xref: /linux/arch/mips/kernel/process.c (revision 04303f8ec14269b0ea2553863553bc7eaadca1f8) 
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 
29 #include <asm/asm.h>
30 #include <asm/bootinfo.h>
31 #include <asm/cpu.h>
32 #include <asm/dsp.h>
33 #include <asm/fpu.h>
34 #include <asm/msa.h>
35 #include <asm/pgtable.h>
36 #include <asm/mipsregs.h>
37 #include <asm/processor.h>
38 #include <asm/reg.h>
39 #include <asm/uaccess.h>
40 #include <asm/io.h>
41 #include <asm/elf.h>
42 #include <asm/isadep.h>
43 #include <asm/inst.h>
44 #include <asm/stacktrace.h>
45 #include <asm/irq_regs.h>
46 
47 #ifdef CONFIG_HOTPLUG_CPU
48 void arch_cpu_idle_dead(void)
49 {
50 	/* What the heck is this check doing ? */
51 	if (!cpu_isset(smp_processor_id(), cpu_callin_map))
52 		play_dead();
53 }
54 #endif
55 
56 asmlinkage void ret_from_fork(void);
57 asmlinkage void ret_from_kernel_thread(void);
58 
59 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
60 {
61 	unsigned long status;
62 
63 	/* New thread loses kernel privileges. */
64 	status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
65 	status |= KU_USER;
66 	regs->cp0_status = status;
67 	clear_used_math();
68 	clear_fpu_owner();
69 	init_dsp();
70 	clear_thread_flag(TIF_USEDMSA);
71 	clear_thread_flag(TIF_MSA_CTX_LIVE);
72 	disable_msa();
73 	regs->cp0_epc = pc;
74 	regs->regs[29] = sp;
75 }
76 
77 void exit_thread(void)
78 {
79 }
80 
81 void flush_thread(void)
82 {
83 }
84 
85 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
86 {
87 	/*
88 	 * Save any process state which is live in hardware registers to the
89 	 * parent context prior to duplication. This prevents the new child
90 	 * state becoming stale if the parent is preempted before copy_thread()
91 	 * gets a chance to save the parent's live hardware registers to the
92 	 * child context.
93 	 */
94 	preempt_disable();
95 
96 	if (is_msa_enabled())
97 		save_msa(current);
98 	else if (is_fpu_owner())
99 		_save_fp(current);
100 
101 	save_dsp(current);
102 
103 	preempt_enable();
104 
105 	*dst = *src;
106 	return 0;
107 }
108 
109 int copy_thread(unsigned long clone_flags, unsigned long usp,
110 	unsigned long arg, struct task_struct *p)
111 {
112 	struct thread_info *ti = task_thread_info(p);
113 	struct pt_regs *childregs, *regs = current_pt_regs();
114 	unsigned long childksp;
115 	p->set_child_tid = p->clear_child_tid = NULL;
116 
117 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
118 
119 	/* set up new TSS. */
120 	childregs = (struct pt_regs *) childksp - 1;
121 	/*  Put the stack after the struct pt_regs.  */
122 	childksp = (unsigned long) childregs;
123 	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
124 	if (unlikely(p->flags & PF_KTHREAD)) {
125 		unsigned long status = p->thread.cp0_status;
126 		memset(childregs, 0, sizeof(struct pt_regs));
127 		ti->addr_limit = KERNEL_DS;
128 		p->thread.reg16 = usp; /* fn */
129 		p->thread.reg17 = arg;
130 		p->thread.reg29 = childksp;
131 		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
132 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
133 		status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
134 			 ((status & (ST0_KUC | ST0_IEC)) << 2);
135 #else
136 		status |= ST0_EXL;
137 #endif
138 		childregs->cp0_status = status;
139 		return 0;
140 	}
141 	*childregs = *regs;
142 	childregs->regs[7] = 0; /* Clear error flag */
143 	childregs->regs[2] = 0; /* Child gets zero as return value */
144 	if (usp)
145 		childregs->regs[29] = usp;
146 	ti->addr_limit = USER_DS;
147 
148 	p->thread.reg29 = (unsigned long) childregs;
149 	p->thread.reg31 = (unsigned long) ret_from_fork;
150 
151 	/*
152 	 * New tasks lose permission to use the fpu. This accelerates context
153 	 * switching for most programs since they don't use the fpu.
154 	 */
155 	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
156 
157 	clear_tsk_thread_flag(p, TIF_USEDFPU);
158 	clear_tsk_thread_flag(p, TIF_USEDMSA);
159 	clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);
160 
161 #ifdef CONFIG_MIPS_MT_FPAFF
162 	clear_tsk_thread_flag(p, TIF_FPUBOUND);
163 #endif /* CONFIG_MIPS_MT_FPAFF */
164 
165 	if (clone_flags & CLONE_SETTLS)
166 		ti->tp_value = regs->regs[7];
167 
168 	return 0;
169 }
170 
171 #ifdef CONFIG_CC_STACKPROTECTOR
172 #include <linux/stackprotector.h>
173 unsigned long __stack_chk_guard __read_mostly;
174 EXPORT_SYMBOL(__stack_chk_guard);
175 #endif
176 
177 struct mips_frame_info {
178 	void		*func;
179 	unsigned long	func_size;
180 	int		frame_size;
181 	int		pc_offset;
182 };
183 
184 #define J_TARGET(pc,target)	\
185 		(((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
186 
187 static inline int is_ra_save_ins(union mips_instruction *ip)
188 {
189 #ifdef CONFIG_CPU_MICROMIPS
190 	union mips_instruction mmi;
191 
192 	/*
193 	 * swsp ra,offset
194 	 * swm16 reglist,offset(sp)
195 	 * swm32 reglist,offset(sp)
196 	 * sw32 ra,offset(sp)
197 	 * jradiussp - NOT SUPPORTED
198 	 *
199 	 * microMIPS is way more fun...
200 	 */
201 	if (mm_insn_16bit(ip->halfword[0])) {
202 		mmi.word = (ip->halfword[0] << 16);
203 		return (mmi.mm16_r5_format.opcode == mm_swsp16_op &&
204 			mmi.mm16_r5_format.rt == 31) ||
205 		       (mmi.mm16_m_format.opcode == mm_pool16c_op &&
206 			mmi.mm16_m_format.func == mm_swm16_op);
207 	}
208 	else {
209 		mmi.halfword[0] = ip->halfword[1];
210 		mmi.halfword[1] = ip->halfword[0];
211 		return (mmi.mm_m_format.opcode == mm_pool32b_op &&
212 			mmi.mm_m_format.rd > 9 &&
213 			mmi.mm_m_format.base == 29 &&
214 			mmi.mm_m_format.func == mm_swm32_func) ||
215 		       (mmi.i_format.opcode == mm_sw32_op &&
216 			mmi.i_format.rs == 29 &&
217 			mmi.i_format.rt == 31);
218 	}
219 #else
220 	/* sw / sd $ra, offset($sp) */
221 	return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
222 		ip->i_format.rs == 29 &&
223 		ip->i_format.rt == 31;
224 #endif
225 }
226 
227 static inline int is_jump_ins(union mips_instruction *ip)
228 {
229 #ifdef CONFIG_CPU_MICROMIPS
230 	/*
231 	 * jr16,jrc,jalr16,jalr16
232 	 * jal
233 	 * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
234 	 * jraddiusp - NOT SUPPORTED
235 	 *
236 	 * microMIPS is kind of more fun...
237 	 */
238 	union mips_instruction mmi;
239 
240 	mmi.word = (ip->halfword[0] << 16);
241 
242 	if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
243 	    (mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
244 	    ip->j_format.opcode == mm_jal32_op)
245 		return 1;
246 	if (ip->r_format.opcode != mm_pool32a_op ||
247 			ip->r_format.func != mm_pool32axf_op)
248 		return 0;
249 	return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
250 #else
251 	if (ip->j_format.opcode == j_op)
252 		return 1;
253 	if (ip->j_format.opcode == jal_op)
254 		return 1;
255 	if (ip->r_format.opcode != spec_op)
256 		return 0;
257 	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
258 #endif
259 }
260 
261 static inline int is_sp_move_ins(union mips_instruction *ip)
262 {
263 #ifdef CONFIG_CPU_MICROMIPS
264 	/*
265 	 * addiusp -imm
266 	 * addius5 sp,-imm
267 	 * addiu32 sp,sp,-imm
268 	 * jradiussp - NOT SUPPORTED
269 	 *
270 	 * microMIPS is not more fun...
271 	 */
272 	if (mm_insn_16bit(ip->halfword[0])) {
273 		union mips_instruction mmi;
274 
275 		mmi.word = (ip->halfword[0] << 16);
276 		return (mmi.mm16_r3_format.opcode == mm_pool16d_op &&
277 			mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
278 		       (mmi.mm16_r5_format.opcode == mm_pool16d_op &&
279 			mmi.mm16_r5_format.rt == 29);
280 	}
281 	return ip->mm_i_format.opcode == mm_addiu32_op &&
282 	       ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
283 #else
284 	/* addiu/daddiu sp,sp,-imm */
285 	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
286 		return 0;
287 	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
288 		return 1;
289 #endif
290 	return 0;
291 }
292 
293 static int get_frame_info(struct mips_frame_info *info)
294 {
295 #ifdef CONFIG_CPU_MICROMIPS
296 	union mips_instruction *ip = (void *) (((char *) info->func) - 1);
297 #else
298 	union mips_instruction *ip = info->func;
299 #endif
300 	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
301 	unsigned i;
302 
303 	info->pc_offset = -1;
304 	info->frame_size = 0;
305 
306 	if (!ip)
307 		goto err;
308 
309 	if (max_insns == 0)
310 		max_insns = 128U;	/* unknown function size */
311 	max_insns = min(128U, max_insns);
312 
313 	for (i = 0; i < max_insns; i++, ip++) {
314 
315 		if (is_jump_ins(ip))
316 			break;
317 		if (!info->frame_size) {
318 			if (is_sp_move_ins(ip))
319 			{
320 #ifdef CONFIG_CPU_MICROMIPS
321 				if (mm_insn_16bit(ip->halfword[0]))
322 				{
323 					unsigned short tmp;
324 
325 					if (ip->halfword[0] & mm_addiusp_func)
326 					{
327 						tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
328 						info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
329 					} else {
330 						tmp = (ip->halfword[0] >> 1);
331 						info->frame_size = -(signed short)(tmp & 0xf);
332 					}
333 					ip = (void *) &ip->halfword[1];
334 					ip--;
335 				} else
336 #endif
337 				info->frame_size = - ip->i_format.simmediate;
338 			}
339 			continue;
340 		}
341 		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
342 			info->pc_offset =
343 				ip->i_format.simmediate / sizeof(long);
344 			break;
345 		}
346 	}
347 	if (info->frame_size && info->pc_offset >= 0) /* nested */
348 		return 0;
349 	if (info->pc_offset < 0) /* leaf */
350 		return 1;
351 	/* prologue seems boggus... */
352 err:
353 	return -1;
354 }
355 
356 static struct mips_frame_info schedule_mfi __read_mostly;
357 
358 #ifdef CONFIG_KALLSYMS
359 static unsigned long get___schedule_addr(void)
360 {
361 	return kallsyms_lookup_name("__schedule");
362 }
363 #else
364 static unsigned long get___schedule_addr(void)
365 {
366 	union mips_instruction *ip = (void *)schedule;
367 	int max_insns = 8;
368 	int i;
369 
370 	for (i = 0; i < max_insns; i++, ip++) {
371 		if (ip->j_format.opcode == j_op)
372 			return J_TARGET(ip, ip->j_format.target);
373 	}
374 	return 0;
375 }
376 #endif
377 
378 static int __init frame_info_init(void)
379 {
380 	unsigned long size = 0;
381 #ifdef CONFIG_KALLSYMS
382 	unsigned long ofs;
383 #endif
384 	unsigned long addr;
385 
386 	addr = get___schedule_addr();
387 	if (!addr)
388 		addr = (unsigned long)schedule;
389 
390 #ifdef CONFIG_KALLSYMS
391 	kallsyms_lookup_size_offset(addr, &size, &ofs);
392 #endif
393 	schedule_mfi.func = (void *)addr;
394 	schedule_mfi.func_size = size;
395 
396 	get_frame_info(&schedule_mfi);
397 
398 	/*
399 	 * Without schedule() frame info, result given by
400 	 * thread_saved_pc() and get_wchan() are not reliable.
401 	 */
402 	if (schedule_mfi.pc_offset < 0)
403 		printk("Can't analyze schedule() prologue at %p\n", schedule);
404 
405 	return 0;
406 }
407 
408 arch_initcall(frame_info_init);
409 
410 /*
411  * Return saved PC of a blocked thread.
412  */
413 unsigned long thread_saved_pc(struct task_struct *tsk)
414 {
415 	struct thread_struct *t = &tsk->thread;
416 
417 	/* New born processes are a special case */
418 	if (t->reg31 == (unsigned long) ret_from_fork)
419 		return t->reg31;
420 	if (schedule_mfi.pc_offset < 0)
421 		return 0;
422 	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
423 }
424 
425 
426 #ifdef CONFIG_KALLSYMS
427 /* generic stack unwinding function */
428 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
429 					      unsigned long *sp,
430 					      unsigned long pc,
431 					      unsigned long *ra)
432 {
433 	struct mips_frame_info info;
434 	unsigned long size, ofs;
435 	int leaf;
436 	extern void ret_from_irq(void);
437 	extern void ret_from_exception(void);
438 
439 	if (!stack_page)
440 		return 0;
441 
442 	/*
443 	 * If we reached the bottom of interrupt context,
444 	 * return saved pc in pt_regs.
445 	 */
446 	if (pc == (unsigned long)ret_from_irq ||
447 	    pc == (unsigned long)ret_from_exception) {
448 		struct pt_regs *regs;
449 		if (*sp >= stack_page &&
450 		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
451 			regs = (struct pt_regs *)*sp;
452 			pc = regs->cp0_epc;
453 			if (__kernel_text_address(pc)) {
454 				*sp = regs->regs[29];
455 				*ra = regs->regs[31];
456 				return pc;
457 			}
458 		}
459 		return 0;
460 	}
461 	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
462 		return 0;
463 	/*
464 	 * Return ra if an exception occurred at the first instruction
465 	 */
466 	if (unlikely(ofs == 0)) {
467 		pc = *ra;
468 		*ra = 0;
469 		return pc;
470 	}
471 
472 	info.func = (void *)(pc - ofs);
473 	info.func_size = ofs;	/* analyze from start to ofs */
474 	leaf = get_frame_info(&info);
475 	if (leaf < 0)
476 		return 0;
477 
478 	if (*sp < stack_page ||
479 	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
480 		return 0;
481 
482 	if (leaf)
483 		/*
484 		 * For some extreme cases, get_frame_info() can
485 		 * consider wrongly a nested function as a leaf
486 		 * one. In that cases avoid to return always the
487 		 * same value.
488 		 */
489 		pc = pc != *ra ? *ra : 0;
490 	else
491 		pc = ((unsigned long *)(*sp))[info.pc_offset];
492 
493 	*sp += info.frame_size;
494 	*ra = 0;
495 	return __kernel_text_address(pc) ? pc : 0;
496 }
497 EXPORT_SYMBOL(unwind_stack_by_address);
498 
499 /* used by show_backtrace() */
500 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
501 			   unsigned long pc, unsigned long *ra)
502 {
503 	unsigned long stack_page = (unsigned long)task_stack_page(task);
504 	return unwind_stack_by_address(stack_page, sp, pc, ra);
505 }
506 #endif
507 
508 /*
509  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
510  */
511 unsigned long get_wchan(struct task_struct *task)
512 {
513 	unsigned long pc = 0;
514 #ifdef CONFIG_KALLSYMS
515 	unsigned long sp;
516 	unsigned long ra = 0;
517 #endif
518 
519 	if (!task || task == current || task->state == TASK_RUNNING)
520 		goto out;
521 	if (!task_stack_page(task))
522 		goto out;
523 
524 	pc = thread_saved_pc(task);
525 
526 #ifdef CONFIG_KALLSYMS
527 	sp = task->thread.reg29 + schedule_mfi.frame_size;
528 
529 	while (in_sched_functions(pc))
530 		pc = unwind_stack(task, &sp, pc, &ra);
531 #endif
532 
533 out:
534 	return pc;
535 }
536 
537 /*
538  * Don't forget that the stack pointer must be aligned on a 8 bytes
539  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
540  */
541 unsigned long arch_align_stack(unsigned long sp)
542 {
543 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
544 		sp -= get_random_int() & ~PAGE_MASK;
545 
546 	return sp & ALMASK;
547 }
548 
549 static void arch_dump_stack(void *info)
550 {
551 	struct pt_regs *regs;
552 
553 	regs = get_irq_regs();
554 
555 	if (regs)
556 		show_regs(regs);
557 
558 	dump_stack();
559 }
560 
561 void arch_trigger_all_cpu_backtrace(bool include_self)
562 {
563 	smp_call_function(arch_dump_stack, NULL, 1);
564 }
565