xref: /openbmc/linux/arch/s390/mm/fault.c (revision b34e08d5)
1 /*
2  *  S390 version
3  *    Copyright IBM Corp. 1999
4  *    Author(s): Hartmut Penner (hp@de.ibm.com)
5  *               Ulrich Weigand (uweigand@de.ibm.com)
6  *
7  *  Derived from "arch/i386/mm/fault.c"
8  *    Copyright (C) 1995  Linus Torvalds
9  */
10 
11 #include <linux/kernel_stat.h>
12 #include <linux/perf_event.h>
13 #include <linux/signal.h>
14 #include <linux/sched.h>
15 #include <linux/kernel.h>
16 #include <linux/errno.h>
17 #include <linux/string.h>
18 #include <linux/types.h>
19 #include <linux/ptrace.h>
20 #include <linux/mman.h>
21 #include <linux/mm.h>
22 #include <linux/compat.h>
23 #include <linux/smp.h>
24 #include <linux/kdebug.h>
25 #include <linux/init.h>
26 #include <linux/console.h>
27 #include <linux/module.h>
28 #include <linux/hardirq.h>
29 #include <linux/kprobes.h>
30 #include <linux/uaccess.h>
31 #include <linux/hugetlb.h>
32 #include <asm/asm-offsets.h>
33 #include <asm/pgtable.h>
34 #include <asm/irq.h>
35 #include <asm/mmu_context.h>
36 #include <asm/facility.h>
37 #include "../kernel/entry.h"
38 
39 #ifndef CONFIG_64BIT
40 #define __FAIL_ADDR_MASK 0x7ffff000
41 #define __SUBCODE_MASK 0x0200
42 #define __PF_RES_FIELD 0ULL
43 #else /* CONFIG_64BIT */
44 #define __FAIL_ADDR_MASK -4096L
45 #define __SUBCODE_MASK 0x0600
46 #define __PF_RES_FIELD 0x8000000000000000ULL
47 #endif /* CONFIG_64BIT */
48 
49 #define VM_FAULT_BADCONTEXT	0x010000
50 #define VM_FAULT_BADMAP		0x020000
51 #define VM_FAULT_BADACCESS	0x040000
52 #define VM_FAULT_SIGNAL		0x080000
53 #define VM_FAULT_PFAULT		0x100000
54 
55 static unsigned long store_indication __read_mostly;
56 
57 #ifdef CONFIG_64BIT
58 static int __init fault_init(void)
59 {
60 	if (test_facility(75))
61 		store_indication = 0xc00;
62 	return 0;
63 }
64 early_initcall(fault_init);
65 #endif
66 
67 static inline int notify_page_fault(struct pt_regs *regs)
68 {
69 	int ret = 0;
70 
71 	/* kprobe_running() needs smp_processor_id() */
72 	if (kprobes_built_in() && !user_mode(regs)) {
73 		preempt_disable();
74 		if (kprobe_running() && kprobe_fault_handler(regs, 14))
75 			ret = 1;
76 		preempt_enable();
77 	}
78 	return ret;
79 }
80 
81 
82 /*
83  * Unlock any spinlocks which will prevent us from getting the
84  * message out.
85  */
86 void bust_spinlocks(int yes)
87 {
88 	if (yes) {
89 		oops_in_progress = 1;
90 	} else {
91 		int loglevel_save = console_loglevel;
92 		console_unblank();
93 		oops_in_progress = 0;
94 		/*
95 		 * OK, the message is on the console.  Now we call printk()
96 		 * without oops_in_progress set so that printk will give klogd
97 		 * a poke.  Hold onto your hats...
98 		 */
99 		console_loglevel = 15;
100 		printk(" ");
101 		console_loglevel = loglevel_save;
102 	}
103 }
104 
105 /*
106  * Returns the address space associated with the fault.
107  * Returns 0 for kernel space and 1 for user space.
108  */
109 static inline int user_space_fault(struct pt_regs *regs)
110 {
111 	unsigned long trans_exc_code;
112 
113 	/*
114 	 * The lowest two bits of the translation exception
115 	 * identification indicate which paging table was used.
116 	 */
117 	trans_exc_code = regs->int_parm_long & 3;
118 	if (trans_exc_code == 3) /* home space -> kernel */
119 		return 0;
120 	if (user_mode(regs))
121 		return 1;
122 	if (trans_exc_code == 2) /* secondary space -> set_fs */
123 		return current->thread.mm_segment.ar4;
124 	if (current->flags & PF_VCPU)
125 		return 1;
126 	return 0;
127 }
128 
129 static inline void report_user_fault(struct pt_regs *regs, long signr)
130 {
131 	if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
132 		return;
133 	if (!unhandled_signal(current, signr))
134 		return;
135 	if (!printk_ratelimit())
136 		return;
137 	printk(KERN_ALERT "User process fault: interruption code 0x%X ",
138 	       regs->int_code);
139 	print_vma_addr(KERN_CONT "in ", regs->psw.addr & PSW_ADDR_INSN);
140 	printk(KERN_CONT "\n");
141 	printk(KERN_ALERT "failing address: %lX\n",
142 	       regs->int_parm_long & __FAIL_ADDR_MASK);
143 	show_regs(regs);
144 }
145 
146 /*
147  * Send SIGSEGV to task.  This is an external routine
148  * to keep the stack usage of do_page_fault small.
149  */
150 static noinline void do_sigsegv(struct pt_regs *regs, int si_code)
151 {
152 	struct siginfo si;
153 
154 	report_user_fault(regs, SIGSEGV);
155 	si.si_signo = SIGSEGV;
156 	si.si_code = si_code;
157 	si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK);
158 	force_sig_info(SIGSEGV, &si, current);
159 }
160 
161 static noinline void do_no_context(struct pt_regs *regs)
162 {
163 	const struct exception_table_entry *fixup;
164 	unsigned long address;
165 
166 	/* Are we prepared to handle this kernel fault?  */
167 	fixup = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
168 	if (fixup) {
169 		regs->psw.addr = extable_fixup(fixup) | PSW_ADDR_AMODE;
170 		return;
171 	}
172 
173 	/*
174 	 * Oops. The kernel tried to access some bad page. We'll have to
175 	 * terminate things with extreme prejudice.
176 	 */
177 	address = regs->int_parm_long & __FAIL_ADDR_MASK;
178 	if (!user_space_fault(regs))
179 		printk(KERN_ALERT "Unable to handle kernel pointer dereference"
180 		       " at virtual kernel address %p\n", (void *)address);
181 	else
182 		printk(KERN_ALERT "Unable to handle kernel paging request"
183 		       " at virtual user address %p\n", (void *)address);
184 
185 	die(regs, "Oops");
186 	do_exit(SIGKILL);
187 }
188 
189 static noinline void do_low_address(struct pt_regs *regs)
190 {
191 	/* Low-address protection hit in kernel mode means
192 	   NULL pointer write access in kernel mode.  */
193 	if (regs->psw.mask & PSW_MASK_PSTATE) {
194 		/* Low-address protection hit in user mode 'cannot happen'. */
195 		die (regs, "Low-address protection");
196 		do_exit(SIGKILL);
197 	}
198 
199 	do_no_context(regs);
200 }
201 
202 static noinline void do_sigbus(struct pt_regs *regs)
203 {
204 	struct task_struct *tsk = current;
205 	struct siginfo si;
206 
207 	/*
208 	 * Send a sigbus, regardless of whether we were in kernel
209 	 * or user mode.
210 	 */
211 	si.si_signo = SIGBUS;
212 	si.si_errno = 0;
213 	si.si_code = BUS_ADRERR;
214 	si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK);
215 	force_sig_info(SIGBUS, &si, tsk);
216 }
217 
218 static noinline void do_fault_error(struct pt_regs *regs, int fault)
219 {
220 	int si_code;
221 
222 	switch (fault) {
223 	case VM_FAULT_BADACCESS:
224 	case VM_FAULT_BADMAP:
225 		/* Bad memory access. Check if it is kernel or user space. */
226 		if (user_mode(regs)) {
227 			/* User mode accesses just cause a SIGSEGV */
228 			si_code = (fault == VM_FAULT_BADMAP) ?
229 				SEGV_MAPERR : SEGV_ACCERR;
230 			do_sigsegv(regs, si_code);
231 			return;
232 		}
233 	case VM_FAULT_BADCONTEXT:
234 	case VM_FAULT_PFAULT:
235 		do_no_context(regs);
236 		break;
237 	case VM_FAULT_SIGNAL:
238 		if (!user_mode(regs))
239 			do_no_context(regs);
240 		break;
241 	default: /* fault & VM_FAULT_ERROR */
242 		if (fault & VM_FAULT_OOM) {
243 			if (!user_mode(regs))
244 				do_no_context(regs);
245 			else
246 				pagefault_out_of_memory();
247 		} else if (fault & VM_FAULT_SIGBUS) {
248 			/* Kernel mode? Handle exceptions or die */
249 			if (!user_mode(regs))
250 				do_no_context(regs);
251 			else
252 				do_sigbus(regs);
253 		} else
254 			BUG();
255 		break;
256 	}
257 }
258 
259 /*
260  * This routine handles page faults.  It determines the address,
261  * and the problem, and then passes it off to one of the appropriate
262  * routines.
263  *
264  * interruption code (int_code):
265  *   04       Protection           ->  Write-Protection  (suprression)
266  *   10       Segment translation  ->  Not present       (nullification)
267  *   11       Page translation     ->  Not present       (nullification)
268  *   3b       Region third trans.  ->  Not present       (nullification)
269  */
270 static inline int do_exception(struct pt_regs *regs, int access)
271 {
272 #ifdef CONFIG_PGSTE
273 	struct gmap *gmap;
274 #endif
275 	struct task_struct *tsk;
276 	struct mm_struct *mm;
277 	struct vm_area_struct *vma;
278 	unsigned long trans_exc_code;
279 	unsigned long address;
280 	unsigned int flags;
281 	int fault;
282 
283 	tsk = current;
284 	/*
285 	 * The instruction that caused the program check has
286 	 * been nullified. Don't signal single step via SIGTRAP.
287 	 */
288 	clear_tsk_thread_flag(tsk, TIF_PER_TRAP);
289 
290 	if (notify_page_fault(regs))
291 		return 0;
292 
293 	mm = tsk->mm;
294 	trans_exc_code = regs->int_parm_long;
295 
296 	/*
297 	 * Verify that the fault happened in user space, that
298 	 * we are not in an interrupt and that there is a
299 	 * user context.
300 	 */
301 	fault = VM_FAULT_BADCONTEXT;
302 	if (unlikely(!user_space_fault(regs) || in_atomic() || !mm))
303 		goto out;
304 
305 	address = trans_exc_code & __FAIL_ADDR_MASK;
306 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
307 	flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
308 	if (user_mode(regs))
309 		flags |= FAULT_FLAG_USER;
310 	if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400)
311 		flags |= FAULT_FLAG_WRITE;
312 	down_read(&mm->mmap_sem);
313 
314 #ifdef CONFIG_PGSTE
315 	gmap = (struct gmap *)
316 		((current->flags & PF_VCPU) ? S390_lowcore.gmap : 0);
317 	if (gmap) {
318 		address = __gmap_fault(address, gmap);
319 		if (address == -EFAULT) {
320 			fault = VM_FAULT_BADMAP;
321 			goto out_up;
322 		}
323 		if (address == -ENOMEM) {
324 			fault = VM_FAULT_OOM;
325 			goto out_up;
326 		}
327 		if (gmap->pfault_enabled)
328 			flags |= FAULT_FLAG_RETRY_NOWAIT;
329 	}
330 #endif
331 
332 retry:
333 	fault = VM_FAULT_BADMAP;
334 	vma = find_vma(mm, address);
335 	if (!vma)
336 		goto out_up;
337 
338 	if (unlikely(vma->vm_start > address)) {
339 		if (!(vma->vm_flags & VM_GROWSDOWN))
340 			goto out_up;
341 		if (expand_stack(vma, address))
342 			goto out_up;
343 	}
344 
345 	/*
346 	 * Ok, we have a good vm_area for this memory access, so
347 	 * we can handle it..
348 	 */
349 	fault = VM_FAULT_BADACCESS;
350 	if (unlikely(!(vma->vm_flags & access)))
351 		goto out_up;
352 
353 	if (is_vm_hugetlb_page(vma))
354 		address &= HPAGE_MASK;
355 	/*
356 	 * If for any reason at all we couldn't handle the fault,
357 	 * make sure we exit gracefully rather than endlessly redo
358 	 * the fault.
359 	 */
360 	fault = handle_mm_fault(mm, vma, address, flags);
361 	/* No reason to continue if interrupted by SIGKILL. */
362 	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
363 		fault = VM_FAULT_SIGNAL;
364 		goto out;
365 	}
366 	if (unlikely(fault & VM_FAULT_ERROR))
367 		goto out_up;
368 
369 	/*
370 	 * Major/minor page fault accounting is only done on the
371 	 * initial attempt. If we go through a retry, it is extremely
372 	 * likely that the page will be found in page cache at that point.
373 	 */
374 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
375 		if (fault & VM_FAULT_MAJOR) {
376 			tsk->maj_flt++;
377 			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
378 				      regs, address);
379 		} else {
380 			tsk->min_flt++;
381 			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
382 				      regs, address);
383 		}
384 		if (fault & VM_FAULT_RETRY) {
385 #ifdef CONFIG_PGSTE
386 			if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) {
387 				/* FAULT_FLAG_RETRY_NOWAIT has been set,
388 				 * mmap_sem has not been released */
389 				current->thread.gmap_pfault = 1;
390 				fault = VM_FAULT_PFAULT;
391 				goto out_up;
392 			}
393 #endif
394 			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
395 			 * of starvation. */
396 			flags &= ~(FAULT_FLAG_ALLOW_RETRY |
397 				   FAULT_FLAG_RETRY_NOWAIT);
398 			flags |= FAULT_FLAG_TRIED;
399 			down_read(&mm->mmap_sem);
400 			goto retry;
401 		}
402 	}
403 	fault = 0;
404 out_up:
405 	up_read(&mm->mmap_sem);
406 out:
407 	return fault;
408 }
409 
410 void __kprobes do_protection_exception(struct pt_regs *regs)
411 {
412 	unsigned long trans_exc_code;
413 	int fault;
414 
415 	trans_exc_code = regs->int_parm_long;
416 	/*
417 	 * Protection exceptions are suppressing, decrement psw address.
418 	 * The exception to this rule are aborted transactions, for these
419 	 * the PSW already points to the correct location.
420 	 */
421 	if (!(regs->int_code & 0x200))
422 		regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
423 	/*
424 	 * Check for low-address protection.  This needs to be treated
425 	 * as a special case because the translation exception code
426 	 * field is not guaranteed to contain valid data in this case.
427 	 */
428 	if (unlikely(!(trans_exc_code & 4))) {
429 		do_low_address(regs);
430 		return;
431 	}
432 	fault = do_exception(regs, VM_WRITE);
433 	if (unlikely(fault))
434 		do_fault_error(regs, fault);
435 }
436 
437 void __kprobes do_dat_exception(struct pt_regs *regs)
438 {
439 	int access, fault;
440 
441 	access = VM_READ | VM_EXEC | VM_WRITE;
442 	fault = do_exception(regs, access);
443 	if (unlikely(fault))
444 		do_fault_error(regs, fault);
445 }
446 
447 #ifdef CONFIG_PFAULT
448 /*
449  * 'pfault' pseudo page faults routines.
450  */
451 static int pfault_disable;
452 
453 static int __init nopfault(char *str)
454 {
455 	pfault_disable = 1;
456 	return 1;
457 }
458 
459 __setup("nopfault", nopfault);
460 
461 struct pfault_refbk {
462 	u16 refdiagc;
463 	u16 reffcode;
464 	u16 refdwlen;
465 	u16 refversn;
466 	u64 refgaddr;
467 	u64 refselmk;
468 	u64 refcmpmk;
469 	u64 reserved;
470 } __attribute__ ((packed, aligned(8)));
471 
472 int pfault_init(void)
473 {
474 	struct pfault_refbk refbk = {
475 		.refdiagc = 0x258,
476 		.reffcode = 0,
477 		.refdwlen = 5,
478 		.refversn = 2,
479 		.refgaddr = __LC_CURRENT_PID,
480 		.refselmk = 1ULL << 48,
481 		.refcmpmk = 1ULL << 48,
482 		.reserved = __PF_RES_FIELD };
483         int rc;
484 
485 	if (pfault_disable)
486 		return -1;
487 	asm volatile(
488 		"	diag	%1,%0,0x258\n"
489 		"0:	j	2f\n"
490 		"1:	la	%0,8\n"
491 		"2:\n"
492 		EX_TABLE(0b,1b)
493 		: "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc");
494         return rc;
495 }
496 
497 void pfault_fini(void)
498 {
499 	struct pfault_refbk refbk = {
500 		.refdiagc = 0x258,
501 		.reffcode = 1,
502 		.refdwlen = 5,
503 		.refversn = 2,
504 	};
505 
506 	if (pfault_disable)
507 		return;
508 	asm volatile(
509 		"	diag	%0,0,0x258\n"
510 		"0:\n"
511 		EX_TABLE(0b,0b)
512 		: : "a" (&refbk), "m" (refbk) : "cc");
513 }
514 
515 static DEFINE_SPINLOCK(pfault_lock);
516 static LIST_HEAD(pfault_list);
517 
518 static void pfault_interrupt(struct ext_code ext_code,
519 			     unsigned int param32, unsigned long param64)
520 {
521 	struct task_struct *tsk;
522 	__u16 subcode;
523 	pid_t pid;
524 
525 	/*
526 	 * Get the external interruption subcode & pfault
527 	 * initial/completion signal bit. VM stores this
528 	 * in the 'cpu address' field associated with the
529          * external interrupt.
530 	 */
531 	subcode = ext_code.subcode;
532 	if ((subcode & 0xff00) != __SUBCODE_MASK)
533 		return;
534 	inc_irq_stat(IRQEXT_PFL);
535 	/* Get the token (= pid of the affected task). */
536 	pid = sizeof(void *) == 4 ? param32 : param64;
537 	rcu_read_lock();
538 	tsk = find_task_by_pid_ns(pid, &init_pid_ns);
539 	if (tsk)
540 		get_task_struct(tsk);
541 	rcu_read_unlock();
542 	if (!tsk)
543 		return;
544 	spin_lock(&pfault_lock);
545 	if (subcode & 0x0080) {
546 		/* signal bit is set -> a page has been swapped in by VM */
547 		if (tsk->thread.pfault_wait == 1) {
548 			/* Initial interrupt was faster than the completion
549 			 * interrupt. pfault_wait is valid. Set pfault_wait
550 			 * back to zero and wake up the process. This can
551 			 * safely be done because the task is still sleeping
552 			 * and can't produce new pfaults. */
553 			tsk->thread.pfault_wait = 0;
554 			list_del(&tsk->thread.list);
555 			wake_up_process(tsk);
556 			put_task_struct(tsk);
557 		} else {
558 			/* Completion interrupt was faster than initial
559 			 * interrupt. Set pfault_wait to -1 so the initial
560 			 * interrupt doesn't put the task to sleep.
561 			 * If the task is not running, ignore the completion
562 			 * interrupt since it must be a leftover of a PFAULT
563 			 * CANCEL operation which didn't remove all pending
564 			 * completion interrupts. */
565 			if (tsk->state == TASK_RUNNING)
566 				tsk->thread.pfault_wait = -1;
567 		}
568 	} else {
569 		/* signal bit not set -> a real page is missing. */
570 		if (WARN_ON_ONCE(tsk != current))
571 			goto out;
572 		if (tsk->thread.pfault_wait == 1) {
573 			/* Already on the list with a reference: put to sleep */
574 			__set_task_state(tsk, TASK_UNINTERRUPTIBLE);
575 			set_tsk_need_resched(tsk);
576 		} else if (tsk->thread.pfault_wait == -1) {
577 			/* Completion interrupt was faster than the initial
578 			 * interrupt (pfault_wait == -1). Set pfault_wait
579 			 * back to zero and exit. */
580 			tsk->thread.pfault_wait = 0;
581 		} else {
582 			/* Initial interrupt arrived before completion
583 			 * interrupt. Let the task sleep.
584 			 * An extra task reference is needed since a different
585 			 * cpu may set the task state to TASK_RUNNING again
586 			 * before the scheduler is reached. */
587 			get_task_struct(tsk);
588 			tsk->thread.pfault_wait = 1;
589 			list_add(&tsk->thread.list, &pfault_list);
590 			__set_task_state(tsk, TASK_UNINTERRUPTIBLE);
591 			set_tsk_need_resched(tsk);
592 		}
593 	}
594 out:
595 	spin_unlock(&pfault_lock);
596 	put_task_struct(tsk);
597 }
598 
599 static int pfault_cpu_notify(struct notifier_block *self, unsigned long action,
600 			     void *hcpu)
601 {
602 	struct thread_struct *thread, *next;
603 	struct task_struct *tsk;
604 
605 	switch (action & ~CPU_TASKS_FROZEN) {
606 	case CPU_DEAD:
607 		spin_lock_irq(&pfault_lock);
608 		list_for_each_entry_safe(thread, next, &pfault_list, list) {
609 			thread->pfault_wait = 0;
610 			list_del(&thread->list);
611 			tsk = container_of(thread, struct task_struct, thread);
612 			wake_up_process(tsk);
613 			put_task_struct(tsk);
614 		}
615 		spin_unlock_irq(&pfault_lock);
616 		break;
617 	default:
618 		break;
619 	}
620 	return NOTIFY_OK;
621 }
622 
623 static int __init pfault_irq_init(void)
624 {
625 	int rc;
626 
627 	rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt);
628 	if (rc)
629 		goto out_extint;
630 	rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP;
631 	if (rc)
632 		goto out_pfault;
633 	irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL);
634 	hotcpu_notifier(pfault_cpu_notify, 0);
635 	return 0;
636 
637 out_pfault:
638 	unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt);
639 out_extint:
640 	pfault_disable = 1;
641 	return rc;
642 }
643 early_initcall(pfault_irq_init);
644 
645 #endif /* CONFIG_PFAULT */
646