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, address: addr);
51 if (p4d_none(p4d: *p4d))
52 break;
53
54 if (p4d_bad(p4d: *p4d)) {
55 pr_cont("(bad)");
56 break;
57 }
58
59 pud = pud_offset(p4d, address: addr);
60 if (PTRS_PER_PUD != 1)
61 pr_cont(", *pud=%08llx", (long long)pud_val(*pud));
62
63 if (pud_none(pud: *pud))
64 break;
65
66 if (pud_bad(pud: *pud)) {
67 pr_cont("(bad)");
68 break;
69 }
70
71 pmd = pmd_offset(pud, address: addr);
72 if (PTRS_PER_PMD != 1)
73 pr_cont(", *pmd=%08llx", (long long)pmd_val(*pmd));
74
75 if (pmd_none(pmd: *pmd))
76 break;
77
78 if (pmd_bad(pmd: *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(yes: 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(yes: 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: 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, addr: (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, trap: 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(msg: "execution of memory",
276 mm, addr, fsr, regs);
277 }
278
279 perf_sw_event(event_id: PERF_COUNT_SW_PAGE_FAULTS, nr: 1, regs, addr);
280
281retry:
282 vma = lock_mm_and_find_vma(mm, address: addr, regs);
283 if (unlikely(!vma)) {
284 fault = VM_FAULT_BADMAP;
285 goto bad_area;
286 }
287
288 /*
289 * ok, we have a good vm_area for this memory access, check the
290 * permissions on the VMA allow for the fault which occurred.
291 */
292 if (!(vma->vm_flags & vm_flags))
293 fault = VM_FAULT_BADACCESS;
294 else
295 fault = handle_mm_fault(vma, address: addr & PAGE_MASK, flags, regs);
296
297 /* If we need to retry but a fatal signal is pending, handle the
298 * signal first. We do not need to release the mmap_lock because
299 * it would already be released in __lock_page_or_retry in
300 * mm/filemap.c. */
301 if (fault_signal_pending(fault_flags: fault, regs)) {
302 if (!user_mode(regs))
303 goto no_context;
304 return 0;
305 }
306
307 /* The fault is fully completed (including releasing mmap lock) */
308 if (fault & VM_FAULT_COMPLETED)
309 return 0;
310
311 if (!(fault & VM_FAULT_ERROR)) {
312 if (fault & VM_FAULT_RETRY) {
313 flags |= FAULT_FLAG_TRIED;
314 goto retry;
315 }
316 }
317
318 mmap_read_unlock(mm);
319
320 /*
321 * Handle the "normal" case first - VM_FAULT_MAJOR
322 */
323 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
324 return 0;
325
326bad_area:
327 /*
328 * If we are in kernel mode at this point, we
329 * have no context to handle this fault with.
330 */
331 if (!user_mode(regs))
332 goto no_context;
333
334 if (fault & VM_FAULT_OOM) {
335 /*
336 * We ran out of memory, call the OOM killer, and return to
337 * userspace (which will retry the fault, or kill us if we
338 * got oom-killed)
339 */
340 pagefault_out_of_memory();
341 return 0;
342 }
343
344 if (fault & VM_FAULT_SIGBUS) {
345 /*
346 * We had some memory, but were unable to
347 * successfully fix up this page fault.
348 */
349 sig = SIGBUS;
350 code = BUS_ADRERR;
351 } else {
352 /*
353 * Something tried to access memory that
354 * isn't in our memory map..
355 */
356 sig = SIGSEGV;
357 code = fault == VM_FAULT_BADACCESS ?
358 SEGV_ACCERR : SEGV_MAPERR;
359 }
360
361 __do_user_fault(addr, fsr, sig, code, regs);
362 return 0;
363
364no_context:
365 __do_kernel_fault(mm, addr, fsr, regs);
366 return 0;
367}
368#else /* CONFIG_MMU */
369static int
370do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
371{
372 return 0;
373}
374#endif /* CONFIG_MMU */
375
376/*
377 * First Level Translation Fault Handler
378 *
379 * We enter here because the first level page table doesn't contain
380 * a valid entry for the address.
381 *
382 * If the address is in kernel space (>= TASK_SIZE), then we are
383 * probably faulting in the vmalloc() area.
384 *
385 * If the init_task's first level page tables contains the relevant
386 * entry, we copy the it to this task. If not, we send the process
387 * a signal, fixup the exception, or oops the kernel.
388 *
389 * NOTE! We MUST NOT take any locks for this case. We may be in an
390 * interrupt or a critical region, and should only copy the information
391 * from the master page table, nothing more.
392 */
393#ifdef CONFIG_MMU
394static int __kprobes
395do_translation_fault(unsigned long addr, unsigned int fsr,
396 struct pt_regs *regs)
397{
398 unsigned int index;
399 pgd_t *pgd, *pgd_k;
400 p4d_t *p4d, *p4d_k;
401 pud_t *pud, *pud_k;
402 pmd_t *pmd, *pmd_k;
403
404 if (addr < TASK_SIZE)
405 return do_page_fault(addr, fsr, regs);
406
407 if (user_mode(regs))
408 goto bad_area;
409
410 index = pgd_index(addr);
411
412 pgd = cpu_get_pgd() + index;
413 pgd_k = init_mm.pgd + index;
414
415 p4d = p4d_offset(pgd, address: addr);
416 p4d_k = p4d_offset(pgd: pgd_k, address: addr);
417
418 if (p4d_none(p4d: *p4d_k))
419 goto bad_area;
420 if (!p4d_present(p4d: *p4d))
421 set_p4d(p4dp: p4d, p4d: *p4d_k);
422
423 pud = pud_offset(p4d, address: addr);
424 pud_k = pud_offset(p4d: p4d_k, address: addr);
425
426 if (pud_none(pud: *pud_k))
427 goto bad_area;
428 if (!pud_present(pud: *pud))
429 set_pud(pudp: pud, pud: *pud_k);
430
431 pmd = pmd_offset(pud, address: addr);
432 pmd_k = pmd_offset(pud: pud_k, address: addr);
433
434#ifdef CONFIG_ARM_LPAE
435 /*
436 * Only one hardware entry per PMD with LPAE.
437 */
438 index = 0;
439#else
440 /*
441 * On ARM one Linux PGD entry contains two hardware entries (see page
442 * tables layout in pgtable.h). We normally guarantee that we always
443 * fill both L1 entries. But create_mapping() doesn't follow the rule.
444 * It can create inidividual L1 entries, so here we have to call
445 * pmd_none() check for the entry really corresponded to address, not
446 * for the first of pair.
447 */
448 index = (addr >> SECTION_SHIFT) & 1;
449#endif
450 if (pmd_none(pmd: pmd_k[index]))
451 goto bad_area;
452
453 copy_pmd(pmd, pmd_k);
454 return 0;
455
456bad_area:
457 do_bad_area(addr, fsr, regs);
458 return 0;
459}
460#else /* CONFIG_MMU */
461static int
462do_translation_fault(unsigned long addr, unsigned int fsr,
463 struct pt_regs *regs)
464{
465 return 0;
466}
467#endif /* CONFIG_MMU */
468
469/*
470 * Some section permission faults need to be handled gracefully.
471 * They can happen due to a __{get,put}_user during an oops.
472 */
473#ifndef CONFIG_ARM_LPAE
474static int
475do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
476{
477 do_bad_area(addr, fsr, regs);
478 return 0;
479}
480#endif /* CONFIG_ARM_LPAE */
481
482/*
483 * This abort handler always returns "fault".
484 */
485static int
486do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
487{
488 return 1;
489}
490
491struct fsr_info {
492 int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
493 int sig;
494 int code;
495 const char *name;
496};
497
498/* FSR definition */
499#ifdef CONFIG_ARM_LPAE
500#include "fsr-3level.c"
501#else
502#include "fsr-2level.c"
503#endif
504
505void __init
506hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
507 int sig, int code, const char *name)
508{
509 if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
510 BUG();
511
512 fsr_info[nr].fn = fn;
513 fsr_info[nr].sig = sig;
514 fsr_info[nr].code = code;
515 fsr_info[nr].name = name;
516}
517
518/*
519 * Dispatch a data abort to the relevant handler.
520 */
521asmlinkage void
522do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
523{
524 const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
525
526 if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
527 return;
528
529 pr_alert("8<--- cut here ---\n");
530 pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
531 inf->name, fsr, addr);
532 show_pte(KERN_ALERT, current->mm, addr);
533
534 arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
535 fsr, 0);
536}
537
538void __init
539hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
540 int sig, int code, const char *name)
541{
542 if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
543 BUG();
544
545 ifsr_info[nr].fn = fn;
546 ifsr_info[nr].sig = sig;
547 ifsr_info[nr].code = code;
548 ifsr_info[nr].name = name;
549}
550
551asmlinkage void
552do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
553{
554 const struct fsr_info *inf = ifsr_info + fsr_fs(fsr: ifsr);
555
556 if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
557 return;
558
559 pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
560 inf->name, ifsr, addr);
561
562 arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
563 ifsr, 0);
564}
565
566/*
567 * Abort handler to be used only during first unmasking of asynchronous aborts
568 * on the boot CPU. This makes sure that the machine will not die if the
569 * firmware/bootloader left an imprecise abort pending for us to trip over.
570 */
571static int __init early_abort_handler(unsigned long addr, unsigned int fsr,
572 struct pt_regs *regs)
573{
574 pr_warn("Hit pending asynchronous external abort (FSR=0x%08x) during "
575 "first unmask, this is most likely caused by a "
576 "firmware/bootloader bug.\n", fsr);
577
578 return 0;
579}
580
581void __init early_abt_enable(void)
582{
583 fsr_info[FSR_FS_AEA].fn = early_abort_handler;
584 local_abt_enable();
585 fsr_info[FSR_FS_AEA].fn = do_bad;
586}
587
588#ifndef CONFIG_ARM_LPAE
589static int __init exceptions_init(void)
590{
591 if (cpu_architecture() >= CPU_ARCH_ARMv6) {
592 hook_fault_code(nr: 4, fn: do_translation_fault, SIGSEGV, SEGV_MAPERR,
593 name: "I-cache maintenance fault");
594 }
595
596 if (cpu_architecture() >= CPU_ARCH_ARMv7) {
597 /*
598 * TODO: Access flag faults introduced in ARMv6K.
599 * Runtime check for 'K' extension is needed
600 */
601 hook_fault_code(nr: 3, fn: do_bad, SIGSEGV, SEGV_MAPERR,
602 name: "section access flag fault");
603 hook_fault_code(nr: 6, fn: do_bad, SIGSEGV, SEGV_MAPERR,
604 name: "section access flag fault");
605 }
606
607 return 0;
608}
609
610arch_initcall(exceptions_init);
611#endif
612

source code of linux/arch/arm/mm/fault.c