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