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
notify_page_fault(struct pt_regs * regs,long err)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
notify_page_fault(struct pt_regs * regs,long err)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 */
bust_spinlocks(int yes)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 */
check_space(struct task_struct * tsk)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 */
do_sigsegv(struct pt_regs * regs,unsigned long error_code,int si_code,unsigned long address)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
do_no_context(struct pt_regs * regs,unsigned long error_code,unsigned long address)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
do_low_address(struct pt_regs * regs,unsigned long error_code)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 */
do_out_of_memory(struct pt_regs * regs,unsigned long error_code,unsigned long address)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_global_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_group_exit(SIGKILL);
222 do_no_context(regs, error_code, address);
223 return 0;
224 }
225
do_sigbus(struct pt_regs * regs,unsigned long error_code,unsigned long address)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
signal_return(struct mm_struct * mm,struct pt_regs * regs,unsigned long address,unsigned long error_code)247 static int signal_return(struct mm_struct *mm, struct pt_regs *regs,
248 unsigned long address, unsigned long error_code)
249 {
250 u16 instruction;
251 int rc;
252 #ifdef CONFIG_COMPAT
253 int compat;
254 #endif
255
256 pagefault_disable();
257 rc = __get_user(instruction, (u16 __user *) regs->psw.addr);
258 pagefault_enable();
259 if (rc)
260 return -EFAULT;
261
262 up_read(&mm->mmap_sem);
263 clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
264 #ifdef CONFIG_COMPAT
265 compat = test_tsk_thread_flag(current, TIF_31BIT);
266 if (compat && instruction == 0x0a77)
267 sys32_sigreturn();
268 else if (compat && instruction == 0x0aad)
269 sys32_rt_sigreturn();
270 else
271 #endif
272 if (instruction == 0x0a77)
273 sys_sigreturn();
274 else if (instruction == 0x0aad)
275 sys_rt_sigreturn();
276 else {
277 current->thread.prot_addr = address;
278 current->thread.trap_no = error_code;
279 do_sigsegv(regs, error_code, SEGV_MAPERR, address);
280 }
281 return 0;
282 }
283 #endif /* CONFIG_S390_EXEC_PROTECT */
284
285 /*
286 * This routine handles page faults. It determines the address,
287 * and the problem, and then passes it off to one of the appropriate
288 * routines.
289 *
290 * error_code:
291 * 04 Protection -> Write-Protection (suprression)
292 * 10 Segment translation -> Not present (nullification)
293 * 11 Page translation -> Not present (nullification)
294 * 3b Region third trans. -> Not present (nullification)
295 */
296 static inline void
do_exception(struct pt_regs * regs,unsigned long error_code,int write)297 do_exception(struct pt_regs *regs, unsigned long error_code, int write)
298 {
299 struct task_struct *tsk;
300 struct mm_struct *mm;
301 struct vm_area_struct *vma;
302 unsigned long address;
303 int space;
304 int si_code;
305 int fault;
306
307 if (notify_page_fault(regs, error_code))
308 return;
309
310 tsk = current;
311 mm = tsk->mm;
312
313 /* get the failing address and the affected space */
314 address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
315 space = check_space(tsk);
316
317 /*
318 * Verify that the fault happened in user space, that
319 * we are not in an interrupt and that there is a
320 * user context.
321 */
322 if (unlikely(space == 0 || in_atomic() || !mm))
323 goto no_context;
324
325 /*
326 * When we get here, the fault happened in the current
327 * task's user address space, so we can switch on the
328 * interrupts again and then search the VMAs
329 */
330 local_irq_enable();
331
332 down_read(&mm->mmap_sem);
333
334 si_code = SEGV_MAPERR;
335 vma = find_vma(mm, address);
336 if (!vma)
337 goto bad_area;
338
339 #ifdef CONFIG_S390_EXEC_PROTECT
340 if (unlikely((space == 2) && !(vma->vm_flags & VM_EXEC)))
341 if (!signal_return(mm, regs, address, error_code))
342 /*
343 * signal_return() has done an up_read(&mm->mmap_sem)
344 * if it returns 0.
345 */
346 return;
347 #endif
348
349 if (vma->vm_start <= address)
350 goto good_area;
351 if (!(vma->vm_flags & VM_GROWSDOWN))
352 goto bad_area;
353 if (expand_stack(vma, address))
354 goto bad_area;
355 /*
356 * Ok, we have a good vm_area for this memory access, so
357 * we can handle it..
358 */
359 good_area:
360 si_code = SEGV_ACCERR;
361 if (!write) {
362 /* page not present, check vm flags */
363 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
364 goto bad_area;
365 } else {
366 if (!(vma->vm_flags & VM_WRITE))
367 goto bad_area;
368 }
369
370 survive:
371 if (is_vm_hugetlb_page(vma))
372 address &= HPAGE_MASK;
373 /*
374 * If for any reason at all we couldn't handle the fault,
375 * make sure we exit gracefully rather than endlessly redo
376 * the fault.
377 */
378 fault = handle_mm_fault(mm, vma, address, write);
379 if (unlikely(fault & VM_FAULT_ERROR)) {
380 if (fault & VM_FAULT_OOM) {
381 if (do_out_of_memory(regs, error_code, address))
382 goto survive;
383 return;
384 } else if (fault & VM_FAULT_SIGBUS) {
385 do_sigbus(regs, error_code, address);
386 return;
387 }
388 BUG();
389 }
390 if (fault & VM_FAULT_MAJOR)
391 tsk->maj_flt++;
392 else
393 tsk->min_flt++;
394
395 up_read(&mm->mmap_sem);
396 /*
397 * The instruction that caused the program check will
398 * be repeated. Don't signal single step via SIGTRAP.
399 */
400 clear_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
401 return;
402
403 /*
404 * Something tried to access memory that isn't in our memory map..
405 * Fix it, but check if it's kernel or user first..
406 */
407 bad_area:
408 up_read(&mm->mmap_sem);
409
410 /* User mode accesses just cause a SIGSEGV */
411 if (regs->psw.mask & PSW_MASK_PSTATE) {
412 tsk->thread.prot_addr = address;
413 tsk->thread.trap_no = error_code;
414 do_sigsegv(regs, error_code, si_code, address);
415 return;
416 }
417
418 no_context:
419 do_no_context(regs, error_code, address);
420 }
421
do_protection_exception(struct pt_regs * regs,long error_code)422 void __kprobes do_protection_exception(struct pt_regs *regs,
423 long error_code)
424 {
425 /* Protection exception is supressing, decrement psw address. */
426 regs->psw.addr -= (error_code >> 16);
427 /*
428 * Check for low-address protection. This needs to be treated
429 * as a special case because the translation exception code
430 * field is not guaranteed to contain valid data in this case.
431 */
432 if (unlikely(!(S390_lowcore.trans_exc_code & 4))) {
433 do_low_address(regs, error_code);
434 return;
435 }
436 do_exception(regs, 4, 1);
437 }
438
do_dat_exception(struct pt_regs * regs,long error_code)439 void __kprobes do_dat_exception(struct pt_regs *regs, long error_code)
440 {
441 do_exception(regs, error_code & 0xff, 0);
442 }
443
444 #ifdef CONFIG_64BIT
do_asce_exception(struct pt_regs * regs,unsigned long error_code)445 void __kprobes do_asce_exception(struct pt_regs *regs, unsigned long error_code)
446 {
447 struct mm_struct *mm;
448 struct vm_area_struct *vma;
449 unsigned long address;
450 int space;
451
452 mm = current->mm;
453 address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
454 space = check_space(current);
455
456 if (unlikely(space == 0 || in_atomic() || !mm))
457 goto no_context;
458
459 local_irq_enable();
460
461 down_read(&mm->mmap_sem);
462 vma = find_vma(mm, address);
463 up_read(&mm->mmap_sem);
464
465 if (vma) {
466 update_mm(mm, current);
467 return;
468 }
469
470 /* User mode accesses just cause a SIGSEGV */
471 if (regs->psw.mask & PSW_MASK_PSTATE) {
472 current->thread.prot_addr = address;
473 current->thread.trap_no = error_code;
474 do_sigsegv(regs, error_code, SEGV_MAPERR, address);
475 return;
476 }
477
478 no_context:
479 do_no_context(regs, error_code, address);
480 }
481 #endif
482
483 #ifdef CONFIG_PFAULT
484 /*
485 * 'pfault' pseudo page faults routines.
486 */
487 static ext_int_info_t ext_int_pfault;
488 static int pfault_disable = 0;
489
nopfault(char * str)490 static int __init nopfault(char *str)
491 {
492 pfault_disable = 1;
493 return 1;
494 }
495
496 __setup("nopfault", nopfault);
497
498 typedef struct {
499 __u16 refdiagc;
500 __u16 reffcode;
501 __u16 refdwlen;
502 __u16 refversn;
503 __u64 refgaddr;
504 __u64 refselmk;
505 __u64 refcmpmk;
506 __u64 reserved;
507 } __attribute__ ((packed, aligned(8))) pfault_refbk_t;
508
pfault_init(void)509 int pfault_init(void)
510 {
511 pfault_refbk_t refbk =
512 { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48,
513 __PF_RES_FIELD };
514 int rc;
515
516 if (!MACHINE_IS_VM || pfault_disable)
517 return -1;
518 asm volatile(
519 " diag %1,%0,0x258\n"
520 "0: j 2f\n"
521 "1: la %0,8\n"
522 "2:\n"
523 EX_TABLE(0b,1b)
524 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc");
525 __ctl_set_bit(0, 9);
526 return rc;
527 }
528
pfault_fini(void)529 void pfault_fini(void)
530 {
531 pfault_refbk_t refbk =
532 { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL };
533
534 if (!MACHINE_IS_VM || pfault_disable)
535 return;
536 __ctl_clear_bit(0,9);
537 asm volatile(
538 " diag %0,0,0x258\n"
539 "0:\n"
540 EX_TABLE(0b,0b)
541 : : "a" (&refbk), "m" (refbk) : "cc");
542 }
543
pfault_interrupt(__u16 error_code)544 static void pfault_interrupt(__u16 error_code)
545 {
546 struct task_struct *tsk;
547 __u16 subcode;
548
549 /*
550 * Get the external interruption subcode & pfault
551 * initial/completion signal bit. VM stores this
552 * in the 'cpu address' field associated with the
553 * external interrupt.
554 */
555 subcode = S390_lowcore.cpu_addr;
556 if ((subcode & 0xff00) != __SUBCODE_MASK)
557 return;
558
559 /*
560 * Get the token (= address of the task structure of the affected task).
561 */
562 tsk = *(struct task_struct **) __LC_PFAULT_INTPARM;
563
564 if (subcode & 0x0080) {
565 /* signal bit is set -> a page has been swapped in by VM */
566 if (xchg(&tsk->thread.pfault_wait, -1) != 0) {
567 /* Initial interrupt was faster than the completion
568 * interrupt. pfault_wait is valid. Set pfault_wait
569 * back to zero and wake up the process. This can
570 * safely be done because the task is still sleeping
571 * and can't produce new pfaults. */
572 tsk->thread.pfault_wait = 0;
573 wake_up_process(tsk);
574 put_task_struct(tsk);
575 }
576 } else {
577 /* signal bit not set -> a real page is missing. */
578 get_task_struct(tsk);
579 set_task_state(tsk, TASK_UNINTERRUPTIBLE);
580 if (xchg(&tsk->thread.pfault_wait, 1) != 0) {
581 /* Completion interrupt was faster than the initial
582 * interrupt (swapped in a -1 for pfault_wait). Set
583 * pfault_wait back to zero and exit. This can be
584 * done safely because tsk is running in kernel
585 * mode and can't produce new pfaults. */
586 tsk->thread.pfault_wait = 0;
587 set_task_state(tsk, TASK_RUNNING);
588 put_task_struct(tsk);
589 } else
590 set_tsk_need_resched(tsk);
591 }
592 }
593
pfault_irq_init(void)594 void __init pfault_irq_init(void)
595 {
596 if (!MACHINE_IS_VM)
597 return;
598
599 /*
600 * Try to get pfault pseudo page faults going.
601 */
602 if (register_early_external_interrupt(0x2603, pfault_interrupt,
603 &ext_int_pfault) != 0)
604 panic("Couldn't request external interrupt 0x2603");
605
606 if (pfault_init() == 0)
607 return;
608
609 /* Tough luck, no pfault. */
610 pfault_disable = 1;
611 unregister_early_external_interrupt(0x2603, pfault_interrupt,
612 &ext_int_pfault);
613 }
614 #endif
615