xref: /linux/arch/mips/kernel/process.c (revision 4413e16d9d21673bb5048a2e542f1aaa00015c2e) 
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  */
11 #include <linux/errno.h>
12 #include <linux/sched.h>
13 #include <linux/tick.h>
14 #include <linux/kernel.h>
15 #include <linux/mm.h>
16 #include <linux/stddef.h>
17 #include <linux/unistd.h>
18 #include <linux/export.h>
19 #include <linux/ptrace.h>
20 #include <linux/mman.h>
21 #include <linux/personality.h>
22 #include <linux/sys.h>
23 #include <linux/user.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/pgtable.h>
35 #include <asm/mipsregs.h>
36 #include <asm/processor.h>
37 #include <asm/uaccess.h>
38 #include <asm/io.h>
39 #include <asm/elf.h>
40 #include <asm/isadep.h>
41 #include <asm/inst.h>
42 #include <asm/stacktrace.h>
43 
44 /*
45  * The idle thread. There's no useful work to be done, so just try to conserve
46  * power and have a low exit latency (ie sit in a loop waiting for somebody to
47  * say that they'd like to reschedule)
48  */
49 void __noreturn cpu_idle(void)
50 {
51 	int cpu;
52 
53 	/* CPU is going idle. */
54 	cpu = smp_processor_id();
55 
56 	/* endless idle loop with no priority at all */
57 	while (1) {
58 		tick_nohz_idle_enter();
59 		rcu_idle_enter();
60 		while (!need_resched() && cpu_online(cpu)) {
61 #ifdef CONFIG_MIPS_MT_SMTC
62 			extern void smtc_idle_loop_hook(void);
63 
64 			smtc_idle_loop_hook();
65 #endif
66 
67 			if (cpu_wait) {
68 				/* Don't trace irqs off for idle */
69 				stop_critical_timings();
70 				(*cpu_wait)();
71 				start_critical_timings();
72 			}
73 		}
74 #ifdef CONFIG_HOTPLUG_CPU
75 		if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
76 		    (system_state == SYSTEM_RUNNING ||
77 		     system_state == SYSTEM_BOOTING))
78 			play_dead();
79 #endif
80 		rcu_idle_exit();
81 		tick_nohz_idle_exit();
82 		schedule_preempt_disabled();
83 	}
84 }
85 
86 asmlinkage void ret_from_fork(void);
87 
88 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
89 {
90 	unsigned long status;
91 
92 	/* New thread loses kernel privileges. */
93 	status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
94 #ifdef CONFIG_64BIT
95 	status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
96 #endif
97 	status |= KU_USER;
98 	regs->cp0_status = status;
99 	clear_used_math();
100 	clear_fpu_owner();
101 	if (cpu_has_dsp)
102 		__init_dsp();
103 	regs->cp0_epc = pc;
104 	regs->regs[29] = sp;
105 }
106 
107 void exit_thread(void)
108 {
109 }
110 
111 void flush_thread(void)
112 {
113 }
114 
115 int copy_thread(unsigned long clone_flags, unsigned long usp,
116 	unsigned long unused, struct task_struct *p, struct pt_regs *regs)
117 {
118 	struct thread_info *ti = task_thread_info(p);
119 	struct pt_regs *childregs;
120 	unsigned long childksp;
121 	p->set_child_tid = p->clear_child_tid = NULL;
122 
123 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
124 
125 	preempt_disable();
126 
127 	if (is_fpu_owner())
128 		save_fp(p);
129 
130 	if (cpu_has_dsp)
131 		save_dsp(p);
132 
133 	preempt_enable();
134 
135 	/* set up new TSS. */
136 	childregs = (struct pt_regs *) childksp - 1;
137 	/*  Put the stack after the struct pt_regs.  */
138 	childksp = (unsigned long) childregs;
139 	*childregs = *regs;
140 	childregs->regs[7] = 0;	/* Clear error flag */
141 
142 	childregs->regs[2] = 0;	/* Child gets zero as return value */
143 
144 	if (childregs->cp0_status & ST0_CU0) {
145 		childregs->regs[28] = (unsigned long) ti;
146 		childregs->regs[29] = childksp;
147 		ti->addr_limit = KERNEL_DS;
148 	} else {
149 		childregs->regs[29] = usp;
150 		ti->addr_limit = USER_DS;
151 	}
152 	p->thread.reg29 = (unsigned long) childregs;
153 	p->thread.reg31 = (unsigned long) ret_from_fork;
154 
155 	/*
156 	 * New tasks lose permission to use the fpu. This accelerates context
157 	 * switching for most programs since they don't use the fpu.
158 	 */
159 	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
160 	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
161 
162 #ifdef CONFIG_MIPS_MT_SMTC
163 	/*
164 	 * SMTC restores TCStatus after Status, and the CU bits
165 	 * are aliased there.
166 	 */
167 	childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
168 #endif
169 	clear_tsk_thread_flag(p, TIF_USEDFPU);
170 
171 #ifdef CONFIG_MIPS_MT_FPAFF
172 	clear_tsk_thread_flag(p, TIF_FPUBOUND);
173 #endif /* CONFIG_MIPS_MT_FPAFF */
174 
175 	if (clone_flags & CLONE_SETTLS)
176 		ti->tp_value = regs->regs[7];
177 
178 	return 0;
179 }
180 
181 /* Fill in the fpu structure for a core dump.. */
182 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
183 {
184 	memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
185 
186 	return 1;
187 }
188 
189 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
190 {
191 	int i;
192 
193 	for (i = 0; i < EF_R0; i++)
194 		gp[i] = 0;
195 	gp[EF_R0] = 0;
196 	for (i = 1; i <= 31; i++)
197 		gp[EF_R0 + i] = regs->regs[i];
198 	gp[EF_R26] = 0;
199 	gp[EF_R27] = 0;
200 	gp[EF_LO] = regs->lo;
201 	gp[EF_HI] = regs->hi;
202 	gp[EF_CP0_EPC] = regs->cp0_epc;
203 	gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
204 	gp[EF_CP0_STATUS] = regs->cp0_status;
205 	gp[EF_CP0_CAUSE] = regs->cp0_cause;
206 #ifdef EF_UNUSED0
207 	gp[EF_UNUSED0] = 0;
208 #endif
209 }
210 
211 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
212 {
213 	elf_dump_regs(*regs, task_pt_regs(tsk));
214 	return 1;
215 }
216 
217 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
218 {
219 	memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
220 
221 	return 1;
222 }
223 
224 /*
225  * Create a kernel thread
226  */
227 static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
228 {
229 	do_exit(fn(arg));
230 }
231 
232 long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
233 {
234 	struct pt_regs regs;
235 
236 	memset(&regs, 0, sizeof(regs));
237 
238 	regs.regs[4] = (unsigned long) arg;
239 	regs.regs[5] = (unsigned long) fn;
240 	regs.cp0_epc = (unsigned long) kernel_thread_helper;
241 	regs.cp0_status = read_c0_status();
242 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
243 	regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
244 			  ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
245 #else
246 	regs.cp0_status |= ST0_EXL;
247 #endif
248 
249 	/* Ok, create the new process.. */
250 	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
251 }
252 
253 /*
254  *
255  */
256 struct mips_frame_info {
257 	void		*func;
258 	unsigned long	func_size;
259 	int		frame_size;
260 	int		pc_offset;
261 };
262 
263 static inline int is_ra_save_ins(union mips_instruction *ip)
264 {
265 	/* sw / sd $ra, offset($sp) */
266 	return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
267 		ip->i_format.rs == 29 &&
268 		ip->i_format.rt == 31;
269 }
270 
271 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
272 {
273 	if (ip->j_format.opcode == jal_op)
274 		return 1;
275 	if (ip->r_format.opcode != spec_op)
276 		return 0;
277 	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
278 }
279 
280 static inline int is_sp_move_ins(union mips_instruction *ip)
281 {
282 	/* addiu/daddiu sp,sp,-imm */
283 	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
284 		return 0;
285 	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
286 		return 1;
287 	return 0;
288 }
289 
290 static int get_frame_info(struct mips_frame_info *info)
291 {
292 	union mips_instruction *ip = info->func;
293 	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
294 	unsigned i;
295 
296 	info->pc_offset = -1;
297 	info->frame_size = 0;
298 
299 	if (!ip)
300 		goto err;
301 
302 	if (max_insns == 0)
303 		max_insns = 128U;	/* unknown function size */
304 	max_insns = min(128U, max_insns);
305 
306 	for (i = 0; i < max_insns; i++, ip++) {
307 
308 		if (is_jal_jalr_jr_ins(ip))
309 			break;
310 		if (!info->frame_size) {
311 			if (is_sp_move_ins(ip))
312 				info->frame_size = - ip->i_format.simmediate;
313 			continue;
314 		}
315 		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
316 			info->pc_offset =
317 				ip->i_format.simmediate / sizeof(long);
318 			break;
319 		}
320 	}
321 	if (info->frame_size && info->pc_offset >= 0) /* nested */
322 		return 0;
323 	if (info->pc_offset < 0) /* leaf */
324 		return 1;
325 	/* prologue seems boggus... */
326 err:
327 	return -1;
328 }
329 
330 static struct mips_frame_info schedule_mfi __read_mostly;
331 
332 static int __init frame_info_init(void)
333 {
334 	unsigned long size = 0;
335 #ifdef CONFIG_KALLSYMS
336 	unsigned long ofs;
337 
338 	kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
339 #endif
340 	schedule_mfi.func = schedule;
341 	schedule_mfi.func_size = size;
342 
343 	get_frame_info(&schedule_mfi);
344 
345 	/*
346 	 * Without schedule() frame info, result given by
347 	 * thread_saved_pc() and get_wchan() are not reliable.
348 	 */
349 	if (schedule_mfi.pc_offset < 0)
350 		printk("Can't analyze schedule() prologue at %p\n", schedule);
351 
352 	return 0;
353 }
354 
355 arch_initcall(frame_info_init);
356 
357 /*
358  * Return saved PC of a blocked thread.
359  */
360 unsigned long thread_saved_pc(struct task_struct *tsk)
361 {
362 	struct thread_struct *t = &tsk->thread;
363 
364 	/* New born processes are a special case */
365 	if (t->reg31 == (unsigned long) ret_from_fork)
366 		return t->reg31;
367 	if (schedule_mfi.pc_offset < 0)
368 		return 0;
369 	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
370 }
371 
372 
373 #ifdef CONFIG_KALLSYMS
374 /* generic stack unwinding function */
375 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
376 					      unsigned long *sp,
377 					      unsigned long pc,
378 					      unsigned long *ra)
379 {
380 	struct mips_frame_info info;
381 	unsigned long size, ofs;
382 	int leaf;
383 	extern void ret_from_irq(void);
384 	extern void ret_from_exception(void);
385 
386 	if (!stack_page)
387 		return 0;
388 
389 	/*
390 	 * If we reached the bottom of interrupt context,
391 	 * return saved pc in pt_regs.
392 	 */
393 	if (pc == (unsigned long)ret_from_irq ||
394 	    pc == (unsigned long)ret_from_exception) {
395 		struct pt_regs *regs;
396 		if (*sp >= stack_page &&
397 		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
398 			regs = (struct pt_regs *)*sp;
399 			pc = regs->cp0_epc;
400 			if (__kernel_text_address(pc)) {
401 				*sp = regs->regs[29];
402 				*ra = regs->regs[31];
403 				return pc;
404 			}
405 		}
406 		return 0;
407 	}
408 	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
409 		return 0;
410 	/*
411 	 * Return ra if an exception occurred at the first instruction
412 	 */
413 	if (unlikely(ofs == 0)) {
414 		pc = *ra;
415 		*ra = 0;
416 		return pc;
417 	}
418 
419 	info.func = (void *)(pc - ofs);
420 	info.func_size = ofs;	/* analyze from start to ofs */
421 	leaf = get_frame_info(&info);
422 	if (leaf < 0)
423 		return 0;
424 
425 	if (*sp < stack_page ||
426 	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
427 		return 0;
428 
429 	if (leaf)
430 		/*
431 		 * For some extreme cases, get_frame_info() can
432 		 * consider wrongly a nested function as a leaf
433 		 * one. In that cases avoid to return always the
434 		 * same value.
435 		 */
436 		pc = pc != *ra ? *ra : 0;
437 	else
438 		pc = ((unsigned long *)(*sp))[info.pc_offset];
439 
440 	*sp += info.frame_size;
441 	*ra = 0;
442 	return __kernel_text_address(pc) ? pc : 0;
443 }
444 EXPORT_SYMBOL(unwind_stack_by_address);
445 
446 /* used by show_backtrace() */
447 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
448 			   unsigned long pc, unsigned long *ra)
449 {
450 	unsigned long stack_page = (unsigned long)task_stack_page(task);
451 	return unwind_stack_by_address(stack_page, sp, pc, ra);
452 }
453 #endif
454 
455 /*
456  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
457  */
458 unsigned long get_wchan(struct task_struct *task)
459 {
460 	unsigned long pc = 0;
461 #ifdef CONFIG_KALLSYMS
462 	unsigned long sp;
463 	unsigned long ra = 0;
464 #endif
465 
466 	if (!task || task == current || task->state == TASK_RUNNING)
467 		goto out;
468 	if (!task_stack_page(task))
469 		goto out;
470 
471 	pc = thread_saved_pc(task);
472 
473 #ifdef CONFIG_KALLSYMS
474 	sp = task->thread.reg29 + schedule_mfi.frame_size;
475 
476 	while (in_sched_functions(pc))
477 		pc = unwind_stack(task, &sp, pc, &ra);
478 #endif
479 
480 out:
481 	return pc;
482 }
483 
484 /*
485  * Don't forget that the stack pointer must be aligned on a 8 bytes
486  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
487  */
488 unsigned long arch_align_stack(unsigned long sp)
489 {
490 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
491 		sp -= get_random_int() & ~PAGE_MASK;
492 
493 	return sp & ALMASK;
494 }
495