigned long pte_misses;       /* updated by do_page_fault() */
  28 unsigned long pte_errors;       /* updated by do_page_fault() */
  29
  30 /* __PHX__ :: - check the vmalloc_fault in do_page_fault()
  31  *            - also look into include/asm-or32/mmu_context.h
  32  */
  33 volatile pgd_t *current_pgd[NR_CPUS];
  34
  35 extern void die(char *, struct pt_regs *, long);
  36
  37 /*
  38  * This routine handles page faults.  It determines the address,
  39  * and the problem, and then passes it off to one of the appropriate
  40  * routines.
  41  *
  42  * If this routine detects a bad access, it returns 1, otherwise it
  43  * returns 0.
  44  */
  45
  46 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
  47                               unsigned long vector, int write_acc)
  48 {
  49         struct task_struct *tsk;
  50         struct mm_struct *mm;
  51         struct vm_area_struct *vma;
  52         int si_code;
  53         vm_fault_t fault;
  54         unsigned int flags = FAULT_FLAG_DEFAULT;
  55
  56         tsk = current;
  57
  58         /*
  59          * We fault-in kernel-space virtual memory on-demand. The
  60          * 'reference' page table is init_mm.pgd.
  61          *
  62          * NOTE! We MUST NOT take any locks for this case. We may
  63          * be in an interrupt or a critical region, and should
  64          * only copy the information from the master page table,
  65          * nothing more.
  66          *
  67          * NOTE2: This is done so that, when updating the vmalloc
  68          * mappings we don't have to walk all processes pgdirs and
  69          * add the high mappings all at once. Instead we do it as they
  70          * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
  71          * bit set so sometimes the TLB can use a lingering entry.
  72          *
  73          * This verifies that the fault happens in kernel space
  74          * and that the fault was not a protection error.
  75          */
  76
  77         if (address >= VMALLOC_START &&
  78             (vector != 0x300 && vector != 0x400) &&
  79             !user_mode(regs))
  80                 goto vmalloc_fault;
  81
  82         /* If exceptions were enabled, we can reenable them here */
  83         if (user_mode(regs)) {
  84                 /* Exception was in userspace: reenable interrupts */
  85                 local_irq_enable();
  86                 flags |= FAULT_FLAG_USER;
  87         } else {
  88                 /* If exception was in a syscall, then IRQ's may have
  89                  * been enabled or disabled.  If they were enabled,
  90                  * reenable them.
  91                  */
  92                 if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
  93                         local_irq_enable();
  94         }
  95
  96         mm = tsk->mm;
  97         si_code = SEGV_MAPERR;
  98
  99         /*
 100          * If we're in an interrupt or have no user
 101          * context, we must not take the fault..
 102          */
 103
 104         if (in_interrupt() || !mm)
 105                 goto no_context;
 106
 107         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 108
 109 retry:
 110         mmap_read_lock(mm);
 111         vma = find_vma(mm, address);
 112
 113         if (!vma)
 114                 goto bad_area;
 115
 116         if (vma->vm_start <= address)
 117                 goto good_area;
 118
 119         if (!(vma->vm_flags & VM_GROWSDOWN))
 120                 goto bad_area;
 121
 122         if (user_mode(regs)) {
 123                 /*
 124                  * accessing the stack below usp is always a bug.
 125                  * we get page-aligned addresses so we can only check
 126                  * if we're within a page from usp, but that might be
 127                  * enough to catch brutal errors at least.
 128                  */
 129                 if (address + PAGE_SIZE < regs->sp)
 130                         goto bad_area;
 131         }
 132         if (expand_stack(vma, address))
 133                 goto bad_area;
 134
 135         /*
 136          * Ok, we have a good vm_area for this memory access, so
 137          * we can handle it..
 138          */
 139
 140 good_area:
 141         si_code = SEGV_ACCERR;
 142
 143         /* first do some preliminary protection checks */
 144
 145         if (write_acc) {
 146                 if (!(vma->vm_flags & VM_WRITE))
 147                         goto bad_area;
 148                 flags |= FAULT_FLAG_WRITE;
 149         } else {
 150                 /* not present */
 151                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 152                         goto bad_area;
 153         }
 154
 155         /* are we trying to execute nonexecutable area */
 156         if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))
 157                 goto bad_area;
 158
 159         /*
 160          * If for any reason at all we couldn't handle the fault,
 161          * make sure we exit gracefully rather than endlessly redo
 162          * the fault.
 163          */
 164
 165         fault = handle_mm_fault(vma, address, flags, regs);
 166
 167         if (fault_signal_pending(fault, regs))
 168                 return;
 169
 170         if (unlikely(fault & VM_FAULT_ERROR)) {
 171                 if (fault & VM_FAULT_OOM)
 172                         goto out_of_memory;
 173                 else if (fault & VM_FAULT_SIGSEGV)
 174                         goto bad_area;
 175                 else if (fault & VM_FAULT_SIGBUS)
 176                         goto do_sigbus;
 177                 BUG();
 178         }
 179
 180         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 181                 /*RGD modeled on Cris */
 182                 if (fault & VM_FAULT_RETRY) {
 183                         flags |= FAULT_FLAG_TRIED;
 184
 185                          /* No need to mmap_read_unlock(mm) as we would
 186                          * have already released it in __lock_page_or_retry
 187                          * in mm/filemap.c.
 188                          */
 189
 190                         goto retry;
 191                 }
 192         }
 193
 194         mmap_read_unlock(mm);
 195         return;
 196
 197         /*
 198          * Something tried to access memory that isn't in our memory map..
 199          * Fix it, but check if it's kernel or user first..
 200          */
 201
 202 bad_area:
 203         mmap_read_unlock(mm);
 204
 205 bad_area_nosemaphore:
 206
 207         /* User mode accesses just cause a SIGSEGV */
 208
 209         if (user_mode(regs)) {
 210                 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 211                 return;
 212         }
 213
 214 no_context:
 215
 216         /* Are we prepared to handle this kernel fault?
 217          *
 218          * (The kernel has valid exception-points in the source
 219          *  when it acesses user-memory. When it fails in one
 220          *  of those points, we find it in a table and do a jump
 221          *  to some fixup code that loads an appropriate error
 222          *  code)
 223          */
 224
 225         {
 226                 const struct exception_table_entry *entry;
 227
 228                 __asm__ __volatile__("l.nop 42");
 229
 230                 if ((entry = search_exception_tables(regs->pc)) != NULL) {
 231                         /* Adjust the instruction pointer in the stackframe */
 232                         regs->pc = entry->fixup;
 233                         return;
 234                 }
 235         }
 236
 237         /*
 238          * Oops. The kernel tried to access some bad page. We'll have to
 239          * terminate things with extreme prejudice.
 240          */
 241
 242         if ((unsigned long)(address) < PAGE_SIZE)
 243                 printk(KERN_ALERT
 244                        "Unable to handle kernel NULL pointer dereference");
 245         else
 246                 printk(KERN_ALERT "Unable to handle kernel access");
 247         printk(" at virtual address 0x%08lx\n", address);
 248
 249         die("Oops", regs, write_acc);
 250
 251         do_exit(SIGKILL);
 252
 253         /*
 254          * We ran out of memory, or some other thing happened to us that made
 255          * us unable to handle the page fault gracefully.
 256          */
 257
 258 out_of_memory:
 259         __asm__ __volatile__("l.nop 42");
 260         __asm__ __volatile__("l.nop 1");
 261
 262         mmap_read_unlock(mm);
 263         if (!user_mode(regs))
 264                 goto no_context;
 265         pagefault_out_of_memory();
 266         return;
 267
 268 do_sigbus:
 269         mmap_read_unlock(mm);
 270
 271         /*
 272          * Send a sigbus, regardless of whether we were in kernel
 273          * or user mode.
 274          */
 275         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
 276
 277         /* Kernel mode? Handle exceptions or die */
 278         if (!user_mode(regs))
 279                 goto no_context;
 280         return;
 281
 282 vmalloc_fault:
 283         {
 284                 /*
 285                  * Synchronize this task's top level page-table
 286                  * with the 'reference' page table.
 287                  *
 288                  * Use current_pgd instead of tsk->active_mm->pgd
 289                  * since the latter might be unavailable if this
 290                  * code is executed in a misfortunately run irq
 291                  * (like inside schedule() between switch_mm and
 292                  *  switch_to...).
 293                  */
 294
 295                 int offset = pgd_index(address);
 296                 pgd_t *pgd, *pgd_k;
 297                 p4d_t *p4d, *p4d_k;
 298                 pud_t *pud, *pud_k;
 299                 pmd_t *pmd, *pmd_k;
 300                 pte_t *pte_k;
 301
 302 /*
 303                 phx_warn("do_page_fault(): vmalloc_fault will not work, "
 304                          "since current_pgd assign a proper value somewhere\n"
 305                          "anyhow we don't need this at the moment\n");
 306
 307                 phx_mmu("vmalloc_fault");
 308 */
 309                 pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset;
 310                 pgd_k = init_mm.pgd + offset;
 311
 312                 /* Since we're two-level, we don't need to do both
 313                  * set_pgd and set_pmd (they do the same thing). If
 314                  * we go three-level at some point, do the right thing
 315                  * with pgd_present and set_pgd here.
 316                  *
 317                  * Also, since the vmalloc area is global, we don't
 318                  * need to copy individual PTE's, it is enough to
 319                  * copy the pgd pointer into the pte page of the
 320                  * root task. If that is there, we'll find our pte if
 321                  * it exists.
 322                  */
 323
 324                 p4d = p4d_offset(pgd, address);
 325                 p4d_k = p4d_offset(pgd_k, address);
 326                 if (!p4d_present(*p4d_k))
 327                         goto no_context;
 328
 329                 pud = pud_offset(p4d, address);
 330                 pud_k = pud_offset(p4d_k, address);
 331                 if (!pud_present(*pud_k))
 332                         goto no_context;
 333
 334                 pmd = pmd_offset(pud, address);
 335                 pmd_k = pmd_offset(pud_k, address);
 336
 337                 if (!pmd_present(*pmd_k))
 338                         goto bad_area_nosemaphore;
 339
 340                 set_pmd(pmd, *pmd_k);
 341
 342                 /* Make sure the actual PTE exists as well to
 343                  * catch kernel vmalloc-area accesses to non-mapped
 344                  * addresses. If we don't do this, this will just
 345                  * silently loop forever.
 346                  */
 347
 348                 pte_k = pte_offset_kernel(pmd_k, address);
 349                 if (!pte_present(*pte_k))
 350                         goto no_context;
 351
 352                 return;
 353         }
 354 }