Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/arch/arm/mm/fault.c
4 *
5 * Copyright (C) 1995 Linus Torvalds
6 * Modifications for ARM processor (c) 1995-2004 Russell King
7 */
8#include <linux/extable.h>
9#include <linux/signal.h>
10#include <linux/mm.h>
11#include <linux/hardirq.h>
12#include <linux/init.h>
13#include <linux/kprobes.h>
14#include <linux/uaccess.h>
15#include <linux/page-flags.h>
16#include <linux/sched/signal.h>
17#include <linux/sched/debug.h>
18#include <linux/highmem.h>
19#include <linux/perf_event.h>
20#include <linux/kfence.h>
21
22#include <asm/system_misc.h>
23#include <asm/system_info.h>
24#include <asm/tlbflush.h>
25
26#include "fault.h"
27
28#ifdef CONFIG_MMU
29
30bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
31{
32 unsigned long addr = (unsigned long)unsafe_src;
33
34 return addr >= TASK_SIZE && ULONG_MAX - addr >= size;
35}
36
37/*
38 * This is useful to dump out the page tables associated with
39 * 'addr' in mm 'mm'.
40 */
41void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
42{
43 pgd_t *pgd;
44
45 if (!mm)
46 mm = &init_mm;
47
48 pgd = pgd_offset(mm, addr);
49 printk("%s[%08lx] *pgd=%08llx", lvl, addr, (long long)pgd_val(*pgd));
50
51 do {
52 p4d_t *p4d;
53 pud_t *pud;
54 pmd_t *pmd;
55 pte_t *pte;
56
57 p4d = p4d_offset(pgd, addr);
58 if (p4d_none(*p4d))
59 break;
60
61 if (p4d_bad(*p4d)) {
62 pr_cont("(bad)");
63 break;
64 }
65
66 pud = pud_offset(p4d, addr);
67 if (PTRS_PER_PUD != 1)
68 pr_cont(", *pud=%08llx", (long long)pud_val(*pud));
69
70 if (pud_none(*pud))
71 break;
72
73 if (pud_bad(*pud)) {
74 pr_cont("(bad)");
75 break;
76 }
77
78 pmd = pmd_offset(pud, addr);
79 if (PTRS_PER_PMD != 1)
80 pr_cont(", *pmd=%08llx", (long long)pmd_val(*pmd));
81
82 if (pmd_none(*pmd))
83 break;
84
85 if (pmd_bad(*pmd)) {
86 pr_cont("(bad)");
87 break;
88 }
89
90 /* We must not map this if we have highmem enabled */
91 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
92 break;
93
94 pte = pte_offset_map(pmd, addr);
95 if (!pte)
96 break;
97
98 pr_cont(", *pte=%08llx", (long long)pte_val(*pte));
99#ifndef CONFIG_ARM_LPAE
100 pr_cont(", *ppte=%08llx",
101 (long long)pte_val(pte[PTE_HWTABLE_PTRS]));
102#endif
103 pte_unmap(pte);
104 } while(0);
105
106 pr_cont("\n");
107}
108#else /* CONFIG_MMU */
109void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
110{ }
111#endif /* CONFIG_MMU */
112
113static inline bool is_write_fault(unsigned int fsr)
114{
115 return (fsr & FSR_WRITE) && !(fsr & FSR_CM);
116}
117
118static inline bool is_translation_fault(unsigned int fsr)
119{
120 int fs = fsr_fs(fsr);
121#ifdef CONFIG_ARM_LPAE
122 if ((fs & FS_MMU_NOLL_MASK) == FS_TRANS_NOLL)
123 return true;
124#else
125 if (fs == FS_L1_TRANS || fs == FS_L2_TRANS)
126 return true;
127#endif
128 return false;
129}
130
131static void die_kernel_fault(const char *msg, struct mm_struct *mm,
132 unsigned long addr, unsigned int fsr,
133 struct pt_regs *regs)
134{
135 bust_spinlocks(1);
136 pr_alert("8<--- cut here ---\n");
137 pr_alert("Unable to handle kernel %s at virtual address %08lx when %s\n",
138 msg, addr, fsr & FSR_LNX_PF ? "execute" :
139 fsr & FSR_WRITE ? "write" : "read");
140
141 show_pte(KERN_ALERT, mm, addr);
142 die("Oops", regs, fsr);
143 bust_spinlocks(0);
144 make_task_dead(SIGKILL);
145}
146
147/*
148 * Oops. The kernel tried to access some page that wasn't present.
149 */
150static void
151__do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
152 struct pt_regs *regs)
153{
154 const char *msg;
155 /*
156 * Are we prepared to handle this kernel fault?
157 */
158 if (fixup_exception(regs))
159 return;
160
161 /*
162 * No handler, we'll have to terminate things with extreme prejudice.
163 */
164 if (addr < PAGE_SIZE) {
165 msg = "NULL pointer dereference";
166 } else {
167 if (is_translation_fault(fsr) &&
168 kfence_handle_page_fault(addr, is_write_fault(fsr), regs))
169 return;
170
171 msg = "paging request";
172 }
173
174 die_kernel_fault(msg, mm, addr, fsr, regs);
175}
176
177/*
178 * Something tried to access memory that isn't in our memory map..
179 * User mode accesses just cause a SIGSEGV
180 */
181static void
182__do_user_fault(unsigned long addr, unsigned int fsr, unsigned int sig,
183 int code, struct pt_regs *regs)
184{
185 struct task_struct *tsk = current;
186
187 if (addr > TASK_SIZE)
188 harden_branch_predictor();
189
190#ifdef CONFIG_DEBUG_USER
191 if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
192 ((user_debug & UDBG_BUS) && (sig == SIGBUS))) {
193 pr_err("8<--- cut here ---\n");
194 pr_err("%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
195 tsk->comm, sig, addr, fsr);
196 show_pte(KERN_ERR, tsk->mm, addr);
197 show_regs(regs);
198 }
199#endif
200#ifndef CONFIG_KUSER_HELPERS
201 if ((sig == SIGSEGV) && ((addr & PAGE_MASK) == 0xffff0000))
202 printk_ratelimited(KERN_DEBUG
203 "%s: CONFIG_KUSER_HELPERS disabled at 0x%08lx\n",
204 tsk->comm, addr);
205#endif
206
207 tsk->thread.address = addr;
208 tsk->thread.error_code = fsr;
209 tsk->thread.trap_no = 14;
210 force_sig_fault(sig, code, (void __user *)addr);
211}
212
213void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
214{
215 struct task_struct *tsk = current;
216 struct mm_struct *mm = tsk->active_mm;
217
218 /*
219 * If we are in kernel mode at this point, we
220 * have no context to handle this fault with.
221 */
222 if (user_mode(regs))
223 __do_user_fault(addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
224 else
225 __do_kernel_fault(mm, addr, fsr, regs);
226}
227
228#ifdef CONFIG_MMU
229static inline bool is_permission_fault(unsigned int fsr)
230{
231 int fs = fsr_fs(fsr);
232#ifdef CONFIG_ARM_LPAE
233 if ((fs & FS_MMU_NOLL_MASK) == FS_PERM_NOLL)
234 return true;
235#else
236 if (fs == FS_L1_PERM || fs == FS_L2_PERM)
237 return true;
238#endif
239 return false;
240}
241
242#ifdef CONFIG_CPU_TTBR0_PAN
243static inline bool ttbr0_usermode_access_allowed(struct pt_regs *regs)
244{
245 struct svc_pt_regs *svcregs;
246
247 /* If we are in user mode: permission granted */
248 if (user_mode(regs))
249 return true;
250
251 /* uaccess state saved above pt_regs on SVC exception entry */
252 svcregs = to_svc_pt_regs(regs);
253
254 return !(svcregs->ttbcr & TTBCR_EPD0);
255}
256#else
257static inline bool ttbr0_usermode_access_allowed(struct pt_regs *regs)
258{
259 return true;
260}
261#endif
262
263static int __kprobes
264do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
265{
266 struct mm_struct *mm = current->mm;
267 struct vm_area_struct *vma;
268 int sig, code;
269 vm_fault_t fault;
270 unsigned int flags = FAULT_FLAG_DEFAULT;
271 unsigned long vm_flags = VM_ACCESS_FLAGS;
272
273 if (kprobe_page_fault(regs, fsr))
274 return 0;
275
276
277 /* Enable interrupts if they were enabled in the parent context. */
278 if (interrupts_enabled(regs))
279 local_irq_enable();
280
281 /*
282 * If we're in an interrupt or have no user
283 * context, we must not take the fault..
284 */
285 if (faulthandler_disabled() || !mm)
286 goto no_context;
287
288 if (user_mode(regs))
289 flags |= FAULT_FLAG_USER;
290
291 if (is_write_fault(fsr)) {
292 flags |= FAULT_FLAG_WRITE;
293 vm_flags = VM_WRITE;
294 }
295
296 if (fsr & FSR_LNX_PF) {
297 vm_flags = VM_EXEC;
298
299 if (is_permission_fault(fsr) && !user_mode(regs))
300 die_kernel_fault("execution of memory",
301 mm, addr, fsr, regs);
302 }
303
304 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
305
306 /*
307 * Privileged access aborts with CONFIG_CPU_TTBR0_PAN enabled are
308 * routed via the translation fault mechanism. Check whether uaccess
309 * is disabled while in kernel mode.
310 */
311 if (!ttbr0_usermode_access_allowed(regs))
312 goto no_context;
313
314 if (!(flags & FAULT_FLAG_USER))
315 goto lock_mmap;
316
317 vma = lock_vma_under_rcu(mm, addr);
318 if (!vma)
319 goto lock_mmap;
320
321 if (!(vma->vm_flags & vm_flags)) {
322 vma_end_read(vma);
323 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
324 fault = 0;
325 code = SEGV_ACCERR;
326 goto bad_area;
327 }
328 fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
329 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
330 vma_end_read(vma);
331
332 if (!(fault & VM_FAULT_RETRY)) {
333 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
334 goto done;
335 }
336 count_vm_vma_lock_event(VMA_LOCK_RETRY);
337 if (fault & VM_FAULT_MAJOR)
338 flags |= FAULT_FLAG_TRIED;
339
340 /* Quick path to respond to signals */
341 if (fault_signal_pending(fault, regs)) {
342 if (!user_mode(regs))
343 goto no_context;
344 return 0;
345 }
346lock_mmap:
347
348retry:
349 vma = lock_mm_and_find_vma(mm, addr, regs);
350 if (unlikely(!vma)) {
351 fault = 0;
352 code = SEGV_MAPERR;
353 goto bad_area;
354 }
355
356 /*
357 * ok, we have a good vm_area for this memory access, check the
358 * permissions on the VMA allow for the fault which occurred.
359 */
360 if (!(vma->vm_flags & vm_flags)) {
361 mmap_read_unlock(mm);
362 fault = 0;
363 code = SEGV_ACCERR;
364 goto bad_area;
365 }
366
367 fault = handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
368
369 /* If we need to retry but a fatal signal is pending, handle the
370 * signal first. We do not need to release the mmap_lock because
371 * it would already be released in __lock_page_or_retry in
372 * mm/filemap.c. */
373 if (fault_signal_pending(fault, regs)) {
374 if (!user_mode(regs))
375 goto no_context;
376 return 0;
377 }
378
379 /* The fault is fully completed (including releasing mmap lock) */
380 if (fault & VM_FAULT_COMPLETED)
381 return 0;
382
383 if (!(fault & VM_FAULT_ERROR)) {
384 if (fault & VM_FAULT_RETRY) {
385 flags |= FAULT_FLAG_TRIED;
386 goto retry;
387 }
388 }
389
390 mmap_read_unlock(mm);
391done:
392
393 /* Handle the "normal" case first */
394 if (likely(!(fault & VM_FAULT_ERROR)))
395 return 0;
396
397 code = SEGV_MAPERR;
398bad_area:
399 /*
400 * If we are in kernel mode at this point, we
401 * have no context to handle this fault with.
402 */
403 if (!user_mode(regs))
404 goto no_context;
405
406 if (fault & VM_FAULT_OOM) {
407 /*
408 * We ran out of memory, call the OOM killer, and return to
409 * userspace (which will retry the fault, or kill us if we
410 * got oom-killed)
411 */
412 pagefault_out_of_memory();
413 return 0;
414 }
415
416 if (fault & VM_FAULT_SIGBUS) {
417 /*
418 * We had some memory, but were unable to
419 * successfully fix up this page fault.
420 */
421 sig = SIGBUS;
422 code = BUS_ADRERR;
423 } else {
424 /*
425 * Something tried to access memory that
426 * isn't in our memory map..
427 */
428 sig = SIGSEGV;
429 }
430
431 __do_user_fault(addr, fsr, sig, code, regs);
432 return 0;
433
434no_context:
435 __do_kernel_fault(mm, addr, fsr, regs);
436 return 0;
437}
438#else /* CONFIG_MMU */
439static int
440do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
441{
442 return 0;
443}
444#endif /* CONFIG_MMU */
445
446/*
447 * First Level Translation Fault Handler
448 *
449 * We enter here because the first level page table doesn't contain
450 * a valid entry for the address.
451 *
452 * If the address is in kernel space (>= TASK_SIZE), then we are
453 * probably faulting in the vmalloc() area.
454 *
455 * If the init_task's first level page tables contains the relevant
456 * entry, we copy the it to this task. If not, we send the process
457 * a signal, fixup the exception, or oops the kernel.
458 *
459 * NOTE! We MUST NOT take any locks for this case. We may be in an
460 * interrupt or a critical region, and should only copy the information
461 * from the master page table, nothing more.
462 */
463#ifdef CONFIG_MMU
464static int __kprobes
465do_translation_fault(unsigned long addr, unsigned int fsr,
466 struct pt_regs *regs)
467{
468 unsigned int index;
469 pgd_t *pgd, *pgd_k;
470 p4d_t *p4d, *p4d_k;
471 pud_t *pud, *pud_k;
472 pmd_t *pmd, *pmd_k;
473
474 if (addr < TASK_SIZE)
475 return do_page_fault(addr, fsr, regs);
476
477 if (user_mode(regs))
478 goto bad_area;
479
480 index = pgd_index(addr);
481
482 pgd = cpu_get_pgd() + index;
483 pgd_k = init_mm.pgd + index;
484
485 p4d = p4d_offset(pgd, addr);
486 p4d_k = p4d_offset(pgd_k, addr);
487
488 if (p4d_none(*p4d_k))
489 goto bad_area;
490 if (!p4d_present(*p4d))
491 set_p4d(p4d, *p4d_k);
492
493 pud = pud_offset(p4d, addr);
494 pud_k = pud_offset(p4d_k, addr);
495
496 if (pud_none(*pud_k))
497 goto bad_area;
498 if (!pud_present(*pud))
499 set_pud(pud, *pud_k);
500
501 pmd = pmd_offset(pud, addr);
502 pmd_k = pmd_offset(pud_k, addr);
503
504#ifdef CONFIG_ARM_LPAE
505 /*
506 * Only one hardware entry per PMD with LPAE.
507 */
508 index = 0;
509#else
510 /*
511 * On ARM one Linux PGD entry contains two hardware entries (see page
512 * tables layout in pgtable.h). We normally guarantee that we always
513 * fill both L1 entries. But create_mapping() doesn't follow the rule.
514 * It can create inidividual L1 entries, so here we have to call
515 * pmd_none() check for the entry really corresponded to address, not
516 * for the first of pair.
517 */
518 index = (addr >> SECTION_SHIFT) & 1;
519#endif
520 if (pmd_none(pmd_k[index]))
521 goto bad_area;
522
523 copy_pmd(pmd, pmd_k);
524 return 0;
525
526bad_area:
527 do_bad_area(addr, fsr, regs);
528 return 0;
529}
530#else /* CONFIG_MMU */
531static int
532do_translation_fault(unsigned long addr, unsigned int fsr,
533 struct pt_regs *regs)
534{
535 return 0;
536}
537#endif /* CONFIG_MMU */
538
539/*
540 * Some section permission faults need to be handled gracefully.
541 * They can happen due to a __{get,put}_user during an oops.
542 */
543#ifndef CONFIG_ARM_LPAE
544static int
545do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
546{
547 do_bad_area(addr, fsr, regs);
548 return 0;
549}
550#endif /* CONFIG_ARM_LPAE */
551
552/*
553 * This abort handler always returns "fault".
554 */
555static int
556do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
557{
558 return 1;
559}
560
561struct fsr_info {
562 int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
563 int sig;
564 int code;
565 const char *name;
566};
567
568/* FSR definition */
569#ifdef CONFIG_ARM_LPAE
570#include "fsr-3level.c"
571#else
572#include "fsr-2level.c"
573#endif
574
575void __init
576hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
577 int sig, int code, const char *name)
578{
579 if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
580 BUG();
581
582 fsr_info[nr].fn = fn;
583 fsr_info[nr].sig = sig;
584 fsr_info[nr].code = code;
585 fsr_info[nr].name = name;
586}
587
588/*
589 * Dispatch a data abort to the relevant handler.
590 */
591asmlinkage void
592do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
593{
594 const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
595
596 if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
597 return;
598
599 pr_alert("8<--- cut here ---\n");
600 pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
601 inf->name, fsr, addr);
602 show_pte(KERN_ALERT, current->mm, addr);
603
604 arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
605 fsr, 0);
606}
607
608void __init
609hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
610 int sig, int code, const char *name)
611{
612 if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
613 BUG();
614
615 ifsr_info[nr].fn = fn;
616 ifsr_info[nr].sig = sig;
617 ifsr_info[nr].code = code;
618 ifsr_info[nr].name = name;
619}
620
621asmlinkage void
622do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
623{
624 const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
625
626 if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
627 return;
628
629 pr_alert("8<--- cut here ---\n");
630 pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
631 inf->name, ifsr, addr);
632
633 arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
634 ifsr, 0);
635}
636
637/*
638 * Abort handler to be used only during first unmasking of asynchronous aborts
639 * on the boot CPU. This makes sure that the machine will not die if the
640 * firmware/bootloader left an imprecise abort pending for us to trip over.
641 */
642static int __init early_abort_handler(unsigned long addr, unsigned int fsr,
643 struct pt_regs *regs)
644{
645 pr_warn("Hit pending asynchronous external abort (FSR=0x%08x) during "
646 "first unmask, this is most likely caused by a "
647 "firmware/bootloader bug.\n", fsr);
648
649 return 0;
650}
651
652void __init early_abt_enable(void)
653{
654 fsr_info[FSR_FS_AEA].fn = early_abort_handler;
655 local_abt_enable();
656 fsr_info[FSR_FS_AEA].fn = do_bad;
657}
658
659#ifndef CONFIG_ARM_LPAE
660static int __init exceptions_init(void)
661{
662 if (cpu_architecture() >= CPU_ARCH_ARMv6) {
663 hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
664 "I-cache maintenance fault");
665 }
666
667 if (cpu_architecture() >= CPU_ARCH_ARMv7) {
668 /*
669 * TODO: Access flag faults introduced in ARMv6K.
670 * Runtime check for 'K' extension is needed
671 */
672 hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
673 "section access flag fault");
674 hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
675 "section access flag fault");
676 }
677
678 return 0;
679}
680
681arch_initcall(exceptions_init);
682#endif
1/*
2 * linux/arch/arm/mm/fault.c
3 *
4 * Copyright (C) 1995 Linus Torvalds
5 * Modifications for ARM processor (c) 1995-2004 Russell King
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11#include <linux/extable.h>
12#include <linux/signal.h>
13#include <linux/mm.h>
14#include <linux/hardirq.h>
15#include <linux/init.h>
16#include <linux/kprobes.h>
17#include <linux/uaccess.h>
18#include <linux/page-flags.h>
19#include <linux/sched/signal.h>
20#include <linux/sched/debug.h>
21#include <linux/highmem.h>
22#include <linux/perf_event.h>
23
24#include <asm/pgtable.h>
25#include <asm/system_misc.h>
26#include <asm/system_info.h>
27#include <asm/tlbflush.h>
28
29#include "fault.h"
30
31#ifdef CONFIG_MMU
32
33#ifdef CONFIG_KPROBES
34static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
35{
36 int ret = 0;
37
38 if (!user_mode(regs)) {
39 /* kprobe_running() needs smp_processor_id() */
40 preempt_disable();
41 if (kprobe_running() && kprobe_fault_handler(regs, fsr))
42 ret = 1;
43 preempt_enable();
44 }
45
46 return ret;
47}
48#else
49static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
50{
51 return 0;
52}
53#endif
54
55/*
56 * This is useful to dump out the page tables associated with
57 * 'addr' in mm 'mm'.
58 */
59void show_pte(struct mm_struct *mm, unsigned long addr)
60{
61 pgd_t *pgd;
62
63 if (!mm)
64 mm = &init_mm;
65
66 pr_alert("pgd = %p\n", mm->pgd);
67 pgd = pgd_offset(mm, addr);
68 pr_alert("[%08lx] *pgd=%08llx",
69 addr, (long long)pgd_val(*pgd));
70
71 do {
72 pud_t *pud;
73 pmd_t *pmd;
74 pte_t *pte;
75
76 if (pgd_none(*pgd))
77 break;
78
79 if (pgd_bad(*pgd)) {
80 pr_cont("(bad)");
81 break;
82 }
83
84 pud = pud_offset(pgd, addr);
85 if (PTRS_PER_PUD != 1)
86 pr_cont(", *pud=%08llx", (long long)pud_val(*pud));
87
88 if (pud_none(*pud))
89 break;
90
91 if (pud_bad(*pud)) {
92 pr_cont("(bad)");
93 break;
94 }
95
96 pmd = pmd_offset(pud, addr);
97 if (PTRS_PER_PMD != 1)
98 pr_cont(", *pmd=%08llx", (long long)pmd_val(*pmd));
99
100 if (pmd_none(*pmd))
101 break;
102
103 if (pmd_bad(*pmd)) {
104 pr_cont("(bad)");
105 break;
106 }
107
108 /* We must not map this if we have highmem enabled */
109 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
110 break;
111
112 pte = pte_offset_map(pmd, addr);
113 pr_cont(", *pte=%08llx", (long long)pte_val(*pte));
114#ifndef CONFIG_ARM_LPAE
115 pr_cont(", *ppte=%08llx",
116 (long long)pte_val(pte[PTE_HWTABLE_PTRS]));
117#endif
118 pte_unmap(pte);
119 } while(0);
120
121 pr_cont("\n");
122}
123#else /* CONFIG_MMU */
124void show_pte(struct mm_struct *mm, unsigned long addr)
125{ }
126#endif /* CONFIG_MMU */
127
128/*
129 * Oops. The kernel tried to access some page that wasn't present.
130 */
131static void
132__do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
133 struct pt_regs *regs)
134{
135 /*
136 * Are we prepared to handle this kernel fault?
137 */
138 if (fixup_exception(regs))
139 return;
140
141 /*
142 * No handler, we'll have to terminate things with extreme prejudice.
143 */
144 bust_spinlocks(1);
145 pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
146 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
147 "paging request", addr);
148
149 show_pte(mm, addr);
150 die("Oops", regs, fsr);
151 bust_spinlocks(0);
152 do_exit(SIGKILL);
153}
154
155/*
156 * Something tried to access memory that isn't in our memory map..
157 * User mode accesses just cause a SIGSEGV
158 */
159static void
160__do_user_fault(struct task_struct *tsk, unsigned long addr,
161 unsigned int fsr, unsigned int sig, int code,
162 struct pt_regs *regs)
163{
164 struct siginfo si;
165
166#ifdef CONFIG_DEBUG_USER
167 if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
168 ((user_debug & UDBG_BUS) && (sig == SIGBUS))) {
169 printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
170 tsk->comm, sig, addr, fsr);
171 show_pte(tsk->mm, addr);
172 show_regs(regs);
173 }
174#endif
175
176 tsk->thread.address = addr;
177 tsk->thread.error_code = fsr;
178 tsk->thread.trap_no = 14;
179 si.si_signo = sig;
180 si.si_errno = 0;
181 si.si_code = code;
182 si.si_addr = (void __user *)addr;
183 force_sig_info(sig, &si, tsk);
184}
185
186void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
187{
188 struct task_struct *tsk = current;
189 struct mm_struct *mm = tsk->active_mm;
190
191 /*
192 * If we are in kernel mode at this point, we
193 * have no context to handle this fault with.
194 */
195 if (user_mode(regs))
196 __do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
197 else
198 __do_kernel_fault(mm, addr, fsr, regs);
199}
200
201#ifdef CONFIG_MMU
202#define VM_FAULT_BADMAP 0x010000
203#define VM_FAULT_BADACCESS 0x020000
204
205/*
206 * Check that the permissions on the VMA allow for the fault which occurred.
207 * If we encountered a write fault, we must have write permission, otherwise
208 * we allow any permission.
209 */
210static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
211{
212 unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
213
214 if (fsr & FSR_WRITE)
215 mask = VM_WRITE;
216 if (fsr & FSR_LNX_PF)
217 mask = VM_EXEC;
218
219 return vma->vm_flags & mask ? false : true;
220}
221
222static int __kprobes
223__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
224 unsigned int flags, struct task_struct *tsk)
225{
226 struct vm_area_struct *vma;
227 int fault;
228
229 vma = find_vma(mm, addr);
230 fault = VM_FAULT_BADMAP;
231 if (unlikely(!vma))
232 goto out;
233 if (unlikely(vma->vm_start > addr))
234 goto check_stack;
235
236 /*
237 * Ok, we have a good vm_area for this
238 * memory access, so we can handle it.
239 */
240good_area:
241 if (access_error(fsr, vma)) {
242 fault = VM_FAULT_BADACCESS;
243 goto out;
244 }
245
246 return handle_mm_fault(vma, addr & PAGE_MASK, flags);
247
248check_stack:
249 /* Don't allow expansion below FIRST_USER_ADDRESS */
250 if (vma->vm_flags & VM_GROWSDOWN &&
251 addr >= FIRST_USER_ADDRESS && !expand_stack(vma, addr))
252 goto good_area;
253out:
254 return fault;
255}
256
257static int __kprobes
258do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
259{
260 struct task_struct *tsk;
261 struct mm_struct *mm;
262 int fault, sig, code;
263 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
264
265 if (notify_page_fault(regs, fsr))
266 return 0;
267
268 tsk = current;
269 mm = tsk->mm;
270
271 /* Enable interrupts if they were enabled in the parent context. */
272 if (interrupts_enabled(regs))
273 local_irq_enable();
274
275 /*
276 * If we're in an interrupt or have no user
277 * context, we must not take the fault..
278 */
279 if (faulthandler_disabled() || !mm)
280 goto no_context;
281
282 if (user_mode(regs))
283 flags |= FAULT_FLAG_USER;
284 if (fsr & FSR_WRITE)
285 flags |= FAULT_FLAG_WRITE;
286
287 /*
288 * As per x86, we may deadlock here. However, since the kernel only
289 * validly references user space from well defined areas of the code,
290 * we can bug out early if this is from code which shouldn't.
291 */
292 if (!down_read_trylock(&mm->mmap_sem)) {
293 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
294 goto no_context;
295retry:
296 down_read(&mm->mmap_sem);
297 } else {
298 /*
299 * The above down_read_trylock() might have succeeded in
300 * which case, we'll have missed the might_sleep() from
301 * down_read()
302 */
303 might_sleep();
304#ifdef CONFIG_DEBUG_VM
305 if (!user_mode(regs) &&
306 !search_exception_tables(regs->ARM_pc))
307 goto no_context;
308#endif
309 }
310
311 fault = __do_page_fault(mm, addr, fsr, flags, tsk);
312
313 /* If we need to retry but a fatal signal is pending, handle the
314 * signal first. We do not need to release the mmap_sem because
315 * it would already be released in __lock_page_or_retry in
316 * mm/filemap.c. */
317 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
318 if (!user_mode(regs))
319 goto no_context;
320 return 0;
321 }
322
323 /*
324 * Major/minor page fault accounting is only done on the
325 * initial attempt. If we go through a retry, it is extremely
326 * likely that the page will be found in page cache at that point.
327 */
328
329 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
330 if (!(fault & VM_FAULT_ERROR) && flags & FAULT_FLAG_ALLOW_RETRY) {
331 if (fault & VM_FAULT_MAJOR) {
332 tsk->maj_flt++;
333 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
334 regs, addr);
335 } else {
336 tsk->min_flt++;
337 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
338 regs, addr);
339 }
340 if (fault & VM_FAULT_RETRY) {
341 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
342 * of starvation. */
343 flags &= ~FAULT_FLAG_ALLOW_RETRY;
344 flags |= FAULT_FLAG_TRIED;
345 goto retry;
346 }
347 }
348
349 up_read(&mm->mmap_sem);
350
351 /*
352 * Handle the "normal" case first - VM_FAULT_MAJOR
353 */
354 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
355 return 0;
356
357 /*
358 * If we are in kernel mode at this point, we
359 * have no context to handle this fault with.
360 */
361 if (!user_mode(regs))
362 goto no_context;
363
364 if (fault & VM_FAULT_OOM) {
365 /*
366 * We ran out of memory, call the OOM killer, and return to
367 * userspace (which will retry the fault, or kill us if we
368 * got oom-killed)
369 */
370 pagefault_out_of_memory();
371 return 0;
372 }
373
374 if (fault & VM_FAULT_SIGBUS) {
375 /*
376 * We had some memory, but were unable to
377 * successfully fix up this page fault.
378 */
379 sig = SIGBUS;
380 code = BUS_ADRERR;
381 } else {
382 /*
383 * Something tried to access memory that
384 * isn't in our memory map..
385 */
386 sig = SIGSEGV;
387 code = fault == VM_FAULT_BADACCESS ?
388 SEGV_ACCERR : SEGV_MAPERR;
389 }
390
391 __do_user_fault(tsk, addr, fsr, sig, code, regs);
392 return 0;
393
394no_context:
395 __do_kernel_fault(mm, addr, fsr, regs);
396 return 0;
397}
398#else /* CONFIG_MMU */
399static int
400do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
401{
402 return 0;
403}
404#endif /* CONFIG_MMU */
405
406/*
407 * First Level Translation Fault Handler
408 *
409 * We enter here because the first level page table doesn't contain
410 * a valid entry for the address.
411 *
412 * If the address is in kernel space (>= TASK_SIZE), then we are
413 * probably faulting in the vmalloc() area.
414 *
415 * If the init_task's first level page tables contains the relevant
416 * entry, we copy the it to this task. If not, we send the process
417 * a signal, fixup the exception, or oops the kernel.
418 *
419 * NOTE! We MUST NOT take any locks for this case. We may be in an
420 * interrupt or a critical region, and should only copy the information
421 * from the master page table, nothing more.
422 */
423#ifdef CONFIG_MMU
424static int __kprobes
425do_translation_fault(unsigned long addr, unsigned int fsr,
426 struct pt_regs *regs)
427{
428 unsigned int index;
429 pgd_t *pgd, *pgd_k;
430 pud_t *pud, *pud_k;
431 pmd_t *pmd, *pmd_k;
432
433 if (addr < TASK_SIZE)
434 return do_page_fault(addr, fsr, regs);
435
436 if (user_mode(regs))
437 goto bad_area;
438
439 index = pgd_index(addr);
440
441 pgd = cpu_get_pgd() + index;
442 pgd_k = init_mm.pgd + index;
443
444 if (pgd_none(*pgd_k))
445 goto bad_area;
446 if (!pgd_present(*pgd))
447 set_pgd(pgd, *pgd_k);
448
449 pud = pud_offset(pgd, addr);
450 pud_k = pud_offset(pgd_k, addr);
451
452 if (pud_none(*pud_k))
453 goto bad_area;
454 if (!pud_present(*pud))
455 set_pud(pud, *pud_k);
456
457 pmd = pmd_offset(pud, addr);
458 pmd_k = pmd_offset(pud_k, addr);
459
460#ifdef CONFIG_ARM_LPAE
461 /*
462 * Only one hardware entry per PMD with LPAE.
463 */
464 index = 0;
465#else
466 /*
467 * On ARM one Linux PGD entry contains two hardware entries (see page
468 * tables layout in pgtable.h). We normally guarantee that we always
469 * fill both L1 entries. But create_mapping() doesn't follow the rule.
470 * It can create inidividual L1 entries, so here we have to call
471 * pmd_none() check for the entry really corresponded to address, not
472 * for the first of pair.
473 */
474 index = (addr >> SECTION_SHIFT) & 1;
475#endif
476 if (pmd_none(pmd_k[index]))
477 goto bad_area;
478
479 copy_pmd(pmd, pmd_k);
480 return 0;
481
482bad_area:
483 do_bad_area(addr, fsr, regs);
484 return 0;
485}
486#else /* CONFIG_MMU */
487static int
488do_translation_fault(unsigned long addr, unsigned int fsr,
489 struct pt_regs *regs)
490{
491 return 0;
492}
493#endif /* CONFIG_MMU */
494
495/*
496 * Some section permission faults need to be handled gracefully.
497 * They can happen due to a __{get,put}_user during an oops.
498 */
499#ifndef CONFIG_ARM_LPAE
500static int
501do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
502{
503 do_bad_area(addr, fsr, regs);
504 return 0;
505}
506#endif /* CONFIG_ARM_LPAE */
507
508/*
509 * This abort handler always returns "fault".
510 */
511static int
512do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
513{
514 return 1;
515}
516
517struct fsr_info {
518 int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
519 int sig;
520 int code;
521 const char *name;
522};
523
524/* FSR definition */
525#ifdef CONFIG_ARM_LPAE
526#include "fsr-3level.c"
527#else
528#include "fsr-2level.c"
529#endif
530
531void __init
532hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
533 int sig, int code, const char *name)
534{
535 if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
536 BUG();
537
538 fsr_info[nr].fn = fn;
539 fsr_info[nr].sig = sig;
540 fsr_info[nr].code = code;
541 fsr_info[nr].name = name;
542}
543
544/*
545 * Dispatch a data abort to the relevant handler.
546 */
547asmlinkage void
548do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
549{
550 const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
551 struct siginfo info;
552
553 if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
554 return;
555
556 pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
557 inf->name, fsr, addr);
558 show_pte(current->mm, addr);
559
560 info.si_signo = inf->sig;
561 info.si_errno = 0;
562 info.si_code = inf->code;
563 info.si_addr = (void __user *)addr;
564 arm_notify_die("", regs, &info, fsr, 0);
565}
566
567void __init
568hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
569 int sig, int code, const char *name)
570{
571 if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
572 BUG();
573
574 ifsr_info[nr].fn = fn;
575 ifsr_info[nr].sig = sig;
576 ifsr_info[nr].code = code;
577 ifsr_info[nr].name = name;
578}
579
580asmlinkage void
581do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
582{
583 const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
584 struct siginfo info;
585
586 if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
587 return;
588
589 pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
590 inf->name, ifsr, addr);
591
592 info.si_signo = inf->sig;
593 info.si_errno = 0;
594 info.si_code = inf->code;
595 info.si_addr = (void __user *)addr;
596 arm_notify_die("", regs, &info, ifsr, 0);
597}
598
599/*
600 * Abort handler to be used only during first unmasking of asynchronous aborts
601 * on the boot CPU. This makes sure that the machine will not die if the
602 * firmware/bootloader left an imprecise abort pending for us to trip over.
603 */
604static int __init early_abort_handler(unsigned long addr, unsigned int fsr,
605 struct pt_regs *regs)
606{
607 pr_warn("Hit pending asynchronous external abort (FSR=0x%08x) during "
608 "first unmask, this is most likely caused by a "
609 "firmware/bootloader bug.\n", fsr);
610
611 return 0;
612}
613
614void __init early_abt_enable(void)
615{
616 fsr_info[FSR_FS_AEA].fn = early_abort_handler;
617 local_abt_enable();
618 fsr_info[FSR_FS_AEA].fn = do_bad;
619}
620
621#ifndef CONFIG_ARM_LPAE
622static int __init exceptions_init(void)
623{
624 if (cpu_architecture() >= CPU_ARCH_ARMv6) {
625 hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
626 "I-cache maintenance fault");
627 }
628
629 if (cpu_architecture() >= CPU_ARCH_ARMv7) {
630 /*
631 * TODO: Access flag faults introduced in ARMv6K.
632 * Runtime check for 'K' extension is needed
633 */
634 hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
635 "section access flag fault");
636 hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
637 "section access flag fault");
638 }
639
640 return 0;
641}
642
643arch_initcall(exceptions_init);
644#endif