xref: /openbmc/linux/arch/mips/kernel/process.c (revision d0b73b48) 
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 			play_dead();
77 #endif
78 		rcu_idle_exit();
79 		tick_nohz_idle_exit();
80 		schedule_preempt_disabled();
81 	}
82 }
83 
84 asmlinkage void ret_from_fork(void);
85 asmlinkage void ret_from_kernel_thread(void);
86 
87 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
88 {
89 	unsigned long status;
90 
91 	/* New thread loses kernel privileges. */
92 	status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
93 #ifdef CONFIG_64BIT
94 	status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
95 #endif
96 	status |= KU_USER;
97 	regs->cp0_status = status;
98 	clear_used_math();
99 	clear_fpu_owner();
100 	if (cpu_has_dsp)
101 		__init_dsp();
102 	regs->cp0_epc = pc;
103 	regs->regs[29] = sp;
104 }
105 
106 void exit_thread(void)
107 {
108 }
109 
110 void flush_thread(void)
111 {
112 }
113 
114 int copy_thread(unsigned long clone_flags, unsigned long usp,
115 	unsigned long arg, struct task_struct *p)
116 {
117 	struct thread_info *ti = task_thread_info(p);
118 	struct pt_regs *childregs, *regs = current_pt_regs();
119 	unsigned long childksp;
120 	p->set_child_tid = p->clear_child_tid = NULL;
121 
122 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
123 
124 	preempt_disable();
125 
126 	if (is_fpu_owner())
127 		save_fp(p);
128 
129 	if (cpu_has_dsp)
130 		save_dsp(p);
131 
132 	preempt_enable();
133 
134 	/* set up new TSS. */
135 	childregs = (struct pt_regs *) childksp - 1;
136 	/*  Put the stack after the struct pt_regs.  */
137 	childksp = (unsigned long) childregs;
138 	p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
139 	if (unlikely(p->flags & PF_KTHREAD)) {
140 		unsigned long status = p->thread.cp0_status;
141 		memset(childregs, 0, sizeof(struct pt_regs));
142 		ti->addr_limit = KERNEL_DS;
143 		p->thread.reg16 = usp; /* fn */
144 		p->thread.reg17 = arg;
145 		p->thread.reg29 = childksp;
146 		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
147 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
148 		status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
149 			 ((status & (ST0_KUC | ST0_IEC)) << 2);
150 #else
151 		status |= ST0_EXL;
152 #endif
153 		childregs->cp0_status = status;
154 		return 0;
155 	}
156 	*childregs = *regs;
157 	childregs->regs[7] = 0;	/* Clear error flag */
158 	childregs->regs[2] = 0;	/* Child gets zero as return value */
159 	childregs->regs[29] = usp;
160 	ti->addr_limit = USER_DS;
161 
162 	p->thread.reg29 = (unsigned long) childregs;
163 	p->thread.reg31 = (unsigned long) ret_from_fork;
164 
165 	/*
166 	 * New tasks lose permission to use the fpu. This accelerates context
167 	 * switching for most programs since they don't use the fpu.
168 	 */
169 	childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
170 
171 #ifdef CONFIG_MIPS_MT_SMTC
172 	/*
173 	 * SMTC restores TCStatus after Status, and the CU bits
174 	 * are aliased there.
175 	 */
176 	childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
177 #endif
178 	clear_tsk_thread_flag(p, TIF_USEDFPU);
179 
180 #ifdef CONFIG_MIPS_MT_FPAFF
181 	clear_tsk_thread_flag(p, TIF_FPUBOUND);
182 #endif /* CONFIG_MIPS_MT_FPAFF */
183 
184 	if (clone_flags & CLONE_SETTLS)
185 		ti->tp_value = regs->regs[7];
186 
187 	return 0;
188 }
189 
190 /* Fill in the fpu structure for a core dump.. */
191 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
192 {
193 	memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
194 
195 	return 1;
196 }
197 
198 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
199 {
200 	int i;
201 
202 	for (i = 0; i < EF_R0; i++)
203 		gp[i] = 0;
204 	gp[EF_R0] = 0;
205 	for (i = 1; i <= 31; i++)
206 		gp[EF_R0 + i] = regs->regs[i];
207 	gp[EF_R26] = 0;
208 	gp[EF_R27] = 0;
209 	gp[EF_LO] = regs->lo;
210 	gp[EF_HI] = regs->hi;
211 	gp[EF_CP0_EPC] = regs->cp0_epc;
212 	gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
213 	gp[EF_CP0_STATUS] = regs->cp0_status;
214 	gp[EF_CP0_CAUSE] = regs->cp0_cause;
215 #ifdef EF_UNUSED0
216 	gp[EF_UNUSED0] = 0;
217 #endif
218 }
219 
220 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
221 {
222 	elf_dump_regs(*regs, task_pt_regs(tsk));
223 	return 1;
224 }
225 
226 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
227 {
228 	memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
229 
230 	return 1;
231 }
232 
233 /*
234  *
235  */
236 struct mips_frame_info {
237 	void		*func;
238 	unsigned long	func_size;
239 	int		frame_size;
240 	int		pc_offset;
241 };
242 
243 static inline int is_ra_save_ins(union mips_instruction *ip)
244 {
245 	/* sw / sd $ra, offset($sp) */
246 	return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
247 		ip->i_format.rs == 29 &&
248 		ip->i_format.rt == 31;
249 }
250 
251 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
252 {
253 	if (ip->j_format.opcode == jal_op)
254 		return 1;
255 	if (ip->r_format.opcode != spec_op)
256 		return 0;
257 	return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
258 }
259 
260 static inline int is_sp_move_ins(union mips_instruction *ip)
261 {
262 	/* addiu/daddiu sp,sp,-imm */
263 	if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
264 		return 0;
265 	if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
266 		return 1;
267 	return 0;
268 }
269 
270 static int get_frame_info(struct mips_frame_info *info)
271 {
272 	union mips_instruction *ip = info->func;
273 	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
274 	unsigned i;
275 
276 	info->pc_offset = -1;
277 	info->frame_size = 0;
278 
279 	if (!ip)
280 		goto err;
281 
282 	if (max_insns == 0)
283 		max_insns = 128U;	/* unknown function size */
284 	max_insns = min(128U, max_insns);
285 
286 	for (i = 0; i < max_insns; i++, ip++) {
287 
288 		if (is_jal_jalr_jr_ins(ip))
289 			break;
290 		if (!info->frame_size) {
291 			if (is_sp_move_ins(ip))
292 				info->frame_size = - ip->i_format.simmediate;
293 			continue;
294 		}
295 		if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
296 			info->pc_offset =
297 				ip->i_format.simmediate / sizeof(long);
298 			break;
299 		}
300 	}
301 	if (info->frame_size && info->pc_offset >= 0) /* nested */
302 		return 0;
303 	if (info->pc_offset < 0) /* leaf */
304 		return 1;
305 	/* prologue seems boggus... */
306 err:
307 	return -1;
308 }
309 
310 static struct mips_frame_info schedule_mfi __read_mostly;
311 
312 static int __init frame_info_init(void)
313 {
314 	unsigned long size = 0;
315 #ifdef CONFIG_KALLSYMS
316 	unsigned long ofs;
317 
318 	kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
319 #endif
320 	schedule_mfi.func = schedule;
321 	schedule_mfi.func_size = size;
322 
323 	get_frame_info(&schedule_mfi);
324 
325 	/*
326 	 * Without schedule() frame info, result given by
327 	 * thread_saved_pc() and get_wchan() are not reliable.
328 	 */
329 	if (schedule_mfi.pc_offset < 0)
330 		printk("Can't analyze schedule() prologue at %p\n", schedule);
331 
332 	return 0;
333 }
334 
335 arch_initcall(frame_info_init);
336 
337 /*
338  * Return saved PC of a blocked thread.
339  */
340 unsigned long thread_saved_pc(struct task_struct *tsk)
341 {
342 	struct thread_struct *t = &tsk->thread;
343 
344 	/* New born processes are a special case */
345 	if (t->reg31 == (unsigned long) ret_from_fork)
346 		return t->reg31;
347 	if (schedule_mfi.pc_offset < 0)
348 		return 0;
349 	return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
350 }
351 
352 
353 #ifdef CONFIG_KALLSYMS
354 /* generic stack unwinding function */
355 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
356 					      unsigned long *sp,
357 					      unsigned long pc,
358 					      unsigned long *ra)
359 {
360 	struct mips_frame_info info;
361 	unsigned long size, ofs;
362 	int leaf;
363 	extern void ret_from_irq(void);
364 	extern void ret_from_exception(void);
365 
366 	if (!stack_page)
367 		return 0;
368 
369 	/*
370 	 * If we reached the bottom of interrupt context,
371 	 * return saved pc in pt_regs.
372 	 */
373 	if (pc == (unsigned long)ret_from_irq ||
374 	    pc == (unsigned long)ret_from_exception) {
375 		struct pt_regs *regs;
376 		if (*sp >= stack_page &&
377 		    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
378 			regs = (struct pt_regs *)*sp;
379 			pc = regs->cp0_epc;
380 			if (__kernel_text_address(pc)) {
381 				*sp = regs->regs[29];
382 				*ra = regs->regs[31];
383 				return pc;
384 			}
385 		}
386 		return 0;
387 	}
388 	if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
389 		return 0;
390 	/*
391 	 * Return ra if an exception occurred at the first instruction
392 	 */
393 	if (unlikely(ofs == 0)) {
394 		pc = *ra;
395 		*ra = 0;
396 		return pc;
397 	}
398 
399 	info.func = (void *)(pc - ofs);
400 	info.func_size = ofs;	/* analyze from start to ofs */
401 	leaf = get_frame_info(&info);
402 	if (leaf < 0)
403 		return 0;
404 
405 	if (*sp < stack_page ||
406 	    *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
407 		return 0;
408 
409 	if (leaf)
410 		/*
411 		 * For some extreme cases, get_frame_info() can
412 		 * consider wrongly a nested function as a leaf
413 		 * one. In that cases avoid to return always the
414 		 * same value.
415 		 */
416 		pc = pc != *ra ? *ra : 0;
417 	else
418 		pc = ((unsigned long *)(*sp))[info.pc_offset];
419 
420 	*sp += info.frame_size;
421 	*ra = 0;
422 	return __kernel_text_address(pc) ? pc : 0;
423 }
424 EXPORT_SYMBOL(unwind_stack_by_address);
425 
426 /* used by show_backtrace() */
427 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
428 			   unsigned long pc, unsigned long *ra)
429 {
430 	unsigned long stack_page = (unsigned long)task_stack_page(task);
431 	return unwind_stack_by_address(stack_page, sp, pc, ra);
432 }
433 #endif
434 
435 /*
436  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
437  */
438 unsigned long get_wchan(struct task_struct *task)
439 {
440 	unsigned long pc = 0;
441 #ifdef CONFIG_KALLSYMS
442 	unsigned long sp;
443 	unsigned long ra = 0;
444 #endif
445 
446 	if (!task || task == current || task->state == TASK_RUNNING)
447 		goto out;
448 	if (!task_stack_page(task))
449 		goto out;
450 
451 	pc = thread_saved_pc(task);
452 
453 #ifdef CONFIG_KALLSYMS
454 	sp = task->thread.reg29 + schedule_mfi.frame_size;
455 
456 	while (in_sched_functions(pc))
457 		pc = unwind_stack(task, &sp, pc, &ra);
458 #endif
459 
460 out:
461 	return pc;
462 }
463 
464 /*
465  * Don't forget that the stack pointer must be aligned on a 8 bytes
466  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
467  */
468 unsigned long arch_align_stack(unsigned long sp)
469 {
470 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
471 		sp -= get_random_int() & ~PAGE_MASK;
472 
473 	return sp & ALMASK;
474 }
475