1 /*
2 * linux/arch/arm/kernel/traps.c
3 *
4 * Copyright (C) 1995-2002 Russell King
5 * Fragments that appear the same as linux/arch/i386/kernel/traps.c (C) Linus Torvalds
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * 'traps.c' handles hardware exceptions after we have saved some state in
12 * 'linux/arch/arm/lib/traps.S'. Mostly a debugging aid, but will probably
13 * kill the offending process.
14 */
15 #include <linux/module.h>
16 #include <linux/signal.h>
17 #include <linux/spinlock.h>
18 #include <linux/personality.h>
19 #include <linux/kallsyms.h>
20 #include <linux/delay.h>
21 #include <linux/init.h>
22 #include <linux/kprobes.h>
23
24 #include <asm/atomic.h>
25 #include <asm/cacheflush.h>
26 #include <asm/system.h>
27 #include <asm/uaccess.h>
28 #include <asm/unistd.h>
29 #include <asm/traps.h>
30 #include <asm/io.h>
31
32 #include "ptrace.h"
33 #include "signal.h"
34
35 static const char *handler[]= { "prefetch abort", "data abort", "address exception", "interrupt" };
36
37 #ifdef CONFIG_DEBUG_USER
38 unsigned int user_debug;
39
40 static int __init user_debug_setup(char *str)
41 {
42 get_option(&str, &user_debug);
43 return 1;
44 }
45 __setup("user_debug=", user_debug_setup);
46 #endif
47
48 static void dump_mem(const char *str, unsigned long bottom, unsigned long top);
49
50 void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long frame)
51 {
52 #ifdef CONFIG_KALLSYMS
53 printk("[<%08lx>] ", where);
54 print_symbol("(%s) ", where);
55 printk("from [<%08lx>] ", from);
56 print_symbol("(%s)\n", from);
57 #else
58 printk("Function entered at [<%08lx>] from [<%08lx>]\n", where, from);
59 #endif
60
61 if (in_exception_text(where))
62 dump_mem("Exception stack", frame + 4, frame + 4 + sizeof(struct pt_regs));
63 }
64
65 /*
66 * Stack pointers should always be within the kernels view of
67 * physical memory. If it is not there, then we can't dump
68 * out any information relating to the stack.
69 */
70 static int verify_stack(unsigned long sp)
71 {
72 if (sp < PAGE_OFFSET || (sp > (unsigned long)high_memory && high_memory != 0))
73 return -EFAULT;
74
75 return 0;
76 }
77
78 /*
79 * Dump out the contents of some memory nicely...
80 */
81 static void dump_mem(const char *str, unsigned long bottom, unsigned long top)
82 {
83 unsigned long p = bottom & ~31;
84 mm_segment_t fs;
85 int i;
86
87 /*
88 * We need to switch to kernel mode so that we can use __get_user
89 * to safely read from kernel space. Note that we now dump the
90 * code first, just in case the backtrace kills us.
91 */
92 fs = get_fs();
93 set_fs(KERNEL_DS);
94
95 printk("%s(0x%08lx to 0x%08lx)\n", str, bottom, top);
96
97 for (p = bottom & ~31; p < top;) {
98 printk("%04lx: ", p & 0xffff);
99
100 for (i = 0; i < 8; i++, p += 4) {
101 unsigned int val;
102
103 if (p < bottom || p >= top)
104 printk(" ");
105 else {
106 __get_user(val, (unsigned long *)p);
107 printk("%08x ", val);
108 }
109 }
110 printk ("\n");
111 }
112
113 set_fs(fs);
114 }
115
116 static void dump_instr(struct pt_regs *regs)
117 {
118 unsigned long addr = instruction_pointer(regs);
119 const int thumb = thumb_mode(regs);
120 const int width = thumb ? 4 : 8;
121 mm_segment_t fs;
122 int i;
123
124 /*
125 * We need to switch to kernel mode so that we can use __get_user
126 * to safely read from kernel space. Note that we now dump the
127 * code first, just in case the backtrace kills us.
128 */
129 fs = get_fs();
130 set_fs(KERNEL_DS);
131
132 printk("Code: ");
133 for (i = -4; i < 1; i++) {
134 unsigned int val, bad;
135
136 if (thumb)
137 bad = __get_user(val, &((u16 *)addr)[i]);
138 else
139 bad = __get_user(val, &((u32 *)addr)[i]);
140
141 if (!bad)
142 printk(i == 0 ? "(%0*x) " : "%0*x ", width, val);
143 else {
144 printk("bad PC value.");
145 break;
146 }
147 }
148 printk("\n");
149
150 set_fs(fs);
151 }
152
153 static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
154 {
155 unsigned int fp;
156 int ok = 1;
157
158 printk("Backtrace: ");
159 fp = regs->ARM_fp;
160 if (!fp) {
161 printk("no frame pointer");
162 ok = 0;
163 } else if (verify_stack(fp)) {
164 printk("invalid frame pointer 0x%08x", fp);
165 ok = 0;
166 } else if (fp < (unsigned long)end_of_stack(tsk))
167 printk("frame pointer underflow");
168 printk("\n");
169
170 if (ok)
171 c_backtrace(fp, processor_mode(regs));
172 }
173
174 void dump_stack(void)
175 {
176 __backtrace();
177 }
178
179 EXPORT_SYMBOL(dump_stack);
180
181 void show_stack(struct task_struct *tsk, unsigned long *sp)
182 {
183 unsigned long fp;
184
185 if (!tsk)
186 tsk = current;
187
188 if (tsk != current)
189 fp = thread_saved_fp(tsk);
190 else
191 asm("mov %0, fp" : "=r" (fp) : : "cc");
192
193 c_backtrace(fp, 0x10);
194 barrier();
195 }
196
197 #ifdef CONFIG_PREEMPT
198 #define S_PREEMPT " PREEMPT"
199 #else
200 #define S_PREEMPT ""
201 #endif
202 #ifdef CONFIG_SMP
203 #define S_SMP " SMP"
204 #else
205 #define S_SMP ""
206 #endif
207
208 static void __die(const char *str, int err, struct thread_info *thread, struct pt_regs *regs)
209 {
210 struct task_struct *tsk = thread->task;
211 static int die_counter;
212
213 printk("Internal error: %s: %x [#%d]" S_PREEMPT S_SMP "\n",
214 str, err, ++die_counter);
215 print_modules();
216 __show_regs(regs);
217 printk("Process %s (pid: %d, stack limit = 0x%p)\n",
218 tsk->comm, task_pid_nr(tsk), thread + 1);
219
220 if (!user_mode(regs) || in_interrupt()) {
221 dump_mem("Stack: ", regs->ARM_sp,
222 THREAD_SIZE + (unsigned long)task_stack_page(tsk));
223 dump_backtrace(regs, tsk);
224 dump_instr(regs);
225 }
226 }
227
228 DEFINE_SPINLOCK(die_lock);
229
230 /*
231 * This function is protected against re-entrancy.
232 */
233 NORET_TYPE void die(const char *str, struct pt_regs *regs, int err)
234 {
235 struct thread_info *thread = current_thread_info();
236
237 oops_enter();
238
239 console_verbose();
240 spin_lock_irq(&die_lock);
241 bust_spinlocks(1);
242 __die(str, err, thread, regs);
243 bust_spinlocks(0);
244 add_taint(TAINT_DIE);
245 spin_unlock_irq(&die_lock);
246
247 if (in_interrupt())
248 panic("Fatal exception in interrupt");
249
250 if (panic_on_oops)
251 panic("Fatal exception");
252
253 oops_exit();
254 do_exit(SIGSEGV);
255 }
256
257 void arm_notify_die(const char *str, struct pt_regs *regs,
258 struct siginfo *info, unsigned long err, unsigned long trap)
259 {
260 if (user_mode(regs)) {
261 current->thread.error_code = err;
262 current->thread.trap_no = trap;
263
264 force_sig_info(info->si_signo, info, current);
265 } else {
266 die(str, regs, err);
267 }
268 }
269
270 static LIST_HEAD(undef_hook);
271 static DEFINE_SPINLOCK(undef_lock);
272
273 void register_undef_hook(struct undef_hook *hook)
274 {
275 unsigned long flags;
276
277 spin_lock_irqsave(&undef_lock, flags);
278 list_add(&hook->node, &undef_hook);
279 spin_unlock_irqrestore(&undef_lock, flags);
280 }
281
282 void unregister_undef_hook(struct undef_hook *hook)
283 {
284 unsigned long flags;
285
286 spin_lock_irqsave(&undef_lock, flags);
287 list_del(&hook->node);
288 spin_unlock_irqrestore(&undef_lock, flags);
289 }
290
291 asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
292 {
293 unsigned int correction = thumb_mode(regs) ? 2 : 4;
294 unsigned int instr;
295 struct undef_hook *hook;
296 siginfo_t info;
297 void __user *pc;
298 unsigned long flags;
299
300 /*
301 * According to the ARM ARM, PC is 2 or 4 bytes ahead,
302 * depending whether we're in Thumb mode or not.
303 * Correct this offset.
304 */
305 regs->ARM_pc -= correction;
306
307 pc = (void __user *)instruction_pointer(regs);
308
309 if (processor_mode(regs) == SVC_MODE) {
310 instr = *(u32 *) pc;
311 } else if (thumb_mode(regs)) {
312 get_user(instr, (u16 __user *)pc);
313 } else {
314 get_user(instr, (u32 __user *)pc);
315 }
316
317 #ifdef CONFIG_KPROBES
318 /*
319 * It is possible to have recursive kprobes, so we can't call
320 * the kprobe trap handler with the undef_lock held.
321 */
322 if (instr == KPROBE_BREAKPOINT_INSTRUCTION && !user_mode(regs)) {
323 kprobe_trap_handler(regs, instr);
324 return;
325 }
326 #endif
327
328 spin_lock_irqsave(&undef_lock, flags);
329 list_for_each_entry(hook, &undef_hook, node) {
330 if ((instr & hook->instr_mask) == hook->instr_val &&
331 (regs->ARM_cpsr & hook->cpsr_mask) == hook->cpsr_val) {
332 if (hook->fn(regs, instr) == 0) {
333 spin_unlock_irqrestore(&undef_lock, flags);
334 return;
335 }
336 }
337 }
338 spin_unlock_irqrestore(&undef_lock, flags);
339
340 #ifdef CONFIG_DEBUG_USER
341 if (user_debug & UDBG_UNDEFINED) {
342 printk(KERN_INFO "%s (%d): undefined instruction: pc=%p\n",
343 current->comm, task_pid_nr(current), pc);
344 dump_instr(regs);
345 }
346 #endif
347
348 info.si_signo = SIGILL;
349 info.si_errno = 0;
350 info.si_code = ILL_ILLOPC;
351 info.si_addr = pc;
352
353 arm_notify_die("Oops - undefined instruction", regs, &info, 0, 6);
354 }
355
356 asmlinkage void do_unexp_fiq (struct pt_regs *regs)
357 {
358 printk("Hmm. Unexpected FIQ received, but trying to continue\n");
359 printk("You may have a hardware problem...\n");
360 }
361
362 /*
363 * bad_mode handles the impossible case in the vectors. If you see one of
364 * these, then it's extremely serious, and could mean you have buggy hardware.
365 * It never returns, and never tries to sync. We hope that we can at least
366 * dump out some state information...
367 */
368 asmlinkage void bad_mode(struct pt_regs *regs, int reason)
369 {
370 console_verbose();
371
372 printk(KERN_CRIT "Bad mode in %s handler detected\n", handler[reason]);
373
374 die("Oops - bad mode", regs, 0);
375 local_irq_disable();
376 panic("bad mode");
377 }
378
379 static int bad_syscall(int n, struct pt_regs *regs)
380 {
381 struct thread_info *thread = current_thread_info();
382 siginfo_t info;
383
384 if (current->personality != PER_LINUX &&
385 current->personality != PER_LINUX_32BIT &&
386 thread->exec_domain->handler) {
387 thread->exec_domain->handler(n, regs);
388 return regs->ARM_r0;
389 }
390
391 #ifdef CONFIG_DEBUG_USER
392 if (user_debug & UDBG_SYSCALL) {
393 printk(KERN_ERR "[%d] %s: obsolete system call %08x.\n",
394 task_pid_nr(current), current->comm, n);
395 dump_instr(regs);
396 }
397 #endif
398
399 info.si_signo = SIGILL;
400 info.si_errno = 0;
401 info.si_code = ILL_ILLTRP;
402 info.si_addr = (void __user *)instruction_pointer(regs) -
403 (thumb_mode(regs) ? 2 : 4);
404
405 arm_notify_die("Oops - bad syscall", regs, &info, n, 0);
406
407 return regs->ARM_r0;
408 }
409
410 static inline void
411 do_cache_op(unsigned long start, unsigned long end, int flags)
412 {
413 struct vm_area_struct *vma;
414
415 if (end < start || flags)
416 return;
417
418 vma = find_vma(current->active_mm, start);
419 if (vma && vma->vm_start < end) {
420 if (start < vma->vm_start)
421 start = vma->vm_start;
422 if (end > vma->vm_end)
423 end = vma->vm_end;
424
425 flush_cache_user_range(vma, start, end);
426 }
427 }
428
429 /*
430 * Handle all unrecognised system calls.
431 * 0x9f0000 - 0x9fffff are some more esoteric system calls
432 */
433 #define NR(x) ((__ARM_NR_##x) - __ARM_NR_BASE)
434 asmlinkage int arm_syscall(int no, struct pt_regs *regs)
435 {
436 struct thread_info *thread = current_thread_info();
437 siginfo_t info;
438
439 if ((no >> 16) != (__ARM_NR_BASE>> 16))
440 return bad_syscall(no, regs);
441
442 switch (no & 0xffff) {
443 case 0: /* branch through 0 */
444 info.si_signo = SIGSEGV;
445 info.si_errno = 0;
446 info.si_code = SEGV_MAPERR;
447 info.si_addr = NULL;
448
449 arm_notify_die("branch through zero", regs, &info, 0, 0);
450 return 0;
451
452 case NR(breakpoint): /* SWI BREAK_POINT */
453 regs->ARM_pc -= thumb_mode(regs) ? 2 : 4;
454 ptrace_break(current, regs);
455 return regs->ARM_r0;
456
457 /*
458 * Flush a region from virtual address 'r0' to virtual address 'r1'
459 * _exclusive_. There is no alignment requirement on either address;
460 * user space does not need to know the hardware cache layout.
461 *
462 * r2 contains flags. It should ALWAYS be passed as ZERO until it
463 * is defined to be something else. For now we ignore it, but may
464 * the fires of hell burn in your belly if you break this rule. ;)
465 *
466 * (at a later date, we may want to allow this call to not flush
467 * various aspects of the cache. Passing '' will guarantee that
468 * everything necessary gets flushed to maintain consistency in
469 * the specified region).
470 */
471 case NR(cacheflush):
472 do_cache_op(regs->ARM_r0, regs->ARM_r1, regs->ARM_r2);
473 return 0;
474
475 case NR(usr26):
476 if (!(elf_hwcap & HWCAP_26BIT))
477 break;
478 regs->ARM_cpsr &= ~MODE32_BIT;
479 return regs->ARM_r0;
480
481 case NR(usr32):
482 if (!(elf_hwcap & HWCAP_26BIT))
483 break;
484 regs->ARM_cpsr |= MODE32_BIT;
485 return regs->ARM_r0;
486
487 case NR(set_tls):
488 thread->tp_value = regs->ARM_r0;
489 #if defined(CONFIG_HAS_TLS_REG)
490 asm ("mcr p15, 0, %0, c13, c0, 3" : : "r" (regs->ARM_r0) );
491 #elif !defined(CONFIG_TLS_REG_EMUL)
492 /*
493 * User space must never try to access this directly.
494 * Expect your app to break eventually if you do so.
495 * The user helper at 0xffff0fe0 must be used instead.
496 * (see entry-armv.S for details)
497 */
498 *((unsigned int *)0xffff0ff0) = regs->ARM_r0;
499 #endif
500 return 0;
501
502 #ifdef CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG
503 /*
504 * Atomically store r1 in *r2 if *r2 is equal to r0 for user space.
505 * Return zero in r0 if *MEM was changed or non-zero if no exchange
506 * happened. Also set the user C flag accordingly.
507 * If access permissions have to be fixed up then non-zero is
508 * returned and the operation has to be re-attempted.
509 *
510 * *NOTE*: This is a ghost syscall private to the kernel. Only the
511 * __kuser_cmpxchg code in entry-armv.S should be aware of its
512 * existence. Don't ever use this from user code.
513 */
514 case 0xfff0:
515 for (;;) {
516 extern void do_DataAbort(unsigned long addr, unsigned int fsr,
517 struct pt_regs *regs);
518 unsigned long val;
519 unsigned long addr = regs->ARM_r2;
520 struct mm_struct *mm = current->mm;
521 pgd_t *pgd; pmd_t *pmd; pte_t *pte;
522 spinlock_t *ptl;
523
524 regs->ARM_cpsr &= ~PSR_C_BIT;
525 down_read(&mm->mmap_sem);
526 pgd = pgd_offset(mm, addr);
527 if (!pgd_present(*pgd))
528 goto bad_access;
529 pmd = pmd_offset(pgd, addr);
530 if (!pmd_present(*pmd))
531 goto bad_access;
532 pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
533 if (!pte_present(*pte) || !pte_dirty(*pte)) {
534 pte_unmap_unlock(pte, ptl);
535 goto bad_access;
536 }
537 val = *(unsigned long *)addr;
538 val -= regs->ARM_r0;
539 if (val == 0) {
540 *(unsigned long *)addr = regs->ARM_r1;
541 regs->ARM_cpsr |= PSR_C_BIT;
542 }
543 pte_unmap_unlock(pte, ptl);
544 up_read(&mm->mmap_sem);
545 return val;
546
547 bad_access:
548 up_read(&mm->mmap_sem);
549 /* simulate a write access fault */
550 do_DataAbort(addr, 15 + (1 << 11), regs);
551 }
552 #endif
553
554 default:
555 /* Calls 9f00xx..9f07ff are defined to return -ENOSYS
556 if not implemented, rather than raising SIGILL. This
557 way the calling program can gracefully determine whether
558 a feature is supported. */
559 if (no <= 0x7ff)
560 return -ENOSYS;
561 break;
562 }
563 #ifdef CONFIG_DEBUG_USER
564 /*
565 * experience shows that these seem to indicate that
566 * something catastrophic has happened
567 */
568 if (user_debug & UDBG_SYSCALL) {
569 printk("[%d] %s: arm syscall %d\n",
570 task_pid_nr(current), current->comm, no);
571 dump_instr(regs);
572 if (user_mode(regs)) {
573 __show_regs(regs);
574 c_backtrace(regs->ARM_fp, processor_mode(regs));
575 }
576 }
577 #endif
578 info.si_signo = SIGILL;
579 info.si_errno = 0;
580 info.si_code = ILL_ILLTRP;
581 info.si_addr = (void __user *)instruction_pointer(regs) -
582 (thumb_mode(regs) ? 2 : 4);
583
584 arm_notify_die("Oops - bad syscall(2)", regs, &info, no, 0);
585 return 0;
586 }
587
588 #ifdef CONFIG_TLS_REG_EMUL
589
590 /*
591 * We might be running on an ARMv6+ processor which should have the TLS
592 * register but for some reason we can't use it, or maybe an SMP system
593 * using a pre-ARMv6 processor (there are apparently a few prototypes like
594 * that in existence) and therefore access to that register must be
595 * emulated.
596 */
597
598 static int get_tp_trap(struct pt_regs *regs, unsigned int instr)
599 {
600 int reg = (instr >> 12) & 15;
601 if (reg == 15)
602 return 1;
603 regs->uregs[reg] = current_thread_info()->tp_value;
604 regs->ARM_pc += 4;
605 return 0;
606 }
607
608 static struct undef_hook arm_mrc_hook = {
609 .instr_mask = 0x0fff0fff,
610 .instr_val = 0x0e1d0f70,
611 .cpsr_mask = PSR_T_BIT,
612 .cpsr_val = 0,
613 .fn = get_tp_trap,
614 };
615
616 static int __init arm_mrc_hook_init(void)
617 {
618 register_undef_hook(&arm_mrc_hook);
619 return 0;
620 }
621
622 late_initcall(arm_mrc_hook_init);
623
624 #endif
625
626 void __bad_xchg(volatile void *ptr, int size)
627 {
628 printk("xchg: bad data size: pc 0x%p, ptr 0x%p, size %d\n",
629 __builtin_return_address(0), ptr, size);
630 BUG();
631 }
632 EXPORT_SYMBOL(__bad_xchg);
633
634 /*
635 * A data abort trap was taken, but we did not handle the instruction.
636 * Try to abort the user program, or panic if it was the kernel.
637 */
638 asmlinkage void
639 baddataabort(int code, unsigned long instr, struct pt_regs *regs)
640 {
641 unsigned long addr = instruction_pointer(regs);
642 siginfo_t info;
643
644 #ifdef CONFIG_DEBUG_USER
645 if (user_debug & UDBG_BADABORT) {
646 printk(KERN_ERR "[%d] %s: bad data abort: code %d instr 0x%08lx\n",
647 task_pid_nr(current), current->comm, code, instr);
648 dump_instr(regs);
649 show_pte(current->mm, addr);
650 }
651 #endif
652
653 info.si_signo = SIGILL;
654 info.si_errno = 0;
655 info.si_code = ILL_ILLOPC;
656 info.si_addr = (void __user *)addr;
657
658 arm_notify_die("unknown data abort code", regs, &info, instr, 0);
659 }
660
661 void __attribute__((noreturn)) __bug(const char *file, int line)
662 {
663 printk(KERN_CRIT"kernel BUG at %s:%d!\n", file, line);
664 *(int *)0 = 0;
665
666 /* Avoid "noreturn function does return" */
667 for (;;);
668 }
669 EXPORT_SYMBOL(__bug);
670
671 void __readwrite_bug(const char *fn)
672 {
673 printk("%s called, but not implemented\n", fn);
674 BUG();
675 }
676 EXPORT_SYMBOL(__readwrite_bug);
677
678 void __pte_error(const char *file, int line, unsigned long val)
679 {
680 printk("%s:%d: bad pte %08lx.\n", file, line, val);
681 }
682
683 void __pmd_error(const char *file, int line, unsigned long val)
684 {
685 printk("%s:%d: bad pmd %08lx.\n", file, line, val);
686 }
687
688 void __pgd_error(const char *file, int line, unsigned long val)
689 {
690 printk("%s:%d: bad pgd %08lx.\n", file, line, val);
691 }
692
693 asmlinkage void __div0(void)
694 {
695 printk("Division by zero in kernel.\n");
696 dump_stack();
697 }
698 EXPORT_SYMBOL(__div0);
699
700 void abort(void)
701 {
702 BUG();
703
704 /* if that doesn't kill us, halt */
705 panic("Oops failed to kill thread");
706 }
707 EXPORT_SYMBOL(abort);
708
709 void __init trap_init(void)
710 {
711 unsigned long vectors = CONFIG_VECTORS_BASE;
712 extern char __stubs_start[], __stubs_end[];
713 extern char __vectors_start[], __vectors_end[];
714 extern char __kuser_helper_start[], __kuser_helper_end[];
715 int kuser_sz = __kuser_helper_end - __kuser_helper_start;
716
717 /*
718 * Copy the vectors, stubs and kuser helpers (in entry-armv.S)
719 * into the vector page, mapped at 0xffff0000, and ensure these
720 * are visible to the instruction stream.
721 */
722 memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start);
723 memcpy((void *)vectors + 0x200, __stubs_start, __stubs_end - __stubs_start);
724 memcpy((void *)vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz);
725
726 /*
727 * Copy signal return handlers into the vector page, and
728 * set sigreturn to be a pointer to these.
729 */
730 memcpy((void *)KERN_SIGRETURN_CODE, sigreturn_codes,
731 sizeof(sigreturn_codes));
732
733 flush_icache_range(vectors, vectors + PAGE_SIZE);
734 modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
735 }
736
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