summaryrefslogtreecommitdiffstats
path: root/arch/ppc64/kernel/process.c
blob: 887005358eb1faa40bdba25f77d75650f21d851a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
/*
 *  linux/arch/ppc64/kernel/process.c
 *
 *  Derived from "arch/i386/kernel/process.c"
 *    Copyright (C) 1995  Linus Torvalds
 *
 *  Updated and modified by Cort Dougan (cort@cs.nmt.edu) and
 *  Paul Mackerras (paulus@cs.anu.edu.au)
 *
 *  PowerPC version 
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/init.h>
#include <linux/init_task.h>
#include <linux/prctl.h>
#include <linux/ptrace.h>
#include <linux/kallsyms.h>
#include <linux/interrupt.h>
#include <linux/utsname.h>
#include <linux/kprobes.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/prom.h>
#include <asm/ppcdebug.h>
#include <asm/machdep.h>
#include <asm/iSeries/HvCallHpt.h>
#include <asm/cputable.h>
#include <asm/firmware.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>
#include <asm/time.h>
#include <asm/plpar_wrappers.h>

#ifndef CONFIG_SMP
struct task_struct *last_task_used_math = NULL;
struct task_struct *last_task_used_altivec = NULL;
#endif

/*
 * Make sure the floating-point register state in the
 * the thread_struct is up to date for task tsk.
 */
void flush_fp_to_thread(struct task_struct *tsk)
{
	if (tsk->thread.regs) {
		/*
		 * We need to disable preemption here because if we didn't,
		 * another process could get scheduled after the regs->msr
		 * test but before we have finished saving the FP registers
		 * to the thread_struct.  That process could take over the
		 * FPU, and then when we get scheduled again we would store
		 * bogus values for the remaining FP registers.
		 */
		preempt_disable();
		if (tsk->thread.regs->msr & MSR_FP) {
#ifdef CONFIG_SMP
			/*
			 * This should only ever be called for current or
			 * for a stopped child process.  Since we save away
			 * the FP register state on context switch on SMP,
			 * there is something wrong if a stopped child appears
			 * to still have its FP state in the CPU registers.
			 */
			BUG_ON(tsk != current);
#endif
			giveup_fpu(current);
		}
		preempt_enable();
	}
}

void enable_kernel_fp(void)
{
	WARN_ON(preemptible());

#ifdef CONFIG_SMP
	if (current->thread.regs && (current->thread.regs->msr & MSR_FP))
		giveup_fpu(current);
	else
		giveup_fpu(NULL);	/* just enables FP for kernel */
#else
	giveup_fpu(last_task_used_math);
#endif /* CONFIG_SMP */
}
EXPORT_SYMBOL(enable_kernel_fp);

int dump_task_fpu(struct task_struct *tsk, elf_fpregset_t *fpregs)
{
	if (!tsk->thread.regs)
		return 0;
	flush_fp_to_thread(current);

	memcpy(fpregs, &tsk->thread.fpr[0], sizeof(*fpregs));

	return 1;
}

#ifdef CONFIG_ALTIVEC

void enable_kernel_altivec(void)
{
	WARN_ON(preemptible());

#ifdef CONFIG_SMP
	if (current->thread.regs && (current->thread.regs->msr & MSR_VEC))
		giveup_altivec(current);
	else
		giveup_altivec(NULL);	/* just enables FP for kernel */
#else
	giveup_altivec(last_task_used_altivec);
#endif /* CONFIG_SMP */
}
EXPORT_SYMBOL(enable_kernel_altivec);

/*
 * Make sure the VMX/Altivec register state in the
 * the thread_struct is up to date for task tsk.
 */
void flush_altivec_to_thread(struct task_struct *tsk)
{
	if (tsk->thread.regs) {
		preempt_disable();
		if (tsk->thread.regs->msr & MSR_VEC) {
#ifdef CONFIG_SMP
			BUG_ON(tsk != current);
#endif
			giveup_altivec(current);
		}
		preempt_enable();
	}
}

int dump_task_altivec(struct pt_regs *regs, elf_vrregset_t *vrregs)
{
	flush_altivec_to_thread(current);
	memcpy(vrregs, &current->thread.vr[0], sizeof(*vrregs));
	return 1;
}

#endif /* CONFIG_ALTIVEC */

static void set_dabr_spr(unsigned long val)
{
	mtspr(SPRN_DABR, val);
}

int set_dabr(unsigned long dabr)
{
	int ret = 0;

	if (firmware_has_feature(FW_FEATURE_XDABR)) {
		/* We want to catch accesses from kernel and userspace */
		unsigned long flags = H_DABRX_KERNEL|H_DABRX_USER;
		ret = plpar_set_xdabr(dabr, flags);
	} else if (firmware_has_feature(FW_FEATURE_DABR)) {
		ret = plpar_set_dabr(dabr);
	} else {
		set_dabr_spr(dabr);
	}

	return ret;
}

DEFINE_PER_CPU(struct cpu_usage, cpu_usage_array);
static DEFINE_PER_CPU(unsigned long, current_dabr);

struct task_struct *__switch_to(struct task_struct *prev,
				struct task_struct *new)
{
	struct thread_struct *new_thread, *old_thread;
	unsigned long flags;
	struct task_struct *last;

#ifdef CONFIG_SMP
	/* avoid complexity of lazy save/restore of fpu
	 * by just saving it every time we switch out if
	 * this task used the fpu during the last quantum.
	 * 
	 * If it tries to use the fpu again, it'll trap and
	 * reload its fp regs.  So we don't have to do a restore
	 * every switch, just a save.
	 *  -- Cort
	 */
	if (prev->thread.regs && (prev->thread.regs->msr & MSR_FP))
		giveup_fpu(prev);
#ifdef CONFIG_ALTIVEC
	if (prev->thread.regs && (prev->thread.regs->msr & MSR_VEC))
		giveup_altivec(prev);
#endif /* CONFIG_ALTIVEC */
#endif /* CONFIG_SMP */

#if defined(CONFIG_ALTIVEC) && !defined(CONFIG_SMP)
	/* Avoid the trap.  On smp this this never happens since
	 * we don't set last_task_used_altivec -- Cort
	 */
	if (new->thread.regs && last_task_used_altivec == new)
		new->thread.regs->msr |= MSR_VEC;
#endif /* CONFIG_ALTIVEC */

	if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr)) {
		set_dabr(new->thread.dabr);
		__get_cpu_var(current_dabr) = new->thread.dabr;
	}

	flush_tlb_pending();

	new_thread = &new->thread;
	old_thread = &current->thread;

	/* Collect purr utilization data per process and per processor
	 * wise purr is nothing but processor time base
	 */
	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
		struct cpu_usage *cu = &__get_cpu_var(cpu_usage_array);
		long unsigned start_tb, current_tb;
		start_tb = old_thread->start_tb;
		cu->current_tb = current_tb = mfspr(SPRN_PURR);
		old_thread->accum_tb += (current_tb - start_tb);
		new_thread->start_tb = current_tb;
	}

	local_irq_save(flags);
	last = _switch(old_thread, new_thread);

	local_irq_restore(flags);

	return last;
}

static int instructions_to_print = 16;

static void show_instructions(struct pt_regs *regs)
{
	int i;
	unsigned long pc = regs->nip - (instructions_to_print * 3 / 4 *
			sizeof(int));

	printk("Instruction dump:");

	for (i = 0; i < instructions_to_print; i++) {
		int instr;

		if (!(i % 8))
			printk("\n");

		if (((REGION_ID(pc) != KERNEL_REGION_ID) &&
		     (REGION_ID(pc) != VMALLOC_REGION_ID)) ||
		     __get_user(instr, (unsigned int *)pc)) {
			printk("XXXXXXXX ");
		} else {
			if (regs->nip == pc)
				printk("<%08x> ", instr);
			else
				printk("%08x ", instr);
		}

		pc += sizeof(int);
	}

	printk("\n");
}

void show_regs(struct pt_regs * regs)
{
	int i;
	unsigned long trap;

	printk("NIP: %016lX XER: %08X LR: %016lX CTR: %016lX\n",
	       regs->nip, (unsigned int)regs->xer, regs->link, regs->ctr);
	printk("REGS: %p TRAP: %04lx   %s  (%s)\n",
	       regs, regs->trap, print_tainted(), system_utsname.release);
	printk("MSR: %016lx EE: %01x PR: %01x FP: %01x ME: %01x "
	       "IR/DR: %01x%01x CR: %08X\n",
	       regs->msr, regs->msr&MSR_EE ? 1 : 0, regs->msr&MSR_PR ? 1 : 0,
	       regs->msr & MSR_FP ? 1 : 0,regs->msr&MSR_ME ? 1 : 0,
	       regs->msr&MSR_IR ? 1 : 0,
	       regs->msr&MSR_DR ? 1 : 0,
	       (unsigned int)regs->ccr);
	trap = TRAP(regs);
	printk("DAR: %016lx DSISR: %016lx\n", regs->dar, regs->dsisr);
	printk("TASK: %p[%d] '%s' THREAD: %p",
	       current, current->pid, current->comm, current->thread_info);

#ifdef CONFIG_SMP
	printk(" CPU: %d", smp_processor_id());
#endif /* CONFIG_SMP */

	for (i = 0; i < 32; i++) {
		if ((i % 4) == 0) {
			printk("\n" KERN_INFO "GPR%02d: ", i);
		}

		printk("%016lX ", regs->gpr[i]);
		if (i == 13 && !FULL_REGS(regs))
			break;
	}
	printk("\n");
	/*
	 * Lookup NIP late so we have the best change of getting the
	 * above info out without failing
	 */
	printk("NIP [%016lx] ", regs->nip);
	print_symbol("%s\n", regs->nip);
	printk("LR [%016lx] ", regs->link);
	print_symbol("%s\n", regs->link);
	show_stack(current, (unsigned long *)regs->gpr[1]);
	if (!user_mode(regs))
		show_instructions(regs);
}

void exit_thread(void)
{
	kprobe_flush_task(current);

#ifndef CONFIG_SMP
	if (last_task_used_math == current)
		last_task_used_math = NULL;
#ifdef CONFIG_ALTIVEC
	if (last_task_used_altivec == current)
		last_task_used_altivec = NULL;
#endif /* CONFIG_ALTIVEC */
#endif /* CONFIG_SMP */
}

void flush_thread(void)
{
	struct thread_info *t = current_thread_info();

	kprobe_flush_task(current);
	if (t->flags & _TIF_ABI_PENDING)
		t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT);

#ifndef CONFIG_SMP
	if (last_task_used_math == current)
		last_task_used_math = NULL;
#ifdef CONFIG_ALTIVEC
	if (last_task_used_altivec == current)
		last_task_used_altivec = NULL;
#endif /* CONFIG_ALTIVEC */
#endif /* CONFIG_SMP */

	if (current->thread.dabr) {
		current->thread.dabr = 0;
		set_dabr(0);
	}
}

void
release_thread(struct task_struct *t)
{
}


/*
 * This gets called before we allocate a new thread and copy
 * the current task into it.
 */
void prepare_to_copy(struct task_struct *tsk)
{
	flush_fp_to_thread(current);
	flush_altivec_to_thread(current);
}

/*
 * Copy a thread..
 */
int
copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
	    unsigned long unused, struct task_struct *p, struct pt_regs *regs)
{
	struct pt_regs *childregs, *kregs;
	extern void ret_from_fork(void);
	unsigned long sp = (unsigned long)p->thread_info + THREAD_SIZE;

	/* Copy registers */
	sp -= sizeof(struct pt_regs);
	childregs = (struct pt_regs *) sp;
	*childregs = *regs;
	if ((childregs->msr & MSR_PR) == 0) {
		/* for kernel thread, set stackptr in new task */
		childregs->gpr[1] = sp + sizeof(struct pt_regs);
		p->thread.regs = NULL;	/* no user register state */
		clear_ti_thread_flag(p->thread_info, TIF_32BIT);
	} else {
		childregs->gpr[1] = usp;
		p->thread.regs = childregs;
		if (clone_flags & CLONE_SETTLS) {
			if (test_thread_flag(TIF_32BIT))
				childregs->gpr[2] = childregs->gpr[6];
			else
				childregs->gpr[13] = childregs->gpr[6];
		}
	}
	childregs->gpr[3] = 0;  /* Result from fork() */
	sp -= STACK_FRAME_OVERHEAD;

	/*
	 * The way this works is that at some point in the future
	 * some task will call _switch to switch to the new task.
	 * That will pop off the stack frame created below and start
	 * the new task running at ret_from_fork.  The new task will
	 * do some house keeping and then return from the fork or clone
	 * system call, using the stack frame created above.
	 */
	sp -= sizeof(struct pt_regs);
	kregs = (struct pt_regs *) sp;
	sp -= STACK_FRAME_OVERHEAD;
	p->thread.ksp = sp;
	if (cpu_has_feature(CPU_FTR_SLB)) {
		unsigned long sp_vsid = get_kernel_vsid(sp);

		sp_vsid <<= SLB_VSID_SHIFT;
		sp_vsid |= SLB_VSID_KERNEL;
		if (cpu_has_feature(CPU_FTR_16M_PAGE))
			sp_vsid |= SLB_VSID_L;

		p->thread.ksp_vsid = sp_vsid;
	}

	/*
	 * The PPC64 ABI makes use of a TOC to contain function 
	 * pointers.  The function (ret_from_except) is actually a pointer
	 * to the TOC entry.  The first entry is a pointer to the actual
	 * function.
 	 */
	kregs->nip = *((unsigned long *)ret_from_fork);

	return 0;
}

/*
 * Set up a thread for executing a new program
 */
void start_thread(struct pt_regs *regs, unsigned long fdptr, unsigned long sp)
{
	unsigned long entry, toc, load_addr = regs->gpr[2];

	/* fdptr is a relocated pointer to the function descriptor for
         * the elf _start routine.  The first entry in the function
         * descriptor is the entry address of _start and the second
         * entry is the TOC value we need to use.
         */
	set_fs(USER_DS);
	__get_user(entry, (unsigned long __user *)fdptr);
	__get_user(toc, (unsigned long __user *)fdptr+1);

	/* Check whether the e_entry function descriptor entries
	 * need to be relocated before we can use them.
	 */
	if (load_addr != 0) {
		entry += load_addr;
		toc   += load_addr;
	}

	/*
	 * If we exec out of a kernel thread then thread.regs will not be
	 * set. Do it now.
	 */
	if (!current->thread.regs) {
		unsigned long childregs = (unsigned long)current->thread_info +
						THREAD_SIZE;
		childregs -= sizeof(struct pt_regs);
		current->thread.regs = (struct pt_regs *)childregs;
	}

	regs->nip = entry;
	regs->gpr[1] = sp;
	regs->gpr[2] = toc;
	regs->msr = MSR_USER64;
#ifndef CONFIG_SMP
	if (last_task_used_math == current)
		last_task_used_math = 0;
#endif /* CONFIG_SMP */
	memset(current->thread.fpr, 0, sizeof(current->thread.fpr));
	current->thread.fpscr = 0;
#ifdef CONFIG_ALTIVEC
#ifndef CONFIG_SMP
	if (last_task_used_altivec == current)
		last_task_used_altivec = 0;
#endif /* CONFIG_SMP */
	memset(current->thread.vr, 0, sizeof(current->thread.vr));
	current->thread.vscr.u[0] = 0;
	current->thread.vscr.u[1] = 0;
	current->thread.vscr.u[2] = 0;
	current->thread.vscr.u[3] = 0x00010000; /* Java mode disabled */
	current->thread.vrsave = 0;
	current->thread.used_vr = 0;
#endif /* CONFIG_ALTIVEC */
}
EXPORT_SYMBOL(start_thread);

int set_fpexc_mode(struct task_struct *tsk, unsigned int val)
{
	struct pt_regs *regs = tsk->thread.regs;

	if (val > PR_FP_EXC_PRECISE)
		return -EINVAL;
	tsk->thread.fpexc_mode = __pack_fe01(val);
	if (regs != NULL && (regs->msr & MSR_FP) != 0)
		regs->msr = (regs->msr & ~(MSR_FE0|MSR_FE1))
			| tsk->thread.fpexc_mode;
	return 0;
}

int get_fpexc_mode(struct task_struct *tsk, unsigned long adr)
{
	unsigned int val;

	val = __unpack_fe01(tsk->thread.fpexc_mode);
	return put_user(val, (unsigned int __user *) adr);
}

int sys_clone(unsigned long clone_flags, unsigned long p2, unsigned long p3,
	      unsigned long p4, unsigned long p5, unsigned long p6,
	      struct pt_regs *regs)
{
	unsigned long parent_tidptr = 0;
	unsigned long child_tidptr = 0;

	if (p2 == 0)
		p2 = regs->gpr[1];	/* stack pointer for child */

	if (clone_flags & (CLONE_PARENT_SETTID | CLONE_CHILD_SETTID |
			   CLONE_CHILD_CLEARTID)) {
		parent_tidptr = p3;
		child_tidptr = p5;
		if (test_thread_flag(TIF_32BIT)) {
			parent_tidptr &= 0xffffffff;
			child_tidptr &= 0xffffffff;
		}
	}

	return do_fork(clone_flags, p2, regs, 0,
		    (int __user *)parent_tidptr, (int __user *)child_tidptr);
}

int sys_fork(unsigned long p1, unsigned long p2, unsigned long p3,
	     unsigned long p4, unsigned long p5, unsigned long p6,
	     struct pt_regs *regs)
{
	return do_fork(SIGCHLD, regs->gpr[1], regs, 0, NULL, NULL);
}

int sys_vfork(unsigned long p1, unsigned long p2, unsigned long p3,
	      unsigned long p4, unsigned long p5, unsigned long p6,
	      struct pt_regs *regs)
{
	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->gpr[1], regs, 0,
	            NULL, NULL);
}

int sys_execve(unsigned long a0, unsigned long a1, unsigned long a2,
	       unsigned long a3, unsigned long a4, unsigned long a5,
	       struct pt_regs *regs)
{
	int error;
	char * filename;
	
	filename = getname((char __user *) a0);
	error = PTR_ERR(filename);
	if (IS_ERR(filename))
		goto out;
	flush_fp_to_thread(current);
	flush_altivec_to_thread(current);
	error = do_execve(filename, (char __user * __user *) a1,
				    (char __user * __user *) a2, regs);
  
	if (error == 0) {
		task_lock(current);
		current->ptrace &= ~PT_DTRACE;
		task_unlock(current);
	}
	putname(filename);

out:
	return error;
}

static int kstack_depth_to_print = 64;

static int validate_sp(unsigned long sp, struct task_struct *p,
		       unsigned long nbytes)
{
	unsigned long stack_page = (unsigned long)p->thread_info;

	if (sp >= stack_page + sizeof(struct thread_struct)
	    && sp <= stack_page + THREAD_SIZE - nbytes)
		return 1;

#ifdef CONFIG_IRQSTACKS
	stack_page = (unsigned long) hardirq_ctx[task_cpu(p)];
	if (sp >= stack_page + sizeof(struct thread_struct)
	    && sp <= stack_page + THREAD_SIZE - nbytes)
		return 1;

	stack_page = (unsigned long) softirq_ctx[task_cpu(p)];
	if (sp >= stack_page + sizeof(struct thread_struct)
	    && sp <= stack_page + THREAD_SIZE - nbytes)
		return 1;
#endif

	return 0;
}

unsigned long get_wchan(struct task_struct *p)
{
	unsigned long ip, sp;
	int count = 0;

	if (!p || p == current || p->state == TASK_RUNNING)
		return 0;

	sp = p->thread.ksp;
	if (!validate_sp(sp, p, 112))
		return 0;

	do {
		sp = *(unsigned long *)sp;
		if (!validate_sp(sp, p, 112))
			return 0;
		if (count > 0) {
			ip = *(unsigned long *)(sp + 16);
			if (!in_sched_functions(ip))
				return ip;
		}
	} while (count++ < 16);
	return 0;
}
EXPORT_SYMBOL(get_wchan);

void show_stack(struct task_struct *p, unsigned long *_sp)
{
	unsigned long ip, newsp, lr;
	int count = 0;
	unsigned long sp = (unsigned long)_sp;
	int firstframe = 1;

	if (sp == 0) {
		if (p) {
			sp = p->thread.ksp;
		} else {
			sp = __get_SP();
			p = current;
		}
	}

	lr = 0;
	printk("Call Trace:\n");
	do {
		if (!validate_sp(sp, p, 112))
			return;

		_sp = (unsigned long *) sp;
		newsp = _sp[0];
		ip = _sp[2];
		if (!firstframe || ip != lr) {
			printk("[%016lx] [%016lx] ", sp, ip);
			print_symbol("%s", ip);
			if (firstframe)
				printk(" (unreliable)");
			printk("\n");
		}
		firstframe = 0;

		/*
		 * See if this is an exception frame.
		 * We look for the "regshere" marker in the current frame.
		 */
		if (validate_sp(sp, p, sizeof(struct pt_regs) + 400)
		    && _sp[12] == 0x7265677368657265ul) {
			struct pt_regs *regs = (struct pt_regs *)
				(sp + STACK_FRAME_OVERHEAD);
			printk("--- Exception: %lx", regs->trap);
			print_symbol(" at %s\n", regs->nip);
			lr = regs->link;
			print_symbol("    LR = %s\n", lr);
			firstframe = 1;
		}

		sp = newsp;
	} while (count++ < kstack_depth_to_print);
}

void dump_stack(void)
{
	show_stack(current, (unsigned long *)__get_SP());
}
EXPORT_SYMBOL(dump_stack);