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
48enum fault_type {
49 KERNEL_FAULT,
50 USER_FAULT,
51 GMAP_FAULT,
52};
53
54static DEFINE_STATIC_KEY_FALSE(have_store_indication);
55
56static int __init fault_init(void)
57{
58 if (test_facility(75))
59 static_branch_enable(&have_store_indication);
60 return 0;
61}
62early_initcall(fault_init);
63
64/*
65 * Find out which address space caused the exception.
66 */
67static 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 *)S390_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
91static 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
98static __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
107static 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);
153out:
154 pr_cont("\n");
155 return;
156bad:
157 pr_cont("BAD\n");
158}
159
160static 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 = S390_lowcore.user_asce.val;
186 pr_cont("user ");
187 break;
188 case GMAP_FAULT:
189 asce = ((struct gmap *)S390_lowcore.gmap)->asce;
190 pr_cont("gmap ");
191 break;
192 case KERNEL_FAULT:
193 asce = S390_lowcore.kernel_asce.val;
194 pr_cont("kernel ");
195 break;
196 default:
197 unreachable();
198 }
199 pr_cont("ASCE.\n");
200 dump_pagetable(asce, address: get_fault_address(regs));
201}
202
203int show_unhandled_signals = 1;
204
205void 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, sig: 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 ", rip: regs->psw.addr);
218 pr_cont("\n");
219 if (is_mm_fault)
220 dump_fault_info(regs);
221 show_regs(regs);
222}
223
224static void do_sigsegv(struct pt_regs *regs, int si_code)
225{
226 report_user_fault(regs, SIGSEGV, is_mm_fault: 1);
227 force_sig_fault(SIGSEGV, code: si_code, addr: (void __user *)get_fault_address(regs));
228}
229
230static 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(addr: 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
258static 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
266static void do_sigbus(struct pt_regs *regs)
267{
268 force_sig_fault(SIGBUS, BUS_ADRERR, addr: (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 */
282static 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, trap: 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, si_code: 0);
307 case USER_FAULT:
308 case GMAP_FAULT:
309 if (faulthandler_disabled() || !mm)
310 return handle_fault_error_nolock(regs, si_code: 0);
311 break;
312 }
313 perf_sw_event(event_id: PERF_COUNT_SW_PAGE_FAULTS, nr: 1, regs, addr: 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 goto lock_mmap;
329 }
330 fault = handle_mm_fault(vma, address, flags: flags | FAULT_FLAG_VMA_LOCK, regs);
331 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
332 vma_end_read(vma);
333 if (!(fault & VM_FAULT_RETRY)) {
334 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
335 if (unlikely(fault & VM_FAULT_ERROR))
336 goto error;
337 return;
338 }
339 count_vm_vma_lock_event(VMA_LOCK_RETRY);
340 if (fault & VM_FAULT_MAJOR)
341 flags |= FAULT_FLAG_TRIED;
342
343 /* Quick path to respond to signals */
344 if (fault_signal_pending(fault_flags: fault, regs)) {
345 if (!user_mode(regs))
346 handle_fault_error_nolock(regs, si_code: 0);
347 return;
348 }
349lock_mmap:
350 mmap_read_lock(mm);
351 gmap = NULL;
352 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) {
353 gmap = (struct gmap *)S390_lowcore.gmap;
354 current->thread.gmap_addr = address;
355 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE);
356 current->thread.gmap_int_code = regs->int_code & 0xffff;
357 address = __gmap_translate(gmap, address);
358 if (address == -EFAULT)
359 return handle_fault_error(regs, SEGV_MAPERR);
360 if (gmap->pfault_enabled)
361 flags |= FAULT_FLAG_RETRY_NOWAIT;
362 }
363retry:
364 vma = find_vma(mm, addr: address);
365 if (!vma)
366 return handle_fault_error(regs, SEGV_MAPERR);
367 if (unlikely(vma->vm_start > address)) {
368 if (!(vma->vm_flags & VM_GROWSDOWN))
369 return handle_fault_error(regs, SEGV_MAPERR);
370 vma = expand_stack(mm, addr: address);
371 if (!vma)
372 return handle_fault_error_nolock(regs, SEGV_MAPERR);
373 }
374 if (unlikely(!(vma->vm_flags & access)))
375 return handle_fault_error(regs, SEGV_ACCERR);
376 fault = handle_mm_fault(vma, address, flags, regs);
377 if (fault_signal_pending(fault_flags: fault, regs)) {
378 if (flags & FAULT_FLAG_RETRY_NOWAIT)
379 mmap_read_unlock(mm);
380 if (!user_mode(regs))
381 handle_fault_error_nolock(regs, si_code: 0);
382 return;
383 }
384 /* The fault is fully completed (including releasing mmap lock) */
385 if (fault & VM_FAULT_COMPLETED) {
386 if (gmap) {
387 mmap_read_lock(mm);
388 goto gmap;
389 }
390 return;
391 }
392 if (unlikely(fault & VM_FAULT_ERROR)) {
393 mmap_read_unlock(mm);
394 goto error;
395 }
396 if (fault & VM_FAULT_RETRY) {
397 if (IS_ENABLED(CONFIG_PGSTE) && gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) {
398 /*
399 * FAULT_FLAG_RETRY_NOWAIT has been set,
400 * mmap_lock has not been released
401 */
402 current->thread.gmap_pfault = 1;
403 return handle_fault_error(regs, si_code: 0);
404 }
405 flags &= ~FAULT_FLAG_RETRY_NOWAIT;
406 flags |= FAULT_FLAG_TRIED;
407 mmap_read_lock(mm);
408 goto retry;
409 }
410gmap:
411 if (IS_ENABLED(CONFIG_PGSTE) && gmap) {
412 address = __gmap_link(gmap, current->thread.gmap_addr,
413 address);
414 if (address == -EFAULT)
415 return handle_fault_error(regs, SEGV_MAPERR);
416 if (address == -ENOMEM) {
417 fault = VM_FAULT_OOM;
418 mmap_read_unlock(mm);
419 goto error;
420 }
421 }
422 mmap_read_unlock(mm);
423 return;
424error:
425 if (fault & VM_FAULT_OOM) {
426 if (!user_mode(regs))
427 handle_fault_error_nolock(regs, si_code: 0);
428 else
429 pagefault_out_of_memory();
430 } else if (fault & VM_FAULT_SIGSEGV) {
431 if (!user_mode(regs))
432 handle_fault_error_nolock(regs, si_code: 0);
433 else
434 do_sigsegv(regs, SEGV_MAPERR);
435 } else if (fault & VM_FAULT_SIGBUS) {
436 if (!user_mode(regs))
437 handle_fault_error_nolock(regs, si_code: 0);
438 else
439 do_sigbus(regs);
440 } else {
441 BUG();
442 }
443}
444
445void do_protection_exception(struct pt_regs *regs)
446{
447 union teid teid = { .val = regs->int_parm_long };
448
449 /*
450 * Protection exceptions are suppressing, decrement psw address.
451 * The exception to this rule are aborted transactions, for these
452 * the PSW already points to the correct location.
453 */
454 if (!(regs->int_code & 0x200))
455 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
456 /*
457 * Check for low-address protection. This needs to be treated
458 * as a special case because the translation exception code
459 * field is not guaranteed to contain valid data in this case.
460 */
461 if (unlikely(!teid.b61)) {
462 if (user_mode(regs)) {
463 /* Low-address protection in user mode: cannot happen */
464 die(regs, "Low-address protection");
465 }
466 /*
467 * Low-address protection in kernel mode means
468 * NULL pointer write access in kernel mode.
469 */
470 return handle_fault_error_nolock(regs, si_code: 0);
471 }
472 if (unlikely(MACHINE_HAS_NX && teid.b56)) {
473 regs->int_parm_long = (teid.addr * PAGE_SIZE) | (regs->psw.addr & PAGE_MASK);
474 return handle_fault_error_nolock(regs, SEGV_ACCERR);
475 }
476 do_exception(regs, VM_WRITE);
477}
478NOKPROBE_SYMBOL(do_protection_exception);
479
480void do_dat_exception(struct pt_regs *regs)
481{
482 do_exception(regs, VM_ACCESS_FLAGS);
483}
484NOKPROBE_SYMBOL(do_dat_exception);
485
486#if IS_ENABLED(CONFIG_PGSTE)
487
488void do_secure_storage_access(struct pt_regs *regs)
489{
490 union teid teid = { .val = regs->int_parm_long };
491 unsigned long addr = get_fault_address(regs);
492 struct vm_area_struct *vma;
493 struct mm_struct *mm;
494 struct page *page;
495 struct gmap *gmap;
496 int rc;
497
498 /*
499 * Bit 61 indicates if the address is valid, if it is not the
500 * kernel should be stopped or SIGSEGV should be sent to the
501 * process. Bit 61 is not reliable without the misc UV feature,
502 * therefore this needs to be checked too.
503 */
504 if (uv_has_feature(BIT_UV_FEAT_MISC) && !teid.b61) {
505 /*
506 * When this happens, userspace did something that it
507 * was not supposed to do, e.g. branching into secure
508 * memory. Trigger a segmentation fault.
509 */
510 if (user_mode(regs)) {
511 send_sig(SIGSEGV, current, 0);
512 return;
513 }
514 /*
515 * The kernel should never run into this case and
516 * there is no way out of this situation.
517 */
518 panic("Unexpected PGM 0x3d with TEID bit 61=0");
519 }
520 switch (get_fault_type(regs)) {
521 case GMAP_FAULT:
522 mm = current->mm;
523 gmap = (struct gmap *)S390_lowcore.gmap;
524 mmap_read_lock(mm);
525 addr = __gmap_translate(gmap, addr);
526 mmap_read_unlock(mm);
527 if (IS_ERR_VALUE(addr))
528 return handle_fault_error_nolock(regs, SEGV_MAPERR);
529 fallthrough;
530 case USER_FAULT:
531 mm = current->mm;
532 mmap_read_lock(mm);
533 vma = find_vma(mm, addr);
534 if (!vma)
535 return handle_fault_error(regs, SEGV_MAPERR);
536 page = follow_page(vma, addr, FOLL_WRITE | FOLL_GET);
537 if (IS_ERR_OR_NULL(page)) {
538 mmap_read_unlock(mm);
539 break;
540 }
541 if (arch_make_page_accessible(page))
542 send_sig(SIGSEGV, current, 0);
543 put_page(page);
544 mmap_read_unlock(mm);
545 break;
546 case KERNEL_FAULT:
547 page = phys_to_page(addr);
548 if (unlikely(!try_get_page(page)))
549 break;
550 rc = arch_make_page_accessible(page);
551 put_page(page);
552 if (rc)
553 BUG();
554 break;
555 default:
556 unreachable();
557 }
558}
559NOKPROBE_SYMBOL(do_secure_storage_access);
560
561void do_non_secure_storage_access(struct pt_regs *regs)
562{
563 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap;
564 unsigned long gaddr = get_fault_address(regs);
565
566 if (WARN_ON_ONCE(get_fault_type(regs) != GMAP_FAULT))
567 return handle_fault_error_nolock(regs, SEGV_MAPERR);
568 if (gmap_convert_to_secure(gmap, gaddr) == -EINVAL)
569 send_sig(SIGSEGV, current, 0);
570}
571NOKPROBE_SYMBOL(do_non_secure_storage_access);
572
573void do_secure_storage_violation(struct pt_regs *regs)
574{
575 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap;
576 unsigned long gaddr = get_fault_address(regs);
577
578 /*
579 * If the VM has been rebooted, its address space might still contain
580 * secure pages from the previous boot.
581 * Clear the page so it can be reused.
582 */
583 if (!gmap_destroy_page(gmap, gaddr))
584 return;
585 /*
586 * Either KVM messed up the secure guest mapping or the same
587 * page is mapped into multiple secure guests.
588 *
589 * This exception is only triggered when a guest 2 is running
590 * and can therefore never occur in kernel context.
591 */
592 pr_warn_ratelimited("Secure storage violation in task: %s, pid %d\n",
593 current->comm, current->pid);
594 send_sig(SIGSEGV, current, 0);
595}
596
597#endif /* CONFIG_PGSTE */
598

source code of linux/arch/s390/mm/fault.c