xref: /openbmc/linux/arch/arm/mm/fault.c (revision 8b35ca3e)
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  */
show_pte(const char * lvl,struct mm_struct * mm,unsigned long addr)34 void 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 */
show_pte(const char * lvl,struct mm_struct * mm,unsigned long addr)102 void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
103 { }
104 #endif					/* CONFIG_MMU */
105 
is_write_fault(unsigned int fsr)106 static inline bool is_write_fault(unsigned int fsr)
107 {
108 	return (fsr & FSR_WRITE) && !(fsr & FSR_CM);
109 }
110 
is_translation_fault(unsigned int fsr)111 static 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 
die_kernel_fault(const char * msg,struct mm_struct * mm,unsigned long addr,unsigned int fsr,struct pt_regs * regs)124 static 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  */
143 static void
__do_kernel_fault(struct mm_struct * mm,unsigned long addr,unsigned int fsr,struct pt_regs * regs)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  */
174 static void
__do_user_fault(unsigned long addr,unsigned int fsr,unsigned int sig,int code,struct pt_regs * regs)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 
do_bad_area(unsigned long addr,unsigned int fsr,struct pt_regs * regs)206 void 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 
is_permission_fault(unsigned int fsr)225 static 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 
238 static int __kprobes
do_page_fault(unsigned long addr,unsigned int fsr,struct pt_regs * regs)239 do_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 retry:
282 	vma = lock_mm_and_find_vma(mm, 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, 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, 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 
326 bad_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 
364 no_context:
365 	__do_kernel_fault(mm, addr, fsr, regs);
366 	return 0;
367 }
368 #else					/* CONFIG_MMU */
369 static int
do_page_fault(unsigned long addr,unsigned int fsr,struct pt_regs * regs)370 do_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
394 static int __kprobes
do_translation_fault(unsigned long addr,unsigned int fsr,struct pt_regs * regs)395 do_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, addr);
416 	p4d_k = p4d_offset(pgd_k, addr);
417 
418 	if (p4d_none(*p4d_k))
419 		goto bad_area;
420 	if (!p4d_present(*p4d))
421 		set_p4d(p4d, *p4d_k);
422 
423 	pud = pud_offset(p4d, addr);
424 	pud_k = pud_offset(p4d_k, addr);
425 
426 	if (pud_none(*pud_k))
427 		goto bad_area;
428 	if (!pud_present(*pud))
429 		set_pud(pud, *pud_k);
430 
431 	pmd = pmd_offset(pud, addr);
432 	pmd_k = pmd_offset(pud_k, 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_k[index]))
451 		goto bad_area;
452 
453 	copy_pmd(pmd, pmd_k);
454 	return 0;
455 
456 bad_area:
457 	do_bad_area(addr, fsr, regs);
458 	return 0;
459 }
460 #else					/* CONFIG_MMU */
461 static int
do_translation_fault(unsigned long addr,unsigned int fsr,struct pt_regs * regs)462 do_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
474 static int
do_sect_fault(unsigned long addr,unsigned int fsr,struct pt_regs * regs)475 do_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  */
485 static int
do_bad(unsigned long addr,unsigned int fsr,struct pt_regs * regs)486 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
487 {
488 	return 1;
489 }
490 
491 struct 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 
505 void __init
hook_fault_code(int nr,int (* fn)(unsigned long,unsigned int,struct pt_regs *),int sig,int code,const char * name)506 hook_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  */
521 asmlinkage void
do_DataAbort(unsigned long addr,unsigned int fsr,struct pt_regs * regs)522 do_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 
538 void __init
hook_ifault_code(int nr,int (* fn)(unsigned long,unsigned int,struct pt_regs *),int sig,int code,const char * name)539 hook_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 
551 asmlinkage void
do_PrefetchAbort(unsigned long addr,unsigned int ifsr,struct pt_regs * regs)552 do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
553 {
554 	const struct fsr_info *inf = ifsr_info + fsr_fs(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  */
early_abort_handler(unsigned long addr,unsigned int fsr,struct pt_regs * regs)571 static 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 
early_abt_enable(void)581 void __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
exceptions_init(void)589 static int __init exceptions_init(void)
590 {
591 	if (cpu_architecture() >= CPU_ARCH_ARMv6) {
592 		hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
593 				"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(3, do_bad, SIGSEGV, SEGV_MAPERR,
602 				"section access flag fault");
603 		hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
604 				"section access flag fault");
605 	}
606 
607 	return 0;
608 }
609 
610 arch_initcall(exceptions_init);
611 #endif
612