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1/*
2 * Based on arch/arm/mm/fault.c
3 *
4 * Copyright (C) 1995 Linus Torvalds
5 * Copyright (C) 1995-2004 Russell King
6 * Copyright (C) 2012 ARM Ltd.
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program. If not, see <http://www.gnu.org/licenses/>.
19 */
20
21#include <linux/module.h>
22#include <linux/signal.h>
23#include <linux/mm.h>
24#include <linux/hardirq.h>
25#include <linux/init.h>
26#include <linux/kprobes.h>
27#include <linux/uaccess.h>
28#include <linux/page-flags.h>
29#include <linux/sched.h>
30#include <linux/highmem.h>
31#include <linux/perf_event.h>
32
33#include <asm/cpufeature.h>
34#include <asm/exception.h>
35#include <asm/debug-monitors.h>
36#include <asm/esr.h>
37#include <asm/sysreg.h>
38#include <asm/system_misc.h>
39#include <asm/pgtable.h>
40#include <asm/tlbflush.h>
41
42static const char *fault_name(unsigned int esr);
43
44/*
45 * Dump out the page tables associated with 'addr' in mm 'mm'.
46 */
47void show_pte(struct mm_struct *mm, unsigned long addr)
48{
49 pgd_t *pgd;
50
51 if (!mm)
52 mm = &init_mm;
53
54 pr_alert("pgd = %p\n", mm->pgd);
55 pgd = pgd_offset(mm, addr);
56 pr_alert("[%08lx] *pgd=%016llx", addr, pgd_val(*pgd));
57
58 do {
59 pud_t *pud;
60 pmd_t *pmd;
61 pte_t *pte;
62
63 if (pgd_none(*pgd) || pgd_bad(*pgd))
64 break;
65
66 pud = pud_offset(pgd, addr);
67 printk(", *pud=%016llx", pud_val(*pud));
68 if (pud_none(*pud) || pud_bad(*pud))
69 break;
70
71 pmd = pmd_offset(pud, addr);
72 printk(", *pmd=%016llx", pmd_val(*pmd));
73 if (pmd_none(*pmd) || pmd_bad(*pmd))
74 break;
75
76 pte = pte_offset_map(pmd, addr);
77 printk(", *pte=%016llx", pte_val(*pte));
78 pte_unmap(pte);
79 } while(0);
80
81 printk("\n");
82}
83
84/*
85 * The kernel tried to access some page that wasn't present.
86 */
87static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr,
88 unsigned int esr, struct pt_regs *regs)
89{
90 /*
91 * Are we prepared to handle this kernel fault?
92 */
93 if (fixup_exception(regs))
94 return;
95
96 /*
97 * No handler, we'll have to terminate things with extreme prejudice.
98 */
99 bust_spinlocks(1);
100 pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
101 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
102 "paging request", addr);
103
104 show_pte(mm, addr);
105 die("Oops", regs, esr);
106 bust_spinlocks(0);
107 do_exit(SIGKILL);
108}
109
110/*
111 * Something tried to access memory that isn't in our memory map. User mode
112 * accesses just cause a SIGSEGV
113 */
114static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
115 unsigned int esr, unsigned int sig, int code,
116 struct pt_regs *regs)
117{
118 struct siginfo si;
119
120 if (unhandled_signal(tsk, sig) && show_unhandled_signals_ratelimited()) {
121 pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n",
122 tsk->comm, task_pid_nr(tsk), fault_name(esr), sig,
123 addr, esr);
124 show_pte(tsk->mm, addr);
125 show_regs(regs);
126 }
127
128 tsk->thread.fault_address = addr;
129 tsk->thread.fault_code = esr;
130 si.si_signo = sig;
131 si.si_errno = 0;
132 si.si_code = code;
133 si.si_addr = (void __user *)addr;
134 force_sig_info(sig, &si, tsk);
135}
136
137static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs)
138{
139 struct task_struct *tsk = current;
140 struct mm_struct *mm = tsk->active_mm;
141
142 /*
143 * If we are in kernel mode at this point, we have no context to
144 * handle this fault with.
145 */
146 if (user_mode(regs))
147 __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs);
148 else
149 __do_kernel_fault(mm, addr, esr, regs);
150}
151
152#define VM_FAULT_BADMAP 0x010000
153#define VM_FAULT_BADACCESS 0x020000
154
155#define ESR_LNX_EXEC (1 << 24)
156
157static int __do_page_fault(struct mm_struct *mm, unsigned long addr,
158 unsigned int mm_flags, unsigned long vm_flags,
159 struct task_struct *tsk)
160{
161 struct vm_area_struct *vma;
162 int fault;
163
164 vma = find_vma(mm, addr);
165 fault = VM_FAULT_BADMAP;
166 if (unlikely(!vma))
167 goto out;
168 if (unlikely(vma->vm_start > addr))
169 goto check_stack;
170
171 /*
172 * Ok, we have a good vm_area for this memory access, so we can handle
173 * it.
174 */
175good_area:
176 /*
177 * Check that the permissions on the VMA allow for the fault which
178 * occurred. If we encountered a write or exec fault, we must have
179 * appropriate permissions, otherwise we allow any permission.
180 */
181 if (!(vma->vm_flags & vm_flags)) {
182 fault = VM_FAULT_BADACCESS;
183 goto out;
184 }
185
186 return handle_mm_fault(mm, vma, addr & PAGE_MASK, mm_flags);
187
188check_stack:
189 if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
190 goto good_area;
191out:
192 return fault;
193}
194
195static inline int permission_fault(unsigned int esr)
196{
197 unsigned int ec = (esr & ESR_ELx_EC_MASK) >> ESR_ELx_EC_SHIFT;
198 unsigned int fsc_type = esr & ESR_ELx_FSC_TYPE;
199
200 return (ec == ESR_ELx_EC_DABT_CUR && fsc_type == ESR_ELx_FSC_PERM);
201}
202
203static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
204 struct pt_regs *regs)
205{
206 struct task_struct *tsk;
207 struct mm_struct *mm;
208 int fault, sig, code;
209 unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC;
210 unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
211
212 tsk = current;
213 mm = tsk->mm;
214
215 /* Enable interrupts if they were enabled in the parent context. */
216 if (interrupts_enabled(regs))
217 local_irq_enable();
218
219 /*
220 * If we're in an interrupt or have no user context, we must not take
221 * the fault.
222 */
223 if (faulthandler_disabled() || !mm)
224 goto no_context;
225
226 if (user_mode(regs))
227 mm_flags |= FAULT_FLAG_USER;
228
229 if (esr & ESR_LNX_EXEC) {
230 vm_flags = VM_EXEC;
231 } else if ((esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM)) {
232 vm_flags = VM_WRITE;
233 mm_flags |= FAULT_FLAG_WRITE;
234 }
235
236 if (permission_fault(esr) && (addr < USER_DS)) {
237 if (get_fs() == KERNEL_DS)
238 die("Accessing user space memory with fs=KERNEL_DS", regs, esr);
239
240 if (!search_exception_tables(regs->pc))
241 die("Accessing user space memory outside uaccess.h routines", regs, esr);
242 }
243
244 /*
245 * As per x86, we may deadlock here. However, since the kernel only
246 * validly references user space from well defined areas of the code,
247 * we can bug out early if this is from code which shouldn't.
248 */
249 if (!down_read_trylock(&mm->mmap_sem)) {
250 if (!user_mode(regs) && !search_exception_tables(regs->pc))
251 goto no_context;
252retry:
253 down_read(&mm->mmap_sem);
254 } else {
255 /*
256 * The above down_read_trylock() might have succeeded in which
257 * case, we'll have missed the might_sleep() from down_read().
258 */
259 might_sleep();
260#ifdef CONFIG_DEBUG_VM
261 if (!user_mode(regs) && !search_exception_tables(regs->pc))
262 goto no_context;
263#endif
264 }
265
266 fault = __do_page_fault(mm, addr, mm_flags, vm_flags, tsk);
267
268 /*
269 * If we need to retry but a fatal signal is pending, handle the
270 * signal first. We do not need to release the mmap_sem because it
271 * would already be released in __lock_page_or_retry in mm/filemap.c.
272 */
273 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
274 return 0;
275
276 /*
277 * Major/minor page fault accounting is only done on the initial
278 * attempt. If we go through a retry, it is extremely likely that the
279 * page will be found in page cache at that point.
280 */
281
282 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
283 if (mm_flags & FAULT_FLAG_ALLOW_RETRY) {
284 if (fault & VM_FAULT_MAJOR) {
285 tsk->maj_flt++;
286 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs,
287 addr);
288 } else {
289 tsk->min_flt++;
290 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs,
291 addr);
292 }
293 if (fault & VM_FAULT_RETRY) {
294 /*
295 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of
296 * starvation.
297 */
298 mm_flags &= ~FAULT_FLAG_ALLOW_RETRY;
299 mm_flags |= FAULT_FLAG_TRIED;
300 goto retry;
301 }
302 }
303
304 up_read(&mm->mmap_sem);
305
306 /*
307 * Handle the "normal" case first - VM_FAULT_MAJOR
308 */
309 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP |
310 VM_FAULT_BADACCESS))))
311 return 0;
312
313 /*
314 * If we are in kernel mode at this point, we have no context to
315 * handle this fault with.
316 */
317 if (!user_mode(regs))
318 goto no_context;
319
320 if (fault & VM_FAULT_OOM) {
321 /*
322 * We ran out of memory, call the OOM killer, and return to
323 * userspace (which will retry the fault, or kill us if we got
324 * oom-killed).
325 */
326 pagefault_out_of_memory();
327 return 0;
328 }
329
330 if (fault & VM_FAULT_SIGBUS) {
331 /*
332 * We had some memory, but were unable to successfully fix up
333 * this page fault.
334 */
335 sig = SIGBUS;
336 code = BUS_ADRERR;
337 } else {
338 /*
339 * Something tried to access memory that isn't in our memory
340 * map.
341 */
342 sig = SIGSEGV;
343 code = fault == VM_FAULT_BADACCESS ?
344 SEGV_ACCERR : SEGV_MAPERR;
345 }
346
347 __do_user_fault(tsk, addr, esr, sig, code, regs);
348 return 0;
349
350no_context:
351 __do_kernel_fault(mm, addr, esr, regs);
352 return 0;
353}
354
355/*
356 * First Level Translation Fault Handler
357 *
358 * We enter here because the first level page table doesn't contain a valid
359 * entry for the address.
360 *
361 * If the address is in kernel space (>= TASK_SIZE), then we are probably
362 * faulting in the vmalloc() area.
363 *
364 * If the init_task's first level page tables contains the relevant entry, we
365 * copy the it to this task. If not, we send the process a signal, fixup the
366 * exception, or oops the kernel.
367 *
368 * NOTE! We MUST NOT take any locks for this case. We may be in an interrupt
369 * or a critical region, and should only copy the information from the master
370 * page table, nothing more.
371 */
372static int __kprobes do_translation_fault(unsigned long addr,
373 unsigned int esr,
374 struct pt_regs *regs)
375{
376 if (addr < TASK_SIZE)
377 return do_page_fault(addr, esr, regs);
378
379 do_bad_area(addr, esr, regs);
380 return 0;
381}
382
383static int do_alignment_fault(unsigned long addr, unsigned int esr,
384 struct pt_regs *regs)
385{
386 do_bad_area(addr, esr, regs);
387 return 0;
388}
389
390/*
391 * This abort handler always returns "fault".
392 */
393static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs)
394{
395 return 1;
396}
397
398static struct fault_info {
399 int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs);
400 int sig;
401 int code;
402 const char *name;
403} fault_info[] = {
404 { do_bad, SIGBUS, 0, "ttbr address size fault" },
405 { do_bad, SIGBUS, 0, "level 1 address size fault" },
406 { do_bad, SIGBUS, 0, "level 2 address size fault" },
407 { do_bad, SIGBUS, 0, "level 3 address size fault" },
408 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 0 translation fault" },
409 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" },
410 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" },
411 { do_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" },
412 { do_bad, SIGBUS, 0, "unknown 8" },
413 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" },
414 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" },
415 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 access flag fault" },
416 { do_bad, SIGBUS, 0, "unknown 12" },
417 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" },
418 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" },
419 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" },
420 { do_bad, SIGBUS, 0, "synchronous external abort" },
421 { do_bad, SIGBUS, 0, "unknown 17" },
422 { do_bad, SIGBUS, 0, "unknown 18" },
423 { do_bad, SIGBUS, 0, "unknown 19" },
424 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
425 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
426 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
427 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
428 { do_bad, SIGBUS, 0, "synchronous parity error" },
429 { do_bad, SIGBUS, 0, "unknown 25" },
430 { do_bad, SIGBUS, 0, "unknown 26" },
431 { do_bad, SIGBUS, 0, "unknown 27" },
432 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" },
433 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" },
434 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" },
435 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" },
436 { do_bad, SIGBUS, 0, "unknown 32" },
437 { do_alignment_fault, SIGBUS, BUS_ADRALN, "alignment fault" },
438 { do_bad, SIGBUS, 0, "unknown 34" },
439 { do_bad, SIGBUS, 0, "unknown 35" },
440 { do_bad, SIGBUS, 0, "unknown 36" },
441 { do_bad, SIGBUS, 0, "unknown 37" },
442 { do_bad, SIGBUS, 0, "unknown 38" },
443 { do_bad, SIGBUS, 0, "unknown 39" },
444 { do_bad, SIGBUS, 0, "unknown 40" },
445 { do_bad, SIGBUS, 0, "unknown 41" },
446 { do_bad, SIGBUS, 0, "unknown 42" },
447 { do_bad, SIGBUS, 0, "unknown 43" },
448 { do_bad, SIGBUS, 0, "unknown 44" },
449 { do_bad, SIGBUS, 0, "unknown 45" },
450 { do_bad, SIGBUS, 0, "unknown 46" },
451 { do_bad, SIGBUS, 0, "unknown 47" },
452 { do_bad, SIGBUS, 0, "TLB conflict abort" },
453 { do_bad, SIGBUS, 0, "unknown 49" },
454 { do_bad, SIGBUS, 0, "unknown 50" },
455 { do_bad, SIGBUS, 0, "unknown 51" },
456 { do_bad, SIGBUS, 0, "implementation fault (lockdown abort)" },
457 { do_bad, SIGBUS, 0, "implementation fault (unsupported exclusive)" },
458 { do_bad, SIGBUS, 0, "unknown 54" },
459 { do_bad, SIGBUS, 0, "unknown 55" },
460 { do_bad, SIGBUS, 0, "unknown 56" },
461 { do_bad, SIGBUS, 0, "unknown 57" },
462 { do_bad, SIGBUS, 0, "unknown 58" },
463 { do_bad, SIGBUS, 0, "unknown 59" },
464 { do_bad, SIGBUS, 0, "unknown 60" },
465 { do_bad, SIGBUS, 0, "section domain fault" },
466 { do_bad, SIGBUS, 0, "page domain fault" },
467 { do_bad, SIGBUS, 0, "unknown 63" },
468};
469
470static const char *fault_name(unsigned int esr)
471{
472 const struct fault_info *inf = fault_info + (esr & 63);
473 return inf->name;
474}
475
476/*
477 * Dispatch a data abort to the relevant handler.
478 */
479asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
480 struct pt_regs *regs)
481{
482 const struct fault_info *inf = fault_info + (esr & 63);
483 struct siginfo info;
484
485 if (!inf->fn(addr, esr, regs))
486 return;
487
488 pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n",
489 inf->name, esr, addr);
490
491 info.si_signo = inf->sig;
492 info.si_errno = 0;
493 info.si_code = inf->code;
494 info.si_addr = (void __user *)addr;
495 arm64_notify_die("", regs, &info, esr);
496}
497
498/*
499 * Handle stack alignment exceptions.
500 */
501asmlinkage void __exception do_sp_pc_abort(unsigned long addr,
502 unsigned int esr,
503 struct pt_regs *regs)
504{
505 struct siginfo info;
506 struct task_struct *tsk = current;
507
508 if (show_unhandled_signals && unhandled_signal(tsk, SIGBUS))
509 pr_info_ratelimited("%s[%d]: %s exception: pc=%p sp=%p\n",
510 tsk->comm, task_pid_nr(tsk),
511 esr_get_class_string(esr), (void *)regs->pc,
512 (void *)regs->sp);
513
514 info.si_signo = SIGBUS;
515 info.si_errno = 0;
516 info.si_code = BUS_ADRALN;
517 info.si_addr = (void __user *)addr;
518 arm64_notify_die("Oops - SP/PC alignment exception", regs, &info, esr);
519}
520
521int __init early_brk64(unsigned long addr, unsigned int esr,
522 struct pt_regs *regs);
523
524/*
525 * __refdata because early_brk64 is __init, but the reference to it is
526 * clobbered at arch_initcall time.
527 * See traps.c and debug-monitors.c:debug_traps_init().
528 */
529static struct fault_info __refdata debug_fault_info[] = {
530 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware breakpoint" },
531 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware single-step" },
532 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware watchpoint" },
533 { do_bad, SIGBUS, 0, "unknown 3" },
534 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch32 BKPT" },
535 { do_bad, SIGTRAP, 0, "aarch32 vector catch" },
536 { early_brk64, SIGTRAP, TRAP_BRKPT, "aarch64 BRK" },
537 { do_bad, SIGBUS, 0, "unknown 7" },
538};
539
540void __init hook_debug_fault_code(int nr,
541 int (*fn)(unsigned long, unsigned int, struct pt_regs *),
542 int sig, int code, const char *name)
543{
544 BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info));
545
546 debug_fault_info[nr].fn = fn;
547 debug_fault_info[nr].sig = sig;
548 debug_fault_info[nr].code = code;
549 debug_fault_info[nr].name = name;
550}
551
552asmlinkage int __exception do_debug_exception(unsigned long addr,
553 unsigned int esr,
554 struct pt_regs *regs)
555{
556 const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr);
557 struct siginfo info;
558
559 if (!inf->fn(addr, esr, regs))
560 return 1;
561
562 pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n",
563 inf->name, esr, addr);
564
565 info.si_signo = inf->sig;
566 info.si_errno = 0;
567 info.si_code = inf->code;
568 info.si_addr = (void __user *)addr;
569 arm64_notify_die("", regs, &info, 0);
570
571 return 0;
572}
573
574#ifdef CONFIG_ARM64_PAN
575void cpu_enable_pan(void *__unused)
576{
577 config_sctlr_el1(SCTLR_EL1_SPAN, 0);
578}
579#endif /* CONFIG_ARM64_PAN */
580
581#ifdef CONFIG_ARM64_UAO
582/*
583 * Kernel threads have fs=KERNEL_DS by default, and don't need to call
584 * set_fs(), devtmpfs in particular relies on this behaviour.
585 * We need to enable the feature at runtime (instead of adding it to
586 * PSR_MODE_EL1h) as the feature may not be implemented by the cpu.
587 */
588void cpu_enable_uao(void *__unused)
589{
590 asm(SET_PSTATE_UAO(1));
591}
592#endif /* CONFIG_ARM64_UAO */