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, 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, 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
224static 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
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(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, (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, 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		goto lock_mmap;
329	}
330	fault = handle_mm_fault(vma, address, 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, regs)) {
345		if (!user_mode(regs))
346			handle_fault_error_nolock(regs, 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, 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, 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, regs)) {
378		if (flags & FAULT_FLAG_RETRY_NOWAIT)
379			mmap_read_unlock(mm);
380		if (!user_mode(regs))
381			handle_fault_error_nolock(regs, 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, 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, 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, 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, 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, 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