xref: /openbmc/linux/arch/mips/kernel/process.c (revision 9c1f8594) 
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/module.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/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/system.h>
36 #include <asm/mipsregs.h>
37 #include <asm/processor.h>
38 #include <asm/uaccess.h>
39 #include <asm/io.h>
40 #include <asm/elf.h>
41 #include <asm/isadep.h>
42 #include <asm/inst.h>
43 #include <asm/stacktrace.h>
44 
45 /*
46  * The idle thread. There's no useful work to be done, so just try to conserve
47  * power and have a low exit latency (ie sit in a loop waiting for somebody to
48  * say that they'd like to reschedule)
49  */
50 void __noreturn cpu_idle(void)
51 {
52 	int cpu;
53 
54 	/* CPU is going idle. */
55 	cpu = smp_processor_id();
56 
57 	/* endless idle loop with no priority at all */
58 	while (1) {
59 		tick_nohz_stop_sched_tick(1);
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 		tick_nohz_restart_sched_tick();
81 		preempt_enable_no_resched();
82 		schedule();
83 		preempt_disable();
84 	}
85 }
86 
87 asmlinkage void ret_from_fork(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 unused, struct task_struct *p, struct pt_regs *regs)
118 {
119 	struct thread_info *ti = task_thread_info(p);
120 	struct pt_regs *childregs;
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 	*childregs = *regs;
141 	childregs->regs[7] = 0;	/* Clear error flag */
142 
143 	childregs->regs[2] = 0;	/* Child gets zero as return value */
144 
145 	if (childregs->cp0_status & ST0_CU0) {
146 		childregs->regs[28] = (unsigned long) ti;
147 		childregs->regs[29] = childksp;
148 		ti->addr_limit = KERNEL_DS;
149 	} else {
150 		childregs->regs[29] = usp;
151 		ti->addr_limit = USER_DS;
152 	}
153 	p->thread.reg29 = (unsigned long) childregs;
154 	p->thread.reg31 = (unsigned long) ret_from_fork;
155 
156 	/*
157 	 * New tasks lose permission to use the fpu. This accelerates context
158 	 * switching for most programs since they don't use the fpu.
159 	 */
160 	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
161 	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
162 
163 #ifdef CONFIG_MIPS_MT_SMTC
164 	/*
165 	 * SMTC restores TCStatus after Status, and the CU bits
166 	 * are aliased there.
167 	 */
168 	childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
169 #endif
170 	clear_tsk_thread_flag(p, TIF_USEDFPU);
171 
172 #ifdef CONFIG_MIPS_MT_FPAFF
173 	clear_tsk_thread_flag(p, TIF_FPUBOUND);
174 #endif /* CONFIG_MIPS_MT_FPAFF */
175 
176 	if (clone_flags & CLONE_SETTLS)
177 		ti->tp_value = regs->regs[7];
178 
179 	return 0;
180 }
181 
182 /* Fill in the fpu structure for a core dump.. */
183 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
184 {
185 	memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
186 
187 	return 1;
188 }
189 
190 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
191 {
192 	int i;
193 
194 	for (i = 0; i < EF_R0; i++)
195 		gp[i] = 0;
196 	gp[EF_R0] = 0;
197 	for (i = 1; i <= 31; i++)
198 		gp[EF_R0 + i] = regs->regs[i];
199 	gp[EF_R26] = 0;
200 	gp[EF_R27] = 0;
201 	gp[EF_LO] = regs->lo;
202 	gp[EF_HI] = regs->hi;
203 	gp[EF_CP0_EPC] = regs->cp0_epc;
204 	gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
205 	gp[EF_CP0_STATUS] = regs->cp0_status;
206 	gp[EF_CP0_CAUSE] = regs->cp0_cause;
207 #ifdef EF_UNUSED0
208 	gp[EF_UNUSED0] = 0;
209 #endif
210 }
211 
212 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
213 {
214 	elf_dump_regs(*regs, task_pt_regs(tsk));
215 	return 1;
216 }
217 
218 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
219 {
220 	memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
221 
222 	return 1;
223 }
224 
225 /*
226  * Create a kernel thread
227  */
228 static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
229 {
230 	do_exit(fn(arg));
231 }
232 
233 long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
234 {
235 	struct pt_regs regs;
236 
237 	memset(&regs, 0, sizeof(regs));
238 
239 	regs.regs[4] = (unsigned long) arg;
240 	regs.regs[5] = (unsigned long) fn;
241 	regs.cp0_epc = (unsigned long) kernel_thread_helper;
242 	regs.cp0_status = read_c0_status();
243 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
244 	regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
245 			  ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
246 #else
247 	regs.cp0_status |= ST0_EXL;
248 #endif
249 
250 	/* Ok, create the new process.. */
251 	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
252 }
253 
254 /*
255  *
256  */
257 struct mips_frame_info {
258 	void		*func;
259 	unsigned long	func_size;
260 	int		frame_size;
261 	int		pc_offset;
262 };
263 
264 static inline int is_ra_save_ins(union mips_instruction *ip)
265 {
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 }
271 
272 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
273 {
274 	if (ip->j_format.opcode == jal_op)
275 		return 1;
276 	if (ip->r_format.opcode != spec_op)
277 		return 0;
278 	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
279 }
280 
281 static inline int is_sp_move_ins(union mips_instruction *ip)
282 {
283 	/* addiu/daddiu sp,sp,-imm */
284 	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
285 		return 0;
286 	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
287 		return 1;
288 	return 0;
289 }
290 
291 static int get_frame_info(struct mips_frame_info *info)
292 {
293 	union mips_instruction *ip = info->func;
294 	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
295 	unsigned i;
296 
297 	info->pc_offset = -1;
298 	info->frame_size = 0;
299 
300 	if (!ip)
301 		goto err;
302 
303 	if (max_insns == 0)
304 		max_insns = 128U;	/* unknown function size */
305 	max_insns = min(128U, max_insns);
306 
307 	for (i = 0; i < max_insns; i++, ip++) {
308 
309 		if (is_jal_jalr_jr_ins(ip))
310 			break;
311 		if (!info->frame_size) {
312 			if (is_sp_move_ins(ip))
313 				info->frame_size = - ip->i_format.simmediate;
314 			continue;
315 		}
316 		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
317 			info->pc_offset =
318 				ip->i_format.simmediate / sizeof(long);
319 			break;
320 		}
321 	}
322 	if (info->frame_size && info->pc_offset >= 0) /* nested */
323 		return 0;
324 	if (info->pc_offset < 0) /* leaf */
325 		return 1;
326 	/* prologue seems boggus... */
327 err:
328 	return -1;
329 }
330 
331 static struct mips_frame_info schedule_mfi __read_mostly;
332 
333 static int __init frame_info_init(void)
334 {
335 	unsigned long size = 0;
336 #ifdef CONFIG_KALLSYMS
337 	unsigned long ofs;
338 
339 	kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
340 #endif
341 	schedule_mfi.func = schedule;
342 	schedule_mfi.func_size = size;
343 
344 	get_frame_info(&schedule_mfi);
345 
346 	/*
347 	 * Without schedule() frame info, result given by
348 	 * thread_saved_pc() and get_wchan() are not reliable.
349 	 */
350 	if (schedule_mfi.pc_offset < 0)
351 		printk("Can't analyze schedule() prologue at %p\n", schedule);
352 
353 	return 0;
354 }
355 
356 arch_initcall(frame_info_init);
357 
358 /*
359  * Return saved PC of a blocked thread.
360  */
361 unsigned long thread_saved_pc(struct task_struct *tsk)
362 {
363 	struct thread_struct *t = &tsk->thread;
364 
365 	/* New born processes are a special case */
366 	if (t->reg31 == (unsigned long) ret_from_fork)
367 		return t->reg31;
368 	if (schedule_mfi.pc_offset < 0)
369 		return 0;
370 	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
371 }
372 
373 
374 #ifdef CONFIG_KALLSYMS
375 /* generic stack unwinding function */
376 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
377 					      unsigned long *sp,
378 					      unsigned long pc,
379 					      unsigned long *ra)
380 {
381 	struct mips_frame_info info;
382 	unsigned long size, ofs;
383 	int leaf;
384 	extern void ret_from_irq(void);
385 	extern void ret_from_exception(void);
386 
387 	if (!stack_page)
388 		return 0;
389 
390 	/*
391 	 * If we reached the bottom of interrupt context,
392 	 * return saved pc in pt_regs.
393 	 */
394 	if (pc == (unsigned long)ret_from_irq ||
395 	    pc == (unsigned long)ret_from_exception) {
396 		struct pt_regs *regs;
397 		if (*sp >= stack_page &&
398 		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
399 			regs = (struct pt_regs *)*sp;
400 			pc = regs->cp0_epc;
401 			if (__kernel_text_address(pc)) {
402 				*sp = regs->regs[29];
403 				*ra = regs->regs[31];
404 				return pc;
405 			}
406 		}
407 		return 0;
408 	}
409 	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
410 		return 0;
411 	/*
412 	 * Return ra if an exception occurred at the first instruction
413 	 */
414 	if (unlikely(ofs == 0)) {
415 		pc = *ra;
416 		*ra = 0;
417 		return pc;
418 	}
419 
420 	info.func = (void *)(pc - ofs);
421 	info.func_size = ofs;	/* analyze from start to ofs */
422 	leaf = get_frame_info(&info);
423 	if (leaf < 0)
424 		return 0;
425 
426 	if (*sp < stack_page ||
427 	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
428 		return 0;
429 
430 	if (leaf)
431 		/*
432 		 * For some extreme cases, get_frame_info() can
433 		 * consider wrongly a nested function as a leaf
434 		 * one. In that cases avoid to return always the
435 		 * same value.
436 		 */
437 		pc = pc != *ra ? *ra : 0;
438 	else
439 		pc = ((unsigned long *)(*sp))[info.pc_offset];
440 
441 	*sp += info.frame_size;
442 	*ra = 0;
443 	return __kernel_text_address(pc) ? pc : 0;
444 }
445 EXPORT_SYMBOL(unwind_stack_by_address);
446 
447 /* used by show_backtrace() */
448 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
449 			   unsigned long pc, unsigned long *ra)
450 {
451 	unsigned long stack_page = (unsigned long)task_stack_page(task);
452 	return unwind_stack_by_address(stack_page, sp, pc, ra);
453 }
454 #endif
455 
456 /*
457  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
458  */
459 unsigned long get_wchan(struct task_struct *task)
460 {
461 	unsigned long pc = 0;
462 #ifdef CONFIG_KALLSYMS
463 	unsigned long sp;
464 	unsigned long ra = 0;
465 #endif
466 
467 	if (!task || task == current || task->state == TASK_RUNNING)
468 		goto out;
469 	if (!task_stack_page(task))
470 		goto out;
471 
472 	pc = thread_saved_pc(task);
473 
474 #ifdef CONFIG_KALLSYMS
475 	sp = task->thread.reg29 + schedule_mfi.frame_size;
476 
477 	while (in_sched_functions(pc))
478 		pc = unwind_stack(task, &sp, pc, &ra);
479 #endif
480 
481 out:
482 	return pc;
483 }
484 
485 /*
486  * Don't forget that the stack pointer must be aligned on a 8 bytes
487  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
488  */
489 unsigned long arch_align_stack(unsigned long sp)
490 {
491 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
492 		sp -= get_random_int() & ~PAGE_MASK;
493 
494 	return sp & ALMASK;
495 }
496