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/mmu_context.h>
14 #include <linux/perf_event.h>
15 #include <linux/signal.h>
16 #include <linux/sched.h>
17 #include <linux/sched/debug.h>
18 #include <linux/jump_label.h>
19 #include <linux/kernel.h>
20 #include <linux/errno.h>
21 #include <linux/string.h>
22 #include <linux/types.h>
23 #include <linux/ptrace.h>
24 #include <linux/mman.h>
25 #include <linux/mm.h>
26 #include <linux/compat.h>
27 #include <linux/smp.h>
28 #include <linux/kdebug.h>
29 #include <linux/init.h>
30 #include <linux/console.h>
31 #include <linux/extable.h>
32 #include <linux/hardirq.h>
33 #include <linux/kprobes.h>
34 #include <linux/uaccess.h>
35 #include <linux/hugetlb.h>
36 #include <linux/kfence.h>
37 #include <asm/asm-extable.h>
38 #include <asm/asm-offsets.h>
39 #include <asm/ptrace.h>
40 #include <asm/fault.h>
41 #include <asm/diag.h>
42 #include <asm/gmap.h>
43 #include <asm/irq.h>
44 #include <asm/facility.h>
45 #include <asm/uv.h>
46 #include "../kernel/entry.h"
47
48 enum fault_type {
49 KERNEL_FAULT,
50 USER_FAULT,
51 GMAP_FAULT,
52 };
53
54 static DEFINE_STATIC_KEY_FALSE(have_store_indication);
55
56 static int __init fault_init(void)
57 {
58 if (test_facility(75))
59 static_branch_enable(&have_store_indication);
60 return 0;
61 }
62 early_initcall(fault_init);
63
64 /*
65 * Find out which address space caused the exception.
66 */
67 static enum fault_type get_fault_type(struct pt_regs *regs)
68 {
69 union teid teid = { .val = regs->int_parm_long };
70 struct gmap *gmap;
71
72 if (likely(teid.as == PSW_BITS_AS_PRIMARY)) {
73 if (user_mode(regs))
74 return USER_FAULT;
75 if (!IS_ENABLED(CONFIG_PGSTE))
76 return KERNEL_FAULT;
77 gmap = (struct gmap *)get_lowcore()->gmap;
78 if (gmap && gmap->asce == regs->cr1)
79 return GMAP_FAULT;
80 return KERNEL_FAULT;
81 }
82 if (teid.as == PSW_BITS_AS_SECONDARY)
83 return USER_FAULT;
84 /* Access register mode, not used in the kernel */
85 if (teid.as == PSW_BITS_AS_ACCREG)
86 return USER_FAULT;
87 /* Home space -> access via kernel ASCE */
88 return KERNEL_FAULT;
89 }
90
91 static unsigned long get_fault_address(struct pt_regs *regs)
92 {
93 union teid teid = { .val = regs->int_parm_long };
94
95 return teid.addr * PAGE_SIZE;
96 }
97
98 static __always_inline bool fault_is_write(struct pt_regs *regs)
99 {
100 union teid teid = { .val = regs->int_parm_long };
101
102 if (static_branch_likely(&have_store_indication))
103 return teid.fsi == TEID_FSI_STORE;
104 return false;
105 }
106
107 static void dump_pagetable(unsigned long asce, unsigned long address)
108 {
109 unsigned long entry, *table = __va(asce & _ASCE_ORIGIN);
110
111 pr_alert("AS:%016lx ", asce);
112 switch (asce & _ASCE_TYPE_MASK) {
113 case _ASCE_TYPE_REGION1:
114 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT;
115 if (get_kernel_nofault(entry, table))
116 goto bad;
117 pr_cont("R1:%016lx ", entry);
118 if (entry & _REGION_ENTRY_INVALID)
119 goto out;
120 table = __va(entry & _REGION_ENTRY_ORIGIN);
121 fallthrough;
122 case _ASCE_TYPE_REGION2:
123 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT;
124 if (get_kernel_nofault(entry, table))
125 goto bad;
126 pr_cont("R2:%016lx ", entry);
127 if (entry & _REGION_ENTRY_INVALID)
128 goto out;
129 table = __va(entry & _REGION_ENTRY_ORIGIN);
130 fallthrough;
131 case _ASCE_TYPE_REGION3:
132 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT;
133 if (get_kernel_nofault(entry, table))
134 goto bad;
135 pr_cont("R3:%016lx ", entry);
136 if (entry & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE))
137 goto out;
138 table = __va(entry & _REGION_ENTRY_ORIGIN);
139 fallthrough;
140 case _ASCE_TYPE_SEGMENT:
141 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
142 if (get_kernel_nofault(entry, table))
143 goto bad;
144 pr_cont("S:%016lx ", entry);
145 if (entry & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE))
146 goto out;
147 table = __va(entry & _SEGMENT_ENTRY_ORIGIN);
148 }
149 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT;
150 if (get_kernel_nofault(entry, table))
151 goto bad;
152 pr_cont("P:%016lx ", entry);
153 out:
154 pr_cont("\n");
155 return;
156 bad:
157 pr_cont("BAD\n");
158 }
159
160 static void dump_fault_info(struct pt_regs *regs)
161 {
162 union teid teid = { .val = regs->int_parm_long };
163 unsigned long asce;
164
165 pr_alert("Failing address: %016lx TEID: %016lx\n",
166 get_fault_address(regs), teid.val);
167 pr_alert("Fault in ");
168 switch (teid.as) {
169 case PSW_BITS_AS_HOME:
170 pr_cont("home space ");
171 break;
172 case PSW_BITS_AS_SECONDARY:
173 pr_cont("secondary space ");
174 break;
175 case PSW_BITS_AS_ACCREG:
176 pr_cont("access register ");
177 break;
178 case PSW_BITS_AS_PRIMARY:
179 pr_cont("primary space ");
180 break;
181 }
182 pr_cont("mode while using ");
183 switch (get_fault_type(regs)) {
184 case USER_FAULT:
185 asce = get_lowcore()->user_asce.val;
186 pr_cont("user ");
187 break;
188 case GMAP_FAULT:
189 asce = ((struct gmap *)get_lowcore()->gmap)->asce;
190 pr_cont("gmap ");
191 break;
192 case KERNEL_FAULT:
193 asce = get_lowcore()->kernel_asce.val;
194 pr_cont("kernel ");
195 break;
196 default:
197 unreachable();
198 }
199 pr_cont("ASCE.\n");
200 dump_pagetable(asce, get_fault_address(regs));
201 }
202
203 int show_unhandled_signals = 1;
204
205 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault)
206 {
207 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
208
209 if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
210 return;
211 if (!unhandled_signal(current, signr))
212 return;
213 if (!__ratelimit(&rs))
214 return;
215 pr_alert("User process fault: interruption code %04x ilc:%d ",
216 regs->int_code & 0xffff, regs->int_code >> 17);
217 print_vma_addr(KERN_CONT "in ", regs->psw.addr);
218 pr_cont("\n");
219 if (is_mm_fault)
220 dump_fault_info(regs);
221 show_regs(regs);
222 }
223
224 static void do_sigsegv(struct pt_regs *regs, int si_code)
225 {
226 report_user_fault(regs, SIGSEGV, 1);
227 force_sig_fault(SIGSEGV, si_code, (void __user *)get_fault_address(regs));
228 }
229
230 static void handle_fault_error_nolock(struct pt_regs *regs, int si_code)
231 {
232 enum fault_type fault_type;
233 unsigned long address;
234 bool is_write;
235
236 if (user_mode(regs)) {
237 if (WARN_ON_ONCE(!si_code))
238 si_code = SEGV_MAPERR;
239 return do_sigsegv(regs, si_code);
240 }
241 if (fixup_exception(regs))
242 return;
243 fault_type = get_fault_type(regs);
244 if (fault_type == KERNEL_FAULT) {
245 address = get_fault_address(regs);
246 is_write = fault_is_write(regs);
247 if (kfence_handle_page_fault(address, is_write, regs))
248 return;
249 }
250 if (fault_type == KERNEL_FAULT)
251 pr_alert("Unable to handle kernel pointer dereference in virtual kernel address space\n");
252 else
253 pr_alert("Unable to handle kernel paging request in virtual user address space\n");
254 dump_fault_info(regs);
255 die(regs, "Oops");
256 }
257
258 static void handle_fault_error(struct pt_regs *regs, int si_code)
259 {
260 struct mm_struct *mm = current->mm;
261
262 mmap_read_unlock(mm);
263 handle_fault_error_nolock(regs, si_code);
264 }
265
266 static void do_sigbus(struct pt_regs *regs)
267 {
268 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)get_fault_address(regs));
269 }
270
271 /*
272 * This routine handles page faults. It determines the address,
273 * and the problem, and then passes it off to one of the appropriate
274 * routines.
275 *
276 * interruption code (int_code):
277 * 04 Protection -> Write-Protection (suppression)
278 * 10 Segment translation -> Not present (nullification)
279 * 11 Page translation -> Not present (nullification)
280 * 3b Region third trans. -> Not present (nullification)
281 */
282 static void do_exception(struct pt_regs *regs, int access)
283 {
284 struct vm_area_struct *vma;
285 unsigned long address;
286 struct mm_struct *mm;
287 enum fault_type type;
288 unsigned int flags;
289 struct gmap *gmap;
290 vm_fault_t fault;
291 bool is_write;
292
293 /*
294 * The instruction that caused the program check has
295 * been nullified. Don't signal single step via SIGTRAP.
296 */
297 clear_thread_flag(TIF_PER_TRAP);
298 if (kprobe_page_fault(regs, 14))
299 return;
300 mm = current->mm;
301 address = get_fault_address(regs);
302 is_write = fault_is_write(regs);
303 type = get_fault_type(regs);
304 switch (type) {
305 case KERNEL_FAULT:
306 return handle_fault_error_nolock(regs, 0);
307 case USER_FAULT:
308 case GMAP_FAULT:
309 if (faulthandler_disabled() || !mm)
310 return handle_fault_error_nolock(regs, 0);
311 break;
312 }
313 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
314 flags = FAULT_FLAG_DEFAULT;
315 if (user_mode(regs))
316 flags |= FAULT_FLAG_USER;
317 if (is_write)
318 access = VM_WRITE;
319 if (access == VM_WRITE)
320 flags |= FAULT_FLAG_WRITE;
321 if (!(flags & FAULT_FLAG_USER))
322 goto lock_mmap;
323 vma = lock_vma_under_rcu(mm, address);
324 if (!vma)
325 goto lock_mmap;
326 if (!(vma->vm_flags & access)) {
327 vma_end_read(vma);
328 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
329 return handle_fault_error_nolock(regs, SEGV_ACCERR);
330 }
331 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
332 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
333 vma_end_read(vma);
334 if (!(fault & VM_FAULT_RETRY)) {
335 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
336 if (unlikely(fault & VM_FAULT_ERROR))
337 goto error;
338 return;
339 }
340 count_vm_vma_lock_event(VMA_LOCK_RETRY);
341 if (fault & VM_FAULT_MAJOR)
342 flags |= FAULT_FLAG_TRIED;
343
344 /* Quick path to respond to signals */
345 if (fault_signal_pending(fault, regs)) {
346 if (!user_mode(regs))
347 handle_fault_error_nolock(regs, 0);
348 return;
349 }
350 lock_mmap:
351 mmap_read_lock(mm);
352 gmap = NULL;
353 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) {
354 gmap = (struct gmap *)get_lowcore()->gmap;
355 current->thread.gmap_addr = address;
356 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE);
357 current->thread.gmap_int_code = regs->int_code & 0xffff;
358 address = __gmap_translate(gmap, address);
359 if (address == -EFAULT)
360 return handle_fault_error(regs, SEGV_MAPERR);
361 if (gmap->pfault_enabled)
362 flags |= FAULT_FLAG_RETRY_NOWAIT;
363 }
364 retry:
365 vma = find_vma(mm, address);
366 if (!vma)
367 return handle_fault_error(regs, SEGV_MAPERR);
368 if (unlikely(vma->vm_start > address)) {
369 if (!(vma->vm_flags & VM_GROWSDOWN))
370 return handle_fault_error(regs, SEGV_MAPERR);
371 vma = expand_stack(mm, address);
372 if (!vma)
373 return handle_fault_error_nolock(regs, SEGV_MAPERR);
374 }
375 if (unlikely(!(vma->vm_flags & access)))
376 return handle_fault_error(regs, SEGV_ACCERR);
377 fault = handle_mm_fault(vma, address, flags, regs);
378 if (fault_signal_pending(fault, regs)) {
379 if (flags & FAULT_FLAG_RETRY_NOWAIT)
380 mmap_read_unlock(mm);
381 if (!user_mode(regs))
382 handle_fault_error_nolock(regs, 0);
383 return;
384 }
385 /* The fault is fully completed (including releasing mmap lock) */
386 if (fault & VM_FAULT_COMPLETED) {
387 if (gmap) {
388 mmap_read_lock(mm);
389 goto gmap;
390 }
391 return;
392 }
393 if (unlikely(fault & VM_FAULT_ERROR)) {
394 mmap_read_unlock(mm);
395 goto error;
396 }
397 if (fault & VM_FAULT_RETRY) {
398 if (IS_ENABLED(CONFIG_PGSTE) && gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) {
399 /*
400 * FAULT_FLAG_RETRY_NOWAIT has been set,
401 * mmap_lock has not been released
402 */
403 current->thread.gmap_pfault = 1;
404 return handle_fault_error(regs, 0);
405 }
406 flags &= ~FAULT_FLAG_RETRY_NOWAIT;
407 flags |= FAULT_FLAG_TRIED;
408 mmap_read_lock(mm);
409 goto retry;
410 }
411 gmap:
412 if (IS_ENABLED(CONFIG_PGSTE) && gmap) {
413 address = __gmap_link(gmap, current->thread.gmap_addr,
414 address);
415 if (address == -EFAULT)
416 return handle_fault_error(regs, SEGV_MAPERR);
417 if (address == -ENOMEM) {
418 fault = VM_FAULT_OOM;
419 mmap_read_unlock(mm);
420 goto error;
421 }
422 }
423 mmap_read_unlock(mm);
424 return;
425 error:
426 if (fault & VM_FAULT_OOM) {
427 if (!user_mode(regs))
428 handle_fault_error_nolock(regs, 0);
429 else
430 pagefault_out_of_memory();
431 } else if (fault & VM_FAULT_SIGSEGV) {
432 if (!user_mode(regs))
433 handle_fault_error_nolock(regs, 0);
434 else
435 do_sigsegv(regs, SEGV_MAPERR);
436 } else if (fault & (VM_FAULT_SIGBUS | VM_FAULT_HWPOISON)) {
437 if (!user_mode(regs))
438 handle_fault_error_nolock(regs, 0);
439 else
440 do_sigbus(regs);
441 } else {
442 pr_emerg("Unexpected fault flags: %08x\n", fault);
443 BUG();
444 }
445 }
446
447 void do_protection_exception(struct pt_regs *regs)
448 {
449 union teid teid = { .val = regs->int_parm_long };
450
451 /*
452 * Protection exceptions are suppressing, decrement psw address.
453 * The exception to this rule are aborted transactions, for these
454 * the PSW already points to the correct location.
455 */
456 if (!(regs->int_code & 0x200))
457 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
458 /*
459 * Check for low-address protection. This needs to be treated
460 * as a special case because the translation exception code
461 * field is not guaranteed to contain valid data in this case.
462 */
463 if (unlikely(!teid.b61)) {
464 if (user_mode(regs)) {
465 /* Low-address protection in user mode: cannot happen */
466 die(regs, "Low-address protection");
467 }
468 /*
469 * Low-address protection in kernel mode means
470 * NULL pointer write access in kernel mode.
471 */
472 return handle_fault_error_nolock(regs, 0);
473 }
474 if (unlikely(MACHINE_HAS_NX && teid.b56)) {
475 regs->int_parm_long = (teid.addr * PAGE_SIZE) | (regs->psw.addr & PAGE_MASK);
476 return handle_fault_error_nolock(regs, SEGV_ACCERR);
477 }
478 do_exception(regs, VM_WRITE);
479 }
480 NOKPROBE_SYMBOL(do_protection_exception);
481
482 void do_dat_exception(struct pt_regs *regs)
483 {
484 do_exception(regs, VM_ACCESS_FLAGS);
485 }
486 NOKPROBE_SYMBOL(do_dat_exception);
487
488 #if IS_ENABLED(CONFIG_PGSTE)
489
490 void do_secure_storage_access(struct pt_regs *regs)
491 {
492 union teid teid = { .val = regs->int_parm_long };
493 unsigned long addr = get_fault_address(regs);
494 struct vm_area_struct *vma;
495 struct mm_struct *mm;
496 struct folio *folio;
497 struct page *page;
498 struct gmap *gmap;
499 int rc;
500
501 /*
502 * Bit 61 indicates if the address is valid, if it is not the
503 * kernel should be stopped or SIGSEGV should be sent to the
504 * process. Bit 61 is not reliable without the misc UV feature,
505 * therefore this needs to be checked too.
506 */
507 if (uv_has_feature(BIT_UV_FEAT_MISC) && !teid.b61) {
508 /*
509 * When this happens, userspace did something that it
510 * was not supposed to do, e.g. branching into secure
511 * memory. Trigger a segmentation fault.
512 */
513 if (user_mode(regs)) {
514 send_sig(SIGSEGV, current, 0);
515 return;
516 }
517 /*
518 * The kernel should never run into this case and
519 * there is no way out of this situation.
520 */
521 panic("Unexpected PGM 0x3d with TEID bit 61=0");
522 }
523 switch (get_fault_type(regs)) {
524 case GMAP_FAULT:
525 mm = current->mm;
526 gmap = (struct gmap *)get_lowcore()->gmap;
527 mmap_read_lock(mm);
528 addr = __gmap_translate(gmap, addr);
529 mmap_read_unlock(mm);
530 if (IS_ERR_VALUE(addr))
531 return handle_fault_error_nolock(regs, SEGV_MAPERR);
532 fallthrough;
533 case USER_FAULT:
534 mm = current->mm;
535 mmap_read_lock(mm);
536 vma = find_vma(mm, addr);
537 if (!vma)
538 return handle_fault_error(regs, SEGV_MAPERR);
539 page = follow_page(vma, addr, FOLL_WRITE | FOLL_GET);
540 if (IS_ERR_OR_NULL(page)) {
541 mmap_read_unlock(mm);
542 break;
543 }
544 folio = page_folio(page);
545 if (arch_make_folio_accessible(folio))
546 send_sig(SIGSEGV, current, 0);
547 folio_put(folio);
548 mmap_read_unlock(mm);
549 break;
550 case KERNEL_FAULT:
551 folio = phys_to_folio(addr);
552 if (unlikely(!folio_try_get(folio)))
553 break;
554 rc = arch_make_folio_accessible(folio);
555 folio_put(folio);
556 if (rc)
557 BUG();
558 break;
559 default:
560 unreachable();
561 }
562 }
563 NOKPROBE_SYMBOL(do_secure_storage_access);
564
565 void do_non_secure_storage_access(struct pt_regs *regs)
566 {
567 struct gmap *gmap = (struct gmap *)get_lowcore()->gmap;
568 unsigned long gaddr = get_fault_address(regs);
569
570 if (WARN_ON_ONCE(get_fault_type(regs) != GMAP_FAULT))
571 return handle_fault_error_nolock(regs, SEGV_MAPERR);
572 if (gmap_convert_to_secure(gmap, gaddr) == -EINVAL)
573 send_sig(SIGSEGV, current, 0);
574 }
575 NOKPROBE_SYMBOL(do_non_secure_storage_access);
576
577 void do_secure_storage_violation(struct pt_regs *regs)
578 {
579 struct gmap *gmap = (struct gmap *)get_lowcore()->gmap;
580 unsigned long gaddr = get_fault_address(regs);
581
582 /*
583 * If the VM has been rebooted, its address space might still contain
584 * secure pages from the previous boot.
585 * Clear the page so it can be reused.
586 */
587 if (!gmap_destroy_page(gmap, gaddr))
588 return;
589 /*
590 * Either KVM messed up the secure guest mapping or the same
591 * page is mapped into multiple secure guests.
592 *
593 * This exception is only triggered when a guest 2 is running
594 * and can therefore never occur in kernel context.
595 */
596 pr_warn_ratelimited("Secure storage violation in task: %s, pid %d\n",
597 current->comm, current->pid);
598 send_sig(SIGSEGV, current, 0);
599 }
600
601 #endif /* CONFIG_PGSTE */
602
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