xref: /linux/arch/mips/kernel/process.c (revision a671de086874b9d8155369319b2bd989cf55d77c) 
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 asmlinkage void ret_from_kernel_thread(void);
88 
89 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
90 {
91 	unsigned long status;
92 
93 	/* New thread loses kernel privileges. */
94 	status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
95 #ifdef CONFIG_64BIT
96 	status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
97 #endif
98 	status |= KU_USER;
99 	regs->cp0_status = status;
100 	clear_used_math();
101 	clear_fpu_owner();
102 	if (cpu_has_dsp)
103 		__init_dsp();
104 	regs->cp0_epc = pc;
105 	regs->regs[29] = sp;
106 }
107 
108 void exit_thread(void)
109 {
110 }
111 
112 void flush_thread(void)
113 {
114 }
115 
116 int copy_thread(unsigned long clone_flags, unsigned long usp,
117 	unsigned long arg, struct task_struct *p)
118 {
119 	struct thread_info *ti = task_thread_info(p);
120 	struct pt_regs *childregs, *regs = current_pt_regs();
121 	unsigned long childksp;
122 	p->set_child_tid = p->clear_child_tid = NULL;
123 
124 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
125 
126 	preempt_disable();
127 
128 	if (is_fpu_owner())
129 		save_fp(p);
130 
131 	if (cpu_has_dsp)
132 		save_dsp(p);
133 
134 	preempt_enable();
135 
136 	/* set up new TSS. */
137 	childregs = (struct pt_regs *) childksp - 1;
138 	/*  Put the stack after the struct pt_regs.  */
139 	childksp = (unsigned long) childregs;
140 	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
141 	if (unlikely(p->flags & PF_KTHREAD)) {
142 		unsigned long status = p->thread.cp0_status;
143 		memset(childregs, 0, sizeof(struct pt_regs));
144 		ti->addr_limit = KERNEL_DS;
145 		p->thread.reg16 = usp; /* fn */
146 		p->thread.reg17 = arg;
147 		p->thread.reg29 = childksp;
148 		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
149 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
150 		status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
151 			 ((status & (ST0_KUC | ST0_IEC)) << 2);
152 #else
153 		status |= ST0_EXL;
154 #endif
155 		childregs->cp0_status = status;
156 		return 0;
157 	}
158 	*childregs = *regs;
159 	childregs->regs[7] = 0;	/* Clear error flag */
160 	childregs->regs[2] = 0;	/* Child gets zero as return value */
161 	childregs->regs[29] = usp;
162 	ti->addr_limit = USER_DS;
163 
164 	p->thread.reg29 = (unsigned long) childregs;
165 	p->thread.reg31 = (unsigned long) ret_from_fork;
166 
167 	/*
168 	 * New tasks lose permission to use the fpu. This accelerates context
169 	 * switching for most programs since they don't use the fpu.
170 	 */
171 	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
172 
173 #ifdef CONFIG_MIPS_MT_SMTC
174 	/*
175 	 * SMTC restores TCStatus after Status, and the CU bits
176 	 * are aliased there.
177 	 */
178 	childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
179 #endif
180 	clear_tsk_thread_flag(p, TIF_USEDFPU);
181 
182 #ifdef CONFIG_MIPS_MT_FPAFF
183 	clear_tsk_thread_flag(p, TIF_FPUBOUND);
184 #endif /* CONFIG_MIPS_MT_FPAFF */
185 
186 	if (clone_flags & CLONE_SETTLS)
187 		ti->tp_value = regs->regs[7];
188 
189 	return 0;
190 }
191 
192 /* Fill in the fpu structure for a core dump.. */
193 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
194 {
195 	memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
196 
197 	return 1;
198 }
199 
200 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
201 {
202 	int i;
203 
204 	for (i = 0; i < EF_R0; i++)
205 		gp[i] = 0;
206 	gp[EF_R0] = 0;
207 	for (i = 1; i <= 31; i++)
208 		gp[EF_R0 + i] = regs->regs[i];
209 	gp[EF_R26] = 0;
210 	gp[EF_R27] = 0;
211 	gp[EF_LO] = regs->lo;
212 	gp[EF_HI] = regs->hi;
213 	gp[EF_CP0_EPC] = regs->cp0_epc;
214 	gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
215 	gp[EF_CP0_STATUS] = regs->cp0_status;
216 	gp[EF_CP0_CAUSE] = regs->cp0_cause;
217 #ifdef EF_UNUSED0
218 	gp[EF_UNUSED0] = 0;
219 #endif
220 }
221 
222 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
223 {
224 	elf_dump_regs(*regs, task_pt_regs(tsk));
225 	return 1;
226 }
227 
228 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
229 {
230 	memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
231 
232 	return 1;
233 }
234 
235 /*
236  *
237  */
238 struct mips_frame_info {
239 	void		*func;
240 	unsigned long	func_size;
241 	int		frame_size;
242 	int		pc_offset;
243 };
244 
245 static inline int is_ra_save_ins(union mips_instruction *ip)
246 {
247 	/* sw / sd $ra, offset($sp) */
248 	return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
249 		ip->i_format.rs == 29 &&
250 		ip->i_format.rt == 31;
251 }
252 
253 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
254 {
255 	if (ip->j_format.opcode == jal_op)
256 		return 1;
257 	if (ip->r_format.opcode != spec_op)
258 		return 0;
259 	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
260 }
261 
262 static inline int is_sp_move_ins(union mips_instruction *ip)
263 {
264 	/* addiu/daddiu sp,sp,-imm */
265 	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
266 		return 0;
267 	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
268 		return 1;
269 	return 0;
270 }
271 
272 static int get_frame_info(struct mips_frame_info *info)
273 {
274 	union mips_instruction *ip = info->func;
275 	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
276 	unsigned i;
277 
278 	info->pc_offset = -1;
279 	info->frame_size = 0;
280 
281 	if (!ip)
282 		goto err;
283 
284 	if (max_insns == 0)
285 		max_insns = 128U;	/* unknown function size */
286 	max_insns = min(128U, max_insns);
287 
288 	for (i = 0; i < max_insns; i++, ip++) {
289 
290 		if (is_jal_jalr_jr_ins(ip))
291 			break;
292 		if (!info->frame_size) {
293 			if (is_sp_move_ins(ip))
294 				info->frame_size = - ip->i_format.simmediate;
295 			continue;
296 		}
297 		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
298 			info->pc_offset =
299 				ip->i_format.simmediate / sizeof(long);
300 			break;
301 		}
302 	}
303 	if (info->frame_size && info->pc_offset >= 0) /* nested */
304 		return 0;
305 	if (info->pc_offset < 0) /* leaf */
306 		return 1;
307 	/* prologue seems boggus... */
308 err:
309 	return -1;
310 }
311 
312 static struct mips_frame_info schedule_mfi __read_mostly;
313 
314 static int __init frame_info_init(void)
315 {
316 	unsigned long size = 0;
317 #ifdef CONFIG_KALLSYMS
318 	unsigned long ofs;
319 
320 	kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
321 #endif
322 	schedule_mfi.func = schedule;
323 	schedule_mfi.func_size = size;
324 
325 	get_frame_info(&schedule_mfi);
326 
327 	/*
328 	 * Without schedule() frame info, result given by
329 	 * thread_saved_pc() and get_wchan() are not reliable.
330 	 */
331 	if (schedule_mfi.pc_offset < 0)
332 		printk("Can't analyze schedule() prologue at %p\n", schedule);
333 
334 	return 0;
335 }
336 
337 arch_initcall(frame_info_init);
338 
339 /*
340  * Return saved PC of a blocked thread.
341  */
342 unsigned long thread_saved_pc(struct task_struct *tsk)
343 {
344 	struct thread_struct *t = &tsk->thread;
345 
346 	/* New born processes are a special case */
347 	if (t->reg31 == (unsigned long) ret_from_fork)
348 		return t->reg31;
349 	if (schedule_mfi.pc_offset < 0)
350 		return 0;
351 	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
352 }
353 
354 
355 #ifdef CONFIG_KALLSYMS
356 /* generic stack unwinding function */
357 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
358 					      unsigned long *sp,
359 					      unsigned long pc,
360 					      unsigned long *ra)
361 {
362 	struct mips_frame_info info;
363 	unsigned long size, ofs;
364 	int leaf;
365 	extern void ret_from_irq(void);
366 	extern void ret_from_exception(void);
367 
368 	if (!stack_page)
369 		return 0;
370 
371 	/*
372 	 * If we reached the bottom of interrupt context,
373 	 * return saved pc in pt_regs.
374 	 */
375 	if (pc == (unsigned long)ret_from_irq ||
376 	    pc == (unsigned long)ret_from_exception) {
377 		struct pt_regs *regs;
378 		if (*sp >= stack_page &&
379 		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
380 			regs = (struct pt_regs *)*sp;
381 			pc = regs->cp0_epc;
382 			if (__kernel_text_address(pc)) {
383 				*sp = regs->regs[29];
384 				*ra = regs->regs[31];
385 				return pc;
386 			}
387 		}
388 		return 0;
389 	}
390 	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
391 		return 0;
392 	/*
393 	 * Return ra if an exception occurred at the first instruction
394 	 */
395 	if (unlikely(ofs == 0)) {
396 		pc = *ra;
397 		*ra = 0;
398 		return pc;
399 	}
400 
401 	info.func = (void *)(pc - ofs);
402 	info.func_size = ofs;	/* analyze from start to ofs */
403 	leaf = get_frame_info(&info);
404 	if (leaf < 0)
405 		return 0;
406 
407 	if (*sp < stack_page ||
408 	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
409 		return 0;
410 
411 	if (leaf)
412 		/*
413 		 * For some extreme cases, get_frame_info() can
414 		 * consider wrongly a nested function as a leaf
415 		 * one. In that cases avoid to return always the
416 		 * same value.
417 		 */
418 		pc = pc != *ra ? *ra : 0;
419 	else
420 		pc = ((unsigned long *)(*sp))[info.pc_offset];
421 
422 	*sp += info.frame_size;
423 	*ra = 0;
424 	return __kernel_text_address(pc) ? pc : 0;
425 }
426 EXPORT_SYMBOL(unwind_stack_by_address);
427 
428 /* used by show_backtrace() */
429 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
430 			   unsigned long pc, unsigned long *ra)
431 {
432 	unsigned long stack_page = (unsigned long)task_stack_page(task);
433 	return unwind_stack_by_address(stack_page, sp, pc, ra);
434 }
435 #endif
436 
437 /*
438  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
439  */
440 unsigned long get_wchan(struct task_struct *task)
441 {
442 	unsigned long pc = 0;
443 #ifdef CONFIG_KALLSYMS
444 	unsigned long sp;
445 	unsigned long ra = 0;
446 #endif
447 
448 	if (!task || task == current || task->state == TASK_RUNNING)
449 		goto out;
450 	if (!task_stack_page(task))
451 		goto out;
452 
453 	pc = thread_saved_pc(task);
454 
455 #ifdef CONFIG_KALLSYMS
456 	sp = task->thread.reg29 + schedule_mfi.frame_size;
457 
458 	while (in_sched_functions(pc))
459 		pc = unwind_stack(task, &sp, pc, &ra);
460 #endif
461 
462 out:
463 	return pc;
464 }
465 
466 /*
467  * Don't forget that the stack pointer must be aligned on a 8 bytes
468  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
469  */
470 unsigned long arch_align_stack(unsigned long sp)
471 {
472 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
473 		sp -= get_random_int() & ~PAGE_MASK;
474 
475 	return sp & ALMASK;
476 }
477