xref: /openbmc/linux/arch/s390/mm/fault.c (revision 82ced6fd)
1 /*
2  *  arch/s390/mm/fault.c
3  *
4  *  S390 version
5  *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
6  *    Author(s): Hartmut Penner (hp@de.ibm.com)
7  *               Ulrich Weigand (uweigand@de.ibm.com)
8  *
9  *  Derived from "arch/i386/mm/fault.c"
10  *    Copyright (C) 1995  Linus Torvalds
11  */
12 
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/smp.h>
23 #include <linux/kdebug.h>
24 #include <linux/smp_lock.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/system.h>
33 #include <asm/pgtable.h>
34 #include <asm/s390_ext.h>
35 #include <asm/mmu_context.h>
36 #include "../kernel/entry.h"
37 
38 #ifndef CONFIG_64BIT
39 #define __FAIL_ADDR_MASK 0x7ffff000
40 #define __FIXUP_MASK 0x7fffffff
41 #define __SUBCODE_MASK 0x0200
42 #define __PF_RES_FIELD 0ULL
43 #else /* CONFIG_64BIT */
44 #define __FAIL_ADDR_MASK -4096L
45 #define __FIXUP_MASK ~0L
46 #define __SUBCODE_MASK 0x0600
47 #define __PF_RES_FIELD 0x8000000000000000ULL
48 #endif /* CONFIG_64BIT */
49 
50 #ifdef CONFIG_SYSCTL
51 extern int sysctl_userprocess_debug;
52 #endif
53 
54 #ifdef CONFIG_KPROBES
55 static inline int notify_page_fault(struct pt_regs *regs, long err)
56 {
57 	int ret = 0;
58 
59 	/* kprobe_running() needs smp_processor_id() */
60 	if (!user_mode(regs)) {
61 		preempt_disable();
62 		if (kprobe_running() && kprobe_fault_handler(regs, 14))
63 			ret = 1;
64 		preempt_enable();
65 	}
66 
67 	return ret;
68 }
69 #else
70 static inline int notify_page_fault(struct pt_regs *regs, long err)
71 {
72 	return 0;
73 }
74 #endif
75 
76 
77 /*
78  * Unlock any spinlocks which will prevent us from getting the
79  * message out.
80  */
81 void bust_spinlocks(int yes)
82 {
83 	if (yes) {
84 		oops_in_progress = 1;
85 	} else {
86 		int loglevel_save = console_loglevel;
87 		console_unblank();
88 		oops_in_progress = 0;
89 		/*
90 		 * OK, the message is on the console.  Now we call printk()
91 		 * without oops_in_progress set so that printk will give klogd
92 		 * a poke.  Hold onto your hats...
93 		 */
94 		console_loglevel = 15;
95 		printk(" ");
96 		console_loglevel = loglevel_save;
97 	}
98 }
99 
100 /*
101  * Returns the address space associated with the fault.
102  * Returns 0 for kernel space, 1 for user space and
103  * 2 for code execution in user space with noexec=on.
104  */
105 static inline int check_space(struct task_struct *tsk)
106 {
107 	/*
108 	 * The lowest two bits of S390_lowcore.trans_exc_code
109 	 * indicate which paging table was used.
110 	 */
111 	int desc = S390_lowcore.trans_exc_code & 3;
112 
113 	if (desc == 3)	/* Home Segment Table Descriptor */
114 		return switch_amode == 0;
115 	if (desc == 2)	/* Secondary Segment Table Descriptor */
116 		return tsk->thread.mm_segment.ar4;
117 #ifdef CONFIG_S390_SWITCH_AMODE
118 	if (unlikely(desc == 1)) { /* STD determined via access register */
119 		/* %a0 always indicates primary space. */
120 		if (S390_lowcore.exc_access_id != 0) {
121 			save_access_regs(tsk->thread.acrs);
122 			/*
123 			 * An alet of 0 indicates primary space.
124 			 * An alet of 1 indicates secondary space.
125 			 * Any other alet values generate an
126 			 * alen-translation exception.
127 			 */
128 			if (tsk->thread.acrs[S390_lowcore.exc_access_id])
129 				return tsk->thread.mm_segment.ar4;
130 		}
131 	}
132 #endif
133 	/* Primary Segment Table Descriptor */
134 	return switch_amode << s390_noexec;
135 }
136 
137 /*
138  * Send SIGSEGV to task.  This is an external routine
139  * to keep the stack usage of do_page_fault small.
140  */
141 static void do_sigsegv(struct pt_regs *regs, unsigned long error_code,
142 		       int si_code, unsigned long address)
143 {
144 	struct siginfo si;
145 
146 #if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG)
147 #if defined(CONFIG_SYSCTL)
148 	if (sysctl_userprocess_debug)
149 #endif
150 	{
151 		printk("User process fault: interruption code 0x%lX\n",
152 		       error_code);
153 		printk("failing address: %lX\n", address);
154 		show_regs(regs);
155 	}
156 #endif
157 	si.si_signo = SIGSEGV;
158 	si.si_code = si_code;
159 	si.si_addr = (void __user *) address;
160 	force_sig_info(SIGSEGV, &si, current);
161 }
162 
163 static void do_no_context(struct pt_regs *regs, unsigned long error_code,
164 			  unsigned long address)
165 {
166 	const struct exception_table_entry *fixup;
167 
168 	/* Are we prepared to handle this kernel fault?  */
169 	fixup = search_exception_tables(regs->psw.addr & __FIXUP_MASK);
170 	if (fixup) {
171 		regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE;
172 		return;
173 	}
174 
175 	/*
176 	 * Oops. The kernel tried to access some bad page. We'll have to
177 	 * terminate things with extreme prejudice.
178 	 */
179 	if (check_space(current) == 0)
180 		printk(KERN_ALERT "Unable to handle kernel pointer dereference"
181 		       " at virtual kernel address %p\n", (void *)address);
182 	else
183 		printk(KERN_ALERT "Unable to handle kernel paging request"
184 		       " at virtual user address %p\n", (void *)address);
185 
186 	die("Oops", regs, error_code);
187 	do_exit(SIGKILL);
188 }
189 
190 static void do_low_address(struct pt_regs *regs, unsigned long error_code)
191 {
192 	/* Low-address protection hit in kernel mode means
193 	   NULL pointer write access in kernel mode.  */
194 	if (regs->psw.mask & PSW_MASK_PSTATE) {
195 		/* Low-address protection hit in user mode 'cannot happen'. */
196 		die ("Low-address protection", regs, error_code);
197 		do_exit(SIGKILL);
198 	}
199 
200 	do_no_context(regs, error_code, 0);
201 }
202 
203 static void do_sigbus(struct pt_regs *regs, unsigned long error_code,
204 		      unsigned long address)
205 {
206 	struct task_struct *tsk = current;
207 	struct mm_struct *mm = tsk->mm;
208 
209 	up_read(&mm->mmap_sem);
210 	/*
211 	 * Send a sigbus, regardless of whether we were in kernel
212 	 * or user mode.
213 	 */
214 	tsk->thread.prot_addr = address;
215 	tsk->thread.trap_no = error_code;
216 	force_sig(SIGBUS, tsk);
217 
218 	/* Kernel mode? Handle exceptions or die */
219 	if (!(regs->psw.mask & PSW_MASK_PSTATE))
220 		do_no_context(regs, error_code, address);
221 }
222 
223 #ifdef CONFIG_S390_EXEC_PROTECT
224 static int signal_return(struct mm_struct *mm, struct pt_regs *regs,
225 			 unsigned long address, unsigned long error_code)
226 {
227 	u16 instruction;
228 	int rc;
229 #ifdef CONFIG_COMPAT
230 	int compat;
231 #endif
232 
233 	pagefault_disable();
234 	rc = __get_user(instruction, (u16 __user *) regs->psw.addr);
235 	pagefault_enable();
236 	if (rc)
237 		return -EFAULT;
238 
239 	up_read(&mm->mmap_sem);
240 	clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
241 #ifdef CONFIG_COMPAT
242 	compat = test_tsk_thread_flag(current, TIF_31BIT);
243 	if (compat && instruction == 0x0a77)
244 		sys32_sigreturn();
245 	else if (compat && instruction == 0x0aad)
246 		sys32_rt_sigreturn();
247 	else
248 #endif
249 	if (instruction == 0x0a77)
250 		sys_sigreturn();
251 	else if (instruction == 0x0aad)
252 		sys_rt_sigreturn();
253 	else {
254 		current->thread.prot_addr = address;
255 		current->thread.trap_no = error_code;
256 		do_sigsegv(regs, error_code, SEGV_MAPERR, address);
257 	}
258 	return 0;
259 }
260 #endif /* CONFIG_S390_EXEC_PROTECT */
261 
262 /*
263  * This routine handles page faults.  It determines the address,
264  * and the problem, and then passes it off to one of the appropriate
265  * routines.
266  *
267  * error_code:
268  *   04       Protection           ->  Write-Protection  (suprression)
269  *   10       Segment translation  ->  Not present       (nullification)
270  *   11       Page translation     ->  Not present       (nullification)
271  *   3b       Region third trans.  ->  Not present       (nullification)
272  */
273 static inline void
274 do_exception(struct pt_regs *regs, unsigned long error_code, int write)
275 {
276 	struct task_struct *tsk;
277 	struct mm_struct *mm;
278 	struct vm_area_struct *vma;
279 	unsigned long address;
280 	int space;
281 	int si_code;
282 	int fault;
283 
284 	if (notify_page_fault(regs, error_code))
285 		return;
286 
287 	tsk = current;
288 	mm = tsk->mm;
289 
290 	/* get the failing address and the affected space */
291 	address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
292 	space = check_space(tsk);
293 
294 	/*
295 	 * Verify that the fault happened in user space, that
296 	 * we are not in an interrupt and that there is a
297 	 * user context.
298 	 */
299 	if (unlikely(space == 0 || in_atomic() || !mm))
300 		goto no_context;
301 
302 	/*
303 	 * When we get here, the fault happened in the current
304 	 * task's user address space, so we can switch on the
305 	 * interrupts again and then search the VMAs
306 	 */
307 	local_irq_enable();
308 
309 	down_read(&mm->mmap_sem);
310 
311 	si_code = SEGV_MAPERR;
312 	vma = find_vma(mm, address);
313 	if (!vma)
314 		goto bad_area;
315 
316 #ifdef CONFIG_S390_EXEC_PROTECT
317 	if (unlikely((space == 2) && !(vma->vm_flags & VM_EXEC)))
318 		if (!signal_return(mm, regs, address, error_code))
319 			/*
320 			 * signal_return() has done an up_read(&mm->mmap_sem)
321 			 * if it returns 0.
322 			 */
323 			return;
324 #endif
325 
326 	if (vma->vm_start <= address)
327 		goto good_area;
328 	if (!(vma->vm_flags & VM_GROWSDOWN))
329 		goto bad_area;
330 	if (expand_stack(vma, address))
331 		goto bad_area;
332 /*
333  * Ok, we have a good vm_area for this memory access, so
334  * we can handle it..
335  */
336 good_area:
337 	si_code = SEGV_ACCERR;
338 	if (!write) {
339 		/* page not present, check vm flags */
340 		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
341 			goto bad_area;
342 	} else {
343 		if (!(vma->vm_flags & VM_WRITE))
344 			goto bad_area;
345 	}
346 
347 	if (is_vm_hugetlb_page(vma))
348 		address &= HPAGE_MASK;
349 	/*
350 	 * If for any reason at all we couldn't handle the fault,
351 	 * make sure we exit gracefully rather than endlessly redo
352 	 * the fault.
353 	 */
354 	fault = handle_mm_fault(mm, vma, address, write);
355 	if (unlikely(fault & VM_FAULT_ERROR)) {
356 		if (fault & VM_FAULT_OOM) {
357 			up_read(&mm->mmap_sem);
358 			pagefault_out_of_memory();
359 			return;
360 		} else if (fault & VM_FAULT_SIGBUS) {
361 			do_sigbus(regs, error_code, address);
362 			return;
363 		}
364 		BUG();
365 	}
366 	if (fault & VM_FAULT_MAJOR)
367 		tsk->maj_flt++;
368 	else
369 		tsk->min_flt++;
370 
371         up_read(&mm->mmap_sem);
372 	/*
373 	 * The instruction that caused the program check will
374 	 * be repeated. Don't signal single step via SIGTRAP.
375 	 */
376 	clear_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
377         return;
378 
379 /*
380  * Something tried to access memory that isn't in our memory map..
381  * Fix it, but check if it's kernel or user first..
382  */
383 bad_area:
384 	up_read(&mm->mmap_sem);
385 
386 	/* User mode accesses just cause a SIGSEGV */
387 	if (regs->psw.mask & PSW_MASK_PSTATE) {
388 		tsk->thread.prot_addr = address;
389 		tsk->thread.trap_no = error_code;
390 		do_sigsegv(regs, error_code, si_code, address);
391 		return;
392 	}
393 
394 no_context:
395 	do_no_context(regs, error_code, address);
396 }
397 
398 void __kprobes do_protection_exception(struct pt_regs *regs,
399 				       long error_code)
400 {
401 	/* Protection exception is supressing, decrement psw address. */
402 	regs->psw.addr -= (error_code >> 16);
403 	/*
404 	 * Check for low-address protection.  This needs to be treated
405 	 * as a special case because the translation exception code
406 	 * field is not guaranteed to contain valid data in this case.
407 	 */
408 	if (unlikely(!(S390_lowcore.trans_exc_code & 4))) {
409 		do_low_address(regs, error_code);
410 		return;
411 	}
412 	do_exception(regs, 4, 1);
413 }
414 
415 void __kprobes do_dat_exception(struct pt_regs *regs, long error_code)
416 {
417 	do_exception(regs, error_code & 0xff, 0);
418 }
419 
420 #ifdef CONFIG_64BIT
421 void __kprobes do_asce_exception(struct pt_regs *regs, unsigned long error_code)
422 {
423 	struct mm_struct *mm;
424 	struct vm_area_struct *vma;
425 	unsigned long address;
426 	int space;
427 
428 	mm = current->mm;
429 	address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
430 	space = check_space(current);
431 
432 	if (unlikely(space == 0 || in_atomic() || !mm))
433 		goto no_context;
434 
435 	local_irq_enable();
436 
437 	down_read(&mm->mmap_sem);
438 	vma = find_vma(mm, address);
439 	up_read(&mm->mmap_sem);
440 
441 	if (vma) {
442 		update_mm(mm, current);
443 		return;
444 	}
445 
446 	/* User mode accesses just cause a SIGSEGV */
447 	if (regs->psw.mask & PSW_MASK_PSTATE) {
448 		current->thread.prot_addr = address;
449 		current->thread.trap_no = error_code;
450 		do_sigsegv(regs, error_code, SEGV_MAPERR, address);
451 		return;
452 	}
453 
454 no_context:
455 	do_no_context(regs, error_code, address);
456 }
457 #endif
458 
459 #ifdef CONFIG_PFAULT
460 /*
461  * 'pfault' pseudo page faults routines.
462  */
463 static ext_int_info_t ext_int_pfault;
464 static int pfault_disable = 0;
465 
466 static int __init nopfault(char *str)
467 {
468 	pfault_disable = 1;
469 	return 1;
470 }
471 
472 __setup("nopfault", nopfault);
473 
474 typedef struct {
475 	__u16 refdiagc;
476 	__u16 reffcode;
477 	__u16 refdwlen;
478 	__u16 refversn;
479 	__u64 refgaddr;
480 	__u64 refselmk;
481 	__u64 refcmpmk;
482 	__u64 reserved;
483 } __attribute__ ((packed, aligned(8))) pfault_refbk_t;
484 
485 int pfault_init(void)
486 {
487 	pfault_refbk_t refbk =
488 		{ 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48,
489 		  __PF_RES_FIELD };
490         int rc;
491 
492 	if (!MACHINE_IS_VM || pfault_disable)
493 		return -1;
494 	asm volatile(
495 		"	diag	%1,%0,0x258\n"
496 		"0:	j	2f\n"
497 		"1:	la	%0,8\n"
498 		"2:\n"
499 		EX_TABLE(0b,1b)
500 		: "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc");
501         __ctl_set_bit(0, 9);
502         return rc;
503 }
504 
505 void pfault_fini(void)
506 {
507 	pfault_refbk_t refbk =
508 	{ 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL };
509 
510 	if (!MACHINE_IS_VM || pfault_disable)
511 		return;
512 	__ctl_clear_bit(0,9);
513 	asm volatile(
514 		"	diag	%0,0,0x258\n"
515 		"0:\n"
516 		EX_TABLE(0b,0b)
517 		: : "a" (&refbk), "m" (refbk) : "cc");
518 }
519 
520 static void pfault_interrupt(__u16 error_code)
521 {
522 	struct task_struct *tsk;
523 	__u16 subcode;
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 = S390_lowcore.cpu_addr;
532 	if ((subcode & 0xff00) != __SUBCODE_MASK)
533 		return;
534 
535 	/*
536 	 * Get the token (= address of the task structure of the affected task).
537 	 */
538 	tsk = *(struct task_struct **) __LC_PFAULT_INTPARM;
539 
540 	if (subcode & 0x0080) {
541 		/* signal bit is set -> a page has been swapped in by VM */
542 		if (xchg(&tsk->thread.pfault_wait, -1) != 0) {
543 			/* Initial interrupt was faster than the completion
544 			 * interrupt. pfault_wait is valid. Set pfault_wait
545 			 * back to zero and wake up the process. This can
546 			 * safely be done because the task is still sleeping
547 			 * and can't produce new pfaults. */
548 			tsk->thread.pfault_wait = 0;
549 			wake_up_process(tsk);
550 			put_task_struct(tsk);
551 		}
552 	} else {
553 		/* signal bit not set -> a real page is missing. */
554 		get_task_struct(tsk);
555 		set_task_state(tsk, TASK_UNINTERRUPTIBLE);
556 		if (xchg(&tsk->thread.pfault_wait, 1) != 0) {
557 			/* Completion interrupt was faster than the initial
558 			 * interrupt (swapped in a -1 for pfault_wait). Set
559 			 * pfault_wait back to zero and exit. This can be
560 			 * done safely because tsk is running in kernel
561 			 * mode and can't produce new pfaults. */
562 			tsk->thread.pfault_wait = 0;
563 			set_task_state(tsk, TASK_RUNNING);
564 			put_task_struct(tsk);
565 		} else
566 			set_tsk_need_resched(tsk);
567 	}
568 }
569 
570 void __init pfault_irq_init(void)
571 {
572 	if (!MACHINE_IS_VM)
573 		return;
574 
575 	/*
576 	 * Try to get pfault pseudo page faults going.
577 	 */
578 	if (register_early_external_interrupt(0x2603, pfault_interrupt,
579 					      &ext_int_pfault) != 0)
580 		panic("Couldn't request external interrupt 0x2603");
581 
582 	if (pfault_init() == 0)
583 		return;
584 
585 	/* Tough luck, no pfault. */
586 	pfault_disable = 1;
587 	unregister_early_external_interrupt(0x2603, pfault_interrupt,
588 					    &ext_int_pfault);
589 }
590 #endif
591