Loading...
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/module.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.h>
20#include <linux/highmem.h>
21#include <linux/perf_event.h>
22
23#include <asm/system.h>
24#include <asm/pgtable.h>
25#include <asm/tlbflush.h>
26
27#include "fault.h"
28
29/*
30 * Fault status register encodings. We steal bit 31 for our own purposes.
31 */
32#define FSR_LNX_PF (1 << 31)
33#define FSR_WRITE (1 << 11)
34#define FSR_FS4 (1 << 10)
35#define FSR_FS3_0 (15)
36
37static inline int fsr_fs(unsigned int fsr)
38{
39 return (fsr & FSR_FS3_0) | (fsr & FSR_FS4) >> 6;
40}
41
42#ifdef CONFIG_MMU
43
44#ifdef CONFIG_KPROBES
45static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
46{
47 int ret = 0;
48
49 if (!user_mode(regs)) {
50 /* kprobe_running() needs smp_processor_id() */
51 preempt_disable();
52 if (kprobe_running() && kprobe_fault_handler(regs, fsr))
53 ret = 1;
54 preempt_enable();
55 }
56
57 return ret;
58}
59#else
60static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
61{
62 return 0;
63}
64#endif
65
66/*
67 * This is useful to dump out the page tables associated with
68 * 'addr' in mm 'mm'.
69 */
70void show_pte(struct mm_struct *mm, unsigned long addr)
71{
72 pgd_t *pgd;
73
74 if (!mm)
75 mm = &init_mm;
76
77 printk(KERN_ALERT "pgd = %p\n", mm->pgd);
78 pgd = pgd_offset(mm, addr);
79 printk(KERN_ALERT "[%08lx] *pgd=%08llx",
80 addr, (long long)pgd_val(*pgd));
81
82 do {
83 pud_t *pud;
84 pmd_t *pmd;
85 pte_t *pte;
86
87 if (pgd_none(*pgd))
88 break;
89
90 if (pgd_bad(*pgd)) {
91 printk("(bad)");
92 break;
93 }
94
95 pud = pud_offset(pgd, addr);
96 if (PTRS_PER_PUD != 1)
97 printk(", *pud=%08llx", (long long)pud_val(*pud));
98
99 if (pud_none(*pud))
100 break;
101
102 if (pud_bad(*pud)) {
103 printk("(bad)");
104 break;
105 }
106
107 pmd = pmd_offset(pud, addr);
108 if (PTRS_PER_PMD != 1)
109 printk(", *pmd=%08llx", (long long)pmd_val(*pmd));
110
111 if (pmd_none(*pmd))
112 break;
113
114 if (pmd_bad(*pmd)) {
115 printk("(bad)");
116 break;
117 }
118
119 /* We must not map this if we have highmem enabled */
120 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
121 break;
122
123 pte = pte_offset_map(pmd, addr);
124 printk(", *pte=%08llx", (long long)pte_val(*pte));
125 printk(", *ppte=%08llx",
126 (long long)pte_val(pte[PTE_HWTABLE_PTRS]));
127 pte_unmap(pte);
128 } while(0);
129
130 printk("\n");
131}
132#else /* CONFIG_MMU */
133void show_pte(struct mm_struct *mm, unsigned long addr)
134{ }
135#endif /* CONFIG_MMU */
136
137/*
138 * Oops. The kernel tried to access some page that wasn't present.
139 */
140static void
141__do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
142 struct pt_regs *regs)
143{
144 /*
145 * Are we prepared to handle this kernel fault?
146 */
147 if (fixup_exception(regs))
148 return;
149
150 /*
151 * No handler, we'll have to terminate things with extreme prejudice.
152 */
153 bust_spinlocks(1);
154 printk(KERN_ALERT
155 "Unable to handle kernel %s at virtual address %08lx\n",
156 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
157 "paging request", addr);
158
159 show_pte(mm, addr);
160 die("Oops", regs, fsr);
161 bust_spinlocks(0);
162 do_exit(SIGKILL);
163}
164
165/*
166 * Something tried to access memory that isn't in our memory map..
167 * User mode accesses just cause a SIGSEGV
168 */
169static void
170__do_user_fault(struct task_struct *tsk, unsigned long addr,
171 unsigned int fsr, unsigned int sig, int code,
172 struct pt_regs *regs)
173{
174 struct siginfo si;
175
176#ifdef CONFIG_DEBUG_USER
177 if (user_debug & UDBG_SEGV) {
178 printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
179 tsk->comm, sig, addr, fsr);
180 show_pte(tsk->mm, addr);
181 show_regs(regs);
182 }
183#endif
184
185 tsk->thread.address = addr;
186 tsk->thread.error_code = fsr;
187 tsk->thread.trap_no = 14;
188 si.si_signo = sig;
189 si.si_errno = 0;
190 si.si_code = code;
191 si.si_addr = (void __user *)addr;
192 force_sig_info(sig, &si, tsk);
193}
194
195void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
196{
197 struct task_struct *tsk = current;
198 struct mm_struct *mm = tsk->active_mm;
199
200 /*
201 * If we are in kernel mode at this point, we
202 * have no context to handle this fault with.
203 */
204 if (user_mode(regs))
205 __do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
206 else
207 __do_kernel_fault(mm, addr, fsr, regs);
208}
209
210#ifdef CONFIG_MMU
211#define VM_FAULT_BADMAP 0x010000
212#define VM_FAULT_BADACCESS 0x020000
213
214/*
215 * Check that the permissions on the VMA allow for the fault which occurred.
216 * If we encountered a write fault, we must have write permission, otherwise
217 * we allow any permission.
218 */
219static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
220{
221 unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
222
223 if (fsr & FSR_WRITE)
224 mask = VM_WRITE;
225 if (fsr & FSR_LNX_PF)
226 mask = VM_EXEC;
227
228 return vma->vm_flags & mask ? false : true;
229}
230
231static int __kprobes
232__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
233 struct task_struct *tsk)
234{
235 struct vm_area_struct *vma;
236 int fault;
237
238 vma = find_vma(mm, addr);
239 fault = VM_FAULT_BADMAP;
240 if (unlikely(!vma))
241 goto out;
242 if (unlikely(vma->vm_start > addr))
243 goto check_stack;
244
245 /*
246 * Ok, we have a good vm_area for this
247 * memory access, so we can handle it.
248 */
249good_area:
250 if (access_error(fsr, vma)) {
251 fault = VM_FAULT_BADACCESS;
252 goto out;
253 }
254
255 /*
256 * If for any reason at all we couldn't handle the fault, make
257 * sure we exit gracefully rather than endlessly redo the fault.
258 */
259 fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, (fsr & FSR_WRITE) ? FAULT_FLAG_WRITE : 0);
260 if (unlikely(fault & VM_FAULT_ERROR))
261 return fault;
262 if (fault & VM_FAULT_MAJOR)
263 tsk->maj_flt++;
264 else
265 tsk->min_flt++;
266 return fault;
267
268check_stack:
269 if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
270 goto good_area;
271out:
272 return fault;
273}
274
275static int __kprobes
276do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
277{
278 struct task_struct *tsk;
279 struct mm_struct *mm;
280 int fault, sig, code;
281
282 if (notify_page_fault(regs, fsr))
283 return 0;
284
285 tsk = current;
286 mm = tsk->mm;
287
288 /* Enable interrupts if they were enabled in the parent context. */
289 if (interrupts_enabled(regs))
290 local_irq_enable();
291
292 /*
293 * If we're in an interrupt or have no user
294 * context, we must not take the fault..
295 */
296 if (in_atomic() || !mm)
297 goto no_context;
298
299 /*
300 * As per x86, we may deadlock here. However, since the kernel only
301 * validly references user space from well defined areas of the code,
302 * we can bug out early if this is from code which shouldn't.
303 */
304 if (!down_read_trylock(&mm->mmap_sem)) {
305 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
306 goto no_context;
307 down_read(&mm->mmap_sem);
308 } else {
309 /*
310 * The above down_read_trylock() might have succeeded in
311 * which case, we'll have missed the might_sleep() from
312 * down_read()
313 */
314 might_sleep();
315#ifdef CONFIG_DEBUG_VM
316 if (!user_mode(regs) &&
317 !search_exception_tables(regs->ARM_pc))
318 goto no_context;
319#endif
320 }
321
322 fault = __do_page_fault(mm, addr, fsr, tsk);
323 up_read(&mm->mmap_sem);
324
325 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
326 if (fault & VM_FAULT_MAJOR)
327 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, addr);
328 else if (fault & VM_FAULT_MINOR)
329 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, addr);
330
331 /*
332 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
333 */
334 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
335 return 0;
336
337 if (fault & VM_FAULT_OOM) {
338 /*
339 * We ran out of memory, call the OOM killer, and return to
340 * userspace (which will retry the fault, or kill us if we
341 * got oom-killed)
342 */
343 pagefault_out_of_memory();
344 return 0;
345 }
346
347 /*
348 * If we are in kernel mode at this point, we
349 * have no context to handle this fault with.
350 */
351 if (!user_mode(regs))
352 goto no_context;
353
354 if (fault & VM_FAULT_SIGBUS) {
355 /*
356 * We had some memory, but were unable to
357 * successfully fix up this page fault.
358 */
359 sig = SIGBUS;
360 code = BUS_ADRERR;
361 } else {
362 /*
363 * Something tried to access memory that
364 * isn't in our memory map..
365 */
366 sig = SIGSEGV;
367 code = fault == VM_FAULT_BADACCESS ?
368 SEGV_ACCERR : SEGV_MAPERR;
369 }
370
371 __do_user_fault(tsk, addr, fsr, sig, code, regs);
372 return 0;
373
374no_context:
375 __do_kernel_fault(mm, addr, fsr, regs);
376 return 0;
377}
378#else /* CONFIG_MMU */
379static int
380do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
381{
382 return 0;
383}
384#endif /* CONFIG_MMU */
385
386/*
387 * First Level Translation Fault Handler
388 *
389 * We enter here because the first level page table doesn't contain
390 * a valid entry for the address.
391 *
392 * If the address is in kernel space (>= TASK_SIZE), then we are
393 * probably faulting in the vmalloc() area.
394 *
395 * If the init_task's first level page tables contains the relevant
396 * entry, we copy the it to this task. If not, we send the process
397 * a signal, fixup the exception, or oops the kernel.
398 *
399 * NOTE! We MUST NOT take any locks for this case. We may be in an
400 * interrupt or a critical region, and should only copy the information
401 * from the master page table, nothing more.
402 */
403#ifdef CONFIG_MMU
404static int __kprobes
405do_translation_fault(unsigned long addr, unsigned int fsr,
406 struct pt_regs *regs)
407{
408 unsigned int index;
409 pgd_t *pgd, *pgd_k;
410 pud_t *pud, *pud_k;
411 pmd_t *pmd, *pmd_k;
412
413 if (addr < TASK_SIZE)
414 return do_page_fault(addr, fsr, regs);
415
416 if (user_mode(regs))
417 goto bad_area;
418
419 index = pgd_index(addr);
420
421 /*
422 * FIXME: CP15 C1 is write only on ARMv3 architectures.
423 */
424 pgd = cpu_get_pgd() + index;
425 pgd_k = init_mm.pgd + index;
426
427 if (pgd_none(*pgd_k))
428 goto bad_area;
429 if (!pgd_present(*pgd))
430 set_pgd(pgd, *pgd_k);
431
432 pud = pud_offset(pgd, addr);
433 pud_k = pud_offset(pgd_k, addr);
434
435 if (pud_none(*pud_k))
436 goto bad_area;
437 if (!pud_present(*pud))
438 set_pud(pud, *pud_k);
439
440 pmd = pmd_offset(pud, addr);
441 pmd_k = pmd_offset(pud_k, addr);
442
443 /*
444 * On ARM one Linux PGD entry contains two hardware entries (see page
445 * tables layout in pgtable.h). We normally guarantee that we always
446 * fill both L1 entries. But create_mapping() doesn't follow the rule.
447 * It can create inidividual L1 entries, so here we have to call
448 * pmd_none() check for the entry really corresponded to address, not
449 * for the first of pair.
450 */
451 index = (addr >> SECTION_SHIFT) & 1;
452 if (pmd_none(pmd_k[index]))
453 goto bad_area;
454
455 copy_pmd(pmd, pmd_k);
456 return 0;
457
458bad_area:
459 do_bad_area(addr, fsr, regs);
460 return 0;
461}
462#else /* CONFIG_MMU */
463static int
464do_translation_fault(unsigned long addr, unsigned int fsr,
465 struct pt_regs *regs)
466{
467 return 0;
468}
469#endif /* CONFIG_MMU */
470
471/*
472 * Some section permission faults need to be handled gracefully.
473 * They can happen due to a __{get,put}_user during an oops.
474 */
475static int
476do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
477{
478 do_bad_area(addr, fsr, regs);
479 return 0;
480}
481
482/*
483 * This abort handler always returns "fault".
484 */
485static int
486do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
487{
488 return 1;
489}
490
491static struct fsr_info {
492 int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
493 int sig;
494 int code;
495 const char *name;
496} fsr_info[] = {
497 /*
498 * The following are the standard ARMv3 and ARMv4 aborts. ARMv5
499 * defines these to be "precise" aborts.
500 */
501 { do_bad, SIGSEGV, 0, "vector exception" },
502 { do_bad, SIGBUS, BUS_ADRALN, "alignment exception" },
503 { do_bad, SIGKILL, 0, "terminal exception" },
504 { do_bad, SIGBUS, BUS_ADRALN, "alignment exception" },
505 { do_bad, SIGBUS, 0, "external abort on linefetch" },
506 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault" },
507 { do_bad, SIGBUS, 0, "external abort on linefetch" },
508 { do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault" },
509 { do_bad, SIGBUS, 0, "external abort on non-linefetch" },
510 { do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault" },
511 { do_bad, SIGBUS, 0, "external abort on non-linefetch" },
512 { do_bad, SIGSEGV, SEGV_ACCERR, "page domain fault" },
513 { do_bad, SIGBUS, 0, "external abort on translation" },
514 { do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault" },
515 { do_bad, SIGBUS, 0, "external abort on translation" },
516 { do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault" },
517 /*
518 * The following are "imprecise" aborts, which are signalled by bit
519 * 10 of the FSR, and may not be recoverable. These are only
520 * supported if the CPU abort handler supports bit 10.
521 */
522 { do_bad, SIGBUS, 0, "unknown 16" },
523 { do_bad, SIGBUS, 0, "unknown 17" },
524 { do_bad, SIGBUS, 0, "unknown 18" },
525 { do_bad, SIGBUS, 0, "unknown 19" },
526 { do_bad, SIGBUS, 0, "lock abort" }, /* xscale */
527 { do_bad, SIGBUS, 0, "unknown 21" },
528 { do_bad, SIGBUS, BUS_OBJERR, "imprecise external abort" }, /* xscale */
529 { do_bad, SIGBUS, 0, "unknown 23" },
530 { do_bad, SIGBUS, 0, "dcache parity error" }, /* xscale */
531 { do_bad, SIGBUS, 0, "unknown 25" },
532 { do_bad, SIGBUS, 0, "unknown 26" },
533 { do_bad, SIGBUS, 0, "unknown 27" },
534 { do_bad, SIGBUS, 0, "unknown 28" },
535 { do_bad, SIGBUS, 0, "unknown 29" },
536 { do_bad, SIGBUS, 0, "unknown 30" },
537 { do_bad, SIGBUS, 0, "unknown 31" }
538};
539
540void __init
541hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
542 int sig, int code, const char *name)
543{
544 if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
545 BUG();
546
547 fsr_info[nr].fn = fn;
548 fsr_info[nr].sig = sig;
549 fsr_info[nr].code = code;
550 fsr_info[nr].name = name;
551}
552
553/*
554 * Dispatch a data abort to the relevant handler.
555 */
556asmlinkage void __exception
557do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
558{
559 const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
560 struct siginfo info;
561
562 if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
563 return;
564
565 printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
566 inf->name, fsr, addr);
567
568 info.si_signo = inf->sig;
569 info.si_errno = 0;
570 info.si_code = inf->code;
571 info.si_addr = (void __user *)addr;
572 arm_notify_die("", regs, &info, fsr, 0);
573}
574
575
576static struct fsr_info ifsr_info[] = {
577 { do_bad, SIGBUS, 0, "unknown 0" },
578 { do_bad, SIGBUS, 0, "unknown 1" },
579 { do_bad, SIGBUS, 0, "debug event" },
580 { do_bad, SIGSEGV, SEGV_ACCERR, "section access flag fault" },
581 { do_bad, SIGBUS, 0, "unknown 4" },
582 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault" },
583 { do_bad, SIGSEGV, SEGV_ACCERR, "page access flag fault" },
584 { do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault" },
585 { do_bad, SIGBUS, 0, "external abort on non-linefetch" },
586 { do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault" },
587 { do_bad, SIGBUS, 0, "unknown 10" },
588 { do_bad, SIGSEGV, SEGV_ACCERR, "page domain fault" },
589 { do_bad, SIGBUS, 0, "external abort on translation" },
590 { do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault" },
591 { do_bad, SIGBUS, 0, "external abort on translation" },
592 { do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault" },
593 { do_bad, SIGBUS, 0, "unknown 16" },
594 { do_bad, SIGBUS, 0, "unknown 17" },
595 { do_bad, SIGBUS, 0, "unknown 18" },
596 { do_bad, SIGBUS, 0, "unknown 19" },
597 { do_bad, SIGBUS, 0, "unknown 20" },
598 { do_bad, SIGBUS, 0, "unknown 21" },
599 { do_bad, SIGBUS, 0, "unknown 22" },
600 { do_bad, SIGBUS, 0, "unknown 23" },
601 { do_bad, SIGBUS, 0, "unknown 24" },
602 { do_bad, SIGBUS, 0, "unknown 25" },
603 { do_bad, SIGBUS, 0, "unknown 26" },
604 { do_bad, SIGBUS, 0, "unknown 27" },
605 { do_bad, SIGBUS, 0, "unknown 28" },
606 { do_bad, SIGBUS, 0, "unknown 29" },
607 { do_bad, SIGBUS, 0, "unknown 30" },
608 { do_bad, SIGBUS, 0, "unknown 31" },
609};
610
611void __init
612hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
613 int sig, int code, const char *name)
614{
615 if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
616 BUG();
617
618 ifsr_info[nr].fn = fn;
619 ifsr_info[nr].sig = sig;
620 ifsr_info[nr].code = code;
621 ifsr_info[nr].name = name;
622}
623
624asmlinkage void __exception
625do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
626{
627 const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
628 struct siginfo info;
629
630 if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
631 return;
632
633 printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
634 inf->name, ifsr, addr);
635
636 info.si_signo = inf->sig;
637 info.si_errno = 0;
638 info.si_code = inf->code;
639 info.si_addr = (void __user *)addr;
640 arm_notify_die("", regs, &info, ifsr, 0);
641}
642
643static int __init exceptions_init(void)
644{
645 if (cpu_architecture() >= CPU_ARCH_ARMv6) {
646 hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
647 "I-cache maintenance fault");
648 }
649
650 if (cpu_architecture() >= CPU_ARCH_ARMv7) {
651 /*
652 * TODO: Access flag faults introduced in ARMv6K.
653 * Runtime check for 'K' extension is needed
654 */
655 hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
656 "section access flag fault");
657 hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
658 "section access flag fault");
659 }
660
661 return 0;
662}
663
664arch_initcall(exceptions_init);
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/module.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.h>
20#include <linux/highmem.h>
21#include <linux/perf_event.h>
22
23#include <asm/exception.h>
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(mm, 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 return 0;
319
320 /*
321 * Major/minor page fault accounting is only done on the
322 * initial attempt. If we go through a retry, it is extremely
323 * likely that the page will be found in page cache at that point.
324 */
325
326 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
327 if (!(fault & VM_FAULT_ERROR) && flags & FAULT_FLAG_ALLOW_RETRY) {
328 if (fault & VM_FAULT_MAJOR) {
329 tsk->maj_flt++;
330 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
331 regs, addr);
332 } else {
333 tsk->min_flt++;
334 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
335 regs, addr);
336 }
337 if (fault & VM_FAULT_RETRY) {
338 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
339 * of starvation. */
340 flags &= ~FAULT_FLAG_ALLOW_RETRY;
341 flags |= FAULT_FLAG_TRIED;
342 goto retry;
343 }
344 }
345
346 up_read(&mm->mmap_sem);
347
348 /*
349 * Handle the "normal" case first - VM_FAULT_MAJOR
350 */
351 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
352 return 0;
353
354 /*
355 * If we are in kernel mode at this point, we
356 * have no context to handle this fault with.
357 */
358 if (!user_mode(regs))
359 goto no_context;
360
361 if (fault & VM_FAULT_OOM) {
362 /*
363 * We ran out of memory, call the OOM killer, and return to
364 * userspace (which will retry the fault, or kill us if we
365 * got oom-killed)
366 */
367 pagefault_out_of_memory();
368 return 0;
369 }
370
371 if (fault & VM_FAULT_SIGBUS) {
372 /*
373 * We had some memory, but were unable to
374 * successfully fix up this page fault.
375 */
376 sig = SIGBUS;
377 code = BUS_ADRERR;
378 } else {
379 /*
380 * Something tried to access memory that
381 * isn't in our memory map..
382 */
383 sig = SIGSEGV;
384 code = fault == VM_FAULT_BADACCESS ?
385 SEGV_ACCERR : SEGV_MAPERR;
386 }
387
388 __do_user_fault(tsk, addr, fsr, sig, code, regs);
389 return 0;
390
391no_context:
392 __do_kernel_fault(mm, addr, fsr, regs);
393 return 0;
394}
395#else /* CONFIG_MMU */
396static int
397do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
398{
399 return 0;
400}
401#endif /* CONFIG_MMU */
402
403/*
404 * First Level Translation Fault Handler
405 *
406 * We enter here because the first level page table doesn't contain
407 * a valid entry for the address.
408 *
409 * If the address is in kernel space (>= TASK_SIZE), then we are
410 * probably faulting in the vmalloc() area.
411 *
412 * If the init_task's first level page tables contains the relevant
413 * entry, we copy the it to this task. If not, we send the process
414 * a signal, fixup the exception, or oops the kernel.
415 *
416 * NOTE! We MUST NOT take any locks for this case. We may be in an
417 * interrupt or a critical region, and should only copy the information
418 * from the master page table, nothing more.
419 */
420#ifdef CONFIG_MMU
421static int __kprobes
422do_translation_fault(unsigned long addr, unsigned int fsr,
423 struct pt_regs *regs)
424{
425 unsigned int index;
426 pgd_t *pgd, *pgd_k;
427 pud_t *pud, *pud_k;
428 pmd_t *pmd, *pmd_k;
429
430 if (addr < TASK_SIZE)
431 return do_page_fault(addr, fsr, regs);
432
433 if (user_mode(regs))
434 goto bad_area;
435
436 index = pgd_index(addr);
437
438 pgd = cpu_get_pgd() + index;
439 pgd_k = init_mm.pgd + index;
440
441 if (pgd_none(*pgd_k))
442 goto bad_area;
443 if (!pgd_present(*pgd))
444 set_pgd(pgd, *pgd_k);
445
446 pud = pud_offset(pgd, addr);
447 pud_k = pud_offset(pgd_k, addr);
448
449 if (pud_none(*pud_k))
450 goto bad_area;
451 if (!pud_present(*pud))
452 set_pud(pud, *pud_k);
453
454 pmd = pmd_offset(pud, addr);
455 pmd_k = pmd_offset(pud_k, addr);
456
457#ifdef CONFIG_ARM_LPAE
458 /*
459 * Only one hardware entry per PMD with LPAE.
460 */
461 index = 0;
462#else
463 /*
464 * On ARM one Linux PGD entry contains two hardware entries (see page
465 * tables layout in pgtable.h). We normally guarantee that we always
466 * fill both L1 entries. But create_mapping() doesn't follow the rule.
467 * It can create inidividual L1 entries, so here we have to call
468 * pmd_none() check for the entry really corresponded to address, not
469 * for the first of pair.
470 */
471 index = (addr >> SECTION_SHIFT) & 1;
472#endif
473 if (pmd_none(pmd_k[index]))
474 goto bad_area;
475
476 copy_pmd(pmd, pmd_k);
477 return 0;
478
479bad_area:
480 do_bad_area(addr, fsr, regs);
481 return 0;
482}
483#else /* CONFIG_MMU */
484static int
485do_translation_fault(unsigned long addr, unsigned int fsr,
486 struct pt_regs *regs)
487{
488 return 0;
489}
490#endif /* CONFIG_MMU */
491
492/*
493 * Some section permission faults need to be handled gracefully.
494 * They can happen due to a __{get,put}_user during an oops.
495 */
496#ifndef CONFIG_ARM_LPAE
497static int
498do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
499{
500 do_bad_area(addr, fsr, regs);
501 return 0;
502}
503#endif /* CONFIG_ARM_LPAE */
504
505/*
506 * This abort handler always returns "fault".
507 */
508static int
509do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
510{
511 return 1;
512}
513
514struct fsr_info {
515 int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
516 int sig;
517 int code;
518 const char *name;
519};
520
521/* FSR definition */
522#ifdef CONFIG_ARM_LPAE
523#include "fsr-3level.c"
524#else
525#include "fsr-2level.c"
526#endif
527
528void __init
529hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
530 int sig, int code, const char *name)
531{
532 if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
533 BUG();
534
535 fsr_info[nr].fn = fn;
536 fsr_info[nr].sig = sig;
537 fsr_info[nr].code = code;
538 fsr_info[nr].name = name;
539}
540
541/*
542 * Dispatch a data abort to the relevant handler.
543 */
544asmlinkage void __exception
545do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
546{
547 const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
548 struct siginfo info;
549
550 if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
551 return;
552
553 pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
554 inf->name, fsr, addr);
555 show_pte(current->mm, addr);
556
557 info.si_signo = inf->sig;
558 info.si_errno = 0;
559 info.si_code = inf->code;
560 info.si_addr = (void __user *)addr;
561 arm_notify_die("", regs, &info, fsr, 0);
562}
563
564void __init
565hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
566 int sig, int code, const char *name)
567{
568 if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
569 BUG();
570
571 ifsr_info[nr].fn = fn;
572 ifsr_info[nr].sig = sig;
573 ifsr_info[nr].code = code;
574 ifsr_info[nr].name = name;
575}
576
577asmlinkage void __exception
578do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
579{
580 const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
581 struct siginfo info;
582
583 if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
584 return;
585
586 pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
587 inf->name, ifsr, addr);
588
589 info.si_signo = inf->sig;
590 info.si_errno = 0;
591 info.si_code = inf->code;
592 info.si_addr = (void __user *)addr;
593 arm_notify_die("", regs, &info, ifsr, 0);
594}
595
596/*
597 * Abort handler to be used only during first unmasking of asynchronous aborts
598 * on the boot CPU. This makes sure that the machine will not die if the
599 * firmware/bootloader left an imprecise abort pending for us to trip over.
600 */
601static int __init early_abort_handler(unsigned long addr, unsigned int fsr,
602 struct pt_regs *regs)
603{
604 pr_warn("Hit pending asynchronous external abort (FSR=0x%08x) during "
605 "first unmask, this is most likely caused by a "
606 "firmware/bootloader bug.\n", fsr);
607
608 return 0;
609}
610
611void __init early_abt_enable(void)
612{
613 fsr_info[22].fn = early_abort_handler;
614 local_abt_enable();
615 fsr_info[22].fn = do_bad;
616}
617
618#ifndef CONFIG_ARM_LPAE
619static int __init exceptions_init(void)
620{
621 if (cpu_architecture() >= CPU_ARCH_ARMv6) {
622 hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
623 "I-cache maintenance fault");
624 }
625
626 if (cpu_architecture() >= CPU_ARCH_ARMv7) {
627 /*
628 * TODO: Access flag faults introduced in ARMv6K.
629 * Runtime check for 'K' extension is needed
630 */
631 hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
632 "section access flag fault");
633 hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
634 "section access flag fault");
635 }
636
637 return 0;
638}
639
640arch_initcall(exceptions_init);
641#endif