xref: /openbmc/linux/arch/mips/kernel/process.c (revision 174cd4b1)
1 /*
2  * This file is subject to the terms and conditions of the GNU General Public
3  * License.  See the file "COPYING" in the main directory of this archive
4  * for more details.
5  *
6  * Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
7  * Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
8  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
9  * Copyright (C) 2004 Thiemo Seufer
10  * Copyright (C) 2013  Imagination Technologies Ltd.
11  */
12 #include <linux/errno.h>
13 #include <linux/sched.h>
14 #include <linux/tick.h>
15 #include <linux/kernel.h>
16 #include <linux/mm.h>
17 #include <linux/stddef.h>
18 #include <linux/unistd.h>
19 #include <linux/export.h>
20 #include <linux/ptrace.h>
21 #include <linux/mman.h>
22 #include <linux/personality.h>
23 #include <linux/sys.h>
24 #include <linux/init.h>
25 #include <linux/completion.h>
26 #include <linux/kallsyms.h>
27 #include <linux/random.h>
28 #include <linux/prctl.h>
29 
30 #include <asm/asm.h>
31 #include <asm/bootinfo.h>
32 #include <asm/cpu.h>
33 #include <asm/dsemul.h>
34 #include <asm/dsp.h>
35 #include <asm/fpu.h>
36 #include <asm/irq.h>
37 #include <asm/msa.h>
38 #include <asm/pgtable.h>
39 #include <asm/mipsregs.h>
40 #include <asm/processor.h>
41 #include <asm/reg.h>
42 #include <linux/uaccess.h>
43 #include <asm/io.h>
44 #include <asm/elf.h>
45 #include <asm/isadep.h>
46 #include <asm/inst.h>
47 #include <asm/stacktrace.h>
48 #include <asm/irq_regs.h>
49 
50 #ifdef CONFIG_HOTPLUG_CPU
51 void arch_cpu_idle_dead(void)
52 {
53 	play_dead();
54 }
55 #endif
56 
57 asmlinkage void ret_from_fork(void);
58 asmlinkage void ret_from_kernel_thread(void);
59 
60 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
61 {
62 	unsigned long status;
63 
64 	/* New thread loses kernel privileges. */
65 	status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
66 	status |= KU_USER;
67 	regs->cp0_status = status;
68 	lose_fpu(0);
69 	clear_thread_flag(TIF_MSA_CTX_LIVE);
70 	clear_used_math();
71 	atomic_set(&current->thread.bd_emu_frame, BD_EMUFRAME_NONE);
72 	init_dsp();
73 	regs->cp0_epc = pc;
74 	regs->regs[29] = sp;
75 }
76 
77 void exit_thread(struct task_struct *tsk)
78 {
79 	/*
80 	 * User threads may have allocated a delay slot emulation frame.
81 	 * If so, clean up that allocation.
82 	 */
83 	if (!(current->flags & PF_KTHREAD))
84 		dsemul_thread_cleanup(tsk);
85 }
86 
87 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
88 {
89 	/*
90 	 * Save any process state which is live in hardware registers to the
91 	 * parent context prior to duplication. This prevents the new child
92 	 * state becoming stale if the parent is preempted before copy_thread()
93 	 * gets a chance to save the parent's live hardware registers to the
94 	 * child context.
95 	 */
96 	preempt_disable();
97 
98 	if (is_msa_enabled())
99 		save_msa(current);
100 	else if (is_fpu_owner())
101 		_save_fp(current);
102 
103 	save_dsp(current);
104 
105 	preempt_enable();
106 
107 	*dst = *src;
108 	return 0;
109 }
110 
111 /*
112  * Copy architecture-specific thread state
113  */
114 int copy_thread(unsigned long clone_flags, unsigned long usp,
115 	unsigned long kthread_arg, struct task_struct *p)
116 {
117 	struct thread_info *ti = task_thread_info(p);
118 	struct pt_regs *childregs, *regs = current_pt_regs();
119 	unsigned long childksp;
120 	p->set_child_tid = p->clear_child_tid = NULL;
121 
122 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
123 
124 	/* set up new TSS. */
125 	childregs = (struct pt_regs *) childksp - 1;
126 	/*  Put the stack after the struct pt_regs.  */
127 	childksp = (unsigned long) childregs;
128 	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
129 	if (unlikely(p->flags & PF_KTHREAD)) {
130 		/* kernel thread */
131 		unsigned long status = p->thread.cp0_status;
132 		memset(childregs, 0, sizeof(struct pt_regs));
133 		ti->addr_limit = KERNEL_DS;
134 		p->thread.reg16 = usp; /* fn */
135 		p->thread.reg17 = kthread_arg;
136 		p->thread.reg29 = childksp;
137 		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
138 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
139 		status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
140 			 ((status & (ST0_KUC | ST0_IEC)) << 2);
141 #else
142 		status |= ST0_EXL;
143 #endif
144 		childregs->cp0_status = status;
145 		return 0;
146 	}
147 
148 	/* user thread */
149 	*childregs = *regs;
150 	childregs->regs[7] = 0; /* Clear error flag */
151 	childregs->regs[2] = 0; /* Child gets zero as return value */
152 	if (usp)
153 		childregs->regs[29] = usp;
154 	ti->addr_limit = USER_DS;
155 
156 	p->thread.reg29 = (unsigned long) childregs;
157 	p->thread.reg31 = (unsigned long) ret_from_fork;
158 
159 	/*
160 	 * New tasks lose permission to use the fpu. This accelerates context
161 	 * switching for most programs since they don't use the fpu.
162 	 */
163 	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
164 
165 	clear_tsk_thread_flag(p, TIF_USEDFPU);
166 	clear_tsk_thread_flag(p, TIF_USEDMSA);
167 	clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);
168 
169 #ifdef CONFIG_MIPS_MT_FPAFF
170 	clear_tsk_thread_flag(p, TIF_FPUBOUND);
171 #endif /* CONFIG_MIPS_MT_FPAFF */
172 
173 	atomic_set(&p->thread.bd_emu_frame, BD_EMUFRAME_NONE);
174 
175 	if (clone_flags & CLONE_SETTLS)
176 		ti->tp_value = regs->regs[7];
177 
178 	return 0;
179 }
180 
181 #ifdef CONFIG_CC_STACKPROTECTOR
182 #include <linux/stackprotector.h>
183 unsigned long __stack_chk_guard __read_mostly;
184 EXPORT_SYMBOL(__stack_chk_guard);
185 #endif
186 
187 struct mips_frame_info {
188 	void		*func;
189 	unsigned long	func_size;
190 	int		frame_size;
191 	int		pc_offset;
192 };
193 
194 #define J_TARGET(pc,target)	\
195 		(((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
196 
197 static inline int is_ra_save_ins(union mips_instruction *ip, int *poff)
198 {
199 #ifdef CONFIG_CPU_MICROMIPS
200 	/*
201 	 * swsp ra,offset
202 	 * swm16 reglist,offset(sp)
203 	 * swm32 reglist,offset(sp)
204 	 * sw32 ra,offset(sp)
205 	 * jradiussp - NOT SUPPORTED
206 	 *
207 	 * microMIPS is way more fun...
208 	 */
209 	if (mm_insn_16bit(ip->halfword[1])) {
210 		switch (ip->mm16_r5_format.opcode) {
211 		case mm_swsp16_op:
212 			if (ip->mm16_r5_format.rt != 31)
213 				return 0;
214 
215 			*poff = ip->mm16_r5_format.simmediate;
216 			*poff = (*poff << 2) / sizeof(ulong);
217 			return 1;
218 
219 		case mm_pool16c_op:
220 			switch (ip->mm16_m_format.func) {
221 			case mm_swm16_op:
222 				*poff = ip->mm16_m_format.imm;
223 				*poff += 1 + ip->mm16_m_format.rlist;
224 				*poff = (*poff << 2) / sizeof(ulong);
225 				return 1;
226 
227 			default:
228 				return 0;
229 			}
230 
231 		default:
232 			return 0;
233 		}
234 	}
235 
236 	switch (ip->i_format.opcode) {
237 	case mm_sw32_op:
238 		if (ip->i_format.rs != 29)
239 			return 0;
240 		if (ip->i_format.rt != 31)
241 			return 0;
242 
243 		*poff = ip->i_format.simmediate / sizeof(ulong);
244 		return 1;
245 
246 	case mm_pool32b_op:
247 		switch (ip->mm_m_format.func) {
248 		case mm_swm32_func:
249 			if (ip->mm_m_format.rd < 0x10)
250 				return 0;
251 			if (ip->mm_m_format.base != 29)
252 				return 0;
253 
254 			*poff = ip->mm_m_format.simmediate;
255 			*poff += (ip->mm_m_format.rd & 0xf) * sizeof(u32);
256 			*poff /= sizeof(ulong);
257 			return 1;
258 		default:
259 			return 0;
260 		}
261 
262 	default:
263 		return 0;
264 	}
265 #else
266 	/* sw / sd $ra, offset($sp) */
267 	if ((ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
268 		ip->i_format.rs == 29 && ip->i_format.rt == 31) {
269 		*poff = ip->i_format.simmediate / sizeof(ulong);
270 		return 1;
271 	}
272 
273 	return 0;
274 #endif
275 }
276 
277 static inline int is_jump_ins(union mips_instruction *ip)
278 {
279 #ifdef CONFIG_CPU_MICROMIPS
280 	/*
281 	 * jr16,jrc,jalr16,jalr16
282 	 * jal
283 	 * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
284 	 * jraddiusp - NOT SUPPORTED
285 	 *
286 	 * microMIPS is kind of more fun...
287 	 */
288 	if (mm_insn_16bit(ip->halfword[1])) {
289 		if ((ip->mm16_r5_format.opcode == mm_pool16c_op &&
290 		    (ip->mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op))
291 			return 1;
292 		return 0;
293 	}
294 
295 	if (ip->j_format.opcode == mm_j32_op)
296 		return 1;
297 	if (ip->j_format.opcode == mm_jal32_op)
298 		return 1;
299 	if (ip->r_format.opcode != mm_pool32a_op ||
300 			ip->r_format.func != mm_pool32axf_op)
301 		return 0;
302 	return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
303 #else
304 	if (ip->j_format.opcode == j_op)
305 		return 1;
306 	if (ip->j_format.opcode == jal_op)
307 		return 1;
308 	if (ip->r_format.opcode != spec_op)
309 		return 0;
310 	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
311 #endif
312 }
313 
314 static inline int is_sp_move_ins(union mips_instruction *ip)
315 {
316 #ifdef CONFIG_CPU_MICROMIPS
317 	/*
318 	 * addiusp -imm
319 	 * addius5 sp,-imm
320 	 * addiu32 sp,sp,-imm
321 	 * jradiussp - NOT SUPPORTED
322 	 *
323 	 * microMIPS is not more fun...
324 	 */
325 	if (mm_insn_16bit(ip->halfword[1])) {
326 		return (ip->mm16_r3_format.opcode == mm_pool16d_op &&
327 			ip->mm16_r3_format.simmediate && mm_addiusp_func) ||
328 		       (ip->mm16_r5_format.opcode == mm_pool16d_op &&
329 			ip->mm16_r5_format.rt == 29);
330 	}
331 
332 	return ip->mm_i_format.opcode == mm_addiu32_op &&
333 	       ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
334 #else
335 	/* addiu/daddiu sp,sp,-imm */
336 	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
337 		return 0;
338 	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
339 		return 1;
340 #endif
341 	return 0;
342 }
343 
344 static int get_frame_info(struct mips_frame_info *info)
345 {
346 	bool is_mmips = IS_ENABLED(CONFIG_CPU_MICROMIPS);
347 	union mips_instruction insn, *ip, *ip_end;
348 	const unsigned int max_insns = 128;
349 	unsigned int i;
350 
351 	info->pc_offset = -1;
352 	info->frame_size = 0;
353 
354 	ip = (void *)msk_isa16_mode((ulong)info->func);
355 	if (!ip)
356 		goto err;
357 
358 	ip_end = (void *)ip + info->func_size;
359 
360 	for (i = 0; i < max_insns && ip < ip_end; i++, ip++) {
361 		if (is_mmips && mm_insn_16bit(ip->halfword[0])) {
362 			insn.halfword[0] = 0;
363 			insn.halfword[1] = ip->halfword[0];
364 		} else if (is_mmips) {
365 			insn.halfword[0] = ip->halfword[1];
366 			insn.halfword[1] = ip->halfword[0];
367 		} else {
368 			insn.word = ip->word;
369 		}
370 
371 		if (is_jump_ins(&insn))
372 			break;
373 
374 		if (!info->frame_size) {
375 			if (is_sp_move_ins(&insn))
376 			{
377 #ifdef CONFIG_CPU_MICROMIPS
378 				if (mm_insn_16bit(ip->halfword[0]))
379 				{
380 					unsigned short tmp;
381 
382 					if (ip->halfword[0] & mm_addiusp_func)
383 					{
384 						tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
385 						info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
386 					} else {
387 						tmp = (ip->halfword[0] >> 1);
388 						info->frame_size = -(signed short)(tmp & 0xf);
389 					}
390 					ip = (void *) &ip->halfword[1];
391 					ip--;
392 				} else
393 #endif
394 				info->frame_size = - ip->i_format.simmediate;
395 			}
396 			continue;
397 		}
398 		if (info->pc_offset == -1 &&
399 		    is_ra_save_ins(&insn, &info->pc_offset))
400 			break;
401 	}
402 	if (info->frame_size && info->pc_offset >= 0) /* nested */
403 		return 0;
404 	if (info->pc_offset < 0) /* leaf */
405 		return 1;
406 	/* prologue seems bogus... */
407 err:
408 	return -1;
409 }
410 
411 static struct mips_frame_info schedule_mfi __read_mostly;
412 
413 #ifdef CONFIG_KALLSYMS
414 static unsigned long get___schedule_addr(void)
415 {
416 	return kallsyms_lookup_name("__schedule");
417 }
418 #else
419 static unsigned long get___schedule_addr(void)
420 {
421 	union mips_instruction *ip = (void *)schedule;
422 	int max_insns = 8;
423 	int i;
424 
425 	for (i = 0; i < max_insns; i++, ip++) {
426 		if (ip->j_format.opcode == j_op)
427 			return J_TARGET(ip, ip->j_format.target);
428 	}
429 	return 0;
430 }
431 #endif
432 
433 static int __init frame_info_init(void)
434 {
435 	unsigned long size = 0;
436 #ifdef CONFIG_KALLSYMS
437 	unsigned long ofs;
438 #endif
439 	unsigned long addr;
440 
441 	addr = get___schedule_addr();
442 	if (!addr)
443 		addr = (unsigned long)schedule;
444 
445 #ifdef CONFIG_KALLSYMS
446 	kallsyms_lookup_size_offset(addr, &size, &ofs);
447 #endif
448 	schedule_mfi.func = (void *)addr;
449 	schedule_mfi.func_size = size;
450 
451 	get_frame_info(&schedule_mfi);
452 
453 	/*
454 	 * Without schedule() frame info, result given by
455 	 * thread_saved_pc() and get_wchan() are not reliable.
456 	 */
457 	if (schedule_mfi.pc_offset < 0)
458 		printk("Can't analyze schedule() prologue at %p\n", schedule);
459 
460 	return 0;
461 }
462 
463 arch_initcall(frame_info_init);
464 
465 /*
466  * Return saved PC of a blocked thread.
467  */
468 unsigned long thread_saved_pc(struct task_struct *tsk)
469 {
470 	struct thread_struct *t = &tsk->thread;
471 
472 	/* New born processes are a special case */
473 	if (t->reg31 == (unsigned long) ret_from_fork)
474 		return t->reg31;
475 	if (schedule_mfi.pc_offset < 0)
476 		return 0;
477 	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
478 }
479 
480 
481 #ifdef CONFIG_KALLSYMS
482 /* generic stack unwinding function */
483 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
484 					      unsigned long *sp,
485 					      unsigned long pc,
486 					      unsigned long *ra)
487 {
488 	struct mips_frame_info info;
489 	unsigned long size, ofs;
490 	int leaf;
491 	extern void ret_from_irq(void);
492 	extern void ret_from_exception(void);
493 
494 	if (!stack_page)
495 		return 0;
496 
497 	/*
498 	 * If we reached the bottom of interrupt context,
499 	 * return saved pc in pt_regs.
500 	 */
501 	if (pc == (unsigned long)ret_from_irq ||
502 	    pc == (unsigned long)ret_from_exception) {
503 		struct pt_regs *regs;
504 		if (*sp >= stack_page &&
505 		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
506 			regs = (struct pt_regs *)*sp;
507 			pc = regs->cp0_epc;
508 			if (!user_mode(regs) && __kernel_text_address(pc)) {
509 				*sp = regs->regs[29];
510 				*ra = regs->regs[31];
511 				return pc;
512 			}
513 		}
514 		return 0;
515 	}
516 	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
517 		return 0;
518 	/*
519 	 * Return ra if an exception occurred at the first instruction
520 	 */
521 	if (unlikely(ofs == 0)) {
522 		pc = *ra;
523 		*ra = 0;
524 		return pc;
525 	}
526 
527 	info.func = (void *)(pc - ofs);
528 	info.func_size = ofs;	/* analyze from start to ofs */
529 	leaf = get_frame_info(&info);
530 	if (leaf < 0)
531 		return 0;
532 
533 	if (*sp < stack_page ||
534 	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
535 		return 0;
536 
537 	if (leaf)
538 		/*
539 		 * For some extreme cases, get_frame_info() can
540 		 * consider wrongly a nested function as a leaf
541 		 * one. In that cases avoid to return always the
542 		 * same value.
543 		 */
544 		pc = pc != *ra ? *ra : 0;
545 	else
546 		pc = ((unsigned long *)(*sp))[info.pc_offset];
547 
548 	*sp += info.frame_size;
549 	*ra = 0;
550 	return __kernel_text_address(pc) ? pc : 0;
551 }
552 EXPORT_SYMBOL(unwind_stack_by_address);
553 
554 /* used by show_backtrace() */
555 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
556 			   unsigned long pc, unsigned long *ra)
557 {
558 	unsigned long stack_page = 0;
559 	int cpu;
560 
561 	for_each_possible_cpu(cpu) {
562 		if (on_irq_stack(cpu, *sp)) {
563 			stack_page = (unsigned long)irq_stack[cpu];
564 			break;
565 		}
566 	}
567 
568 	if (!stack_page)
569 		stack_page = (unsigned long)task_stack_page(task);
570 
571 	return unwind_stack_by_address(stack_page, sp, pc, ra);
572 }
573 #endif
574 
575 /*
576  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
577  */
578 unsigned long get_wchan(struct task_struct *task)
579 {
580 	unsigned long pc = 0;
581 #ifdef CONFIG_KALLSYMS
582 	unsigned long sp;
583 	unsigned long ra = 0;
584 #endif
585 
586 	if (!task || task == current || task->state == TASK_RUNNING)
587 		goto out;
588 	if (!task_stack_page(task))
589 		goto out;
590 
591 	pc = thread_saved_pc(task);
592 
593 #ifdef CONFIG_KALLSYMS
594 	sp = task->thread.reg29 + schedule_mfi.frame_size;
595 
596 	while (in_sched_functions(pc))
597 		pc = unwind_stack(task, &sp, pc, &ra);
598 #endif
599 
600 out:
601 	return pc;
602 }
603 
604 /*
605  * Don't forget that the stack pointer must be aligned on a 8 bytes
606  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
607  */
608 unsigned long arch_align_stack(unsigned long sp)
609 {
610 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
611 		sp -= get_random_int() & ~PAGE_MASK;
612 
613 	return sp & ALMASK;
614 }
615 
616 static void arch_dump_stack(void *info)
617 {
618 	struct pt_regs *regs;
619 
620 	regs = get_irq_regs();
621 
622 	if (regs)
623 		show_regs(regs);
624 
625 	dump_stack();
626 }
627 
628 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
629 {
630 	long this_cpu = get_cpu();
631 
632 	if (cpumask_test_cpu(this_cpu, mask) && !exclude_self)
633 		dump_stack();
634 
635 	smp_call_function_many(mask, arch_dump_stack, NULL, 1);
636 
637 	put_cpu();
638 }
639 
640 int mips_get_process_fp_mode(struct task_struct *task)
641 {
642 	int value = 0;
643 
644 	if (!test_tsk_thread_flag(task, TIF_32BIT_FPREGS))
645 		value |= PR_FP_MODE_FR;
646 	if (test_tsk_thread_flag(task, TIF_HYBRID_FPREGS))
647 		value |= PR_FP_MODE_FRE;
648 
649 	return value;
650 }
651 
652 static void prepare_for_fp_mode_switch(void *info)
653 {
654 	struct mm_struct *mm = info;
655 
656 	if (current->mm == mm)
657 		lose_fpu(1);
658 }
659 
660 int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)
661 {
662 	const unsigned int known_bits = PR_FP_MODE_FR | PR_FP_MODE_FRE;
663 	struct task_struct *t;
664 	int max_users;
665 
666 	/* Check the value is valid */
667 	if (value & ~known_bits)
668 		return -EOPNOTSUPP;
669 
670 	/* Avoid inadvertently triggering emulation */
671 	if ((value & PR_FP_MODE_FR) && raw_cpu_has_fpu &&
672 	    !(raw_current_cpu_data.fpu_id & MIPS_FPIR_F64))
673 		return -EOPNOTSUPP;
674 	if ((value & PR_FP_MODE_FRE) && raw_cpu_has_fpu && !cpu_has_fre)
675 		return -EOPNOTSUPP;
676 
677 	/* FR = 0 not supported in MIPS R6 */
678 	if (!(value & PR_FP_MODE_FR) && raw_cpu_has_fpu && cpu_has_mips_r6)
679 		return -EOPNOTSUPP;
680 
681 	/* Proceed with the mode switch */
682 	preempt_disable();
683 
684 	/* Save FP & vector context, then disable FPU & MSA */
685 	if (task->signal == current->signal)
686 		lose_fpu(1);
687 
688 	/* Prevent any threads from obtaining live FP context */
689 	atomic_set(&task->mm->context.fp_mode_switching, 1);
690 	smp_mb__after_atomic();
691 
692 	/*
693 	 * If there are multiple online CPUs then force any which are running
694 	 * threads in this process to lose their FPU context, which they can't
695 	 * regain until fp_mode_switching is cleared later.
696 	 */
697 	if (num_online_cpus() > 1) {
698 		/* No need to send an IPI for the local CPU */
699 		max_users = (task->mm == current->mm) ? 1 : 0;
700 
701 		if (atomic_read(&current->mm->mm_users) > max_users)
702 			smp_call_function(prepare_for_fp_mode_switch,
703 					  (void *)current->mm, 1);
704 	}
705 
706 	/*
707 	 * There are now no threads of the process with live FP context, so it
708 	 * is safe to proceed with the FP mode switch.
709 	 */
710 	for_each_thread(task, t) {
711 		/* Update desired FP register width */
712 		if (value & PR_FP_MODE_FR) {
713 			clear_tsk_thread_flag(t, TIF_32BIT_FPREGS);
714 		} else {
715 			set_tsk_thread_flag(t, TIF_32BIT_FPREGS);
716 			clear_tsk_thread_flag(t, TIF_MSA_CTX_LIVE);
717 		}
718 
719 		/* Update desired FP single layout */
720 		if (value & PR_FP_MODE_FRE)
721 			set_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
722 		else
723 			clear_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
724 	}
725 
726 	/* Allow threads to use FP again */
727 	atomic_set(&task->mm->context.fp_mode_switching, 0);
728 	preempt_enable();
729 
730 	return 0;
731 }
732 
733 #if defined(CONFIG_32BIT) || defined(CONFIG_MIPS32_O32)
734 void mips_dump_regs32(u32 *uregs, const struct pt_regs *regs)
735 {
736 	unsigned int i;
737 
738 	for (i = MIPS32_EF_R1; i <= MIPS32_EF_R31; i++) {
739 		/* k0/k1 are copied as zero. */
740 		if (i == MIPS32_EF_R26 || i == MIPS32_EF_R27)
741 			uregs[i] = 0;
742 		else
743 			uregs[i] = regs->regs[i - MIPS32_EF_R0];
744 	}
745 
746 	uregs[MIPS32_EF_LO] = regs->lo;
747 	uregs[MIPS32_EF_HI] = regs->hi;
748 	uregs[MIPS32_EF_CP0_EPC] = regs->cp0_epc;
749 	uregs[MIPS32_EF_CP0_BADVADDR] = regs->cp0_badvaddr;
750 	uregs[MIPS32_EF_CP0_STATUS] = regs->cp0_status;
751 	uregs[MIPS32_EF_CP0_CAUSE] = regs->cp0_cause;
752 }
753 #endif /* CONFIG_32BIT || CONFIG_MIPS32_O32 */
754 
755 #ifdef CONFIG_64BIT
756 void mips_dump_regs64(u64 *uregs, const struct pt_regs *regs)
757 {
758 	unsigned int i;
759 
760 	for (i = MIPS64_EF_R1; i <= MIPS64_EF_R31; i++) {
761 		/* k0/k1 are copied as zero. */
762 		if (i == MIPS64_EF_R26 || i == MIPS64_EF_R27)
763 			uregs[i] = 0;
764 		else
765 			uregs[i] = regs->regs[i - MIPS64_EF_R0];
766 	}
767 
768 	uregs[MIPS64_EF_LO] = regs->lo;
769 	uregs[MIPS64_EF_HI] = regs->hi;
770 	uregs[MIPS64_EF_CP0_EPC] = regs->cp0_epc;
771 	uregs[MIPS64_EF_CP0_BADVADDR] = regs->cp0_badvaddr;
772 	uregs[MIPS64_EF_CP0_STATUS] = regs->cp0_status;
773 	uregs[MIPS64_EF_CP0_CAUSE] = regs->cp0_cause;
774 }
775 #endif /* CONFIG_64BIT */
776