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 static unsigned long store_indication __read_mostly;
54
fault_init(void)55 static int __init fault_init(void)
56 {
57 if (test_facility(75))
58 store_indication = 0xc00;
59 return 0;
60 }
61 early_initcall(fault_init);
62
notify_page_fault(struct pt_regs * regs)63 static inline int notify_page_fault(struct pt_regs *regs)
64 {
65 int ret = 0;
66
67 /* kprobe_running() needs smp_processor_id() */
68 if (kprobes_built_in() && !user_mode(regs)) {
69 preempt_disable();
70 if (kprobe_running() && kprobe_fault_handler(regs, 14))
71 ret = 1;
72 preempt_enable();
73 }
74 return ret;
75 }
76
77
78 /*
79 * Unlock any spinlocks which will prevent us from getting the
80 * message out.
81 */
bust_spinlocks(int yes)82 void bust_spinlocks(int yes)
83 {
84 if (yes) {
85 oops_in_progress = 1;
86 } else {
87 int loglevel_save = console_loglevel;
88 console_unblank();
89 oops_in_progress = 0;
90 /*
91 * OK, the message is on the console. Now we call printk()
92 * without oops_in_progress set so that printk will give klogd
93 * a poke. Hold onto your hats...
94 */
95 console_loglevel = 15;
96 printk(" ");
97 console_loglevel = loglevel_save;
98 }
99 }
100
101 /*
102 * Returns the address space associated with the fault.
103 * Returns 0 for kernel space and 1 for user space.
104 */
user_space_fault(struct pt_regs * regs)105 static inline int user_space_fault(struct pt_regs *regs)
106 {
107 unsigned long trans_exc_code;
108
109 /*
110 * The lowest two bits of the translation exception
111 * identification indicate which paging table was used.
112 */
113 trans_exc_code = regs->int_parm_long & 3;
114 if (trans_exc_code == 3) /* home space -> kernel */
115 return 0;
116 if (user_mode(regs))
117 return 1;
118 if (trans_exc_code == 2) /* secondary space -> set_fs */
119 return current->thread.mm_segment.ar4;
120 if (current->flags & PF_VCPU)
121 return 1;
122 return 0;
123 }
124
bad_address(void * p)125 static int bad_address(void *p)
126 {
127 unsigned long dummy;
128
129 return probe_kernel_address((unsigned long *)p, dummy);
130 }
131
dump_pagetable(unsigned long asce,unsigned long address)132 static void dump_pagetable(unsigned long asce, unsigned long address)
133 {
134 unsigned long *table = __va(asce & _ASCE_ORIGIN);
135
136 pr_alert("AS:%016lx ", asce);
137 switch (asce & _ASCE_TYPE_MASK) {
138 case _ASCE_TYPE_REGION1:
139 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT;
140 if (bad_address(table))
141 goto bad;
142 pr_cont("R1:%016lx ", *table);
143 if (*table & _REGION_ENTRY_INVALID)
144 goto out;
145 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
146 /* fallthrough */
147 case _ASCE_TYPE_REGION2:
148 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT;
149 if (bad_address(table))
150 goto bad;
151 pr_cont("R2:%016lx ", *table);
152 if (*table & _REGION_ENTRY_INVALID)
153 goto out;
154 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
155 /* fallthrough */
156 case _ASCE_TYPE_REGION3:
157 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT;
158 if (bad_address(table))
159 goto bad;
160 pr_cont("R3:%016lx ", *table);
161 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE))
162 goto out;
163 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
164 /* fallthrough */
165 case _ASCE_TYPE_SEGMENT:
166 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
167 if (bad_address(table))
168 goto bad;
169 pr_cont("S:%016lx ", *table);
170 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE))
171 goto out;
172 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN);
173 }
174 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT;
175 if (bad_address(table))
176 goto bad;
177 pr_cont("P:%016lx ", *table);
178 out:
179 pr_cont("\n");
180 return;
181 bad:
182 pr_cont("BAD\n");
183 }
184
dump_fault_info(struct pt_regs * regs)185 static void dump_fault_info(struct pt_regs *regs)
186 {
187 unsigned long asce;
188
189 pr_alert("Failing address: %016lx TEID: %016lx\n",
190 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long);
191 pr_alert("Fault in ");
192 switch (regs->int_parm_long & 3) {
193 case 3:
194 pr_cont("home space ");
195 break;
196 case 2:
197 pr_cont("secondary space ");
198 break;
199 case 1:
200 pr_cont("access register ");
201 break;
202 case 0:
203 pr_cont("primary space ");
204 break;
205 }
206 pr_cont("mode while using ");
207 if (!user_space_fault(regs)) {
208 asce = S390_lowcore.kernel_asce;
209 pr_cont("kernel ");
210 }
211 #ifdef CONFIG_PGSTE
212 else if ((current->flags & PF_VCPU) && S390_lowcore.gmap) {
213 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap;
214 asce = gmap->asce;
215 pr_cont("gmap ");
216 }
217 #endif
218 else {
219 asce = S390_lowcore.user_asce;
220 pr_cont("user ");
221 }
222 pr_cont("ASCE.\n");
223 dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK);
224 }
225
226 int show_unhandled_signals = 1;
227
report_user_fault(struct pt_regs * regs,long signr,int is_mm_fault)228 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault)
229 {
230 if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
231 return;
232 if (!unhandled_signal(current, signr))
233 return;
234 if (!printk_ratelimit())
235 return;
236 printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ",
237 regs->int_code & 0xffff, regs->int_code >> 17);
238 print_vma_addr(KERN_CONT "in ", regs->psw.addr);
239 printk(KERN_CONT "\n");
240 if (is_mm_fault)
241 dump_fault_info(regs);
242 show_regs(regs);
243 }
244
245 /*
246 * Send SIGSEGV to task. This is an external routine
247 * to keep the stack usage of do_page_fault small.
248 */
do_sigsegv(struct pt_regs * regs,int si_code)249 static noinline void do_sigsegv(struct pt_regs *regs, int si_code)
250 {
251 struct siginfo si;
252
253 report_user_fault(regs, SIGSEGV, 1);
254 si.si_signo = SIGSEGV;
255 si.si_errno = 0;
256 si.si_code = si_code;
257 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK);
258 force_sig_info(SIGSEGV, &si, current);
259 }
260
do_no_context(struct pt_regs * regs)261 static noinline void do_no_context(struct pt_regs *regs)
262 {
263 const struct exception_table_entry *fixup;
264
265 /* Are we prepared to handle this kernel fault? */
266 fixup = search_exception_tables(regs->psw.addr);
267 if (fixup) {
268 regs->psw.addr = extable_fixup(fixup);
269 return;
270 }
271
272 /*
273 * Oops. The kernel tried to access some bad page. We'll have to
274 * terminate things with extreme prejudice.
275 */
276 if (!user_space_fault(regs))
277 printk(KERN_ALERT "Unable to handle kernel pointer dereference"
278 " in virtual kernel address space\n");
279 else
280 printk(KERN_ALERT "Unable to handle kernel paging request"
281 " in virtual user address space\n");
282 dump_fault_info(regs);
283 die(regs, "Oops");
284 do_exit(SIGKILL);
285 }
286
do_low_address(struct pt_regs * regs)287 static noinline void do_low_address(struct pt_regs *regs)
288 {
289 /* Low-address protection hit in kernel mode means
290 NULL pointer write access in kernel mode. */
291 if (regs->psw.mask & PSW_MASK_PSTATE) {
292 /* Low-address protection hit in user mode 'cannot happen'. */
293 die (regs, "Low-address protection");
294 do_exit(SIGKILL);
295 }
296
297 do_no_context(regs);
298 }
299
do_sigbus(struct pt_regs * regs)300 static noinline void do_sigbus(struct pt_regs *regs)
301 {
302 struct task_struct *tsk = current;
303 struct siginfo si;
304
305 /*
306 * Send a sigbus, regardless of whether we were in kernel
307 * or user mode.
308 */
309 si.si_signo = SIGBUS;
310 si.si_errno = 0;
311 si.si_code = BUS_ADRERR;
312 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK);
313 force_sig_info(SIGBUS, &si, tsk);
314 }
315
signal_return(struct pt_regs * regs)316 static noinline int signal_return(struct pt_regs *regs)
317 {
318 u16 instruction;
319 int rc;
320
321 rc = __get_user(instruction, (u16 __user *) regs->psw.addr);
322 if (rc)
323 return rc;
324 if (instruction == 0x0a77) {
325 set_pt_regs_flag(regs, PIF_SYSCALL);
326 regs->int_code = 0x00040077;
327 return 0;
328 } else if (instruction == 0x0aad) {
329 set_pt_regs_flag(regs, PIF_SYSCALL);
330 regs->int_code = 0x000400ad;
331 return 0;
332 }
333 return -EACCES;
334 }
335
do_fault_error(struct pt_regs * regs,int access,int fault)336 static noinline void do_fault_error(struct pt_regs *regs, int access, int fault)
337 {
338 int si_code;
339
340 switch (fault) {
341 case VM_FAULT_BADACCESS:
342 if (access == VM_EXEC && signal_return(regs) == 0)
343 break;
344 case VM_FAULT_BADMAP:
345 /* Bad memory access. Check if it is kernel or user space. */
346 if (user_mode(regs)) {
347 /* User mode accesses just cause a SIGSEGV */
348 si_code = (fault == VM_FAULT_BADMAP) ?
349 SEGV_MAPERR : SEGV_ACCERR;
350 do_sigsegv(regs, si_code);
351 break;
352 }
353 case VM_FAULT_BADCONTEXT:
354 case VM_FAULT_PFAULT:
355 do_no_context(regs);
356 break;
357 case VM_FAULT_SIGNAL:
358 if (!user_mode(regs))
359 do_no_context(regs);
360 break;
361 default: /* fault & VM_FAULT_ERROR */
362 if (fault & VM_FAULT_OOM) {
363 if (!user_mode(regs))
364 do_no_context(regs);
365 else
366 pagefault_out_of_memory();
367 } else if (fault & VM_FAULT_SIGSEGV) {
368 /* Kernel mode? Handle exceptions or die */
369 if (!user_mode(regs))
370 do_no_context(regs);
371 else
372 do_sigsegv(regs, SEGV_MAPERR);
373 } else if (fault & VM_FAULT_SIGBUS) {
374 /* Kernel mode? Handle exceptions or die */
375 if (!user_mode(regs))
376 do_no_context(regs);
377 else
378 do_sigbus(regs);
379 } else
380 BUG();
381 break;
382 }
383 }
384
385 /*
386 * This routine handles page faults. It determines the address,
387 * and the problem, and then passes it off to one of the appropriate
388 * routines.
389 *
390 * interruption code (int_code):
391 * 04 Protection -> Write-Protection (suprression)
392 * 10 Segment translation -> Not present (nullification)
393 * 11 Page translation -> Not present (nullification)
394 * 3b Region third trans. -> Not present (nullification)
395 */
do_exception(struct pt_regs * regs,int access)396 static inline int do_exception(struct pt_regs *regs, int access)
397 {
398 #ifdef CONFIG_PGSTE
399 struct gmap *gmap;
400 #endif
401 struct task_struct *tsk;
402 struct mm_struct *mm;
403 struct vm_area_struct *vma;
404 unsigned long trans_exc_code;
405 unsigned long address;
406 unsigned int flags;
407 int fault;
408
409 tsk = current;
410 /*
411 * The instruction that caused the program check has
412 * been nullified. Don't signal single step via SIGTRAP.
413 */
414 clear_pt_regs_flag(regs, PIF_PER_TRAP);
415
416 if (notify_page_fault(regs))
417 return 0;
418
419 mm = tsk->mm;
420 trans_exc_code = regs->int_parm_long;
421
422 /*
423 * Verify that the fault happened in user space, that
424 * we are not in an interrupt and that there is a
425 * user context.
426 */
427 fault = VM_FAULT_BADCONTEXT;
428 if (unlikely(!user_space_fault(regs) || faulthandler_disabled() || !mm))
429 goto out;
430
431 address = trans_exc_code & __FAIL_ADDR_MASK;
432 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
433 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
434 if (user_mode(regs))
435 flags |= FAULT_FLAG_USER;
436 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400)
437 flags |= FAULT_FLAG_WRITE;
438 down_read(&mm->mmap_sem);
439
440 #ifdef CONFIG_PGSTE
441 gmap = (current->flags & PF_VCPU) ?
442 (struct gmap *) S390_lowcore.gmap : NULL;
443 if (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 #endif
456
457 retry:
458 fault = VM_FAULT_BADMAP;
459 vma = find_vma(mm, address);
460 if (!vma)
461 goto out_up;
462
463 if (unlikely(vma->vm_start > address)) {
464 if (!(vma->vm_flags & VM_GROWSDOWN))
465 goto out_up;
466 if (expand_stack(vma, address))
467 goto out_up;
468 }
469
470 /*
471 * Ok, we have a good vm_area for this memory access, so
472 * we can handle it..
473 */
474 fault = VM_FAULT_BADACCESS;
475 if (unlikely(!(vma->vm_flags & access)))
476 goto out_up;
477
478 if (is_vm_hugetlb_page(vma))
479 address &= HPAGE_MASK;
480 /*
481 * If for any reason at all we couldn't handle the fault,
482 * make sure we exit gracefully rather than endlessly redo
483 * the fault.
484 */
485 fault = handle_mm_fault(vma, address, flags);
486 /* No reason to continue if interrupted by SIGKILL. */
487 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
488 fault = VM_FAULT_SIGNAL;
489 if (flags & FAULT_FLAG_RETRY_NOWAIT)
490 goto out_up;
491 goto out;
492 }
493 if (unlikely(fault & VM_FAULT_ERROR))
494 goto out_up;
495
496 /*
497 * Major/minor page fault accounting is only done on the
498 * initial attempt. If we go through a retry, it is extremely
499 * likely that the page will be found in page cache at that point.
500 */
501 if (flags & FAULT_FLAG_ALLOW_RETRY) {
502 if (fault & VM_FAULT_MAJOR) {
503 tsk->maj_flt++;
504 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
505 regs, address);
506 } else {
507 tsk->min_flt++;
508 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
509 regs, address);
510 }
511 if (fault & VM_FAULT_RETRY) {
512 #ifdef CONFIG_PGSTE
513 if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) {
514 /* FAULT_FLAG_RETRY_NOWAIT has been set,
515 * mmap_sem has not been released */
516 current->thread.gmap_pfault = 1;
517 fault = VM_FAULT_PFAULT;
518 goto out_up;
519 }
520 #endif
521 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
522 * of starvation. */
523 flags &= ~(FAULT_FLAG_ALLOW_RETRY |
524 FAULT_FLAG_RETRY_NOWAIT);
525 flags |= FAULT_FLAG_TRIED;
526 down_read(&mm->mmap_sem);
527 goto retry;
528 }
529 }
530 #ifdef CONFIG_PGSTE
531 if (gmap) {
532 address = __gmap_link(gmap, current->thread.gmap_addr,
533 address);
534 if (address == -EFAULT) {
535 fault = VM_FAULT_BADMAP;
536 goto out_up;
537 }
538 if (address == -ENOMEM) {
539 fault = VM_FAULT_OOM;
540 goto out_up;
541 }
542 }
543 #endif
544 fault = 0;
545 out_up:
546 up_read(&mm->mmap_sem);
547 out:
548 return fault;
549 }
550
do_protection_exception(struct pt_regs * regs)551 void do_protection_exception(struct pt_regs *regs)
552 {
553 unsigned long trans_exc_code;
554 int access, fault;
555
556 trans_exc_code = regs->int_parm_long;
557 /*
558 * Protection exceptions are suppressing, decrement psw address.
559 * The exception to this rule are aborted transactions, for these
560 * the PSW already points to the correct location.
561 */
562 if (!(regs->int_code & 0x200))
563 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
564 /*
565 * Check for low-address protection. This needs to be treated
566 * as a special case because the translation exception code
567 * field is not guaranteed to contain valid data in this case.
568 */
569 if (unlikely(!(trans_exc_code & 4))) {
570 do_low_address(regs);
571 return;
572 }
573 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) {
574 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) |
575 (regs->psw.addr & PAGE_MASK);
576 access = VM_EXEC;
577 fault = VM_FAULT_BADACCESS;
578 } else {
579 access = VM_WRITE;
580 fault = do_exception(regs, access);
581 }
582 if (unlikely(fault))
583 do_fault_error(regs, access, fault);
584 }
585 NOKPROBE_SYMBOL(do_protection_exception);
586
do_dat_exception(struct pt_regs * regs)587 void do_dat_exception(struct pt_regs *regs)
588 {
589 int access, fault;
590
591 access = VM_READ | VM_EXEC | VM_WRITE;
592 fault = do_exception(regs, access);
593 if (unlikely(fault))
594 do_fault_error(regs, access, fault);
595 }
596 NOKPROBE_SYMBOL(do_dat_exception);
597
598 #ifdef CONFIG_PFAULT
599 /*
600 * 'pfault' pseudo page faults routines.
601 */
602 static int pfault_disable;
603
nopfault(char * str)604 static int __init nopfault(char *str)
605 {
606 pfault_disable = 1;
607 return 1;
608 }
609
610 __setup("nopfault", nopfault);
611
612 struct pfault_refbk {
613 u16 refdiagc;
614 u16 reffcode;
615 u16 refdwlen;
616 u16 refversn;
617 u64 refgaddr;
618 u64 refselmk;
619 u64 refcmpmk;
620 u64 reserved;
621 } __attribute__ ((packed, aligned(8)));
622
pfault_init(void)623 int pfault_init(void)
624 {
625 struct pfault_refbk refbk = {
626 .refdiagc = 0x258,
627 .reffcode = 0,
628 .refdwlen = 5,
629 .refversn = 2,
630 .refgaddr = __LC_LPP,
631 .refselmk = 1ULL << 48,
632 .refcmpmk = 1ULL << 48,
633 .reserved = __PF_RES_FIELD };
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) : "a" (&refbk), "m" (refbk) : "cc");
646 return rc;
647 }
648
pfault_fini(void)649 void pfault_fini(void)
650 {
651 struct pfault_refbk refbk = {
652 .refdiagc = 0x258,
653 .reffcode = 1,
654 .refdwlen = 5,
655 .refversn = 2,
656 };
657
658 if (pfault_disable)
659 return;
660 diag_stat_inc(DIAG_STAT_X258);
661 asm volatile(
662 " diag %0,0,0x258\n"
663 "0: nopr %%r7\n"
664 EX_TABLE(0b,0b)
665 : : "a" (&refbk), "m" (refbk) : "cc");
666 }
667
668 static DEFINE_SPINLOCK(pfault_lock);
669 static LIST_HEAD(pfault_list);
670
671 #define PF_COMPLETE 0x0080
672
673 /*
674 * The mechanism of our pfault code: if Linux is running as guest, runs a user
675 * space process and the user space process accesses a page that the host has
676 * paged out we get a pfault interrupt.
677 *
678 * This allows us, within the guest, to schedule a different process. Without
679 * this mechanism the host would have to suspend the whole virtual cpu until
680 * the page has been paged in.
681 *
682 * So when we get such an interrupt then we set the state of the current task
683 * to uninterruptible and also set the need_resched flag. Both happens within
684 * interrupt context(!). If we later on want to return to user space we
685 * recognize the need_resched flag and then call schedule(). It's not very
686 * obvious how this works...
687 *
688 * Of course we have a lot of additional fun with the completion interrupt (->
689 * host signals that a page of a process has been paged in and the process can
690 * continue to run). This interrupt can arrive on any cpu and, since we have
691 * virtual cpus, actually appear before the interrupt that signals that a page
692 * is missing.
693 */
pfault_interrupt(struct ext_code ext_code,unsigned int param32,unsigned long param64)694 static void pfault_interrupt(struct ext_code ext_code,
695 unsigned int param32, unsigned long param64)
696 {
697 struct task_struct *tsk;
698 __u16 subcode;
699 pid_t pid;
700
701 /*
702 * Get the external interruption subcode & pfault initial/completion
703 * signal bit. VM stores this in the 'cpu address' field associated
704 * with the external interrupt.
705 */
706 subcode = ext_code.subcode;
707 if ((subcode & 0xff00) != __SUBCODE_MASK)
708 return;
709 inc_irq_stat(IRQEXT_PFL);
710 /* Get the token (= pid of the affected task). */
711 pid = param64 & LPP_PFAULT_PID_MASK;
712 rcu_read_lock();
713 tsk = find_task_by_pid_ns(pid, &init_pid_ns);
714 if (tsk)
715 get_task_struct(tsk);
716 rcu_read_unlock();
717 if (!tsk)
718 return;
719 spin_lock(&pfault_lock);
720 if (subcode & PF_COMPLETE) {
721 /* signal bit is set -> a page has been swapped in by VM */
722 if (tsk->thread.pfault_wait == 1) {
723 /* Initial interrupt was faster than the completion
724 * interrupt. pfault_wait is valid. Set pfault_wait
725 * back to zero and wake up the process. This can
726 * safely be done because the task is still sleeping
727 * and can't produce new pfaults. */
728 tsk->thread.pfault_wait = 0;
729 list_del(&tsk->thread.list);
730 wake_up_process(tsk);
731 put_task_struct(tsk);
732 } else {
733 /* Completion interrupt was faster than initial
734 * interrupt. Set pfault_wait to -1 so the initial
735 * interrupt doesn't put the task to sleep.
736 * If the task is not running, ignore the completion
737 * interrupt since it must be a leftover of a PFAULT
738 * CANCEL operation which didn't remove all pending
739 * completion interrupts. */
740 if (tsk->state == TASK_RUNNING)
741 tsk->thread.pfault_wait = -1;
742 }
743 } else {
744 /* signal bit not set -> a real page is missing. */
745 if (WARN_ON_ONCE(tsk != current))
746 goto out;
747 if (tsk->thread.pfault_wait == 1) {
748 /* Already on the list with a reference: put to sleep */
749 goto block;
750 } else if (tsk->thread.pfault_wait == -1) {
751 /* Completion interrupt was faster than the initial
752 * interrupt (pfault_wait == -1). Set pfault_wait
753 * back to zero and exit. */
754 tsk->thread.pfault_wait = 0;
755 } else {
756 /* Initial interrupt arrived before completion
757 * interrupt. Let the task sleep.
758 * An extra task reference is needed since a different
759 * cpu may set the task state to TASK_RUNNING again
760 * before the scheduler is reached. */
761 get_task_struct(tsk);
762 tsk->thread.pfault_wait = 1;
763 list_add(&tsk->thread.list, &pfault_list);
764 block:
765 /* Since this must be a userspace fault, there
766 * is no kernel task state to trample. Rely on the
767 * return to userspace schedule() to block. */
768 __set_current_state(TASK_UNINTERRUPTIBLE);
769 set_tsk_need_resched(tsk);
770 set_preempt_need_resched();
771 }
772 }
773 out:
774 spin_unlock(&pfault_lock);
775 put_task_struct(tsk);
776 }
777
pfault_cpu_dead(unsigned int cpu)778 static int pfault_cpu_dead(unsigned int cpu)
779 {
780 struct thread_struct *thread, *next;
781 struct task_struct *tsk;
782
783 spin_lock_irq(&pfault_lock);
784 list_for_each_entry_safe(thread, next, &pfault_list, list) {
785 thread->pfault_wait = 0;
786 list_del(&thread->list);
787 tsk = container_of(thread, struct task_struct, thread);
788 wake_up_process(tsk);
789 put_task_struct(tsk);
790 }
791 spin_unlock_irq(&pfault_lock);
792 return 0;
793 }
794
pfault_irq_init(void)795 static int __init pfault_irq_init(void)
796 {
797 int rc;
798
799 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt);
800 if (rc)
801 goto out_extint;
802 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP;
803 if (rc)
804 goto out_pfault;
805 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL);
806 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead",
807 NULL, pfault_cpu_dead);
808 return 0;
809
810 out_pfault:
811 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt);
812 out_extint:
813 pfault_disable = 1;
814 return rc;
815 }
816 early_initcall(pfault_irq_init);
817
818 #endif /* CONFIG_PFAULT */
819