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