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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/diag.h> | |
34 | #include <asm/pgtable.h> | |
35 | #include <asm/gmap.h> | |
36 | #include <asm/irq.h> | |
37 | #include <asm/mmu_context.h> | |
38 | #include <asm/facility.h> | |
39 | #include "../kernel/entry.h" | |
40 | ||
41 | #define __FAIL_ADDR_MASK -4096L | |
42 | #define __SUBCODE_MASK 0x0600 | |
43 | #define __PF_RES_FIELD 0x8000000000000000ULL | |
44 | ||
45 | #define VM_FAULT_BADCONTEXT 0x010000 | |
46 | #define VM_FAULT_BADMAP 0x020000 | |
47 | #define VM_FAULT_BADACCESS 0x040000 | |
48 | #define VM_FAULT_SIGNAL 0x080000 | |
49 | #define VM_FAULT_PFAULT 0x100000 | |
50 | ||
51 | static unsigned long store_indication __read_mostly; | |
52 | ||
53 | static int __init fault_init(void) | |
54 | { | |
55 | if (test_facility(75)) | |
56 | store_indication = 0xc00; | |
57 | return 0; | |
58 | } | |
59 | early_initcall(fault_init); | |
60 | ||
61 | static inline int notify_page_fault(struct pt_regs *regs) | |
62 | { | |
63 | int ret = 0; | |
64 | ||
65 | /* kprobe_running() needs smp_processor_id() */ | |
66 | if (kprobes_built_in() && !user_mode(regs)) { | |
67 | preempt_disable(); | |
68 | if (kprobe_running() && kprobe_fault_handler(regs, 14)) | |
69 | ret = 1; | |
70 | preempt_enable(); | |
71 | } | |
72 | return ret; | |
73 | } | |
74 | ||
75 | ||
76 | /* | |
77 | * Unlock any spinlocks which will prevent us from getting the | |
78 | * message out. | |
79 | */ | |
80 | void bust_spinlocks(int yes) | |
81 | { | |
82 | if (yes) { | |
83 | oops_in_progress = 1; | |
84 | } else { | |
85 | int loglevel_save = console_loglevel; | |
86 | console_unblank(); | |
87 | oops_in_progress = 0; | |
88 | /* | |
89 | * OK, the message is on the console. Now we call printk() | |
90 | * without oops_in_progress set so that printk will give klogd | |
91 | * a poke. Hold onto your hats... | |
92 | */ | |
93 | console_loglevel = 15; | |
94 | printk(" "); | |
95 | console_loglevel = loglevel_save; | |
96 | } | |
97 | } | |
98 | ||
99 | /* | |
100 | * Returns the address space associated with the fault. | |
101 | * Returns 0 for kernel space and 1 for user space. | |
102 | */ | |
103 | static inline int user_space_fault(struct pt_regs *regs) | |
104 | { | |
105 | unsigned long trans_exc_code; | |
106 | ||
107 | /* | |
108 | * The lowest two bits of the translation exception | |
109 | * identification indicate which paging table was used. | |
110 | */ | |
111 | trans_exc_code = regs->int_parm_long & 3; | |
112 | if (trans_exc_code == 3) /* home space -> kernel */ | |
113 | return 0; | |
114 | if (user_mode(regs)) | |
115 | return 1; | |
116 | if (trans_exc_code == 2) /* secondary space -> set_fs */ | |
117 | return current->thread.mm_segment.ar4; | |
118 | if (current->flags & PF_VCPU) | |
119 | return 1; | |
120 | return 0; | |
121 | } | |
122 | ||
123 | static int bad_address(void *p) | |
124 | { | |
125 | unsigned long dummy; | |
126 | ||
127 | return probe_kernel_address((unsigned long *)p, dummy); | |
128 | } | |
129 | ||
130 | static void dump_pagetable(unsigned long asce, unsigned long address) | |
131 | { | |
132 | unsigned long *table = __va(asce & PAGE_MASK); | |
133 | ||
134 | pr_alert("AS:%016lx ", asce); | |
135 | switch (asce & _ASCE_TYPE_MASK) { | |
136 | case _ASCE_TYPE_REGION1: | |
137 | table = table + ((address >> 53) & 0x7ff); | |
138 | if (bad_address(table)) | |
139 | goto bad; | |
140 | pr_cont("R1:%016lx ", *table); | |
141 | if (*table & _REGION_ENTRY_INVALID) | |
142 | goto out; | |
143 | table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); | |
144 | /* fallthrough */ | |
145 | case _ASCE_TYPE_REGION2: | |
146 | table = table + ((address >> 42) & 0x7ff); | |
147 | if (bad_address(table)) | |
148 | goto bad; | |
149 | pr_cont("R2:%016lx ", *table); | |
150 | if (*table & _REGION_ENTRY_INVALID) | |
151 | goto out; | |
152 | table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); | |
153 | /* fallthrough */ | |
154 | case _ASCE_TYPE_REGION3: | |
155 | table = table + ((address >> 31) & 0x7ff); | |
156 | if (bad_address(table)) | |
157 | goto bad; | |
158 | pr_cont("R3:%016lx ", *table); | |
159 | if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) | |
160 | goto out; | |
161 | table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); | |
162 | /* fallthrough */ | |
163 | case _ASCE_TYPE_SEGMENT: | |
164 | table = table + ((address >> 20) & 0x7ff); | |
165 | if (bad_address(table)) | |
166 | goto bad; | |
167 | pr_cont("S:%016lx ", *table); | |
168 | if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) | |
169 | goto out; | |
170 | table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); | |
171 | } | |
172 | table = table + ((address >> 12) & 0xff); | |
173 | if (bad_address(table)) | |
174 | goto bad; | |
175 | pr_cont("P:%016lx ", *table); | |
176 | out: | |
177 | pr_cont("\n"); | |
178 | return; | |
179 | bad: | |
180 | pr_cont("BAD\n"); | |
181 | } | |
182 | ||
183 | static void dump_fault_info(struct pt_regs *regs) | |
184 | { | |
185 | unsigned long asce; | |
186 | ||
187 | pr_alert("Failing address: %016lx TEID: %016lx\n", | |
188 | regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); | |
189 | pr_alert("Fault in "); | |
190 | switch (regs->int_parm_long & 3) { | |
191 | case 3: | |
192 | pr_cont("home space "); | |
193 | break; | |
194 | case 2: | |
195 | pr_cont("secondary space "); | |
196 | break; | |
197 | case 1: | |
198 | pr_cont("access register "); | |
199 | break; | |
200 | case 0: | |
201 | pr_cont("primary space "); | |
202 | break; | |
203 | } | |
204 | pr_cont("mode while using "); | |
205 | if (!user_space_fault(regs)) { | |
206 | asce = S390_lowcore.kernel_asce; | |
207 | pr_cont("kernel "); | |
208 | } | |
209 | #ifdef CONFIG_PGSTE | |
210 | else if ((current->flags & PF_VCPU) && S390_lowcore.gmap) { | |
211 | struct gmap *gmap = (struct gmap *)S390_lowcore.gmap; | |
212 | asce = gmap->asce; | |
213 | pr_cont("gmap "); | |
214 | } | |
215 | #endif | |
216 | else { | |
217 | asce = S390_lowcore.user_asce; | |
218 | pr_cont("user "); | |
219 | } | |
220 | pr_cont("ASCE.\n"); | |
221 | dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK); | |
222 | } | |
223 | ||
224 | int show_unhandled_signals = 1; | |
225 | ||
226 | void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) | |
227 | { | |
228 | if ((task_pid_nr(current) > 1) && !show_unhandled_signals) | |
229 | return; | |
230 | if (!unhandled_signal(current, signr)) | |
231 | return; | |
232 | if (!printk_ratelimit()) | |
233 | return; | |
234 | printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ", | |
235 | regs->int_code & 0xffff, regs->int_code >> 17); | |
236 | print_vma_addr(KERN_CONT "in ", regs->psw.addr); | |
237 | printk(KERN_CONT "\n"); | |
238 | if (is_mm_fault) | |
239 | dump_fault_info(regs); | |
240 | show_regs(regs); | |
241 | } | |
242 | ||
243 | /* | |
244 | * Send SIGSEGV to task. This is an external routine | |
245 | * to keep the stack usage of do_page_fault small. | |
246 | */ | |
247 | static noinline void do_sigsegv(struct pt_regs *regs, int si_code) | |
248 | { | |
249 | struct siginfo si; | |
250 | ||
251 | report_user_fault(regs, SIGSEGV, 1); | |
252 | si.si_signo = SIGSEGV; | |
253 | si.si_errno = 0; | |
254 | si.si_code = si_code; | |
255 | si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); | |
256 | force_sig_info(SIGSEGV, &si, current); | |
257 | } | |
258 | ||
259 | static noinline void do_no_context(struct pt_regs *regs) | |
260 | { | |
261 | const struct exception_table_entry *fixup; | |
262 | ||
263 | /* Are we prepared to handle this kernel fault? */ | |
264 | fixup = search_exception_tables(regs->psw.addr); | |
265 | if (fixup) { | |
266 | regs->psw.addr = extable_fixup(fixup); | |
267 | return; | |
268 | } | |
269 | ||
270 | /* | |
271 | * Oops. The kernel tried to access some bad page. We'll have to | |
272 | * terminate things with extreme prejudice. | |
273 | */ | |
274 | if (!user_space_fault(regs)) | |
275 | printk(KERN_ALERT "Unable to handle kernel pointer dereference" | |
276 | " in virtual kernel address space\n"); | |
277 | else | |
278 | printk(KERN_ALERT "Unable to handle kernel paging request" | |
279 | " in virtual user address space\n"); | |
280 | dump_fault_info(regs); | |
281 | die(regs, "Oops"); | |
282 | do_exit(SIGKILL); | |
283 | } | |
284 | ||
285 | static noinline void do_low_address(struct pt_regs *regs) | |
286 | { | |
287 | /* Low-address protection hit in kernel mode means | |
288 | NULL pointer write access in kernel mode. */ | |
289 | if (regs->psw.mask & PSW_MASK_PSTATE) { | |
290 | /* Low-address protection hit in user mode 'cannot happen'. */ | |
291 | die (regs, "Low-address protection"); | |
292 | do_exit(SIGKILL); | |
293 | } | |
294 | ||
295 | do_no_context(regs); | |
296 | } | |
297 | ||
298 | static noinline void do_sigbus(struct pt_regs *regs) | |
299 | { | |
300 | struct task_struct *tsk = current; | |
301 | struct siginfo si; | |
302 | ||
303 | /* | |
304 | * Send a sigbus, regardless of whether we were in kernel | |
305 | * or user mode. | |
306 | */ | |
307 | si.si_signo = SIGBUS; | |
308 | si.si_errno = 0; | |
309 | si.si_code = BUS_ADRERR; | |
310 | si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); | |
311 | force_sig_info(SIGBUS, &si, tsk); | |
312 | } | |
313 | ||
314 | static noinline void do_fault_error(struct pt_regs *regs, int fault) | |
315 | { | |
316 | int si_code; | |
317 | ||
318 | switch (fault) { | |
319 | case VM_FAULT_BADACCESS: | |
320 | case VM_FAULT_BADMAP: | |
321 | /* Bad memory access. Check if it is kernel or user space. */ | |
322 | if (user_mode(regs)) { | |
323 | /* User mode accesses just cause a SIGSEGV */ | |
324 | si_code = (fault == VM_FAULT_BADMAP) ? | |
325 | SEGV_MAPERR : SEGV_ACCERR; | |
326 | do_sigsegv(regs, si_code); | |
327 | return; | |
328 | } | |
329 | case VM_FAULT_BADCONTEXT: | |
330 | case VM_FAULT_PFAULT: | |
331 | do_no_context(regs); | |
332 | break; | |
333 | case VM_FAULT_SIGNAL: | |
334 | if (!user_mode(regs)) | |
335 | do_no_context(regs); | |
336 | break; | |
337 | default: /* fault & VM_FAULT_ERROR */ | |
338 | if (fault & VM_FAULT_OOM) { | |
339 | if (!user_mode(regs)) | |
340 | do_no_context(regs); | |
341 | else | |
342 | pagefault_out_of_memory(); | |
343 | } else if (fault & VM_FAULT_SIGSEGV) { | |
344 | /* Kernel mode? Handle exceptions or die */ | |
345 | if (!user_mode(regs)) | |
346 | do_no_context(regs); | |
347 | else | |
348 | do_sigsegv(regs, SEGV_MAPERR); | |
349 | } else if (fault & VM_FAULT_SIGBUS) { | |
350 | /* Kernel mode? Handle exceptions or die */ | |
351 | if (!user_mode(regs)) | |
352 | do_no_context(regs); | |
353 | else | |
354 | do_sigbus(regs); | |
355 | } else | |
356 | BUG(); | |
357 | break; | |
358 | } | |
359 | } | |
360 | ||
361 | /* | |
362 | * This routine handles page faults. It determines the address, | |
363 | * and the problem, and then passes it off to one of the appropriate | |
364 | * routines. | |
365 | * | |
366 | * interruption code (int_code): | |
367 | * 04 Protection -> Write-Protection (suprression) | |
368 | * 10 Segment translation -> Not present (nullification) | |
369 | * 11 Page translation -> Not present (nullification) | |
370 | * 3b Region third trans. -> Not present (nullification) | |
371 | */ | |
372 | static inline int do_exception(struct pt_regs *regs, int access) | |
373 | { | |
374 | #ifdef CONFIG_PGSTE | |
375 | struct gmap *gmap; | |
376 | #endif | |
377 | struct task_struct *tsk; | |
378 | struct mm_struct *mm; | |
379 | struct vm_area_struct *vma; | |
380 | unsigned long trans_exc_code; | |
381 | unsigned long address; | |
382 | unsigned int flags; | |
383 | int fault; | |
384 | ||
385 | tsk = current; | |
386 | /* | |
387 | * The instruction that caused the program check has | |
388 | * been nullified. Don't signal single step via SIGTRAP. | |
389 | */ | |
390 | clear_pt_regs_flag(regs, PIF_PER_TRAP); | |
391 | ||
392 | if (notify_page_fault(regs)) | |
393 | return 0; | |
394 | ||
395 | mm = tsk->mm; | |
396 | trans_exc_code = regs->int_parm_long; | |
397 | ||
398 | /* | |
399 | * Verify that the fault happened in user space, that | |
400 | * we are not in an interrupt and that there is a | |
401 | * user context. | |
402 | */ | |
403 | fault = VM_FAULT_BADCONTEXT; | |
404 | if (unlikely(!user_space_fault(regs) || faulthandler_disabled() || !mm)) | |
405 | goto out; | |
406 | ||
407 | address = trans_exc_code & __FAIL_ADDR_MASK; | |
408 | perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); | |
409 | flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; | |
410 | if (user_mode(regs)) | |
411 | flags |= FAULT_FLAG_USER; | |
412 | if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) | |
413 | flags |= FAULT_FLAG_WRITE; | |
414 | down_read(&mm->mmap_sem); | |
415 | ||
416 | #ifdef CONFIG_PGSTE | |
417 | gmap = (current->flags & PF_VCPU) ? | |
418 | (struct gmap *) S390_lowcore.gmap : NULL; | |
419 | if (gmap) { | |
420 | current->thread.gmap_addr = address; | |
421 | address = __gmap_translate(gmap, address); | |
422 | if (address == -EFAULT) { | |
423 | fault = VM_FAULT_BADMAP; | |
424 | goto out_up; | |
425 | } | |
426 | if (gmap->pfault_enabled) | |
427 | flags |= FAULT_FLAG_RETRY_NOWAIT; | |
428 | } | |
429 | #endif | |
430 | ||
431 | retry: | |
432 | fault = VM_FAULT_BADMAP; | |
433 | vma = find_vma(mm, address); | |
434 | if (!vma) | |
435 | goto out_up; | |
436 | ||
437 | if (unlikely(vma->vm_start > address)) { | |
438 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
439 | goto out_up; | |
440 | if (expand_stack(vma, address)) | |
441 | goto out_up; | |
442 | } | |
443 | ||
444 | /* | |
445 | * Ok, we have a good vm_area for this memory access, so | |
446 | * we can handle it.. | |
447 | */ | |
448 | fault = VM_FAULT_BADACCESS; | |
449 | if (unlikely(!(vma->vm_flags & access))) | |
450 | goto out_up; | |
451 | ||
452 | if (is_vm_hugetlb_page(vma)) | |
453 | address &= HPAGE_MASK; | |
454 | /* | |
455 | * If for any reason at all we couldn't handle the fault, | |
456 | * make sure we exit gracefully rather than endlessly redo | |
457 | * the fault. | |
458 | */ | |
459 | fault = handle_mm_fault(mm, vma, address, flags); | |
460 | /* No reason to continue if interrupted by SIGKILL. */ | |
461 | if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { | |
462 | fault = VM_FAULT_SIGNAL; | |
463 | goto out; | |
464 | } | |
465 | if (unlikely(fault & VM_FAULT_ERROR)) | |
466 | goto out_up; | |
467 | ||
468 | /* | |
469 | * Major/minor page fault accounting is only done on the | |
470 | * initial attempt. If we go through a retry, it is extremely | |
471 | * likely that the page will be found in page cache at that point. | |
472 | */ | |
473 | if (flags & FAULT_FLAG_ALLOW_RETRY) { | |
474 | if (fault & VM_FAULT_MAJOR) { | |
475 | tsk->maj_flt++; | |
476 | perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, | |
477 | regs, address); | |
478 | } else { | |
479 | tsk->min_flt++; | |
480 | perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, | |
481 | regs, address); | |
482 | } | |
483 | if (fault & VM_FAULT_RETRY) { | |
484 | #ifdef CONFIG_PGSTE | |
485 | if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) { | |
486 | /* FAULT_FLAG_RETRY_NOWAIT has been set, | |
487 | * mmap_sem has not been released */ | |
488 | current->thread.gmap_pfault = 1; | |
489 | fault = VM_FAULT_PFAULT; | |
490 | goto out_up; | |
491 | } | |
492 | #endif | |
493 | /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk | |
494 | * of starvation. */ | |
495 | flags &= ~(FAULT_FLAG_ALLOW_RETRY | | |
496 | FAULT_FLAG_RETRY_NOWAIT); | |
497 | flags |= FAULT_FLAG_TRIED; | |
498 | down_read(&mm->mmap_sem); | |
499 | goto retry; | |
500 | } | |
501 | } | |
502 | #ifdef CONFIG_PGSTE | |
503 | if (gmap) { | |
504 | address = __gmap_link(gmap, current->thread.gmap_addr, | |
505 | address); | |
506 | if (address == -EFAULT) { | |
507 | fault = VM_FAULT_BADMAP; | |
508 | goto out_up; | |
509 | } | |
510 | if (address == -ENOMEM) { | |
511 | fault = VM_FAULT_OOM; | |
512 | goto out_up; | |
513 | } | |
514 | } | |
515 | #endif | |
516 | fault = 0; | |
517 | out_up: | |
518 | up_read(&mm->mmap_sem); | |
519 | out: | |
520 | return fault; | |
521 | } | |
522 | ||
523 | void do_protection_exception(struct pt_regs *regs) | |
524 | { | |
525 | unsigned long trans_exc_code; | |
526 | int fault; | |
527 | ||
528 | trans_exc_code = regs->int_parm_long; | |
529 | /* | |
530 | * Protection exceptions are suppressing, decrement psw address. | |
531 | * The exception to this rule are aborted transactions, for these | |
532 | * the PSW already points to the correct location. | |
533 | */ | |
534 | if (!(regs->int_code & 0x200)) | |
535 | regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); | |
536 | /* | |
537 | * Check for low-address protection. This needs to be treated | |
538 | * as a special case because the translation exception code | |
539 | * field is not guaranteed to contain valid data in this case. | |
540 | */ | |
541 | if (unlikely(!(trans_exc_code & 4))) { | |
542 | do_low_address(regs); | |
543 | return; | |
544 | } | |
545 | fault = do_exception(regs, VM_WRITE); | |
546 | if (unlikely(fault)) | |
547 | do_fault_error(regs, fault); | |
548 | } | |
549 | NOKPROBE_SYMBOL(do_protection_exception); | |
550 | ||
551 | void do_dat_exception(struct pt_regs *regs) | |
552 | { | |
553 | int access, fault; | |
554 | ||
555 | access = VM_READ | VM_EXEC | VM_WRITE; | |
556 | fault = do_exception(regs, access); | |
557 | if (unlikely(fault)) | |
558 | do_fault_error(regs, fault); | |
559 | } | |
560 | NOKPROBE_SYMBOL(do_dat_exception); | |
561 | ||
562 | #ifdef CONFIG_PFAULT | |
563 | /* | |
564 | * 'pfault' pseudo page faults routines. | |
565 | */ | |
566 | static int pfault_disable; | |
567 | ||
568 | static int __init nopfault(char *str) | |
569 | { | |
570 | pfault_disable = 1; | |
571 | return 1; | |
572 | } | |
573 | ||
574 | __setup("nopfault", nopfault); | |
575 | ||
576 | struct pfault_refbk { | |
577 | u16 refdiagc; | |
578 | u16 reffcode; | |
579 | u16 refdwlen; | |
580 | u16 refversn; | |
581 | u64 refgaddr; | |
582 | u64 refselmk; | |
583 | u64 refcmpmk; | |
584 | u64 reserved; | |
585 | } __attribute__ ((packed, aligned(8))); | |
586 | ||
587 | int pfault_init(void) | |
588 | { | |
589 | struct pfault_refbk refbk = { | |
590 | .refdiagc = 0x258, | |
591 | .reffcode = 0, | |
592 | .refdwlen = 5, | |
593 | .refversn = 2, | |
594 | .refgaddr = __LC_LPP, | |
595 | .refselmk = 1ULL << 48, | |
596 | .refcmpmk = 1ULL << 48, | |
597 | .reserved = __PF_RES_FIELD }; | |
598 | int rc; | |
599 | ||
600 | if (pfault_disable) | |
601 | return -1; | |
602 | diag_stat_inc(DIAG_STAT_X258); | |
603 | asm volatile( | |
604 | " diag %1,%0,0x258\n" | |
605 | "0: j 2f\n" | |
606 | "1: la %0,8\n" | |
607 | "2:\n" | |
608 | EX_TABLE(0b,1b) | |
609 | : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc"); | |
610 | return rc; | |
611 | } | |
612 | ||
613 | void pfault_fini(void) | |
614 | { | |
615 | struct pfault_refbk refbk = { | |
616 | .refdiagc = 0x258, | |
617 | .reffcode = 1, | |
618 | .refdwlen = 5, | |
619 | .refversn = 2, | |
620 | }; | |
621 | ||
622 | if (pfault_disable) | |
623 | return; | |
624 | diag_stat_inc(DIAG_STAT_X258); | |
625 | asm volatile( | |
626 | " diag %0,0,0x258\n" | |
627 | "0:\n" | |
628 | EX_TABLE(0b,0b) | |
629 | : : "a" (&refbk), "m" (refbk) : "cc"); | |
630 | } | |
631 | ||
632 | static DEFINE_SPINLOCK(pfault_lock); | |
633 | static LIST_HEAD(pfault_list); | |
634 | ||
635 | #define PF_COMPLETE 0x0080 | |
636 | ||
637 | /* | |
638 | * The mechanism of our pfault code: if Linux is running as guest, runs a user | |
639 | * space process and the user space process accesses a page that the host has | |
640 | * paged out we get a pfault interrupt. | |
641 | * | |
642 | * This allows us, within the guest, to schedule a different process. Without | |
643 | * this mechanism the host would have to suspend the whole virtual cpu until | |
644 | * the page has been paged in. | |
645 | * | |
646 | * So when we get such an interrupt then we set the state of the current task | |
647 | * to uninterruptible and also set the need_resched flag. Both happens within | |
648 | * interrupt context(!). If we later on want to return to user space we | |
649 | * recognize the need_resched flag and then call schedule(). It's not very | |
650 | * obvious how this works... | |
651 | * | |
652 | * Of course we have a lot of additional fun with the completion interrupt (-> | |
653 | * host signals that a page of a process has been paged in and the process can | |
654 | * continue to run). This interrupt can arrive on any cpu and, since we have | |
655 | * virtual cpus, actually appear before the interrupt that signals that a page | |
656 | * is missing. | |
657 | */ | |
658 | static void pfault_interrupt(struct ext_code ext_code, | |
659 | unsigned int param32, unsigned long param64) | |
660 | { | |
661 | struct task_struct *tsk; | |
662 | __u16 subcode; | |
663 | pid_t pid; | |
664 | ||
665 | /* | |
666 | * Get the external interruption subcode & pfault initial/completion | |
667 | * signal bit. VM stores this in the 'cpu address' field associated | |
668 | * with the external interrupt. | |
669 | */ | |
670 | subcode = ext_code.subcode; | |
671 | if ((subcode & 0xff00) != __SUBCODE_MASK) | |
672 | return; | |
673 | inc_irq_stat(IRQEXT_PFL); | |
674 | /* Get the token (= pid of the affected task). */ | |
675 | pid = param64 & LPP_PFAULT_PID_MASK; | |
676 | rcu_read_lock(); | |
677 | tsk = find_task_by_pid_ns(pid, &init_pid_ns); | |
678 | if (tsk) | |
679 | get_task_struct(tsk); | |
680 | rcu_read_unlock(); | |
681 | if (!tsk) | |
682 | return; | |
683 | spin_lock(&pfault_lock); | |
684 | if (subcode & PF_COMPLETE) { | |
685 | /* signal bit is set -> a page has been swapped in by VM */ | |
686 | if (tsk->thread.pfault_wait == 1) { | |
687 | /* Initial interrupt was faster than the completion | |
688 | * interrupt. pfault_wait is valid. Set pfault_wait | |
689 | * back to zero and wake up the process. This can | |
690 | * safely be done because the task is still sleeping | |
691 | * and can't produce new pfaults. */ | |
692 | tsk->thread.pfault_wait = 0; | |
693 | list_del(&tsk->thread.list); | |
694 | wake_up_process(tsk); | |
695 | put_task_struct(tsk); | |
696 | } else { | |
697 | /* Completion interrupt was faster than initial | |
698 | * interrupt. Set pfault_wait to -1 so the initial | |
699 | * interrupt doesn't put the task to sleep. | |
700 | * If the task is not running, ignore the completion | |
701 | * interrupt since it must be a leftover of a PFAULT | |
702 | * CANCEL operation which didn't remove all pending | |
703 | * completion interrupts. */ | |
704 | if (tsk->state == TASK_RUNNING) | |
705 | tsk->thread.pfault_wait = -1; | |
706 | } | |
707 | } else { | |
708 | /* signal bit not set -> a real page is missing. */ | |
709 | if (WARN_ON_ONCE(tsk != current)) | |
710 | goto out; | |
711 | if (tsk->thread.pfault_wait == 1) { | |
712 | /* Already on the list with a reference: put to sleep */ | |
713 | goto block; | |
714 | } else if (tsk->thread.pfault_wait == -1) { | |
715 | /* Completion interrupt was faster than the initial | |
716 | * interrupt (pfault_wait == -1). Set pfault_wait | |
717 | * back to zero and exit. */ | |
718 | tsk->thread.pfault_wait = 0; | |
719 | } else { | |
720 | /* Initial interrupt arrived before completion | |
721 | * interrupt. Let the task sleep. | |
722 | * An extra task reference is needed since a different | |
723 | * cpu may set the task state to TASK_RUNNING again | |
724 | * before the scheduler is reached. */ | |
725 | get_task_struct(tsk); | |
726 | tsk->thread.pfault_wait = 1; | |
727 | list_add(&tsk->thread.list, &pfault_list); | |
728 | block: | |
729 | /* Since this must be a userspace fault, there | |
730 | * is no kernel task state to trample. Rely on the | |
731 | * return to userspace schedule() to block. */ | |
732 | __set_current_state(TASK_UNINTERRUPTIBLE); | |
733 | set_tsk_need_resched(tsk); | |
734 | } | |
735 | } | |
736 | out: | |
737 | spin_unlock(&pfault_lock); | |
738 | put_task_struct(tsk); | |
739 | } | |
740 | ||
741 | static int pfault_cpu_notify(struct notifier_block *self, unsigned long action, | |
742 | void *hcpu) | |
743 | { | |
744 | struct thread_struct *thread, *next; | |
745 | struct task_struct *tsk; | |
746 | ||
747 | switch (action & ~CPU_TASKS_FROZEN) { | |
748 | case CPU_DEAD: | |
749 | spin_lock_irq(&pfault_lock); | |
750 | list_for_each_entry_safe(thread, next, &pfault_list, list) { | |
751 | thread->pfault_wait = 0; | |
752 | list_del(&thread->list); | |
753 | tsk = container_of(thread, struct task_struct, thread); | |
754 | wake_up_process(tsk); | |
755 | put_task_struct(tsk); | |
756 | } | |
757 | spin_unlock_irq(&pfault_lock); | |
758 | break; | |
759 | default: | |
760 | break; | |
761 | } | |
762 | return NOTIFY_OK; | |
763 | } | |
764 | ||
765 | static int __init pfault_irq_init(void) | |
766 | { | |
767 | int rc; | |
768 | ||
769 | rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); | |
770 | if (rc) | |
771 | goto out_extint; | |
772 | rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; | |
773 | if (rc) | |
774 | goto out_pfault; | |
775 | irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); | |
776 | hotcpu_notifier(pfault_cpu_notify, 0); | |
777 | return 0; | |
778 | ||
779 | out_pfault: | |
780 | unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); | |
781 | out_extint: | |
782 | pfault_disable = 1; | |
783 | return rc; | |
784 | } | |
785 | early_initcall(pfault_irq_init); | |
786 | ||
787 | #endif /* CONFIG_PFAULT */ |