xref: /openbmc/linux/arch/mips/kernel/process.c (revision 2ff40400) 
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 copy_thread(unsigned long clone_flags, unsigned long usp,
86 	unsigned long arg, struct task_struct *p)
87 {
88 	struct thread_info *ti = task_thread_info(p);
89 	struct pt_regs *childregs, *regs = current_pt_regs();
90 	unsigned long childksp;
91 	p->set_child_tid = p->clear_child_tid = NULL;
92 
93 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
94 
95 	preempt_disable();
96 
97 	if (is_msa_enabled())
98 		save_msa(p);
99 	else if (is_fpu_owner())
100 		save_fp(p);
101 
102 	if (cpu_has_dsp)
103 		save_dsp(p);
104 
105 	preempt_enable();
106 
107 	/* set up new TSS. */
108 	childregs = (struct pt_regs *) childksp - 1;
109 	/*  Put the stack after the struct pt_regs.  */
110 	childksp = (unsigned long) childregs;
111 	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
112 	if (unlikely(p->flags & PF_KTHREAD)) {
113 		unsigned long status = p->thread.cp0_status;
114 		memset(childregs, 0, sizeof(struct pt_regs));
115 		ti->addr_limit = KERNEL_DS;
116 		p->thread.reg16 = usp; /* fn */
117 		p->thread.reg17 = arg;
118 		p->thread.reg29 = childksp;
119 		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
120 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
121 		status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
122 			 ((status & (ST0_KUC | ST0_IEC)) << 2);
123 #else
124 		status |= ST0_EXL;
125 #endif
126 		childregs->cp0_status = status;
127 		return 0;
128 	}
129 	*childregs = *regs;
130 	childregs->regs[7] = 0; /* Clear error flag */
131 	childregs->regs[2] = 0; /* Child gets zero as return value */
132 	if (usp)
133 		childregs->regs[29] = usp;
134 	ti->addr_limit = USER_DS;
135 
136 	p->thread.reg29 = (unsigned long) childregs;
137 	p->thread.reg31 = (unsigned long) ret_from_fork;
138 
139 	/*
140 	 * New tasks lose permission to use the fpu. This accelerates context
141 	 * switching for most programs since they don't use the fpu.
142 	 */
143 	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
144 
145 	clear_tsk_thread_flag(p, TIF_USEDFPU);
146 	clear_tsk_thread_flag(p, TIF_USEDMSA);
147 	clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);
148 
149 #ifdef CONFIG_MIPS_MT_FPAFF
150 	clear_tsk_thread_flag(p, TIF_FPUBOUND);
151 #endif /* CONFIG_MIPS_MT_FPAFF */
152 
153 	if (clone_flags & CLONE_SETTLS)
154 		ti->tp_value = regs->regs[7];
155 
156 	return 0;
157 }
158 
159 #ifdef CONFIG_CC_STACKPROTECTOR
160 #include <linux/stackprotector.h>
161 unsigned long __stack_chk_guard __read_mostly;
162 EXPORT_SYMBOL(__stack_chk_guard);
163 #endif
164 
165 struct mips_frame_info {
166 	void		*func;
167 	unsigned long	func_size;
168 	int		frame_size;
169 	int		pc_offset;
170 };
171 
172 #define J_TARGET(pc,target)	\
173 		(((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
174 
175 static inline int is_ra_save_ins(union mips_instruction *ip)
176 {
177 #ifdef CONFIG_CPU_MICROMIPS
178 	union mips_instruction mmi;
179 
180 	/*
181 	 * swsp ra,offset
182 	 * swm16 reglist,offset(sp)
183 	 * swm32 reglist,offset(sp)
184 	 * sw32 ra,offset(sp)
185 	 * jradiussp - NOT SUPPORTED
186 	 *
187 	 * microMIPS is way more fun...
188 	 */
189 	if (mm_insn_16bit(ip->halfword[0])) {
190 		mmi.word = (ip->halfword[0] << 16);
191 		return (mmi.mm16_r5_format.opcode == mm_swsp16_op &&
192 			mmi.mm16_r5_format.rt == 31) ||
193 		       (mmi.mm16_m_format.opcode == mm_pool16c_op &&
194 			mmi.mm16_m_format.func == mm_swm16_op);
195 	}
196 	else {
197 		mmi.halfword[0] = ip->halfword[1];
198 		mmi.halfword[1] = ip->halfword[0];
199 		return (mmi.mm_m_format.opcode == mm_pool32b_op &&
200 			mmi.mm_m_format.rd > 9 &&
201 			mmi.mm_m_format.base == 29 &&
202 			mmi.mm_m_format.func == mm_swm32_func) ||
203 		       (mmi.i_format.opcode == mm_sw32_op &&
204 			mmi.i_format.rs == 29 &&
205 			mmi.i_format.rt == 31);
206 	}
207 #else
208 	/* sw / sd $ra, offset($sp) */
209 	return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
210 		ip->i_format.rs == 29 &&
211 		ip->i_format.rt == 31;
212 #endif
213 }
214 
215 static inline int is_jump_ins(union mips_instruction *ip)
216 {
217 #ifdef CONFIG_CPU_MICROMIPS
218 	/*
219 	 * jr16,jrc,jalr16,jalr16
220 	 * jal
221 	 * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
222 	 * jraddiusp - NOT SUPPORTED
223 	 *
224 	 * microMIPS is kind of more fun...
225 	 */
226 	union mips_instruction mmi;
227 
228 	mmi.word = (ip->halfword[0] << 16);
229 
230 	if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
231 	    (mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
232 	    ip->j_format.opcode == mm_jal32_op)
233 		return 1;
234 	if (ip->r_format.opcode != mm_pool32a_op ||
235 			ip->r_format.func != mm_pool32axf_op)
236 		return 0;
237 	return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
238 #else
239 	if (ip->j_format.opcode == j_op)
240 		return 1;
241 	if (ip->j_format.opcode == jal_op)
242 		return 1;
243 	if (ip->r_format.opcode != spec_op)
244 		return 0;
245 	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
246 #endif
247 }
248 
249 static inline int is_sp_move_ins(union mips_instruction *ip)
250 {
251 #ifdef CONFIG_CPU_MICROMIPS
252 	/*
253 	 * addiusp -imm
254 	 * addius5 sp,-imm
255 	 * addiu32 sp,sp,-imm
256 	 * jradiussp - NOT SUPPORTED
257 	 *
258 	 * microMIPS is not more fun...
259 	 */
260 	if (mm_insn_16bit(ip->halfword[0])) {
261 		union mips_instruction mmi;
262 
263 		mmi.word = (ip->halfword[0] << 16);
264 		return (mmi.mm16_r3_format.opcode == mm_pool16d_op &&
265 			mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
266 		       (mmi.mm16_r5_format.opcode == mm_pool16d_op &&
267 			mmi.mm16_r5_format.rt == 29);
268 	}
269 	return ip->mm_i_format.opcode == mm_addiu32_op &&
270 	       ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
271 #else
272 	/* addiu/daddiu sp,sp,-imm */
273 	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
274 		return 0;
275 	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
276 		return 1;
277 #endif
278 	return 0;
279 }
280 
281 static int get_frame_info(struct mips_frame_info *info)
282 {
283 #ifdef CONFIG_CPU_MICROMIPS
284 	union mips_instruction *ip = (void *) (((char *) info->func) - 1);
285 #else
286 	union mips_instruction *ip = info->func;
287 #endif
288 	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
289 	unsigned i;
290 
291 	info->pc_offset = -1;
292 	info->frame_size = 0;
293 
294 	if (!ip)
295 		goto err;
296 
297 	if (max_insns == 0)
298 		max_insns = 128U;	/* unknown function size */
299 	max_insns = min(128U, max_insns);
300 
301 	for (i = 0; i < max_insns; i++, ip++) {
302 
303 		if (is_jump_ins(ip))
304 			break;
305 		if (!info->frame_size) {
306 			if (is_sp_move_ins(ip))
307 			{
308 #ifdef CONFIG_CPU_MICROMIPS
309 				if (mm_insn_16bit(ip->halfword[0]))
310 				{
311 					unsigned short tmp;
312 
313 					if (ip->halfword[0] & mm_addiusp_func)
314 					{
315 						tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
316 						info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
317 					} else {
318 						tmp = (ip->halfword[0] >> 1);
319 						info->frame_size = -(signed short)(tmp & 0xf);
320 					}
321 					ip = (void *) &ip->halfword[1];
322 					ip--;
323 				} else
324 #endif
325 				info->frame_size = - ip->i_format.simmediate;
326 			}
327 			continue;
328 		}
329 		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
330 			info->pc_offset =
331 				ip->i_format.simmediate / sizeof(long);
332 			break;
333 		}
334 	}
335 	if (info->frame_size && info->pc_offset >= 0) /* nested */
336 		return 0;
337 	if (info->pc_offset < 0) /* leaf */
338 		return 1;
339 	/* prologue seems boggus... */
340 err:
341 	return -1;
342 }
343 
344 static struct mips_frame_info schedule_mfi __read_mostly;
345 
346 #ifdef CONFIG_KALLSYMS
347 static unsigned long get___schedule_addr(void)
348 {
349 	return kallsyms_lookup_name("__schedule");
350 }
351 #else
352 static unsigned long get___schedule_addr(void)
353 {
354 	union mips_instruction *ip = (void *)schedule;
355 	int max_insns = 8;
356 	int i;
357 
358 	for (i = 0; i < max_insns; i++, ip++) {
359 		if (ip->j_format.opcode == j_op)
360 			return J_TARGET(ip, ip->j_format.target);
361 	}
362 	return 0;
363 }
364 #endif
365 
366 static int __init frame_info_init(void)
367 {
368 	unsigned long size = 0;
369 #ifdef CONFIG_KALLSYMS
370 	unsigned long ofs;
371 #endif
372 	unsigned long addr;
373 
374 	addr = get___schedule_addr();
375 	if (!addr)
376 		addr = (unsigned long)schedule;
377 
378 #ifdef CONFIG_KALLSYMS
379 	kallsyms_lookup_size_offset(addr, &size, &ofs);
380 #endif
381 	schedule_mfi.func = (void *)addr;
382 	schedule_mfi.func_size = size;
383 
384 	get_frame_info(&schedule_mfi);
385 
386 	/*
387 	 * Without schedule() frame info, result given by
388 	 * thread_saved_pc() and get_wchan() are not reliable.
389 	 */
390 	if (schedule_mfi.pc_offset < 0)
391 		printk("Can't analyze schedule() prologue at %p\n", schedule);
392 
393 	return 0;
394 }
395 
396 arch_initcall(frame_info_init);
397 
398 /*
399  * Return saved PC of a blocked thread.
400  */
401 unsigned long thread_saved_pc(struct task_struct *tsk)
402 {
403 	struct thread_struct *t = &tsk->thread;
404 
405 	/* New born processes are a special case */
406 	if (t->reg31 == (unsigned long) ret_from_fork)
407 		return t->reg31;
408 	if (schedule_mfi.pc_offset < 0)
409 		return 0;
410 	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
411 }
412 
413 
414 #ifdef CONFIG_KALLSYMS
415 /* generic stack unwinding function */
416 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
417 					      unsigned long *sp,
418 					      unsigned long pc,
419 					      unsigned long *ra)
420 {
421 	struct mips_frame_info info;
422 	unsigned long size, ofs;
423 	int leaf;
424 	extern void ret_from_irq(void);
425 	extern void ret_from_exception(void);
426 
427 	if (!stack_page)
428 		return 0;
429 
430 	/*
431 	 * If we reached the bottom of interrupt context,
432 	 * return saved pc in pt_regs.
433 	 */
434 	if (pc == (unsigned long)ret_from_irq ||
435 	    pc == (unsigned long)ret_from_exception) {
436 		struct pt_regs *regs;
437 		if (*sp >= stack_page &&
438 		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
439 			regs = (struct pt_regs *)*sp;
440 			pc = regs->cp0_epc;
441 			if (__kernel_text_address(pc)) {
442 				*sp = regs->regs[29];
443 				*ra = regs->regs[31];
444 				return pc;
445 			}
446 		}
447 		return 0;
448 	}
449 	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
450 		return 0;
451 	/*
452 	 * Return ra if an exception occurred at the first instruction
453 	 */
454 	if (unlikely(ofs == 0)) {
455 		pc = *ra;
456 		*ra = 0;
457 		return pc;
458 	}
459 
460 	info.func = (void *)(pc - ofs);
461 	info.func_size = ofs;	/* analyze from start to ofs */
462 	leaf = get_frame_info(&info);
463 	if (leaf < 0)
464 		return 0;
465 
466 	if (*sp < stack_page ||
467 	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
468 		return 0;
469 
470 	if (leaf)
471 		/*
472 		 * For some extreme cases, get_frame_info() can
473 		 * consider wrongly a nested function as a leaf
474 		 * one. In that cases avoid to return always the
475 		 * same value.
476 		 */
477 		pc = pc != *ra ? *ra : 0;
478 	else
479 		pc = ((unsigned long *)(*sp))[info.pc_offset];
480 
481 	*sp += info.frame_size;
482 	*ra = 0;
483 	return __kernel_text_address(pc) ? pc : 0;
484 }
485 EXPORT_SYMBOL(unwind_stack_by_address);
486 
487 /* used by show_backtrace() */
488 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
489 			   unsigned long pc, unsigned long *ra)
490 {
491 	unsigned long stack_page = (unsigned long)task_stack_page(task);
492 	return unwind_stack_by_address(stack_page, sp, pc, ra);
493 }
494 #endif
495 
496 /*
497  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
498  */
499 unsigned long get_wchan(struct task_struct *task)
500 {
501 	unsigned long pc = 0;
502 #ifdef CONFIG_KALLSYMS
503 	unsigned long sp;
504 	unsigned long ra = 0;
505 #endif
506 
507 	if (!task || task == current || task->state == TASK_RUNNING)
508 		goto out;
509 	if (!task_stack_page(task))
510 		goto out;
511 
512 	pc = thread_saved_pc(task);
513 
514 #ifdef CONFIG_KALLSYMS
515 	sp = task->thread.reg29 + schedule_mfi.frame_size;
516 
517 	while (in_sched_functions(pc))
518 		pc = unwind_stack(task, &sp, pc, &ra);
519 #endif
520 
521 out:
522 	return pc;
523 }
524 
525 /*
526  * Don't forget that the stack pointer must be aligned on a 8 bytes
527  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
528  */
529 unsigned long arch_align_stack(unsigned long sp)
530 {
531 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
532 		sp -= get_random_int() & ~PAGE_MASK;
533 
534 	return sp & ALMASK;
535 }
536 
537 static void arch_dump_stack(void *info)
538 {
539 	struct pt_regs *regs;
540 
541 	regs = get_irq_regs();
542 
543 	if (regs)
544 		show_regs(regs);
545 
546 	dump_stack();
547 }
548 
549 void arch_trigger_all_cpu_backtrace(bool include_self)
550 {
551 	smp_call_function(arch_dump_stack, NULL, 1);
552 }
553