Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/arch/arm/mm/fault.c
4 *
5 * Copyright (C) 1995 Linus Torvalds
6 * Modifications for ARM processor (c) 1995-2004 Russell King
7 */
8#include <linux/extable.h>
9#include <linux/signal.h>
10#include <linux/mm.h>
11#include <linux/hardirq.h>
12#include <linux/init.h>
13#include <linux/kprobes.h>
14#include <linux/uaccess.h>
15#include <linux/page-flags.h>
16#include <linux/sched/signal.h>
17#include <linux/sched/debug.h>
18#include <linux/highmem.h>
19#include <linux/perf_event.h>
20
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
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/system_misc.h>
22#include <asm/system_info.h>
23#include <asm/tlbflush.h>
24
25#include "fault.h"
26
27#ifdef CONFIG_MMU
28
29/*
30 * This is useful to dump out the page tables associated with
31 * 'addr' in mm 'mm'.
32 */
33void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
34{
35 pgd_t *pgd;
36
37 if (!mm)
38 mm = &init_mm;
39
40 printk("%spgd = %p\n", lvl, mm->pgd);
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
103/*
104 * Oops. The kernel tried to access some page that wasn't present.
105 */
106static void
107__do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
108 struct pt_regs *regs)
109{
110 /*
111 * Are we prepared to handle this kernel fault?
112 */
113 if (fixup_exception(regs))
114 return;
115
116 /*
117 * No handler, we'll have to terminate things with extreme prejudice.
118 */
119 bust_spinlocks(1);
120 pr_alert("8<--- cut here ---\n");
121 pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
122 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
123 "paging request", addr);
124
125 show_pte(KERN_ALERT, mm, addr);
126 die("Oops", regs, fsr);
127 bust_spinlocks(0);
128 do_exit(SIGKILL);
129}
130
131/*
132 * Something tried to access memory that isn't in our memory map..
133 * User mode accesses just cause a SIGSEGV
134 */
135static void
136__do_user_fault(unsigned long addr, unsigned int fsr, unsigned int sig,
137 int code, struct pt_regs *regs)
138{
139 struct task_struct *tsk = current;
140
141 if (addr > TASK_SIZE)
142 harden_branch_predictor();
143
144#ifdef CONFIG_DEBUG_USER
145 if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
146 ((user_debug & UDBG_BUS) && (sig == SIGBUS))) {
147 pr_err("8<--- cut here ---\n");
148 pr_err("%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
149 tsk->comm, sig, addr, fsr);
150 show_pte(KERN_ERR, tsk->mm, addr);
151 show_regs(regs);
152 }
153#endif
154#ifndef CONFIG_KUSER_HELPERS
155 if ((sig == SIGSEGV) && ((addr & PAGE_MASK) == 0xffff0000))
156 printk_ratelimited(KERN_DEBUG
157 "%s: CONFIG_KUSER_HELPERS disabled at 0x%08lx\n",
158 tsk->comm, addr);
159#endif
160
161 tsk->thread.address = addr;
162 tsk->thread.error_code = fsr;
163 tsk->thread.trap_no = 14;
164 force_sig_fault(sig, code, (void __user *)addr);
165}
166
167void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
168{
169 struct task_struct *tsk = current;
170 struct mm_struct *mm = tsk->active_mm;
171
172 /*
173 * If we are in kernel mode at this point, we
174 * have no context to handle this fault with.
175 */
176 if (user_mode(regs))
177 __do_user_fault(addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
178 else
179 __do_kernel_fault(mm, addr, fsr, regs);
180}
181
182#ifdef CONFIG_MMU
183#define VM_FAULT_BADMAP 0x010000
184#define VM_FAULT_BADACCESS 0x020000
185
186/*
187 * Check that the permissions on the VMA allow for the fault which occurred.
188 * If we encountered a write fault, we must have write permission, otherwise
189 * we allow any permission.
190 */
191static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
192{
193 unsigned int mask = VM_ACCESS_FLAGS;
194
195 if ((fsr & FSR_WRITE) && !(fsr & FSR_CM))
196 mask = VM_WRITE;
197 if (fsr & FSR_LNX_PF)
198 mask = VM_EXEC;
199
200 return vma->vm_flags & mask ? false : true;
201}
202
203static vm_fault_t __kprobes
204__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
205 unsigned int flags, struct task_struct *tsk,
206 struct pt_regs *regs)
207{
208 struct vm_area_struct *vma;
209 vm_fault_t fault;
210
211 vma = find_vma(mm, addr);
212 fault = VM_FAULT_BADMAP;
213 if (unlikely(!vma))
214 goto out;
215 if (unlikely(vma->vm_start > addr))
216 goto check_stack;
217
218 /*
219 * Ok, we have a good vm_area for this
220 * memory access, so we can handle it.
221 */
222good_area:
223 if (access_error(fsr, vma)) {
224 fault = VM_FAULT_BADACCESS;
225 goto out;
226 }
227
228 return handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
229
230check_stack:
231 /* Don't allow expansion below FIRST_USER_ADDRESS */
232 if (vma->vm_flags & VM_GROWSDOWN &&
233 addr >= FIRST_USER_ADDRESS && !expand_stack(vma, addr))
234 goto good_area;
235out:
236 return fault;
237}
238
239static int __kprobes
240do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
241{
242 struct task_struct *tsk;
243 struct mm_struct *mm;
244 int sig, code;
245 vm_fault_t fault;
246 unsigned int flags = FAULT_FLAG_DEFAULT;
247
248 if (kprobe_page_fault(regs, fsr))
249 return 0;
250
251 tsk = current;
252 mm = tsk->mm;
253
254 /* Enable interrupts if they were enabled in the parent context. */
255 if (interrupts_enabled(regs))
256 local_irq_enable();
257
258 /*
259 * If we're in an interrupt or have no user
260 * context, we must not take the fault..
261 */
262 if (faulthandler_disabled() || !mm)
263 goto no_context;
264
265 if (user_mode(regs))
266 flags |= FAULT_FLAG_USER;
267 if ((fsr & FSR_WRITE) && !(fsr & FSR_CM))
268 flags |= FAULT_FLAG_WRITE;
269
270 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
271
272 /*
273 * As per x86, we may deadlock here. However, since the kernel only
274 * validly references user space from well defined areas of the code,
275 * we can bug out early if this is from code which shouldn't.
276 */
277 if (!mmap_read_trylock(mm)) {
278 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
279 goto no_context;
280retry:
281 mmap_read_lock(mm);
282 } else {
283 /*
284 * The above down_read_trylock() might have succeeded in
285 * which case, we'll have missed the might_sleep() from
286 * down_read()
287 */
288 might_sleep();
289#ifdef CONFIG_DEBUG_VM
290 if (!user_mode(regs) &&
291 !search_exception_tables(regs->ARM_pc))
292 goto no_context;
293#endif
294 }
295
296 fault = __do_page_fault(mm, addr, fsr, flags, tsk, regs);
297
298 /* If we need to retry but a fatal signal is pending, handle the
299 * signal first. We do not need to release the mmap_lock because
300 * it would already be released in __lock_page_or_retry in
301 * mm/filemap.c. */
302 if (fault_signal_pending(fault, regs)) {
303 if (!user_mode(regs))
304 goto no_context;
305 return 0;
306 }
307
308 if (!(fault & VM_FAULT_ERROR) && flags & FAULT_FLAG_ALLOW_RETRY) {
309 if (fault & VM_FAULT_RETRY) {
310 flags |= FAULT_FLAG_TRIED;
311 goto retry;
312 }
313 }
314
315 mmap_read_unlock(mm);
316
317 /*
318 * Handle the "normal" case first - VM_FAULT_MAJOR
319 */
320 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
321 return 0;
322
323 /*
324 * If we are in kernel mode at this point, we
325 * have no context to handle this fault with.
326 */
327 if (!user_mode(regs))
328 goto no_context;
329
330 if (fault & VM_FAULT_OOM) {
331 /*
332 * We ran out of memory, call the OOM killer, and return to
333 * userspace (which will retry the fault, or kill us if we
334 * got oom-killed)
335 */
336 pagefault_out_of_memory();
337 return 0;
338 }
339
340 if (fault & VM_FAULT_SIGBUS) {
341 /*
342 * We had some memory, but were unable to
343 * successfully fix up this page fault.
344 */
345 sig = SIGBUS;
346 code = BUS_ADRERR;
347 } else {
348 /*
349 * Something tried to access memory that
350 * isn't in our memory map..
351 */
352 sig = SIGSEGV;
353 code = fault == VM_FAULT_BADACCESS ?
354 SEGV_ACCERR : SEGV_MAPERR;
355 }
356
357 __do_user_fault(addr, fsr, sig, code, regs);
358 return 0;
359
360no_context:
361 __do_kernel_fault(mm, addr, fsr, regs);
362 return 0;
363}
364#else /* CONFIG_MMU */
365static int
366do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
367{
368 return 0;
369}
370#endif /* CONFIG_MMU */
371
372/*
373 * First Level Translation Fault Handler
374 *
375 * We enter here because the first level page table doesn't contain
376 * a valid entry for the address.
377 *
378 * If the address is in kernel space (>= TASK_SIZE), then we are
379 * probably faulting in the vmalloc() area.
380 *
381 * If the init_task's first level page tables contains the relevant
382 * entry, we copy the it to this task. If not, we send the process
383 * a signal, fixup the exception, or oops the kernel.
384 *
385 * NOTE! We MUST NOT take any locks for this case. We may be in an
386 * interrupt or a critical region, and should only copy the information
387 * from the master page table, nothing more.
388 */
389#ifdef CONFIG_MMU
390static int __kprobes
391do_translation_fault(unsigned long addr, unsigned int fsr,
392 struct pt_regs *regs)
393{
394 unsigned int index;
395 pgd_t *pgd, *pgd_k;
396 p4d_t *p4d, *p4d_k;
397 pud_t *pud, *pud_k;
398 pmd_t *pmd, *pmd_k;
399
400 if (addr < TASK_SIZE)
401 return do_page_fault(addr, fsr, regs);
402
403 if (user_mode(regs))
404 goto bad_area;
405
406 index = pgd_index(addr);
407
408 pgd = cpu_get_pgd() + index;
409 pgd_k = init_mm.pgd + index;
410
411 p4d = p4d_offset(pgd, addr);
412 p4d_k = p4d_offset(pgd_k, addr);
413
414 if (p4d_none(*p4d_k))
415 goto bad_area;
416 if (!p4d_present(*p4d))
417 set_p4d(p4d, *p4d_k);
418
419 pud = pud_offset(p4d, addr);
420 pud_k = pud_offset(p4d_k, addr);
421
422 if (pud_none(*pud_k))
423 goto bad_area;
424 if (!pud_present(*pud))
425 set_pud(pud, *pud_k);
426
427 pmd = pmd_offset(pud, addr);
428 pmd_k = pmd_offset(pud_k, addr);
429
430#ifdef CONFIG_ARM_LPAE
431 /*
432 * Only one hardware entry per PMD with LPAE.
433 */
434 index = 0;
435#else
436 /*
437 * On ARM one Linux PGD entry contains two hardware entries (see page
438 * tables layout in pgtable.h). We normally guarantee that we always
439 * fill both L1 entries. But create_mapping() doesn't follow the rule.
440 * It can create inidividual L1 entries, so here we have to call
441 * pmd_none() check for the entry really corresponded to address, not
442 * for the first of pair.
443 */
444 index = (addr >> SECTION_SHIFT) & 1;
445#endif
446 if (pmd_none(pmd_k[index]))
447 goto bad_area;
448
449 copy_pmd(pmd, pmd_k);
450 return 0;
451
452bad_area:
453 do_bad_area(addr, fsr, regs);
454 return 0;
455}
456#else /* CONFIG_MMU */
457static int
458do_translation_fault(unsigned long addr, unsigned int fsr,
459 struct pt_regs *regs)
460{
461 return 0;
462}
463#endif /* CONFIG_MMU */
464
465/*
466 * Some section permission faults need to be handled gracefully.
467 * They can happen due to a __{get,put}_user during an oops.
468 */
469#ifndef CONFIG_ARM_LPAE
470static int
471do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
472{
473 do_bad_area(addr, fsr, regs);
474 return 0;
475}
476#endif /* CONFIG_ARM_LPAE */
477
478/*
479 * This abort handler always returns "fault".
480 */
481static int
482do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
483{
484 return 1;
485}
486
487struct fsr_info {
488 int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
489 int sig;
490 int code;
491 const char *name;
492};
493
494/* FSR definition */
495#ifdef CONFIG_ARM_LPAE
496#include "fsr-3level.c"
497#else
498#include "fsr-2level.c"
499#endif
500
501void __init
502hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
503 int sig, int code, const char *name)
504{
505 if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
506 BUG();
507
508 fsr_info[nr].fn = fn;
509 fsr_info[nr].sig = sig;
510 fsr_info[nr].code = code;
511 fsr_info[nr].name = name;
512}
513
514/*
515 * Dispatch a data abort to the relevant handler.
516 */
517asmlinkage void
518do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
519{
520 const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
521
522 if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
523 return;
524
525 pr_alert("8<--- cut here ---\n");
526 pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
527 inf->name, fsr, addr);
528 show_pte(KERN_ALERT, current->mm, addr);
529
530 arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
531 fsr, 0);
532}
533
534void __init
535hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
536 int sig, int code, const char *name)
537{
538 if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
539 BUG();
540
541 ifsr_info[nr].fn = fn;
542 ifsr_info[nr].sig = sig;
543 ifsr_info[nr].code = code;
544 ifsr_info[nr].name = name;
545}
546
547asmlinkage void
548do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
549{
550 const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
551
552 if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
553 return;
554
555 pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
556 inf->name, ifsr, addr);
557
558 arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
559 ifsr, 0);
560}
561
562/*
563 * Abort handler to be used only during first unmasking of asynchronous aborts
564 * on the boot CPU. This makes sure that the machine will not die if the
565 * firmware/bootloader left an imprecise abort pending for us to trip over.
566 */
567static int __init early_abort_handler(unsigned long addr, unsigned int fsr,
568 struct pt_regs *regs)
569{
570 pr_warn("Hit pending asynchronous external abort (FSR=0x%08x) during "
571 "first unmask, this is most likely caused by a "
572 "firmware/bootloader bug.\n", fsr);
573
574 return 0;
575}
576
577void __init early_abt_enable(void)
578{
579 fsr_info[FSR_FS_AEA].fn = early_abort_handler;
580 local_abt_enable();
581 fsr_info[FSR_FS_AEA].fn = do_bad;
582}
583
584#ifndef CONFIG_ARM_LPAE
585static int __init exceptions_init(void)
586{
587 if (cpu_architecture() >= CPU_ARCH_ARMv6) {
588 hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
589 "I-cache maintenance fault");
590 }
591
592 if (cpu_architecture() >= CPU_ARCH_ARMv7) {
593 /*
594 * TODO: Access flag faults introduced in ARMv6K.
595 * Runtime check for 'K' extension is needed
596 */
597 hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
598 "section access flag fault");
599 hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
600 "section access flag fault");
601 }
602
603 return 0;
604}
605
606arch_initcall(exceptions_init);
607#endif