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