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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
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