arch/s390/mm/fault.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  S390 version
   4  *    Copyright IBM Corp. 1999
   5  *    Author(s): Hartmut Penner (hp@de.ibm.com)
   6  *               Ulrich Weigand (uweigand@de.ibm.com)
   7  *
   8  *  Derived from "arch/i386/mm/fault.c"
   9  *    Copyright (C) 1995  Linus Torvalds
  10  */
  11
  12 #include <linux/kernel_stat.h>
  13 #include <linux/perf_event.h>
  14 #include <linux/signal.h>
  15 #include <linux/sched.h>
  16 #include <linux/sched/debug.h>
  17 #include <linux/kernel.h>
  18 #include <linux/errno.h>
  19 #include <linux/string.h>
  20 #include <linux/types.h>
  21 #include <linux/ptrace.h>
  22 #include <linux/mman.h>
  23 #include <linux/mm.h>
  24 #include <linux/compat.h>
  25 #include <linux/smp.h>
  26 #include <linux/kdebug.h>
  27 #include <linux/init.h>
  28 #include <linux/console.h>
  29 #include <linux/extable.h>
  30 #include <linux/hardirq.h>
  31 #include <linux/kprobes.h>
  32 #include <linux/uaccess.h>
  33 #include <linux/hugetlb.h>
  34 #include <asm/asm-offsets.h>
  35 #include <asm/diag.h>
  36 #include <asm/pgtable.h>
  37 #include <asm/gmap.h>
  38 #include <asm/irq.h>
  39 #include <asm/mmu_context.h>
  40 #include <asm/facility.h>
  41 #include <asm/uv.h>
  42 #include "../kernel/entry.h"
  43
  44 #define __FAIL_ADDR_MASK -4096L
  45 #define __SUBCODE_MASK 0x0600
  46 #define __PF_RES_FIELD 0x8000000000000000ULL
  47
  48 #define VM_FAULT_BADCONTEXT     ((__force vm_fault_t) 0x010000)
  49 #define VM_FAULT_BADMAP         ((__force vm_fault_t) 0x020000)
  50 #define VM_FAULT_BADACCESS      ((__force vm_fault_t) 0x040000)
  51 #define VM_FAULT_SIGNAL         ((__force vm_fault_t) 0x080000)
  52 #define VM_FAULT_PFAULT         ((__force vm_fault_t) 0x100000)
  53
  54 enum fault_type {
  55         KERNEL_FAULT,
  56         USER_FAULT,
  57         VDSO_FAULT,
  58         GMAP_FAULT,
  59 };
  60
  61 static unsigned long store_indication __read_mostly;
  62
  63 static int __init fault_init(void)
  64 {
  65         if (test_facility(75))
  66                 store_indication = 0xc00;
  67         return 0;
  68 }
  69 early_initcall(fault_init);
  70
  71 /*
  72  * Find out which address space caused the exception.
  73  */
  74 static enum fault_type get_fault_type(struct pt_regs *regs)
  75 {
  76         unsigned long trans_exc_code;
  77
  78         trans_exc_code = regs->int_parm_long & 3;
  79         if (likely(trans_exc_code == 0)) {
  80                 /* primary space exception */
  81                 if (IS_ENABLED(CONFIG_PGSTE) &&
  82                     test_pt_regs_flag(regs, PIF_GUEST_FAULT))
  83                         return GMAP_FAULT;
  84                 if (current->thread.mm_segment == USER_DS)
  85                         return USER_FAULT;
  86                 return KERNEL_FAULT;
  87         }
  88         if (trans_exc_code == 2) {
  89                 /* secondary space exception */
  90                 if (current->thread.mm_segment & 1) {
  91                         if (current->thread.mm_segment == USER_DS_SACF)
  92                                 return USER_FAULT;
  93                         return KERNEL_FAULT;
  94                 }
  95                 return VDSO_FAULT;
  96         }
  97         if (trans_exc_code == 1) {
  98                 /* access register mode, not used in the kernel */
  99                 return USER_FAULT;
 100         }
 101         /* home space exception -> access via kernel ASCE */
 102         return KERNEL_FAULT;
 103 }
 104
 105 static int bad_address(void *p)
 106 {
 107         unsigned long dummy;
 108
 109         return probe_kernel_address((unsigned long *)p, dummy);
 110 }
 111
 112 static void dump_pagetable(unsigned long asce, unsigned long address)
 113 {
 114         unsigned long *table = __va(asce & _ASCE_ORIGIN);
 115
 116         pr_alert("AS:%016lx ", asce);
 117         switch (asce & _ASCE_TYPE_MASK) {
 118         case _ASCE_TYPE_REGION1:
 119                 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT;
 120                 if (bad_address(table))
 121                         goto bad;
 122                 pr_cont("R1:%016lx ", *table);
 123                 if (*table & _REGION_ENTRY_INVALID)
 124                         goto out;
 125                 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
 126                 fallthrough;
 127         case _ASCE_TYPE_REGION2:
 128                 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT;
 129                 if (bad_address(table))
 130                         goto bad;
 131                 pr_cont("R2:%016lx ", *table);
 132                 if (*table & _REGION_ENTRY_INVALID)
 133                         goto out;
 134                 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
 135                 fallthrough;
 136         case _ASCE_TYPE_REGION3:
 137                 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT;
 138                 if (bad_address(table))
 139                         goto bad;
 140                 pr_cont("R3:%016lx ", *table);
 141                 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE))
 142                         goto out;
 143                 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
 144                 fallthrough;
 145         case _ASCE_TYPE_SEGMENT:
 146                 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
 147                 if (bad_address(table))
 148                         goto bad;
 149                 pr_cont("S:%016lx ", *table);
 150                 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE))
 151                         goto out;
 152                 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN);
 153         }
 154         table += (address & _PAGE_INDEX) >> _PAGE_SHIFT;
 155         if (bad_address(table))
 156                 goto bad;
 157         pr_cont("P:%016lx ", *table);
 158 out:
 159         pr_cont("\n");
 160         return;
 161 bad:
 162         pr_cont("BAD\n");
 163 }
 164
 165 static void dump_fault_info(struct pt_regs *regs)
 166 {
 167         unsigned long asce;
 168
 169         pr_alert("Failing address: %016lx TEID: %016lx\n",
 170                  regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long);
 171         pr_alert("Fault in ");
 172         switch (regs->int_parm_long & 3) {
 173         case 3:
 174                 pr_cont("home space ");
 175                 break;
 176         case 2:
 177                 pr_cont("secondary space ");
 178                 break;
 179         case 1:
 180                 pr_cont("access register ");
 181                 break;
 182         case 0:
 183                 pr_cont("primary space ");
 184                 break;
 185         }
 186         pr_cont("mode while using ");
 187         switch (get_fault_type(regs)) {
 188         case USER_FAULT:
 189                 asce = S390_lowcore.user_asce;
 190                 pr_cont("user ");
 191                 break;
 192         case VDSO_FAULT:
 193                 asce = S390_lowcore.vdso_asce;
 194                 pr_cont("vdso ");
 195                 break;
 196         case GMAP_FAULT:
 197                 asce = ((struct gmap *) S390_lowcore.gmap)->asce;
 198                 pr_cont("gmap ");
 199                 break;
 200         case KERNEL_FAULT:
 201                 asce = S390_lowcore.kernel_asce;
 202                 pr_cont("kernel ");
 203                 break;
 204         default:
 205                 unreachable();
 206         }
 207         pr_cont("ASCE.\n");
 208         dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK);
 209 }
 210
 211 int show_unhandled_signals = 1;
 212
 213 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault)
 214 {
 215         if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
 216                 return;
 217         if (!unhandled_signal(current, signr))
 218                 return;
 219         if (!printk_ratelimit())
 220                 return;
 221         printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ",
 222                regs->int_code & 0xffff, regs->int_code >> 17);
 223         print_vma_addr(KERN_CONT "in ", regs->psw.addr);
 224         printk(KERN_CONT "\n");
 225         if (is_mm_fault)
 226                 dump_fault_info(regs);
 227         show_regs(regs);
 228 }
 229
 230 /*
 231  * Send SIGSEGV to task.  This is an external routine
 232  * to keep the stack usage of do_page_fault small.
 233  */
 234 static noinline void do_sigsegv(struct pt_regs *regs, int si_code)
 235 {
 236         report_user_fault(regs, SIGSEGV, 1);
 237         force_sig_fault(SIGSEGV, si_code,
 238                         (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK));
 239 }
 240
 241 const struct exception_table_entry *s390_search_extables(unsigned long addr)
 242 {
 243         const struct exception_table_entry *fixup;
 244
 245         fixup = search_extable(__start_dma_ex_table,
 246                                __stop_dma_ex_table - __start_dma_ex_table,
 247                                addr);
 248         if (!fixup)
 249                 fixup = search_exception_tables(addr);
 250         return fixup;
 251 }
 252
 253 static noinline void do_no_context(struct pt_regs *regs)
 254 {
 255         const struct exception_table_entry *fixup;
 256
 257         /* Are we prepared to handle this kernel fault?  */
 258         fixup = s390_search_extables(regs->psw.addr);
 259         if (fixup) {
 260                 regs->psw.addr = extable_fixup(fixup);
 261                 return;
 262         }
 263
 264         /*
 265          * Oops. The kernel tried to access some bad page. We'll have to
 266          * terminate things with extreme prejudice.
 267          */
 268         if (get_fault_type(regs) == KERNEL_FAULT)
 269                 printk(KERN_ALERT "Unable to handle kernel pointer dereference"
 270                        " in virtual kernel address space\n");
 271         else
 272                 printk(KERN_ALERT "Unable to handle kernel paging request"
 273                        " in virtual user address space\n");
 274         dump_fault_info(regs);
 275         die(regs, "Oops");
 276         do_exit(SIGKILL);
 277 }
 278
 279 static noinline void do_low_address(struct pt_regs *regs)
 280 {
 281         /* Low-address protection hit in kernel mode means
 282            NULL pointer write access in kernel mode.  */
 283         if (regs->psw.mask & PSW_MASK_PSTATE) {
 284                 /* Low-address protection hit in user mode 'cannot happen'. */
 285                 die (regs, "Low-address protection");
 286                 do_exit(SIGKILL);
 287         }
 288
 289         do_no_context(regs);
 290 }
 291
 292 static noinline void do_sigbus(struct pt_regs *regs)
 293 {
 294         /*
 295          * Send a sigbus, regardless of whether we were in kernel
 296          * or user mode.
 297          */
 298         force_sig_fault(SIGBUS, BUS_ADRERR,
 299                         (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK));
 300 }
 301
 302 static noinline int signal_return(struct pt_regs *regs)
 303 {
 304         u16 instruction;
 305         int rc;
 306
 307         rc = __get_user(instruction, (u16 __user *) regs->psw.addr);
 308         if (rc)
 309                 return rc;
 310         if (instruction == 0x0a77) {
 311                 set_pt_regs_flag(regs, PIF_SYSCALL);
 312                 regs->int_code = 0x00040077;
 313                 return 0;
 314         } else if (instruction == 0x0aad) {
 315                 set_pt_regs_flag(regs, PIF_SYSCALL);
 316                 regs->int_code = 0x000400ad;
 317                 return 0;
 318         }
 319         return -EACCES;
 320 }
 321
 322 static noinline void do_fault_error(struct pt_regs *regs, int access,
 323                                         vm_fault_t fault)
 324 {
 325         int si_code;
 326
 327         switch (fault) {
 328         case VM_FAULT_BADACCESS:
 329                 if (access == VM_EXEC && signal_return(regs) == 0)
 330                         break;
 331                 fallthrough;
 332         case VM_FAULT_BADMAP:
 333                 /* Bad memory access. Check if it is kernel or user space. */
 334                 if (user_mode(regs)) {
 335                         /* User mode accesses just cause a SIGSEGV */
 336                         si_code = (fault == VM_FAULT_BADMAP) ?
 337                                 SEGV_MAPERR : SEGV_ACCERR;
 338                         do_sigsegv(regs, si_code);
 339                         break;
 340                 }
 341                 fallthrough;
 342         case VM_FAULT_BADCONTEXT:
 343         case VM_FAULT_PFAULT:
 344                 do_no_context(regs);
 345                 break;
 346         case VM_FAULT_SIGNAL:
 347                 if (!user_mode(regs))
 348                         do_no_context(regs);
 349                 break;
 350         default: /* fault & VM_FAULT_ERROR */
 351                 if (fault & VM_FAULT_OOM) {
 352                         if (!user_mode(regs))
 353                                 do_no_context(regs);
 354                         else
 355                                 pagefault_out_of_memory();
 356                 } else if (fault & VM_FAULT_SIGSEGV) {
 357                         /* Kernel mode? Handle exceptions or die */
 358                         if (!user_mode(regs))
 359                                 do_no_context(regs);
 360                         else
 361                                 do_sigsegv(regs, SEGV_MAPERR);
 362                 } else if (fault & VM_FAULT_SIGBUS) {
 363                         /* Kernel mode? Handle exceptions or die */
 364                         if (!user_mode(regs))
 365                                 do_no_context(regs);
 366                         else
 367                                 do_sigbus(regs);
 368                 } else
 369                         BUG();
 370                 break;
 371         }
 372 }
 373
 374 /*
 375  * This routine handles page faults.  It determines the address,
 376  * and the problem, and then passes it off to one of the appropriate
 377  * routines.
 378  *
 379  * interruption code (int_code):
 380  *   04       Protection           ->  Write-Protection  (suprression)
 381  *   10       Segment translation  ->  Not present       (nullification)
 382  *   11       Page translation     ->  Not present       (nullification)
 383  *   3b       Region third trans.  ->  Not present       (nullification)
 384  */
 385 static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
 386 {
 387         struct gmap *gmap;
 388         struct task_struct *tsk;
 389         struct mm_struct *mm;
 390         struct vm_area_struct *vma;
 391         enum fault_type type;
 392         unsigned long trans_exc_code;
 393         unsigned long address;
 394         unsigned int flags;
 395         vm_fault_t fault;
 396
 397         tsk = current;
 398         /*
 399          * The instruction that caused the program check has
 400          * been nullified. Don't signal single step via SIGTRAP.
 401          */
 402         clear_pt_regs_flag(regs, PIF_PER_TRAP);
 403
 404         if (kprobe_page_fault(regs, 14))
 405                 return 0;
 406
 407         mm = tsk->mm;
 408         trans_exc_code = regs->int_parm_long;
 409
 410         /*
 411          * Verify that the fault happened in user space, that
 412          * we are not in an interrupt and that there is a
 413          * user context.
 414          */
 415         fault = VM_FAULT_BADCONTEXT;
 416         type = get_fault_type(regs);
 417         switch (type) {
 418         case KERNEL_FAULT:
 419                 goto out;
 420         case VDSO_FAULT:
 421                 fault = VM_FAULT_BADMAP;
 422                 goto out;
 423         case USER_FAULT:
 424         case GMAP_FAULT:
 425                 if (faulthandler_disabled() || !mm)
 426                         goto out;
 427                 break;
 428         }
 429
 430         address = trans_exc_code & __FAIL_ADDR_MASK;
 431         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 432         flags = FAULT_FLAG_DEFAULT;
 433         if (user_mode(regs))
 434                 flags |= FAULT_FLAG_USER;
 435         if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400)
 436                 flags |= FAULT_FLAG_WRITE;
 437         down_read(&mm->mmap_sem);
 438
 439         gmap = NULL;
 440         if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) {
 441                 gmap = (struct gmap *) S390_lowcore.gmap;
 442                 current->thread.gmap_addr = address;
 443                 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE);
 444                 current->thread.gmap_int_code = regs->int_code & 0xffff;
 445                 address = __gmap_translate(gmap, address);
 446                 if (address == -EFAULT) {
 447                         fault = VM_FAULT_BADMAP;
 448                         goto out_up;
 449                 }
 450                 if (gmap->pfault_enabled)
 451                         flags |= FAULT_FLAG_RETRY_NOWAIT;
 452         }
 453
 454 retry:
 455         fault = VM_FAULT_BADMAP;
 456         vma = find_vma(mm, address);
 457         if (!vma)
 458                 goto out_up;
 459
 460         if (unlikely(vma->vm_start > address)) {
 461                 if (!(vma->vm_flags & VM_GROWSDOWN))
 462                         goto out_up;
 463                 if (expand_stack(vma, address))
 464                         goto out_up;
 465         }
 466
 467         /*
 468          * Ok, we have a good vm_area for this memory access, so
 469          * we can handle it..
 470          */
 471         fault = VM_FAULT_BADACCESS;
 472         if (unlikely(!(vma->vm_flags & access)))
 473                 goto out_up;
 474
 475         if (is_vm_hugetlb_page(vma))
 476                 address &= HPAGE_MASK;
 477         /*
 478          * If for any reason at all we couldn't handle the fault,
 479          * make sure we exit gracefully rather than endlessly redo
 480          * the fault.
 481          */
 482         fault = handle_mm_fault(vma, address, flags);
 483         if (fault_signal_pending(fault, regs)) {
 484                 fault = VM_FAULT_SIGNAL;
 485                 if (flags & FAULT_FLAG_RETRY_NOWAIT)
 486                         goto out_up;
 487                 goto out;
 488         }
 489         if (unlikely(fault & VM_FAULT_ERROR))
 490                 goto out_up;
 491
 492         /*
 493          * Major/minor page fault accounting is only done on the
 494          * initial attempt. If we go through a retry, it is extremely
 495          * likely that the page will be found in page cache at that point.
 496          */
 497         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 498                 if (fault & VM_FAULT_MAJOR) {
 499                         tsk->maj_flt++;
 500                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 501                                       regs, address);
 502                 } else {
 503                         tsk->min_flt++;
 504                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 505                                       regs, address);
 506                 }
 507                 if (fault & VM_FAULT_RETRY) {
 508                         if (IS_ENABLED(CONFIG_PGSTE) && gmap &&
 509                             (flags & FAULT_FLAG_RETRY_NOWAIT)) {
 510                                 /* FAULT_FLAG_RETRY_NOWAIT has been set,
 511                                  * mmap_sem has not been released */
 512                                 current->thread.gmap_pfault = 1;
 513                                 fault = VM_FAULT_PFAULT;
 514                                 goto out_up;
 515                         }
 516                         flags &= ~FAULT_FLAG_RETRY_NOWAIT;
 517                         flags |= FAULT_FLAG_TRIED;
 518                         down_read(&mm->mmap_sem);
 519                         goto retry;
 520                 }
 521         }
 522         if (IS_ENABLED(CONFIG_PGSTE) && gmap) {
 523                 address =  __gmap_link(gmap, current->thread.gmap_addr,
 524                                        address);
 525                 if (address == -EFAULT) {
 526                         fault = VM_FAULT_BADMAP;
 527                         goto out_up;
 528                 }
 529                 if (address == -ENOMEM) {
 530                         fault = VM_FAULT_OOM;
 531                         goto out_up;
 532                 }
 533         }
 534         fault = 0;
 535 out_up:
 536         up_read(&mm->mmap_sem);
 537 out:
 538         return fault;
 539 }
 540
 541 void do_protection_exception(struct pt_regs *regs)
 542 {
 543         unsigned long trans_exc_code;
 544         int access;
 545         vm_fault_t fault;
 546
 547         trans_exc_code = regs->int_parm_long;
 548         /*
 549          * Protection exceptions are suppressing, decrement psw address.
 550          * The exception to this rule are aborted transactions, for these
 551          * the PSW already points to the correct location.
 552          */
 553         if (!(regs->int_code & 0x200))
 554                 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
 555         /*
 556          * Check for low-address protection.  This needs to be treated
 557          * as a special case because the translation exception code
 558          * field is not guaranteed to contain valid data in this case.
 559          */
 560         if (unlikely(!(trans_exc_code & 4))) {
 561                 do_low_address(regs);
 562                 return;
 563         }
 564         if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) {
 565                 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) |
 566                                         (regs->psw.addr & PAGE_MASK);
 567                 access = VM_EXEC;
 568                 fault = VM_FAULT_BADACCESS;
 569         } else {
 570                 access = VM_WRITE;
 571                 fault = do_exception(regs, access);
 572         }
 573         if (unlikely(fault))
 574                 do_fault_error(regs, access, fault);
 575 }
 576 NOKPROBE_SYMBOL(do_protection_exception);
 577
 578 void do_dat_exception(struct pt_regs *regs)
 579 {
 580         int access;
 581         vm_fault_t fault;
 582
 583         access = VM_ACCESS_FLAGS;
 584         fault = do_exception(regs, access);
 585         if (unlikely(fault))
 586                 do_fault_error(regs, access, fault);
 587 }
 588 NOKPROBE_SYMBOL(do_dat_exception);
 589
 590 #ifdef CONFIG_PFAULT
 591 /*
 592  * 'pfault' pseudo page faults routines.
 593  */
 594 static int pfault_disable;
 595
 596 static int __init nopfault(char *str)
 597 {
 598         pfault_disable = 1;
 599         return 1;
 600 }
 601
 602 __setup("nopfault", nopfault);
 603
 604 struct pfault_refbk {
 605         u16 refdiagc;
 606         u16 reffcode;
 607         u16 refdwlen;
 608         u16 refversn;
 609         u64 refgaddr;
 610         u64 refselmk;
 611         u64 refcmpmk;
 612         u64 reserved;
 613 } __attribute__ ((packed, aligned(8)));
 614
 615 static struct pfault_refbk pfault_init_refbk = {
 616         .refdiagc = 0x258,
 617         .reffcode = 0,
 618         .refdwlen = 5,
 619         .refversn = 2,
 620         .refgaddr = __LC_LPP,
 621         .refselmk = 1ULL << 48,
 622         .refcmpmk = 1ULL << 48,
 623         .reserved = __PF_RES_FIELD
 624 };
 625
 626 int pfault_init(void)
 627 {
 628         int rc;
 629
 630         if (pfault_disable)
 631                 return -1;
 632         diag_stat_inc(DIAG_STAT_X258);
 633         asm volatile(
 634                 "       diag    %1,%0,0x258\n"
 635                 "0:     j       2f\n"
 636                 "1:     la      %0,8\n"
 637                 "2:\n"
 638                 EX_TABLE(0b,1b)
 639                 : "=d" (rc)
 640                 : "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc");
 641         return rc;
 642 }
 643
 644 static struct pfault_refbk pfault_fini_refbk = {
 645         .refdiagc = 0x258,
 646         .reffcode = 1,
 647         .refdwlen = 5,
 648         .refversn = 2,
 649 };
 650
 651 void pfault_fini(void)
 652 {
 653
 654         if (pfault_disable)
 655                 return;
 656         diag_stat_inc(DIAG_STAT_X258);
 657         asm volatile(
 658                 "       diag    %0,0,0x258\n"
 659                 "0:     nopr    %%r7\n"
 660                 EX_TABLE(0b,0b)
 661                 : : "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk) : "cc");
 662 }
 663
 664 static DEFINE_SPINLOCK(pfault_lock);
 665 static LIST_HEAD(pfault_list);
 666
 667 #define PF_COMPLETE     0x0080
 668
 669 /*
 670  * The mechanism of our pfault code: if Linux is running as guest, runs a user
 671  * space process and the user space process accesses a page that the host has
 672  * paged out we get a pfault interrupt.
 673  *
 674  * This allows us, within the guest, to schedule a different process. Without
 675  * this mechanism the host would have to suspend the whole virtual cpu until
 676  * the page has been paged in.
 677  *
 678  * So when we get such an interrupt then we set the state of the current task
 679  * to uninterruptible and also set the need_resched flag. Both happens within
 680  * interrupt context(!). If we later on want to return to user space we
 681  * recognize the need_resched flag and then call schedule().  It's not very
 682  * obvious how this works...
 683  *
 684  * Of course we have a lot of additional fun with the completion interrupt (->
 685  * host signals that a page of a process has been paged in and the process can
 686  * continue to run). This interrupt can arrive on any cpu and, since we have
 687  * virtual cpus, actually appear before the interrupt that signals that a page
 688  * is missing.
 689  */
 690 static void pfault_interrupt(struct ext_code ext_code,
 691                              unsigned int param32, unsigned long param64)
 692 {
 693         struct task_struct *tsk;
 694         __u16 subcode;
 695         pid_t pid;
 696
 697         /*
 698          * Get the external interruption subcode & pfault initial/completion
 699          * signal bit. VM stores this in the 'cpu address' field associated
 700          * with the external interrupt.
 701          */
 702         subcode = ext_code.subcode;
 703         if ((subcode & 0xff00) != __SUBCODE_MASK)
 704                 return;
 705         inc_irq_stat(IRQEXT_PFL);
 706         /* Get the token (= pid of the affected task). */
 707         pid = param64 & LPP_PID_MASK;
 708         rcu_read_lock();
 709         tsk = find_task_by_pid_ns(pid, &init_pid_ns);
 710         if (tsk)
 711                 get_task_struct(tsk);
 712         rcu_read_unlock();
 713         if (!tsk)
 714                 return;
 715         spin_lock(&pfault_lock);
 716         if (subcode & PF_COMPLETE) {
 717                 /* signal bit is set -> a page has been swapped in by VM */
 718                 if (tsk->thread.pfault_wait == 1) {
 719                         /* Initial interrupt was faster than the completion
 720                          * interrupt. pfault_wait is valid. Set pfault_wait
 721                          * back to zero and wake up the process. This can
 722                          * safely be done because the task is still sleeping
 723                          * and can't produce new pfaults. */
 724                         tsk->thread.pfault_wait = 0;
 725                         list_del(&tsk->thread.list);
 726                         wake_up_process(tsk);
 727                         put_task_struct(tsk);
 728                 } else {
 729                         /* Completion interrupt was faster than initial
 730                          * interrupt. Set pfault_wait to -1 so the initial
 731                          * interrupt doesn't put the task to sleep.
 732                          * If the task is not running, ignore the completion
 733                          * interrupt since it must be a leftover of a PFAULT
 734                          * CANCEL operation which didn't remove all pending
 735                          * completion interrupts. */
 736                         if (tsk->state == TASK_RUNNING)
 737                                 tsk->thread.pfault_wait = -1;
 738                 }
 739         } else {
 740                 /* signal bit not set -> a real page is missing. */
 741                 if (WARN_ON_ONCE(tsk != current))
 742                         goto out;
 743                 if (tsk->thread.pfault_wait == 1) {
 744                         /* Already on the list with a reference: put to sleep */
 745                         goto block;
 746                 } else if (tsk->thread.pfault_wait == -1) {
 747                         /* Completion interrupt was faster than the initial
 748                          * interrupt (pfault_wait == -1). Set pfault_wait
 749                          * back to zero and exit. */
 750                         tsk->thread.pfault_wait = 0;
 751                 } else {
 752                         /* Initial interrupt arrived before completion
 753                          * interrupt. Let the task sleep.
 754                          * An extra task reference is needed since a different
 755                          * cpu may set the task state to TASK_RUNNING again
 756                          * before the scheduler is reached. */
 757                         get_task_struct(tsk);
 758                         tsk->thread.pfault_wait = 1;
 759                         list_add(&tsk->thread.list, &pfault_list);
 760 block:
 761                         /* Since this must be a userspace fault, there
 762                          * is no kernel task state to trample. Rely on the
 763                          * return to userspace schedule() to block. */
 764                         __set_current_state(TASK_UNINTERRUPTIBLE);
 765                         set_tsk_need_resched(tsk);
 766                         set_preempt_need_resched();
 767                 }
 768         }
 769 out:
 770         spin_unlock(&pfault_lock);
 771         put_task_struct(tsk);
 772 }
 773
 774 static int pfault_cpu_dead(unsigned int cpu)
 775 {
 776         struct thread_struct *thread, *next;
 777         struct task_struct *tsk;
 778
 779         spin_lock_irq(&pfault_lock);
 780         list_for_each_entry_safe(thread, next, &pfault_list, list) {
 781                 thread->pfault_wait = 0;
 782                 list_del(&thread->list);
 783                 tsk = container_of(thread, struct task_struct, thread);
 784                 wake_up_process(tsk);
 785                 put_task_struct(tsk);
 786         }
 787         spin_unlock_irq(&pfault_lock);
 788         return 0;
 789 }
 790
 791 static int __init pfault_irq_init(void)
 792 {
 793         int rc;
 794
 795         rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt);
 796         if (rc)
 797                 goto out_extint;
 798         rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP;
 799         if (rc)
 800                 goto out_pfault;
 801         irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL);
 802         cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead",
 803                                   NULL, pfault_cpu_dead);
 804         return 0;
 805
 806 out_pfault:
 807         unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt);
 808 out_extint:
 809         pfault_disable = 1;
 810         return rc;
 811 }
 812 early_initcall(pfault_irq_init);
 813
 814 #endif /* CONFIG_PFAULT */
 815
 816 #if IS_ENABLED(CONFIG_PGSTE)
 817 void do_secure_storage_access(struct pt_regs *regs)
 818 {
 819         unsigned long addr = regs->int_parm_long & __FAIL_ADDR_MASK;
 820         struct vm_area_struct *vma;
 821         struct mm_struct *mm;
 822         struct page *page;
 823         int rc;
 824
 825         switch (get_fault_type(regs)) {
 826         case USER_FAULT:
 827                 mm = current->mm;
 828                 down_read(&mm->mmap_sem);
 829                 vma = find_vma(mm, addr);
 830                 if (!vma) {
 831                         up_read(&mm->mmap_sem);
 832                         do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
 833                         break;
 834                 }
 835                 page = follow_page(vma, addr, FOLL_WRITE | FOLL_GET);
 836                 if (IS_ERR_OR_NULL(page)) {
 837                         up_read(&mm->mmap_sem);
 838                         break;
 839                 }
 840                 if (arch_make_page_accessible(page))
 841                         send_sig(SIGSEGV, current, 0);
 842                 put_page(page);
 843                 up_read(&mm->mmap_sem);
 844                 break;
 845         case KERNEL_FAULT:
 846                 page = phys_to_page(addr);
 847                 if (unlikely(!try_get_page(page)))
 848                         break;
 849                 rc = arch_make_page_accessible(page);
 850                 put_page(page);
 851                 if (rc)
 852                         BUG();
 853                 break;
 854         case VDSO_FAULT:
 855         case GMAP_FAULT:
 856         default:
 857                 do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
 858                 WARN_ON_ONCE(1);
 859         }
 860 }
 861 NOKPROBE_SYMBOL(do_secure_storage_access);
 862
 863 void do_non_secure_storage_access(struct pt_regs *regs)
 864 {
 865         unsigned long gaddr = regs->int_parm_long & __FAIL_ADDR_MASK;
 866         struct gmap *gmap = (struct gmap *)S390_lowcore.gmap;
 867
 868         if (get_fault_type(regs) != GMAP_FAULT) {
 869                 do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
 870                 WARN_ON_ONCE(1);
 871                 return;
 872         }
 873
 874         if (gmap_convert_to_secure(gmap, gaddr) == -EINVAL)
 875                 send_sig(SIGSEGV, current, 0);
 876 }
 877 NOKPROBE_SYMBOL(do_non_secure_storage_access);
 878
 879 #else
 880 void do_secure_storage_access(struct pt_regs *regs)
 881 {
 882         default_trap_handler(regs);
 883 }
 884
 885 void do_non_secure_storage_access(struct pt_regs *regs)
 886 {
 887         default_trap_handler(regs);
 888 }
 889 #endif