xref: /linux/arch/arm/kernel/traps.c (revision fcb3ad4366b9c810cbb9da34c076a9a52d8aa1e0)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  linux/arch/arm/kernel/traps.c
4  *
5  *  Copyright (C) 1995-2009 Russell King
6  *  Fragments that appear the same as linux/arch/i386/kernel/traps.c (C) Linus Torvalds
7  *
8  *  'traps.c' handles hardware exceptions after we have saved some state in
9  *  'linux/arch/arm/lib/traps.S'.  Mostly a debugging aid, but will probably
10  *  kill the offending process.
11  */
12 #include <linux/signal.h>
13 #include <linux/personality.h>
14 #include <linux/kallsyms.h>
15 #include <linux/spinlock.h>
16 #include <linux/uaccess.h>
17 #include <linux/hardirq.h>
18 #include <linux/kdebug.h>
19 #include <linux/kprobes.h>
20 #include <linux/module.h>
21 #include <linux/kexec.h>
22 #include <linux/bug.h>
23 #include <linux/delay.h>
24 #include <linux/init.h>
25 #include <linux/sched/signal.h>
26 #include <linux/sched/debug.h>
27 #include <linux/sched/task_stack.h>
28 #include <linux/irq.h>
29 #include <linux/vmalloc.h>
30 
31 #include <linux/atomic.h>
32 #include <asm/cacheflush.h>
33 #include <asm/exception.h>
34 #include <asm/spectre.h>
35 #include <asm/unistd.h>
36 #include <asm/traps.h>
37 #include <asm/ptrace.h>
38 #include <asm/unwind.h>
39 #include <asm/tls.h>
40 #include <asm/stacktrace.h>
41 #include <asm/system_misc.h>
42 #include <asm/opcodes.h>
43 
44 
45 static const char *handler[]= {
46 	"prefetch abort",
47 	"data abort",
48 	"address exception",
49 	"interrupt",
50 	"undefined instruction",
51 };
52 
53 void *vectors_page;
54 
55 #ifdef CONFIG_DEBUG_USER
56 unsigned int user_debug;
57 
58 static int __init user_debug_setup(char *str)
59 {
60 	get_option(&str, &user_debug);
61 	return 1;
62 }
63 __setup("user_debug=", user_debug_setup);
64 #endif
65 
66 void dump_backtrace_entry(unsigned long where, unsigned long from,
67 			  unsigned long frame, const char *loglvl)
68 {
69 	unsigned long end = frame + 4 + sizeof(struct pt_regs);
70 
71 	if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER) &&
72 	    IS_ENABLED(CONFIG_CC_IS_GCC) &&
73 	    end > ALIGN(frame, THREAD_SIZE)) {
74 		/*
75 		 * If we are walking past the end of the stack, it may be due
76 		 * to the fact that we are on an IRQ or overflow stack. In this
77 		 * case, we can load the address of the other stack from the
78 		 * frame record.
79 		 */
80 		frame = ((unsigned long *)frame)[-2] - 4;
81 		end = frame + 4 + sizeof(struct pt_regs);
82 	}
83 
84 #ifndef CONFIG_KALLSYMS
85 	printk("%sFunction entered at [<%08lx>] from [<%08lx>]\n",
86 		loglvl, where, from);
87 #elif defined CONFIG_BACKTRACE_VERBOSE
88 	printk("%s[<%08lx>] (%ps) from [<%08lx>] (%pS)\n",
89 		loglvl, where, (void *)where, from, (void *)from);
90 #else
91 	printk("%s %ps from %pS\n", loglvl, (void *)where, (void *)from);
92 #endif
93 
94 	if (in_entry_text(from) && end <= ALIGN(frame, THREAD_SIZE))
95 		dump_mem(loglvl, "Exception stack", frame + 4, end);
96 }
97 
98 void dump_backtrace_stm(u32 *stack, u32 instruction, const char *loglvl)
99 {
100 	char str[80], *p;
101 	unsigned int x;
102 	int reg;
103 
104 	for (reg = 10, x = 0, p = str; reg >= 0; reg--) {
105 		if (instruction & BIT(reg)) {
106 			p += sprintf(p, " r%d:%08x", reg, *stack--);
107 			if (++x == 6) {
108 				x = 0;
109 				p = str;
110 				printk("%s%s\n", loglvl, str);
111 			}
112 		}
113 	}
114 	if (p != str)
115 		printk("%s%s\n", loglvl, str);
116 }
117 
118 #ifndef CONFIG_ARM_UNWIND
119 /*
120  * Stack pointers should always be within the kernels view of
121  * physical memory.  If it is not there, then we can't dump
122  * out any information relating to the stack.
123  */
124 static int verify_stack(unsigned long sp)
125 {
126 	if (sp < PAGE_OFFSET ||
127 	    (!IS_ENABLED(CONFIG_VMAP_STACK) &&
128 	     sp > (unsigned long)high_memory && high_memory != NULL))
129 		return -EFAULT;
130 
131 	return 0;
132 }
133 #endif
134 
135 /*
136  * Dump out the contents of some memory nicely...
137  */
138 void dump_mem(const char *lvl, const char *str, unsigned long bottom,
139 	      unsigned long top)
140 {
141 	unsigned long first;
142 	int i;
143 
144 	printk("%s%s(0x%08lx to 0x%08lx)\n", lvl, str, bottom, top);
145 
146 	for (first = bottom & ~31; first < top; first += 32) {
147 		unsigned long p;
148 		char str[sizeof(" 12345678") * 8 + 1];
149 
150 		memset(str, ' ', sizeof(str));
151 		str[sizeof(str) - 1] = '\0';
152 
153 		for (p = first, i = 0; i < 8 && p < top; i++, p += 4) {
154 			if (p >= bottom && p < top) {
155 				unsigned long val;
156 				if (!get_kernel_nofault(val, (unsigned long *)p))
157 					sprintf(str + i * 9, " %08lx", val);
158 				else
159 					sprintf(str + i * 9, " ????????");
160 			}
161 		}
162 		printk("%s%04lx:%s\n", lvl, first & 0xffff, str);
163 	}
164 }
165 
166 static void dump_instr(const char *lvl, struct pt_regs *regs)
167 {
168 	unsigned long addr = instruction_pointer(regs);
169 	const int thumb = thumb_mode(regs);
170 	const int width = thumb ? 4 : 8;
171 	char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
172 	int i;
173 
174 	/*
175 	 * Note that we now dump the code first, just in case the backtrace
176 	 * kills us.
177 	 */
178 
179 	for (i = -4; i < 1 + !!thumb; i++) {
180 		unsigned int val, bad;
181 
182 		if (thumb) {
183 			u16 tmp;
184 
185 			if (user_mode(regs))
186 				bad = get_user(tmp, &((u16 __user *)addr)[i]);
187 			else
188 				bad = get_kernel_nofault(tmp, &((u16 *)addr)[i]);
189 
190 			val = __mem_to_opcode_thumb16(tmp);
191 		} else {
192 			if (user_mode(regs))
193 				bad = get_user(val, &((u32 __user *)addr)[i]);
194 			else
195 				bad = get_kernel_nofault(val, &((u32 *)addr)[i]);
196 
197 			val = __mem_to_opcode_arm(val);
198 		}
199 
200 		if (!bad)
201 			p += sprintf(p, i == 0 ? "(%0*x) " : "%0*x ",
202 					width, val);
203 		else {
204 			p += sprintf(p, "bad PC value");
205 			break;
206 		}
207 	}
208 	printk("%sCode: %s\n", lvl, str);
209 }
210 
211 #ifdef CONFIG_ARM_UNWIND
212 void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
213 		    const char *loglvl)
214 {
215 	unwind_backtrace(regs, tsk, loglvl);
216 }
217 #else
218 void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
219 		    const char *loglvl)
220 {
221 	unsigned int fp, mode;
222 	int ok = 1;
223 
224 	printk("%sCall trace: ", loglvl);
225 
226 	if (!tsk)
227 		tsk = current;
228 
229 	if (regs) {
230 		fp = frame_pointer(regs);
231 		mode = processor_mode(regs);
232 	} else if (tsk != current) {
233 		fp = thread_saved_fp(tsk);
234 		mode = 0x10;
235 	} else {
236 		asm("mov %0, fp" : "=r" (fp) : : "cc");
237 		mode = 0x10;
238 	}
239 
240 	if (!fp) {
241 		pr_cont("no frame pointer");
242 		ok = 0;
243 	} else if (verify_stack(fp)) {
244 		pr_cont("invalid frame pointer 0x%08x", fp);
245 		ok = 0;
246 	} else if (fp < (unsigned long)end_of_stack(tsk))
247 		pr_cont("frame pointer underflow");
248 	pr_cont("\n");
249 
250 	if (ok)
251 		c_backtrace(fp, mode, loglvl);
252 }
253 #endif
254 
255 void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
256 {
257 	dump_backtrace(NULL, tsk, loglvl);
258 	barrier();
259 }
260 
261 #ifdef CONFIG_PREEMPT
262 #define S_PREEMPT " PREEMPT"
263 #elif defined(CONFIG_PREEMPT_RT)
264 #define S_PREEMPT " PREEMPT_RT"
265 #else
266 #define S_PREEMPT ""
267 #endif
268 #ifdef CONFIG_SMP
269 #define S_SMP " SMP"
270 #else
271 #define S_SMP ""
272 #endif
273 #ifdef CONFIG_THUMB2_KERNEL
274 #define S_ISA " THUMB2"
275 #else
276 #define S_ISA " ARM"
277 #endif
278 
279 static int __die(const char *str, int err, struct pt_regs *regs)
280 {
281 	struct task_struct *tsk = current;
282 	static int die_counter;
283 	int ret;
284 
285 	pr_emerg("Internal error: %s: %x [#%d]" S_PREEMPT S_SMP S_ISA "\n",
286 	         str, err, ++die_counter);
287 
288 	/* trap and error numbers are mostly meaningless on ARM */
289 	ret = notify_die(DIE_OOPS, str, regs, err, tsk->thread.trap_no, SIGSEGV);
290 	if (ret == NOTIFY_STOP)
291 		return 1;
292 
293 	print_modules();
294 	__show_regs(regs);
295 	__show_regs_alloc_free(regs);
296 	pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n",
297 		 TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), end_of_stack(tsk));
298 
299 	if (!user_mode(regs) || in_interrupt()) {
300 		dump_mem(KERN_EMERG, "Stack: ", regs->ARM_sp,
301 			 ALIGN(regs->ARM_sp - THREAD_SIZE, THREAD_ALIGN)
302 			 + THREAD_SIZE);
303 		dump_backtrace(regs, tsk, KERN_EMERG);
304 		dump_instr(KERN_EMERG, regs);
305 	}
306 
307 	return 0;
308 }
309 
310 static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
311 static int die_owner = -1;
312 static unsigned int die_nest_count;
313 
314 static unsigned long oops_begin(void)
315 {
316 	int cpu;
317 	unsigned long flags;
318 
319 	oops_enter();
320 
321 	/* racy, but better than risking deadlock. */
322 	raw_local_irq_save(flags);
323 	cpu = smp_processor_id();
324 	if (!arch_spin_trylock(&die_lock)) {
325 		if (cpu == die_owner)
326 			/* nested oops. should stop eventually */;
327 		else
328 			arch_spin_lock(&die_lock);
329 	}
330 	die_nest_count++;
331 	die_owner = cpu;
332 	console_verbose();
333 	bust_spinlocks(1);
334 	return flags;
335 }
336 
337 static void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
338 {
339 	if (regs && kexec_should_crash(current))
340 		crash_kexec(regs);
341 
342 	bust_spinlocks(0);
343 	die_owner = -1;
344 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
345 	die_nest_count--;
346 	if (!die_nest_count)
347 		/* Nest count reaches zero, release the lock. */
348 		arch_spin_unlock(&die_lock);
349 	raw_local_irq_restore(flags);
350 	oops_exit();
351 
352 	if (in_interrupt())
353 		panic("Fatal exception in interrupt");
354 	if (panic_on_oops)
355 		panic("Fatal exception");
356 	if (signr)
357 		make_task_dead(signr);
358 }
359 
360 /*
361  * This function is protected against re-entrancy.
362  */
363 void die(const char *str, struct pt_regs *regs, int err)
364 {
365 	enum bug_trap_type bug_type = BUG_TRAP_TYPE_NONE;
366 	unsigned long flags = oops_begin();
367 	int sig = SIGSEGV;
368 
369 	if (!user_mode(regs))
370 		bug_type = report_bug(regs->ARM_pc, regs);
371 	if (bug_type != BUG_TRAP_TYPE_NONE)
372 		str = "Oops - BUG";
373 
374 	if (__die(str, err, regs))
375 		sig = 0;
376 
377 	oops_end(flags, regs, sig);
378 }
379 
380 void arm_notify_die(const char *str, struct pt_regs *regs,
381 		int signo, int si_code, void __user *addr,
382 		unsigned long err, unsigned long trap)
383 {
384 	if (user_mode(regs)) {
385 		current->thread.error_code = err;
386 		current->thread.trap_no = trap;
387 
388 		force_sig_fault(signo, si_code, addr);
389 	} else {
390 		die(str, regs, err);
391 	}
392 }
393 
394 #ifdef CONFIG_GENERIC_BUG
395 
396 int is_valid_bugaddr(unsigned long pc)
397 {
398 #ifdef CONFIG_THUMB2_KERNEL
399 	u16 bkpt;
400 	u16 insn = __opcode_to_mem_thumb16(BUG_INSTR_VALUE);
401 #else
402 	u32 bkpt;
403 	u32 insn = __opcode_to_mem_arm(BUG_INSTR_VALUE);
404 #endif
405 
406 	if (get_kernel_nofault(bkpt, (void *)pc))
407 		return 0;
408 
409 	return bkpt == insn;
410 }
411 
412 #endif
413 
414 static LIST_HEAD(undef_hook);
415 static DEFINE_RAW_SPINLOCK(undef_lock);
416 
417 void register_undef_hook(struct undef_hook *hook)
418 {
419 	unsigned long flags;
420 
421 	raw_spin_lock_irqsave(&undef_lock, flags);
422 	list_add(&hook->node, &undef_hook);
423 	raw_spin_unlock_irqrestore(&undef_lock, flags);
424 }
425 
426 void unregister_undef_hook(struct undef_hook *hook)
427 {
428 	unsigned long flags;
429 
430 	raw_spin_lock_irqsave(&undef_lock, flags);
431 	list_del(&hook->node);
432 	raw_spin_unlock_irqrestore(&undef_lock, flags);
433 }
434 
435 static nokprobe_inline
436 int call_undef_hook(struct pt_regs *regs, unsigned int instr)
437 {
438 	struct undef_hook *hook;
439 	unsigned long flags;
440 	int (*fn)(struct pt_regs *regs, unsigned int instr) = NULL;
441 
442 	raw_spin_lock_irqsave(&undef_lock, flags);
443 	list_for_each_entry(hook, &undef_hook, node)
444 		if ((instr & hook->instr_mask) == hook->instr_val &&
445 		    (regs->ARM_cpsr & hook->cpsr_mask) == hook->cpsr_val)
446 			fn = hook->fn;
447 	raw_spin_unlock_irqrestore(&undef_lock, flags);
448 
449 	return fn ? fn(regs, instr) : 1;
450 }
451 
452 asmlinkage void do_undefinstr(struct pt_regs *regs)
453 {
454 	unsigned int instr;
455 	void __user *pc;
456 
457 	pc = (void __user *)instruction_pointer(regs);
458 
459 	if (processor_mode(regs) == SVC_MODE) {
460 #ifdef CONFIG_THUMB2_KERNEL
461 		if (thumb_mode(regs)) {
462 			instr = __mem_to_opcode_thumb16(((u16 *)pc)[0]);
463 			if (is_wide_instruction(instr)) {
464 				u16 inst2;
465 				inst2 = __mem_to_opcode_thumb16(((u16 *)pc)[1]);
466 				instr = __opcode_thumb32_compose(instr, inst2);
467 			}
468 		} else
469 #endif
470 			instr = __mem_to_opcode_arm(*(u32 *) pc);
471 	} else if (thumb_mode(regs)) {
472 		if (get_user(instr, (u16 __user *)pc))
473 			goto die_sig;
474 		instr = __mem_to_opcode_thumb16(instr);
475 		if (is_wide_instruction(instr)) {
476 			unsigned int instr2;
477 			if (get_user(instr2, (u16 __user *)pc+1))
478 				goto die_sig;
479 			instr2 = __mem_to_opcode_thumb16(instr2);
480 			instr = __opcode_thumb32_compose(instr, instr2);
481 		}
482 	} else {
483 		if (get_user(instr, (u32 __user *)pc))
484 			goto die_sig;
485 		instr = __mem_to_opcode_arm(instr);
486 	}
487 
488 	if (call_undef_hook(regs, instr) == 0)
489 		return;
490 
491 die_sig:
492 #ifdef CONFIG_DEBUG_USER
493 	if (user_debug & UDBG_UNDEFINED) {
494 		pr_info("%s (%d): undefined instruction: pc=%px\n",
495 			current->comm, task_pid_nr(current), pc);
496 		__show_regs(regs);
497 		dump_instr(KERN_INFO, regs);
498 	}
499 #endif
500 	arm_notify_die("Oops - undefined instruction", regs,
501 		       SIGILL, ILL_ILLOPC, pc, 0, 6);
502 }
503 NOKPROBE_SYMBOL(do_undefinstr)
504 
505 /*
506  * Handle FIQ similarly to NMI on x86 systems.
507  *
508  * The runtime environment for NMIs is extremely restrictive
509  * (NMIs can pre-empt critical sections meaning almost all locking is
510  * forbidden) meaning this default FIQ handling must only be used in
511  * circumstances where non-maskability improves robustness, such as
512  * watchdog or debug logic.
513  *
514  * This handler is not appropriate for general purpose use in drivers
515  * platform code and can be overrideen using set_fiq_handler.
516  */
517 asmlinkage void __exception_irq_entry handle_fiq_as_nmi(struct pt_regs *regs)
518 {
519 	struct pt_regs *old_regs = set_irq_regs(regs);
520 
521 	nmi_enter();
522 
523 	/* nop. FIQ handlers for special arch/arm features can be added here. */
524 
525 	nmi_exit();
526 
527 	set_irq_regs(old_regs);
528 }
529 
530 /*
531  * bad_mode handles the impossible case in the vectors.  If you see one of
532  * these, then it's extremely serious, and could mean you have buggy hardware.
533  * It never returns, and never tries to sync.  We hope that we can at least
534  * dump out some state information...
535  */
536 asmlinkage void bad_mode(struct pt_regs *regs, int reason)
537 {
538 	console_verbose();
539 
540 	pr_crit("Bad mode in %s handler detected\n", handler[reason]);
541 
542 	die("Oops - bad mode", regs, 0);
543 	local_irq_disable();
544 	panic("bad mode");
545 }
546 
547 static int bad_syscall(int n, struct pt_regs *regs)
548 {
549 	if ((current->personality & PER_MASK) != PER_LINUX) {
550 		send_sig(SIGSEGV, current, 1);
551 		return regs->ARM_r0;
552 	}
553 
554 #ifdef CONFIG_DEBUG_USER
555 	if (user_debug & UDBG_SYSCALL) {
556 		pr_err("[%d] %s: obsolete system call %08x.\n",
557 			task_pid_nr(current), current->comm, n);
558 		dump_instr(KERN_ERR, regs);
559 	}
560 #endif
561 
562 	arm_notify_die("Oops - bad syscall", regs, SIGILL, ILL_ILLTRP,
563 		       (void __user *)instruction_pointer(regs) -
564 			 (thumb_mode(regs) ? 2 : 4),
565 		       n, 0);
566 
567 	return regs->ARM_r0;
568 }
569 
570 static inline int
571 __do_cache_op(unsigned long start, unsigned long end)
572 {
573 	unsigned int ua_flags;
574 	int ret;
575 
576 	do {
577 		unsigned long chunk = min(PAGE_SIZE, end - start);
578 
579 		if (fatal_signal_pending(current))
580 			return 0;
581 
582 		ua_flags = uaccess_save_and_enable();
583 		ret = flush_icache_user_range(start, start + chunk);
584 		uaccess_restore(ua_flags);
585 		if (ret)
586 			return ret;
587 
588 		cond_resched();
589 		start += chunk;
590 	} while (start < end);
591 
592 	return 0;
593 }
594 
595 static inline int
596 do_cache_op(unsigned long start, unsigned long end, int flags)
597 {
598 	if (end < start || flags)
599 		return -EINVAL;
600 
601 	if (!access_ok((void __user *)start, end - start))
602 		return -EFAULT;
603 
604 	return __do_cache_op(start, end);
605 }
606 
607 /*
608  * Handle all unrecognised system calls.
609  *  0x9f0000 - 0x9fffff are some more esoteric system calls
610  */
611 #define NR(x) ((__ARM_NR_##x) - __ARM_NR_BASE)
612 asmlinkage int arm_syscall(int no, struct pt_regs *regs)
613 {
614 	if ((no >> 16) != (__ARM_NR_BASE>> 16))
615 		return bad_syscall(no, regs);
616 
617 	switch (no & 0xffff) {
618 	case 0: /* branch through 0 */
619 		arm_notify_die("branch through zero", regs,
620 			       SIGSEGV, SEGV_MAPERR, NULL, 0, 0);
621 		return 0;
622 
623 	case NR(breakpoint): /* SWI BREAK_POINT */
624 		regs->ARM_pc -= thumb_mode(regs) ? 2 : 4;
625 		ptrace_break(regs);
626 		return regs->ARM_r0;
627 
628 	/*
629 	 * Flush a region from virtual address 'r0' to virtual address 'r1'
630 	 * _exclusive_.  There is no alignment requirement on either address;
631 	 * user space does not need to know the hardware cache layout.
632 	 *
633 	 * r2 contains flags.  It should ALWAYS be passed as ZERO until it
634 	 * is defined to be something else.  For now we ignore it, but may
635 	 * the fires of hell burn in your belly if you break this rule. ;)
636 	 *
637 	 * (at a later date, we may want to allow this call to not flush
638 	 * various aspects of the cache.  Passing '0' will guarantee that
639 	 * everything necessary gets flushed to maintain consistency in
640 	 * the specified region).
641 	 */
642 	case NR(cacheflush):
643 		return do_cache_op(regs->ARM_r0, regs->ARM_r1, regs->ARM_r2);
644 
645 	case NR(usr26):
646 		if (!(elf_hwcap & HWCAP_26BIT))
647 			break;
648 		regs->ARM_cpsr &= ~MODE32_BIT;
649 		return regs->ARM_r0;
650 
651 	case NR(usr32):
652 		if (!(elf_hwcap & HWCAP_26BIT))
653 			break;
654 		regs->ARM_cpsr |= MODE32_BIT;
655 		return regs->ARM_r0;
656 
657 	case NR(set_tls):
658 		set_tls(regs->ARM_r0);
659 		return 0;
660 
661 	case NR(get_tls):
662 		return current_thread_info()->tp_value[0];
663 
664 	default:
665 		/* Calls 9f00xx..9f07ff are defined to return -ENOSYS
666 		   if not implemented, rather than raising SIGILL.  This
667 		   way the calling program can gracefully determine whether
668 		   a feature is supported.  */
669 		if ((no & 0xffff) <= 0x7ff)
670 			return -ENOSYS;
671 		break;
672 	}
673 #ifdef CONFIG_DEBUG_USER
674 	/*
675 	 * experience shows that these seem to indicate that
676 	 * something catastrophic has happened
677 	 */
678 	if (user_debug & UDBG_SYSCALL) {
679 		pr_err("[%d] %s: arm syscall %d\n",
680 		       task_pid_nr(current), current->comm, no);
681 		dump_instr(KERN_ERR, regs);
682 		if (user_mode(regs)) {
683 			__show_regs(regs);
684 			c_backtrace(frame_pointer(regs), processor_mode(regs), KERN_ERR);
685 		}
686 	}
687 #endif
688 	arm_notify_die("Oops - bad syscall(2)", regs, SIGILL, ILL_ILLTRP,
689 		       (void __user *)instruction_pointer(regs) -
690 			 (thumb_mode(regs) ? 2 : 4),
691 		       no, 0);
692 	return 0;
693 }
694 
695 #ifdef CONFIG_TLS_REG_EMUL
696 
697 /*
698  * We might be running on an ARMv6+ processor which should have the TLS
699  * register but for some reason we can't use it, or maybe an SMP system
700  * using a pre-ARMv6 processor (there are apparently a few prototypes like
701  * that in existence) and therefore access to that register must be
702  * emulated.
703  */
704 
705 static int get_tp_trap(struct pt_regs *regs, unsigned int instr)
706 {
707 	int reg = (instr >> 12) & 15;
708 	if (reg == 15)
709 		return 1;
710 	regs->uregs[reg] = current_thread_info()->tp_value[0];
711 	regs->ARM_pc += 4;
712 	return 0;
713 }
714 
715 static struct undef_hook arm_mrc_hook = {
716 	.instr_mask	= 0x0fff0fff,
717 	.instr_val	= 0x0e1d0f70,
718 	.cpsr_mask	= PSR_T_BIT,
719 	.cpsr_val	= 0,
720 	.fn		= get_tp_trap,
721 };
722 
723 static int __init arm_mrc_hook_init(void)
724 {
725 	register_undef_hook(&arm_mrc_hook);
726 	return 0;
727 }
728 
729 late_initcall(arm_mrc_hook_init);
730 
731 #endif
732 
733 /*
734  * A data abort trap was taken, but we did not handle the instruction.
735  * Try to abort the user program, or panic if it was the kernel.
736  */
737 asmlinkage void
738 baddataabort(int code, unsigned long instr, struct pt_regs *regs)
739 {
740 	unsigned long addr = instruction_pointer(regs);
741 
742 #ifdef CONFIG_DEBUG_USER
743 	if (user_debug & UDBG_BADABORT) {
744 		pr_err("8<--- cut here ---\n");
745 		pr_err("[%d] %s: bad data abort: code %d instr 0x%08lx\n",
746 		       task_pid_nr(current), current->comm, code, instr);
747 		dump_instr(KERN_ERR, regs);
748 		show_pte(KERN_ERR, current->mm, addr);
749 	}
750 #endif
751 
752 	arm_notify_die("unknown data abort code", regs,
753 		       SIGILL, ILL_ILLOPC, (void __user *)addr, instr, 0);
754 }
755 
756 void __readwrite_bug(const char *fn)
757 {
758 	pr_err("%s called, but not implemented\n", fn);
759 	BUG();
760 }
761 EXPORT_SYMBOL(__readwrite_bug);
762 
763 #ifdef CONFIG_MMU
764 void __pte_error(const char *file, int line, pte_t pte)
765 {
766 	pr_err("%s:%d: bad pte %08llx.\n", file, line, (long long)pte_val(pte));
767 }
768 
769 void __pmd_error(const char *file, int line, pmd_t pmd)
770 {
771 	pr_err("%s:%d: bad pmd %08llx.\n", file, line, (long long)pmd_val(pmd));
772 }
773 
774 void __pgd_error(const char *file, int line, pgd_t pgd)
775 {
776 	pr_err("%s:%d: bad pgd %08llx.\n", file, line, (long long)pgd_val(pgd));
777 }
778 #endif
779 
780 asmlinkage void __div0(void)
781 {
782 	pr_err("Division by zero in kernel.\n");
783 	dump_stack();
784 }
785 EXPORT_SYMBOL(__div0);
786 
787 void abort(void)
788 {
789 	BUG();
790 
791 	/* if that doesn't kill us, halt */
792 	panic("Oops failed to kill thread");
793 }
794 
795 #ifdef CONFIG_KUSER_HELPERS
796 static void __init kuser_init(void *vectors)
797 {
798 	extern char __kuser_helper_start[], __kuser_helper_end[];
799 	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
800 
801 	memcpy(vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz);
802 
803 	/*
804 	 * vectors + 0xfe0 = __kuser_get_tls
805 	 * vectors + 0xfe8 = hardware TLS instruction at 0xffff0fe8
806 	 */
807 	if (tls_emu || has_tls_reg)
808 		memcpy(vectors + 0xfe0, vectors + 0xfe8, 4);
809 }
810 #else
811 static inline void __init kuser_init(void *vectors)
812 {
813 }
814 #endif
815 
816 #ifndef CONFIG_CPU_V7M
817 static void copy_from_lma(void *vma, void *lma_start, void *lma_end)
818 {
819 	memcpy(vma, lma_start, lma_end - lma_start);
820 }
821 
822 static void flush_vectors(void *vma, size_t offset, size_t size)
823 {
824 	unsigned long start = (unsigned long)vma + offset;
825 	unsigned long end = start + size;
826 
827 	flush_icache_range(start, end);
828 }
829 
830 #ifdef CONFIG_HARDEN_BRANCH_HISTORY
831 int spectre_bhb_update_vectors(unsigned int method)
832 {
833 	extern char __vectors_bhb_bpiall_start[], __vectors_bhb_bpiall_end[];
834 	extern char __vectors_bhb_loop8_start[], __vectors_bhb_loop8_end[];
835 	void *vec_start, *vec_end;
836 
837 	if (system_state >= SYSTEM_FREEING_INITMEM) {
838 		pr_err("CPU%u: Spectre BHB workaround too late - system vulnerable\n",
839 		       smp_processor_id());
840 		return SPECTRE_VULNERABLE;
841 	}
842 
843 	switch (method) {
844 	case SPECTRE_V2_METHOD_LOOP8:
845 		vec_start = __vectors_bhb_loop8_start;
846 		vec_end = __vectors_bhb_loop8_end;
847 		break;
848 
849 	case SPECTRE_V2_METHOD_BPIALL:
850 		vec_start = __vectors_bhb_bpiall_start;
851 		vec_end = __vectors_bhb_bpiall_end;
852 		break;
853 
854 	default:
855 		pr_err("CPU%u: unknown Spectre BHB state %d\n",
856 		       smp_processor_id(), method);
857 		return SPECTRE_VULNERABLE;
858 	}
859 
860 	copy_from_lma(vectors_page, vec_start, vec_end);
861 	flush_vectors(vectors_page, 0, vec_end - vec_start);
862 
863 	return SPECTRE_MITIGATED;
864 }
865 #endif
866 
867 void __init early_trap_init(void *vectors_base)
868 {
869 	extern char __stubs_start[], __stubs_end[];
870 	extern char __vectors_start[], __vectors_end[];
871 	unsigned i;
872 
873 	vectors_page = vectors_base;
874 
875 	/*
876 	 * Poison the vectors page with an undefined instruction.  This
877 	 * instruction is chosen to be undefined for both ARM and Thumb
878 	 * ISAs.  The Thumb version is an undefined instruction with a
879 	 * branch back to the undefined instruction.
880 	 */
881 	for (i = 0; i < PAGE_SIZE / sizeof(u32); i++)
882 		((u32 *)vectors_base)[i] = 0xe7fddef1;
883 
884 	/*
885 	 * Copy the vectors, stubs and kuser helpers (in entry-armv.S)
886 	 * into the vector page, mapped at 0xffff0000, and ensure these
887 	 * are visible to the instruction stream.
888 	 */
889 	copy_from_lma(vectors_base, __vectors_start, __vectors_end);
890 	copy_from_lma(vectors_base + 0x1000, __stubs_start, __stubs_end);
891 
892 	kuser_init(vectors_base);
893 
894 	flush_vectors(vectors_base, 0, PAGE_SIZE * 2);
895 }
896 #else /* ifndef CONFIG_CPU_V7M */
897 void __init early_trap_init(void *vectors_base)
898 {
899 	/*
900 	 * on V7-M there is no need to copy the vector table to a dedicated
901 	 * memory area. The address is configurable and so a table in the kernel
902 	 * image can be used.
903 	 */
904 }
905 #endif
906 
907 #ifdef CONFIG_VMAP_STACK
908 
909 DECLARE_PER_CPU(u8 *, irq_stack_ptr);
910 
911 asmlinkage DEFINE_PER_CPU(u8 *, overflow_stack_ptr);
912 
913 static int __init allocate_overflow_stacks(void)
914 {
915 	u8 *stack;
916 	int cpu;
917 
918 	for_each_possible_cpu(cpu) {
919 		stack = (u8 *)__get_free_page(GFP_KERNEL);
920 		if (WARN_ON(!stack))
921 			return -ENOMEM;
922 		per_cpu(overflow_stack_ptr, cpu) = &stack[OVERFLOW_STACK_SIZE];
923 	}
924 	return 0;
925 }
926 early_initcall(allocate_overflow_stacks);
927 
928 asmlinkage void handle_bad_stack(struct pt_regs *regs)
929 {
930 	unsigned long tsk_stk = (unsigned long)current->stack;
931 #ifdef CONFIG_IRQSTACKS
932 	unsigned long irq_stk = (unsigned long)raw_cpu_read(irq_stack_ptr);
933 #endif
934 	unsigned long ovf_stk = (unsigned long)raw_cpu_read(overflow_stack_ptr);
935 
936 	console_verbose();
937 	pr_emerg("Insufficient stack space to handle exception!");
938 
939 	pr_emerg("Task stack:     [0x%08lx..0x%08lx]\n",
940 		 tsk_stk, tsk_stk + THREAD_SIZE);
941 #ifdef CONFIG_IRQSTACKS
942 	pr_emerg("IRQ stack:      [0x%08lx..0x%08lx]\n",
943 		 irq_stk - THREAD_SIZE, irq_stk);
944 #endif
945 	pr_emerg("Overflow stack: [0x%08lx..0x%08lx]\n",
946 		 ovf_stk - OVERFLOW_STACK_SIZE, ovf_stk);
947 
948 	die("kernel stack overflow", regs, 0);
949 }
950 
951 #ifndef CONFIG_ARM_LPAE
952 /*
953  * Normally, we rely on the logic in do_translation_fault() to update stale PMD
954  * entries covering the vmalloc space in a task's page tables when it first
955  * accesses the region in question. Unfortunately, this is not sufficient when
956  * the task stack resides in the vmalloc region, as do_translation_fault() is a
957  * C function that needs a stack to run.
958  *
959  * So we need to ensure that these PMD entries are up to date *before* the MM
960  * switch. As we already have some logic in the MM switch path that takes care
961  * of this, let's trigger it by bumping the counter every time the core vmalloc
962  * code modifies a PMD entry in the vmalloc region. Use release semantics on
963  * the store so that other CPUs observing the counter's new value are
964  * guaranteed to see the updated page table entries as well.
965  */
966 void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
967 {
968 	if (start < VMALLOC_END && end > VMALLOC_START)
969 		atomic_inc_return_release(&init_mm.context.vmalloc_seq);
970 }
971 #endif
972 #endif
973