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 
30 #include <linux/atomic.h>
31 #include <asm/cacheflush.h>
32 #include <asm/exception.h>
33 #include <asm/spectre.h>
34 #include <asm/unistd.h>
35 #include <asm/traps.h>
36 #include <asm/ptrace.h>
37 #include <asm/unwind.h>
38 #include <asm/tls.h>
39 #include <asm/stacktrace.h>
40 #include <asm/system_misc.h>
41 #include <asm/opcodes.h>
42 
43 
44 static const char *handler[]= {
45 	"prefetch abort",
46 	"data abort",
47 	"address exception",
48 	"interrupt",
49 	"undefined instruction",
50 };
51 
52 void *vectors_page;
53 
54 #ifdef CONFIG_DEBUG_USER
55 unsigned int user_debug;
56 
user_debug_setup(char * str)57 static int __init user_debug_setup(char *str)
58 {
59 	get_option(&str, &user_debug);
60 	return 1;
61 }
62 __setup("user_debug=", user_debug_setup);
63 #endif
64 
dump_backtrace_entry(unsigned long where,unsigned long from,unsigned long frame,const char * loglvl)65 void dump_backtrace_entry(unsigned long where, unsigned long from,
66 			  unsigned long frame, const char *loglvl)
67 {
68 	unsigned long end = frame + 4 + sizeof(struct pt_regs);
69 
70 	if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER) &&
71 	    IS_ENABLED(CONFIG_CC_IS_GCC) &&
72 	    end > ALIGN(frame, THREAD_SIZE)) {
73 		/*
74 		 * If we are walking past the end of the stack, it may be due
75 		 * to the fact that we are on an IRQ or overflow stack. In this
76 		 * case, we can load the address of the other stack from the
77 		 * frame record.
78 		 */
79 		frame = ((unsigned long *)frame)[-2] - 4;
80 		end = frame + 4 + sizeof(struct pt_regs);
81 	}
82 
83 #ifndef CONFIG_KALLSYMS
84 	printk("%sFunction entered at [<%08lx>] from [<%08lx>]\n",
85 		loglvl, where, from);
86 #elif defined CONFIG_BACKTRACE_VERBOSE
87 	printk("%s[<%08lx>] (%ps) from [<%08lx>] (%pS)\n",
88 		loglvl, where, (void *)where, from, (void *)from);
89 #else
90 	printk("%s %ps from %pS\n", loglvl, (void *)where, (void *)from);
91 #endif
92 
93 	if (in_entry_text(from) && end <= ALIGN(frame, THREAD_SIZE))
94 		dump_mem(loglvl, "Exception stack", frame + 4, end);
95 }
96 
dump_backtrace_stm(u32 * stack,u32 instruction,const char * loglvl)97 void dump_backtrace_stm(u32 *stack, u32 instruction, const char *loglvl)
98 {
99 	char str[80], *p;
100 	unsigned int x;
101 	int reg;
102 
103 	for (reg = 10, x = 0, p = str; reg >= 0; reg--) {
104 		if (instruction & BIT(reg)) {
105 			p += sprintf(p, " r%d:%08x", reg, *stack--);
106 			if (++x == 6) {
107 				x = 0;
108 				p = str;
109 				printk("%s%s\n", loglvl, str);
110 			}
111 		}
112 	}
113 	if (p != str)
114 		printk("%s%s\n", loglvl, str);
115 }
116 
117 #ifndef CONFIG_ARM_UNWIND
118 /*
119  * Stack pointers should always be within the kernels view of
120  * physical memory.  If it is not there, then we can't dump
121  * out any information relating to the stack.
122  */
verify_stack(unsigned long sp)123 static int verify_stack(unsigned long sp)
124 {
125 	if (sp < PAGE_OFFSET ||
126 	    (!IS_ENABLED(CONFIG_VMAP_STACK) &&
127 	     sp > (unsigned long)high_memory && high_memory != NULL))
128 		return -EFAULT;
129 
130 	return 0;
131 }
132 #endif
133 
134 /*
135  * Dump out the contents of some memory nicely...
136  */
dump_mem(const char * lvl,const char * str,unsigned long bottom,unsigned long top)137 void dump_mem(const char *lvl, const char *str, unsigned long bottom,
138 	      unsigned long top)
139 {
140 	unsigned long first;
141 	int i;
142 
143 	printk("%s%s(0x%08lx to 0x%08lx)\n", lvl, str, bottom, top);
144 
145 	for (first = bottom & ~31; first < top; first += 32) {
146 		unsigned long p;
147 		char str[sizeof(" 12345678") * 8 + 1];
148 
149 		memset(str, ' ', sizeof(str));
150 		str[sizeof(str) - 1] = '\0';
151 
152 		for (p = first, i = 0; i < 8 && p < top; i++, p += 4) {
153 			if (p >= bottom && p < top) {
154 				unsigned long val;
155 				if (!get_kernel_nofault(val, (unsigned long *)p))
156 					sprintf(str + i * 9, " %08lx", val);
157 				else
158 					sprintf(str + i * 9, " ????????");
159 			}
160 		}
161 		printk("%s%04lx:%s\n", lvl, first & 0xffff, str);
162 	}
163 }
164 
dump_instr(const char * lvl,struct pt_regs * regs)165 static void dump_instr(const char *lvl, struct pt_regs *regs)
166 {
167 	unsigned long addr = instruction_pointer(regs);
168 	const int thumb = thumb_mode(regs);
169 	const int width = thumb ? 4 : 8;
170 	char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
171 	int i;
172 
173 	/*
174 	 * Note that we now dump the code first, just in case the backtrace
175 	 * kills us.
176 	 */
177 
178 	for (i = -4; i < 1 + !!thumb; i++) {
179 		unsigned int val, bad;
180 
181 		if (!user_mode(regs)) {
182 			if (thumb) {
183 				u16 val16;
184 				bad = get_kernel_nofault(val16, &((u16 *)addr)[i]);
185 				val = val16;
186 			} else {
187 				bad = get_kernel_nofault(val, &((u32 *)addr)[i]);
188 			}
189 		} else {
190 			if (thumb)
191 				bad = get_user(val, &((u16 *)addr)[i]);
192 			else
193 				bad = get_user(val, &((u32 *)addr)[i]);
194 		}
195 
196 		if (!bad)
197 			p += sprintf(p, i == 0 ? "(%0*x) " : "%0*x ",
198 					width, val);
199 		else {
200 			p += sprintf(p, "bad PC value");
201 			break;
202 		}
203 	}
204 	printk("%sCode: %s\n", lvl, str);
205 }
206 
207 #ifdef CONFIG_ARM_UNWIND
dump_backtrace(struct pt_regs * regs,struct task_struct * tsk,const char * loglvl)208 static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
209 				  const char *loglvl)
210 {
211 	unwind_backtrace(regs, tsk, loglvl);
212 }
213 #else
dump_backtrace(struct pt_regs * regs,struct task_struct * tsk,const char * loglvl)214 static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
215 			   const char *loglvl)
216 {
217 	unsigned int fp, mode;
218 	int ok = 1;
219 
220 	printk("%sBacktrace: ", loglvl);
221 
222 	if (!tsk)
223 		tsk = current;
224 
225 	if (regs) {
226 		fp = frame_pointer(regs);
227 		mode = processor_mode(regs);
228 	} else if (tsk != current) {
229 		fp = thread_saved_fp(tsk);
230 		mode = 0x10;
231 	} else {
232 		asm("mov %0, fp" : "=r" (fp) : : "cc");
233 		mode = 0x10;
234 	}
235 
236 	if (!fp) {
237 		pr_cont("no frame pointer");
238 		ok = 0;
239 	} else if (verify_stack(fp)) {
240 		pr_cont("invalid frame pointer 0x%08x", fp);
241 		ok = 0;
242 	} else if (fp < (unsigned long)end_of_stack(tsk))
243 		pr_cont("frame pointer underflow");
244 	pr_cont("\n");
245 
246 	if (ok)
247 		c_backtrace(fp, mode, loglvl);
248 }
249 #endif
250 
show_stack(struct task_struct * tsk,unsigned long * sp,const char * loglvl)251 void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
252 {
253 	dump_backtrace(NULL, tsk, loglvl);
254 	barrier();
255 }
256 
257 #ifdef CONFIG_PREEMPT
258 #define S_PREEMPT " PREEMPT"
259 #elif defined(CONFIG_PREEMPT_RT)
260 #define S_PREEMPT " PREEMPT_RT"
261 #else
262 #define S_PREEMPT ""
263 #endif
264 #ifdef CONFIG_SMP
265 #define S_SMP " SMP"
266 #else
267 #define S_SMP ""
268 #endif
269 #ifdef CONFIG_THUMB2_KERNEL
270 #define S_ISA " THUMB2"
271 #else
272 #define S_ISA " ARM"
273 #endif
274 
__die(const char * str,int err,struct pt_regs * regs)275 static int __die(const char *str, int err, struct pt_regs *regs)
276 {
277 	struct task_struct *tsk = current;
278 	static int die_counter;
279 	int ret;
280 
281 	pr_emerg("Internal error: %s: %x [#%d]" S_PREEMPT S_SMP S_ISA "\n",
282 	         str, err, ++die_counter);
283 
284 	/* trap and error numbers are mostly meaningless on ARM */
285 	ret = notify_die(DIE_OOPS, str, regs, err, tsk->thread.trap_no, SIGSEGV);
286 	if (ret == NOTIFY_STOP)
287 		return 1;
288 
289 	print_modules();
290 	__show_regs(regs);
291 	__show_regs_alloc_free(regs);
292 	pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n",
293 		 TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), end_of_stack(tsk));
294 
295 	if (!user_mode(regs) || in_interrupt()) {
296 		dump_mem(KERN_EMERG, "Stack: ", regs->ARM_sp,
297 			 ALIGN(regs->ARM_sp - THREAD_SIZE, THREAD_ALIGN)
298 			 + THREAD_SIZE);
299 		dump_backtrace(regs, tsk, KERN_EMERG);
300 		dump_instr(KERN_EMERG, regs);
301 	}
302 
303 	return 0;
304 }
305 
306 static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
307 static int die_owner = -1;
308 static unsigned int die_nest_count;
309 
oops_begin(void)310 static unsigned long oops_begin(void)
311 {
312 	int cpu;
313 	unsigned long flags;
314 
315 	oops_enter();
316 
317 	/* racy, but better than risking deadlock. */
318 	raw_local_irq_save(flags);
319 	cpu = smp_processor_id();
320 	if (!arch_spin_trylock(&die_lock)) {
321 		if (cpu == die_owner)
322 			/* nested oops. should stop eventually */;
323 		else
324 			arch_spin_lock(&die_lock);
325 	}
326 	die_nest_count++;
327 	die_owner = cpu;
328 	console_verbose();
329 	bust_spinlocks(1);
330 	return flags;
331 }
332 
oops_end(unsigned long flags,struct pt_regs * regs,int signr)333 static void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
334 {
335 	if (regs && kexec_should_crash(current))
336 		crash_kexec(regs);
337 
338 	bust_spinlocks(0);
339 	die_owner = -1;
340 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
341 	die_nest_count--;
342 	if (!die_nest_count)
343 		/* Nest count reaches zero, release the lock. */
344 		arch_spin_unlock(&die_lock);
345 	raw_local_irq_restore(flags);
346 	oops_exit();
347 
348 	if (in_interrupt())
349 		panic("Fatal exception in interrupt");
350 	if (panic_on_oops)
351 		panic("Fatal exception");
352 	if (signr)
353 		make_task_dead(signr);
354 }
355 
356 /*
357  * This function is protected against re-entrancy.
358  */
die(const char * str,struct pt_regs * regs,int err)359 void die(const char *str, struct pt_regs *regs, int err)
360 {
361 	enum bug_trap_type bug_type = BUG_TRAP_TYPE_NONE;
362 	unsigned long flags = oops_begin();
363 	int sig = SIGSEGV;
364 
365 	if (!user_mode(regs))
366 		bug_type = report_bug(regs->ARM_pc, regs);
367 	if (bug_type != BUG_TRAP_TYPE_NONE)
368 		str = "Oops - BUG";
369 
370 	if (__die(str, err, regs))
371 		sig = 0;
372 
373 	oops_end(flags, regs, sig);
374 }
375 
arm_notify_die(const char * str,struct pt_regs * regs,int signo,int si_code,void __user * addr,unsigned long err,unsigned long trap)376 void arm_notify_die(const char *str, struct pt_regs *regs,
377 		int signo, int si_code, void __user *addr,
378 		unsigned long err, unsigned long trap)
379 {
380 	if (user_mode(regs)) {
381 		current->thread.error_code = err;
382 		current->thread.trap_no = trap;
383 
384 		force_sig_fault(signo, si_code, addr);
385 	} else {
386 		die(str, regs, err);
387 	}
388 }
389 
390 #ifdef CONFIG_GENERIC_BUG
391 
is_valid_bugaddr(unsigned long pc)392 int is_valid_bugaddr(unsigned long pc)
393 {
394 #ifdef CONFIG_THUMB2_KERNEL
395 	u16 bkpt;
396 	u16 insn = __opcode_to_mem_thumb16(BUG_INSTR_VALUE);
397 #else
398 	u32 bkpt;
399 	u32 insn = __opcode_to_mem_arm(BUG_INSTR_VALUE);
400 #endif
401 
402 	if (get_kernel_nofault(bkpt, (void *)pc))
403 		return 0;
404 
405 	return bkpt == insn;
406 }
407 
408 #endif
409 
410 static LIST_HEAD(undef_hook);
411 static DEFINE_RAW_SPINLOCK(undef_lock);
412 
register_undef_hook(struct undef_hook * hook)413 void register_undef_hook(struct undef_hook *hook)
414 {
415 	unsigned long flags;
416 
417 	raw_spin_lock_irqsave(&undef_lock, flags);
418 	list_add(&hook->node, &undef_hook);
419 	raw_spin_unlock_irqrestore(&undef_lock, flags);
420 }
421 
unregister_undef_hook(struct undef_hook * hook)422 void unregister_undef_hook(struct undef_hook *hook)
423 {
424 	unsigned long flags;
425 
426 	raw_spin_lock_irqsave(&undef_lock, flags);
427 	list_del(&hook->node);
428 	raw_spin_unlock_irqrestore(&undef_lock, flags);
429 }
430 
431 static nokprobe_inline
call_undef_hook(struct pt_regs * regs,unsigned int instr)432 int call_undef_hook(struct pt_regs *regs, unsigned int instr)
433 {
434 	struct undef_hook *hook;
435 	unsigned long flags;
436 	int (*fn)(struct pt_regs *regs, unsigned int instr) = NULL;
437 
438 	raw_spin_lock_irqsave(&undef_lock, flags);
439 	list_for_each_entry(hook, &undef_hook, node)
440 		if ((instr & hook->instr_mask) == hook->instr_val &&
441 		    (regs->ARM_cpsr & hook->cpsr_mask) == hook->cpsr_val)
442 			fn = hook->fn;
443 	raw_spin_unlock_irqrestore(&undef_lock, flags);
444 
445 	return fn ? fn(regs, instr) : 1;
446 }
447 
do_undefinstr(struct pt_regs * regs)448 asmlinkage void do_undefinstr(struct pt_regs *regs)
449 {
450 	unsigned int instr;
451 	void __user *pc;
452 
453 	pc = (void __user *)instruction_pointer(regs);
454 
455 	if (processor_mode(regs) == SVC_MODE) {
456 #ifdef CONFIG_THUMB2_KERNEL
457 		if (thumb_mode(regs)) {
458 			instr = __mem_to_opcode_thumb16(((u16 *)pc)[0]);
459 			if (is_wide_instruction(instr)) {
460 				u16 inst2;
461 				inst2 = __mem_to_opcode_thumb16(((u16 *)pc)[1]);
462 				instr = __opcode_thumb32_compose(instr, inst2);
463 			}
464 		} else
465 #endif
466 			instr = __mem_to_opcode_arm(*(u32 *) pc);
467 	} else if (thumb_mode(regs)) {
468 		if (get_user(instr, (u16 __user *)pc))
469 			goto die_sig;
470 		instr = __mem_to_opcode_thumb16(instr);
471 		if (is_wide_instruction(instr)) {
472 			unsigned int instr2;
473 			if (get_user(instr2, (u16 __user *)pc+1))
474 				goto die_sig;
475 			instr2 = __mem_to_opcode_thumb16(instr2);
476 			instr = __opcode_thumb32_compose(instr, instr2);
477 		}
478 	} else {
479 		if (get_user(instr, (u32 __user *)pc))
480 			goto die_sig;
481 		instr = __mem_to_opcode_arm(instr);
482 	}
483 
484 	if (call_undef_hook(regs, instr) == 0)
485 		return;
486 
487 die_sig:
488 #ifdef CONFIG_DEBUG_USER
489 	if (user_debug & UDBG_UNDEFINED) {
490 		pr_info("%s (%d): undefined instruction: pc=%p\n",
491 			current->comm, task_pid_nr(current), pc);
492 		__show_regs(regs);
493 		dump_instr(KERN_INFO, regs);
494 	}
495 #endif
496 	arm_notify_die("Oops - undefined instruction", regs,
497 		       SIGILL, ILL_ILLOPC, pc, 0, 6);
498 }
NOKPROBE_SYMBOL(do_undefinstr)499 NOKPROBE_SYMBOL(do_undefinstr)
500 
501 /*
502  * Handle FIQ similarly to NMI on x86 systems.
503  *
504  * The runtime environment for NMIs is extremely restrictive
505  * (NMIs can pre-empt critical sections meaning almost all locking is
506  * forbidden) meaning this default FIQ handling must only be used in
507  * circumstances where non-maskability improves robustness, such as
508  * watchdog or debug logic.
509  *
510  * This handler is not appropriate for general purpose use in drivers
511  * platform code and can be overrideen using set_fiq_handler.
512  */
513 asmlinkage void __exception_irq_entry handle_fiq_as_nmi(struct pt_regs *regs)
514 {
515 	struct pt_regs *old_regs = set_irq_regs(regs);
516 
517 	nmi_enter();
518 
519 	/* nop. FIQ handlers for special arch/arm features can be added here. */
520 
521 	nmi_exit();
522 
523 	set_irq_regs(old_regs);
524 }
525 
526 /*
527  * bad_mode handles the impossible case in the vectors.  If you see one of
528  * these, then it's extremely serious, and could mean you have buggy hardware.
529  * It never returns, and never tries to sync.  We hope that we can at least
530  * dump out some state information...
531  */
bad_mode(struct pt_regs * regs,int reason)532 asmlinkage void bad_mode(struct pt_regs *regs, int reason)
533 {
534 	console_verbose();
535 
536 	pr_crit("Bad mode in %s handler detected\n", handler[reason]);
537 
538 	die("Oops - bad mode", regs, 0);
539 	local_irq_disable();
540 	panic("bad mode");
541 }
542 
bad_syscall(int n,struct pt_regs * regs)543 static int bad_syscall(int n, struct pt_regs *regs)
544 {
545 	if ((current->personality & PER_MASK) != PER_LINUX) {
546 		send_sig(SIGSEGV, current, 1);
547 		return regs->ARM_r0;
548 	}
549 
550 #ifdef CONFIG_DEBUG_USER
551 	if (user_debug & UDBG_SYSCALL) {
552 		pr_err("[%d] %s: obsolete system call %08x.\n",
553 			task_pid_nr(current), current->comm, n);
554 		dump_instr(KERN_ERR, regs);
555 	}
556 #endif
557 
558 	arm_notify_die("Oops - bad syscall", regs, SIGILL, ILL_ILLTRP,
559 		       (void __user *)instruction_pointer(regs) -
560 			 (thumb_mode(regs) ? 2 : 4),
561 		       n, 0);
562 
563 	return regs->ARM_r0;
564 }
565 
566 static inline int
__do_cache_op(unsigned long start,unsigned long end)567 __do_cache_op(unsigned long start, unsigned long end)
568 {
569 	int ret;
570 
571 	do {
572 		unsigned long chunk = min(PAGE_SIZE, end - start);
573 
574 		if (fatal_signal_pending(current))
575 			return 0;
576 
577 		ret = flush_icache_user_range(start, start + chunk);
578 		if (ret)
579 			return ret;
580 
581 		cond_resched();
582 		start += chunk;
583 	} while (start < end);
584 
585 	return 0;
586 }
587 
588 static inline int
do_cache_op(unsigned long start,unsigned long end,int flags)589 do_cache_op(unsigned long start, unsigned long end, int flags)
590 {
591 	if (end < start || flags)
592 		return -EINVAL;
593 
594 	if (!access_ok((void __user *)start, end - start))
595 		return -EFAULT;
596 
597 	return __do_cache_op(start, end);
598 }
599 
600 /*
601  * Handle all unrecognised system calls.
602  *  0x9f0000 - 0x9fffff are some more esoteric system calls
603  */
604 #define NR(x) ((__ARM_NR_##x) - __ARM_NR_BASE)
arm_syscall(int no,struct pt_regs * regs)605 asmlinkage int arm_syscall(int no, struct pt_regs *regs)
606 {
607 	if ((no >> 16) != (__ARM_NR_BASE>> 16))
608 		return bad_syscall(no, regs);
609 
610 	switch (no & 0xffff) {
611 	case 0: /* branch through 0 */
612 		arm_notify_die("branch through zero", regs,
613 			       SIGSEGV, SEGV_MAPERR, NULL, 0, 0);
614 		return 0;
615 
616 	case NR(breakpoint): /* SWI BREAK_POINT */
617 		regs->ARM_pc -= thumb_mode(regs) ? 2 : 4;
618 		ptrace_break(regs);
619 		return regs->ARM_r0;
620 
621 	/*
622 	 * Flush a region from virtual address 'r0' to virtual address 'r1'
623 	 * _exclusive_.  There is no alignment requirement on either address;
624 	 * user space does not need to know the hardware cache layout.
625 	 *
626 	 * r2 contains flags.  It should ALWAYS be passed as ZERO until it
627 	 * is defined to be something else.  For now we ignore it, but may
628 	 * the fires of hell burn in your belly if you break this rule. ;)
629 	 *
630 	 * (at a later date, we may want to allow this call to not flush
631 	 * various aspects of the cache.  Passing '0' will guarantee that
632 	 * everything necessary gets flushed to maintain consistency in
633 	 * the specified region).
634 	 */
635 	case NR(cacheflush):
636 		return do_cache_op(regs->ARM_r0, regs->ARM_r1, regs->ARM_r2);
637 
638 	case NR(usr26):
639 		if (!(elf_hwcap & HWCAP_26BIT))
640 			break;
641 		regs->ARM_cpsr &= ~MODE32_BIT;
642 		return regs->ARM_r0;
643 
644 	case NR(usr32):
645 		if (!(elf_hwcap & HWCAP_26BIT))
646 			break;
647 		regs->ARM_cpsr |= MODE32_BIT;
648 		return regs->ARM_r0;
649 
650 	case NR(set_tls):
651 		set_tls(regs->ARM_r0);
652 		return 0;
653 
654 	case NR(get_tls):
655 		return current_thread_info()->tp_value[0];
656 
657 	default:
658 		/* Calls 9f00xx..9f07ff are defined to return -ENOSYS
659 		   if not implemented, rather than raising SIGILL.  This
660 		   way the calling program can gracefully determine whether
661 		   a feature is supported.  */
662 		if ((no & 0xffff) <= 0x7ff)
663 			return -ENOSYS;
664 		break;
665 	}
666 #ifdef CONFIG_DEBUG_USER
667 	/*
668 	 * experience shows that these seem to indicate that
669 	 * something catastrophic has happened
670 	 */
671 	if (user_debug & UDBG_SYSCALL) {
672 		pr_err("[%d] %s: arm syscall %d\n",
673 		       task_pid_nr(current), current->comm, no);
674 		dump_instr(KERN_ERR, regs);
675 		if (user_mode(regs)) {
676 			__show_regs(regs);
677 			c_backtrace(frame_pointer(regs), processor_mode(regs), KERN_ERR);
678 		}
679 	}
680 #endif
681 	arm_notify_die("Oops - bad syscall(2)", regs, SIGILL, ILL_ILLTRP,
682 		       (void __user *)instruction_pointer(regs) -
683 			 (thumb_mode(regs) ? 2 : 4),
684 		       no, 0);
685 	return 0;
686 }
687 
688 #ifdef CONFIG_TLS_REG_EMUL
689 
690 /*
691  * We might be running on an ARMv6+ processor which should have the TLS
692  * register but for some reason we can't use it, or maybe an SMP system
693  * using a pre-ARMv6 processor (there are apparently a few prototypes like
694  * that in existence) and therefore access to that register must be
695  * emulated.
696  */
697 
get_tp_trap(struct pt_regs * regs,unsigned int instr)698 static int get_tp_trap(struct pt_regs *regs, unsigned int instr)
699 {
700 	int reg = (instr >> 12) & 15;
701 	if (reg == 15)
702 		return 1;
703 	regs->uregs[reg] = current_thread_info()->tp_value[0];
704 	regs->ARM_pc += 4;
705 	return 0;
706 }
707 
708 static struct undef_hook arm_mrc_hook = {
709 	.instr_mask	= 0x0fff0fff,
710 	.instr_val	= 0x0e1d0f70,
711 	.cpsr_mask	= PSR_T_BIT,
712 	.cpsr_val	= 0,
713 	.fn		= get_tp_trap,
714 };
715 
arm_mrc_hook_init(void)716 static int __init arm_mrc_hook_init(void)
717 {
718 	register_undef_hook(&arm_mrc_hook);
719 	return 0;
720 }
721 
722 late_initcall(arm_mrc_hook_init);
723 
724 #endif
725 
726 /*
727  * A data abort trap was taken, but we did not handle the instruction.
728  * Try to abort the user program, or panic if it was the kernel.
729  */
730 asmlinkage void
baddataabort(int code,unsigned long instr,struct pt_regs * regs)731 baddataabort(int code, unsigned long instr, struct pt_regs *regs)
732 {
733 	unsigned long addr = instruction_pointer(regs);
734 
735 #ifdef CONFIG_DEBUG_USER
736 	if (user_debug & UDBG_BADABORT) {
737 		pr_err("8<--- cut here ---\n");
738 		pr_err("[%d] %s: bad data abort: code %d instr 0x%08lx\n",
739 		       task_pid_nr(current), current->comm, code, instr);
740 		dump_instr(KERN_ERR, regs);
741 		show_pte(KERN_ERR, current->mm, addr);
742 	}
743 #endif
744 
745 	arm_notify_die("unknown data abort code", regs,
746 		       SIGILL, ILL_ILLOPC, (void __user *)addr, instr, 0);
747 }
748 
__readwrite_bug(const char * fn)749 void __readwrite_bug(const char *fn)
750 {
751 	pr_err("%s called, but not implemented\n", fn);
752 	BUG();
753 }
754 EXPORT_SYMBOL(__readwrite_bug);
755 
__pte_error(const char * file,int line,pte_t pte)756 void __pte_error(const char *file, int line, pte_t pte)
757 {
758 	pr_err("%s:%d: bad pte %08llx.\n", file, line, (long long)pte_val(pte));
759 }
760 
__pmd_error(const char * file,int line,pmd_t pmd)761 void __pmd_error(const char *file, int line, pmd_t pmd)
762 {
763 	pr_err("%s:%d: bad pmd %08llx.\n", file, line, (long long)pmd_val(pmd));
764 }
765 
__pgd_error(const char * file,int line,pgd_t pgd)766 void __pgd_error(const char *file, int line, pgd_t pgd)
767 {
768 	pr_err("%s:%d: bad pgd %08llx.\n", file, line, (long long)pgd_val(pgd));
769 }
770 
__div0(void)771 asmlinkage void __div0(void)
772 {
773 	pr_err("Division by zero in kernel.\n");
774 	dump_stack();
775 }
776 EXPORT_SYMBOL(__div0);
777 
abort(void)778 void abort(void)
779 {
780 	BUG();
781 
782 	/* if that doesn't kill us, halt */
783 	panic("Oops failed to kill thread");
784 }
785 
786 #ifdef CONFIG_KUSER_HELPERS
kuser_init(void * vectors)787 static void __init kuser_init(void *vectors)
788 {
789 	extern char __kuser_helper_start[], __kuser_helper_end[];
790 	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
791 
792 	memcpy(vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz);
793 
794 	/*
795 	 * vectors + 0xfe0 = __kuser_get_tls
796 	 * vectors + 0xfe8 = hardware TLS instruction at 0xffff0fe8
797 	 */
798 	if (tls_emu || has_tls_reg)
799 		memcpy(vectors + 0xfe0, vectors + 0xfe8, 4);
800 }
801 #else
kuser_init(void * vectors)802 static inline void __init kuser_init(void *vectors)
803 {
804 }
805 #endif
806 
807 #ifndef CONFIG_CPU_V7M
copy_from_lma(void * vma,void * lma_start,void * lma_end)808 static void copy_from_lma(void *vma, void *lma_start, void *lma_end)
809 {
810 	memcpy(vma, lma_start, lma_end - lma_start);
811 }
812 
flush_vectors(void * vma,size_t offset,size_t size)813 static void flush_vectors(void *vma, size_t offset, size_t size)
814 {
815 	unsigned long start = (unsigned long)vma + offset;
816 	unsigned long end = start + size;
817 
818 	flush_icache_range(start, end);
819 }
820 
821 #ifdef CONFIG_HARDEN_BRANCH_HISTORY
spectre_bhb_update_vectors(unsigned int method)822 int spectre_bhb_update_vectors(unsigned int method)
823 {
824 	extern char __vectors_bhb_bpiall_start[], __vectors_bhb_bpiall_end[];
825 	extern char __vectors_bhb_loop8_start[], __vectors_bhb_loop8_end[];
826 	void *vec_start, *vec_end;
827 
828 	if (system_state >= SYSTEM_FREEING_INITMEM) {
829 		pr_err("CPU%u: Spectre BHB workaround too late - system vulnerable\n",
830 		       smp_processor_id());
831 		return SPECTRE_VULNERABLE;
832 	}
833 
834 	switch (method) {
835 	case SPECTRE_V2_METHOD_LOOP8:
836 		vec_start = __vectors_bhb_loop8_start;
837 		vec_end = __vectors_bhb_loop8_end;
838 		break;
839 
840 	case SPECTRE_V2_METHOD_BPIALL:
841 		vec_start = __vectors_bhb_bpiall_start;
842 		vec_end = __vectors_bhb_bpiall_end;
843 		break;
844 
845 	default:
846 		pr_err("CPU%u: unknown Spectre BHB state %d\n",
847 		       smp_processor_id(), method);
848 		return SPECTRE_VULNERABLE;
849 	}
850 
851 	copy_from_lma(vectors_page, vec_start, vec_end);
852 	flush_vectors(vectors_page, 0, vec_end - vec_start);
853 
854 	return SPECTRE_MITIGATED;
855 }
856 #endif
857 
early_trap_init(void * vectors_base)858 void __init early_trap_init(void *vectors_base)
859 {
860 	extern char __stubs_start[], __stubs_end[];
861 	extern char __vectors_start[], __vectors_end[];
862 	unsigned i;
863 
864 	vectors_page = vectors_base;
865 
866 	/*
867 	 * Poison the vectors page with an undefined instruction.  This
868 	 * instruction is chosen to be undefined for both ARM and Thumb
869 	 * ISAs.  The Thumb version is an undefined instruction with a
870 	 * branch back to the undefined instruction.
871 	 */
872 	for (i = 0; i < PAGE_SIZE / sizeof(u32); i++)
873 		((u32 *)vectors_base)[i] = 0xe7fddef1;
874 
875 	/*
876 	 * Copy the vectors, stubs and kuser helpers (in entry-armv.S)
877 	 * into the vector page, mapped at 0xffff0000, and ensure these
878 	 * are visible to the instruction stream.
879 	 */
880 	copy_from_lma(vectors_base, __vectors_start, __vectors_end);
881 	copy_from_lma(vectors_base + 0x1000, __stubs_start, __stubs_end);
882 
883 	kuser_init(vectors_base);
884 
885 	flush_vectors(vectors_base, 0, PAGE_SIZE * 2);
886 }
887 #else /* ifndef CONFIG_CPU_V7M */
early_trap_init(void * vectors_base)888 void __init early_trap_init(void *vectors_base)
889 {
890 	/*
891 	 * on V7-M there is no need to copy the vector table to a dedicated
892 	 * memory area. The address is configurable and so a table in the kernel
893 	 * image can be used.
894 	 */
895 }
896 #endif
897 
898 #ifdef CONFIG_VMAP_STACK
899 
900 DECLARE_PER_CPU(u8 *, irq_stack_ptr);
901 
902 asmlinkage DEFINE_PER_CPU(u8 *, overflow_stack_ptr);
903 
allocate_overflow_stacks(void)904 static int __init allocate_overflow_stacks(void)
905 {
906 	u8 *stack;
907 	int cpu;
908 
909 	for_each_possible_cpu(cpu) {
910 		stack = (u8 *)__get_free_page(GFP_KERNEL);
911 		if (WARN_ON(!stack))
912 			return -ENOMEM;
913 		per_cpu(overflow_stack_ptr, cpu) = &stack[OVERFLOW_STACK_SIZE];
914 	}
915 	return 0;
916 }
917 early_initcall(allocate_overflow_stacks);
918 
handle_bad_stack(struct pt_regs * regs)919 asmlinkage void handle_bad_stack(struct pt_regs *regs)
920 {
921 	unsigned long tsk_stk = (unsigned long)current->stack;
922 #ifdef CONFIG_IRQSTACKS
923 	unsigned long irq_stk = (unsigned long)this_cpu_read(irq_stack_ptr);
924 #endif
925 	unsigned long ovf_stk = (unsigned long)this_cpu_read(overflow_stack_ptr);
926 
927 	console_verbose();
928 	pr_emerg("Insufficient stack space to handle exception!");
929 
930 	pr_emerg("Task stack:     [0x%08lx..0x%08lx]\n",
931 		 tsk_stk, tsk_stk + THREAD_SIZE);
932 #ifdef CONFIG_IRQSTACKS
933 	pr_emerg("IRQ stack:      [0x%08lx..0x%08lx]\n",
934 		 irq_stk - THREAD_SIZE, irq_stk);
935 #endif
936 	pr_emerg("Overflow stack: [0x%08lx..0x%08lx]\n",
937 		 ovf_stk - OVERFLOW_STACK_SIZE, ovf_stk);
938 
939 	die("kernel stack overflow", regs, 0);
940 }
941 
942 #ifndef CONFIG_ARM_LPAE
943 /*
944  * Normally, we rely on the logic in do_translation_fault() to update stale PMD
945  * entries covering the vmalloc space in a task's page tables when it first
946  * accesses the region in question. Unfortunately, this is not sufficient when
947  * the task stack resides in the vmalloc region, as do_translation_fault() is a
948  * C function that needs a stack to run.
949  *
950  * So we need to ensure that these PMD entries are up to date *before* the MM
951  * switch. As we already have some logic in the MM switch path that takes care
952  * of this, let's trigger it by bumping the counter every time the core vmalloc
953  * code modifies a PMD entry in the vmalloc region. Use release semantics on
954  * the store so that other CPUs observing the counter's new value are
955  * guaranteed to see the updated page table entries as well.
956  */
arch_sync_kernel_mappings(unsigned long start,unsigned long end)957 void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
958 {
959 	if (start < VMALLOC_END && end > VMALLOC_START)
960 		atomic_inc_return_release(&init_mm.context.vmalloc_seq);
961 }
962 #endif
963 #endif
964