xref: /openbmc/linux/arch/s390/mm/fault.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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 
32 #include <asm/system.h>
33 #include <asm/pgtable.h>
34 #include <asm/s390_ext.h>
35 
36 #ifndef CONFIG_64BIT
37 #define __FAIL_ADDR_MASK 0x7ffff000
38 #define __FIXUP_MASK 0x7fffffff
39 #define __SUBCODE_MASK 0x0200
40 #define __PF_RES_FIELD 0ULL
41 #else /* CONFIG_64BIT */
42 #define __FAIL_ADDR_MASK -4096L
43 #define __FIXUP_MASK ~0L
44 #define __SUBCODE_MASK 0x0600
45 #define __PF_RES_FIELD 0x8000000000000000ULL
46 #endif /* CONFIG_64BIT */
47 
48 #ifdef CONFIG_SYSCTL
49 extern int sysctl_userprocess_debug;
50 #endif
51 
52 extern void die(const char *,struct pt_regs *,long);
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 /*
204  * We ran out of memory, or some other thing happened to us that made
205  * us unable to handle the page fault gracefully.
206  */
207 static int do_out_of_memory(struct pt_regs *regs, unsigned long error_code,
208 			    unsigned long address)
209 {
210 	struct task_struct *tsk = current;
211 	struct mm_struct *mm = tsk->mm;
212 
213 	up_read(&mm->mmap_sem);
214 	if (is_init(tsk)) {
215 		yield();
216 		down_read(&mm->mmap_sem);
217 		return 1;
218 	}
219 	printk("VM: killing process %s\n", tsk->comm);
220 	if (regs->psw.mask & PSW_MASK_PSTATE)
221 		do_exit(SIGKILL);
222 	do_no_context(regs, error_code, address);
223 	return 0;
224 }
225 
226 static void do_sigbus(struct pt_regs *regs, unsigned long error_code,
227 		      unsigned long address)
228 {
229 	struct task_struct *tsk = current;
230 	struct mm_struct *mm = tsk->mm;
231 
232 	up_read(&mm->mmap_sem);
233 	/*
234 	 * Send a sigbus, regardless of whether we were in kernel
235 	 * or user mode.
236 	 */
237 	tsk->thread.prot_addr = address;
238 	tsk->thread.trap_no = error_code;
239 	force_sig(SIGBUS, tsk);
240 
241 	/* Kernel mode? Handle exceptions or die */
242 	if (!(regs->psw.mask & PSW_MASK_PSTATE))
243 		do_no_context(regs, error_code, address);
244 }
245 
246 #ifdef CONFIG_S390_EXEC_PROTECT
247 extern long sys_sigreturn(struct pt_regs *regs);
248 extern long sys_rt_sigreturn(struct pt_regs *regs);
249 extern long sys32_sigreturn(struct pt_regs *regs);
250 extern long sys32_rt_sigreturn(struct pt_regs *regs);
251 
252 static int signal_return(struct mm_struct *mm, struct pt_regs *regs,
253 			 unsigned long address, unsigned long error_code)
254 {
255 	u16 instruction;
256 	int rc;
257 #ifdef CONFIG_COMPAT
258 	int compat;
259 #endif
260 
261 	pagefault_disable();
262 	rc = __get_user(instruction, (u16 __user *) regs->psw.addr);
263 	pagefault_enable();
264 	if (rc)
265 		return -EFAULT;
266 
267 	up_read(&mm->mmap_sem);
268 	clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
269 #ifdef CONFIG_COMPAT
270 	compat = test_tsk_thread_flag(current, TIF_31BIT);
271 	if (compat && instruction == 0x0a77)
272 		sys32_sigreturn(regs);
273 	else if (compat && instruction == 0x0aad)
274 		sys32_rt_sigreturn(regs);
275 	else
276 #endif
277 	if (instruction == 0x0a77)
278 		sys_sigreturn(regs);
279 	else if (instruction == 0x0aad)
280 		sys_rt_sigreturn(regs);
281 	else {
282 		current->thread.prot_addr = address;
283 		current->thread.trap_no = error_code;
284 		do_sigsegv(regs, error_code, SEGV_MAPERR, address);
285 	}
286 	return 0;
287 }
288 #endif /* CONFIG_S390_EXEC_PROTECT */
289 
290 /*
291  * This routine handles page faults.  It determines the address,
292  * and the problem, and then passes it off to one of the appropriate
293  * routines.
294  *
295  * error_code:
296  *   04       Protection           ->  Write-Protection  (suprression)
297  *   10       Segment translation  ->  Not present       (nullification)
298  *   11       Page translation     ->  Not present       (nullification)
299  *   3b       Region third trans.  ->  Not present       (nullification)
300  */
301 static inline void
302 do_exception(struct pt_regs *regs, unsigned long error_code, int write)
303 {
304 	struct task_struct *tsk;
305 	struct mm_struct *mm;
306 	struct vm_area_struct *vma;
307 	unsigned long address;
308 	int space;
309 	int si_code;
310 
311 	if (notify_page_fault(regs, error_code))
312 		return;
313 
314 	tsk = current;
315 	mm = tsk->mm;
316 
317 	/* get the failing address and the affected space */
318 	address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
319 	space = check_space(tsk);
320 
321 	/*
322 	 * Verify that the fault happened in user space, that
323 	 * we are not in an interrupt and that there is a
324 	 * user context.
325 	 */
326 	if (unlikely(space == 0 || in_atomic() || !mm))
327 		goto no_context;
328 
329 	/*
330 	 * When we get here, the fault happened in the current
331 	 * task's user address space, so we can switch on the
332 	 * interrupts again and then search the VMAs
333 	 */
334 	local_irq_enable();
335 
336 	down_read(&mm->mmap_sem);
337 
338 	si_code = SEGV_MAPERR;
339 	vma = find_vma(mm, address);
340 	if (!vma)
341 		goto bad_area;
342 
343 #ifdef CONFIG_S390_EXEC_PROTECT
344 	if (unlikely((space == 2) && !(vma->vm_flags & VM_EXEC)))
345 		if (!signal_return(mm, regs, address, error_code))
346 			/*
347 			 * signal_return() has done an up_read(&mm->mmap_sem)
348 			 * if it returns 0.
349 			 */
350 			return;
351 #endif
352 
353 	if (vma->vm_start <= address)
354 		goto good_area;
355 	if (!(vma->vm_flags & VM_GROWSDOWN))
356 		goto bad_area;
357 	if (expand_stack(vma, address))
358 		goto bad_area;
359 /*
360  * Ok, we have a good vm_area for this memory access, so
361  * we can handle it..
362  */
363 good_area:
364 	si_code = SEGV_ACCERR;
365 	if (!write) {
366 		/* page not present, check vm flags */
367 		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
368 			goto bad_area;
369 	} else {
370 		if (!(vma->vm_flags & VM_WRITE))
371 			goto bad_area;
372 	}
373 
374 survive:
375 	/*
376 	 * If for any reason at all we couldn't handle the fault,
377 	 * make sure we exit gracefully rather than endlessly redo
378 	 * the fault.
379 	 */
380 	switch (handle_mm_fault(mm, vma, address, write)) {
381 	case VM_FAULT_MINOR:
382 		tsk->min_flt++;
383 		break;
384 	case VM_FAULT_MAJOR:
385 		tsk->maj_flt++;
386 		break;
387 	case VM_FAULT_SIGBUS:
388 		do_sigbus(regs, error_code, address);
389 		return;
390 	case VM_FAULT_OOM:
391 		if (do_out_of_memory(regs, error_code, address))
392 			goto survive;
393 		return;
394 	default:
395 		BUG();
396 	}
397 
398         up_read(&mm->mmap_sem);
399 	/*
400 	 * The instruction that caused the program check will
401 	 * be repeated. Don't signal single step via SIGTRAP.
402 	 */
403 	clear_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
404         return;
405 
406 /*
407  * Something tried to access memory that isn't in our memory map..
408  * Fix it, but check if it's kernel or user first..
409  */
410 bad_area:
411 	up_read(&mm->mmap_sem);
412 
413 	/* User mode accesses just cause a SIGSEGV */
414 	if (regs->psw.mask & PSW_MASK_PSTATE) {
415 		tsk->thread.prot_addr = address;
416 		tsk->thread.trap_no = error_code;
417 		do_sigsegv(regs, error_code, si_code, address);
418 		return;
419 	}
420 
421 no_context:
422 	do_no_context(regs, error_code, address);
423 }
424 
425 void __kprobes do_protection_exception(struct pt_regs *regs,
426 				       unsigned long error_code)
427 {
428 	/* Protection exception is supressing, decrement psw address. */
429 	regs->psw.addr -= (error_code >> 16);
430 	/*
431 	 * Check for low-address protection.  This needs to be treated
432 	 * as a special case because the translation exception code
433 	 * field is not guaranteed to contain valid data in this case.
434 	 */
435 	if (unlikely(!(S390_lowcore.trans_exc_code & 4))) {
436 		do_low_address(regs, error_code);
437 		return;
438 	}
439 	do_exception(regs, 4, 1);
440 }
441 
442 void __kprobes do_dat_exception(struct pt_regs *regs, unsigned long error_code)
443 {
444 	do_exception(regs, error_code & 0xff, 0);
445 }
446 
447 #ifdef CONFIG_PFAULT
448 /*
449  * 'pfault' pseudo page faults routines.
450  */
451 static ext_int_info_t ext_int_pfault;
452 static int pfault_disable = 0;
453 
454 static int __init nopfault(char *str)
455 {
456 	pfault_disable = 1;
457 	return 1;
458 }
459 
460 __setup("nopfault", nopfault);
461 
462 typedef struct {
463 	__u16 refdiagc;
464 	__u16 reffcode;
465 	__u16 refdwlen;
466 	__u16 refversn;
467 	__u64 refgaddr;
468 	__u64 refselmk;
469 	__u64 refcmpmk;
470 	__u64 reserved;
471 } __attribute__ ((packed)) pfault_refbk_t;
472 
473 int pfault_init(void)
474 {
475 	pfault_refbk_t refbk =
476 		{ 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48,
477 		  __PF_RES_FIELD };
478         int rc;
479 
480 	if (!MACHINE_IS_VM || pfault_disable)
481 		return -1;
482 	asm volatile(
483 		"	diag	%1,%0,0x258\n"
484 		"0:	j	2f\n"
485 		"1:	la	%0,8\n"
486 		"2:\n"
487 		EX_TABLE(0b,1b)
488 		: "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc");
489         __ctl_set_bit(0, 9);
490         return rc;
491 }
492 
493 void pfault_fini(void)
494 {
495 	pfault_refbk_t refbk =
496 	{ 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL };
497 
498 	if (!MACHINE_IS_VM || pfault_disable)
499 		return;
500 	__ctl_clear_bit(0,9);
501 	asm volatile(
502 		"	diag	%0,0,0x258\n"
503 		"0:\n"
504 		EX_TABLE(0b,0b)
505 		: : "a" (&refbk), "m" (refbk) : "cc");
506 }
507 
508 static void pfault_interrupt(__u16 error_code)
509 {
510 	struct task_struct *tsk;
511 	__u16 subcode;
512 
513 	/*
514 	 * Get the external interruption subcode & pfault
515 	 * initial/completion signal bit. VM stores this
516 	 * in the 'cpu address' field associated with the
517          * external interrupt.
518 	 */
519 	subcode = S390_lowcore.cpu_addr;
520 	if ((subcode & 0xff00) != __SUBCODE_MASK)
521 		return;
522 
523 	/*
524 	 * Get the token (= address of the task structure of the affected task).
525 	 */
526 	tsk = *(struct task_struct **) __LC_PFAULT_INTPARM;
527 
528 	if (subcode & 0x0080) {
529 		/* signal bit is set -> a page has been swapped in by VM */
530 		if (xchg(&tsk->thread.pfault_wait, -1) != 0) {
531 			/* Initial interrupt was faster than the completion
532 			 * interrupt. pfault_wait is valid. Set pfault_wait
533 			 * back to zero and wake up the process. This can
534 			 * safely be done because the task is still sleeping
535 			 * and can't produce new pfaults. */
536 			tsk->thread.pfault_wait = 0;
537 			wake_up_process(tsk);
538 			put_task_struct(tsk);
539 		}
540 	} else {
541 		/* signal bit not set -> a real page is missing. */
542 		get_task_struct(tsk);
543 		set_task_state(tsk, TASK_UNINTERRUPTIBLE);
544 		if (xchg(&tsk->thread.pfault_wait, 1) != 0) {
545 			/* Completion interrupt was faster than the initial
546 			 * interrupt (swapped in a -1 for pfault_wait). Set
547 			 * pfault_wait back to zero and exit. This can be
548 			 * done safely because tsk is running in kernel
549 			 * mode and can't produce new pfaults. */
550 			tsk->thread.pfault_wait = 0;
551 			set_task_state(tsk, TASK_RUNNING);
552 			put_task_struct(tsk);
553 		} else
554 			set_tsk_need_resched(tsk);
555 	}
556 }
557 
558 void __init pfault_irq_init(void)
559 {
560 	if (!MACHINE_IS_VM)
561 		return;
562 
563 	/*
564 	 * Try to get pfault pseudo page faults going.
565 	 */
566 	if (register_early_external_interrupt(0x2603, pfault_interrupt,
567 					      &ext_int_pfault) != 0)
568 		panic("Couldn't request external interrupt 0x2603");
569 
570 	if (pfault_init() == 0)
571 		return;
572 
573 	/* Tough luck, no pfault. */
574 	pfault_disable = 1;
575 	unregister_early_external_interrupt(0x2603, pfault_interrupt,
576 					    &ext_int_pfault);
577 }
578 #endif
579