c11e5ca2a434a4cef23b80aa39a58f974ae97be2
[linux-3.10.git] / arch / mips / kernel / process.c
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/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_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                 tick_nohz_idle_exit();
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 }