arch/unicore32/mm/fault.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/arch/unicore32/mm/fault.c
   4  *
   5  * Code specific to PKUnity SoC and UniCore ISA
   6  *
   7  * Copyright (C) 2001-2010 GUAN Xue-tao
   8  */
   9 #include <linux/extable.h>
  10 #include <linux/signal.h>
  11 #include <linux/mm.h>
  12 #include <linux/hardirq.h>
  13 #include <linux/init.h>
  14 #include <linux/kprobes.h>
  15 #include <linux/uaccess.h>
  16 #include <linux/page-flags.h>
  17 #include <linux/sched/signal.h>
  18 #include <linux/io.h>
  19
  20 #include <asm/pgtable.h>
  21 #include <asm/tlbflush.h>
  22
  23 /*
  24  * Fault status register encodings.  We steal bit 31 for our own purposes.
  25  */
  26 #define FSR_LNX_PF              (1 << 31)
  27
  28 static inline int fsr_fs(unsigned int fsr)
  29 {
  30         /* xyabcde will be abcde+xy */
  31         return (fsr & 31) + ((fsr & (3 << 5)) >> 5);
  32 }
  33
  34 /*
  35  * This is useful to dump out the page tables associated with
  36  * 'addr' in mm 'mm'.
  37  */
  38 void show_pte(struct mm_struct *mm, unsigned long addr)
  39 {
  40         pgd_t *pgd;
  41
  42         if (!mm)
  43                 mm = &init_mm;
  44
  45         printk(KERN_ALERT "pgd = %p\n", mm->pgd);
  46         pgd = pgd_offset(mm, addr);
  47         printk(KERN_ALERT "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
  48
  49         do {
  50                 pmd_t *pmd;
  51                 pte_t *pte;
  52
  53                 if (pgd_none(*pgd))
  54                         break;
  55
  56                 if (pgd_bad(*pgd)) {
  57                         printk("(bad)");
  58                         break;
  59                 }
  60
  61                 pmd = pmd_offset((pud_t *) pgd, addr);
  62                 if (PTRS_PER_PMD != 1)
  63                         printk(", *pmd=%08lx", pmd_val(*pmd));
  64
  65                 if (pmd_none(*pmd))
  66                         break;
  67
  68                 if (pmd_bad(*pmd)) {
  69                         printk("(bad)");
  70                         break;
  71                 }
  72
  73                 /* We must not map this if we have highmem enabled */
  74                 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
  75                         break;
  76
  77                 pte = pte_offset_map(pmd, addr);
  78                 printk(", *pte=%08lx", pte_val(*pte));
  79                 pte_unmap(pte);
  80         } while (0);
  81
  82         printk("\n");
  83 }
  84
  85 /*
  86  * Oops.  The kernel tried to access some page that wasn't present.
  87  */
  88 static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr,
  89                 unsigned int fsr, struct pt_regs *regs)
  90 {
  91         /*
  92          * Are we prepared to handle this kernel fault?
  93          */
  94         if (fixup_exception(regs))
  95                 return;
  96
  97         /*
  98          * No handler, we'll have to terminate things with extreme prejudice.
  99          */
 100         bust_spinlocks(1);
 101         printk(KERN_ALERT
 102                "Unable to handle kernel %s at virtual address %08lx\n",
 103                (addr < PAGE_SIZE) ? "NULL pointer dereference" :
 104                "paging request", addr);
 105
 106         show_pte(mm, addr);
 107         die("Oops", regs, fsr);
 108         bust_spinlocks(0);
 109         do_exit(SIGKILL);
 110 }
 111
 112 /*
 113  * Something tried to access memory that isn't in our memory map..
 114  * User mode accesses just cause a SIGSEGV
 115  */
 116 static void __do_user_fault(unsigned long addr, unsigned int fsr,
 117                             unsigned int sig, int code, struct pt_regs *regs)
 118 {
 119         struct task_struct *tsk = current;
 120
 121         tsk->thread.address = addr;
 122         tsk->thread.error_code = fsr;
 123         tsk->thread.trap_no = 14;
 124         force_sig_fault(sig, code, (void __user *)addr);
 125 }
 126
 127 void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 128 {
 129         struct task_struct *tsk = current;
 130         struct mm_struct *mm = tsk->active_mm;
 131
 132         /*
 133          * If we are in kernel mode at this point, we
 134          * have no context to handle this fault with.
 135          */
 136         if (user_mode(regs))
 137                 __do_user_fault(addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
 138         else
 139                 __do_kernel_fault(mm, addr, fsr, regs);
 140 }
 141
 142 #define VM_FAULT_BADMAP         0x010000
 143 #define VM_FAULT_BADACCESS      0x020000
 144
 145 /*
 146  * Check that the permissions on the VMA allow for the fault which occurred.
 147  * If we encountered a write fault, we must have write permission, otherwise
 148  * we allow any permission.
 149  */
 150 static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 151 {
 152         unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
 153
 154         if (!(fsr ^ 0x12))      /* write? */
 155                 mask = VM_WRITE;
 156         if (fsr & FSR_LNX_PF)
 157                 mask = VM_EXEC;
 158
 159         return vma->vm_flags & mask ? false : true;
 160 }
 161
 162 static vm_fault_t __do_pf(struct mm_struct *mm, unsigned long addr,
 163                 unsigned int fsr, unsigned int flags, struct task_struct *tsk)
 164 {
 165         struct vm_area_struct *vma;
 166         vm_fault_t fault;
 167
 168         vma = find_vma(mm, addr);
 169         fault = VM_FAULT_BADMAP;
 170         if (unlikely(!vma))
 171                 goto out;
 172         if (unlikely(vma->vm_start > addr))
 173                 goto check_stack;
 174
 175         /*
 176          * Ok, we have a good vm_area for this
 177          * memory access, so we can handle it.
 178          */
 179 good_area:
 180         if (access_error(fsr, vma)) {
 181                 fault = VM_FAULT_BADACCESS;
 182                 goto out;
 183         }
 184
 185         /*
 186          * If for any reason at all we couldn't handle the fault, make
 187          * sure we exit gracefully rather than endlessly redo the fault.
 188          */
 189         fault = handle_mm_fault(vma, addr & PAGE_MASK, flags);
 190         return fault;
 191
 192 check_stack:
 193         if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 194                 goto good_area;
 195 out:
 196         return fault;
 197 }
 198
 199 static int do_pf(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 200 {
 201         struct task_struct *tsk;
 202         struct mm_struct *mm;
 203         int sig, code;
 204         vm_fault_t fault;
 205         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 206
 207         tsk = current;
 208         mm = tsk->mm;
 209
 210         /*
 211          * If we're in an interrupt or have no user
 212          * context, we must not take the fault..
 213          */
 214         if (faulthandler_disabled() || !mm)
 215                 goto no_context;
 216
 217         if (user_mode(regs))
 218                 flags |= FAULT_FLAG_USER;
 219         if (!(fsr ^ 0x12))
 220                 flags |= FAULT_FLAG_WRITE;
 221
 222         /*
 223          * As per x86, we may deadlock here.  However, since the kernel only
 224          * validly references user space from well defined areas of the code,
 225          * we can bug out early if this is from code which shouldn't.
 226          */
 227         if (!down_read_trylock(&mm->mmap_sem)) {
 228                 if (!user_mode(regs)
 229                     && !search_exception_tables(regs->UCreg_pc))
 230                         goto no_context;
 231 retry:
 232                 down_read(&mm->mmap_sem);
 233         } else {
 234                 /*
 235                  * The above down_read_trylock() might have succeeded in
 236                  * which case, we'll have missed the might_sleep() from
 237                  * down_read()
 238                  */
 239                 might_sleep();
 240 #ifdef CONFIG_DEBUG_VM
 241                 if (!user_mode(regs) &&
 242                     !search_exception_tables(regs->UCreg_pc))
 243                         goto no_context;
 244 #endif
 245         }
 246
 247         fault = __do_pf(mm, addr, fsr, flags, tsk);
 248
 249         /* If we need to retry but a fatal signal is pending, handle the
 250          * signal first. We do not need to release the mmap_sem because
 251          * it would already be released in __lock_page_or_retry in
 252          * mm/filemap.c. */
 253         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 254                 return 0;
 255
 256         if (!(fault & VM_FAULT_ERROR) && (flags & FAULT_FLAG_ALLOW_RETRY)) {
 257                 if (fault & VM_FAULT_MAJOR)
 258                         tsk->maj_flt++;
 259                 else
 260                         tsk->min_flt++;
 261                 if (fault & VM_FAULT_RETRY) {
 262                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 263                         * of starvation. */
 264                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 265                         goto retry;
 266                 }
 267         }
 268
 269         up_read(&mm->mmap_sem);
 270
 271         /*
 272          * Handle the "normal" case first - VM_FAULT_MAJOR
 273          */
 274         if (likely(!(fault &
 275                (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
 276                 return 0;
 277
 278         /*
 279          * If we are in kernel mode at this point, we
 280          * have no context to handle this fault with.
 281          */
 282         if (!user_mode(regs))
 283                 goto no_context;
 284
 285         if (fault & VM_FAULT_OOM) {
 286                 /*
 287                  * We ran out of memory, call the OOM killer, and return to
 288                  * userspace (which will retry the fault, or kill us if we
 289                  * got oom-killed)
 290                  */
 291                 pagefault_out_of_memory();
 292                 return 0;
 293         }
 294
 295         if (fault & VM_FAULT_SIGBUS) {
 296                 /*
 297                  * We had some memory, but were unable to
 298                  * successfully fix up this page fault.
 299                  */
 300                 sig = SIGBUS;
 301                 code = BUS_ADRERR;
 302         } else {
 303                 /*
 304                  * Something tried to access memory that
 305                  * isn't in our memory map..
 306                  */
 307                 sig = SIGSEGV;
 308                 code = fault == VM_FAULT_BADACCESS ? SEGV_ACCERR : SEGV_MAPERR;
 309         }
 310
 311         __do_user_fault(addr, fsr, sig, code, regs);
 312         return 0;
 313
 314 no_context:
 315         __do_kernel_fault(mm, addr, fsr, regs);
 316         return 0;
 317 }
 318
 319 /*
 320  * First Level Translation Fault Handler
 321  *
 322  * We enter here because the first level page table doesn't contain
 323  * a valid entry for the address.
 324  *
 325  * If the address is in kernel space (>= TASK_SIZE), then we are
 326  * probably faulting in the vmalloc() area.
 327  *
 328  * If the init_task's first level page tables contains the relevant
 329  * entry, we copy the it to this task.  If not, we send the process
 330  * a signal, fixup the exception, or oops the kernel.
 331  *
 332  * NOTE! We MUST NOT take any locks for this case. We may be in an
 333  * interrupt or a critical region, and should only copy the information
 334  * from the master page table, nothing more.
 335  */
 336 static int do_ifault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 337 {
 338         unsigned int index;
 339         pgd_t *pgd, *pgd_k;
 340         pmd_t *pmd, *pmd_k;
 341
 342         if (addr < TASK_SIZE)
 343                 return do_pf(addr, fsr, regs);
 344
 345         if (user_mode(regs))
 346                 goto bad_area;
 347
 348         index = pgd_index(addr);
 349
 350         pgd = cpu_get_pgd() + index;
 351         pgd_k = init_mm.pgd + index;
 352
 353         if (pgd_none(*pgd_k))
 354                 goto bad_area;
 355
 356         pmd_k = pmd_offset((pud_t *) pgd_k, addr);
 357         pmd = pmd_offset((pud_t *) pgd, addr);
 358
 359         if (pmd_none(*pmd_k))
 360                 goto bad_area;
 361
 362         set_pmd(pmd, *pmd_k);
 363         flush_pmd_entry(pmd);
 364         return 0;
 365
 366 bad_area:
 367         do_bad_area(addr, fsr, regs);
 368         return 0;
 369 }
 370
 371 /*
 372  * This abort handler always returns "fault".
 373  */
 374 static int do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 375 {
 376         return 1;
 377 }
 378
 379 static int do_good(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 380 {
 381         unsigned int res1, res2;
 382
 383         printk("dabt exception but no error!\n");
 384
 385         __asm__ __volatile__(
 386                         "mff %0,f0\n"
 387                         "mff %1,f1\n"
 388                         : "=r"(res1), "=r"(res2)
 389                         :
 390                         : "memory");
 391
 392         printk(KERN_EMERG "r0 :%08x  r1 :%08x\n", res1, res2);
 393         panic("shut up\n");
 394         return 0;
 395 }
 396
 397 static struct fsr_info {
 398         int (*fn) (unsigned long addr, unsigned int fsr, struct pt_regs *regs);
 399         int sig;
 400         int code;
 401         const char *name;
 402 } fsr_info[] = {
 403         /*
 404          * The following are the standard Unicore-I and UniCore-II aborts.
 405          */
 406         { do_good,      SIGBUS,  0,             "no error"              },
 407         { do_bad,       SIGBUS,  BUS_ADRALN,    "alignment exception"   },
 408         { do_bad,       SIGBUS,  BUS_OBJERR,    "external exception"    },
 409         { do_bad,       SIGBUS,  0,             "burst operation"       },
 410         { do_bad,       SIGBUS,  0,             "unknown 00100"         },
 411         { do_ifault,    SIGSEGV, SEGV_MAPERR,   "2nd level pt non-exist"},
 412         { do_bad,       SIGBUS,  0,             "2nd lvl large pt non-exist" },
 413         { do_bad,       SIGBUS,  0,             "invalid pte"           },
 414         { do_pf,        SIGSEGV, SEGV_MAPERR,   "page miss"             },
 415         { do_bad,       SIGBUS,  0,             "middle page miss"      },
 416         { do_bad,       SIGBUS,  0,             "large page miss"       },
 417         { do_pf,        SIGSEGV, SEGV_MAPERR,   "super page (section) miss" },
 418         { do_bad,       SIGBUS,  0,             "unknown 01100"         },
 419         { do_bad,       SIGBUS,  0,             "unknown 01101"         },
 420         { do_bad,       SIGBUS,  0,             "unknown 01110"         },
 421         { do_bad,       SIGBUS,  0,             "unknown 01111"         },
 422         { do_bad,       SIGBUS,  0,             "addr: up 3G or IO"     },
 423         { do_pf,        SIGSEGV, SEGV_ACCERR,   "read unreadable addr"  },
 424         { do_pf,        SIGSEGV, SEGV_ACCERR,   "write unwriteable addr"},
 425         { do_pf,        SIGSEGV, SEGV_ACCERR,   "exec unexecutable addr"},
 426         { do_bad,       SIGBUS,  0,             "unknown 10100"         },
 427         { do_bad,       SIGBUS,  0,             "unknown 10101"         },
 428         { do_bad,       SIGBUS,  0,             "unknown 10110"         },
 429         { do_bad,       SIGBUS,  0,             "unknown 10111"         },
 430         { do_bad,       SIGBUS,  0,             "unknown 11000"         },
 431         { do_bad,       SIGBUS,  0,             "unknown 11001"         },
 432         { do_bad,       SIGBUS,  0,             "unknown 11010"         },
 433         { do_bad,       SIGBUS,  0,             "unknown 11011"         },
 434         { do_bad,       SIGBUS,  0,             "unknown 11100"         },
 435         { do_bad,       SIGBUS,  0,             "unknown 11101"         },
 436         { do_bad,       SIGBUS,  0,             "unknown 11110"         },
 437         { do_bad,       SIGBUS,  0,             "unknown 11111"         }
 438 };
 439
 440 void __init hook_fault_code(int nr,
 441                 int (*fn) (unsigned long, unsigned int, struct pt_regs *),
 442                 int sig, int code, const char *name)
 443 {
 444         if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
 445                 BUG();
 446
 447         fsr_info[nr].fn   = fn;
 448         fsr_info[nr].sig  = sig;
 449         fsr_info[nr].code = code;
 450         fsr_info[nr].name = name;
 451 }
 452
 453 /*
 454  * Dispatch a data abort to the relevant handler.
 455  */
 456 asmlinkage void do_DataAbort(unsigned long addr, unsigned int fsr,
 457                         struct pt_regs *regs)
 458 {
 459         const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
 460
 461         if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
 462                 return;
 463
 464         printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 465                inf->name, fsr, addr);
 466
 467         uc32_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
 468                         fsr, 0);
 469 }
 470
 471 asmlinkage void do_PrefetchAbort(unsigned long addr,
 472                         unsigned int ifsr, struct pt_regs *regs)
 473 {
 474         const struct fsr_info *inf = fsr_info + fsr_fs(ifsr);
 475
 476         if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
 477                 return;
 478
 479         printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
 480                inf->name, ifsr, addr);
 481
 482         uc32_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
 483                         ifsr, 0);
 484 }