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