aboutsummaryrefslogtreecommitdiff
path: root/arch/mips/kernel/process.c
blob: c558bce989cd386c940d3f1338f5ae2ec2516760 (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
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
 * Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 * Copyright (C) 2004 Thiemo Seufer
 * Copyright (C) 2013  Imagination Technologies Ltd.
 */
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/tick.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/export.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/personality.h>
#include <linux/sys.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
#include <linux/random.h>
#include <linux/prctl.h>

#include <asm/asm.h>
#include <asm/bootinfo.h>
#include <asm/cpu.h>
#include <asm/dsemul.h>
#include <asm/dsp.h>
#include <asm/fpu.h>
#include <asm/irq.h>
#include <asm/msa.h>
#include <asm/pgtable.h>
#include <asm/mipsregs.h>
#include <asm/processor.h>
#include <asm/reg.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/elf.h>
#include <asm/isadep.h>
#include <asm/inst.h>
#include <asm/stacktrace.h>
#include <asm/irq_regs.h>

#ifdef CONFIG_HOTPLUG_CPU
void arch_cpu_idle_dead(void)
{
	play_dead();
}
#endif

asmlinkage void ret_from_fork(void);
asmlinkage void ret_from_kernel_thread(void);

void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
{
	unsigned long status;

	/* New thread loses kernel privileges. */
	status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
	status |= KU_USER;
	regs->cp0_status = status;
	lose_fpu(0);
	clear_thread_flag(TIF_MSA_CTX_LIVE);
	clear_used_math();
	atomic_set(&current->thread.bd_emu_frame, BD_EMUFRAME_NONE);
	init_dsp();
	regs->cp0_epc = pc;
	regs->regs[29] = sp;
}

void exit_thread(struct task_struct *tsk)
{
	/*
	 * User threads may have allocated a delay slot emulation frame.
	 * If so, clean up that allocation.
	 */
	if (!(current->flags & PF_KTHREAD))
		dsemul_thread_cleanup(tsk);
}

int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
	/*
	 * Save any process state which is live in hardware registers to the
	 * parent context prior to duplication. This prevents the new child
	 * state becoming stale if the parent is preempted before copy_thread()
	 * gets a chance to save the parent's live hardware registers to the
	 * child context.
	 */
	preempt_disable();

	if (is_msa_enabled())
		save_msa(current);
	else if (is_fpu_owner())
		_save_fp(current);

	save_dsp(current);

	preempt_enable();

	*dst = *src;
	return 0;
}

/*
 * Copy architecture-specific thread state
 */
int copy_thread(unsigned long clone_flags, unsigned long usp,
	unsigned long kthread_arg, struct task_struct *p)
{
	struct thread_info *ti = task_thread_info(p);
	struct pt_regs *childregs, *regs = current_pt_regs();
	unsigned long childksp;
	p->set_child_tid = p->clear_child_tid = NULL;

	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;

	/* set up new TSS. */
	childregs = (struct pt_regs *) childksp - 1;
	/*  Put the stack after the struct pt_regs.  */
	childksp = (unsigned long) childregs;
	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
	if (unlikely(p->flags & PF_KTHREAD)) {
		/* kernel thread */
		unsigned long status = p->thread.cp0_status;
		memset(childregs, 0, sizeof(struct pt_regs));
		ti->addr_limit = KERNEL_DS;
		p->thread.reg16 = usp; /* fn */
		p->thread.reg17 = kthread_arg;
		p->thread.reg29 = childksp;
		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
		status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
			 ((status & (ST0_KUC | ST0_IEC)) << 2);
#else
		status |= ST0_EXL;
#endif
		childregs->cp0_status = status;
		return 0;
	}

	/* user thread */
	*childregs = *regs;
	childregs->regs[7] = 0; /* Clear error flag */
	childregs->regs[2] = 0; /* Child gets zero as return value */
	if (usp)
		childregs->regs[29] = usp;
	ti->addr_limit = USER_DS;

	p->thread.reg29 = (unsigned long) childregs;
	p->thread.reg31 = (unsigned long) ret_from_fork;

	/*
	 * New tasks lose permission to use the fpu. This accelerates context
	 * switching for most programs since they don't use the fpu.
	 */
	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);

	clear_tsk_thread_flag(p, TIF_USEDFPU);
	clear_tsk_thread_flag(p, TIF_USEDMSA);
	clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);

#ifdef CONFIG_MIPS_MT_FPAFF
	clear_tsk_thread_flag(p, TIF_FPUBOUND);
#endif /* CONFIG_MIPS_MT_FPAFF */

	atomic_set(&p->thread.bd_emu_frame, BD_EMUFRAME_NONE);

	if (clone_flags & CLONE_SETTLS)
		ti->tp_value = regs->regs[7];

	return 0;
}

#ifdef CONFIG_CC_STACKPROTECTOR
#include <linux/stackprotector.h>
unsigned long __stack_chk_guard __read_mostly;
EXPORT_SYMBOL(__stack_chk_guard);
#endif

struct mips_frame_info {
	void		*func;
	unsigned long	func_size;
	int		frame_size;
	int		pc_offset;
};

#define J_TARGET(pc,target)	\
		(((unsigned long)(pc) & 0xf0000000) | ((target) << 2))

static inline int is_ra_save_ins(union mips_instruction *ip, int *poff)
{
#ifdef CONFIG_CPU_MICROMIPS
	/*
	 * swsp ra,offset
	 * swm16 reglist,offset(sp)
	 * swm32 reglist,offset(sp)
	 * sw32 ra,offset(sp)
	 * jradiussp - NOT SUPPORTED
	 *
	 * microMIPS is way more fun...
	 */
	if (mm_insn_16bit(ip->halfword[1])) {
		switch (ip->mm16_r5_format.opcode) {
		case mm_swsp16_op:
			if (ip->mm16_r5_format.rt != 31)
				return 0;

			*poff = ip->mm16_r5_format.simmediate;
			*poff = (*poff << 2) / sizeof(ulong);
			return 1;

		case mm_pool16c_op:
			switch (ip->mm16_m_format.func) {
			case mm_swm16_op:
				*poff = ip->mm16_m_format.imm;
				*poff += 1 + ip->mm16_m_format.rlist;
				*poff = (*poff << 2) / sizeof(ulong);
				return 1;

			default:
				return 0;
			}

		default:
			return 0;
		}
	}

	switch (ip->i_format.opcode) {
	case mm_sw32_op:
		if (ip->i_format.rs != 29)
			return 0;
		if (ip->i_format.rt != 31)
			return 0;

		*poff = ip->i_format.simmediate / sizeof(ulong);
		return 1;

	case mm_pool32b_op:
		switch (ip->mm_m_format.func) {
		case mm_swm32_func:
			if (ip->mm_m_format.rd < 0x10)
				return 0;
			if (ip->mm_m_format.base != 29)
				return 0;

			*poff = ip->mm_m_format.simmediate;
			*poff += (ip->mm_m_format.rd & 0xf) * sizeof(u32);
			*poff /= sizeof(ulong);
			return 1;
		default:
			return 0;
		}

	default:
		return 0;
	}
#else
	/* sw / sd $ra, offset($sp) */
	if ((ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
		ip->i_format.rs == 29 && ip->i_format.rt == 31) {
		*poff = ip->i_format.simmediate / sizeof(ulong);
		return 1;
	}

	return 0;
#endif
}

static inline int is_jump_ins(union mips_instruction *ip)
{
#ifdef CONFIG_CPU_MICROMIPS
	/*
	 * jr16,jrc,jalr16,jalr16
	 * jal
	 * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
	 * jraddiusp - NOT SUPPORTED
	 *
	 * microMIPS is kind of more fun...
	 */
	if (mm_insn_16bit(ip->halfword[1])) {
		if ((ip->mm16_r5_format.opcode == mm_pool16c_op &&
		    (ip->mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op))
			return 1;
		return 0;
	}

	if (ip->j_format.opcode == mm_j32_op)
		return 1;
	if (ip->j_format.opcode == mm_jal32_op)
		return 1;
	if (ip->r_format.opcode != mm_pool32a_op ||
			ip->r_format.func != mm_pool32axf_op)
		return 0;
	return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
#else
	if (ip->j_format.opcode == j_op)
		return 1;
	if (ip->j_format.opcode == jal_op)
		return 1;
	if (ip->r_format.opcode != spec_op)
		return 0;
	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
#endif
}

static inline int is_sp_move_ins(union mips_instruction *ip)
{
#ifdef CONFIG_CPU_MICROMIPS
	/*
	 * addiusp -imm
	 * addius5 sp,-imm
	 * addiu32 sp,sp,-imm
	 * jradiussp - NOT SUPPORTED
	 *
	 * microMIPS is not more fun...
	 */
	if (mm_insn_16bit(ip->halfword[1])) {
		return (ip->mm16_r3_format.opcode == mm_pool16d_op &&
			ip->mm16_r3_format.simmediate && mm_addiusp_func) ||
		       (ip->mm16_r5_format.opcode == mm_pool16d_op &&
			ip->mm16_r5_format.rt == 29);
	}

	return ip->mm_i_format.opcode == mm_addiu32_op &&
	       ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
#else
	/* addiu/daddiu sp,sp,-imm */
	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
		return 0;
	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
		return 1;
#endif
	return 0;
}

static int get_frame_info(struct mips_frame_info *info)
{
	bool is_mmips = IS_ENABLED(CONFIG_CPU_MICROMIPS);
	union mips_instruction insn, *ip, *ip_end;
	const unsigned int max_insns = 128;
	unsigned int i;

	info->pc_offset = -1;
	info->frame_size = 0;

	ip = (void *)msk_isa16_mode((ulong)info->func);
	if (!ip)
		goto err;

	ip_end = (void *)ip + info->func_size;

	for (i = 0; i < max_insns && ip < ip_end; i++, ip++) {
		if (is_mmips && mm_insn_16bit(ip->halfword[0])) {
			insn.halfword[0] = 0;
			insn.halfword[1] = ip->halfword[0];
		} else if (is_mmips) {
			insn.halfword[0] = ip->halfword[1];
			insn.halfword[1] = ip->halfword[0];
		} else {
			insn.word = ip->word;
		}

		if (is_jump_ins(&insn))
			break;

		if (!info->frame_size) {
			if (is_sp_move_ins(&insn))
			{
#ifdef CONFIG_CPU_MICROMIPS
				if (mm_insn_16bit(ip->halfword[0]))
				{
					unsigned short tmp;

					if (ip->halfword[0] & mm_addiusp_func)
					{
						tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
						info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
					} else {
						tmp = (ip->halfword[0] >> 1);
						info->frame_size = -(signed short)(tmp & 0xf);
					}
					ip = (void *) &ip->halfword[1];
					ip--;
				} else
#endif
				info->frame_size = - ip->i_format.simmediate;
			}
			continue;
		}
		if (info->pc_offset == -1 &&
		    is_ra_save_ins(&insn, &info->pc_offset))
			break;
	}
	if (info->frame_size && info->pc_offset >= 0) /* nested */
		return 0;
	if (info->pc_offset < 0) /* leaf */
		return 1;
	/* prologue seems bogus... */
err:
	return -1;
}

static struct mips_frame_info schedule_mfi __read_mostly;

#ifdef CONFIG_KALLSYMS
static unsigned long get___schedule_addr(void)
{
	return kallsyms_lookup_name("__schedule");
}
#else
static unsigned long get___schedule_addr(void)
{
	union mips_instruction *ip = (void *)schedule;
	int max_insns = 8;
	int i;

	for (i = 0; i < max_insns; i++, ip++) {
		if (ip->j_format.opcode == j_op)
			return J_TARGET(ip, ip->j_format.target);
	}
	return 0;
}
#endif

static int __init frame_info_init(void)
{
	unsigned long size = 0;
#ifdef CONFIG_KALLSYMS
	unsigned long ofs;
#endif
	unsigned long addr;

	addr = get___schedule_addr();
	if (!addr)
		addr = (unsigned long)schedule;

#ifdef CONFIG_KALLSYMS
	kallsyms_lookup_size_offset(addr, &size, &ofs);
#endif
	schedule_mfi.func = (void *)addr;
	schedule_mfi.func_size = size;

	get_frame_info(&schedule_mfi);

	/*
	 * Without schedule() frame info, result given by
	 * thread_saved_pc() and get_wchan() are not reliable.
	 */
	if (schedule_mfi.pc_offset < 0)
		printk("Can't analyze schedule() prologue at %p\n", schedule);

	return 0;
}

arch_initcall(frame_info_init);

/*
 * Return saved PC of a blocked thread.
 */
unsigned long thread_saved_pc(struct task_struct *tsk)
{
	struct thread_struct *t = &tsk->thread;

	/* New born processes are a special case */
	if (t->reg31 == (unsigned long) ret_from_fork)
		return t->reg31;
	if (schedule_mfi.pc_offset < 0)
		return 0;
	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
}


#ifdef CONFIG_KALLSYMS
/* generic stack unwinding function */
unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
					      unsigned long *sp,
					      unsigned long pc,
					      unsigned long *ra)
{
	unsigned long low, high, irq_stack_high;
	struct mips_frame_info info;
	unsigned long size, ofs;
	struct pt_regs *regs;
	int leaf;

	if (!stack_page)
		return 0;

	/*
	 * IRQ stacks start at IRQ_STACK_START
	 * task stacks at THREAD_SIZE - 32
	 */
	low = stack_page;
	if (!preemptible() && on_irq_stack(raw_smp_processor_id(), *sp)) {
		high = stack_page + IRQ_STACK_START;
		irq_stack_high = high;
	} else {
		high = stack_page + THREAD_SIZE - 32;
		irq_stack_high = 0;
	}

	/*
	 * If we reached the top of the interrupt stack, start unwinding
	 * the interrupted task stack.
	 */
	if (unlikely(*sp == irq_stack_high)) {
		unsigned long task_sp = *(unsigned long *)*sp;

		/*
		 * Check that the pointer saved in the IRQ stack head points to
		 * something within the stack of the current task
		 */
		if (!object_is_on_stack((void *)task_sp))
			return 0;

		/*
		 * Follow pointer to tasks kernel stack frame where interrupted
		 * state was saved.
		 */
		regs = (struct pt_regs *)task_sp;
		pc = regs->cp0_epc;
		if (!user_mode(regs) && __kernel_text_address(pc)) {
			*sp = regs->regs[29];
			*ra = regs->regs[31];
			return pc;
		}
		return 0;
	}
	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
		return 0;
	/*
	 * Return ra if an exception occurred at the first instruction
	 */
	if (unlikely(ofs == 0)) {
		pc = *ra;
		*ra = 0;
		return pc;
	}

	info.func = (void *)(pc - ofs);
	info.func_size = ofs;	/* analyze from start to ofs */
	leaf = get_frame_info(&info);
	if (leaf < 0)
		return 0;

	if (*sp < low || *sp + info.frame_size > high)
		return 0;

	if (leaf)
		/*
		 * For some extreme cases, get_frame_info() can
		 * consider wrongly a nested function as a leaf
		 * one. In that cases avoid to return always the
		 * same value.
		 */
		pc = pc != *ra ? *ra : 0;
	else
		pc = ((unsigned long *)(*sp))[info.pc_offset];

	*sp += info.frame_size;
	*ra = 0;
	return __kernel_text_address(pc) ? pc : 0;
}
EXPORT_SYMBOL(unwind_stack_by_address);

/* used by show_backtrace() */
unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
			   unsigned long pc, unsigned long *ra)
{
	unsigned long stack_page = 0;
	int cpu;

	for_each_possible_cpu(cpu) {
		if (on_irq_stack(cpu, *sp)) {
			stack_page = (unsigned long)irq_stack[cpu];
			break;
		}
	}

	if (!stack_page)
		stack_page = (unsigned long)task_stack_page(task);

	return unwind_stack_by_address(stack_page, sp, pc, ra);
}
#endif

/*
 * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 */
unsigned long get_wchan(struct task_struct *task)
{
	unsigned long pc = 0;
#ifdef CONFIG_KALLSYMS
	unsigned long sp;
	unsigned long ra = 0;
#endif

	if (!task || task == current || task->state == TASK_RUNNING)
		goto out;
	if (!task_stack_page(task))
		goto out;

	pc = thread_saved_pc(task);

#ifdef CONFIG_KALLSYMS
	sp = task->thread.reg29 + schedule_mfi.frame_size;

	while (in_sched_functions(pc))
		pc = unwind_stack(task, &sp, pc, &ra);
#endif

out:
	return pc;
}

/*
 * Don't forget that the stack pointer must be aligned on a 8 bytes
 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 */
unsigned long arch_align_stack(unsigned long sp)
{
	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
		sp -= get_random_int() & ~PAGE_MASK;

	return sp & ALMASK;
}

static void arch_dump_stack(void *info)
{
	struct pt_regs *regs;

	regs = get_irq_regs();

	if (regs)
		show_regs(regs);

	dump_stack();
}

void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
{
	long this_cpu = get_cpu();

	if (cpumask_test_cpu(this_cpu, mask) && !exclude_self)
		dump_stack();

	smp_call_function_many(mask, arch_dump_stack, NULL, 1);

	put_cpu();
}

int mips_get_process_fp_mode(struct task_struct *task)
{
	int value = 0;

	if (!test_tsk_thread_flag(task, TIF_32BIT_FPREGS))
		value |= PR_FP_MODE_FR;
	if (test_tsk_thread_flag(task, TIF_HYBRID_FPREGS))
		value |= PR_FP_MODE_FRE;

	return value;
}

static void prepare_for_fp_mode_switch(void *info)
{
	struct mm_struct *mm = info;

	if (current->mm == mm)
		lose_fpu(1);
}

int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)
{
	const unsigned int known_bits = PR_FP_MODE_FR | PR_FP_MODE_FRE;
	struct task_struct *t;
	int max_users;

	/* Check the value is valid */
	if (value & ~known_bits)
		return -EOPNOTSUPP;

	/* Avoid inadvertently triggering emulation */
	if ((value & PR_FP_MODE_FR) && raw_cpu_has_fpu &&
	    !(raw_current_cpu_data.fpu_id & MIPS_FPIR_F64))
		return -EOPNOTSUPP;
	if ((value & PR_FP_MODE_FRE) && raw_cpu_has_fpu && !cpu_has_fre)
		return -EOPNOTSUPP;

	/* FR = 0 not supported in MIPS R6 */
	if (!(value & PR_FP_MODE_FR) && raw_cpu_has_fpu && cpu_has_mips_r6)
		return -EOPNOTSUPP;

	/* Proceed with the mode switch */
	preempt_disable();

	/* Save FP & vector context, then disable FPU & MSA */
	if (task->signal == current->signal)
		lose_fpu(1);

	/* Prevent any threads from obtaining live FP context */
	atomic_set(&task->mm->context.fp_mode_switching, 1);
	smp_mb__after_atomic();

	/*
	 * If there are multiple online CPUs then force any which are running
	 * threads in this process to lose their FPU context, which they can't
	 * regain until fp_mode_switching is cleared later.
	 */
	if (num_online_cpus() > 1) {
		/* No need to send an IPI for the local CPU */
		max_users = (task->mm == current->mm) ? 1 : 0;

		if (atomic_read(&current->mm->mm_users) > max_users)
			smp_call_function(prepare_for_fp_mode_switch,
					  (void *)current->mm, 1);
	}

	/*
	 * There are now no threads of the process with live FP context, so it
	 * is safe to proceed with the FP mode switch.
	 */
	for_each_thread(task, t) {
		/* Update desired FP register width */
		if (value & PR_FP_MODE_FR) {
			clear_tsk_thread_flag(t, TIF_32BIT_FPREGS);
		} else {
			set_tsk_thread_flag(t, TIF_32BIT_FPREGS);
			clear_tsk_thread_flag(t, TIF_MSA_CTX_LIVE);
		}

		/* Update desired FP single layout */
		if (value & PR_FP_MODE_FRE)
			set_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
		else
			clear_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
	}

	/* Allow threads to use FP again */
	atomic_set(&task->mm->context.fp_mode_switching, 0);
	preempt_enable();

	return 0;
}