xref: /openbmc/linux/arch/mips/kernel/process.c (revision afb46f79) 
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/user.h>
25 #include <linux/init.h>
26 #include <linux/completion.h>
27 #include <linux/kallsyms.h>
28 #include <linux/random.h>
29 
30 #include <asm/asm.h>
31 #include <asm/bootinfo.h>
32 #include <asm/cpu.h>
33 #include <asm/dsp.h>
34 #include <asm/fpu.h>
35 #include <asm/msa.h>
36 #include <asm/pgtable.h>
37 #include <asm/mipsregs.h>
38 #include <asm/processor.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 
46 #ifdef CONFIG_HOTPLUG_CPU
47 void arch_cpu_idle_dead(void)
48 {
49 	/* What the heck is this check doing ? */
50 	if (!cpu_isset(smp_processor_id(), cpu_callin_map))
51 		play_dead();
52 }
53 #endif
54 
55 asmlinkage void ret_from_fork(void);
56 asmlinkage void ret_from_kernel_thread(void);
57 
58 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
59 {
60 	unsigned long status;
61 
62 	/* New thread loses kernel privileges. */
63 	status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
64 	status |= KU_USER;
65 	regs->cp0_status = status;
66 	clear_used_math();
67 	clear_fpu_owner();
68 	init_dsp();
69 	clear_thread_flag(TIF_MSA_CTX_LIVE);
70 	disable_msa();
71 	regs->cp0_epc = pc;
72 	regs->regs[29] = sp;
73 }
74 
75 void exit_thread(void)
76 {
77 }
78 
79 void flush_thread(void)
80 {
81 }
82 
83 int copy_thread(unsigned long clone_flags, unsigned long usp,
84 	unsigned long arg, struct task_struct *p)
85 {
86 	struct thread_info *ti = task_thread_info(p);
87 	struct pt_regs *childregs, *regs = current_pt_regs();
88 	unsigned long childksp;
89 	p->set_child_tid = p->clear_child_tid = NULL;
90 
91 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
92 
93 	preempt_disable();
94 
95 	if (is_msa_enabled())
96 		save_msa(p);
97 	else if (is_fpu_owner())
98 		save_fp(p);
99 
100 	if (cpu_has_dsp)
101 		save_dsp(p);
102 
103 	preempt_enable();
104 
105 	/* set up new TSS. */
106 	childregs = (struct pt_regs *) childksp - 1;
107 	/*  Put the stack after the struct pt_regs.  */
108 	childksp = (unsigned long) childregs;
109 	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
110 	if (unlikely(p->flags & PF_KTHREAD)) {
111 		unsigned long status = p->thread.cp0_status;
112 		memset(childregs, 0, sizeof(struct pt_regs));
113 		ti->addr_limit = KERNEL_DS;
114 		p->thread.reg16 = usp; /* fn */
115 		p->thread.reg17 = arg;
116 		p->thread.reg29 = childksp;
117 		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
118 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
119 		status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
120 			 ((status & (ST0_KUC | ST0_IEC)) << 2);
121 #else
122 		status |= ST0_EXL;
123 #endif
124 		childregs->cp0_status = status;
125 		return 0;
126 	}
127 	*childregs = *regs;
128 	childregs->regs[7] = 0; /* Clear error flag */
129 	childregs->regs[2] = 0; /* Child gets zero as return value */
130 	if (usp)
131 		childregs->regs[29] = usp;
132 	ti->addr_limit = USER_DS;
133 
134 	p->thread.reg29 = (unsigned long) childregs;
135 	p->thread.reg31 = (unsigned long) ret_from_fork;
136 
137 	/*
138 	 * New tasks lose permission to use the fpu. This accelerates context
139 	 * switching for most programs since they don't use the fpu.
140 	 */
141 	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
142 
143 #ifdef CONFIG_MIPS_MT_SMTC
144 	/*
145 	 * SMTC restores TCStatus after Status, and the CU bits
146 	 * are aliased there.
147 	 */
148 	childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
149 #endif
150 	clear_tsk_thread_flag(p, TIF_USEDFPU);
151 
152 #ifdef CONFIG_MIPS_MT_FPAFF
153 	clear_tsk_thread_flag(p, TIF_FPUBOUND);
154 #endif /* CONFIG_MIPS_MT_FPAFF */
155 
156 	if (clone_flags & CLONE_SETTLS)
157 		ti->tp_value = regs->regs[7];
158 
159 	return 0;
160 }
161 
162 /* Fill in the fpu structure for a core dump.. */
163 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
164 {
165 	int i;
166 
167 	for (i = 0; i < NUM_FPU_REGS; i++)
168 		memcpy(&r[i], &current->thread.fpu.fpr[i], sizeof(*r));
169 
170 	memcpy(&r[NUM_FPU_REGS], &current->thread.fpu.fcr31,
171 	       sizeof(current->thread.fpu.fcr31));
172 
173 	return 1;
174 }
175 
176 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
177 {
178 	int i;
179 
180 	for (i = 0; i < EF_R0; i++)
181 		gp[i] = 0;
182 	gp[EF_R0] = 0;
183 	for (i = 1; i <= 31; i++)
184 		gp[EF_R0 + i] = regs->regs[i];
185 	gp[EF_R26] = 0;
186 	gp[EF_R27] = 0;
187 	gp[EF_LO] = regs->lo;
188 	gp[EF_HI] = regs->hi;
189 	gp[EF_CP0_EPC] = regs->cp0_epc;
190 	gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
191 	gp[EF_CP0_STATUS] = regs->cp0_status;
192 	gp[EF_CP0_CAUSE] = regs->cp0_cause;
193 #ifdef EF_UNUSED0
194 	gp[EF_UNUSED0] = 0;
195 #endif
196 }
197 
198 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
199 {
200 	elf_dump_regs(*regs, task_pt_regs(tsk));
201 	return 1;
202 }
203 
204 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
205 {
206 	int i;
207 
208 	for (i = 0; i < NUM_FPU_REGS; i++)
209 		memcpy(&fpr[i], &t->thread.fpu.fpr[i], sizeof(*fpr));
210 
211 	memcpy(&fpr[NUM_FPU_REGS], &t->thread.fpu.fcr31,
212 	       sizeof(t->thread.fpu.fcr31));
213 
214 	return 1;
215 }
216 
217 #ifdef CONFIG_CC_STACKPROTECTOR
218 #include <linux/stackprotector.h>
219 unsigned long __stack_chk_guard __read_mostly;
220 EXPORT_SYMBOL(__stack_chk_guard);
221 #endif
222 
223 struct mips_frame_info {
224 	void		*func;
225 	unsigned long	func_size;
226 	int		frame_size;
227 	int		pc_offset;
228 };
229 
230 #define J_TARGET(pc,target)	\
231 		(((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
232 
233 static inline int is_ra_save_ins(union mips_instruction *ip)
234 {
235 #ifdef CONFIG_CPU_MICROMIPS
236 	union mips_instruction mmi;
237 
238 	/*
239 	 * swsp ra,offset
240 	 * swm16 reglist,offset(sp)
241 	 * swm32 reglist,offset(sp)
242 	 * sw32 ra,offset(sp)
243 	 * jradiussp - NOT SUPPORTED
244 	 *
245 	 * microMIPS is way more fun...
246 	 */
247 	if (mm_insn_16bit(ip->halfword[0])) {
248 		mmi.word = (ip->halfword[0] << 16);
249 		return ((mmi.mm16_r5_format.opcode == mm_swsp16_op &&
250 			 mmi.mm16_r5_format.rt == 31) ||
251 			(mmi.mm16_m_format.opcode == mm_pool16c_op &&
252 			 mmi.mm16_m_format.func == mm_swm16_op));
253 	}
254 	else {
255 		mmi.halfword[0] = ip->halfword[1];
256 		mmi.halfword[1] = ip->halfword[0];
257 		return ((mmi.mm_m_format.opcode == mm_pool32b_op &&
258 			 mmi.mm_m_format.rd > 9 &&
259 			 mmi.mm_m_format.base == 29 &&
260 			 mmi.mm_m_format.func == mm_swm32_func) ||
261 			(mmi.i_format.opcode == mm_sw32_op &&
262 			 mmi.i_format.rs == 29 &&
263 			 mmi.i_format.rt == 31));
264 	}
265 #else
266 	/* sw / sd $ra, offset($sp) */
267 	return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
268 		ip->i_format.rs == 29 &&
269 		ip->i_format.rt == 31;
270 #endif
271 }
272 
273 static inline int is_jump_ins(union mips_instruction *ip)
274 {
275 #ifdef CONFIG_CPU_MICROMIPS
276 	/*
277 	 * jr16,jrc,jalr16,jalr16
278 	 * jal
279 	 * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
280 	 * jraddiusp - NOT SUPPORTED
281 	 *
282 	 * microMIPS is kind of more fun...
283 	 */
284 	union mips_instruction mmi;
285 
286 	mmi.word = (ip->halfword[0] << 16);
287 
288 	if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
289 	    (mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
290 	    ip->j_format.opcode == mm_jal32_op)
291 		return 1;
292 	if (ip->r_format.opcode != mm_pool32a_op ||
293 			ip->r_format.func != mm_pool32axf_op)
294 		return 0;
295 	return (((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op);
296 #else
297 	if (ip->j_format.opcode == j_op)
298 		return 1;
299 	if (ip->j_format.opcode == jal_op)
300 		return 1;
301 	if (ip->r_format.opcode != spec_op)
302 		return 0;
303 	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
304 #endif
305 }
306 
307 static inline int is_sp_move_ins(union mips_instruction *ip)
308 {
309 #ifdef CONFIG_CPU_MICROMIPS
310 	/*
311 	 * addiusp -imm
312 	 * addius5 sp,-imm
313 	 * addiu32 sp,sp,-imm
314 	 * jradiussp - NOT SUPPORTED
315 	 *
316 	 * microMIPS is not more fun...
317 	 */
318 	if (mm_insn_16bit(ip->halfword[0])) {
319 		union mips_instruction mmi;
320 
321 		mmi.word = (ip->halfword[0] << 16);
322 		return ((mmi.mm16_r3_format.opcode == mm_pool16d_op &&
323 			 mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
324 			(mmi.mm16_r5_format.opcode == mm_pool16d_op &&
325 			 mmi.mm16_r5_format.rt == 29));
326 	}
327 	return (ip->mm_i_format.opcode == mm_addiu32_op &&
328 		 ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29);
329 #else
330 	/* addiu/daddiu sp,sp,-imm */
331 	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
332 		return 0;
333 	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
334 		return 1;
335 #endif
336 	return 0;
337 }
338 
339 static int get_frame_info(struct mips_frame_info *info)
340 {
341 #ifdef CONFIG_CPU_MICROMIPS
342 	union mips_instruction *ip = (void *) (((char *) info->func) - 1);
343 #else
344 	union mips_instruction *ip = info->func;
345 #endif
346 	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
347 	unsigned i;
348 
349 	info->pc_offset = -1;
350 	info->frame_size = 0;
351 
352 	if (!ip)
353 		goto err;
354 
355 	if (max_insns == 0)
356 		max_insns = 128U;	/* unknown function size */
357 	max_insns = min(128U, max_insns);
358 
359 	for (i = 0; i < max_insns; i++, ip++) {
360 
361 		if (is_jump_ins(ip))
362 			break;
363 		if (!info->frame_size) {
364 			if (is_sp_move_ins(ip))
365 			{
366 #ifdef CONFIG_CPU_MICROMIPS
367 				if (mm_insn_16bit(ip->halfword[0]))
368 				{
369 					unsigned short tmp;
370 
371 					if (ip->halfword[0] & mm_addiusp_func)
372 					{
373 						tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
374 						info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
375 					} else {
376 						tmp = (ip->halfword[0] >> 1);
377 						info->frame_size = -(signed short)(tmp & 0xf);
378 					}
379 					ip = (void *) &ip->halfword[1];
380 					ip--;
381 				} else
382 #endif
383 				info->frame_size = - ip->i_format.simmediate;
384 			}
385 			continue;
386 		}
387 		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
388 			info->pc_offset =
389 				ip->i_format.simmediate / sizeof(long);
390 			break;
391 		}
392 	}
393 	if (info->frame_size && info->pc_offset >= 0) /* nested */
394 		return 0;
395 	if (info->pc_offset < 0) /* leaf */
396 		return 1;
397 	/* prologue seems boggus... */
398 err:
399 	return -1;
400 }
401 
402 static struct mips_frame_info schedule_mfi __read_mostly;
403 
404 #ifdef CONFIG_KALLSYMS
405 static unsigned long get___schedule_addr(void)
406 {
407 	return kallsyms_lookup_name("__schedule");
408 }
409 #else
410 static unsigned long get___schedule_addr(void)
411 {
412 	union mips_instruction *ip = (void *)schedule;
413 	int max_insns = 8;
414 	int i;
415 
416 	for (i = 0; i < max_insns; i++, ip++) {
417 		if (ip->j_format.opcode == j_op)
418 			return J_TARGET(ip, ip->j_format.target);
419 	}
420 	return 0;
421 }
422 #endif
423 
424 static int __init frame_info_init(void)
425 {
426 	unsigned long size = 0;
427 #ifdef CONFIG_KALLSYMS
428 	unsigned long ofs;
429 #endif
430 	unsigned long addr;
431 
432 	addr = get___schedule_addr();
433 	if (!addr)
434 		addr = (unsigned long)schedule;
435 
436 #ifdef CONFIG_KALLSYMS
437 	kallsyms_lookup_size_offset(addr, &size, &ofs);
438 #endif
439 	schedule_mfi.func = (void *)addr;
440 	schedule_mfi.func_size = size;
441 
442 	get_frame_info(&schedule_mfi);
443 
444 	/*
445 	 * Without schedule() frame info, result given by
446 	 * thread_saved_pc() and get_wchan() are not reliable.
447 	 */
448 	if (schedule_mfi.pc_offset < 0)
449 		printk("Can't analyze schedule() prologue at %p\n", schedule);
450 
451 	return 0;
452 }
453 
454 arch_initcall(frame_info_init);
455 
456 /*
457  * Return saved PC of a blocked thread.
458  */
459 unsigned long thread_saved_pc(struct task_struct *tsk)
460 {
461 	struct thread_struct *t = &tsk->thread;
462 
463 	/* New born processes are a special case */
464 	if (t->reg31 == (unsigned long) ret_from_fork)
465 		return t->reg31;
466 	if (schedule_mfi.pc_offset < 0)
467 		return 0;
468 	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
469 }
470 
471 
472 #ifdef CONFIG_KALLSYMS
473 /* generic stack unwinding function */
474 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
475 					      unsigned long *sp,
476 					      unsigned long pc,
477 					      unsigned long *ra)
478 {
479 	struct mips_frame_info info;
480 	unsigned long size, ofs;
481 	int leaf;
482 	extern void ret_from_irq(void);
483 	extern void ret_from_exception(void);
484 
485 	if (!stack_page)
486 		return 0;
487 
488 	/*
489 	 * If we reached the bottom of interrupt context,
490 	 * return saved pc in pt_regs.
491 	 */
492 	if (pc == (unsigned long)ret_from_irq ||
493 	    pc == (unsigned long)ret_from_exception) {
494 		struct pt_regs *regs;
495 		if (*sp >= stack_page &&
496 		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
497 			regs = (struct pt_regs *)*sp;
498 			pc = regs->cp0_epc;
499 			if (__kernel_text_address(pc)) {
500 				*sp = regs->regs[29];
501 				*ra = regs->regs[31];
502 				return pc;
503 			}
504 		}
505 		return 0;
506 	}
507 	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
508 		return 0;
509 	/*
510 	 * Return ra if an exception occurred at the first instruction
511 	 */
512 	if (unlikely(ofs == 0)) {
513 		pc = *ra;
514 		*ra = 0;
515 		return pc;
516 	}
517 
518 	info.func = (void *)(pc - ofs);
519 	info.func_size = ofs;	/* analyze from start to ofs */
520 	leaf = get_frame_info(&info);
521 	if (leaf < 0)
522 		return 0;
523 
524 	if (*sp < stack_page ||
525 	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
526 		return 0;
527 
528 	if (leaf)
529 		/*
530 		 * For some extreme cases, get_frame_info() can
531 		 * consider wrongly a nested function as a leaf
532 		 * one. In that cases avoid to return always the
533 		 * same value.
534 		 */
535 		pc = pc != *ra ? *ra : 0;
536 	else
537 		pc = ((unsigned long *)(*sp))[info.pc_offset];
538 
539 	*sp += info.frame_size;
540 	*ra = 0;
541 	return __kernel_text_address(pc) ? pc : 0;
542 }
543 EXPORT_SYMBOL(unwind_stack_by_address);
544 
545 /* used by show_backtrace() */
546 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
547 			   unsigned long pc, unsigned long *ra)
548 {
549 	unsigned long stack_page = (unsigned long)task_stack_page(task);
550 	return unwind_stack_by_address(stack_page, sp, pc, ra);
551 }
552 #endif
553 
554 /*
555  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
556  */
557 unsigned long get_wchan(struct task_struct *task)
558 {
559 	unsigned long pc = 0;
560 #ifdef CONFIG_KALLSYMS
561 	unsigned long sp;
562 	unsigned long ra = 0;
563 #endif
564 
565 	if (!task || task == current || task->state == TASK_RUNNING)
566 		goto out;
567 	if (!task_stack_page(task))
568 		goto out;
569 
570 	pc = thread_saved_pc(task);
571 
572 #ifdef CONFIG_KALLSYMS
573 	sp = task->thread.reg29 + schedule_mfi.frame_size;
574 
575 	while (in_sched_functions(pc))
576 		pc = unwind_stack(task, &sp, pc, &ra);
577 #endif
578 
579 out:
580 	return pc;
581 }
582 
583 /*
584  * Don't forget that the stack pointer must be aligned on a 8 bytes
585  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
586  */
587 unsigned long arch_align_stack(unsigned long sp)
588 {
589 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
590 		sp -= get_random_int() & ~PAGE_MASK;
591 
592 	return sp & ALMASK;
593 }
594