xref: /openbmc/linux/arch/mips/kernel/process.c (revision 4a44a19b) 
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 
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_USEDMSA);
70 	clear_thread_flag(TIF_MSA_CTX_LIVE);
71 	disable_msa();
72 	regs->cp0_epc = pc;
73 	regs->regs[29] = sp;
74 }
75 
76 void exit_thread(void)
77 {
78 }
79 
80 void flush_thread(void)
81 {
82 }
83 
84 int copy_thread(unsigned long clone_flags, unsigned long usp,
85 	unsigned long arg, struct task_struct *p)
86 {
87 	struct thread_info *ti = task_thread_info(p);
88 	struct pt_regs *childregs, *regs = current_pt_regs();
89 	unsigned long childksp;
90 	p->set_child_tid = p->clear_child_tid = NULL;
91 
92 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
93 
94 	preempt_disable();
95 
96 	if (is_msa_enabled())
97 		save_msa(p);
98 	else if (is_fpu_owner())
99 		save_fp(p);
100 
101 	if (cpu_has_dsp)
102 		save_dsp(p);
103 
104 	preempt_enable();
105 
106 	/* set up new TSS. */
107 	childregs = (struct pt_regs *) childksp - 1;
108 	/*  Put the stack after the struct pt_regs.  */
109 	childksp = (unsigned long) childregs;
110 	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
111 	if (unlikely(p->flags & PF_KTHREAD)) {
112 		unsigned long status = p->thread.cp0_status;
113 		memset(childregs, 0, sizeof(struct pt_regs));
114 		ti->addr_limit = KERNEL_DS;
115 		p->thread.reg16 = usp; /* fn */
116 		p->thread.reg17 = arg;
117 		p->thread.reg29 = childksp;
118 		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
119 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
120 		status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
121 			 ((status & (ST0_KUC | ST0_IEC)) << 2);
122 #else
123 		status |= ST0_EXL;
124 #endif
125 		childregs->cp0_status = status;
126 		return 0;
127 	}
128 	*childregs = *regs;
129 	childregs->regs[7] = 0; /* Clear error flag */
130 	childregs->regs[2] = 0; /* Child gets zero as return value */
131 	if (usp)
132 		childregs->regs[29] = usp;
133 	ti->addr_limit = USER_DS;
134 
135 	p->thread.reg29 = (unsigned long) childregs;
136 	p->thread.reg31 = (unsigned long) ret_from_fork;
137 
138 	/*
139 	 * New tasks lose permission to use the fpu. This accelerates context
140 	 * switching for most programs since they don't use the fpu.
141 	 */
142 	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
143 
144 	clear_tsk_thread_flag(p, TIF_USEDFPU);
145 	clear_tsk_thread_flag(p, TIF_USEDMSA);
146 	clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);
147 
148 #ifdef CONFIG_MIPS_MT_FPAFF
149 	clear_tsk_thread_flag(p, TIF_FPUBOUND);
150 #endif /* CONFIG_MIPS_MT_FPAFF */
151 
152 	if (clone_flags & CLONE_SETTLS)
153 		ti->tp_value = regs->regs[7];
154 
155 	return 0;
156 }
157 
158 #ifdef CONFIG_CC_STACKPROTECTOR
159 #include <linux/stackprotector.h>
160 unsigned long __stack_chk_guard __read_mostly;
161 EXPORT_SYMBOL(__stack_chk_guard);
162 #endif
163 
164 struct mips_frame_info {
165 	void		*func;
166 	unsigned long	func_size;
167 	int		frame_size;
168 	int		pc_offset;
169 };
170 
171 #define J_TARGET(pc,target)	\
172 		(((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
173 
174 static inline int is_ra_save_ins(union mips_instruction *ip)
175 {
176 #ifdef CONFIG_CPU_MICROMIPS
177 	union mips_instruction mmi;
178 
179 	/*
180 	 * swsp ra,offset
181 	 * swm16 reglist,offset(sp)
182 	 * swm32 reglist,offset(sp)
183 	 * sw32 ra,offset(sp)
184 	 * jradiussp - NOT SUPPORTED
185 	 *
186 	 * microMIPS is way more fun...
187 	 */
188 	if (mm_insn_16bit(ip->halfword[0])) {
189 		mmi.word = (ip->halfword[0] << 16);
190 		return ((mmi.mm16_r5_format.opcode == mm_swsp16_op &&
191 			 mmi.mm16_r5_format.rt == 31) ||
192 			(mmi.mm16_m_format.opcode == mm_pool16c_op &&
193 			 mmi.mm16_m_format.func == mm_swm16_op));
194 	}
195 	else {
196 		mmi.halfword[0] = ip->halfword[1];
197 		mmi.halfword[1] = ip->halfword[0];
198 		return ((mmi.mm_m_format.opcode == mm_pool32b_op &&
199 			 mmi.mm_m_format.rd > 9 &&
200 			 mmi.mm_m_format.base == 29 &&
201 			 mmi.mm_m_format.func == mm_swm32_func) ||
202 			(mmi.i_format.opcode == mm_sw32_op &&
203 			 mmi.i_format.rs == 29 &&
204 			 mmi.i_format.rt == 31));
205 	}
206 #else
207 	/* sw / sd $ra, offset($sp) */
208 	return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
209 		ip->i_format.rs == 29 &&
210 		ip->i_format.rt == 31;
211 #endif
212 }
213 
214 static inline int is_jump_ins(union mips_instruction *ip)
215 {
216 #ifdef CONFIG_CPU_MICROMIPS
217 	/*
218 	 * jr16,jrc,jalr16,jalr16
219 	 * jal
220 	 * jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
221 	 * jraddiusp - NOT SUPPORTED
222 	 *
223 	 * microMIPS is kind of more fun...
224 	 */
225 	union mips_instruction mmi;
226 
227 	mmi.word = (ip->halfword[0] << 16);
228 
229 	if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
230 	    (mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
231 	    ip->j_format.opcode == mm_jal32_op)
232 		return 1;
233 	if (ip->r_format.opcode != mm_pool32a_op ||
234 			ip->r_format.func != mm_pool32axf_op)
235 		return 0;
236 	return (((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op);
237 #else
238 	if (ip->j_format.opcode == j_op)
239 		return 1;
240 	if (ip->j_format.opcode == jal_op)
241 		return 1;
242 	if (ip->r_format.opcode != spec_op)
243 		return 0;
244 	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
245 #endif
246 }
247 
248 static inline int is_sp_move_ins(union mips_instruction *ip)
249 {
250 #ifdef CONFIG_CPU_MICROMIPS
251 	/*
252 	 * addiusp -imm
253 	 * addius5 sp,-imm
254 	 * addiu32 sp,sp,-imm
255 	 * jradiussp - NOT SUPPORTED
256 	 *
257 	 * microMIPS is not more fun...
258 	 */
259 	if (mm_insn_16bit(ip->halfword[0])) {
260 		union mips_instruction mmi;
261 
262 		mmi.word = (ip->halfword[0] << 16);
263 		return ((mmi.mm16_r3_format.opcode == mm_pool16d_op &&
264 			 mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
265 			(mmi.mm16_r5_format.opcode == mm_pool16d_op &&
266 			 mmi.mm16_r5_format.rt == 29));
267 	}
268 	return (ip->mm_i_format.opcode == mm_addiu32_op &&
269 		 ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29);
270 #else
271 	/* addiu/daddiu sp,sp,-imm */
272 	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
273 		return 0;
274 	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
275 		return 1;
276 #endif
277 	return 0;
278 }
279 
280 static int get_frame_info(struct mips_frame_info *info)
281 {
282 #ifdef CONFIG_CPU_MICROMIPS
283 	union mips_instruction *ip = (void *) (((char *) info->func) - 1);
284 #else
285 	union mips_instruction *ip = info->func;
286 #endif
287 	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
288 	unsigned i;
289 
290 	info->pc_offset = -1;
291 	info->frame_size = 0;
292 
293 	if (!ip)
294 		goto err;
295 
296 	if (max_insns == 0)
297 		max_insns = 128U;	/* unknown function size */
298 	max_insns = min(128U, max_insns);
299 
300 	for (i = 0; i < max_insns; i++, ip++) {
301 
302 		if (is_jump_ins(ip))
303 			break;
304 		if (!info->frame_size) {
305 			if (is_sp_move_ins(ip))
306 			{
307 #ifdef CONFIG_CPU_MICROMIPS
308 				if (mm_insn_16bit(ip->halfword[0]))
309 				{
310 					unsigned short tmp;
311 
312 					if (ip->halfword[0] & mm_addiusp_func)
313 					{
314 						tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
315 						info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
316 					} else {
317 						tmp = (ip->halfword[0] >> 1);
318 						info->frame_size = -(signed short)(tmp & 0xf);
319 					}
320 					ip = (void *) &ip->halfword[1];
321 					ip--;
322 				} else
323 #endif
324 				info->frame_size = - ip->i_format.simmediate;
325 			}
326 			continue;
327 		}
328 		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
329 			info->pc_offset =
330 				ip->i_format.simmediate / sizeof(long);
331 			break;
332 		}
333 	}
334 	if (info->frame_size && info->pc_offset >= 0) /* nested */
335 		return 0;
336 	if (info->pc_offset < 0) /* leaf */
337 		return 1;
338 	/* prologue seems boggus... */
339 err:
340 	return -1;
341 }
342 
343 static struct mips_frame_info schedule_mfi __read_mostly;
344 
345 #ifdef CONFIG_KALLSYMS
346 static unsigned long get___schedule_addr(void)
347 {
348 	return kallsyms_lookup_name("__schedule");
349 }
350 #else
351 static unsigned long get___schedule_addr(void)
352 {
353 	union mips_instruction *ip = (void *)schedule;
354 	int max_insns = 8;
355 	int i;
356 
357 	for (i = 0; i < max_insns; i++, ip++) {
358 		if (ip->j_format.opcode == j_op)
359 			return J_TARGET(ip, ip->j_format.target);
360 	}
361 	return 0;
362 }
363 #endif
364 
365 static int __init frame_info_init(void)
366 {
367 	unsigned long size = 0;
368 #ifdef CONFIG_KALLSYMS
369 	unsigned long ofs;
370 #endif
371 	unsigned long addr;
372 
373 	addr = get___schedule_addr();
374 	if (!addr)
375 		addr = (unsigned long)schedule;
376 
377 #ifdef CONFIG_KALLSYMS
378 	kallsyms_lookup_size_offset(addr, &size, &ofs);
379 #endif
380 	schedule_mfi.func = (void *)addr;
381 	schedule_mfi.func_size = size;
382 
383 	get_frame_info(&schedule_mfi);
384 
385 	/*
386 	 * Without schedule() frame info, result given by
387 	 * thread_saved_pc() and get_wchan() are not reliable.
388 	 */
389 	if (schedule_mfi.pc_offset < 0)
390 		printk("Can't analyze schedule() prologue at %p\n", schedule);
391 
392 	return 0;
393 }
394 
395 arch_initcall(frame_info_init);
396 
397 /*
398  * Return saved PC of a blocked thread.
399  */
400 unsigned long thread_saved_pc(struct task_struct *tsk)
401 {
402 	struct thread_struct *t = &tsk->thread;
403 
404 	/* New born processes are a special case */
405 	if (t->reg31 == (unsigned long) ret_from_fork)
406 		return t->reg31;
407 	if (schedule_mfi.pc_offset < 0)
408 		return 0;
409 	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
410 }
411 
412 
413 #ifdef CONFIG_KALLSYMS
414 /* generic stack unwinding function */
415 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
416 					      unsigned long *sp,
417 					      unsigned long pc,
418 					      unsigned long *ra)
419 {
420 	struct mips_frame_info info;
421 	unsigned long size, ofs;
422 	int leaf;
423 	extern void ret_from_irq(void);
424 	extern void ret_from_exception(void);
425 
426 	if (!stack_page)
427 		return 0;
428 
429 	/*
430 	 * If we reached the bottom of interrupt context,
431 	 * return saved pc in pt_regs.
432 	 */
433 	if (pc == (unsigned long)ret_from_irq ||
434 	    pc == (unsigned long)ret_from_exception) {
435 		struct pt_regs *regs;
436 		if (*sp >= stack_page &&
437 		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
438 			regs = (struct pt_regs *)*sp;
439 			pc = regs->cp0_epc;
440 			if (__kernel_text_address(pc)) {
441 				*sp = regs->regs[29];
442 				*ra = regs->regs[31];
443 				return pc;
444 			}
445 		}
446 		return 0;
447 	}
448 	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
449 		return 0;
450 	/*
451 	 * Return ra if an exception occurred at the first instruction
452 	 */
453 	if (unlikely(ofs == 0)) {
454 		pc = *ra;
455 		*ra = 0;
456 		return pc;
457 	}
458 
459 	info.func = (void *)(pc - ofs);
460 	info.func_size = ofs;	/* analyze from start to ofs */
461 	leaf = get_frame_info(&info);
462 	if (leaf < 0)
463 		return 0;
464 
465 	if (*sp < stack_page ||
466 	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
467 		return 0;
468 
469 	if (leaf)
470 		/*
471 		 * For some extreme cases, get_frame_info() can
472 		 * consider wrongly a nested function as a leaf
473 		 * one. In that cases avoid to return always the
474 		 * same value.
475 		 */
476 		pc = pc != *ra ? *ra : 0;
477 	else
478 		pc = ((unsigned long *)(*sp))[info.pc_offset];
479 
480 	*sp += info.frame_size;
481 	*ra = 0;
482 	return __kernel_text_address(pc) ? pc : 0;
483 }
484 EXPORT_SYMBOL(unwind_stack_by_address);
485 
486 /* used by show_backtrace() */
487 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
488 			   unsigned long pc, unsigned long *ra)
489 {
490 	unsigned long stack_page = (unsigned long)task_stack_page(task);
491 	return unwind_stack_by_address(stack_page, sp, pc, ra);
492 }
493 #endif
494 
495 /*
496  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
497  */
498 unsigned long get_wchan(struct task_struct *task)
499 {
500 	unsigned long pc = 0;
501 #ifdef CONFIG_KALLSYMS
502 	unsigned long sp;
503 	unsigned long ra = 0;
504 #endif
505 
506 	if (!task || task == current || task->state == TASK_RUNNING)
507 		goto out;
508 	if (!task_stack_page(task))
509 		goto out;
510 
511 	pc = thread_saved_pc(task);
512 
513 #ifdef CONFIG_KALLSYMS
514 	sp = task->thread.reg29 + schedule_mfi.frame_size;
515 
516 	while (in_sched_functions(pc))
517 		pc = unwind_stack(task, &sp, pc, &ra);
518 #endif
519 
520 out:
521 	return pc;
522 }
523 
524 /*
525  * Don't forget that the stack pointer must be aligned on a 8 bytes
526  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
527  */
528 unsigned long arch_align_stack(unsigned long sp)
529 {
530 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
531 		sp -= get_random_int() & ~PAGE_MASK;
532 
533 	return sp & ALMASK;
534 }
535