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/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#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 if (!pte)
89 break;
90
91 pr_cont(", *pte=%08llx", (long long)pte_val(*pte));
92#ifndef CONFIG_ARM_LPAE
93 pr_cont(", *ppte=%08llx",
94 (long long)pte_val(pte[PTE_HWTABLE_PTRS]));
95#endif
96 pte_unmap(pte);
97 } while(0);
98
99 pr_cont("\n");
100}
101#else /* CONFIG_MMU */
102void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
103{ }
104#endif /* CONFIG_MMU */
105
106static inline bool is_write_fault(unsigned int fsr)
107{
108 return (fsr & FSR_WRITE) && !(fsr & FSR_CM);
109}
110
111static inline bool is_translation_fault(unsigned int fsr)
112{
113 int fs = fsr_fs(fsr);
114#ifdef CONFIG_ARM_LPAE
115 if ((fs & FS_MMU_NOLL_MASK) == FS_TRANS_NOLL)
116 return true;
117#else
118 if (fs == FS_L1_TRANS || fs == FS_L2_TRANS)
119 return true;
120#endif
121 return false;
122}
123
124static void die_kernel_fault(const char *msg, struct mm_struct *mm,
125 unsigned long addr, unsigned int fsr,
126 struct pt_regs *regs)
127{
128 bust_spinlocks(1);
129 pr_alert("8<--- cut here ---\n");
130 pr_alert("Unable to handle kernel %s at virtual address %08lx when %s\n",
131 msg, addr, fsr & FSR_LNX_PF ? "execute" :
132 fsr & FSR_WRITE ? "write" : "read");
133
134 show_pte(KERN_ALERT, mm, addr);
135 die("Oops", regs, fsr);
136 bust_spinlocks(0);
137 make_task_dead(SIGKILL);
138}
139
140/*
141 * Oops. The kernel tried to access some page that wasn't present.
142 */
143static void
144__do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
145 struct pt_regs *regs)
146{
147 const char *msg;
148 /*
149 * Are we prepared to handle this kernel fault?
150 */
151 if (fixup_exception(regs))
152 return;
153
154 /*
155 * No handler, we'll have to terminate things with extreme prejudice.
156 */
157 if (addr < PAGE_SIZE) {
158 msg = "NULL pointer dereference";
159 } else {
160 if (is_translation_fault(fsr) &&
161 kfence_handle_page_fault(addr, is_write_fault(fsr), regs))
162 return;
163
164 msg = "paging request";
165 }
166
167 die_kernel_fault(msg, mm, addr, fsr, regs);
168}
169
170/*
171 * Something tried to access memory that isn't in our memory map..
172 * User mode accesses just cause a SIGSEGV
173 */
174static void
175__do_user_fault(unsigned long addr, unsigned int fsr, unsigned int sig,
176 int code, struct pt_regs *regs)
177{
178 struct task_struct *tsk = current;
179
180 if (addr > TASK_SIZE)
181 harden_branch_predictor();
182
183#ifdef CONFIG_DEBUG_USER
184 if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
185 ((user_debug & UDBG_BUS) && (sig == SIGBUS))) {
186 pr_err("8<--- cut here ---\n");
187 pr_err("%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
188 tsk->comm, sig, addr, fsr);
189 show_pte(KERN_ERR, tsk->mm, addr);
190 show_regs(regs);
191 }
192#endif
193#ifndef CONFIG_KUSER_HELPERS
194 if ((sig == SIGSEGV) && ((addr & PAGE_MASK) == 0xffff0000))
195 printk_ratelimited(KERN_DEBUG
196 "%s: CONFIG_KUSER_HELPERS disabled at 0x%08lx\n",
197 tsk->comm, addr);
198#endif
199
200 tsk->thread.address = addr;
201 tsk->thread.error_code = fsr;
202 tsk->thread.trap_no = 14;
203 force_sig_fault(sig, code, (void __user *)addr);
204}
205
206void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
207{
208 struct task_struct *tsk = current;
209 struct mm_struct *mm = tsk->active_mm;
210
211 /*
212 * If we are in kernel mode at this point, we
213 * have no context to handle this fault with.
214 */
215 if (user_mode(regs))
216 __do_user_fault(addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
217 else
218 __do_kernel_fault(mm, addr, fsr, regs);
219}
220
221#ifdef CONFIG_MMU
222#define VM_FAULT_BADMAP ((__force vm_fault_t)0x010000)
223#define VM_FAULT_BADACCESS ((__force vm_fault_t)0x020000)
224
225static inline bool is_permission_fault(unsigned int fsr)
226{
227 int fs = fsr_fs(fsr);
228#ifdef CONFIG_ARM_LPAE
229 if ((fs & FS_MMU_NOLL_MASK) == FS_PERM_NOLL)
230 return true;
231#else
232 if (fs == FS_L1_PERM || fs == FS_L2_PERM)
233 return true;
234#endif
235 return false;
236}
237
238static int __kprobes
239do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
240{
241 struct mm_struct *mm = current->mm;
242 struct vm_area_struct *vma;
243 int sig, code;
244 vm_fault_t fault;
245 unsigned int flags = FAULT_FLAG_DEFAULT;
246 unsigned long vm_flags = VM_ACCESS_FLAGS;
247
248 if (kprobe_page_fault(regs, fsr))
249 return 0;
250
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
266 if (is_write_fault(fsr)) {
267 flags |= FAULT_FLAG_WRITE;
268 vm_flags = VM_WRITE;
269 }
270
271 if (fsr & FSR_LNX_PF) {
272 vm_flags = VM_EXEC;
273
274 if (is_permission_fault(fsr) && !user_mode(regs))
275 die_kernel_fault("execution of memory",
276 mm, addr, fsr, regs);
277 }
278
279 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
280
281 if (!(flags & FAULT_FLAG_USER))
282 goto lock_mmap;
283
284 vma = lock_vma_under_rcu(mm, addr);
285 if (!vma)
286 goto lock_mmap;
287
288 if (!(vma->vm_flags & vm_flags)) {
289 vma_end_read(vma);
290 goto lock_mmap;
291 }
292 fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
293 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
294 vma_end_read(vma);
295
296 if (!(fault & VM_FAULT_RETRY)) {
297 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
298 goto done;
299 }
300 count_vm_vma_lock_event(VMA_LOCK_RETRY);
301 if (fault & VM_FAULT_MAJOR)
302 flags |= FAULT_FLAG_TRIED;
303
304 /* Quick path to respond to signals */
305 if (fault_signal_pending(fault, regs)) {
306 if (!user_mode(regs))
307 goto no_context;
308 return 0;
309 }
310lock_mmap:
311
312retry:
313 vma = lock_mm_and_find_vma(mm, addr, regs);
314 if (unlikely(!vma)) {
315 fault = VM_FAULT_BADMAP;
316 goto bad_area;
317 }
318
319 /*
320 * ok, we have a good vm_area for this memory access, check the
321 * permissions on the VMA allow for the fault which occurred.
322 */
323 if (!(vma->vm_flags & vm_flags))
324 fault = VM_FAULT_BADACCESS;
325 else
326 fault = handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
327
328 /* If we need to retry but a fatal signal is pending, handle the
329 * signal first. We do not need to release the mmap_lock because
330 * it would already be released in __lock_page_or_retry in
331 * mm/filemap.c. */
332 if (fault_signal_pending(fault, regs)) {
333 if (!user_mode(regs))
334 goto no_context;
335 return 0;
336 }
337
338 /* The fault is fully completed (including releasing mmap lock) */
339 if (fault & VM_FAULT_COMPLETED)
340 return 0;
341
342 if (!(fault & VM_FAULT_ERROR)) {
343 if (fault & VM_FAULT_RETRY) {
344 flags |= FAULT_FLAG_TRIED;
345 goto retry;
346 }
347 }
348
349 mmap_read_unlock(mm);
350done:
351
352 /*
353 * Handle the "normal" case first - VM_FAULT_MAJOR
354 */
355 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
356 return 0;
357
358bad_area:
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