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